oEPA
            United States
            Environmental Protection
            Agency
             Office of Solid Waste
             and Emergency
             Response
Publication 9345.1-07
PB92-963377
EPA 540-R-92-026
November 1992
            Superfund
Hazard Ranking System
Guidance Manual

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                                 EPA540-R-92-026
                           OSWER Directive 9345.1-07
                                   November 1992
The Hazard Ranking System
       Guidance Manual
          Interim Final
       Hazardous Site Evaluation Division
   Office of Solid Waste and Emergency Response
      U.S. Environmental Protection Agency
           Washington, DC 20460

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                                         NOTICE

The  procedures  set forth  in this  document are  intended as  guidance to  employees  of the U.S.
Environmental Protection Agency (EPA), States, and other government agencies. EPA officials may
decide to follow the guidance provided in this directive, or to act at variance with it, based on analysis of
specific site circumstances. EPA also reserves the right to modify this guidance at any time without public
notice.

These guidelines do not constitute EPA rulemaking and cannot be relied upon to create rights enforceable
by any party In litigation with the United States.

Mention of any company or product names in this document should not be considered as an endorsement
by EPA.

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                                       CONTENTS

                                                                                   Page

CHAPTER 1    INTRODUCTION

Section 1.1 Introduction to the MRS	1

Section 1.2 Overview of the Superfund Process	2

       Current Superfund Process	2
       Superfund Accelerated Cleanup Model	4

Section 1.3 Organization of the HRSGM  	5

Section 1.4 Related Site Assessment Guidance Materials	6

CHAPTER 2   POLICY AND STATUTORY ISSUES

Section 2.1 Source and Site Definition  	9

       Multiple Sources	9
       Federal Facilities  	10

Section 2.2 Scoring All Pathways and Threats	11

Section 2.3 Evaluation of Sites with Waste Removals  	11

       Requirements for Considering Removal Actions	12
       Determining the Cutoff Date	12
       Scoring Considerations When a Qualifying Removal Has Occurred  	16

Section 2.4 CERCLA Pollutants or Contaminants	18

Section 2.5 Statutory and Policy Exclusions	18

       CERCLA Petroleum Exclusion 	19
       Radioactive Materials	19
       RCRA Site Policy	20

CHAPTER 3   THE HRS SCORING PROCESS

Section 3.1 General Approach to HRS Scoring	21

       Step 1: Assemble and Review All Available Site  Information 	22
       Step 2: Identify and Characterize Sources 	22
       Step 3: Identify and Characterize Significant Pathways	23
       Step 4: Evaluate Targets for Significant Pathways  	24
       Step 5: Collect Additional Information, If Necessary  	26
       Step 6: Check Validity of Factor Values 	26
       Step 7: Assemble and Submit Complete HRS Package  	27
       Step 8: Respond to Reviews	27



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                                  CONTENTS (continued)

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Section 3.2 The MRS Scoring Package  	27

       The Documentation Record  	27
       References	28
       Other Items  in the MRS Scoring Package	29

Section 3.3 The Package Review Process	30

Section 3.4 MRS Scoring Strategy	31

       Scoring Effort	31
       Implications  of MRS Equations for Site Scoring	32
       Pathway Considerations  	35

CHAPTER 4   SOURCES

Section 4.1 Characterization of Sources and Areas of
   Observed Contamination 	41

       Definitions	41
       Evaluating Sources	43
       Evaluating Sites with No Identified Sources  	46
       Characterizing Unique Sources	46
       Tips and Reminders  	48

Section 4.2 Overview of Sites with Multiple Sources 	49

       Definitions	49
       Scoring Multiple Source Sites	49
       Aggregating  Sources	51
       Tips and Reminders  	54

CHAPTER 5   OBSERVED RELEASE

Section 5.1 Establishing an Observed Release and Observed Contamination	55

       Definitions	55
       Establishing  an Observed Release by Chemical Analysis	58
       Using Published Data for Background Levels 	62
       Using Qualified Data	63
       Establishing  an Observed Release by Direct Observation	63
       Tips and Reminders  	65

Section 5.2 Selecting Appropriate Background Samples	67

       Definitions	67
       Data Requirements	68
       Data Evaluation Guidelines	69
       Tips and Reminders  	   78


Contents                                     IV

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                                  CONTENTS (continued)

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Section 5.3 Transformation Products 	79

       Definitions	79
       General Requirements  	79
       Establishing an Observed Release (or Observed Contamination) for
       Transformation Products	80

CHAPTER 6   HAZARDOUS WASTE QUANTITY

Section 6.1 Overview of Hazardous Waste Quantity for the Three Migration Pathways	83

       Definitions	86
       Beginning the Hazardous Waste Quantity Evaluation	86
       Locating Hazardous Waste Quantity Information  	88
       Tips and Reminders  	89

Section 6.2 Tier A — Hazardous Constituent Quantity	91

       Definitions	91
       A1.  Locating Data	91
       A2.  Using Concentration Data	93
       A3.  Evaluating RCRA Hazardous Wastes	93
       A4.  Calculating Hazardous Constituent Quantity	96
       Tips and Reminders  	97

Section 6.3 Tier B — Hazardous Wastestrearn Quantity	99

       Definitions	99
       B1.  Locating Data	99
       B2.  Evaluating RCRA Hazardous Waste	101
       B3.  Extrapolating Data  	101
       B4.  Calculating Hazardous Wastestrearn Quantity  	102
       Tips and Reminders  	102

Section 6.4 Tier C — Volume  	105

       C1.  Locating Data	105
       C2.  Calculating Volume  	105
       Tips and Reminders  	107

Section 6.5 Tier D — Area	109

       D1.  Locating Data	109
       D2.  Calculating Area	109

Section 6.6 Hazardous Waste  Quantity Calculation  	111

       Selecting Source Hazardous Waste Quantity Values  	111
       Calculating Pathway Hazardous Waste Quantity Factor Value  	111
       Applying the Minimum Factor Value	111
                                                                                    Contents

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                                  CONTENTS (continued)

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CHAPTER 7   GROUND WATER PATHWAY

Section 7.1     Determining Aguifer Boundaries and Number of Aguifers	115

       Definitions	116
       Identifying and Evaluating Aquifers	117
       Identifying Aquifer Discontinuities	125
       Identifying Aquifer Interconnections  	127
       Tips and Reminders  	134

Section 7.2 Treatment of Karst	137

       Definitions	138
       Identifying Karst 	138
       Scoring Differences for Karst Aquifers  	140
       Tips and Reminders  	146

Section 7.3 Containment Factor	147

       Definitions	147
       Scoring the Ground Water Containment Factor	148
       Tips and Reminders  	151

Section 7.4 Actual Contamination 	153

       Definitions	153
       Establishing Actual Contamination  	154
       Determining Level of Contamination	156
       Scoring Sites with Actual Contamination	159
       Tips and Reminders  	162

Section 7.5 Population and  Nearest Well Factors	163

       Definitions	163
       Evaluating the Ground Water Population Factor	165
       Evaluating the Nearest Well Factor	170
       Evaluating Ground Water Pathway When Multiple Sources Are Present	172
       Tips and Reminders  	175

Section 7.6 Blended Water Supplies 	177

       Definitions	177
       Scoring the Population Factor for Blended Water Supplies	178
       Scoring Interconnected Blended  Systems	180
       Tips and Reminders  	185

Section 7.7 Standby Wells  	187

       Definitions	187
       Scoring the Nearest Well Using Standby Wells	188
       Scoring the Population Using Standby Wells	189
       Tips and Reminders  	192
Contents                                      VI

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                                  CONTENTS (continued)

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Section 7.8 Resources and Wellhead Protection Area 	193

       Definitions	193
       Scoring the Resources Factor	194
       Scoring the Wellhead Protection Area Factor	194
       Tips and Reminders  	196

Section 7.9 Scoring Sites with Multiple Aguifers  	197

       Definitions	197
       Scoring Multiple Aquifer Systems	197
       Examples of Multiple Aquifer Systems  	198
       Tips and Reminders  	202

CHAPTER 8   SURFACE WATER PATHWAY

Section 8.1 Hazardous Substance Migration Path  	203

       Definitions	203
       Delineating the Overland Segment	204
       Scoring the Distance to Surface Water Factor  	206
       Scoring the Flood Frequency Factor	208
       Evaluating the Target Distance Limit for Non-tidally
          Influenced Water Bodies	208
       Evaluating the Target Distance Limit for Tidally
          Influenced Water Bodies	216
       Tips and Reminders  	218

Section 8.2 Delineation of Watersheds and Drainage Areas  	219

       Definitions	219
       Delineating Watersheds 	220
       Determining Drainage Area	221
       Tips and Reminders  	227

Section 8.3 Characterization of Surface Water Bodies	229

       Definitions	229
       Determining Breakpoints between  Surface Water Categories	230
       Assigning Surface Water Dilution Weights  	231
       Estimating Flow 	233
       Evaluating Targets in Multiple Water Body Categories  	239
       Determining Salinity Category of Water Body	239
       Tips and Reminders  	241

Section 8.4 Surface Water Containment Factor	243

       Definitions	243
       Scoring Surface Water Containment for Overland Flow  	245
       Scoring Surface Water Containment for Flood  	245
       Tips and Reminders  	248
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                                   CONTENTS (continued)

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Section 8.5 Overview of Actual Contamination for All Three Threats 	249

       Definitions	249

Section 8.6 Efficiency of Scoring the Drinking Water Threat	253

       Definitions	253
       Estimating Actual Contamination  	253
       Estimating Potential Contamination  	254

Section 8.7 Actual Contamination In the Drinking Water Threat  	259

       Definitions	259
       Establishing Actual Contamination for a Drinking Water Intake	260
       Determining Level of Contamination	261
       Scoring Intakes Subject to Actual Contamination  	263
       Tips and Reminders  	263

Section 8.8 Population and Nearest Intake Factors  	265

       Definitions	265
       Evaluating the Drinking Water Population Factor  	266
       Evaluating the Nearest Intake Factor 	271
       Tips and Reminders  	271

Section 8.9 Blended Water Supplies  	273

       Definitions	273
       Scoring the Population Factor for Blended Water Supplies	274
       Scoring Multiple Blended Systems 	276
       Tips and Reminders  	280

Section 8.10 Standby Intakes	281

       Definitions	281
       Scoring the Nearest Intake Factor Using Standby Intakes	282
       Scoring the Population Factor Using Standby Intakes	283
       Tips and Reminders  	288

Section 8.11 Resources 	289

       Definitions	289
       Scoring the Resources Factor	289
       Tips and Reminders  	291

Section 8.12 Actual Human Food Chain Contamination	293

       Definitions	293
       Documenting Presence of a Fishery	294
       Establishing Actual Contamination of a Fishery	295
       Determining the Level of Actual Contamination 	298
       Scoring Sites with Actual Contamination	300
Contents                                      Vlll

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                                  CONTENTS (continued)

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       Tips and Reminders  	304

Section 8.13 Human Food Chain Production  	305

       Definitions	305
       Estimating the Human Food Chain Population Factor	306
       Determining Production Using Site-specific Data 	309
       Estimating Production Using Surrogate Data	315
       Estimating Production without Actual or Surrogate Data	315
       Tips and Reminders  	316

Section 8.14 Sensitive Environments  	317

       Definitions	317
       Sensitive Environments Eligible to Be Evaluated in the Surface Water Pathway	318
       Calculating the Sensitive Environments Factor Value	318
       Tips and Reminders  	324

Section 8.15 Level I and Level II Concentrations for Listed Sensitive Environments	325

       Definitions	325
       Determining Level of Contamination	326
       Tips and Reminders  	329

Section 8.16 Wetlands	331

       Definitions	331
       Identifying and Delineating Wetlands   	331
       Determining Wetland Size (Length or Perimeter) 	332
       Establishing Actual and Potential Contamination	338
       Determining Wetland Length (or Perimeter) Subject to Actual
           and Potential Contamination	338
       Tips and Reminders  	342

CHAPTER 9   SOIL EXPOSURE PATHWAY

Section 9.1 Areas of Observed Contamination	343

       Definitions	343
       Establishing Areas of Observed Contamination	344
       Tips and Reminders  	350

Section 9.2 Waste Characteristics for the Soil Exposure Pathway 	351

       Definitions	351
       Evaluating Toxicity	352
       Evaluating Hazardous Waste Quantity 	352
       Evaluating Tier A — Hazardous Constituent Quantity	353
       Evaluating Tier B — Hazardous Wastestream Quantity  	353
       Evaluating Tier C — Volume	355
       Evaluating Tier D — Area	356


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       Calculating Hazardous Waste Quantity Factor Value  	356
       Tips and Reminders  	357

Section 9.3 Resident Population Threat 	359

       Definitions	360
       Identifying Resident Individuals and Workers 	361
       Identifying Resources and Terrestrial Sensitive Environments  	362
       Level I and Level II Concentrations	362
       Tips and Reminders  	362

Section 9.4 Resident Individual and Resident Population	363

       Definitions	363
       Evaluating Level of Contamination	364
       Evaluating Resident Individual 	365
       Evaluating Resident Population  	366
       Tips and Reminders  	369

Section 9.5 Workers and Resources 	371

       Definitions	371
       Evaluating the Workers Factor	372
       Scoring the Resources Factor	373
       Tips and Reminders  	374

Section 9.6 Terrestrial Sensitive Environments  	375

       Definitions	375
       Scoring Terrestrial Sensitive Environments	376
       Tips and Reminders  	381

Section 9.7 Estimation of Nearby Population Threat Scores	383

       Definitions	383
       Estimating Nearby Population Threat Score 	383

Section 9.8 Evaluation of Nearby Population Threat  	389

       Definitions	389
       Scoring the Likelihood of Exposure Factor Category	390
       Scoring Waste Characteristics Factor Category  	390
       Scoring Targets Factor Category  	390
       Calculating the Nearby Population Threat Score	394
       Tips and Reminders  	396

CHAPTER 10  AIR PATHWAY

Section 10.1 Observed Release 	397

       Definitions	397

Contents                                       X

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                                  CONTENTS (continued)
       Establishing an Observed Release by Direct Observation	  398
       Establishing an Observed Release by Chemical Analysis	  399
       Tips and Reminders	  401

Section 10.2   Potential to Release	  403

       Definitions	  404
       Distinguishing between Gaseous and Particulate Hazardous Substances	404
       Combining Sources Before Calculating Potential to Release	  404
       Evaluating Gas and Particulate Containment	  406

Section 10.3   Actual Contamination and Nearest Individual  	  411

       Definitions	  411
       Determining Level of Actual Contamination 	  412
       Evaluating Sites with Actual Contamination 	  414
       Evaluating Nearest Individual Factor	  416
       Tips and Reminders  	  420

Section 10.4   Resources	  421

       Definitions	  421
       Scoring the Resources Factor	  421
       Tips and Reminders  	  422

Section 10.5   Evaluation of Sensitive Environments 	  423

       Definitions	  423
       Calculating the Sensitive Environments Factor Value	  423
       Tips and Reminders  	  431

APPENDIX A  SENSITIVE ENVIRONMENTS

Section A.1    Pathway-specific Eligibility Requirements for Sensitive Environments	A-1

       Air Pathway  	  A-1
       Soil Exposure Pathway	  A-1
       Surface Water Pathway 	  A-1

Section A.2   Definitions of Sensitive Environments Including Wetlands  	  A-3

Section A.3   Process for Identifying and Delineating Sensitive Environments	  A-25

       Sensitive Environments Likely to Be Delineated  on USGS Topographic Maps	  A-25
       Sensitive Environments Likely to Be Delineated  on Specialized Maps or
           in Special Documents	  A-25
       Sensitive Environments That Require Professional Judgment and/or Specific
       Expertise to Identify and Delineate	  A-26

Section A.4   Sources of Information for Identifying Sensitive Environments	  A-33
                                            XI                                       Contents

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                                       HIGHLIGHTS

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CHAPTER 1    INTRODUCTION

Highlight 1 -1:      The Superfund Process	 3

Highlight 1-2:      Icons for HRS Pathways, Threats, and Factor Categories	6

Highlight 1-3:      Site Assessment Guidance Documents and Scoring Tools	8

CHAPTER 2    POLICY AND STATUTORY ISSUES

Highlight 2-1:      Flowchart for Identification of the Cutoff Date	 14

Highlight 2-2:      Examples of Determining Cutoff Date 	 15

CHAPTER 3    THE HRS SCORING PROCESS

Highlight 3-1:      The PREscore Software Program	 21

Highlight 3-2:      The Superfund Chemical Database Matrix	 29

Highlight 3-3:      Combinations of Pathway Scores That Yield Site Score of 28.50	33

Highlight 3-4:      Additional Score Required to Yield Site Score of 28.50	34

Highlight 3-5:      Minimum Targets Factor Value Required to Yield Pathway Score of 57	36

Highlight 3-6:      Distance and Dilution Weights under Potential Contamination	37

Highlight 3-7:      Population Required to Yield Pathway Score of 57	 37

Highlight 3-8:      Drinking Water Threat Scores under Potential Contamination	39

CHAPTER 4    SOURCES

Highlight 4-1:      Commonly Confused Source Types	 44

Highlight 4-2:      When to Consider Natural Ponds as Sources	 47

Highlight 4-3:      HRS Factors Summed for Multiple Sources	 50

Highlight 4-4:      HRS Factors Selected from Individual
                 Source Factor Values	 50

Highlight 4-5:      HRS Factors Affected by Minimum Size  Requirements 	50

Highlight 4-6:      Checklist for Source Aggregation	 51

Highlight 4-7:      When to Aggregate Overlapping Sources 	 52



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Highlight 4-8:      When to Aggregate Contaminated Soil with Other Sources	53

CHAPTER 5   OBSERVED RELEASES

Highlight 5-1:      Flowchart for Establishing an Observed Release
                  or Observed Contamination	 56

Highlight 5-2:      Flowchart for Determining Significance above Background	60

Highlight 5-3:      Examples for Deciding Whether Significance above
                  Background Is Established	 61

Highlight 5-4:      Definitions and Applications of Common Data Qualifiers	64

Highlight 5-5:      Illustration of Appropriate Background Samples:
                  Ground Water Pathway — Single Aquifer	 71

Highlight 5-6:      Illustration of Appropriate Background Samples:
                  Ground Water Pathway — Multiple Aquifers	 72

Highlight 5-7:      Illustration of Appropriate Background Samples:
                  Ground Water Pathway— Interconnected Aquifers	 73

Highlight 5-8:      Illustration of Appropriate Background Samples:
                  Surface Water Pathway — Streams and Rivers	 75

Highlight 5-9:      Typical Degradation Products	 80

CHAPTER 6   HAZARDOUS WASTE QUANTITY

Highlight 6-1:      Flowchart for Evaluating Hazardous Waste Quantity	84

Highlight 6-2:      Data Availability by Source Type	 87

Highlight 6-3:      Flowchart for Evaluating Tier A  	 92

Highlight 6-4:      Scoring Examples for Tier A  	 94

Highlight 6-5:      Flowchart for Evaluating RCRA Hazardous Wastes under Tier A	97

Highlight 6-6:      Flowchart for Evaluating Tier B  	 100

Highlight 6-7:      Flowchart for Evaluating Tier C  	 106

Highlight 6-8:      Flowchart for Evaluating Tier D  	 110

Highlight 6-9:      Calculation of Source Hazardous Waste Quantity Value	 112

Highlight 6-10:     Calculation of Pathway Hazardous Waste Quantity Factor Value	113
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CHAPTER 7

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GROUND WATER PATHWAY

   Aquifer Data Used for First Level of Investigation	  118

   Aquifer Data Used for Second Level of Investigation	  119

   Aquifer Data Used for Third Level of Investigation	  119

   Combining Horizontal Formations  	  121

   Combining Vertical Formations  	  122

   Combining Vertical Formations with Differences
   in Hydraulic Conductivity	  123

   Delineating Aquifer When a Boundary Is Continuous
   throughout 2-Mile Distance	  124

   Delineating Aquifer When Boundary Partially Transects Aquifer	  126

   Horizontal Aquifers Separated by Formation of Similar
   Hydraulic Conductivity	  128

   Using Well Logs to Assess Aquifer Interconnection	  129

   Using Contaminant Migration to Assess Aquifer Interconnection	131

   Using Pumping Test Data to Assess Aquifer Interconnection	  132

   Using Numerous Man-made Conduits to Assess Aquifer
   Interconnection  	  133

   Bodies  of Salt Water as Aquifer Discontinuities	  136

   Defining Boundaries for a Karst Aquifer	  139

   HRS Factors Given Special Consideration for Karst Aquifers	  141

   Scoring Considerations for Karst Aquifers: Depth to Aquifer Factor	142

   Scoring Considerations for Karst Aquifers: Travel Time Factor	  143

   Scoring Considerations for Karst Aquifers: Mobility Factor	  144

   Scoring Considerations for Karst Aquifers: Nearest Well Factor	  145

   Scoring Considerations for Karst Aquifers: Population/
   Potential Contamination Factor  	  146

   Data Needs for Evaluating Containment	  149

   Source  Measurements That Meet the Minimum Size Requirement	150
                                             xv
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                 HIGHLIGHTS (continued)

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Comparison of Actual Contamination to Observed Release	 154

Examples of Wells Subject to Level I, Level II, and
Potential Contamination	 155

Data Needs for Level of Contamination  	 156

Flowchart for Determining Level I,  Level II, or Potential
Contamination 	 157

Calculating I and J Indices	 159

Comparison of Scoring Level I, Level II, and
Potential Contamination	 160

Scoring Ground  Water Population  Subject to Level I, Level II,
and Potential Contamination 	 161

Identifying Target and Non-target Residences	 164

Data Needs for Ground Water Population  	 166

Documenting Ground Water Population for an Aquifer	 168

Scoring Example of Ground Water Population Factor	 171

Establishing Target Distance Categories: Method 1	 173

Establishing Target Distance Categories: Method 2	 174

Pumpage and Capacity Data	 178

Data Needs for Evaluating Blended Systems	 179

Scoring Example of Single Blended System with Wells
Outside the Target Distance Limit  	 181

Scoring Example for Two Separate Blended Systems	 182

Scoring Example for Multiple Blended Systems	 184

Data Needs and Sources for Standby Wells	 188

Pumpage and Capacity Data for Standby Wells	 190

Using Pumpage Data for Standby Wells	 190

Evaluating Population Factor Using a Standby Well	 191

Checklist for Resources Factor	 195

Information Sources for Resource  Use	 195
Highlights
                                             XVI

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CHAPTER 8

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SURFACE WATER PATHWAY

    Hazardous Substance Migration Path	  205

    Overland Segment for Contaminated Soils  	  205

    Characterization of the Overland Segment for
    Storm Sewers and Covered Drains 	  206

    Eligible Surface Waters	  207

    Probable Point of Entry for Wetlands and Intermittent Streams	208

    Probable Point of Entry and Target Distance Limit for
    Sites with More Than One Overland Segment	  209

    Determining Target Distance Limit	  210

    Determining Target Distance Limit for Sites with Observed
    Release Beyond 15 Miles	  210

    Determining Target Distance Limit for Sites with
    More Than One Probable Point of Entry into Rivers	212

    Determining Target Distance Limit for Sites with More Than One
    Probable Point of Entry into Lakes	  212

    Determining Target Distance Limit for Sites with Probable
    Points of Entry into Two Branches of a River	  213

    Determining Target Distance Limit for Sites with Probable
    Points of Entry into Two Lakes	  214

    Determining Target Distance Limit When
    the In-water Segment Branches	  215

    Determining the Target Distance Limit for Sites
    Consisting Solely of Contaminated Sediments	  216

    Determining Upstream Target Distance Limit
    forTidally Influenced Rivers	  217

    Defining a Single Watershed with  Multiple
    Probable Points of Entry	  222

    Defining Multiple Watersheds	  223

    Drainage Area Determination	  225

    Drainage Area Restricted by Man-made Structures	226

    Breakpoint between Coastal Tidal Waters and  Ocean	232
                                             XVII
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                                  HIGHLIGHTS (continued)
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Highlight 8-21:      Sources of Flow Data	 233

Highlight 8-22:      Extending Short-term Streamflow Records	 234

Highlight 8-23:      Estimating Target Flow Using Interpolation 	 236

Highlight 8-24:      Scoring Targets in Two Dilution Weight Categories	240

Highlight 8-25:      Source Measurements That Meet the Minimum Size Requirement	246

Highlight 8-26:      Data Needs for Evaluating Source Containment	 247

Highlight 8-27:      Samples and Criteria for Level I and Level II
                  Concentrations by Threat	 251

DRINKING WATER THREAT

Highlight 8-28:      Approximate Drinking Water Threat Scores for Population
                  Subject to Actual Contamination 	 254

Highlight 8-29:      Approximate Drinking Water Threat Scores for Population
                  Subject to Potential Contamination 	 256

Highlight 8-30:      Example of Estimating Drinking Water Threat Score	258

Highlight 8-31:      Benchmarks for the Drinking Water Threat	 262

Highlight 8-32:      Comparison of Scoring Level I, Level II, and Potential Contamination	263

Highlight 8-33:      Data Needs for Drinking  Water Threat Population	 266

Highlight 8-34:      Documenting Drinking Water Threat Population	 269

Highlight 8-35:      Example of Scoring Drinking Water Population Factor	270

Highlight 8-36:      Pumpage and Capacity Data	 274

Highlight 8-37:      Data Needs for Evaluating Blended Systems	 275

Highlight 8-38:      Scoring Example of Single Blended System with Intakes
                  Outside of the Target Distance Limit  	 277

Highlight 8-39:      Scoring Example of Two  Separate Blended Systems	278

Highlight 8-40:      Scoring Example for Multiple Blended Systems	 280

Highlight 8-41:      Pumpage and Capacity Data for Standby Intakes	 284

Highlight 8-42:      Data Needs for Standby  Intakes	 285

Highlight 8-43:      Using Pumpage Data for Standby Intakes 	 285
Highlights
                                            XVIII

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                                  HIGHLIGHTS (continued)
Highlight 8-44:     Evaluating Population Factor Using a Standby Intake	286

Highlight 8-45:     Checklist for the Resources Factor	 290

HUMAN FOOD CHAIN THREAT
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Flowchart for Identifying Contaminated Fisheries	  296

Use of Tissue Samples from Aquatic Organisms 	  297

Samples and Criteria for Level I and Level II
Concentrations in the Human  Food Chain Threat	  299

Benchmarks for the Human Food Chain Threat	  300

Comparison of Scoring Level  I, Level II,
and Potential Contamination  	  301

Identifying Level of Contamination for Fisheries	  302

Values for Human  Food Chain Population Factor
Given Actual Contamination in a Fishery	  307

Values for Human  Food Chain Population Factor
Given Potential Contamination in a Fishery	  308

Sources of Fishery Production Data	  310

Production Data Typically Available from NMFS 	  311

Apportionment of Production Data in a River	  312

Apportionment of Production Data along a Coastline	313

Scoring  Example for Potential Contamination  	  314
ENVIRONMENTAL THREAT
Highlight 8-59:

Highlight 8-60:

Highlight 8-61:

Highlight 8-62:


Highlight 8-63:


Highlight 8-64:
Scoring Example for Sensitive Environments	  319

Scoring Example for Level I and Level 11 Contamination  	322

Determining Length for Wetlands along a River	  333

Determining Length for Wetlands along a Lake, Coastal
Tidal Water, or Ocean  	  334

Determining Length for Wetland for a Watershed with
a River and Lake, or Coastal Tidal Water	  335

Determining Length for Wetland Divided by a Stream	336
                                            XIX
                                                                                     Highlights

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                                   HIGHLIGHTS (continued)
                                                                                       Page
Highlight 8-65:     Determining Perimeter of a Wetland When the Probable
                  Point of Entry Is in the Wetland 	  337

Highlight 8-66:     Delineating Actual Contamination for Wetlands in a River	339

Highlight 8-67:     Delineating Actual Contamination for Wetlands in a Lake,
                  Ocean, and Coastal Tidal Water 	  340

Highlight 8-68:     Delineating Actual Contamination for Wetlands When the
                  Probable Point of Entry Is in the Wetland	  342

CHAPTER 9   SOIL EXPOSURE PATHWAY

Highlight 9-1:      Background Samples for Areas of Observed Contamination  	344

Highlight 9-2:      Delineating Areas of Observed Contamination
                  for Sources Other Than Contaminated Soil 	  345

Highlight 9-3:      Delineating Areas of Observed Contamination for Contaminated
                  Soil   	  346

Highlight 9-4:      Delineating Areas of Observed Contamination
                  Using Composite Samples	  347

Highlight 9-5:      Inferring Contamination between Multiple Areas of
                  Observed Contamination	  348

Highlight 9-6:      Delineating Areas of Observed Contamination When
                  Uncontaminated Soils Are Intermingled	  349

Highlight 9-7:      Comparison of Hazardous Waste Quantity Evaluation
                  in the Migration Pathways and the Soil Exposure Pathway	354

RESIDENT POPULATION THREAT

Highlight 9-8:      Targets in the Resident Population Threat	  359

Highlight 9-9:      Identifying Resident Individuals	  361

Highlight 9-10:     Scoring Example for Resident Population on Adjacent Properties	367

Highlight 9-11:     Scoring Example for Multiple Residences on One Property	368

Highlight 9-12:     Evaluating Workers at a Multiple-building Facility 	  372

Highlight 9-13:     Checklist for the Resources Factor	  373

Highlight 9-14:     Data Sources for the Resources Factor	  373

Highlight 9-15:     EC Values Corresponding to Waste Characteristics Factor Values	379
Highlights
                                             XX

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                                  HIGHLIGHTS (continued)
Highlight 9-16:     Scoring Example for Terrestrial Sensitive Environments 	380

NEARBY POPULATION THREAT

Highlight 9-17:     Approximate Distance-weighted Population Values Based on
                  Local Population Density	  384

Highlight 9-18:     Approximate Nearby Population Threat Scores	  385

Highlight 9-19:     Estimated Area of Contamination  Factor Values 	  387

Highlight 9-20:     Estimated Nearby Population Likelihood of Exposure Factor Values	387

Highlight 9-21:     Examples of Attractiveness/Accessibility Values 	  391

Highlight 9-22:     Establishing Target Distance Categories for Nearby Threat:
                  Method 1  	  393

Highlight 9-23:     Establishing Target Distance Categories for Nearby Threat:
                  Method 2 	  395

CHAPTER 10    AIR PATHWAY

Highlight 10-1:     Selected EPA Guidance on Air Sampling	  400


Highlight 10-2:     Vapor Pressure Ranges For Gaseous and/or Particulate
                  Hazardous Substances	  405


Highlight 10-3:     Vapor Pressures for Selected Hazardous Substances	405

Highlight 10-4:     Selected Containment Descriptions That Are Assigned
                  the Same Gas and Particulate Containment Values	407

Highlight 10-5:     Flowchart for Potential to Release: Particulate Hazardous Substances	409

Highlight 10-6:     Flowchart for Potential to Release: Gaseous Hazardous Substance	410

Highlight 10-7:     Determining Areas of Actual and Potential Contamination
                  with Multiple Sources	  415

Highlight 10-8:     Determining Potential Contamination with Multiple Sources  	417

Highlight 10-9:     Effect of Sample Location on Target Population 	  418

Highlight 10-10:    Illustration of Target Populations Subject to Level I, Level  II,
                  and Potential Contamination  	  419

Highlight 10-11:    Checklist for Resources Factor 	  422

Highlight 10-12:    Data Sources for the Resources Factor	  422
                                             XXI
                                                                                     Highlights

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                                   HIGHLIGHTS (continued)


                                                                                        Page

Highlight 10-13:    Identifying Sensitive Environments in the Air Pathway	425

Highlight 10-14     Determining Actual and Potential Contamination for:
                  sensitive Environments 	 426

Highlight 10-15:    Scoring  Example for Sensitive Environments	 427

APPENDIX A    SENSITIVE ENVIRONMENTS

Highlight A-1:      Eligibility Requirements for Evaluating Terrestrial Sensitive
                  Environments in Surface Water Pathway	 A-2

Highlight A-2:      Key Terms Used in Defining Sensitive Environments	 A-3

Highlight A-3:      Determining HRS Categories for Coastal Barrier	 A-6

Highlight A-4:      HRS Categories for Wild and Scenic Rivers	 A-8

Highlight A-5:      CERCLA Natural Resource Trustees	 A-12

Highlight A-6:      Appropriate Documentation for Migratory Pathways and
                  Feeding Areas Critical for Maintenance of Anadromous
                  Fish Species within Rivers, Lakes, or Coastal Tidal Waters	 A-13

Highlight A-7:      Appropriate Documentation for Spawning Areas Critical
                  for Maintenance of Fish/Shellfish Species within
                  Rivers, Lakes, or Coastal Tidal Waters  	 A-17

Highlight A-8:      Comparison of HRS Wetlands Definition and Wetlands
                  Classification System Used for NWI  Maps	 A-22

Highlight A-9:      Eligibility of Wetland Categories on NWI Maps for HRS Scoring	 A-30

Highlight A-10:     U.S. Geological Survey Earth Science Information Center Offices	 A-43

Highlight A-11:     U.S. National Park Service Regional Offices 	 A-44

Highlight A-12:     U.S. Fish and Wildlife Service Regional Offices	 A-45

Highlight A-13:     U.S. Bureau of Land Management State Offices  	 A-46

Highlight A-14:     U.S. National Forest Service Regions 	 A-47

Highlight A-15:     National Estuarine Research Reserve System	 A-48

Highlight A-16:     Near Coastal Waters Program EPA Regional Contacts	 A-50

Highlight A-17:     EPA Regional Clean Lakes Program Offices	 A-51

Highlight A-18:     Nautical Chart Numbers for Maine Sanctuaries	 A-52
Highlights
                                             XXII

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                                   HIGHLIGHTS (continued)
Highlight A-19:     National Estuary Program Information Sources 	  A-53



Highlight A-20:     EPA Regional Offices  	  A-54



Highlight A-21:     National Park Service Regional Boundaries	  A-55



Highlight A-22:     U.S. Fish and Wildlife Service Regional Boundaries	  A-56



Highlight A-23:     U.S. Forest Service Regional Boundaries	  A-57
                                             XXIII                                       Highlights

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                                   MRS CROSS REFERENCE

MRS Rule                                                                              HRSGM
Section           MRS Rule Section Title                                             Section(s)
1.1             Definitions  	   7.2

2.1.3           Common evaluations 	   4.1

2.2             Characterize sources	   4.1

2.2.1           Identify sources 	   4.1

2.2.2           Identify hazardous substances associated with a source	  4.1
                                                                                        9.1,9.2
2.2.3           Identify hazardous substances available to a pathway	  4.1

2.3             Likelihood of release 	5.1, 5.2, 5.3
                                                                                            7.4
                                                                                       8.5,8.12
                                                                                            9.1
                                                                                      10.1, 10.3

2.4.1.1         Toxicity factor	   9.2

2.4.2           Hazardous waste quantity	   6.1
                                                                                            9.2

2.4.2.1         Source hazardous waste quantity	   6.1

2.4.2.1.1       Hazardous constituent quantity	  6.1, 6.2

2.4.2.1.2       Hazardous wastestream quantity	  6.1, 6.3

2.4.2.1.3       Volume	  6.1, 6.4

2.4.2.1.4       Area	  6.1, 6.5

2.4.2.1.5       Calculation of source hazardous waste quantity value	6.1, 6.6

2.4.2.2         Calculation of hazardous waste quantity factor value	  6.1, 6.6.

2.5             Targets	   7.4
                                                                         8.5,8.7, 8.12, 8.14, 8.15
                                                                                           10.3
2.5.1           Determination of level of actual contamination
               at a sampling location	   7.4
                                                                              8.5,8.7, 8.12, 8.15
                                                                                           10.3

2.5.2           Comparison to benchmarks  	   7.4
                                                                         8.5,8.7, 8.12, 8.14, 8.15
                                                                                           10.3
                                              XXV                              MRS Cross Reference

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                              MRS CROSS REFERENCE (continued)

MRS Rule                                                                                HRSGM
Section        MRS Rule Section Title                                                  Section(s)

3.0            Ground water migration pathway  	   7.9

3.0.1           General considerations	   7.5

3.0.1.1         Ground water target distance limit  	  7.1,7.5

3.0.1.2         Aquifer boundaries	   7.1

3.0.1.2.1        Aquifer interconnections	   7.1

3.0.1.2.2       Aquifer discontinuities  	   7.1

3.0.1.3         Karst aquifer	   7.2

3.1.1           Observed release	5.1, 5.2, 5.3
                                                                                              7.4

3.1.2           Potential to release	   7.9

3.1.2.1         Containment	   7.3

3.1.2.3         Depth to  aquifer	   7.2

3.1.2.4         Travel time	   7.2

3.2.1.2         Mobility	   7.2

3.3            Targets	   7.9

3.3.1           Nearest well	  7.2, 7.4, 7.5, 7.7, 7.9

3.3.2           Population 	   7.5, 7.6, 7.7, 7.9

3.3.2.1         Level of contamination	   7.4

3.3.2.2         Level I concentrations  	  7.2, 7.4

3.3.2.3         Level II concentrations	  7.2, 7.4

3.3.2.4         Potential contamination  	  7.2, 7.9

3.3.3           Resources 	   7.8

3.3.4           Wellhead protection area	   7.8

3.4            Ground water migration score for an aquifer	   7.9

4.0.2           Surface water categories 	   8.1, 8.2, 8.3, 8.16

4.1.1.1         Definition of the hazardous substance migration
               path for overland flow/flood migration	  8.1, 8.2


MRS Cross Reference                              XXVi

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                              MRS CROSS REFERENCE (continued)

MRS Rule                                                                                 HRSGM
Section        MRS Rule Section Title                                                  Section(s)

4.1.1.2         Target distance limit	  8.1, 8.2, 8.5, 8.7, 8.8, 8.12, 8.14

4.1.2.1.1       Observed release	  5.1, 5.2,5.3
                                                                                         8.5,8.12
4.1.2.1.2.1.1    Containment	  8.4

4.1.2.1.2.1.2    Runoff  	  8.1, 8.2

4.1.2.1.2.1.3    Distance to surface water	  8.1

4.1.2.1.2.2.1    Containment	  8.4

4.1.2.1.2.2.2    Flood frequency	  8.4

4.1.2.1.2.2.3    Calculation of the factor value for potential to release by flood	 8.4

4.1.2.1.2.3     Calculation of potential to release factor value	  8.4

4.1.2.3         Drinking water threat - targets	8.5, 8.7, 8.9

4.1.2.3.1       Nearest intake  	  8.3, 8.7, 8.8, 8.10

4.1.2.3.2       Population  	  8.7, 8.8, 8.9, 8.10

4.1.2.3.2.1      Level of contamination	  8.7

4.1.2.3.2.2     Level I concentrations 	  8.7

4.1.2.3.2.3     Level II concentrations	  8.7

4.1.3.2.1.3     Bioaccumulation potential	  8.3, 8.12

4.1.3.3         Human food chain threat - targets  	8.5, 8.12, 8.13

4.1.3.3.1       Food chain individual	  8.12

4.1.3.3.2       Population  	  8.12, 8.13

4.1.3.3.2.1      Level I concentrations 	  8.12, 8.13

4.1.3.3.2.2     Level II concentrations	  8.12, 8.13

4.1.3.3.2.3     Potential human food chain contamination	  8.13

4.1.4.2.1.1      Ecosystem toxicity 	  8.3

4.1.4.2.1.3     Ecosystem bioaccumulation potential	  8.3

4.1.4.3         Environmental threat - targets 	  8.5,8.14,8.15,8.16
                                              XXVII                               MRS Cross Reference

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                              MRS CROSS REFERENCE (continued)

MRS Rule                                                                                HRSGM
Section        MRS Rule Section Title                                                  Section(s)

4.1.4.3.1        Sensitive environments  	  8.3,8.14,8.15, 8.16

4.1.4.3.1.1      Level I concentrations  	8.14, 8.15, 8.16

4.1.4.3.1.2     Level II concentrations	8.14, 8.15, 8.16

4.1.4.3.1.3     Potential contamination  	  8.14, 8.16

4.1.4.3.1.4     Calculation of environmental threat - targets factor category value	  8.14

5.0.1           General considerations	  4.1
                                                                                      5.1,5.2, 5.3
                                                                                           9.1,9.8

5.1             Resident population threat	  9.6

5.1.1           Likelihood of exposure	  9.1

5.1.2           Waste characteristics	  9.1

5.1.2.1         Toxicity  	  9.2

5.1.2.2         Hazardous waste quantity	  9.2

5.1.3           Targets	  9.3, 9.4, 9.5, 9.6

5.1.3.1         Resident individual	  9.3, 9.4

5.1.3.2         Resident population	  9.3, 9.4

5.1.3.3         Workers	  9.3, 9.5

5.1.3.4         Resources 	  9.3, 9.5

5.1.3.5         Terrestrial sensitive environments  	  9.3, 9.6

5.1.3.6         Calculation of resident population targets factor category value	  9.5

5.2            Nearby population threat 	  9.8

5.2.1           Likelihood of exposure	  9.1

5.2.1.1         Attractiveness/accessibility	  9.8

5.2.1.2         Area of contamination  	  9.2, 9.8

5.2.2.1         Toxicity  	  9.2

5.2.3           Targets	  9.8

6.1             Likelihood of release  	  10.1


MRS Cross Reference                              XXViM

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                             MRS CROSS REFERENCE (continued)

MRS Rule                                                                               HRSGM
Section        MRS Rule Section Title                                                Section(s)
6.1.1           Observed release   	5.1, 5.2, 5.3
                                                                                            10.1

6.1.2           Potential to release	   10.2

6.1.2.1         Gas potential to release	   10.2

6.1.2.2         Particulate potential to release	   10.2

6.1.2.3         Calculation of potential to release factor value for the site	   10.2

6.3             Targets 	 10.3, 10.4, 10.5

6.3.1           Nearest individual	   10.3

6.3.2           Population  	   10.3

6.3.2.1         Level of contamination	   10.3

6.3.2.2         Level I  concentrations 	   10.3

6.3.2.3         Level II concentrations	   10.3

6.3.3           Resources  	   10.4

6.3.4           Sensitive environments  	   10.5

6.3.4.1         Actual contamination  	   10.5

6.3.4.2         Potential contamination  	   10.5

6.3.4.3         Calculation of sensitive environments factor value	   10.5
                                              XXIX                               MRS Cross Reference

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                                       ACRONYMS

AALAC        ambient aquatic life advisory concentration
AOC          area of observed contamination
AWQC        ambient water quality criteria
BCF          bioconcentration factor
BIA           Bureau of Indian Affairs
BLM          Bureau of Land Management
BPF          bioaccumulation potential factor
BPFV         bioaccumulation potential factor value
BTAG         Biological Technical Assistance Group
CERCLA      Comprehensive Environmental Response, Compensation, and Liability Act
CERCLIS      Comprehensive Environmental Response, Compensation, and Liability Information
              System
CERI          Center for Environmental Research Information
CFR          Code of Federal Regulations
CLP          Contract Laboratory Program
CRDL         contract-required detection limit
CRQL         contract-required quantitation limit
ODD          dichloro-diphenyl-dichloro-ethane
DDE          dichloro-diphenyl-ethane
DDT          dichloro-diphenyl-trichloro-ethane
DL            detection limit
DNAPL        dense non-aqueous phase liquid
DOE          Department of Energy
DOT          Department of Transportation
EIS           environmental impact statement
EP            Extraction Procedure
EPA          Environmental Protection Agency
ES            sensitive environment
FDAAL        Food and Drug Administration advisory level
FRDS         Federal Reporting Data System
FWRS        Fish and Wildlife Reference Service
CIS           Geographic Information System
GW           ground water
HFC          human food chain
MRS          Hazard Ranking System
HRSGM       Hazard Ranking System Guidance Manual
HWQ          hazardous waste quantity
IAG           interagency agreement
IDL           instrument detection limit
LNAPL        light non-aqueous phase liquid
LR            likelihood of release
MCL          maximum contaminant level
MCLG         maximum contaminant level goal
MDL          method detection limit
MMS          Minerals Management Service
NAAQS        National Ambient Air Quality Standard
NAWDEX      National Water Data Exchange
NCP          National Contingency Plan
NESHAP      National Emission Standard for Hazardous Air Pollutants
NMFS         National Marine Fisheries Service
NOAA         National Oceanic and Atmospheric Administration
NPDES        National Pollution Discharge Elimination System
NPL          National Priorities List
                                           XXXI
                                                                                  Acronyms

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                                  ACRONYMS (continued)

NPS          National Park Service
NRC          Nuclear Regulatory Commission
NSFF         National Sport Fishing Federation
NWI          National Wetlands Inventory
OSM          Office of Surface Mining
OSWER       Office of Solid Waste and Emergency Response
OVA          organic vapor analyzer
OWRS        Office of Water Regulations and Standards
PA           preliminary assessment
PCB          polychlorinated biphenyls
PPE          probable point of entry
PRP          potentially responsible party
QA           quality assurance
QC           quality control
RCRA         Resource Conservation and Recovery Act
RI/FS         remedial investigation/feasibility study
RREL         Risk Reduction Engineering Laboratory
SACM         Superfund Accelerated Cleanup Model
SARA         Superfund Amendments and Reauthorization Act
SAV          submerged aquatic vegetation
SC           screening concentration
SCDM         Superfund Chemical Data Matrix
SCS          Soil Conservation Service
SDWA        Safe Drinking Water Act
SF           slope factor
SI            site inspection
SQL          sample quantitation limit
SW           surface water
SWDA        Solid Waste Disposal Act
TCLP         Toxicity Characteristic Leaching Procedure
TDL          target distance limit
TSCA         Toxic Substances Control Act
TSDF         treatment, storage, or disposal facility
USC          U.S. Code
USDA         U.S. Department of Agriculture
USFS         U.S. Forest Service
USFWS       U.S. Fish and Wildlife Service
USGS         U.S. Geological Survey
UV           ultraviolet
WC           waste characteristics
WPA          wellhead protection area
Acronymns
                                           XXXII

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CHAPTER 1
INTRODUCTION
       The Hazard Ranking System Guidance Manual (HRSGM) provides general and technical
guidance for individuals involved in determining Hazard Ranking System (HRS) scores and preparing
HRS scoring packages. The HRSGM clarifies terms and concepts in the HRS, presents strategies and
specific guidance for scoring selected HRS factors, and provides guidelines to assist in collecting and
organizing relevant data. Although it is targeted primarily to HRS scorers and package prepares
(frequently contractors or state agency staff), others involved in the U.S. Environmental Protection
Agency's (ERA'S) site assessment process (e.g., package reviewers) may find parts of the document
useful.

       This document has certain limitations. The HRSGM does not account for the  infinite ways in
which conditions may vary from one site to another. Thus, all parts of the guidance may not apply to
every site. Scorers should consider Site- specific conditions and consult, as appropriate, the EPA
Region's National Priorities List (NPL) Coordinator, the Regional Site Assessment Manager, the Site
Assessment Regional Coordinator at EPA Headquarters, Quality Assurance (QA) staff, field
investigators, and other personnel associated with the site assessment process. The HRSGM focuses on
scoring guidance, such as where to find  information  and how to calculate factor values, rather than on
documentation requirements for HRS scoring packages. Additionally, the HRSGM is not intended to be
an all-inclusive reference. No specific guidance is provided, for example, on scoring procedures for
radioactive substances or on the ground water to surface water component of the surface water pathway.
The HRS, published as a Federal regulation on December 14, 1990 (55Federal Register 51532),
constitutes the definitive reference and should be consulted throughout the process of scoring a site.
       The remainder of this introductory chapter presents overviews of the HRS and the Superfund
process, describes the content and organization of the HRSGM, and indentifies several related site
assessment guidance documents and scoring tools.

1.1     INTRODUCTION TO THE HRS

       The HRS is the scoring system used by the EPA's Superfund program to assess the relative
threat associated with actual or potential releases of hazardous substances. The HRS is the primary
screening tool for determining whether a site is to be included on the NPL, EPA's list  of sites that are
priorities for further investigation and,  if necessary, response action under the Comprehensive
Environmental Response, Compensation, and Liability Act (CERCLA), 42 USC 9601 ,ef seq. An HRS
score for a site is determined by evaluating four pathways:

              Ground water migration;

              Surface water migration  (composed  of the three threats — drinking water, human food
              chain, and environmental);

              Soil exposure (composed of two threats — resident population and nearby population);
              and

              Air migration.
                                                                                   Chapter 1

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       The scoring system for each pathway is based on a number of individual factors grouped into
three factor categories: (1) likelihood of release (or, for the soil exposure pathway, likelihood of
exposure); (2) waste characteristics; and (3) targets. Individual factors are evaluated and the factor
values are combined mathematically to produce factor category values. To obtain a pathway score (e.g.,
the ground water migration pathway score) the factor category values are multiplied and then normalized
to 100 points. In the case of the surface water migration  and soil exposure pathways, scores are
calculated for each threat and then added to yield the pathway score. The MRS site score, which ranges
from 0 to 100, is obtained by combining the four pathway scores using the following root-mean-square
equation:
                                   s =


where: S      = site score
       Sgw    = ground water migration pathway score
       Ssw    = surface water migration pathway score
       Ss     = soil exposure pathway score
       Sa     = air migration pathway score

Under this equation, higher scoring pathways have a greater relative impact on the overall site score
than lower scoring pathways. Section 3.4 explains the mathematics of scoring in more detail.

       Any site scoring 28.50 or greater is eligible for the NPL. This score does not represent a
specified level of risk, but is a cutoff point that serves as a screening-level indicator of the highest priority
releases or threatened releases. Sites that score below 28.50 may be addressed under other Federal and
state response authorities. Some sites that score above  28.50 may be addressed by other Federal
programs.

1.2    OVERVIEW OF THE SUPERFUND PROCESS

       The principal components of EPA's Superfund program are set forth in CERCLA, which was
enacted in 1980 and amended by the Superfund Amendments and Reauthorization Act of 1986 (SARA),
and in the National Contingency Plan (NCP)  (40 CFR 300). The Superfund  program responds to threats
posed by uncontrolled releases of hazardous substances into the environment.

CURRENT SUPERFUND PROCESS

       The process by which EPA determines and implements the appropriate response to releases that
require a remedial response action consists of two phases (seeHighlight 1-1):

              Site assessment: screening-level evaluation of all sites to determine those for which
              response action may be required, culminating in the listing of sites on the NPL, where
              appropriate; and

              Remedial response action: comprehensive evaluation of NPL sites to determine the
              nature and extent of contamination, and to select and implement any necessary site
              cleanups.

Releases that require immediate or short-term response actions are addressed under the removal
portion of the Superfund program,

       The site assessment phase begins with site discovery,  or notification to EPA of possible
releases of hazardous substances. Sites are discovered by various parties, including EPA Regional
offices, state agencies, and citizens who petition EPA to perform a preliminary assessment. Once
Chapter 1

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               HIGHLIGHT 1-1
        THE SUPERFUND PROCESS
            SITE ASSESSMENT PHASE
            Site Evaluation Accomplished (Information Provided
               to States and Other Regulatory Authorities)
   Removal and Enforcement Actions May Occur at Any Stage
                REMEDIAL PHASE
Removal and Enforcement Actions May Occur at An/ Stags
                                                                Chapter 1

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discovered, sites are entered into the Comprehensive Environmental Response, Compensation, and
Liability Information System (CERCLIS), EPA's computerized inventory of potential hazardous substance
release sites. EPA then evaluates the potential for a release of hazardous substances from the site
during two investigative steps:

              Preliminary Assessment (PA): A PA is a limited-scope  investigation performed on  every
              CERCLIS site. PA investigators collect readily available information about a site and its
              surrounding area. The PA is designed to distinguish, based on relatively limited data,
              between sites that pose little or no threat to human health and the environment and  sites
              that may pose a threat and thus require further investigation. The PA also identifies  sites
              requiring assessment for possible emergency response (i.e., removal) actions.

              Site Inspection (SI): If the PA results in a recommendation for further investigation, an SI
              is performed. The objectives of the  SI are to identify which sites have a high probability
              of qualifying for the NPL and to collect the data needed for MRS scoring and
              documentation. SI investigators typically collect environmental and waste samples to
              determine what hazardous substances are present at a site, whether they are being
              released to the environment, and whether they have reached nearby targets. The SI can
              be conducted in one stage or in two. The first stage, or focused SI, tests critical
              hypotheses developed during the PA and, in some cases, yields information sufficient to
              prepare an  MRS scoring package. If further information is necessary to document an
              MRS score, an expanded SI is conducted.

       Information collected during the PA and SI is used to calculate an MRS score. Sites with an  MRS
score of 28.50 or greater are eligible for listing on the NPL and require the preparation of a complete
MRS scoring package, including a site narrative summary, Quality Control (QC) checklist, QA signature
page, MRS scoresheets, MRS documentation record and references, and NPL characteristics data
collection form. Section 3.2 discusses the  MRS scoring package.

SUPERFUND ACCELERATED CLEANUP MODEL

       EPA recently developed the Superfund Accelerated Cleanup Model (SACM) to increase the
efficiency of the Superfund program by streamlining cleanup efforts at  all Superfund sites. The traditional
Superfund response follows a prolonged initial phase of study and  assessment, while SACM is designed
to combine immediate action with continuing study as necessary. SACM is a new process for new sites
and an administrative improvement for processing existing sites.

       SACM involves the  following five elements: (1) a one-step screening and risk assessment at the
beginning  of the process; (2) Regional Decision Teams to serve as "traffic cops" for all sites to ensure
quick yet thorough risk reduction; (3) early actions to reduce immediate risk to human health  and the
environment; (4)  long-term actions to  address sites expected to require more than five years to clean up;
and (5) a combination of enforcement, community relations, and public involvement throughout the
process. Benefits of SACM include measuring success by total risk reduction  at all Superfund sites and
making long-term restoration a separate activity. SACM will restore public confidence through early  risk
reduction,  balancing priorities by cleaning up the worst sites first, and cleaning up a large number of
sites.

       Under SACM, EPA can institute actions to address threats  to health and safety of the
surrounding population and environment as soon as those threats are  identified, using removal action
authority or early remedial action authority. The remedial action can be long-term, such as ground water
restoration, or short-term, such as soil treatment. Whenever possible, Superfund assessment activities
should  be  conducted concurrently with short-term removal and long-term remedial actions. For instance,
under SACM EPA may decide to conduct the SI and the remedial investigation, which previously were
separate activities, as a single investigation at sites that are expected to require significant response
action.
Chapter 1

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       Consistent with the NCR, listing sites on the NPL will continue to be a prerequisite to using
certain remedial action authorities to clean up sites. The MRS will continue to be the primary basis for
selecting sites for the NPL.

1.3    ORGANIZATION OF THE HRSGM

       The HRSGM is organized in two parts. The first provides guidance on broad policy issues
and an introduction to the site scoring  process. These chapters, intended to be read through in their
entirety, are:

              Chapter 1:     Introduction
              Chapter 2:     Policy and Statutory Issues
              Chapters:     The MRS Scoring Process.

       The second part of the HRSGM provides specific, detailed guidance on various topics important
to MRS scoring. Each section within these chapters addresses a particular topic and provides
self-contained guidance.  Chapters need not be read in their entirety, but rather are intended to be used
primarily as reference material for specific topics, or to answer specific questions.  Chapters 4 through 6
and Appendix A provide guidance on topics that relate to more than one MRS pathway:

              Chapter 4:     Sources
              Chapters:     Observed Releases
              Chapter6:     Hazardous Waste Quantity
              Appendix A:    Sensitive Environments.

Chapters 7 through 10 address the four MRS pathways:

              Chapter?:     Ground Water Pathway
              Chapters:     Surface Water Pathway
              Chapter 9:     Soil Exposure Pathway
              Chapter 10:    Air Pathway.

A typical section in Chapters 4 through 10 contains the following subsections:

              Introduction: a brief overview of the topic, including its context within the MRS.

              Relevant MRS Sections: a text box referencing relevant MRS section numbers and
              titles.

              Definitions: a subsection defining and clarifying important terms, particularly those
              with HRS-specific definitions.

              How to Score (or How to Evaluate): step-by-step instructions for scoring and/or
              evaluating the relevant factors or topics.

              Topic Icons: graphics in the top right-hand corner of the first page of each section,
              indicating the topic(s) (e.g., air pathway, targets) covered in the section.High light 1-2
              provides a listing of all the icons.

Sections may also include:

              Tips and Reminders: bullet points that present strategies for efficient scoring and data
              collection, identify common mistakes,  and restate key issues.
                                                                                       Chapter 1

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                                  HIGHLIGHT 1-2
      ICONS FOR HRS PATHWAYS, THREATS, AND FACTOR CATEGORIES

i-T-ijS'rtf
:":*
S.\

.:w!
-w i
sj&!

Ground Water
Pathway
                                           Human Food
                                           Chain Threat
             Highlights: text boxes providing reference tables, figures, or other related information,
             such as examples of how to score particular factors under certain, specified
             circumstances or a listing of reference data commonly used to score particular factors
             and suggesting where to obtain such data.

       An index is included at the beginning of the document that cross references HRS rule section
 numbers with relevant HRSGM Sections.

1.4    RELATED SITE ASSESSMENT GUIDANCE MATERIALS

       In addition to the HRS rule and this guidance document, EPA has developed several other
documents and scoring tools to assist investigators with various aspects of the site assessment process.
These include:

             PA Guidance
             SI Guidance
             QC Guidance for NPL Candidate Sites
             PREscore and PA-Score Computer Software and Users Manuals
             Data Useability Guidance for Site Assessment (under development).

Highlight 1-3 compares the audience and scope for each of these site assessment guidance
 documents and scoring tools.
Chapter 1

-------
       Other information about the MRS is available through several "Quick Reference Fact Sheets"
prepared by EPA:

              The Revised Hazard Ranking System: An Improved Too/for Screening Superfund Sites
              (OSWER Publication 9320.7-01 FS, November 1990);

              The Revised Hazard Ranking System: Qs and As (OSWER Publication 9320.7-02FS,
              November 1990);

              The Revised Hazard Ranking System: Background Information (OSWER Publication
              9320.7-03FS, November 1990); and

              The Revised Hazard Ranking System: Evaluating Sites After Waste Removals (OSWER
              Publication 9345.1-03FS, October 1991).
                                                                                  Chapter 1

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                                             HIGHLIGHT 1-3
                         SITE ASSESSMENT GUIDANCE DOCUMENTS AND SCORING TOOLS

Guidance
Document

Reference #

Status/Date



Primary
Audience

Scope and Content

























Guidance for Performing
Preliminary Assessments
Under CERCLA

9345.0-01 A

Final/September 1991



PA Investigations


Provides instructions for
conducting PAs and
reporting the results,
including: determining
CERCLA eligibility;
information required to
evaluate a site; how and
where to find such
information; how to conduct
a site reconnaissance; how
to evaluate a PA site; and
reporting requirements,
format, content, and review.
The purpose of this
document is to assist PA
investigators in conducting
high-quality assessments
that result in correct site
recommendations on a
nationally consistent basis.






Guidance for Performing
Site Inspections
Under CERCLA

9345.1-05

Interim Final/ September
1992


SI Investigators


Provides guidance for the SI
scoping, planning, and
sampling strategies. The
document addresses
focused SI and expanded SI
activities, including
development of field work
plan, sampling strategies,
data analysis and scoring
reviews, and report
preparation. The purpose of
this document is to assist SI
investigators in conducting
efficient, high-quality Sis that
result in correct site
recommendations on a
nationally consistent basis.









Data Useability Guidance
for Site Assessment


9345.1-06

Under Development



Field Technicians,
Data Reviewers, and Data
Analysts
Focuses on the collection,
interpretation, and useability
of chemical analysis data to
support the scoring of sites
under the MRS.





















Hazard Ranking System
Guidance Manual


9345.1-07

Interim Final/ November
1992


MRS Scores.EPARegional
Staff

Provides general and
technical guidance for
prepares of an MRS scoring
package. Guidance includes:
general approach to scoring,
clarification of terms and
concepts in the rule, general
policy issues, and specific
guidance for scoring
selected factors in all
pathways.















Regional Quantity Control
(QC) Guidance for NPL
Candidate Sites

9345.1-08

Final/December 1991



EPA Regional Staff, MRS
Scorers

Provides required and
recommended procedures
for an EPA Regional QC
program for MRS packages.
This guidance is intended to
standardize Regional QC
review and improve MRS
package quality. The
document provides a
checklist that must be
reviewed prior to submitting
the MRS documentation to
Headquarters. It also
provides guidance on a
number of policy issues,
including site definition, the
CERCLA petroleum
exclusion, and the RCRA
policy.







PREscore Users Manual
and Tutorial / PA-Score
Users Manual and
Tutorial
9345. 1-04 (PREscore)
9345.1-11 (PA-Score)
Ver 1.1 /July 1992
(PREscore)
Ver2.0/July1992
(PA-Score)
MRS Scorers


The PREscore Users
Manual and Tutorial provides
instuctions for installing
PREscore on a computer
and a step-by-step lesson on
the use of PREscore The
computer program
calculates MRS scores,
assists in creating
documentation for MRS
scoring packages, and
provides excerpts of the
MRS.

The PA-Score Users Manual
and Tutorial provides
instructions on installing PA-
Score on a computer and
step-by-step lessons on the
use of PA-Score. The
computer program performs
calculations to determine the
PA score.
See also Highlight 3-1 for a
more detailed description of
PREscore.
Chapter 1

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CHAPTER 2
POLICY AND
STATUTORY ISSUES
       This chapter addresses the following key policy issues related to MRS scoring:

              Source and site definition
              Scoring all pathways and threats
              Evaluating sites with waste removals
              CERCLA pollutants or contaminants
              Statutory and policy exclusions.

       Although this chapter presents general information to help the scorer understand policy and
statutory issues, it does not describe specific scoring strategies or provide detailed instructions. These
are provided in the appropriate sections of the guidance.

2.1    SOURCE AND SITE DEFINITION

       This section defines sources and sites and lists criteria for deciding whether multiple sources
should be addressed, for purposes of MRS scoring, as one or more sites (this issue is sometimes referred
to as site aggregation). The section also discusses special considerations for defining sites at Federal
facilities. Section 4.2 addresses the related issue of how to group individual sources to facilitate scoring
at a site that has already been defined to include multiple sources.

       The MRS defines a source as any area where a hazardous substance has been deposited,
stored, disposed, or placed, plus those soils that have become contaminated through migration  (note that
other media contaminated by migration usually are not considered sources). A site, for MRS purposes,
can be any area or areas where a hazardous substance has been deposited, stored,  disposed, or placed,
or has otherwise come to be located (e.g., through  migration). Thus, the definition of site is broader than
the definition of source. A site may include multiple sources and may include the area between sources.
For MRS purposes, the term site does not simply refer to legal property boundaries or fenced-in areas,
but instead refers to the sources of hazardous substances and areas of hazardous substance
contamination  that  are to be scored as a single unit, even if a site is listed for administrative or tracking
purposes (e.g., in CERCLIS) in geographic or ownership terms. The area considered to be the site may
change during the RI/FS and/or later remedial actions as the extent of contamination  becomes better
defined.

MULTIPLE SOURCES

       When  multiple sources are in an area, Regional EPA personnel must decide whether to treat the
area as one site or as several sites for MRS scoring purposes. This decision should be made before
scoring; however, new sources may be discovered  during scoring or later remedial activities, which could
result in redefining  the site. Professional judgment and experience must be used in deciding, on a
case-by-case basis, how to evaluate these newly discovered sources (e.g., whether to treat them as part
of the existing  site under evaluation, or whether to treat the newly discovered sources as a new  site).
Section 4.2 provides more information on evaluating sites where multiple sources may be grouped and
considered a single source to simplify scoring.
                                                                                  Chapter 2

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       Keep in mind the following criteria for defining sites in multiple source situations:

               Proximity of the sources to each other;

               Similarity of wastes contained in the sources;

               Similarity of targets (e.g., potential to affect one or more of the same aquifers, surface
               water bodies, sensitive environments, or populations); and

               Common owner, operator, or potentially responsible party (PRP).

       These criteria are not a comprehensive list of requirements that must be met to address multiple
sources as a single site, but instead are some of the site-specific factors that should be considered.
Present any questions about grouping multiple sources to the EPA Regional contact.

FEDERAL FACILITIES

       Federal facilities are often very large and encompass multiple potential sources of hazardous
substances contamination. Because of their size, and the fact that Sis to collect the data for scoring are
not supervised by EPA, it is not always possible to ensure that all areas of contamination have been
identified, Moreover,  issues of site ownership and the identity of responsible party(ies) are irrelevant to
site definition. Because of these features, Federal facilities may be evaluated as one or more sites,
depending on how the sources are clustered and how the releases are described in the scoring package.
Below are some approaches for evaluating multiple sources at Federal facilities.

               Score the site  based on a small  number of sources, and describe the site at proposal as
               including those sources as well as all other contaminated  areas within the boundaries of
               the facility. Thus, the site would  include  any contamination, either known at the time of
               proposal or discovered later, within those boundaries. This approach should be made
               very clear because of the potentially large scope of the site.

               Fully characterize the sources that drive the MRS score, but also describe other areas
               known or believed to be sources of contamination. Using this method, all sources
               characterized or generally described in the  package,  plus areas contaminated by
               migration from these sources, would be  part of the NPL site.

               Include multiple  sources in the same site if:

               —     They were part of the same operation or activity;
               —     They affect the same target population in one or more pathways; and
               —     They are in the same watershed.

As a general rule, sources at Federal facilities may be combined if the result is real environmental or
cleanup benefits,  even if sources are miles apart.

       Even  if sources at a Federal facility are not contiguous and may contain  different hazardous
substances from different activities, they can be grouped as  a single site. Agency policy, established on
September 8, 1983 (48 Federal Register 40663)  when the first NPL was promulgated, is that
noncontiguous releases and unrelated sources may be grouped together as one site. This policy is
generally appropriate because of the presence of a single responsible party that will serve as lead
agency for any response and with whom EPA may enter into an umbrella Interagency Agreement (IAG)
for the site response. Remember, however, that Federal facilities also may be listed as several sites. For
example, the Department of Energy (DOE) Hanford Facility is listed as four separate NPL sites, each
containing multiple sources.

Chapter 2                                       1 0

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2.2    SCORING ALL PATHWAYS AND THREATS

       The statutory mandate of the MRS is to assess, to the maximum extent feasible, the relative
degree of risk to human health and the environment posed by sites under review. EPA uses the MRS as
a screening tool in its site assessment process to identity sites that merit further investigation under
Superfund. The site assessment program, however, has limited resources for identifying, evaluating, and
scoring large numbers of sites. The competing goals of assessing relative risk to the maximum extent
feasible and screening large numbers of sites have caused some confusion over whether to score all
pathways and threats at a site when the additional effort will not change the site's listing status. The
Agency must balance the need to characterize site risks for all pathways and threats with the constraints
imposed  by the limited resources available for data collection and analysis.

       Generally, all pathways and threats that pose potentially significant  risks to human health and the
environment should be scored to reflect the importance of that pathway or threat to the  overall evaluation
of the site. The scorer should use professional judgment to evaluate the potential seriousness of the risk.
Criteria to consider when deciding whether a pathway or threat should be scored  include:

              Existence of documented releases or contaminated targets
              Potential magnitude of the pathway score
              Availability of scoring data
              Likely range of the overall site score (e.g., near the 28.50 cutoff or not).

       In general, score the pathway if there is an observed release, if targets are subject to actual
contamination, or if there are major target areas for the  pathway.

       If the contribution of a pathway or threat to the overall score is minimal, scoring and fully
documenting the pathway may not be necessary, even if extensive data are available. As a general
guideline, pathways and threats scoring less than  10 points usually do not need to be scored, unless the
overall site score is near the cutoff. (Note that near 28.50, the most a 10-point pathway can add to an
overall score is approximately half a point. See Section 3.4 for more details.) If a pathway is not scored,
the scorer should describe the pathway and available data in the MRS package. This discussion helps
present a more thorough and accurate picture  of conditions at the site and may be useful later in the
remedial process.

       If a site score is close to the cutoff, score all pathways even if they add only a few points to the
overall site score. In many cases, site scores drop after Quality Assurance review or response to public
comments, and the initial inclusion of these additional pathways may keep the site above the cutoff.

       In conclusion, the site assessment process should  not be viewed simply as an exercise to
achieve the maximum MRS score possible by always scoring every pathway, nor as a mechanical
process that automatically ends when a score of 28.50 is reached. The  scorer must make decisions
about whether to score individual pathways or threats based on knowledge of the site, professional
judgment and experience, and an understanding how the site score might be affected.

2.3    EVALUATION OF SITES WITH  WASTE REMOVALS

       A removal action is a relatively short-term response taken to eliminate a threat or prevent more
serious environmental problems resulting from the release of CERCLA  hazardous substances. Under the
original MRS,  a site was scored based on conditions that existed prior to a removal action. Under the
revised MRS, waste removals (a specific type of removal action in which hazardous substances, or
wastes containing hazardous substances, are  physically removed from  a site)  may be considered for
scoring purposes under certain circumstances. This section outlines the requirements for evaluating
removal actions for MRS purposes, defines a qualifying removal, explains how to  determine the cutoff
date for qualifying removals, and discusses other relevant scoring issues. The waste  removal policy is
                                             11                                       Chapter 2

-------
designed to provide an incentive for rapid response actions by PRPs, reducing risks to the public and the
environment and allowing for more timely and cost-effective cleanups. The Agency's waste removal
policy is explained in greater detail in The Revised Hazard Ranking System: Evaluating Sites After Waste
Removals (OSWER Publication 9345.1-03FS, October 1991).

REQUIREMENTS FOR CONSIDERING REMOVAL ACTIONS

       In the preamble to the MRS (55 Federal Register 51567, December 14, 1990), EPA established
three requirements that must be met for the results of a removal action to be considered in scoring a site
with the MRS. A removal  action that meets these three requirements is referred to as a qualifying
removal.

       The first requirement is that the removal action physically remove from the site wastes
containing hazardous substances. Note that it is not necessary that all wastes from the site or even  all
wastes from a particular source  be removed; partial removals can be considered in scoring. This
requirement for actual physical removal ensures that there is  no scoring  benefit for simply moving the
waste and its associated  risks to another portion of the same  site. A removal action conducted under
Superfund's emergency response  program does not necessarily involve  physical removal of wastes from
the site. For example, Superfund removal actions, as defined  in CERCLA section  101(23), may include
stabilizing or containing waste on-site through engineering controls or limiting  exposure potential by
erecting fences or providing alternate water supplies. These types of actions do not constitute a
qualifying removal.

       The second requirement is that the removal must have occurred  prior to the cutoff date
applicable to the site. The MRS  preamble states that EPA will only consider removals conducted prior to
the SI. This requirement encourages prompt action and avoids the need  to resample or rescore sites due
to waste removals conducted after the SI. Because of differences in site  assessment activities for
different types of sites (e.g., EPA-lead, state-lead, Federal facilities), criteria for determining the
appropriate cutoff date differ among sites. The next section provides detailed guidance on determining a
site-specific cutoff date.

       The third requirement is that all waste removed must  be disposed of or destroyed at a facility
permitted, as appropriate, under the Resource Conservation and Recovery Act (RCRA) or the Toxic
Substances Control Act (TSCA) or by the Nuclear Regulatory Commission (NRC). This requirement
encourages proper disposal of the removed waste and discourages simply moving the waste and its
associated hazards to another location.

DETERMINING THE CUTOFF DATE

       The paragraphs below describe how to  determine the cutoff date for non-Federal and Federal
facility sites and for sites  with more than one SI.

Non-Federal Facility Sites with One SI

       An SI for non-Federal facility sites generally begins with development of a workplan, which often
includes the sampling strategy for the site. EPA believes it would disrupt Sis to consider the results of
removal actions conducted after this point because to do so could require revising sampling plans,
resampling, or rescoring the site. Because of variation in the way Regions have historically tracked Sis, it
is impossible to define a single event as the cutoff date for sites that had Sis before the removal policy
fact sheet was distributed in December 1991. Therefore, the cutoff date for those sites generally is the
date development of a workplan for the SI begins. Examples of dates that can  be considered analogous
to workplan development for purposes of determining the cutoff date include:
Chapter 2                                      12

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              SI start date in CERCLIS;

              Date of Technical Decision Document (TDD) or Technical Decision Memorandum (TDM)
              issued for work assignment to develop SI workplan;

              Date when EPA approves the site-specific SI workplan; or

              Date of an SI reconnaissance to develop SI workplan.

       If no workplan or analogous event is available, the  cutoff date is the earliest documented date
that EPA conducted SI activities for the site. For all sites with Sis conducted after December 1991,
Regions are expected to  enter the date of site-specific workplan approval by EPA as the SI start date in
CERCLIS, and that date should be used as the  cutoff date for determining qualifying removals.

       If EPA determines that previous investigations by other parties (e.g., states, EPA's removal
program) are suitable for SI purposes, then the  date when drafting of a Superfund SI report collating
previous analytical data is begun serves as the  cutoff date. The cutoff date is not the date of a state or
PRP investigation conducted independently of CERCLA; the cutoff is based on the date these data are
collated for Superfund SI purposes.

Non-Federal Facility Sites with Multiple Sis

       For non-Federal facility sites with more  than one SI, the cutoff date for most sites will be keyed
to the first SI. However, the Agency may establish a later cutoff date under certain circumstances:

              If a second SI implementing a completely new sampling strategy is conducted, the
              Agency may consider basing the cutoff date on workplan development for the second SI.
              In these cases, considering removals prior to the second SI is not likely to  unduly disrupt
              the site assessment process.

              For sites where the first SI was  conducted more than four years prior to MRS scoring, the
              Agency may consider, on a case-by-case basis, changing the cutoff date to a later date.
              (CERCLA section 116, added by SARA,  mandates that EPA conduct site assessment
              work within four years of CERCLIS listing.)

       The transition to the revised MRS and the follow-up sampling needed for some sites may mean
that site assessment activities take longer than  four years.  Follow-up sampling  should not be used to
determine a new cutoff date in that situation, even if more than four years have elapsed since the first
cutoff date, unless a completely new sampling strategy is implemented.

Federal Facility Sites

       Federal facility sites undergo  a somewhat different site process than other sites. Assessments of
Federal facility sites are expected to be conducted within 18 months of their placement on the Federal
Agency Hazardous Waste Compliance Docket,  set up under CERCLA section 120(c),  added by SARA.
Therefore, the cutoff date for Federal  facility sites is 18 months after the site is  placed on the Federal
facilities docket.

Summary

       Highlight 2-1 is a flowchart for determining a site-specific cutoff date. Highlight 2-2 provides
examples of determining  the cutoff date for hypothetical sites.
                                             1 3                                       Chapter 2

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                                         HIGHLIGHT 2-1
               FLOWCHART FOR IDENTIFICATION OF THE CUTOFF  DATE
               Is the site a Federal
                   facility?
               Has more that one SI
              been conducted for the
                    site?
                                                         Is the date of the
                                                       workplan or analogous
                                                        activity available?
id a later SI implement
 a completely new
sampling strategy?
              Was the first SI more
              than four years prior to
                 HRS scoring?
NO


Use earliest date
of Superfund SI
activities as the
cutoff date.
Chapter 2
                                                 14

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HIGHTLIGHT 2-2
EXAMPLES OF DETERMINING CUTOFF DATE
SITE #1
Site
Assessment
Activities
Cutoff Date
PA was conducted in May 1988
SI sampling took place in October 1989. The date workplan development for SI began
is unknown; however, the date of the Technical Decision Document authorizing the
contractor to develop an SI workplan was dated July 1989.
MRS package prepared began in January 1991.
July 1989: Cutoff date is the date analogous to workplan preparation.

SITE #2
Site
Assessment
Activities
Cutoff Date
No PA was conducted.
The State conducted an independent (i.e., non-Superfund) investigation of this
site, including sampling in May 1988. The State issued a final report of the
investigation in December 1988.
In May 1990, EPA examined the State's December 1988 report. EPA decided this
investigation constituted an SI, and began drafting a Superfund SI report in May 1990.
The report was finalized in July 1990.
MRS package preparation began in August 1991.
May 1990: Cutoff date is the date EPA began drafting an SI report using previous
analytical data, not the date of the state investigation or report on which EPA's report is
based.

SITE #3
Site
Assessment
Activities
Cutoff Date
PA was conducted in January 1989.
EPA's emergency response program conducted a removal assessment in June 1989
and removed a number of corroding drums in July 1989.
Development of an SI workplan began in November 1989. Sampling took place in
March 1990.
MRS package preparation began in February 1991.
November 1 989: Cutoff date is based on development of SI workplan, not on the date
of the removal assessment.
(continued on next page)

15
                                             Chapter 2

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HIGHTLIGHT 2-2 (continued)
EXAMPLES OF DETERMINING CUTOFF DATE
SITE #4
Site
Assessment
Activities
Cutoff Date
PA was conducted In March 1986
SI sampling was conducted by an EPA contractor In January 1987. No date for
workplan development or analogous date Is available. The earliest identified date for
Superfund SI activities Is December 1986.
A second SI with a similar sampling strategy was conducted in September 1989.
Limited sampling to collect additional data to support MRS scoring was conducted In
April 1991.
MRS package preparation began In August 1991.
To be determined: The cutoff date normally would be December 1986. This date
(earliest identified date of Superfund SI activities) is used because the date of workplan
development for the first SI is not available. In addition, the September 1989 and April
1991 SI activities did not implement completely new sampling strategies. However,
bemuse the first SI was conducted more than four years prior to MRS scoring, EPA
may determine a later cutoff date than December 1 986 for the site.


SCORING CONSIDERATIONS WHEN A QUALIFYING REMOVAL HAS OCCURRED

       A qualifying removal affects scoring of the hazardous waste quantity factor and also may affect
the scoring of a number of other MRS factors. Scoring hazardous waste quantity for sites with qualifying
removals is discussed in detail in the removal policy fact sheet. For a qualifying removal, do not count
the amount of waste removed when scoring hazardous waste quantity. For a non-qualifying removal,
score hazardous waste quantity as if the waste was not removed. For a partial qualifying removal, the
waste removed generally may be subtracted from the total amount of waste, if the same hazardous
waste quantity tier (e.g., both must be based on volume) can be used.

       Changes in factors other than hazardous waste quantity caused by a  qualifying removal should
be considered in scoring a pathway only if all of the following conditions are met.

              Change in the factor was a direct result of a qualifying removal. For example, if during a
              qualifying removal waste is removed from a surface impoundment and the impoundment
              is refilled with clean soil, the clean fill can be considered in scoring factors other than
              hazardous waste quantity (e.g., containment) if the following two conditions are also met.

              No observed release of a hazardous substance associated with the source is
              established.  If an observed release associated with the source involved in the qualifying
              removal is established, the effects of the removal are not considered in scoring factors
              other than hazardous waste quantity. This requirement is pathway specific. If, for
              example, an  observed release is established for ground water but not for air or surface
              water, then changes in factors other than hazardous waste quantity can be considered in
              scoring the air and surface water pathways (as long as the other two conditions are also
              met).
Chapter 2
                                             16

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              The removal completely eliminated the source or resulted in a containment factor value
              of zero for the source, if the removal is partial or if changes that result from the removal
              would result in a lower, but non-zero, containment factor value, the effects of the
              removal are not considered in scoring factors other than hazardous waste quantity.
              Again, this  requirement is pathway-specific; the removal may result in a zero
              containment factor value for air but a non-zero containment factor value for ground
              water and surface water.

The requirements above apply to all MRS factors other than hazardous waste quantity. Instructions for
applying these requirements to specific factors are provided below.

Observed Release

       An observed release to a migration  pathway, whether documented before or after a qualifying
removal, can be used to score likelihood of release. That is, a qualifying removal does not negate the
fact that the source has released substances to the  environment. However, areas of observed
contamination in the soil exposure  pathway reflect continuing hazards at the site. Therefore, the soil
exposure pathway factor is  evaluated based on conditions that exist following a qualifying removal.

Source Containment and  Source Type

       Scoring of the containment and, for the air pathway, source type factors is affected only by
qualifying removals that result in a  factor value of 0. Changes in containment or source type that result in
a lower but non-zero factor value are not considered in scoring.

Substance-specific Factors

       Substance-specific factors  cannot be based on a hazardous substance that was completely
eliminated from a pathway by a qualifying removal. Such a removal must eliminate all sources of the
hazardous substance, and  no prior releases of the substance may have occurred. Substance-specific
factors include:

              Toxicity
              Mobility
              Persistence
              Bioaccumulation potential
              Gas migration potential.

       EPA generally will be unable to document complete elimination of a hazardous substance within
the scope of an SI and will rely on PRPs to produce these data. If a portion of a source is eliminated in a
qualifying removal, the remaining portion of that source is assumed to contain the same hazardous
substances as the removed portion, unless the PRP can document otherwise (e.g., provide analytical
results or manifest data that convincingly demonstrate a given hazardous substance is not present in the
remaining portion  of the source).

Targets Factors

       Site-specific TDL (or distance categories) and the distance to nearest targets in migration
pathways may change if a qualifying removal meets the three requirements above. In such cases, the
source is eliminated from the pathway and, therefore, is not used to measure target distances. If a
qualifying removal does not meet the three requirements above (e.g., an observed release of a
hazardous substance associated with the source is  established or the source containment factor value is
non-zero), the source is included when  measuring target distances for that pathway.


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2.4 CERCLA POLLUTANTS OR CONTAMINANTS

       MRS scores on the basis of likelihood of release of hazardous substances into the environment,
waste characteristics (e.g., toxicity and quantity) on site, and the targets potentially affected by releases
from the site. Therefore, the scorer must know what substances can and cannot be considered in
scoring. The MRS definition of hazardous substance, with one exception, includes both CERCLA
hazardous substances and pollutants or contaminants, as defined in CERCLA sections 101 (14) and
101(33). Section 101(14) of CERCLA defines hazardous substances by referencing substances
specifically listed under other Federal laws. Section 101 (33)  of CERCLA does not specifically list the
substances considered to be n pollutants or contaminants," but instead gives the following definition:

       "pollutant or contaminant shall include, but shall not be limited to, any element, substance,
       compound, or mixture, including disease-causing agents, which after release into the
       environment and upon exposure, ingestion, inhalation, or assimilation into any organism, either
       directly from the environment or indirectly by ingestion through food chains, will or may
       reasonably be anticipated to cause death, disease, behavioral abnormalities, cancer, genetic
       mutation, physiological malfunctions (including malfunctions in reproduction) or physical
       deformations,  in such organisms or their offspring... ".

       Thus, the term "pollutant or contaminant" is very broadly defined in CERCLA and could include
any substance known or reasonably anticipated to be harmful to human or ecological health. Because no
substances are actually  listed as pollutants or contaminants, either in CERCLA or in  the MRS, the
Agency determines on a case-by-case basis which substances fall within the definition. This
determination is important because pollutants or contaminants may, for example, contribute to the waste
quantity factor value, be used to determine substance-specific factor values, and affect source
identification and targets evaluation. Direct any questions regarding whether a substance is a pollutant or
contaminant, or how to score a site involving pollutants or contaminants, to the EPA Regional Site
Assessment Manager.

       These two basic MRS scoring scenarios involve releases of pollutants or contaminants:

              Substances at the site include only pollutants or contaminants (i.e., no CERCLA
              hazardous substances). This scenario  is relatively unusual. Most sites that have been
              identified for potential listing contain a number of substances, usually including CERCLA
              hazardous substances. However, even if no  GERCLA hazardous substances are
              identified, the site can be scored and is eligible for the NPLif at least one substance
              present is documented to be a CERCLA pollutant or contaminant. In  these situations, the
              standard MRS scoring process is followed, except that Tier A under the hazardous waste
              quantity factor is not applicable.

              Substances at the site include both CERCLA hazardous substances  and pollutants or
              contaminants. The scorer should follow the standard MRS scoring process. Before using
              a substance that is not a CERCLA hazardous substance in scoring, document that the
              substance qualifies as a CERCLA pollutant or contaminant.

       Pollutants or contaminants are treated the same in the MRS as CERCLA hazardous substances
except pollutants or contaminants cannot be used to score Tier A of the hazardous waste quantity factor.

2.5 STATUTORY AND POLICY EXCLUSIONS

       A number of statutory and policy provisions affect a site's eligibility for CERCLA response
actions and listing the NPL. CERCLA specifically excludes certain types of releases and wastes from
response actions, and in  some cases, it is more appropriate to conduct response under another


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statutory authority. This section summarizes several statutory and policy exclusions that MRS scorers
may encounter.

       Although a site's eligibility for the NPL should be determined before MRS scoring begins, new
information may surface during scoring that relates to site eligibility. MRS scorers should be familiar with
general site eligibility considerations so they can recognize issues that need to be addressed by EPA
Regional staff. For additional information on determining a site's eligibility under CERCLA, seeGuidance
for Performing Preliminary Assessments Under CERCLA (OSWER Publication 9345.0-01, September
1991) and Regional Quality Control Guidance for NPL Candidate Sites  (OSWER Publication 9345.1-08,
December 1991).

CERCLA PETROLEUM EXCLUSION

       CERCLA sections 101  (14) and (33) exclude petroleum from the definitions  of "hazardous
substance" and "pollutant or contaminant," respectively. The exclusion applies to petroleum, including
crude oil or any fraction thereof (if the fraction is not specifically listed  nor designated a hazardous
substance by other listed acts), natural gas,  natural gas liquids, liquified  natural gas, and synthetic gas
usable for fuel.

       The Regional Quality Control (QC) Guidance for NPL Candidate Sites (OSWER Publication
9345.1-08, December 1991) raises several issues to consider when scoring a site possibly containing
petroleum or petroleum products:

              CERCLA does not define petroleum. Crude petroleum includes a number of hazardous
              substances that would otherwise be CERCLA hazardous substances, such as benzene,
              toluene, xylene, and ethylbenzene. In their pure forms, these substances remain
              hazardous substances and can be scored. When they are part of, or released directly
              from, a petroleum product, they cannot be used in scoring.

              The presence of petroleum products at a site, as a part of site contamination, does not
              exclude the site from consideration. Sites are excluded if they contain  only excluded
              petroleum products.

              Releases of petroleum products contaminated with hazardous substances (i.e., used
              oil/waste oil contaminated with metals or PCBs) can be listed if the hazardous
              substances cannot be separated from the petroleum.

              If two distinct plumes commingle, one of petroleum and one of a hazardous substance
              that can be listed, the release can be listed: however,  only the non-petroleum plume can
              be used in MRS scoring.

              A petroleum release can be  used to show aquifer interconnection.

RADIOACTIVE MATERIALS

       Section 101  (22) of CERCLA excludes a limited category of radioactive materials from the
statutory definition of "release," making them ineligible for CERCLA response or the NPL. These are (1)
releases of source (uranium orthorium, or any combination of the two, in any physical or chemical form),
by-product (any radioactive material that was made radioactive by exposure to radiation from the
process of using or producing special nuclear material), or special nuclear material (plutonium,
uranium-233, enriched uranium-233 or -235, or any material that the NRC determines to be special
nuclear material (not including  source material)) subject to section 170 of the Atomic Energy Act; and (2)
any release of source, by-products, or special nuclear material from any  processing site specifically
designated under the Uranium Mill Tailings Radiation Control Act of 1978.
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       The exclusion of these substances does not exclude other types of radioactive materials.
However, it is Agency policy not to list releases of radioactive materials from facilities with a current
license issued by the NRC (e.g., certain medical facilities, manufacturing plants, research laboratories).
These facilities are under the authority of the NRC which is responsible for requiring and overseeing
cleanup at these sites. All other types of radioactive materials sites,  including state licensees and former
NRC licensees, are eligible for the NPL.

RCRA SITE POLICY

       In general, it is Agency policy to use RCRA Subtitle C authority to respond to sites that can be
addressed under RCRA Subtitle C corrective action authority, and not to place such sites on the NPL
(see generally, 54 Federal Register 41000, October 4, 1989). According to the Agency's NPL/RCRA
deferral policy, however, some facilities subject to RCRA Subtitle C authority may be placed on the NPL
when  corrective action is unlikely to succeed (refer  to the QC Guidance for more details). Sites subject to
corrective action under RCRA Subtitle C authority which may be placed on the NPL include:

              Treatment, storage, or disposal facilities (TSDFs) that have demonstrated an
              unwillingness to undertake corrective actions;

              TSDFs that have demonstrated an  inability to pay for cleanup, as evidenced by a
              bankruptcy filing or similar action;

              Former treatment or storage facilities that did not pursue a RCRA operating permit and
              have changed their RCRA status to "generator" or "non-handier" (these facilities are
              sometimes referred to as "converters"); and

              RCRA "Non- or Late Filers" (i.e., facilities that operated as TSDFs after the statutory
              deadline but either did not notify EPA or delayed notification).

       If the scorer finds new evidence indicating that the site may  be eligible for RCRA Subtitle C
corrective action, notify the Regional EPA Site Assessment Manager.
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CHAPTER  3
THE  HRS SCORING
PROCESS
       This chapter provides an introduction to the process by which HRS packages are prepared,
identifies the elements of a complete package, describes the package review process, and discusses
effective scoring strategy. The approach and strategy for implementing the HRS discussed in this
chapter are very broad; Chapters 4 through 10 and Appendix A present more specific guidance for
scoring particular pathways, threats, and factors.

3.1    GENERAL APPROACH TO HRS SCORING

       This section outlines an eight-step approach that breaks down the HRS scoring process into a
series of manageable tasks. Although geared to the inexperienced HRS scorer, this approach can serve
as a guide for experienced scorers as well. The approach presented here is only a suggested one;
experienced scorers may develop their own approaches. In addition, because every site is different, an
approach appropriate for one site  may be  inappropriate for another.

       Throughout the scoring process, all information used in scoring must be recorded in the HRS
documentation record. EPA has developed a computer software package (and companion user's
manual) called PREscore, which automates HRS scoring and allows the scorer to enter limited narrative
descriptions of scoring rationales and data sources. The PREscore printout can serve as a starting point
for the final HRS documentation record. See Highlight 3-1 for an introduction  to PREscore.
                                     HIGHLIGHT 3-1
                       THE PRESCORE SOFTWARE PROGRAM

 The PREscore software package includes the PREscore and PREprint computer programs, as well as a users
 manual and tutorial (OSWER Dir. 9345.1-04). PREscore provides an efficient and convenient means of scoring sites
 using the HRS. PREscore performs HRS calculations from some raw data, retrieves values from hazardous
 substance reference tables, and calculates pathway and sites cores. PREprint generates HRS score sheets, an HRS1
 documentation record, and an NPL characteristics data collection form. The user's manual provides instruction for
 installing and using PREscore and PREprint.

 PREscore partially automates HRS scoring, allowing for entry and evaluation of site-related information such as
 sampling data, waste quantities, waste characteristics, physical parameters of the site, and population data. Scorers
 can enter descriptive narrative text and reference citations to document the selection of specific HRS factor values
 and scoring decisions.

 PREscore users must be familiar with the HRS. The software does not provide detailed HRS instructions, although
 help screens with text from the HRS are available throughout  the program.  PREscore contains  HRS related
 information  on over 300 hazardous substances that may be encountered at Superfund sites. This information
 includes substance characteristics (such as toxicity and persistence) and concentration benchmarks.

 For more information on PREscore, contact the appropriate Regional NPL Coordinator.
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STEP 1: ASSEMBLE AND REVIEW ALL AVAILABLE SITE INFORMATION

       Scorers often have limited first-hand knowledge of a site when they begin an MRS evaluation.
Thus, the first step is to become familiar with the site by assembling and reviewing existing documents, a
step sometimes referred to as a "file search." The PA and SI reports should contain most of the relevant
site data collected to date. In addition, any preliminary MRS scoring results (e.g., PA-Score results)
should be reviewed as a means of generating hypotheses about which pathways and factors are likely to
be most significant in scoring the site.

       When reviewing available information about a site, be sure to consider the following questions:

              What are the primary sources at the site? Are other (i.e., not part of the site) potentially
              important sources of hazardous substances nearby? (As in the MRS rule, the term
              "hazardous substance" is defined in this guidance document to include both CERCLA
              hazardous substances and CERCLA pollutants or contaminants; see Section 2.4 for
              additional related discussion.)

              What hazardous substances are associated with the site, and in what quantities are they
              present? Are they at least partially attributable to sources at the site?

              Have any observed  releases or areas of observed contamination been documented?

              Are there any major targets (e.g., populations, municipal wells, fisheries, sensitive
              environments) located near the site (i.e., within the TDLs)? Are any targets located on or
              very near (e.g., within  1/2 mile) sources at the site?

              Are any targets exposed to actual contamination that is at  least partially attributable to
              the site? If so, are there any data indicating the hazardous substance concentrations to
              which targets have been exposed?

       The answers to these questions will provide a basic understanding of the nature of the threat
posed by the site and will assist in determining  whether available information contains  any significant
"gaps" that  require additional investigation.

       The scorer also should consider up front the site definition (i.e., which specific sources and/or
areas of contamination comprise the site) and the site's eligibility for the NPL (see Sections 2.1 and 2.5).
Both of these issues should have been resolved before MRS scoring and package preparation begins,
but the scorer should confirm that the issues have been addressed.

STEP 2: IDENTIFY AND CHARACTERIZE SOURCES

       Understanding the sources (and, for the soil exposure pathway,  areas of observed
contamination) at a site is one of the keys to MRS scoring. The MRS defines a source as any area where
a hazardous substance has been deposited, stored, disposed, or placed, plus anysoilsthat have  been
contaminated through migration (contaminated  media other than soil usually are not considered
sources). A site may include multiple sources and/or areas of observed contamination.

       With this definition  in mind, review source-related information and  complete the source
characterization portion of the MRS documentation record. Describe the dimensions and identify the
hazardous substances associated with each source,  and classify each source into a source type  category
(the assigned category can vary by pathway). Then, for each source, determine the containment
characteristics and evaluate hazardous waste quantity for each pathway.
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       Evaluate source information to determine if:

              A source has been eliminated through a qualifying removal action and there is no
              observed release is associated with that source (see Section 2.3).

              A source has a containment factor value of zero for each migration pathway and an
              attractiveness/accessibility factor of zero for the soil exposure pathway.

If either of these conditions applies, do not use the source in scoring the site.

STEP 3: IDENTIFY AND CHARACTERIZE SIGNIFICANT PATHWAYS

       While the potential hazards should be described qualitatively (at a minimum) for all MRS
pathways, some pathways and threats may not be scored for a particular site. The identification of
significant pathways depends to a large degree on professional judgment based on knowledge of the site
and preliminary MRS scoring results. As a general rule, a pathway should be considered significant at
this early stage of the scoring process if either of the following conditions is met: (1) there is an observed
release (or observed contamination) for that pathway; or (2) several major target areas are within the
TDL for that pathway. See Section 2.2 for general considerations about scoring all pathways and Section
3.4 for more quantitative guidance on the efficiency of scoring particular pathways.

       The following are some of the more significant MRS considerations and information needs when
characterizing  pathways to be scored. See Chapters 7 through 10 for more detailed pathway-specific
guidance.

Ground Water Pathway

              Evaluate all aquifers used as sources of potable water. The aquifer that yields the
              highest score is used to evaluate the pathway.

              Identify the geologic formations present (including known aquifer boundaries,
              discontinuities,  and  interconnections), especially underlying aquifers used for drinking
              water supply. Identify any karst aquifers within the TDL.

              Determine whether there has been an observed release of a hazardous substance
              from the source(s) to one or more aquifers.

              Identify ground  water uses and well locations within the TDL.

Surface Water Pathway

              Identify all surface water bodies within the TDL.

              Determine whether multiple watersheds exist. If so, evaluate all watersheds. The
              watershed that yields the highest score is used to evaluate the pathway.

              Evaluate the hazardous substance migration path(s),  including the overland
              segment(s) (including runoff routes, distance from source to surface water) and the in-
              water segment(s) (including probable point of hazardous substance entry, TDL(s)) for
              all surface waters to which hazardous substances have been or have the potential to
              be released, or have floodplains that include a source at the site.

              Determine whether there has been an observed release of a hazardous substance
              from the source(s) to surface water.

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               Evaluate waste characteristics carefully, particularly for the human food chain and
               environmental threats because the maximum waste characteristics factor category value
               is 1,000 (rather than 100) in these threats due to consideration of bioaccumulation
               potential.

               Identify surface water uses (e.g., drinking water intakes, fisheries) within the TDL.

               Identify all sensitive environments within the TDL.

               Determine which of the three threats (drinking water, human food chain, and
               environmental) should be scored. Human food chain and environmental threats may
               score high if a substance with a bioaccumulation potential factor value of 500 or greater
               is present.

               Evaluate whether the ground water to surface water component should be scored. Note
               that no specific guidance on this component is provided in this manual.
Soil Exposure Pathway
               Identify and delineate areas where hazardous substances have been documented within
               2 feet of the surface and do not lie beneath an essentially impenetrable cover (i.e, the
               areas of observed contamination). If no such areas have been documented, assign a
               zero to the pathway score.

               Identify property boundaries for areas of observed contamination.

               Determine the 200-foot distance from areas of observed contamination for the resident
               population threat.

               Identify land uses within areas of observed contamination.

               Identify all terrestrial sensitive environments at least partially within areas of observed
               contamination.

               Determine the 1/4-mile, 1/2-mile, and 1-mile travel distances for the nearby population
               threat. (Travel distances need not be straight line measurements.)
Air Pathway
               Determine whether there has been an observed release of a hazardous substance from
               the source(s) to air.

               Evaluate gas potential to release for sources with gaseous hazardous substances and
               particulate potential to release for sources with particulate hazardous substances.
               Evaluate both for sources with both types of hazardous substances.

               Identify land uses within the TDL.

               Identify all sensitive environments in the TDL.

STEP 4: EVALUATE TARGETS FOR SIGNIFICANT PATHWAYS

       Targets consist of people, sensitive environments, fisheries, and resources that potentially can
be affected by a site. The MRS targets factor category is the only category that has no maximum value.
The relative contribution of a particular target to the overall site score is determined by its assigned point
value and the level of contamination to which the target is subject. For each significant



Chapter 3                                      24

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pathway, identify all targets within the appropriate TDL and determine whether they are exposed to Level
I, Level II, or potential contamination.

       The following is a list of general guidelines for evaluating targets by pathway. For more detailed
guidance, see the appropriate sections of Chapters 7 through 10. Refer to Appendix A for additional
information on sensitive environments.

Ground Water Pathway

               Identify all wells drawing water from the aquifer(s) of concern.

               Determine whether ground water wells are part of a blended water supply system
               (including blending with surface water intakes), as this will affect the targets
               calculations.

               Identify and evaluate standby wells and emergency ground water supplies.

               Identify private drinking water wells and determine populations that rely on them for
               drinking water. Some private wells are not used as drinking water supplies.

               Focus on populations subject to actual contamination (Level I  or Level II or within 1
               mile of a source,  as these generally will dominate the targets factor category value.
               Do not, however, ignore large populations beyond 1  mile.

               Collect sufficient data to be confident that the population subject to contamination
               within each distance category falls within the range of populations assigned the same
               factor value.

Surface Water  Pathway

               Estimate average annual flow for all streams and rivers within the TDL. If the site is near
               an ocean or the Great Lakes, estimate the depth of these water bodies within the TDL.

               Focus on targets subject to actual contamination (Level I or Level II) or located on water
               bodies with an average annual flow of 100 cubic feet per second or less (i.e., high value
               for dilution weight multiplier), as these generally will dominate the targets factor category
               value.

               If actual contamination of targets cannot be established,  identify the presence of
               significant targets (drinking water intakes, fisheries, sensitive environments) and
               calculate target factor category values after applying the appropriate dilution weight for
               the water bodies  in which these targets are located.

               Determine whether drinking water intakes are part of a blended water supply system
               (including blending with ground water wells), as this will affect the targets calculations.

               Identify and evaluate standby intakes and emergency surface water supplies.

               Evaluate nearest intake and food chain individual values.

               Collect sufficient data to be confident that the population subject to contamination within
               each distance category falls within the range of populations assigned the same factor
               value.
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Soil Exposure Pathway

              Focus on the resident population threat; the nearby population threat rarely will affect the
              pathway score significantly.

              Determine whether observed contamination exists that is within the property boundary
              and within 200 feet of any residences, day care centers, schools, or work areas.

              Determine whether observed contamination exists in terrestrial sensitive environments.

Air Pathway

              Identify all individuals regularly occupying areas an or near sources.

              Focus on populations and sensitive environments subject to actual contamination (Level
              I  or Level II) or within 1/4 mile of a source, as these generally will dominate the targets
              factor category value.

              Collect sufficient data to be confident that the population subject to contamination within
              each  distance category falls within the range of populations assigned the same factor
              value.

STEP 5: COLLECT ADDITIONAL INFORMATION, IF NECESSARY

       At this stage of the MRS scoring process, the scorer should assess whether the available
information is sufficient to document all the MRS factors relevant to the site's score. If not, collect the
additional  information needed. This may include verifying target populations. Additional sampling may be
considered for a number of reasons, including:

              To score all MRS factors for all significant pathways;

              To replace low-quality chemical analysis data that support observed releases, and/or the
              calculation of targets exposed to actual contamination;

              To replace other low-quality data, if required;

              To attribute hazardous substances to sources at the site; and/or

              To establish representative background levels (in most cases, additional "release"
              samples would need to be collected at the same time background levels are
              established).

       This step will  not be necessary for all sites. In general, additional data collection at this point
should focus on those factors critical to the site's MRS score.

STEP 6: CHECK VALIDITY OF FACTOR VALUES

       The calculation of factor values should be reviewed to determine whether the 'best" data
available have been used for scoring and whether the professional judgments made in scoring are
appropriate. It is strongly recommended that inexperienced scorers consult more experienced scorers for
this review. Areas that require a particularly thorough review include:

               Source characterization
               Hazardous waste quantity
               Aquifer boundaries, discontinuities, and interconnections
               Quality of sampling data
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              Observed releases
              Extent of observed surficial contamination
              Documentation of targets exposed to Level I or Level II contamination
              Factor values for which data are near scoring range boundaries.


STEP 7: ASSEMBLE AND SUBMIT COMPLETE MRS PACKAGE

       When assembling the MRS package, it may be helpful to prepare a working draft of the
documentation record, indicating raw data values and the references used to support specific MRS
factors. Use the working draft to enter information into PREscore (see High light 3-1), which will convert
the input data into factor, pathway, and site scores. More detailed information on the MRS scoring
package itself is provided in Section 3.2. The completed MRS package is submitted to the appropriate
EPA Regional office for review.

STEP 8: RESPOND TO REVIEWS

       The EPA Regional QC review process will identify potential problems with the MRS package. If
QC indicates that an  MRS score is inaccurate or that the documentation is incomplete, the scorer must
work with the Region to resolve any problems before the package is submitted to EPA Headquarters for
QA review. Only sites scoring at or above the cutoff of 28.50 are submitted for QA review. See Section
3.3 for more information on the MRS package review process.

3.2    THE MRS  SCORING  PACKAGE

       A complete MRS scoring package consists of the following materials  (in order):

       (1)     A site narrative summary
       (2)     A signed QC checklist (completed by Regional  reviewer)
       (3)     A QA signature page (completed by EPA Headquarters)
       (4)     MRS scoresheets (hard copy and disk; should be from PREscore)
       (5)     MRS documentation record, including bibliography of references
       (6)     Complete copies of referenced reports or documents, including legible maps (with
              scales) of sampling points and target locations
       (7)     NPL characteristics data collection form
       (8)     Other information as appropriate (e.g., RCRA documentation).

       This section focuses on the materials most important to the MRS scorer, the documentation
record and references. Refer to EPA's Regional Quality Control (QC) Guidance for NPL Candidate Sites
(OSWER Publication 9345.1-08, December 1991) for information on other materials listed above.

THE DOCUMENTATION RECORD

       The documentation record is the central element of the MRS package. It contains all of the
information upon which a site score is based and a list of the references from which the information was
obtained. The documentation record and references for sites proposed to the NPL are available for
public review. If a site's listing  is challenged in court, EPA's defense of the site score is restricted to the
information contained in the documentation record. To refute legal challenges, information in the MRS
documentation record must be objective, accurate, and complete.  Every statement of fact in the record
that is not a matter of general public knowledge should be supported by a reference number and a page
number. Although the use of professional judgment is acceptable where appropriate, the documentation
record should not contain assertions based strictly on opinion.

       As a general rule, MRS documentation should be sufficient for an independent observer to
replicate the observations, measurements, and calculations and arrive at the same quantitative or
qualitative decision (factor value). More specific guidance on the MRS documentation record includes:


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              All MRS factors that are scored must be documented in the documentation record.

              Adequate documentation of observed releases or observed contamination is extremely
              important. Be certain they are documented carefully and thoroughly.

              "Proof is not required for documenting a factor value. The MRS has been designed with
              wide scoring ranges for many factors, reflecting the uncertainties in SI data.

              An entry in the documentation record should include a reference to the supporting
              documents upon which the information is based (e.g., reports, well logs, geologic
              investigations). Always include the appropriate reference page number(s).

              Take particular care in documenting factor values upon which the  final site score is
              critically dependent. Successful challenges to these factor values  could prevent a site's
              placement on the NPL.

              Delete pages of the documentation record relating to MRS factors, pathways, and threats
              that have not been evaluated.

              Be as specific as possible given the available data. For example, do not indicate the
              MRS  range into which site information falls (e.g.,  nearest well is 1/4 mile to 1/2 mile from
              Source A) when more precise information (e.g., 1,500 feet) is available.

              When information is close to a "break point" in an MRS scoring range, estimate it as
              precisely as possible.

              Show all intermediate calculations in documenting hazardous waste quantities, blended
              target populations, and food chain production. Do not merely list the final values for
              these (and similar) factors.

              Remember that incomplete entries in the documentation record could form the basis of
              challenge to the scoring  during public comment; support all entries with sufficient
              references.

REFERENCES

       A complete list of references, including the number of pages in each, should be included at the
front of the documentation record. Number references sequentially in the order in which they are cited in
the documentation record, with the following exceptions:

              List the MRS as reference 1; and

              List the version of the Superfund Chemical Data Matrix (SCDM) used as reference 2.
              Highlight 3-2 provides more details on SCDM.

       Include a complete copy of most references cited in the documentation record (except
references 1 and 2, listed above) in the MRS scoring package. For unusually lengthy references, provide
only the appropriate excerpts and the title page. For any document that is not publicly available (e.g.,
those phone logs, PA/SI reports, consultant reports), include a complete copy, regardless of length. Maps
(e.g., those indicating sampling points, target locations) must be legible and include distance scales.
Chapter 3                                       28

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                                     HIGHLIGHT 3-2
                     THE SUPERFUND CHEMICAL DATA MATRIX

 SCDM contains data for more than 300 chemicals frequently found at Superfund sites. For each substance, SCDM
 provides selected HRS factor values (primarily for contaminant characteristics) and HRS benchmarks for each of
 the four pathways. MRS factor values listed include: toxicity, groundwater mobility, surface water persistence,
 human food chain and environmental bioaccumulation, ecosystem toxicity, air gas migration potential, and air
 mobility. Available benchmarks for all four pathways include toxicity-based benchmarks (e.g., cancer risk and
 reference dose screening concentrations) and regulation-based benchmarks (e.g., Maximum Contaminant Levels
 (MCLs) and Maximum Contaminant Level Goals (MCLGs) promulgated under the Safe Drinking Water Act). SCDM
 is essential for MRS scoring because benchmarks and MRS factor values are found more easily in SCDM than by
 consulting primary references.

 SCDM is published by EPA and is updated periodically.To obtain a copy of SCDM, contact the Hazardous Site
 Evaluation Division at EPA Headquarters.
       When referencing target measurements, describe where the measurement began (e.g., the
identified PPE), where the measurement ended (e.g., a specific sampling location), and how the
measurement was made (e.g., measured during the SI, or estimated from a map). This description
enables reviewers to repeat each step of the measurement and verify the supporting information in the
references.

       Whenever possible, ensure that references cited are primary sources; that is, the original
material from which the information was obtained. Examples of primary sources are:

              Geologic publications
              Records of field observations/measurements
              Analytical data reports
              Waste manifests
              Phone logs
              Field notebooks
              Contractor's reports.

Examples of references that can  be used but are not considered primary references are:

              Summaries of analytical results with the appropriate QA/QC information
              PA or SI reports.

       Examine very carefully the  use of PA and SI reports as references. In addition to actual field
observations or measurements and sampling results, these reports may contain summaries of
information gathered from other documents. Ensure that the documents referenced within the PA and SI
reports are reviewed and used as the primary references in the MRS documentation record.

OTHER ITEMS IN THE HRS SCORING PACKAGE

       Other items in the HRS package include:

              The HRS scoresheets, which list HRS factor values, pathway and threat scores, and the
              total site score.

              The site narrative summary, which is a brief description of the site including the site's
              name,  location, approximate size, general nature of contamination problem, and a
              description of current status of any response actions or enforcement actions.
                                             29                                      Chapter 3

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              The QC checklist which is filled out and signed by the Regional site assessment
              personnel responsible for performing QC review of MRS packages before submitting
              them to EPA Headquarters for formal QA.

              The NPL  characteristics data collection form, used to update an EPA data base of NPL
              sites.

              The QA signature page, which is signed by the EPA Headquarters Regional Coordinator
              and Site Assessment Branch Chief, indicating that all QA issues have been resolved and
              that the site is ready for proposal to the NPL.

       In some cases, other information is included in the HRS package. For example, when multiple
sources that are some distance apart or otherwise may appear unrelated are treated as a single site, a
statement of the rationale for doing so - a document sometimes referred to as an aggregation
memorandum- may be part of the HRS package. As another example, the package may include a
statement regarding the use of RCRA permits to document hazardous waste quantity.

3.3    THE PACKAGE REVIEW PROCESS

       All HRS scoring packages developed by states and EPA contractors are subject to QC review by
EPA Regional site assessment staff. EPA Headquarters will not review any package that has not
completed Regional QC and  is not accompanied by a signed  QC checklist. The purpose of the Regional
QC is to:

              Confirm the eligibility of a site for the NPL;

              Verify that the package is complete, information is accurate and readable, and every
              statement of fact is supported by documentation in the package;

              Check the arithmetic;

              Ensure that scores for individual HRS factors are appropriate, given the information
              contained in the package;

              Review key assumptions and professional judgments made in scoring the site and
              ensure that they are adequately explained and documented;

              Resolve and correct any errors or discrepancies; and

              Review the site narrative summary and NPL characteristics data collection form to
              ensure that they are adequate.

For more information on the QC process, refer to EPA's Regional Quality Control (QC) Guidance for NPL
Candidate Sites (OSWER Publication 9345.1-08, December 1991).

       After Regional QC is complete, packages undergo an  in-depth QA review at EPA Headquarters.
Analysis of HRS scoring packages submitted to Headquarters in the past shows a high incidence of
incorrect referencing and  illegible photocopies,  especially of maps. Avoiding these common errors will
streamline the review process considerably.

       After any scoring  errors or issues are resolved, EPA may propose adding  sites scoring greater
than 28.50 to the NPL through a proposed rulemaking in theFectera/ Register. Comments received
during the ensuing public comment  period are reviewed and addressed, and site scores modified as
necessary. In some cases, site scores may drop below 28.50.  A final rule is then published in theFectera/
Register identifying the sites added  to the NPL (i.e., sites with  scores remaining above 28.50 and
remaining eligible under EPA's policy).


Chapter 3                                     30

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3.4   MRS SCORING STRATEGY

       This section discusses a strategy for efficient MRS scoring. Guidelines are presented for
determining the extent of scoring effort and the number of pathways to score. In addition, this section
discusses the implications of the MRS equations for site scoring and provides several scoring principles
that will help in preparing MRS packages.

       The MRS evaluates hazards to human health and the environment on the basis of a large
number of individual factors. For most sites, it is neither feasible nor productive to gather data for and
score every factor in every pathway, because:

               One of the primary objectives of MRS scoring is to determine whether or not the site
               score is greater than 28.50 (i.e., cutoff score for NPL listing).

               Many sites pose threats  primarily via one or two pathways.

               The mathematics of the  MRS is such that higher-scoring pathways exert a
               proportionately greater influence on the site score than do lower-scoring pathways.

       Without a clearly defined scoring strategy, considerable resources may be expended gathering
data and  scoring factors and pathways that will have little  impact on the site score.

SCORING EFFORT

       Scoring a site with the MRS involves various types of decisions. Quantitative decisions may
include determining the correct scoring ranges for waste characteristics and targets. Qualitative decisions
may include deciding which pathways, threats, aquifers, and watersheds to evaluate, and whether
existing sampling results are sufficient to document an observed release or observed contamination.
One of the most important decisions is determining  when the data collection and scoring effort is
complete.

       The level of effort devoted to scoring a site  is governed by two competing requirements: (1) to
accurately determine the relative threat posed by the site, and  (2) to efficiently use EPA's limited data
collection and analysis resources. The MRS includes  numerous factors that must be evaluated for each
pathway scored, and comprehensive data are rarely readily available for every factor. Moreover, some
factor evaluations are more resource-intensive than others. At  most sites, it would be possible to refine
factor values by gathering or analyzing additional data (e.g., take one more sample,  count one more
house), but such efforts may consume resources better devoted to other sites. It is important to have a
strategy for accurately and efficiently scoring a site. The following general principles should help
determine the extent of scoring effort:

               The MRS score should reliably reflect the  site's eligibility for the NPL. If the site score is
               greater than or equal to  28.50, the scorer should be confident that the score will remain
               at or above 28.50 after QA/QC review and public comment. If the site score is less than
               28.50, the scorer should be confident that additional scoring efforts would not raise the
               score to 28.50 or greater.

               To the extent practicable, the MRS score should reflect the relative threat posed by the
               site.

       In developing a scoring strategy, the scorer must realize that the MRS is a screening tool, not
a detailed risk assessment.  Given the considerable uncertainties regarding specific characteristics of
a site and its surrounding environment at the time of scoring, the MRS score should not be viewed as
a measure of absolute risk that must be determined to the last  decimal point. Moreover, qualitative
information regarding specific site characteristics may be as important as the numerical MRS score in
determining some aspects of relative threat. For example, the immediate threat a site poses as a


                                              31                                        Chapters

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result of a few drinking water wells contaminated above health-based benchmarks would be greater than
the immediate threat posed by a site at which nearby municipal wells were threatened with contamination
(but not currently contaminated), even if the two sites received similar MRS scores.

IMPLICATIONS OF MRS EQUATIONS FOR SITE SCORING

       Understanding the mathematical dynamics of the MRS requires familiarity with (1) the way in
which the site score is determined from pathway scores and (2) the way in which pathway scores are
determined from factor category values.

Dynamics of the MRS Site Score

       The MRS site score (S) is calculated by a root-mean-square formula:
                                           0   0  0   *>
                                          S  +S +S +S
                                           gw  sw  s   a
where:   Sgw = ground water migration pathway score
         Ssw = surface water migration pathway score
         Ss  = soil exposure pathway score
         Sa  = air migration pathway score.

       Each pathway score has a minimum value of 0 and a maximum value of 100. The mathematics
of the root-mean-square equation is such that higher-scoring pathways exert a proportionately greater
influence on the site score than lower-scoring pathways. For example,
       In the root-mean-square equation, the sum of the squared pathway scores is the key to reaching
the cutoff score:
The value of 3,249 can be reached in a variety of ways, as shown by the examples \r\Highlight3-3.
Chapter 3                                      32

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COME
HIGHLIGHT 3-3
3INATIONS OF PATHWAY SCORES THAT YIELD SITE SCORE OF 28.50
Individual Pathway Scores
57.00
40.31
32.91
28.50
0.00
40.31
32.91
28.50
0.00
0.00
32.91
28.50
Sum of Squared
Pathway Scores
3,249
3,250
3,249
3,249
Site Score
28.50
28.50
28.50
28.50


       The root-me an-square equation ar\dHighlight3-3 illustrate that it is easier to raise a site score
by adding points to a high-scoring pathway than by adding the same number of points to a second,
lower-scoring pathway. Given an existing single-pathway score (A) less than 57, the additional score
required for the same pathway to reach a site score of 28.50 is:

                                             57-A

whereas the score required for a second pathway is given by:
                                          3,249 -A'
       For example, suppose a preliminary scoring effort resulted in a single-pathway score of 50.
Within that same pathway, only (57-50)=7 additional points would be required for a site score of 28.50,
while in a different pathway, (3,249-2,500)=27.37 points would be required High light 3-4 presents the
general relationship between additional points required within the same pathway versus a second
pathway.

       Several general conclusions can  be reached from the dynamics of the algorithm used to derive
the MRS site score:

               Knowing the two highest pathway scores usually is sufficient to determine whether the
               site score is likely to be above 28.50.

               The site score is unlikely  to be above 28.50 unless one pathway score is greater than 50,
               two pathway scores are greater than 35, or three pathway scores are greater than 30.

               Pathways that receive a score lower than 10 points are unlikely to have a significant
               effect on the site score in the range of the cutoff score or above (e.g.,  a single-pathway
               score of 50 would result in a site score of 25.00; pathway scores of 50 and 10 would
               result in a site score of 25.50).
                                              33
                                                                                       Chapter 3

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                                   HIGHLIGHT 3-4
     ADDITIONAL SCORE REQUIRED TO YIELD SITE SCORE OF 28.50
       a
       ffi
                         10        20        30        40

                                EXISTING SINGLE PATHWAY SCORE
Dynamics of the MRS Pathway Scores

       Each MRS pathway score (A) is the product of the three factor category values (likelihood of
release or likelihood of exposure, waste characteristics, and targets) divided by a scaling factor:
                                      A =
                            LJR
                                                  x T
                                             82,500
where: LR
       WC
       T
= likelihood of release
= waste characteristic
= targets factor.
       The scaling factor of 82,500 results in a pathway score of 100 when the values for likelihood of
release (or likelihood of exposure) and waste characteristics are at their "typical" maxima and the targets
factor category value is 150 (i.e., (550 x 100 x 150)782,500 = 100). However, several characteristics of
the MRS scoring algorithms make it difficult to determine a priori for a specific site which factor category
or individual factor has the greatest influence on pathway score:

              The multiplicative nature of the factor categories, which means, for example, that
              doubling any one factor category value will double the  pathway score, is subject to
              certain maximum values (i.e., "caps").

              The hazardous substance  used to determine toxicity and other waste characteristics
              factor values may vary among pathways and threats.
Chapter 3
                                            34

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               Caps on the waste characteristics factor category value vary among pathways and
               threats.

               The maximum pathway score based solely on environmental threat is 60.

               The targets factor category has no cap.

               The point value assigned to specific targets depends on whether they are subject to
               actual contamination.

       If the values for likelihood of release and waste characteristics are known (or have been
approximated) for a pathway, the targets factor category value required to obtain a particular pathway
score (A) is:


                                        7= 82,500 x A
                                             £J?x  WC

       For example, if likelihood of release is 550, waste characteristics is 32, and the pathway score
required for a site score of 28.50  is 47.5, the minimum targets factor category value necessary for this
score is (82,500 x47.5)/(550 x32) = 222.66. Assuming maximum values for likelihood of release and
waste characteristics the minimum targets factor values  required for a pathway score of 57 (and hence a
single-pathway site score of 28.50) are presented \r\Highlight3-5. Note that the targets factor category
value includes Level I, Level II, and potential contamination values; values for nearest well, intake, or
residence; and values for wellhead protection areas, workers, resources, sensitive environments, and
other targets factors. The relative weight given each of these targets factors determines the overall
contribution of a single target to the pathway and site score. For example, individuals and sensitive
environments evaluated  under Level I or Level II contamination are weighted, respectively, a minimum
of 100 and  10 times more heavily than those evaluated under potential contamination.

       A high pathway score generally requires relatively high values for all three factor categories, and
with a few exceptions (e.g., when the targets category value, which is not capped, is very high)  a low
value for any single factor category will limit the pathway score. This results partly from the multiplicative
relationship between the three factor category values in the pathway score  equation, and partly from how
the  values for each factor category are assigned in the MRS. For example, minimal waste quantity and a
moderate or low likelihood  of release are likely to result in a low pathway score unless a very high targets
value is obtained. A high targets value could be difficult to obtain in this scenario because all targets
would be evaluated under potential contamination.

PATHWAY CONSIDERATIONS

       Certain combinations of site  characteristics usually result in a high pathway score. The following
generalizations may help identify potentially high-scoring pathways:

               Pathways with actual contamination of targets are  likely to score higher than pathways in
               which  only potential  contamination is established. Therefore,  consider scoring all
               pathways with actual contamination of targets.

               The decrease in target values due to distance-weighting of targets subject to potential
               contamination is less in the ground water pathway than in the air and soil pathways (see
               Highlight 3-6).

               The surface water pathway is likely to receive a relatively high score if an observed
               release to a fishery or sensitive environment is established.
                                              35                                        Chapter 3

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HIGHLIGHT 3-5
MINIMUM TARGETS FACTOR VALUE REQUIRED TO YIELD
PATHWAY SCORE OF 57

Pathway or Threat
Ground Water
Surface Water
Drinking Water
Human Food Chain
Environmental"
Soil Exposure
Resident
Nearby Population0
Air
Maximum
Likelihood of
Release
Factor
550
550
550
550
550
500
550
Maximum
Waste
Characteristics
Factor Category
100
100
1,000
1,000
100
100
100
Minimum Targets
Factor Category
Value for
Pathway Score of
85.5
85.5
8.55
8.55
85.5
94.05
85.5
a Assumes maximum value for likelihood of release and waste characteristics; required
targets factor value increases as values for likelihood of release and/or waste
characteristics decrease
bMaximum Score for the environment threat is 60.
CA targets factor category value as high as 94.05 is unlikely for this threat.

             In the surface water pathway, the maximum value for waste characteristics is 1,000 in the
             human  food chain and environmental threats. A waste characteristics value greater than
             100 means the pathway can score > 57 with lower values for the likelihood of release and
             targets  factor categories (see High light 3-5).

             If the likelihood of release and waste characteristics factor values are maximum, a
             pathway or threat score of 57 or greater may result when actual contamination is
             established for between 4 and 41 persons (seeHighlight3-7).

      Several other generalizations for pathway scoring are presented below. For specific pathway and
factor scoring strategies, see the appropriate chapters of this document.

Ground Water Pathway

      The ground water pathway may receive a score of 57 or greater based on actual or potential
contamination if target populations are sufficiently large.

             Score the ground water pathway if any targets are evaluated under actual contamination
             (Level I or II concentrations).

             Score the pathway if there is a large population within the TDL, even if all targets are
             evaluated under potential contamination.

             The nearest well  factor may have a significant effect on the pathway score.

             A large distance-weighted population is most likely when a large number of private wells
             are within 1/2 mile of the site, municipal wells are within the TDL, and/or a karst aquifer is
             within the TDL.
Chapter 3
                                              36

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HIGHLIGHT 3-6
DISTANCE AND DILUTION WEIGHTS UNDER POTENTIAL CONTAMINATION












Distance
Category3

Onsite
>0.00- 0.25
> 0.25 -0.50
> 0.50 -1.00
> 1.00-2.00
> 2.00 -3.00
> 3.00 -4.00
Relative Distance Weight
Assigned to Population Targets
Evaluated Under Potential Contamination
Ground Water
Pathway b
1.00
1.00
0.62
0.32
0.18
0.13
0.08
Air Pathway
1.000
0.250
0.054
0.016
0.005
0.002
0.001
Soil Exposure
Pathway c
1.000
0.025
0.013
0.006
0
0
0











a Distance from source (miles).
b For karst aquifers, relative weight is 0.50 beyond 0.5 mile.
c Nearby population threat only.
                                    HIGHLIGHTS-?
           POPULATION REQUIRED TO YIELD PATHWAY SCORE OF 57
Number of Persons Evaluated Under Actual Contamination

Level I
4
3
2
1
0

Level II
0
6
16
26
41
Pathway or
Threat
Score3'"
60.00
57.33
57.33
57.33
57.33
       a Pathway or threat score based solely on population evaluated under actual contamination (e.g., no
 resources, no sensitive environments).
       b Ground water pathway, surface water pathway (drinking water threat), soil exposure pathway
 (resident population threat), and air pathway.
Surface Water Pathway

     The surface water pathway score is the sum of the three separate scores for the drinking water,
human food chain, and environmental threats. Any threat may score 57 or greater if actual contamination
of targets is established; if actual contamination is established for either the human food chain or
environmental threat, the surface water pathway is very likely to score 57 or greater.

            Score the surface water pathway if any targets are evaluated under actual contamination
            (Level I or II  concentrations).
                                             37
                                                                                     Chapter 3

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             Score the surface water pathway if there is an observed release to surface water and a
             fishery is present within the TDL, even If the fishery is not subject to actual contamination.

             If an observed release to surface water is not established, an individual threat is unlikely to
             score  greater than 10 points unless many targets (or a large fishery) are present within a
             surface water body with a dilution weight of 0.01 or greater (for a list of such surface water
             body types, see MRS Table 4-13); however, the sum of the three threats may exceed 10.

             Within the surface water pathway, threat scores are additive (i.e., they are not combined
             using  a root-mean-square equation), and therefore an individual threat score lower than 10
             may contribute significantly to the pathway score.

             At many sites, several types of surface water bodies are located within the TDL.; therefore,
             targets within all surface water body types must be considered in developing a scoring
             strategy.
Drinking Water Threat
             A large dilution-weighted population is most likely when a municipal intake is located on a
             stream or river with low or moderate flow characteristics. The low dilution weight for large
             surface water bodies often will result in a low threat score, even when population served is
             large (for examples, see Highlight 3-8).

             When evaluated based on potential contamination, the nearest intake factor generally will
             not have a significant effect on the drinking water threat score unless the intake is located
             within a minimal stream.
Human Food Chain Threat
             The human food chain threat score is likely to be 57 or greater if actual contamination of a
             fishery is established. If actual contamination is established and the waste characteristics
             value is 180 or greater, the human food chain threat score will almost always be 57 or
             greater.

             Even if actual contamination of a fishery is  not established, the human food chain threat
             score is likely to be significant if there is an observed release to the watershed and the
             waste characteristics value is 100 or greater.

             If no observed release is established, the human food chain threat score is unlikely to be
             significant unless there is a fishery within a minimal or small to moderate stream and the
             waste characteristics value is greater than 320.
Environmental Threat
             The environmental threat score is likely to be 57 or greater if Level I concentrations are
             established for a sensitive environment with a point value of 25 or greater. If actual
             contamination is established for at least one sensitive environment and the waste
             characteristics value is 320  or greater, the environmental threat score will almost always
             be 57 or greater.
Chapter 3                                       38

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HIGHLIGHT 3-8






DRINKING WATER THREAT SCORES UNDER POTENTIAL CONTAMINATION
Type of Surface Water Bodyb
Rivers and Streams
Minimal stream
Small to moderate stream
Moderate to large stream
Large stream to river
Large river
Very large river
3-mile mixing zone in quiet
flowing river
Other Surface Water Bodies0
Shallow ocean/Great Lake
Moderate depth/Great Lake
Deep zone/Great Lake
Drinking Water Threat Score for Intake with Given
Population Served3
2,500

98.79
9.70
1.21
0.12
0.01
0.0
49.70

0.01
0.0
0.0
7,500

100.00
31.52
3.03
0.30
0.03
0.0
100.00

0.03
0.0
0.0
25,000

100.00
98.79
9.70
1.21
0.12
0.01
100.00

0.12
0.01
0.0
75,000

100.00
100.00
31.52
3.03
0.30
0.03
100.00

0.30
0.03
0.02
250,000

100.00
100.00
98.79
9.70
1.21
0.12
100.00

1.21
0.12
0.06






3 Assumes likelihood of release value of 500, waste characteristics value of 100, and no other
drinking water intakes within the TDL.
b For definitions, see MRS Table 4-1 3.
c Assumes no drinking water intakes in salt or brackish water; for other lakes, see MRS section
41231


               If actual contamination of a sensitive environment cannot be established, the
               environmental threat score is unlikely to be significant unless there are several sensitive
               environments within a minimal or small to moderate stream and the waste
               characteristics value is greater than 100.

               The maximum score for the environmental threat is 60.

Soil Exposure  Pathway

               The soil exposure pathway score is derived by combining separate scores for the
resident population and nearby population threats.  The soil exposure pathway is only evaluated when
areas of observed (surficial) contamination are documented. The area of observed contamination is an
important determinant of waste characteristics in the resident population threat and of likelihood of
exposure and waste characteristics in the nearby population threat.

               Score the soil exposure pathway if  any targets are within 200 feet  of an area of observed
               contamination.

               The soil exposure pathway usually  will not score 57 or greater unless residents, students
               (including day care), workers, or sensitive environments are on or within 200 feet of an
               area of observed contamination on  the property.

               The nearby population threat is unlikely to contribute significantly to the soil exposure
               pathway score unless there is a very large population near the site and areas of
               observed  contamination at the site  are readily accessible.
                                              39
                                                                                        Chapter 3

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               Within the soil exposure pathway, threat scores are additive (i.e., they are not combined
               using a root-mean square equation), and therefore an individual threat score lower than
               10 may contribute significantly to the pathway score.

               The maximum soil exposure pathway score that can be achieved when the only targets
               are terrestrial sensitive environments is 60.

       Resident Population Threat

               Evaluating a relatively small number of resident threat targets may result in a significant
               pathway score. For example, if the waste characteristics value is 32, documenting one
               resident and one 50-point sensitive environment both subject to Level II concentrations
               plus one worker would result in a pathway score of 21.55 (based solely on resident
               population threat).

       Nearby Population Threat

               The nearby population threat score is likely to be significant by itself only if there is a
               large population very near the  site and likelihood of exposure and waste characteristics
               are moderate to high.

Air Pathway

       The air pathway may score 57 or greater based on actual or potential contamination. However, if
all targets are evaluated under potential contamination, the pathway score is likely to be lower than 10
unless at least some targets are on or very near sources.

               Score the air pathway if any targets are evaluated under actual contamination (Level I or
               II concentrations).

               Score the pathway if there are  any targets on or within 1/4 mile of sources at the site,
               even if all targets are evaluated under potential contamination.

               The relative value assigned to  targets evaluated under potential contamination declines
               steeply with distance  (seeHighlight 3-6). Therefore, the targets factor category value
               generally will be determined primarily by targets on or within 1/4 mile of a source.

               The maximum air pathway score that can be achieved when the only targets are
               sensitive environments is 60.
Chapter 3                                       40

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CHAPTER 4
SOURCES
   Contaminated
   So
                 Surface
                 Impoundment

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SECTION 4.1
CHARACTERIZATION
OF SOURCES AND
AREAS OF OBSERVED
CONTAMINATION
      This section provides guidance to assist the scorer in characterizing sources and areas of
observed contamination by assigning factor values based on source type. Because source information is
used throughout the MRS and deficiencies in that information or in its interpretation may have a
significant impact on the site score, it is critical to correctly classify and characterize each source. This
section defines sources (and  areas of observed contamination), provides pathway-specific guidance for
identifying and documenting sources and their hazardous substances, and discusses special cases where
characterizing sources (or areas of observed contamination) is especially complex. This section does not
discuss multiple-source sites.
                             RELEVANT MRS SECTIONS

       Section 2.1.3               Common evaluations
       Section 2.2                 Characterize sources
       Section 2.2.1               Identify sources
       Section 2.2.2               Identify hazardous substances associated with a source
       Section 2.2.3               Identify hazardous substances available to a pathway
       Section 5.0.1               General considerations (soil exposure)
DEFINITIONS
      Area of Observed Contamination:  Evaluated only in the soil exposure pathway and
      established based on sampling locations as follows:

             Generally, for contaminated soil, consider the sampling locations that indicate observed
             contamination and the area lying between such locations to be an area of observed
             contamination, unless information indicates otherwise.

             For sources other than contaminated soil, if any sample taken from the source indicates
             observed contamination, consider the entire source to be an area of observed
             contamination.

      If an area of observed contamination (or a portion of such an area) is covered by a permanent,
      or otherwise maintained, essentially impenetrable material (e.g., asphalt), exclude the covered
      area from the area of observed contamination. However, asphalt or other impenetrable materials
      contaminated by site-related hazardous substances may be considered areas of observed
      contamination.

      Hazardous Substances:  CERCLA hazardous substances and pollutants or contaminants as
      defined in CERCLA sections 101 (14) and 101 (33), except as otherwise specifically noted in the
      MRS.
                                        41                                 Section 4.1

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       Source:  Any area where a hazardous substance has been deposited, stored, disposed, or
       placed, plus those soils that may have become contaminated from hazardous substance
       migration. In general, however, the volumes of air, ground water, surface water, and surface
       water sediments that may have become contaminated through migration are not considered
       sources.

       Unallocated Source:  Not an MRS source type, rather a means of including within the
       hazardous waste quantity factor those hazardous substances or hazardous waste streams that
       are known to be at the site but that cannot be allocated to any specific source. Thus, the term
       only applies for hazardous waste quantity.

The following  definitions are for specific source types evaluated in the MRS.

       Above-ground Tank:  Any tank that does not meet the definition of a below-ground tank
       (including any tank that is only partially below the surface).

       Active Fire Area: Area presently burning or smoldering.

       Below-ground Tank:  A tank with its entire surface area below the surface and not visible;
       however, a fraction of its associated piping may be above the surface.

       Buried/Backfilled Surface Impoundment:  A surface impoundment that has been completely
       covered with soil or other cover material after the  final deposition of waste  materials.

       Burn  Pit: An uncovered area on the land surface that is not presently burning but that was at
       one time  used to burn hazardous substances or was otherwise significantly inflamed.

       Container or Tank:  A stationary device constructed primarily of nonearthen materials (such as
       wood, concrete, steel, or plastic) used to contain an accumulation of a hazardous substance; or a
       portable device in which a hazardous substance is stored or otherwise handled.

       Contaminated Soil  (excluding land treatment):  Soil onto which available evidence indicates
       a hazardous substance was spilled, spread, disposed, or deposited.

       Drum: A type of container used to hold hazardous substances. For MRS purposes, drums are
       standard 55-gallon cylindrical containers.

       Landfarm/Land Treatment: A method of waste management in which either liquid wastes or
       sludges are spread over land and tilled or liquids  are injected at shallow depths into soils.

       Landfill:  An engineered (by excavation or construction) or natural hole  in  the ground into which
       wastes have been disposed of by backfilling or by contemporaneous deposition of soil and
       wastes.

       Other: A source type used when defined source types do not apply. Examples include:
       contaminated buildings, storm drains, dry wells, injection wells, and French drains. "Other" also
       can be used for ground water plumes and sediments with no identified source.
       Piles:
              Chemical Waste Pile: A pile consisting primarily of discarded chemical products
              (whether marketable or not), by-products, radioactive wastes, or used or unused
              feedstocks.
Section 4.1                                      42

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              Other:  A term reserved for a pile of indeterminate origin that contains hazardous
              substances.

              Scrap Metal or Junk Pile:  A pile consisting primarily of scrap metal or discarded
              durable goods such as appliances,  automobiles, auto parts, or batteries, that contain or
              have contained hazardous substances.

              Tailings Pile:  A pile consisting primarily of any combination of overburden from a
              mining operation and tailings from a mineral mining, beneficiation, or processing
              operation.

              Trash Pile: A pile consisting primarily of paper, garbage, or discarded nondurable
              goods that contain or have contained  hazardous substances.

       Surface Impoundment: A topographic depression, excavation, or diked area, primarily formed
       from earthen materials (lined or unlined) and designed to hold accumulated liquid wastes, wastes
       containing free liquids, or sludges that were not backfilled or otherwise covered during periods of
       deposition; depression may be dry if deposited liquid has evaporated, volatilized or leached;
       structures that may be more specifically described as lagoon, pond, aeration pit, settling pond,
       tailings pond, sludge pit, etc.; also a surface impoundment that has been covered with soil after
       the final deposition of waste materials (i.e.,  buried or backfilled).

EVALUATING SOURCES

       Evaluating sources consists of five steps: (1)  identifying the sources and areas of observed
contamination, (2) classifying the source type, (3) identifying the hazardous substances associated with
each source or area of observed contamination, (4) evaluating the containment associated with each
source, and (5) calculating the hazardous waste quantity for each source. A complete source
characterization should include:

              Narrative summary describing the source or area of observed contamination;

              Reference location for the source or area of observed contamination on the site map;

              List of hazardous substances associated with the source or area of observed
              contamination;

              Containment description; and

              Hazardous waste quantity evaluation.

       This section outlines the general strategy for evaluating sources. The order in which topics are
discussed here does not imply that any one action is always taken before another. At some sites, the
source may be identified and the evaluation will include identifying hazardous substances present in the
source and the containment for that source; at others, the hazardous substances may be found  in a
media and then traced to sources.

(1)     Identify sources and areas of observed contamination. Locate all sources and areas of
       observed contamination at the site.  For sources readily seen, the scorer can move directly to
       Step (2). Sources not readily seen can  be identified by several methods including (but not limited
       to):

              Visual observation of geographic or other site features followed  by sampling
              Site records indicating  historical disposal areas
              Discovery during the SI
                                              43                                      Section 4.1

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               Aerial photographs showing historical evidence of a source
               Statements by individuals who have knowledge of the site.

       Another method to identify sources is through the presence of hazardous substances. In this
       method, first identify hazardous substances through sampling and then define the source based
       on the sampling location or trace back from the sampling location to identify the source of the
       migration. This process may become complicated at sites with more than one source or
       hazardous substance.

(2)     Classify source type. After identifying sources at the site, classify each source in one of the
       MRS source type categories identified for that pathway. If the source classification is unclear,
       consult Highlight 4-1  and the subsection below, Characterizing Unique Sources.

(3)     Identify hazardous substances associated with sources. After identifying and classifying the
       sources at a site, the next step in the characterization process is identifying the hazardous
       substances associated with each source. The basic methods for identifying hazardous
       substances associated with a source include:

               Labels, manifests, or other historical records;

               Site operations (e.g., if a plating facility uses trichloroethylene and disposes sludge into a
               surface impoundment, the scorer could assume trichloroethylene was  present in the
               surface impoundment); and

               Sampling.
                                          HIGHLIGHT 4-1
                            COMMONLY CONFUSED SOURCE TYPES

 At times, it Is difficult to categorize a source at a facility as one particular MRS source. In some cases, the scorer
 must use professional judgment and knowledge of the waste management practices at the site to assign a source
 type. The following can help the scorer differentiate commonly confused source types.

 Landfill:  Landfills are generally characterized by the addition of fill (e.g., soil) during or after disposal, covering the
 wastes from view. Often, landfills are dug out In the ground and then the soil from the resulting pit is used as fill
 during disposal. Sometimes, open pits (e.g., old quarries) are used and soil is brought in as cover.

 Pile: Piles are characterized by periodic addition of wastes to stacks resulting in one large pile. Piles may occur in
 a pit, liquid impoundment, or on the land surface. Piles differ from landfills  because the wastes generally are not
 mixed with fill during disposal. Piles in liquid impoundments differ from surface impoundments because the wastes
 (e.g., often slurries) are deposited with the intention of dewatering the waste and accumulating a large pile of wastes
 in  one area.

 Surface Impoundment: Surface impoundments are distinguished by two characteristics -the waste management
 unit is intended to contain liquid wastes and lacks a soil cover. If the liquid has evaporated, the waste management
 unit should still be considered a surface Impoundment for MRS purposes. A buried/backfilled surface Impoundment
 is  similar to a surface impoundment, only this source type has been filled with soil or other cover material after the
 final deposition of wastes.

 Contaminated Soil:  Contaminated soil  can be distinguished by the method of deposition. Unlike other sources,
 contaminated soil is not intended to be a waste management unit  and is often formed by migration, deposition, or
 spills of wastes.
Section 4.1                                        44

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       However, consider these important points before associating hazardous substances with a
       source:

              An observed release to the migration pathways can be shown by sampling or by direct
              observation (e.g., if sampling finds hazardous substances in a ground water plume
              associated with a landfill, the hazardous substances can be associated with the landfill).

              Transformation products from a hazardous substance associated with a source can be
              scored only if sampling indicates they are present.

              Comparison to background is not necessary to establish the presence of hazardous
              substances for sources confirmed by manifests (e.g., RCRA, DOT).

              Visual observation of stained soils may be a clue to the presence of hazardous
              substances, but their presence must be verified through sampling or other means.

              There are significant differences between the three migration pathways (ground water,
       surface water, and air) and the soil exposure pathway for associating hazardous substances with
       sources. The differences are highlighted below.

       For the migration pathways:

              Consider those hazardous substances documented to be present in a source or known to
              be deposited in that source (e.g.,  by sampling, labels, manifests, oral or written
              statements) or in releases from the source to be associated with that source when
              evaluating each pathway.

              When a hazardous substance can be determined to be present at a site (e.g., by labels,
              manifests, oral or written statements, observed release), but the specific source cannot
              be documented, consider the hazardous substance to be present at all the sources,
              except those for which definitive information indicates that the hazardous substance was
              not or could not be present.

       For the soil exposure  pathway:

              Consider only the hazardous substances that  meet the criteria for observed
              contamination for an area of observed contamination to be present  in that area of
              observed contamination.

(4)     Evaluate the containment for each  source. Only hazardous substances associated with a
       source with a containment greater than zero or with an area of observed contamination are
       available to the pathway under consideration. Acceptable means of documenting hazardous
       substances available to the migration pathways and the soil exposure pathway are listed below.

              For the migration  pathways, the hazardous substances (including any transformation
              products)  available to a particular pathway are those that:

              —     Meet the criteria for an observed release to the pathway under consideration; or

              —     Are associated with a source with a containment factor greater than zero for the
                     pathway under consideration (see Sections 7.4 and 8.5).
                                             45                                      Section 4.1

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              For the soil exposure pathway, the hazardous substances available are those that:

              —     Meet the criteria for observed contamination at the site; or

              —     Meet the criteria for observed contamination at areas with an
                     attractiveness/accessibility factor greater than zero, for the nearby population
                     threat (see Section 9.8).

(5)     Calculate hazardous waste quantity. After identifying the sources and determining the
       hazardous substances available to each pathway, calculate the hazardous waste quantity. For
       guidance on calculating  the hazardous waste quantity, see Chapters of this document.

EVALUATING SITES WITH NO IDENTIFIED SOURCES

       Occasionally, sites that consist of a plume of contaminated ground water or an area of surface
water sediment contamination, with the original source of the contamination unidentified, enter the
Superfund process. Before scoring such sites, efforts should be undertaken to identify the original
source(s) of contamination. These efforts should be equivalent to those of an expanded SI and should
include:

              Research on site history and regulatory status;

              Site reconnaissance;

              Consideration of hazardous substances affiliated with industries of potential concern at
              the  site;

              Records search  and  interviews with employees; and

              Sampling to eliminate or confirm other possible sources.

A source should generally not be designated as "unidentified" until sampling has been undertaken in an
area and a search for the original sources  has been conducted (within the scope of an expanded SI).

       If the original source(s) of contamination cannot be identified, evaluate the ground water plume
or the sediment contamination as the source for scoring purposes. In order for a ground water plume or
sediment contamination to be characterized as a source, generally consider the following:

              The plume or sediment contamination has been established solely by sampling and
              inference, using the observed release criteria; and

              The level of effort to identify the original source is similar to an expanded SI.

CHARACTERIZING UNIQUE SOURCES

       Some sources do not easily fit into MRS source types. These sources should be evaluated on a
case-by-case  basis. The unique sources described below do not comprise a complete list.

NATURAL PONDS

       A natural pond used as a surface impoundment into which one or more hazardous substances
were deposited can be considered a source in some circumstances. The following criteria provide
guidelines for determining if a natural pond may be considered a source:


Section 4.1                                     46

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               The pond is an isolated water body (or has been modified so as to be an isolated water
               body).

               The entire pond is intended to be used as a waste management area.

               The hazardous substances in the pond result from deposition, as opposed to migration
               (see definition of source).

       When a natural pond meets all of the above criteria, it may be considered a source and the
assigned source type is usually surface impoundment. Water bodies such as rivers, oceans, or the Great
Lakes should generally not be considered sources Highlight 4-2 shows two ponds, one that would be
considered a source and another that would not.
                                       HIGHLIGHT 4-2
               WHEN TO CONSIDER NATURAL  PONDS AS SOURCES
   In this highlight, two ponds containing hazardous substances are shown.  Pond 1 could be considered a
   source for HRS purposes.  Pond 2, however, could not be considered a source, but rather is a contaminated
   surface water body in the surface water pathway. The reasons for this distinction are as follows:

   •       Pond 1 is essentially a closed system. Wastes in Pond 2 have the potential to migrate because the
          pond flows into a stream,

   •       The entire Pond 1 is intended for waste management as shown by the outfall pipes. No wastes are
          directly deposited into Pond 2.

   «       Wastes were deposited in Pond 1.  Wastes migrated from the adjacent waste pile into  Pond 2.

   «       Most importantly, Pond 1, although initially naturally occurring, was modified to manage wastes; Pond
          2 was not.
                                               47
                                                                                        Section 4.1

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INJECTION WELLS

       Any documentation of direct deposition of a material that contains one or more hazardous
substances into an injection well identifies it as a source. Such documentation can include (but is not
limited to) manifests, permits, employee interviews, and sworn testimony. Injection wells are considered
source type "other" for scoring purposes.

CONTAMINATED SEEPS AND LEACHATES

       Because contaminated seeps and leachates arise from migration rather than from deposition,
they should not be considered sources for the migration pathway. However, soils contaminated by seeps
and leachates can be considered areas of observed contamination for the soil exposure pathway. If soil
samples show observed contamination within two feet of the surface, consider the  surface soil delineated
by these samples to be an area of observed contamination.

WALLS OR OTHER PARTS OF BUILDINGS CONTAINING HAZARDOUS SUBSTANCES

       Walls or other parts of buildings can be considered sources subject to the  restrictions in CERCLA
concerning what constitutes a release (i.e., CERCLA section 101 (22), definition of release). Generally,
the contamination of the building must be the result of activities within the building. The assigned source
type is "other."

TIPS AND  REMINDERS

       Sources must contain hazardous substances.

       Contaminated soil is considered a source for all three migration pathways, even if the soils
       have become contaminated by hazardous substance migration from another source type.

       Contaminated bayous are generally not considered surface impoundments; however, the
       contaminated sediments in a bayou may be classified as source type "other" if no other
       sources can be identified.

       Discuss qualitatively alleged or possible sources in the documentation record; however, only
       sources that can be described and documented should be used  in scoring.

       Evaluate the documentation, other than sampling data, for sources with attention to the
       original purpose of the information. For instance, a letter giving permission for disposal of a
       hazardous substance in a landfill is generally not sufficient by itself to document that the
       substance was deposited.

       Manifests indicating deposition of hazardous substances are acceptable evidence of the
       presence of those hazardous substances in a source.

       Do not  confuse "unidentified source" and "unallocated source." The unidentified source is
       used as a source type for ground water plumes or contaminated sediments when the original
       source  of the contamination is unknown. The unallocated source is not actually a  source, but
       rather is a means of evaluating hazardous waste quantity at sites where hazardous
       substances cannot be allocated to specific sources.
Section 4.1                                      48

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SECTION 4.2
OVERVIEW OF
SITES  WITH
MULTIPLE
SOURCES
       The purpose of this section is to assist the scorer in deciding when to treat multiple areas
containing hazardous substances as one source and when to treat these areas separately. This section
defines multiple-source sites, orients the scorer to factor-specific considerations for MRS scoring, lists
criteria necessary for source aggregation, and helps the scorer develop effective scoring strategies. If
sources are similar in type and have similar target populations, the scorer should consider aggregating
them into one source. Decisions to aggregate sources should be considered carefully because they may
affect distance categories for some targets. This section does not address site aggregation issues.

DEFINITIONS

       Site: Areas where a hazardous substance has been deposited, stored, disposed, or placed, or
       has otherwise come to be located. Such areas may include multiple sources and may include the
       area between sources.

       Source: Any area where a hazardous substance has been deposited, stored, disposed, or
       placed, plus those soils that may  have become contaminated from hazardous substance
       migration. In  general, however, the volumes of air, ground water, surface water, and surface
       water sediments that may have become contaminated through migration are not considered
       sources.

       Source Aggregation: The treatment of two or more areas that could be considered individual
       sources as one discrete source. The area between two or more individual sources may or may
       not be considered part of the aggregated source.

SCORING MULTIPLE SOURCE SITES

       The MRS establishes different procedures for scoring sites with single sources vs. multiple
sources. Two types of MRS factors are affected.

              Factors for which the mechanism of scoring differs for single and multiple source sites
              are affected (Highlights 4-3 and 4-4). These are divided into two groups: (1) factors
              which are summed to obtain the score for multiple sources; and (2) factors in which a
              value is assigned to each source and the highest score for any one source is used for
              scoring; and

              Factors for which sources must meet specific criteria to be eligible for MRS scoring are
              affected (Highlight 4-5).
                                          49
                                                                               Section 4.2

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                                     HIGHLIGHT 4-3
                 HRS FACTORS SUMMED FOR MULTIPLE SOURCES

 When scoring the factors listed below for multiple sources, sum the values form all individual sources
 to obtain the factor value.

        Section 2.4.2                 Hazardous waste quality
        Section 4.1.2.1.2.1.2          Runoff (surface water)
        Sections 5.1.2.2 and 5.2.2.2    Hazardous waste quantity (soil exposure)

 In addition, most targets factors (including the TDL, populations associated with distance categories,
 and sensitive environments) belong in this category.
                                     HIGHLIGHT 4-4
    HRS FACTORS SELECTED FROM INDIVIDUAL SOURCE FACTOR VALUES

 When scoring factors (for pathways and threats) at sites with multiple sources, determine the factor
 values listed below for each individual source and then select the highest factor value for any one
 source as the pathway (or threat) factor value.

        Section 3.1.2.1               Containment (ground water)
        Section 4.1.2.1.2.1.1          Containment (surface water)
        Section 4.1.2.1.2.2            Potential to release by flood (surface water)
        Section 5.2.1.1               Attractiveness/accessibility (soil exposure)
        Section 6.1.2                Potential to release (air)
        Section 6.1.2.1.4             Calculation of gas potential to release value (air)
        Section 6.1.2.2.4             Calculation of particulate potential to release value (air)
                                     HIGHLIGHT 4-5
           HRS FACTORS AFFECTED BY MINIMUM SIZE REQUIREMENTS

 A few HRS factors are affected by the minimum size requirement. For such factors, the scorer should
 consider only those sources with a hazardous waste quantity factor value of 0.5 or more. However, if
 no sources meet the minimum size requirement, evaluate each source for the factors listed below. At
 sites with only one source, evaluate the source regardless of its hazardous waste quantity factor.

        Section 3.1.2.1               Containment (ground water)
        Section 4.1.2.1.2.1.1           Containment (surface water)
        Section 4.1.2.1.2.2.3          Calculation of factor value for potential to release by flood
                                    (surface water)
        Section 6.1.2.1.2             Gas source type (air)
        Section 6.1.2.2.2             Particulate source type air
Section 4.2                                     50

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AGGREGATING SOURCES

       Source aggregation refers to documenting two or more areas that could be considered
individual sources as one discrete source when evaluating one or more pathwaysHighlight 4-6
provides criteria necessary to consider before aggregating sources. Sources may be aggregated in
one pathway and treated separately in another pathway, based on the criteria listed \rHighlight4-6.
In general, it is advantageous to aggregate sources where possible because this should limit the
number of separate sources evaluated without generally changing the overall site score.

       The criteria in Highlight 4-6 are appropriate for use when the sources under consideration are
spatially separated from each other. When two sources overlap, consider site-specific information about
the nature of the disposal operation, the hazardous substances found in the overlapping sources, and the
containment characteristics of the sources in determining what sources should be aggregated.
Highlights 4-7 and 4-8 illustrate when to consider potential sources that apparently overlap as one
source or two sources.
                                      HIGHLIGHT 4-6
                      CHECKLIST FOR SOURCE AGGREGATION

 Questions on this checklist should be used to determine whether to aggregate two or more sources for
 each pathway being evaluated.

 (1)     Can the sources be classified as the same source type for the         Yes    No
        pathway? (e.g., drums, landfills, piles)

 (2)     Do the sources affect similar target populations for the pathway?       Yes    No
        (i.e., target populations significantly overlap)

 (3)     Do the sources have similar containment for the pathway?             Yes    No
        (e.g., liner,  run-on and runoff controls, cover)

 (4)     Do the sources contain substances with similar waste characteristics   Yes    No
        factor values available to the pathway? (e.g., toxicity, persistence
        mobility)

 (5)     Are the sources in the same watershed and floodplain? (surface        Yes    No
        water only)

 (6)     Are the sources overlying the same aquifer system(s)? (ground        Yes    No
        water only)

 If the answer to each of these questions is "Yes" then the sourcesshould be aggregated and treated as
 one source for the pathway. If the answer is  "No" to one or more of these questions, then the sources
 should be treated separately for the pathway.
                                             51                                     Section 4.2

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                                         HIGHLIGHT 4-7
                   WHEN TO AGGREGATE OVERLAPPING SOURCES
                                    Landfill
                                                                             Area 2
                                                                          WP*
    LF  = Sampling point in landfill
    WPX = Sampling point in waste pile

    •       In assessing overlapping sources, consider site-specific disposal operations, hazardous substances
            found in the overlapping sources, and containment characteristics of the sources.

            In this example, two hazardous wastestreams (Areas 1 and 2) overlap within a closed landfill. Drums
            containing hazardous substances had been deposited in part of the landfill (Area 1) and tailings had
            been piled on top of the landfill (Area 2) after it closed.

    •       Sampling data show the following constituents exceed background:

            WP1 = Arsenic, lead
            LF,  =  Arsenic, cadmium, mercury
            LF2  =  Arsenic, mercury, toluene

            Additionally, manifests indicate that drums containing benzene had been deposited in Area 1.

    •       The  buried drums are a wastestream deposited in the landfill. These drums should not be considered
            a separate source.

    •       Consider Area 2 a separate source because the waste pile was deposited after the landfill was closed,
            and  because the containment factors would score significantly different In selected pathways  (e.g.,
            air).
Section 4.2
                                                  52

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                                  HIGHLIGHT 4-8
  WHEN TO AGGREGATE CONTAMINATED SOIL WITH OTHER SOURCES
                 Landfill
                      A real
                                                                             -Tank
                                                                           Area 2
  Sx = Sample point indicating contaminated
       surficial soils
                    Figure 1

Sx = Sampling point indicating contaminated surficial soils
Figure 2
       In Figure 1, contaminated soil (Area 1) is covering a landfill.  Determine if this is one source or two
       sources.

       If the hazardous substances found in surficial soil samples are also found in deeper samples in the
       landfill, the source is simply a landfill.

       If the hazardous substances found in surficial soil are not found in deeper samples, then consider this
       two sources - contaminated soil and a landfill.

       In Figure 2, a leaking tank overlies an area of observed contamination (Area 2). Two sources would
       be present - the tank and contaminated soil.
                                          53
                                                                                   Section 4.2

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TIPS AND REMINDERS

       Score all sources that may significantly affect site score. In particular, consider possible changes
       to waste quantity, contaminant characteristics, or targets if the source is evaluated.

       Consider aggregating sources if they are the same source type and have similar characteristics
       (e.g., containment,  proximity of units, target location, and hazardous substances associated with
       the units). Source aggregation for multiple-source units can change from pathway to pathway.

       For ground water, air, and soil exposure pathways, two strategies may be used to evaluate the
       applicable TDL and targets for multiple sources:

       S       Targets can be the sum of the targets that fall into the distance categories around
               each individual source. This method is most appropriate when evaluating multiple
               sources that are  large or far apart (i.e., distance categories drawn around each source
               do not overlap extensively).

       S       Targets can be determined based on a single source that gives the highest targets
               factor category value. This method is appropriate for sites where considering multiple
               sources will not significantly affect the score.

       In the ground water migration pathway, it may be more efficient to measure the distance from
       each target well (if there  are few) to the nearest source (if there are multiple sources) than to
       draw distance categories.

       For sources that are in the same watershed but have multiple PPEs to a watershed, the TDL
       should generally include  the distance from the most upstream PPE to 15 miles from the most
       downstream PPE.

       For sources that have PPEs to different surface water bodies in the same watershed, determine
       the TDL from each  PPE.  The TDL for the watershed includes all in-water segments from these
       PPEs to the point where  the water bodies merge plus the longest downstream distance as
       determined from each PPE.

       If sources are in different watersheds, score each watershed separately, and  use the highest
       scoring watershed to score the pathway.
Section 4.2                                      54

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CHAPTER  5
     SERVED RELEASE
•i:
                   Is the concentration of the
                   hazardous substance in the
                   release sample significantly
                    above background?
                  Is the hazardous substance
                   attributable to the site?
                  Is a portion of the significant
                  increase above background
                    attributable to the site?
                   OBSERVED RELEASE
                         or
                 OBSERVED CONTAMINATION
                     ESTABLISHED

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SECTION 5.1
ESTABLISHING AN
OBSERVED RELEASE
AND  OBSERVED
CONTAMINATION
HHMwRlwNMI
* ; 
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                                            HIGHLIGHT 5-1
               FLOWCHART FOR ESTABLISHING AN  OBSERVED RELEASE
                                OR OBSERVED CONTAMINATION
                                                  Is the concentration of
                                                hazardous substance in the
                                                release sample significantly
                                                  above background (see
                                                     Highlight 5-2}!
     Was the material containing
       a hazardous substance
     placed into or seen entering
     the environmental medium?
               Is the hazardous
                 substance
              attributable to the
                   site?
                                                                            Is the hazardous
                                                                               substance
                                                                           attributable to the
                                                                                site?
No observed
  release
                                                                                 Is a portion of the
                                                                                significant increase
                                                                                attributable to the
                                                                                      site?
         Observed release
        established by direct
           observatioa a
                                                                            Observed release or observed
                                                                            contamination b established by
                                                                                 chemical analysis.
a Observed contamination for the sol exposure
 pathway cannot be estabished by direct observatioa

b Observed contamination for the sol exposure
 pathway can be estabished If there is no
 impenetrable cover and the 2 foot Iml te considered,
Section 5.1
                                                      56

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in the medium of concern for the environmental setting on or near a site. Background level does
not necessarily represent pre-release conditions, nor conditions in the absence of influence from
source(s) at the site. A background level may or may not be less than the detection limit (DL),
but if it is greater than the DL,  it should account for variability in local concentrations. A
background level need not be  established by chemical analysis.

Background Sample: A sample used in establishing a background level.

Contract Laboratory Program (CLP): The analytical program developed for CERCLA waste
site samples to fulfill the  need  for legally defensible analytical results supported by a high level of
quality assurance and documentation.

Contract-required Detection Limit (CRDL): A term equivalent to the contract-required
quantitation limit (CRQL), but used primarily for inorganic substances.

Contract-required Quantitation Limit (CRQL): The substance-specific level that a CLP
laboratory must be able to routinely and reliably detect in specific sample matrices. The CRQL is
not the lowest detectable level achievable, but rather the level that a CLP laboratory must
reliably quantify. The CRQL may  or may not be equal to the quantitation limit of a given
substance in a given sample. For  MRS purposes, the term CRQL also refers to the CRDL.

Detection Limit (DL): The smallest quantity of a hazardous substance that can be distinguished
from the normal random "noise" of an analytical instrument or method. For MRS purposes, DL is
the method detection limit (MDL) or, for real-time field instruments, the instrument detection limit
(IDL) as used in the field.

Method Detection Limit (MDL): The lowest concentration of a hazardous substance that a
method can detect reliably in either a sample or blank.

Observed Contamination: Surficial contamination related to a site. It must be established by
chemical analysis. Observed contamination is present at sampling locations where analytic
evidence indicates that:

       A hazardous substance attributable to the site is present at a concentration significantly
       above background  levels  for the site (i.e., meets the observed release criteria in MRS
       Table 2-3).

       The hazardous substance is present at the surface or covered by two feet or less of
       cover material (e.g., soil).

Observed Release: An observed release is established for the ground water, surface  water,  or
air migration pathway either by chemical analysis or by direct observation. Observed release is
not relevant to the MRS soil exposure pathway. The minimum requirements for establishing an
observed release by chemical  analysis are analytical data demonstrating the presence of a
hazardous substance in the medium significantly above background level, and information that
some portion  of that increase is attributable to the site. The minimum criterion for establishing an
observed release by direct observation is evidence that the hazardous substance was placed into
or has been seen entering the  medium.

Release Sample: A sample taken to determine whether the concentration of a hazardous
substance is significantly above its background level in order to determine whether an observed
release (or observed contamination) has occurred.

Sample Quantitation Limit (SQL): The quantity of a substance that can be reasonably
quantified given the limits of detection for the methods of analysis  and sample characteristics
that may affect quantitation (e.g.,  dilution, concentration).


                                     57                                     Section 5.1

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       Similar Samples: Samples from the same environmental medium that are identical or similar in
       every way (e.g. field collection procedure, analytical technique) except the degree to which they
       are affected by a site.

ESTABLISHING AN OBSERVED RELEASE BY CHEMICAL ANALYSIS

       Establishing an observed release (or observed contamination) by chemical analysis generally
requires documenting that the concentration of at least one hazardous substance in a release sample is
significantly increased above its background level, and that the substance in the release can be
attributed to the site. Note that some additional rules apply for observed contamination (see Section 9.1).
General guidance for establishing an observed release by chemical analysis is presented below. An
observed release is established at most sites by comparing analytical data derived from samples
reflective of site-specific background with analytical data derived from site-related samples. Sample data
used to establish  an observed release should be of known and documented quality. Analytical data may
come from the SI  or from studies done by other EPA offices, states, other Federal agencies,  or PRPs.

CONSIDERATIONS FOR BACKGROUND

       All relevant data should be evaluated to determine representativeness of the background
samples and attribution. In certain circumstances, background samples are not required to establish an
observed release by chemical analysis. Additional guidance used for selecting background samples is
provided in Section 5.2. See subsection below, Using Published Data for Background Levels, for a
discussion on establishing background levels. The general guidelines below introduce the main concepts.

              Background and release samples must be from the same medium (e.g., soil, water,
              tissue) and should be as similar as possible. Similar sampling methods should be used
              to obtain background and  release samples. Ideally, background samples also should be
              outside the influence of contamination from the site, but background levels may be
              determined from samples  which contain measurable levels of contamination.

              Many hazardous substances may be widespread in the environment in the vicinity of a
              site. Widespread substances may originate naturally, from non-point sources, or from
              large point sources. The background level for widespread substances should account for
              local variability. Several background samples may be required to establish variability in
              background concentrations (see Section 5.2).

SIGNIFICANCE ABOVE BACKGROUND

       The concentration in the release sample must be equal to or greater than the release sample
SQL. Continue  with the steps below only after determining that the release sample is above  its SQL. The
criteria used for determining significance  above background depend  on whether the background level is
above or below the background DL.

              If the background level is  greater than or equal to its  DL, the minimum requirement for
              an observed release is that the concentration in the release sample is  at least three
              times greater than the background level.

              If the background level is  below its DL, the minimum requirement for establishing an
              observed release is that the concentration in the release sample is greater than or equal
              to the background SQL.

                     If the SQL for the hazardous substance  cannot be established and the sample
                     analysis was performed under the CLP,  use the CRQL  in place of the SQL.
Section 5.1                                    58

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                     If the SQL for the hazardous substance cannot be established and the sample
                     analysis was not performed under the CLP, use the DL in place of the SQL.

       The considerations detailed in the bullets above are presented in flowchart forn+Kghlight
5-2. Highlight 5-3 presents several examples of how to decide whether or not significance above
background is established.

ATTRIBUTION

       Attribution generally involves demonstrating that the hazardous substance used to establish an
observed release can be associated with the site,  and the site contributed at least in part to the
significant increase in the concentration of the hazardous substance. Attribution can be established
based on sampling or non-sampling data.

              The following information generally is sufficient to associate the  hazardous substance to
              the site:

                     Manifests, labels, records, oral or written statements, or other information about
                     site operations exist that demonstrates that the  hazardous substance was
                     deposited or is present in a source (or somewhere at the site). Note that if
                     confirmed by manifests, labels, or oral or written statements, attribution
                     generally can be established even if the specific source(s) where the substance
                     was deposited cannot be documented.

                     Analytical sampling data that demonstrate the presence  of the hazardous
                     substance in a source at a concentration greater than background.

              The data required to attribute a portion of the significant increase in the concentration of
              the hazardous substance to the site generally depend on whether or not the site being
              evaluated is located in an area where other sources may have contributed to the
              significant increase.

                     When  no other nearby sources are likely to have contributed to the release, or
                     when the site-specific background concentration is less than the DL, it generally
                     will be sufficient to document that the  hazardous substance is associated with a
                     source at the site that could have released to the environmental  medium of
                     concern.

                     When  other sources are present in the vicinity of the site being evaluated and
                     may have contributed to the significant increase (e.g., in highly industrialized
                     areas), it generally is necessary to obtain sufficient samples between the site
                     being evaluated  and other known potential sources (or between the site and
                     adjacent sites) in order to demonstrate an increase in concentration attributable
                     to the site. Additional information may be required if other sites are known to
                     release substances intermittently, such that "pulses" of hazardous substances
                     are created  in environmental media. Types of information that will strengthen
                     such attribution include:

                             Data on concentration gradients (e.g., established based  on samples
                             from multiple wells or a series of samples  between the site and the
                             alternative source);

                             Data on flow gradients or other information about the movement of
                             hazardous substances in the environmental medium of concern; or
                                             59                                     Section 5.1

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                                         HIGHLIGHT 5-2
       FLOWCHART FOR DETERMINING SIGNIFICANCE ABOVE BACKGROUND
              Are SQLs
              available?
                                   Is the analysis
                                   under the CLP?
Use DL for SQL
                Is the
            release sample
         concentration greater
            than its SQL?
                               Is the background
                              sample concentration
                              greater than its SQL?
                                                                             Is the
                                                                          release sample
                                                                       concentration greater
                                                                       than the background
                                                                             SQL?
                              Is the release sample
                             concentration at least
                              three times greater
                               than background?
                                                        Significance above
                                                      backgound established.
                                                       See Highlight 5-1 for
                                                     other criteria to establish
                                                        an observed release.
Significance above
background is not
   established.
Section 5.1
                                                  60

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c
b
HIGHLIGHT 5-3
EXAMPLES FOR DECIDING WHETHER SIGNIFICANCE
ABOVE BACKGROUND IS ESTABLISHED
Background
SQL (ppb)
20
20
20
20
50
50
50
Background
Concertration
(ppb)
30
30
5a
NDb
NDb
NDb
NDb
Sample
SQL
(ppb)
50
50
20
50
20
20
60
Sample
Concentration
(ppb)
100
60
16a
55
55
25
55
Significance Above Background
Established?
Yes, sample concentration is greater
than three times the background
concentration
No, sample concentration is less than
three times the background
concentration
No, sample concentration is less than
the SQL
Yes, sample concentration is greater
than both SQLs
Yes, sample concentration is greater
than both SQLs
No, sample concentration is less than
the background SQL
No, sample concentration is less than
the sample SQL
a When reported concentrations are less than SQLs, it is likely that data qualifiers would be associated with the
oncentrations (seeHighlight 5-4).
bThe entry "ND" signifies the substance was not detected (i.e., the background concentration is less than the
ackground SQL).

                            Analytical "fingerprinting" data that establish an association between the
                            site and a unique form of the substance or unique ratios of different
                            substances.

       The above general guidelines apply to all MRS pathways and threats. Additional pathway-specific
considerations are presented below.

PATHWAY-SPECIFIC CONSIDERATIONS

Ground Water Pathway

              Background and release samples must be from the same aquifer because background
              levels, water chemistry, and other parameters may vary among  aquifers.

              In some cases a contaminated well can serve as its own background (e.g., if similar
              samples at different points in time establish background levels and levels significantly
              above background).
                                            61
                                                                                  Section 5.1

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              When evaluating a ground water plume with no identified source, background samples
              are required, but the release need not be attributed to a specific site.

       Surface Water Pathway

              Background samples and release samples must be the same type of sample (e.g.,
              aqueous samples must be compared to aqueous samples, sediment samples must be
              compared to sediment samples).

              For tissue samples, only samples from essentially sessile, benthic organisms (e.g.,
              mussels, oysters) can be used to establish an observed release.

              When evaluating contaminated sediments with no  identified source, background
              samples are required, but no separate attribution is required.

       Soil Exposure Pathway

              Observed contamination can be established only when the hazardous substance  is
              present at the surface or covered by two feet or less of cover material (e.g., soil).
              However, any area covered by a permanent or otherwise maintained, essentially
              impenetrable material (e.g., asphalt) cannot be considered an area of observed
              contamination.

              For contaminated soil, areas of observed contamination can be inferred for the area
              lying between sampling locations at which observed contamination  is established unless
              available information (e.g., topography, site operations, impenetrable cover, drainage
              patterns) indicates otherwise.

              For sources other than contaminated soil, the entire source is considered an area of
              observed contamination if observed contamination is established at any point on the
              source and within two feet of the surface.

       Air Pathway

              Indoor air samples cannot be used to establish an  observed release.

USING PUBLISHED DATA FOR BACKGROUND LEVELS

       At some sites, it may not be possible to collect sample(s) to determine  a background level.
Certain circumstances may preclude background sampling  (or use of available background sampling
data) for the site.  Several such circumstances are outlined  below.

              No appropriate background sampling locations for  the site were found. This
              circumstance generally applies only to the surface water pathway (e.g., a release to an
              isolated pond  or wetland; surface water originates  from a spring on  the site).

              Resource constraints precluded background sampling.

Under such circumstances, it may be necessary to establish the background  level based on published
data relevant to the site. Existing data from published reports should be evaluated to determine  if
background levels can be developed. Documentation should focus on  establishing  what the
concentration of the hazardous substance of concern should be for the medium of concern  in the
absence of contamination attributable to the site.

       The appropriateness of published data for establishing background levels must be determined on
a case-by-case basis. Noa priori set of criteria regarding use of published data can be


Section 5.1                                     62

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established for every hazardous substance and type of site. The guidelines presented below, while
helpful in evaluating the appropriateness of such data, are not intended as definitive criteria for accepting
or rejecting such data. Published values may not be site-specific enough to be appropriate for
determining background levels.

              Potential background levels should be obtained from multiple data sources. Sources of
              data should include regional and local studies. Ideally, only primary sources should  be
              used. Examples of primary data sources include regional soil lead studies, surveys of
              sediment contamination in harbors and bays, and national tissue residue surveys such
              as NOAA's mussel watch program.

              The variability of background concentrations for the substance on a national, regional,
              and local scale should be described as fully as possible. Variability will depend, in part,
              on the nature of the hazardous substance. Naturally occurring substances such as heavy
              metals, for example, are expected to be distributed more widely in the environment than
              are organic substances used in a limited number of manufacturing practices. Variability
              will also depend on the local environment. Information on other sources near the site will
              help determine whether unusually high background concentrations are expected (e.g.,
              soil lead levels are expected to be higher near major highways).

              Regional geology may help determine where higher concentrations of naturally occurring
              substances are likely (e.g., ore veins, soil types with unusually high metals
              concentrations).

USING QUALIFIED DATA

       For analytical results, particularly those developed within the CLP, various data qualifiers and
codes (collectively termed "qualifiers") may be attached to certain data by the laboratory conducting the
analysis. Data qualifiers also may be added, modified, or changed during data validation. The qualifiers
pertain to QA and QC variations which result in uncertain confidence concerning the identity of the
substance being analyzed, its concentration, or both. The QA and  QC conditions that result in data
qualification must be evaluated with respect to the decision being  made (e.g., establishing an observed
release) before using the data in MRS scoring. Because non-CLP laboratories may assign codes that
differ from those of the CLP, it is important to ascertain the exact meaning of all data qualifiers. See
Highlight 5-4 for some considerations that are usually applicable to data generated within CLP.

ESTABLISHING AN OBSERVED RELEASE  BY DIRECT OBSERVATION

       In contrast to establishing an observed  release by chemical analysis, where significance above
background and  attribution are interrelated, establishing an observed release by direct observation
generally only requires information that material containing a hazardous substance attributable to the site
was placed into or has been seen entering the medium of concern. Attribution in this case generally
involves documenting that the substance in the release is associated with the site, either with
non-sampling or sampling data. Pathway-specific considerations are outlined below.

GROUND WATER PATHWAY

              Establishing an  observed release by direct observation generally requires information
              that material containing a hazardous substance has been deposited directly into or
              otherwise  has come to be located (e.g., due to a rising water table) below the top of the
              aquifer being evaluated.
                                            63                                      Section 5.1

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                                      HIGHLIGHT 5-4

        DEFINITIONS AND APPLICATIONS OF COMMON DATA QUALIFIERS

 "J"         The identity of the hazardous substance is known with certainty, but the reported concentration is
            considered an estimate. Data may be useable  in selected circumstances (see examples below).


 "U"         The hazardous substance was analyzed for and was not present above the reported concentration.
            Data may be useable as an upperbound on background concentration.

 "R"         The identity and concentration  of the hazardous substance are uncertain due to exceeded QC
            limits.
            Data generally not useable for either background or release purposes.

 For example, suppose a scorer had a background sample of 3J, which is biased high, and a release sample of
 10J, which is biased low. The direction of bias Indicates that the accurate background concentration is lower than
 the  reported concentration,  and the  accurate release concentration  is greater than  the  reported  release
 concentration.Assuming attribution can be established, the data are useable to establish an observed release,
 because the release concentration (i.e., 10 or more) is more than three times background (i.e., 3 or less).

 In a more complex example,  suppose a scorer had background sample of 10J, which was biased high  at 30
 percent, and a release sample of 40J, which was biased high at 20 percent (i.e., concentration could be  as high
 as 48). Assuming attribution can be established, these data also would be useable to establish an observed
 release, because the lower bound of the release  samp(e.e.,  40) is more than three times the upper bound of
 the  background sample (i.e., 13).
SURFACE WATER PATHWAY
               Establishing an observed release by direct observation generally requires information
               that:

                      Material containing a hazardous substance has been seen entering surface
                      water through migration or direct deposition;

                      A source area has been flooded at a time that a hazardous substance was
                      present in the source, and  material containing a hazardous substance was in
                      direct contact with the surface water; or

                      Information documenting adverse affects associated with a release of a
                      hazardous substance to surface water (e.g., a fish kill incident) supports the
                      inference of a release of material containing that  hazardous substance from the
                      site to surface water.

               When basing an  observed release on inference of a release by demonstrated adverse
               effects, it generally is necessary to provide a rationale for inferring the release from the
               site, to document that the substance was present on the site prior to or at the time the
               adverse effects occurred, and to document that the adverse effects were likely caused
               by the substance.

               When the source area that has been flooded is contaminated soil, it is necessary to
               demonstrate that the hazardous substance was present at a concentration significantly
               above background  level in order to document an observed release.
Section 5.1                                      64

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SOIL EXPOSURE PATHWAY
              Observed contamination in the soil exposure pathway cannot be established by direct
              observation.
AIR PATHWAY

              Establishing an observed release by direct observation generally requires information
              that:

                     Material containing a hazardous substance has been seen entering the
                     atmosphere directly (e.g., particulate material blowing off a pile);

                     Information supports the inference of a release from the site to the atmosphere
                     of material that contains at least one hazardous substance; or

                     Information documenting adverse effects associated with the release of a
                     hazardous substance to air (e.g., human health effects) supports the inference of
                     a release  of material containing that hazardous substance from the site to air.

              When basing an observed release on inference of a release  by demonstrated adverse
              effects, it generally is necessary to provide a rationale for inferring the release from the
              site, to document  that the substance was present on the site prior to or at the time the
              adverse effects occurred, and to document that the adverse effects were likely caused
              by the substance.

              If the source used to establish an observed release is contaminated soil, it is necessary
              to demonstrate that the hazardous substance was present at  a concentration significantly
              above background level to document an observed release.

TIPS AND REMINDERS

       Establishing an observed  release by direct observation generally requires the following
       information: (1) material containing a hazardous substance was placed into or has been seen
       entering the medium of concern, and (2) the substance in the release is associated with the site.
       If the source is contaminated soil, the  concentration of the hazardous substance in the
       contaminated soil must be significantly above background and some portion  of the increase must
       be attributable to the site.

       Establishing an observed  release by chemical analysis generally requires the following
       information: (1) the concentration of at least one hazardous substance  in a release sample is
       significantly increased above the background level, (2) the substance in the release is associated
       with the site, and (3) the site contributed at least in part to the significant increase.

       Background level  need not be established by chemical analysis.

       The difficulties in attributing an increase in concentration to a site can be avoided if an observed
       release by direct observation can be established.
                                             65                                     Section 5.1

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SECTION 5.2
SELECTING  APPROPRIATE
BACKGROUND SAMPLES
                                                                  fl
                                                nr-rl
   A background level for a site provides a reference point by which to
evaluate whether or not a release of a hazardous substance from the site has occurred. Determining
background level is necessary to establish an observed release (or observed contamination) by chemical
analysis. This section provides guidance on selecting appropriate samples for determining background
level for a site. The application of background levels in establishing an observed release (or observed
contamination) by chemical analysis is discussed in Section 5.1 of this document.

   When chemical analysis is used to determine background levels, the background and release
samples must be from the same medium (e.g., soil, water, tissue) and should be as similar as possible
except for potential influence from the site. Similar sampling methods should be used to obtain
background and release samples. Ideally, background samples should be outside the influence of
contamination from the site, but background levels may be determined from samples that contain
measurable levels of contamination. Background levels also do not need to represent pre-release
conditions at the site.
        Section 2.3
        Section 3.1.1
        Section 4.1.2.1.1
        Section 5.0.1
        Section 6.1.1
 RELEVANT MRS SECTIONS
Likelihood of release
Observed release (ground water)
Observed release (surface water)
General considerations (soil exposure)
Observed release (air)
DEFINITIONS

   Background Level: The concentration of a hazardous substance that provides a defensible
   reference point that can be used to evaluate whether or not a release from the site has occurred. The
   background level should reflect the concentration of the hazardous substance in the medium of
   concern for the environmental setting on or near a site. Background level does not necessarily
   represent pre-release conditions, nor conditions in the absence of influence from source(s) at the
   site. A background level may or may not be less than the DL, but if it is greater than the DL, it should
   account for variability in local concentrations. A background  level need not be established by
   chemical analysis.

   Background Sample: A sample used in establishing a background level.

   Release Sample: A sample taken to determine whether the concentration of a hazardous substance
   is significantly above its background level in order to determine whether an observed release (or
   observed contamination) has occurred.
                                         67
                                                                            Section 5.2

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       Similar Samples: Samples from the same environmental medium that are identical or similar in
       every way (e.g., field collection procedure, analytical technique) except the degree to which they
       are affected by a site.

DATA REQUIREMENTS

       The minimum data requirements for establishing background levels by chemical analysis include
the actual analytical data from the background sample(s) and sufficient other information to establish
similarity between background and release samples. Analytical data may be obtained from one or more
background sample(s).

NUMBER OF SAMPLES FOR ESTABLISHING BACKGROUND LEVELS BY CHEMICAL ANALYSIS

           Where background is established by chemical analysis, a single sample  may provide a
defensible background level. However, when the hazardous substances being considered are
widespread in the environment (e.g., pesticides in an agricultural area, naturally occurring trace metals)
and/or may have  come from other nearby sites, one sample generally will not be sufficient. At such sites,
attribution also may be difficult (see Section 5.1). Factors influencing the number of samples used to
establish background levels by chemical analysis include:

              Physical complexity of the site (e.g., size, number of source types);

              Physical complexity of migration routes (e.g., number of watersheds,  number of
              overland segments in each hazardous substance migration path);

              Temporal complexity of site data (e.g., time periods over which sampling and other data
              were collected);

              Meteorological  conditions under which samples were collected;

              Number of hazardous substances present at the site, their expected concentrations in
              sources and  releases, and the degree to which they are widespread in the vicinity of the
              site;

              Number and  physical/chemical complexity of environmental media being sampled (e.g.,
              number and interconnection of aquifers, heterogeneity of soils and sediments, number
              and type of water bodies within watershed);

              Type of samples  (e.g., filtered or unfiltered); and

              Other potential sources in the vicinity of the site.

       At some sites, multiple background samples appropriate for a particular environmental medium
will exhibit different concentrations for the same hazardous substance. In this situation, using the sample
with the highest concentration is always defensible in a legal sense (i.e., the background level based on
available samples could not be higher than the value selected), but it may not always be appropriate.
Generally, it is  best to decide on a case-by-case basis whether to use the highest, lowest, or a measure
of central tendency of the samples to establish background.

ESTABLISHING  SIMILARITY BETWEEN BACKGROUND AND RELEASE SAMPLES

       Analytical data from background samples is necessary but may not be sufficient to establish
background levels by chemical  analysis. Additional information related to the site and sampling
procedures is often desirable to establish similarity between the background and release samples.
Examples of things to consider in establishing similarity may include:
Section 5.2                                     68

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              Type of samples (e.g., soil, sediment, air);

              Time and location at which samples were collected;

              Physical conditions under which samples were collected (e.g., meteorological conditions,
              season);

              Sampling, handling, and analytical chemistry procedures used; and

              Environmental setting for each sample (e.g., topography, land use in the vicinity of the
              sampling locations, streamflow).

DATA EVALUATION GUIDELINES

       Temporal and spatial variations in measured concentrations often make it difficult to define
background. Large differences in analytical results may result from differences that are independent of
site-related contamination (e.g., differences in the manner in which samples were collected, differences
in the physical or chemical conditions under which the samples were collected). This section provides
guidance for selecting background samples that will yield the most defensible background levels.
General considerations are followed by pathway-specific considerations.

GENERAL CONSIDERATIONS

              In most cases, samples will be designated as background at the time of an SI. In some
              cases, however, it may be necessary to re-evaluate which samples are background and
              release after the data have been collected (e.g., when analytical data or additional site
              information suggest a different pattern of contamination than originally expected).

              Sampling and analysis methods should  be the same for background and release
              samples.

              Background samples do not have to be  completely outside the influence of the site. This
              may be particularly applicable in areas where the  presence of other potential sources
              and/or the complexity of the nearby environment make it difficult to select a background
              sampling location that  is not influenced  by the site.

GROUND WATER PATHWAY

       Data evaluation guidelines for the ground water pathway are presented below. General
guidelines are presented first, followed by guidelines specific to the following situations:  the background
well and release well are in the same aquifer; there is no background well in the aquifer in which the
release well is located; and the release well serves as its own background well.

General Guidelines

              An understanding and  description of aquifers and  their boundaries are necessary for
              identifying background samples.  Information must be sufficient to identify the types and
              boundaries of geologic materials within  the TDL for the site. Minimum information
              includes types of bedrock, soil, or other non-consolidated material, and their lateral and
              vertical boundaries; types of surficial deposits and their boundaries (i.e., thicknesses and
              lateral extents); and locations and screened depths of release and background wells.
              Guidance on determining aquifers and aquifer boundaries is presented in Section 7.1.
                                             69                                      Section 5.2

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              When a connection has been established between two individual aquifers, the
              background sample must be taken from the same aquifer as the release sample (e.g., a
              background sample taken from a bedrock aquifer cannot be compared to a release
              sample taken from an overlying alluvial aquifer, even if a hydrologic connection has
              been documented between the two aquifers and they are being considered a single
              hydrologic unit for purposes of MRS scoring). Different aquifers may have very different
              background levels as well as other important differences in water chemistry.

              Information on ground water flow gradients in the  area is not required  and may not be
              known completely at the time of the SI. Depending on site conditions,  background wells
              may be upgradient, side-gradient, ordowngradient from sources. In complex situations,
              with multiple sources and aquifers,  selecting or installing wells for background samples
              will require considerable knowledge of aquifers, aquifer boundaries, and aquifer
              interconnections.

Background Well and Release Well In Same Aquifer

       At some sites, one or more potential background wells already exist in the aquifer(s) of concern
(i.e., these wells did not need to be installed during the SI). Such a situation generally will make it easier
to obtain background samples. However, existing wells may not be suitable for background samples,
even if they are not influenced by sources at the site.  Highlights 5-5, 5-6, and 5-7 provide illustrations
of appropriate background wells for the ground water  pathway. Note that these illustrations are highly
idealized and are not meant to reflect expected site-specific conditions.

              In general, background and release samples should be from approximately the same
              depths in  an aquifer, although different depths may be appropriate under certain
              circumstances. Factors to consider include aquifer structure, the nature of the hazardous
              substances, and other possible sources, including natural sources. Ground water tends
              not to be well mixed, and water quality can vary significantly in the vertical plane within
              an aquifer. This is particularly true when substances that have a tendency to sink or float
              in the aquifer are present (i.e., dense  non-aqueous phase liquids (DNAPLs) and light
              non-aqueous phase  liquids (LNAPLs)). Depth should be determined relative to a fixed
              reference point (e.g., mean sea level) rather than  the ground surface to eliminate
              apparent differences caused by surface topography.

              If the background sample well is screened, the well screen interval must be in the same
              aquifer as the release sample well.

              A well screened over two or more distinct aquifers cannot be used to establish
              background or release levels of hazardous substances.

              Take particular care  in areas that are  hydrogeologically complex. In glaciated terrain, for
              example, water may  occur within  sand lenses of limited areal extent, and surrounding
              soil with a substantial clay component could serve to isolate these lenses. Thus, each
              sand lens may be, in effect, a small, independent  aquifer, making it difficult to establish
              background. In such areas, geologic cross sections may be necessary to understand the
              underlying aquifer system.

No Background Well In Release Well Aquifer

       At some sites, no  potential background wells exist in the aquifer(s) of concern  prior to the SI. At
these sites, background levels may be determined only in two ways: by installing monitoring wells at
appropriate background locations, or based on appropriate published concentration data. Data from
monitoring wells generally are preferred over data from the literature. Guidance for using published
concentration data to establish background levels is presented in  Section 5.1.
Section 5.2                                      70

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                                   HIGHLIGHT 5-5
        ILLUSTRATION OF APPROPRIATE BACKGROUND SAMPLES:
               GROUND WATER PATHWAY - SINGLE AQUIFER
          1 Screening Interval
Illustrated in this idealized drawing is a source releasing LNAPLs, DNAPLs, and other hazardous substances
to a single aquifer. Assume that the eight wells have a similar development history. The appropriateness of
each well for release and background samples is given below:
Type of
Hazardous
Substance
LNAPLs
Others
DNAPLs
Release Samples
A
N/A
Yes
Yes
B
N/A
Yes
N/A
C
Yes
N/A
N/A
D
Yes
Yes
N/A
Background Samples
E
Yes
No
No
F
No
Yes
No
G
No
No
Yes
H
Yes
Yes
Yes
   For LNAPLs, E and H are appropriate background wells and C and D are appropriate release wells because
   their screening intervals are at the top of the aquifer (where LNAPLs are likely to occur).

   For DNAPLs, G and H are appropriate background wells and A is the only appropriate release well because
   their screening intervals are at the bottom of the aquifer (where DNAPLs are likely to occur).

   For other hazardous substances,  F and  H are appropriate background wells and A, B, and D are
   appropriate release wells because their screening intervals are in the middle  of the aquifer (where these
   substances are likely to occur).

                                           71
                                                                                      Section 5.2

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                                       HIGHLIGHT 5-6
             ILLUSTRATION OF APPROPRIATE  BACKGROUND SAMPLES:
                  GROUND WATER PATHWAY — MULTIPLE AQUIFERS
             ] Screening Interval
     Illustrated In this idealized drawing is a source releasing hazardous substances to two aquifers that are not
     interconnected within 2 miles of sources at the site.  Assume that the seven wells have a similar development
     history.  The appropriateness of each well for release and background samples is given below:
Aquifer
Aquifer 1
Aquifer 2
Release Samples
A
No
No
B
No
Yes
C
Yes
No
Background Samples
D
Yes
No
E
No
Yes
F
No
No
G
Yes
No
         For Aquifer 1,  D and G are appropriate background wells and C is an appropriate release well.

         For Aquifer 2, E Is an appropriate background well and B is an appropriate release well.  A is not an
         appropriate release well and F Is not an appropriate background well because both wells are screened
         in both aquifers.
Section 5.2
                                               72

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                                  HIGHLIGHT 5-7
        ILLUSTRATION OF APPROPRIATE BACKGROUND SAMPLES:
       GROUND WATER PATHWAY - INTERCONNECTED AQUIFERS
     fQq Screening Interval


Illustrated in this idealized drawing is a source releasing hazardous substances to three aquifers, two of which
are Interconnected within 2 miles  of sources at the site,  Assume that the eight wells have a similar
development history. The appropriateness of each well for release and background samples is given below:
Aquifer
Aquifer 1
Aquifer 2
Aquifer 3
Release Samples
A
No
Yes -
No
B
No
No
Yes
C
No
No
No
D
Yes
No
No
Background Samples
E
Yes
No
No
F
No
Yes
No
G
No
No
No
H
No
No
Yes
    For Aquifer 1, E is the only appropriate background well and D is the only appropriate release well.

    For Aquifer 2, F is the only appropriate background well and A is the only appropriate release well.
    Although Aquifers 2 and 3 are interconnected, H is not an appropriate background well for Aquifer 2
    because it is screened in Aquifer 3,

    For Aquifer 3, H is the only appropriate background well and B is the only appropriate release well.

    Well G cannot serve as a background well because it is screened in both Aquifer 2 and Aquifer 3.
    Well C cannot serve as a release well because it is screened in both Aquifer 2 and Aquifer 3.
                                           73
                                                                                     Section 5.2

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Release Well Serves as its Own Background

       Under some circumstances a single well, overtime, may provide both background and release
samples. For example, where a regular water quality monitoring program is in effect (e.g., at municipal
wells), a time series of monitoring data may document encroachment of a hazardous substance plume.
Data must be available from a sufficient  period of record, so that a trend in increasing concentrations can
be demonstrated clearly.

SURFACE WATER PATHWAY

       Data evaluation guidelines for the surface water pathway are presented below. General
guidelines are presented first, followed by guidelines specific to particular types of surface water bodies
(i.e., streams and rivers; lakes, Great Lakes, and other large water bodies; and tidally influenced areas)
and particular types of samples (i.e., aqueous,  sediment, and \\ssue).Highlight 5-8 provides an
idealized illustration of appropriate background sampling locations for the surface water pathway.

General Guidelines

              An observed release by chemical analysis can be established in the surface water
              pathway using aqueous samples, sediment samples, and/or tissue samples from
              essentially sessile benthic organisms. Background and release samples  must be of the
              same type (e.g., aqueous samples must be compared to aqueous samples, sediment to
              sediment).

              Chemical and physical properties of surface water and sediments may vary substantially
              within a small area. Stratification of lakes, lack of mixing in slowly moving rivers, and
              mixing effects induced by tributaries may affect the appropriateness of a  given sampling
              location for establishing background levels. Environmental conditions at  both the
              background and release sample locations should be similar.

Non-tidal Streams and Rivers

              Background samples should be collected upstream from the potentially contaminated
              area.  In the simplest case (i.e., one PPE and one main channel), one background
              sample may be sufficient. In cases where there is significant branching or tributary input
              upstream of the PPE, more than one background sample may be appropriate.

              If there are  multiple PPEs, background samples may be appropriate for each PPE,
              particularly if the  hazardous substances for each PPE are different and significant
              branching or tributary input occurs between PPEs.

              Where possible,  background and release samples should be collected from the same
              general part of the surface water body (e.g., a background sample taken  near one bank
              generally should  not be  compared with a release sample taken from the center of the
              main channel).

Ponds and Other Small, Isolated Water Bodies

       In ponds and other  small, isolated water bodies, it may not be possible to collect  background and
release samples from the same water body (e.g., the entire pond may be influenced by the site). In that
case, background can be established as follows.

              Samples of water flowing into the pond may provide  background levels if there is a clear
              inflow and this is  not influenced by the site.
Section 5.2                                     74

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                                 HIGHLIGHT 5-8
        ILLUSTRATION OF APPROPRIATE BACKGROUND SAMPLES:
           SURFACE WATER PATHWAY - STREAMS AND RIVERS
                                Direction of Flow
Illustrated in this idealized drawing is a site releasing hazardous substances from two sources to two branches
of a river. Assume that the five samples are similar (e.g., they are all sediment samples collected from similar
substrates at similar times and were handled and analyzed  in an identical manner). The appropriate
background sample for each release sample is given below:
Release Sample
Sample C
Sample D
Sample E
Appropriate Background
Sample(s)
A
Yes
No
Yes
B
No
Yes
Yes
       For Release Sample C, A is the only appropriate background sample because any increased
       hazardous substance concentrations could be attributed to Source 1.

       For Release Sample D, B is the only appropriate background sample because any increased
       hazardous substance concentrations could be attributed to Source 2.

       For Release Sample E, both A and B are appropriate background samples because contamination
       could be flowing down either or both branches upstream of Sample E.
                                        75
                                                                                Section 5.2

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              Samples from an analogous water body outside of the area influenced by the site (e,g., a
              nearby pond of similar size and type) may provide background levels.

              Background levels may be established based on literature values without having to take
              samples (see Section 5.1).

Lakes, Great Lakes, and Other Large Water Bodies

              In smaller lakes, samples at the point where surface water enters the take generally will
              provide appropriate background levels. If there is no obvious point of entry, it generally
              is best to use samples as far as possible from the PPE(s) to establish background levels.
              However, the presence of springs, other potential sources, and points of flow out of the
              lake may influence selection  of background locations.

              If other potential sources are near the site, background samples should be collected
              between the PPE for the site and the PPE for other potential sources. Ideally,
              background samples should also be out of the zone of influence of the other potential
              sources.

              In large water bodies, background samples should be collected as far from the PPE as
              possible, except when other potential sources, points of flow into the lake, or points of
              flow out of the lake are  present in between.
Tidal Areas
               In tidal water bodies, background samples ideally should be collected beyond the
               farthest upstream point at which substances from the site might be transported by the
               tide. If it is difficult to determine exactly how far upstream substances might be
               transported, it may be appropriate to collect background samples above the "head of the
               tide" (i.e., the most upstream point at which tidal cycles are present), as long as it isn't
               too far upstream to be unrepresentative of background. In some cases, a series of
               samples successively farther upstream may be required.

               In tidally influenced areas, it is especially important to be aware of attribution problems
               that might be presented by non-site related sources of contamination either upstream or
               downstream from the PPE. In general, attribution will  be more difficult as distance from
               the PPE increases.

               For aqueous samples, sample collection times in relation to tidal cycles should be
               considered. Hazardous substance transport upstream will be greatest during a rising tide
               and lowest during a failing tide. Background aqueous samples are most likely to have
               the least site-related contamination toward the end of the failing tide, when downstream
               flow is expected to exert maximum flushing effect. Site-related concentrations in the
               background sample are likely to be higher toward the end of the rising tide, when
               contaminated water is carried upstream to the  maximum extent.
Sediment Samples
              Sediment type should be similar in background and release samples. Fine clay particles
              are more likely to adsorb hazardous substances such as metals and hydrophobic organic
              compounds than are larger particles or particles with a predominately sandy matrix.
              Different sediment types tend to accumulate in different areas of a stream or lake. Fine
              sediments will predominate in quiescent zones, whereas sandy sediments, with fewer
              fine particles, will be found in more turbulent areas. Visual documentation of sediment
              type similarity is generally sufficient.
Section 5.2                                      76

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Tissue Samples
              The only tissue samples that may be used to establish an observed release are those
              from essentially sessile, benthic organisms. Such organisms do not need to be human
              food chain species. This ensures that any contamination found in the tissue can be
              attributed to the immediate area in which the organism was collected. Benthic organisms
              are generally those which spend most of their lives on the bottom of a water body, and
              sessile organisms are those which are relatively immobile. Examples of essentially
              sessile, benthic organisms include sponges, oysters, and mussels.

              Concentrations of hazardous substances in tissue samples may vary among different
              species, different individuals within a species, and different organs and tissues within an
              individual organism. At a minimum, background and release tissue samples must be of
              the same species. Ideally, background and release samples should be from organisms of
              similar age,  if age can be determined. If variability among individuals is high, multiple
              background and release samples may be appropriate.
SOIL EXPOSURE PATHWAY


       •      Soil is a heterogeneous material that may vary substantially in texture and other physical
              and chemical properties. Background and release samples should be collected in areas
              with similar soil characteristics.

              Site setting and operational history should be considered in selecting background
              samples. Information about site operations may indicate which areas were subject to a
              particular type of contamination and which areas may serve as background for the
              contaminated areas. Land features might prevent the migration of liquids to certain
              portions of the site. Other contaminated sites nearby may affect the appropriateness of a
              particular location for background samples.

              Some sites may be located in or near areas that have been filled, and the fill soils may
              have come from different locations. If possible, background samples should be from
              undisturbed areas (e.g., those with mature vegetation).

              Soil within a dry drainage ditch or swale is subject to many outside influences and
              generally should not be used for determining background levels. An exception might be
              if the contaminated soil source is in the same swale or drainage ditch.

AIR PATHWAY

       Wind direction is of paramount importance in determining background levels for air samples. A
background air sample will  ideally be collected upwind from the area of contamination. However,
cross-wind samples may also be acceptable for background conditions and should be used if potential
sources of similar contamination are located cross-wind. Consideration must be given to the entire time
period over which a sample was collected.  Data on the predominant wind direction in an area are
insufficient to determine background; wind direction  must be established during the sampling period.

              During any sampling event it is likely that changes in wind speed  and direction will occur.
              A wind rose, based upon continuous data collected during the entire period of site
              sampling, may be helpful for selecting background.

              Background and release samples should be from approximately the same heights above
              the ground surface. Samples do  not need to be collected from the "breathing zone."
              Samples from very low heights should be evaluated carefully because field  activities,
              particularly soil disturbance, may introduce contamination.
                                             77                                      Section 5.2

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              Background and release samples generally should be collected simultaneously.

              Indoor air samples cannot be used to establish background levels (or to establish an
              observed release).

TIPS AND REMINDERS


•      Large differences in the physical or chemical characteristics of background and release samples
       may indicate artifacts introduced during the sampling process. For example, a high concentration
       of suspended solids in  a ground water sample may indicate insufficient purging of the well prior
       to sampling and/or substantial disturbance to the well during sampling.

       Ground water wells from which background and release samples are obtained must be
       completed in the same  aquifer and should generally be at approximately the same relative depth
       in the aquifer.

       Background and release samples should be collected within the same time frame, as appropriate
       for the pathway.

       Background and release sediment (or soil) samples should be of similar type.

       Tidal effects should be  considered when establishing background sampling locations in surface
       water.

       Knowledge of site operations can often provide clues to appropriate locations for background soil
       samples.
Section 5.2                                      78

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SECTION  5.3
TRANSFORMATION
PRODUCTS
       A hazardous substance exposed to other substances or to the environment is susceptible to
transformation by physical, chemical, and biological processes. The products of these reactions are
termed transformation products. Substances found in the environment (i.e., the transformation products)
may be different than those found or otherwise documented in sources at the site (i.e., the parent
substances). This section provides guidance for establishing an observed release (or observed
contamination) based on transformation products.
        Section 2.3
        Section 3.1.1
        Section 4.1.2.1.1
        Section 5.0.1
        Section 6.1.1
 RELEVANT MRS SECTIONS

Likelihood of release
Observed release (ground water)
Observed release (surface water)
General considerations (soil exposure)
Observed release (air)
DEFINITIONS

       Transformation Product: The substance(s) resulting from the transformation of a hazardous
       substance in the environment by physical, chemical, and/or biological processes. The original
       hazardous substance is referred to as the parent substance. When a transformation product is a
       simpler, less complex substance than the parent substance, it is referred to as a degradation
       product. When a more complex substance is produced, the product is often referred to as a
       formation product.

GENERAL REQUIREMENTS

       Most transformation products of environmental concern at waste sites are degradation products.
Examples of physical degradation processes include spontaneous decay of radioactive substances (e.g.,
uranium to radium) and dechlorination of aromatic hydrocarbons due to photodegradation (e.g.,
heptachlorobiphenyl to hexachlorobiphenyl). Examples of chemical degradation processes include
oxidation/reduction reaction of chromium VI to chromium III, acid/base reaction of sulfuric acid to sulfate
salts, and dissolving of metals due to ground water acidification by landfill leachate (e.g., lead solid to
lead ion under low pH conditions). Examples of biological degradation processes include transformation
of trichloroethane to  dichloroethane; hydroxylation of benzenes to phenolics by aerobic microorganisms
(dichlorobenzene to dichlorophenol); and dehalogenation (i.e., removal of a halide) of aromatic
pesticides by anaerobic microorganisms (e.g., pentachlorophenol to tetrachlorophenol).H/gAi//gAif 5-9
provides some examples of common degradation products and their parent substances.
                                           79
                                                                                Section 5.3

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HIGHLIGHT 5-9
TYPICAL DEGRADION PRODUCTS
Parent Substance(s)
Chloromethanes (e.g., carbon tetrachioride)
Chloroethanes (e.g., tetrachloroethane,
trichloroethanes (1,1,1 or 1,1,2),
dichloroethanes, chloroethanes)
Chloroethenes (e.g., tetrachloroethene,
trichloroethene, dichloroethenes vinyl
chloride)
Chlorobenzenes and chlorophenols,
hexachlorobenzene, pentachlorophenols
Polychlorinated biphenyls (PCBs)
DDT
Disulfoton
2,4-Dichlorophenoxyacetic acid (2,4-D)
Aldrin
Typical Degradation Product(s)
Other chloromethanes with fewer chlorines;
formaldehyde; chloroform
Other chloroethanes with fewer chlorines;
chloroethanols; ethanol; chloroethenes
Other chloroethenes with fewer chlorines;
chloroethanols; chloroethanes
Other Chlorobenzenes and chlorophenols
with fewer chlorines; chlorocatachols;
chlorobenzoic acids; phenols
Other PCBs with fewer chlorines;
Chlorobenzenes
DDE, ODD
Carbon disulfide
2,4-Dichlorophenol; 3,5-Dichlorocatechol;
2,4-Dichloromuconic acid
Dieldrin


       The same requirements for establishing an observed release by chemical analysis that apply to
hazardous substances in general apply to transformation products (see Section 5.1). Transformation
products must be hazardous substances in order to be used to establish an observed release (or
observed contamination). Also, an observed release based on transformation products cannot be
established  by direct observation.

ESTABLISHING AN OBSERVED RELEASE (OR OBSERVED
CONTAMINATION) FOR TRANSFORMATION PRODUCTS

       The steps outlined below describe how to establish an observed release (or observed
contamination) for transformation products.

(1)     Document the presence of the transformation product(s) in the release sample at levels
       significantly greater than background. Analytical data used to demonstrate the presence of
       a transformation product must meet the same significance, attribution, and QA/QC
       requirements as for any other hazardous substance (see Section 5.1). The transformation
       products should be considered to be present in the media they have been found in, but this
       does not mean they necessarily are available to other pathways. For example, a
       transformation product detected  in ground water is not necessarily available to the air
       pathway. Any hazardous substance documented to be in a source is considered available to
       all pathways for which the source has a non-zero containment factor value.
Section 5.3
                                           80

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(2)     Attribute the parent substance to the site. Establishing attribution of the parent substance
       to the site usually involves documenting that the parent substance was deposited or is
       present in a source, or that the parent substance was produced, stored, deposited, or treated
       at the site and/or originated in or resulted from activities at the site.

       The following types of information  may be used to establish attribution of a parent substance
        to a site (in order of  preference).

               The most complete information  is chemical analysis of samples from at least one source
               in the site and documentation that the substance was placed in the source.  If the source
               is contaminated soil or contains soil used as cover or fill material, it generally  also will be
               necessary to document that the concentration of the substance in the source is
               significantly above background.

               If the above information cannot be obtained, documentation by chemical analysis that
               the parent substance is in  a source can be used alone if the source does not contain soil
               or if the substance is not a naturally occurring substance.

               If analytical data are not available, records or manifests indicating the parent material
               was placed in a source are preferred. Documentation that the parent substance was
               used, stored, or handled at the  site is also acceptable.

               In some  situations, information  indicating that a parent substance was most likely
               present at a site because of the nature of the site activity may also be considered
               adequate attribution (e.g.,  carbon tetrachloride or tetrachloroethene at a dry cleaning
               facility).

(3)     Attribute the transformation product to the site. Attributing the transformation product to the
       site generally involves documenting that the hazardous substance detected in the receiving
       medium is the transformation product of a parent substance attributable to that site. Establishing
       attribution of a transformation  product to the site usually involves documenting the following.

               The substance detected in a medium is a transformation product of the parent material,
               as shown by:

               —     Site-specific studies on the transformation process by qualified research
                      organizations (e.g., universities, EPA research laboratories);

               —     EPA  technical reports discussing the transformation of the parent substance,
                      such as from the Office of Research and Development, the Risk Reduction
                      Engineering Laboratory (RREL), and/or the Center for Environmental  Research
                      Information (CERI);

               —     Information in data bases containing EPA-reviewed information (e.g., the
                      computerized RREL "Treatability Data Base");

               —     Articles from peer  reviewed journals; or

               —     Textbooks on soil  and environmental microbiology, biotechnology, and
                      biotreatment processes and their effectiveness.

               A significant  increase  of the transformation product relative to its background for the site
               has occurred.
                                              81                                       Section 5.3

-------
               At least some portion of the significant increase of the transformation product above
               background can be attributed to the site.

        Information that would further support attribution (but would not be sufficient by itself) includes:

               Conditions at the site are such that it is possible that the parent material has transformed
               into these substances, or, at minimum, that the conditions at the site do not prevent the
               transformation from occurring (e.g., the transformation requires oxidizing conditions and
               these exist at the site); and

               There is a non-zero containment factor value for at least one source at the site
               containing the parent material.
Section 5.3                                       82

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CHAPTER 6
HAZARDOUS WASTE QUANTITY
   TIER A
   TIERB
   TIERC
   HERD
HAZARDOUS CONSTITUENT
    QUANTITY
HAZARDOUS WASTESTREAM
    QUANTITY
    VOLUME
     AREA
 POUNDS
 POUNDS
CUBIC YARDS
SQUARE FEET

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SECTION  6.1
OVERVIEW OF
HAZARDOUS WASTE
QUANTITY FOR THE
THREE MIGRATION
PATHWAYS
                                                 we
      This section introduces the concept of hazardous waste quantity and provides a flowchart
summarizing how to calculate the hazardous waste quantity factor value for the migration pathways. A
discussion of possible information sources that may assist in documenting hazardous waste quantity
values is also included. Hazardous waste quantity for the soil exposure pathway is discussed
in Section 9.2.

      The purpose of the hazardous waste quantity factor in the MRS is to represent the quantity of
hazardous substances at a site. The hazardous waste quantity factor allows the use of various measures
of hazardous waste quantity depending on data availability and adequacy. The factor has a
hierarchical structure of four tiers:
             Tier A
             TierB
             TierC
             TierD
Hazardous Constituent Quantity
Hazardous Wastestrearn Quantity
Source Volume
Source Area.
      In general, Tier A is the most exact measure of hazardous waste quantity and also requires the
highest level of data to score; successive tiers are less accurate and have less rigorous data
requirements. The hierarchy allows evaluation of a source at the most precise level for which data are
reasonably available, while not requiring extensive data collection where less information is available.
The hazardous waste quantity for each source at a site is determined by evaluating as many of the tiers
as necessary to estimate the mass of hazardous substances for the source (and in any associated
releases from the source). The highest value among the tiers used is then selected as the source
hazardous waste quantity value. The overall pathway hazardous waste quantity factor value is
determined by summing the individual source hazardous waste quantity values, and then assigning a
value using HRS Table 2-6.

      The quantity of hazardous substances in each source generally should be estimated as a specific
number, not a range or qualitative estimate. However,  if data are only available to support a range of
source hazardous waste quantity values, the range can be used. The documentation presented in the
HRS scoring package should clearly demonstrate how the source hazardous waste quantity value was
calculated, and the references should support that demonstration.

      Highlight 6-1 is a flowchart that summarizes the methodology for evaluating hazardous waste
quantity. In addition, flowcharts in subsequent sections provide step-wise instruction for scoring each
individual tier.
                                         83
                                                                            Section 6.1

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cf
a
o
                                                                                                HIGHLIGHT 6-1
                                                      FLOWCHART FOR EVALUATING  HAZARDOUS  WASTE QUANTITY
                                       START
                                     SOURCE #1

                              For the migration pathway being
                                       evaluated
oo
                                                            Do not evaluate hazardous waste
                                                               quantity factor for source.
                                                                Continue to next source.
        Source
      containment
       value >0?
                                                                                             Is hazardous constituent quantity for the
                                                                                             source adequately determined (i.e., total
                                                                                                mass of at CERCLA hazardous
                                                                                             substances in source and releases from
                                                                                               source is known or estimated with
                                                                                                    reasonable confidence?)
                                  TERA
                             Evaluate hazardous
                             constituent quantity
                               for the source.
Can mass of any CERCLA
 hazardous substance be
      determined? i>
                                                                                                                             Is hazardous wastestream quantity for the
                                                                                                                            source adequately determined (Le., total mass
                                                                                                                            of all hazardous wastestreams and CERCLA
                                                                                                                             pollutants and contaminants for source and
                                                                                                                             releases from source Is known or estimated
                                                                                                                                   with reasonable confidence?)
                               Assign mass (in b) of CERCLA
                               hazardous substances, based on
                                 available data, as value for
                                hazardous constituent quantity.
                               Assign source a value of 0 for
                                  hazardous constituent.
                                                                                                            TIERS
                                                                                                  Evaluate hazardous wastestream
                                                                                                      quantity for the source.
                                                                Can mass of any hazardous
                                                               wastestream plus mass of any
                                                                additional CERCLA pollutants
                                                                   and contaminants be
                                                                       determined? *
                                                                                                        Is the source an
                                                                                                          unallocated
                                                                                                            source?
    Assign total mass (in b) of
      CERCLA hazardous
      substances, based on
    available data, as value for
      hazardous constituent
           quantity.

    Assign source a value of 0
    for the wastestream (Tier
    B), volume (Tier C), and
     area (Tier 0) measures.
Assign source
a value of 0
for hazardous
wastestream
quantity.
i
r

NO
Divide total mass (in b)
     of hazardous
  wastestreams plus
CERCLA pollutants and
 contaminants by 5,000
  and assign result as
  value (or hazardous
 wastestream quantity.
Assign source value of 0
for volume (Tier C), and
    area (Tier D).

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                                                                               Divide mass fin Ib) of hazardous wastestream plus
                                                                                CERCLA pollutants and contaminants, based on
                                                                               available data, by 5,000 and assign result as value
                                                                                     for hazardous wastestream quantity.
                                     Can volume of
                                       source be
                                      determined?
                                                        YES
Assign source a value of 0 for
     the area (Tier D).
oo
en
                                               NO
                                                                               TIERC

                                                              Evaluate volume measure using dimensions of
                                                              the source.  Based on volume, assign source a
                                                               value for volume using appropriate Tier C
                                                                       equation (HRS Table 2-5).
                                                                               TIERD

                                                               Evaluate area measure using dimensions of
                                                              source. Based on area, assign source a value
                                                               for area using appropriate Tier D equation
                                                                             (Table 2-5),
VOLUME (V)

Landfill
Surface Impoundment
Surface Impoundment
     (burfecVbackflled)
Drums
Tanks and Containers
    (other than drums)
Contaminated Soil
Pie
Other
                             units
                                                                                                                                             cubic yds     V/2,500
                                                                                                                                             cubic yds     V/2.5
                                                                                                                                             cubic yds     V/2.5
                                                                        gakxis
                                                                        cubic yds
                                                                        cubic yds     V/2,500
                                                                        cubic yds     V/2.5
                                                                        cubic yds     V/2.5
                                           AREA (A)

                                           LandfW
                                           Surface Impoundment
                                           Surface Impoundment
                                               (burfecVbacMIted)
                                           Contaminated Soil
                                           Pile
                                           Land Treatment
                                                                                                                                         units
                        square ft      A/3,400
                        square ft      A/13
                        square ft      A/13

                        square ft      A/34,000
                        square ft      A/13
                        square ft      A/270
                                1 Does not apply to sites containing radronucfdes (ether alone or in combination with other
                                 substances).

                                b Does not include directions for allocating hazardous substances and hazardous wastestreams
                                 to sources (see HRS section 2.4.2).  Does not include needed directions for evaluating RCRA
                                 hazardous wastes under Tiers A and B. (See HRS section 2.4.2.11 and HRS section 2.4.2.1.2.)

                                c Does not include directions for determining the hazardous constituent quantity after a removal
                                 action.  (See HRS section 2.4.22.)
                                                    If hazardous constituent quantity
                                                       (Tter A) is not adequately
                                                   determined for an sources, then this
                                                   factor value is subject to a minimum
                                                    of 10; except if any target for the
                                                     migration pathway is subject to
                                                    actual contamination, this factor
                                                     value is subject to a minimum
                                                                                                                                      END
o>
a
o
                                                                                                        Select highest values assigned to source for
                                                                                                        hazardous constituent quantity, hazardous
                                                                                                        wastestream quantity, and volume or area.
                                                                                                       Assign this highest value as source hazardous
                                                                                                         waste quantity value.  Do not round to the
                                                                                                                     nearest integer.
   Are there
    sources to be
     evaluated?
Sum source hazardous waste
quantity values assigned to al
sources (inducing unallocated
    sources) for migration
pathway being evaluated and
  round this sum to nearest
   integer, except if sum is
 greater than 0, but less than
1, round it to 1. Based on this
   value, assign hazardous
 waste quantity factor value
 for migration pathway using
       HRS Table 2-6.
                                                                         HRS Table 2-8

                                                  Hazardous waste quantity value
                                                  1 to 100	
                                                  Greater than WO to 10,000........
                                                                                             Greaterthan 10,000 to 1,000,000	
                                                                                             Greater thai 1,000,000	
                                                                                                                                                      equation

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                               RELEVANT MRS SECTIONS

        Section 2.4.2              Hazardous waste quantity
        Section 2.4.2.1             Source hazardous waste quantity
        Section 2.4.2.1.1            Hazardous constituent quantity
        Section 2.4.2.1.2            Hazardous wastestream quantity
        Section 2.4.2.1.3            Volume
        Section 2.4.2.1.4            Area
        Section 2.4.2.1.5            Calculation of source hazardous waste quantity value
        Section 2.4.2.2             Calculation of hazardous waste quantity factor value
DEFINITIONS

       Hazardous Waste Quantity Factor Value: An assigned value for the pathway that is based on
       the sum of all source hazardous waste quantity values, and assigned using MRS Table 2-6.

       Source Hazardous Waste Quantity Factor Value:  The highest of the values assigned to a
       source using the four hazardous waste quantity tiers.

BEGINNING THE HAZARDOUS WASTE QUANTITY EVALUATION

       The evaluation of hazardous waste quantity begins with allocation of hazardous substances to
sources and evaluation of containment factor values. These  steps are an extension of source
characterizations, discussed in Section 4.1.

(1)     Allocate hazardous substances to sources.  Review the evidence that hazardous substances
       and/or wastestreams are associated with the site. This information can be retrieved from a
       variety of references. See subsection below, Locating hazardous waste quantity Information.
       These references may indicate which and possibly how much hazardous substances are present.
       To begin evaluating the hazardous waste quantity factor, allocate the substances and
       wastestreams deemed hazardous to specific sources at the site.

(2)     Evaluate an unallocated source, if necessary.  If hazardous substances and/or wastestreams
       are documented as deposited at the site, but cannot be allocated to a specific source,  consider
       them allocated to a separate "unallocated source." Assign the unallocated source a containment
       factor value of greater than 0. In rare circumstances, there may be definitive information that the
       substance or wastestream that cannot be allocated to a specific source could only have been
       placed in sources with  a containment factor value of 0 for a particular pathway; in this particular
       situation, do not evaluate hazardous waste quantity  for these hazardous substances. In all
       situations, only Tier A and Tier B can  be used to  evaluate the unallocated source.

              To begin evaluating hazardous waste quantity, allocate hazardous substances and
              wastestreams at the site to specific sources, to the extent possible. If necessary, assign
              hazardous substances and/or wastestreams to an unallocated source.
Section 6.1                                      86

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(3)     Evaluate pathway-specific containment factor values for each source. To be evaluated for
       hazardous waste quantity, a source must have a containment factor value greater than 0 for the
       pathway being scored. As discussed above, always assume that the unallocated source has a
       containment factor value greater than 0 for all migration pathways. If a source has a containment
       factor value equal to 0,  hazardous waste quantity cannot be evaluated for that particular source
       in that particular pathway.

               To evaluate hazardous waste quantity for a source for a particular pathway, the
               containment factor value for the source must be greater than 0 for that pathway.

       Highlight 6-2 is a matrix that indicates tiers for which hazardous waste quantity data are most
likely to be available for each MRS source type.  For instance, when calculating hazardous waste quantity
for a landfill, it is more likely that data adequate for evaluating Tier D will be available than data
adequate for evaluating Tier A.  Note that the information provided \r\Highlight6-2, although generally
appropriate, may or may not apply to particular sources at a site and is to be used  only for general
guidance.
H
HIGHLIGHT 6-2
DATA AVAILABILITY BY SOURCE TYPE
Source Type
Landfill
Surface
Impoundment
Surface
Impoundment
(buried/backfill)
Drums
Tanks/Containers
Contaminated Soil
Pile
Land Treatment
Other
TIER A
Hazardous
Constituent
Quantity
—
+
—
+
+
—
—
+
—
TIERB
Hazardous
Wastestream
Quantity
+
+
+
++
++
—
+
+
+
TIERC
Volume
+
++
+
++
++
—
++
+
+
TIERD
Area
-
++
++
—
—
++
+
++
++
H+ Likely that data on HWQ will be available.
+ Possible that data on HWQ will be available.
— Unlikely that data on HWQ will be available.

                                              87
                                                                                      Section 6.1

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LOCATING HAZARDOUS WASTE QUANTITY INFORMATION

       Various types of information may be helpful for determining hazardous waste quantity. Although
Tiers A and B require more detailed information, Tiers C and D also require documentation to
substantiate the volume or area being used. It may be necessary to rely on a single particular
recordkeeping reference to estimate hazardous waste quantity, and to incorporate other documents
supporting such an estimate.

              RCRA Waste Manifests. The RCRA Subtitle C program uses the Uniform Hazardous
              Waste Manifest to track the movement of hazardous waste from the point of generation
              to off-site points of treatment, storage, or disposal. RCRA manifests include:

              —     Name and EPA identification number of the generator, transporter(s), and facility
                     where the waste is to be treated, stored, or disposed;

              —     Department of Transportation (DOT) description of the waste being transported;

              —     Quantity of each hazardous waste being transported by units of weight or
                     volume; and

              —     Address of the treatment, storage, or disposal facility to which the generator is
                     sending waste.

              For purposes of hazardous wastestream quantity, RCRA manifests are most useful when
              the site being scored is (or was) a RCRA treatment, storage or disposal facility; then,
              manifests document the types and quantities of waste that have been  received. If the
              site being scored is a generator of RCRA hazardous wastes that were transported
              off-site, manifests can be used to document the quantity of waste generated.

              State Manifests. Many states impose additional or more stringent regulations that
              require the manifesting of materials/wastes other than RCRA Subtitle C wastes.
              Although each  state's requirements vary, investigating state manifests may be helpful in
              scoring hazardous waste quantity.

              Permits. Permits may provide helpful information about a site. Permits, however,
              establish levels that should be compiled with and not levels that actually occur at the
              site. Any permits  used to provide information must be signed and finalized. Permits are
              rarely used as the only supporting documentation for actual hazardous waste quantity at
              a site. However, permits can provide supporting documentation to allocate certain
              hazardous substances to a wastestream (e.g., support the presence of benzene in a
              wastewater discharge under a National Pollution Discharge Elimination System (NPDES)
              permit).

              EPA Compliance Orders. EPA signed and finalized compliance orders may provide
              information relevant to hazardous waste quantity. For example, a violation of a NPDES
              permit may be used to document that certain concentration levels of hazardous
              substances were actually released.
Section 6.1                                      88

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              Section 10(k) Reports. The Securities and Exchange Commission requires section
              10(k) reports that may contain detailed information related to hazardous waste quantity.
              The section 10(k) report, a version of the annual report that all U.S. corporations must
              file with the Securities and Exchange Commission, frequently contains more information
              on the  company's assets and liabilities (e.g., hazardous waste) than the annual report
              distributed to stockholders.

              CERCLA 103(c) "Notification of Hazardous Waste Site" Forms. These forms are a
              direct source of waste quantity information. If a facility stored, treated, or disposed of
              hazardous substances before (and during) 1980, then the owner/operator was required to
              submit a CERCLA 103(c) "Notification of Hazardous Waste  Site" form. This form
              provides the amount and types of hazardous substances on the site,  as well as any
              known, suspected, or likely releases of such substances from the facility.

              PRP Records. At sites where PRPs have been identified, PRP records of
              incoming/outgoing wastes may be used to estimate the hazardous waste quantity at a
              site.

              Property Owners' Tax Assessment Documents. Property owners' tax assessment
              documents may contain some useful information.

              Emergency Response Monitoring Data. The scorer might find relevant information in
              this general source.

              Material Safety Data Sheets. This source can provide limited information such as
              chemical properties, Chemical Abstract Service number, percent technical grades and
              safe handling procedures.

              Other  Records. In addition, numerous other records may be used to estimate the
              hazardous waste quantity at a site. A facility's product records, annual reports, property
              records, and production reports may be useful, as may trade association information,
              transcripts of interviews with former employees, and aerial photographs. Completeness,
              accuracy, and validity of these information sources varies and should be evaluated on a
              case-by-case basis.

TIPS AND REMINDERS

       Some scorers find it helpful to start evaluating hazardous waste quantity under Tier D and then
       work backward to Tier A. In certain situations (e.g., landfills, manufacturing sites), this method
       makes it easier to recognize which tier should be used to evaluate hazardous waste quantity.

       Incomplete information on a  higher tier can at times score higher than complete information on
       lower tiers.

       Adequate references should be included for all tiers evaluated for the hazardous waste quantity
       factor. At a minimum, references should support the tier(s) used to score the  source and also at
       least one tier both below and above (e.g.,  if Tier B is used, references should also be  provided
       for Tier C or D, and Tier A if scored). This provides usable data for these other tiers if the
       assumptions used during evaluation of the tier do not hold up. Note  that although Tier A or Tier B
       may be adequately determined in some  situations, it may be advisable to  include references for
       Tier C or Tier D.

       Additional  sampling generally will not be performed to obtain Tier A  data.  Instead, use a different
       tier as the  basis of the source hazardous waste quantity value.
                                             89                                      Section 6.1

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       Hazardous waste quantity is a measure of the hazardous substancesdeposited in sources at the
       site rather than a measure of hazardous substances in sources at the site. Therefore, the
       hazardous substances in the sources and in the releases from those sources are evaluated for
       hazardous waste quantity.

       The unallocated source is not used in scoring factors other than hazardous waste quantity. An
       unallocated source results when a hazardous substance or hazardous wastestream is known to
       have been deposited at the site but cannot be allocated to any specific source.

       Do not confuse the unallocated source with sources that are  "ground water plumes (or surface
       water sediments) with no identified source."

       For an  unallocated source, only Tier A or Tier B can be used to evaluate the hazardous waste
       quantity.

       The most reasonable and defensible estimate of hazardous waste quantity should always be
       applied for each of the tiers used for calculating hazardous waste quantity, regardless of whether
       the estimate is based on the most recent or highest figures.
Section 6.1                                       90

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SECTION 6.2
TIER A-
HAZARDOUS
CONSTITUENT  QUANTITY
                                                                             we
       This section clarifies the method for evaluating hazardous waste quantity under
Tier A of the MRS. Topics include definitions that pertain to Tier A, data requirements for scoring under
Tier A, data sources that can provide hazardous waste quantity information, and evaluation of RCRA
wastes.

       Tier A is used when data are available on the quantities of individual CERCLA hazardous
substances. If complete data are available for the evaluation, Tier A yields the most accurate measure of
the mass of CERCLA hazardous substances in the source. Any data that provide quantities of CERCLA
hazardous substances deposited into a particular source are ideal for evaluating Tier A. However,  in
many cases, a representative value for the average concentration of CERCLA hazardous substances
present in a source will not be adequately documented or obtain able. Highlight 6-3 is a flowchart that
provides step-wise instructions for scoring a source with Tier A.

DEFINITIONS

       Adequately Determined (for purposes of Tier A only): The total mass of all CERCLA
       hazardous substances in the source and releases from the source (or for the area of observed
       contamination) is known or is estimated with reasonable confidence. (For the site hazardous
       waste quantity factor value to be adequately determined for Tier A, this definition must apply for
       all sources.)

       CERCLA Hazardous Substances: Hazardous substance as defined by statute in CERCLA
       section 101 (14); the list of CERCLA hazardous substances having reportable quantities is found
       in 40 CFR 302 in Table 302.4.

       Hazardous Constituent Quantity: The mass (in pounds) of CERCLA hazardous substances
       allocated to a source (with certain exceptions for RCRA wastes).

       Hazardous Substances: CERCLA hazardous substances and pollutants or contaminants as
       defined in CERCLA sections 101  (14) and 101 (33), except as otherwise specifically noted in the
       HRS.

A1.    LOCATING DATA

       The following records or resources, which are described in more detail in Section 6.1, can
provide accounts of quantities of hazardous substances deposited into sources:

             Manifests
             PRP records
             State records
             EPA signed and finalized compliance orders
             Material Safety Data Sheets (for product)
             Permits
             Waste concentration data (see discussion in A2).
                                         91                                  Section 6.2

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                                                       HIGHLIGHT 6-3
                                    FLOWCHART FOR  EVALUATING TIER A
                                   START
                                 SOURCE *1

                          Source with containment factor
                                   value > 0
                               (See Section 6.1)
                         Compile Information on constituent
                           data of CERCLA hazardous
                                  substances.
                                   (See A1)
                                                           Are volume, density, and
                                                              concentration data
                                                             available to determine
                                                             hazardous constituent
                                                                 quantity?
   Can mass of any
 CERCLA hazardous
    substances be
     determined?
                                                                                          Evaluate and use
                                                                                        concentration data, as
                                                                                            appropriate.
                                                                                             (See A2)
Assign source a value of
   0 for hazardous
  constituent quantity.
                                                                                         Evaluate hazardous
                                                                                      constituent quantity using
                                                                                      the exceptions for RCRA
                                                                                             wastes,
                                                                                             (See A3)
                                 Are RCRA hazardous
                                   wastes present In
                                       source?
                                                             Calculate hazardous
                                                            constituent quantity for
                                                                   source.
                                                                                        Assign total mass (in Ib)
                                                                                        of CERCLA hazardous
                                                                                        substances as value for
                                                                                         hazardous constituent
                                                                                              quantity.
     Assign mass (in Ib) of
                                     Is hazardous
                                  constituent quantity
                                 adequately determined
                                     for source?
                                   (See A4 and A5)
CERCLA hazardous
substances, based on
                                  value for hazardous
                                                                                        Assign source a value of
                                                                                        0 for Tier B, Tier C, and
                                                                                               Tier D.
      constituent quantity.
                                 Evaluate source with
                                  Tier B (hazardous
                                wastestream quantity).
                                   (See Section 6.3)
Section 6.2
                                                                 92

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       The hazardous constituent quantity is evaluated based solely on the mass of CERCLA
hazardous substances present in the source (with certain exceptions for RCRA wastes). The mass of
CERCLA pollutants or contaminants, if any, are not included. MRS Table 2-5 designates hazardous
constituent quantity as C - the mass in pounds of CERCLA hazardous substances. No further
calculations are required (e.g., no divisors).

A2.    USING CONCENTRATION  DATA

       To use concentration data to calculate the  hazardous constituent quantity, the following must be
true:

              Volume and density of the source (or portion of the source) are known with reasonable
              confidence; and

              Concentration data are representative of the source (or portion of the source).

       If concentration data meet the above criteria, the following equation can be used to calculate the
hazardous constituent quantity:
                         HCQ8Z C, xDM x  Vs
       where:     HCQS  =   hazardous constituent quantity for source S (mass)

                 Cj     =   average concentration of CERCLA hazardous substance i (mass/mass)

                 n      =   total number of CERCLA hazardous substances

                 DM     =   density of source medium (mass/volume)

                 Vs     =   volume of source S (volume)

       The equation can be modified to estimate the quantity of hazardous constituents in a portion of
the source or in different media within a source. Note that when concentration data are available for
some but not all hazardous substances in a source, the equation can still be used and a hazardous
constituent quantity value determined under Tier A; in such cases, however, the scorer would have to
proceed to Tier B because scoring under Tier A would be incomplete.

       Highlight 6-4 presents some sample scoring examples for the hazardous constituent quantity
evaluation.

A3.    EVALUATING RCRA HAZARDOUS WASTES

       The MRS provides exceptions when calculating hazardous constituent quantity for certain RCRA
hazardous wastes. For MRS purposes, the presence of RCRA hazardous wastes is usually documented
through manifests or other PRP records. It is not the intent of the SI to sample in order to determine the
presence of RCRA hazardous wastes.  If RCRA hazardous wastes are evaluated for hazardous
constituent quantity, evidence supporting their presence must be provided and documented. The next
section provides background about the classification scheme for RCRA hazardous wastes, and the MRS
scoring instructions.
                                            93                                    Section 6.2

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                                        HIGHLIGHT 6-4
                            SCORING EXAMPLES FOR TIER A

      Scenario 1     1,000 gallons of pure toluene were found In 19 drums onsite. (The density of toluene
                    is 7.2 Ibs/gallon.) These 19 drums are the only source at the site.
                    Hazardous Constituent Quantity:
                    1,000 gallons   x   7.2 Ib/gallon =       7,200 Ib
                    Hazardous constituent quantity |s adequately determined for this source.
      Scenario 2     1,000 gallons of pure toluene leaked onto the ground at a site. The source of this
                    information is an emergency response notification report. The spill area is the only
                    source at the site.
                    Hazardous Constituent Quantity:
                    1,000 gallons   x   7.2 Ib/gallon =       7,200 Ib
                    Hazardous constituent quantity |s adequately determined for this source.
      Scenario 3     1,000 gallons of pure toluene were spilled onto the ground onsite; 1,000,000 pounds
                    of soil were excavated to clean up the spill; the excavated soil was placed in a waste
                    pile on the site. The site is located In a deserted industrial  park and it is  not known
                    whether other sources exist.
                    Hazardous Constituent Quantity:
                    1,000 gallons   x   7.2 Ib/gallon =       7,200 Ib
                    Hazardous constituent quantity is not adequately determined - other
                    substances may have been present In the soil priorto the spill. The other
                    tiers need to  be evaluated.
      Scenario 4     1,000 gallons  of pure toluene  mixed with  1,000,000 gallons  of process water
                    discharged to a settling surface impoundment.
                    Hazardous Constituent Quantity:
                    1,000 gallons   x   7.2 Ib/gallon =       7,200 Ib
                    Hazardous constituent quantityis_not adequately determined - other substances may
                    be present In the process water. The other tiers need to be evaluated.
                    All mass is converted to pounds. In each scenario the source HWQ value is 7,200.

Section 6.2
                                                94

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BACKGROUND AND DEFINITIONS

       RCRA, an amendment to the Solid Waste Disposal Act (SWDA), was enacted in 1976 to
manage the large volumes of solid wastes being generated, including certain municipal and industrial
wastes. Subtitle C of RCRA establishes a system for managing hazardous wastes.

       The RCRA regulations in 40 CFR 261 specify that a solid waste is a RCRA hazardous waste if
 it is not excluded from regulation, and it either:

              Exhibits any of the characteristics of a hazardous waste (known as characteristic
              hazardous waste); or

              Has been listed as a hazardous waste in the RCRA Subtitle C regulations (known as
              listed hazardous waste).

       For purposes of the RCRA Subtitle C regulations, a solid waste is any discarded material
(solid, semisolid, liquid, and contained gas) that is not excluded under SWDA.

       RCRA characteristic wastes.  EPA  has identified four characteristics for hazardous waste. Any
solid waste that exhibits one or more of these characteristics is classified as a RCRA hazardous
waste:

              Ignitability (40 CFR 261.21);

              Corrosivity (40 CFR 261.22);

              Reactivity (40 CFR 261.23);  or

              Toxicity (40 CFR 261.24; determined either by the Toxicity Characteristic Leaching
              Procedure (TCLP) or Extraction Procedure (EP)).  (Note that the transition from the EP
              to the TCLP occurred between 1990 and 1991.)

       Guidelines defining each of these characteristics are contained in the CFR citations.

       RCRA listed wastes. A solid waste is a RCRA hazardous waste if it is named on one of the
lists developed by EPA:

              Nonspecific source wastes  (40 CFR 261.31, also called F" list  wastes) - generic
              wastes, commonly produced by manufacturing and industrial processes. Examples
              include spent halogenated solvents used in degreasing and wastewater treatment
              sludge from electroplating processes.

              Specific source wastes (40  CFR 261.32, also called K" list wastes) - wastes from
              specifically identified industries such as wood preserving, petroleum  refining, and
              organic chemical manufacturing. These wastes typically include sludges, still bottoms,
              wastewaters, spent catalysts, and residues.

              Commercial chemical products (40 CFR 261.33(e) and (f), also called P" and "U" list
              wastes) - specific commercial chemical products or manufacturing intermediates.
              These products are considered hazardous wastes when discarded.

       EPA developed these listed wastes by examining different types of wastes and chemical
products and  by determining if any of the following criteria were met:

              Exhibits one of the four characteristics of a hazardous waste (Hazard Codds;for
              ignitability),C (for corrosivity),R (for reactivity), andE (for toxicity));
                                            95                                     Section 6.2

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              Is acutely toxic or acutely hazardous (Hazard Code H); or

              Is otherwise toxic (Hazard CodeT).

These criteria and associated codes are listed in 40 CFR 261.30(b). For a particularlisted waste, one
or more of the hazard codes are assigned as the basis for listing that waste (in 40 CFR 261.31,
261.32, and 261.33).

SPECIAL CONSIDERATIONS FOR CALCULATION OF HAZARDOUS CONSTITUENT QUANTITY

       For a RCRA characteristicwaste that exhibits only the characteristic of toxicity (either TCLP or
EP), only the mass of constituents in the hazardous waste that are CERCLA hazardous substances
are included in the hazardous constituent quantity.

       For a RCRA characteristicwaste that exhibits any characteristic other than toxicity  (including
any other characteristic plus the characteristic of toxicity), the entire mass of the  hazardous waste is
included in the hazardous constituent quantity.

       For hazardous constituent quantity for a RCRA listed waste that is listed solelyfor Hazard
Code T, only the mass of constituents in the hazardous waste that are CERCLA hazardous
substances is included in the hazardous constituent quantity.

       If the RCRA  listed waste is listed for any other Hazard Code (including T plus any  other
Hazard Code), then the mass of the entire hazardous waste is included in the hazardous constituent
quantity.

       Highlight 6-5 is a flowchart that enables scorers to decide which  situation applies.

A4.    CALCULATING HAZARDOUS CONSTITUENT QUANTITY

       At  this point in the hazardous waste quantity evaluation, the scorer needs to answer the
following question for the source:

       Is the hazardous constituent quantity adequately determined? That is, is the total mass  of all
       CERCLA hazardous substances in the source and associated releases from the source known
       or  estimated with reasonable confidence?

              If the answer to the question is YES:

              —     Assign the total mass (in pounds) of CERCLA hazardous substances as the
                     value for hazardous constituent quantity. Assign the other three tiers (hazardous
                     wastestream quantity, volume,  and area) values of 0 for the source.

              —     Assign the hazardous  constituent quantity value as the source hazardous waste
                     quantity value. (Do  not round to the nearest integer.)

              If the answer to the question isNO:

              —     Assign the total mass (in pounds) of the CERCLA hazardous substances, based
                     on the available data,  as the value for hazardous constituent quantity.

              —     Continue the hazardous waste quantity evaluation for this source. See Section
                     6.3 for guidance on evaluating Tier B.
Section 6.2                                    96

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                                      HIGHLIGHT 6-5
          FLOWCHART FOR EVALUATING RCRA HAZARDOUS WASTES
                                      UNDER TIER A
             START
            SOURCE #1

        RCRA hazardous waste has
           been identified
          Is RCRA hazardous
           waste a listed or
          characteristic waste?
         Is listed waste assigned
          Hazard Code T only?
    Does waste eaiibl
  characteristic of toxicity
  Entire mass of hazardous
wastes Is included in hazardous
   constituent quantity.
 Only mass of constituents in
  hazardous waste that are
   CERCLA hazardous
  substances are included in
hazardous constituent quantity.
TIPS AND REMINDERS

       The scorer is unlikely to find information to adequately determine the hazardous constituent
       quantity. Tier A (hazardous constituent quantity) can be used to evaluate hazardous waste
       quantity if the mass of some CERCLA hazardous substances in the source or in releases from
       the source is known. Even if Tier A isnot adequately determined, it may result in a higher value
       than the other tiers.

       Include the mass of all deposited CERCLA hazardous substances, even if they have migrated, in
       calculating hazardous constituent quantity for the source.

       When evaluating Tier A, only CERCLA defined hazardous substances are used; CERCLA
       defined  pollutants and contaminants are not used. However, CERCLA hazardous substances,
       pollutants, or contaminants can be used in all other waste characteristics factor evaluations,
       including waste quantity evaluations using Tiers B, C, and D.

       The most reasonable and defensible estimate of hazardous waste quantity should always be
       applied for each of the tiers used for calculating hazardous waste quantity, regardless of whether
       the estimate is based on the most recent or highest figures.
                                             97
                                                                                    Section 6.2

-------
       Do not subtract background levels for hazardous substances before calculating hazardous
       constituent quantity, except for radioactive substances.

       Sampling data can only be used to extrapolate hazardous constituent quantity if the source is
       documented to be homogeneous.

       Mining wastes generally should not be considered "homogeneous," particularly since ores and
       mining processes change overtime.

       Tier A can be used where representative concentration data are available from sampling or
       manifest data. However, sampling to determine hazardous constituent quantity is typically
       beyond the scope of the SI. For some sites, sampling conducted by other parties (e.g., PRPs or
       states) may be sufficient to score Tier A.

       Drums, tanks, and containers are examples of source types most likely to have Tier A data.

       For Tier A, RCRA listed or characteristic hazardous wastes are given special consideration. For
       certain RCRA waste codes, only the mass of constituents in the hazardous waste that are
       CERCLA hazardous substances are included in the hazardous waste quantity.

       Unless there is evidence that products have spilled or been abandoned,  the total volume of
       tanks, drums, or containers containing  product should not be used to determine hazardous
       constituent quantity.

       For the site hazardous waste quantity factor value to be adequately determined, the hazardous
       waste quantities for all the sources must be adequately determined.
Section 6.2                                    98

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SECTION 6.3
TIERB —
HAZARDOUS
WASTESTREAM
QUANTITY
mrr
                                                                            we
       This section clarifies the method for
evaluating hazardous waste quantity under Tier B of the MRS. Topics include definitions that pertain to
Tier 8, data requirements for scoring under Tier B, evaluation of RCRA wastes, and extrapolation of
data.

       Tier B is used when Tier A data are not adequately determined and when wastestrearn and/or
CERCLA pollutant and contaminant data are available. This tier deals with wastes "as deposited", as
does Tier A. Highlight 6-6 is a flowchart that provides step-wise instructions for scoring a source with
TierB.

DEFINITIONS

       Adequately Determined (for purposes of Tier B only): The total mass of all hazardous waste
       streams and CERCLA pollutants and contaminants for the source and releases from the source
       (or for the area of observed contamination) is known or is estimated with reasonable confidence.
       (For the site hazardous waste quantity to be adequately determined for Tier B, this must apply
       for aN sources.)

       CERCLA Pollutant or Contaminant: Section 101  (33) of CERCLA states that: "pollutant or
       contaminant shall include, but not be limited to, any element, substance, compound, or mixture,
       including disease-causing agents, which after release into the environment and upon exposure,
       ingestion, inhalation, or assimilation into any organism, either directly from the environment or
       indirectly by ingestion through food chains, will or may reasonably be anticipated to cause death,
       disease, behavioral abnormalities, cancer, genetic mutation, physiological malfunctions (including
       malfunctions in reproduction) or physical deformations, in such organisms or their offspring,
       except that the term "pollutant or contaminanr shall not include petroleum,  including crude oil or
       any fraction thereof which is not otherwise specifically listed or designated as a hazardous
       substance under subparagraphs (A) through (F) of paragraph (14) and shall not include natural
       gas, liquefied natural gas, or synthetic gas of pipeline quality (or mixtures of natural gas and such
       synthetic gas)."

       Hazardous Waste Stream:  Material containing CERCLA hazardous substances as defined in
       CERCLA section 101 (14), that was deposited, stored, disposed, or placed in, or that otherwise
       migrated to, a source.

B1.    LOCATING DATA

       The following  records or resources usually provide direct accounts of hazardous wastestreams:

             Manifests
             PRP and state records
             Permits.
                                          99
                                                                               Section 6.3

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                                                        HIGHLIGHT 6-6
                                     FLOWCHART FOR EVALUATING TIER  B
                                                                   START
                                                                 SOURCE *1

                                                          Source with containment factor
                                                                  value > 0.
                                                               (See Section 6.1)
                                                             Compile information on
                                                            hazardous wastestreams,
                                                           including CERCLA pollutants
                                                               and contaminants.
                                                                  (See B1)
                                                           Can mass of any hazardous
                                                            wastestreams or mass of
                                                             CERCLA pollutants and
                                                           contaminants be determined?
                                                            If needed and appropriate,
                                                           extrapolate data to estimate
                                                         hazardous wastestream quantity.
                                                                   (SeeB3)
                                                         Calculate hazardous wastestream
                                                              quantity for source.
                                                                  (See B4)
                                                                 Is hazardous
                                                             wastestream quantity
                                                             adequately determined?
                                                                  (See B5)
                            Evaluate source with
                                  Tier C.
                              (See Section 6.4)
                                                           Divide total mass On Ib) of
                                                          hazardous wastestreams plus
                                                            CERCLA pollutants and
                                                         contaminants, based on available
                                                         data, by 5,000 and assign this as
                                                              value for hazardous
                                                             wastestream quantity.
 Divide total mass (In Ib)
     of hazardous
  wastestreams plus
CERCLA pollutants and
 contaminants by 5,000
and assign this as value
    for hazardous
 wastestream quantity.
                                                                                        Assign source a value of
                                                                                        0 for Tier C and Tier D.
Section 6.3
                                                                 100

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       To evaluate Tier B for hazardous wastestream quantity for a source, the following must be true:

              The mass of any hazardous wastestream or the mass of any additional CERCLA
              pollutants and contaminants allocated to the source are  known.

              Hazardous constituent quantity (Tier A) was not adequately determined for that source.

MRS Table 5-2 designates the hazardous wastestream quantity &&/. Once this  mass (in pounds) is
determined, assign the source a value for hazardous wastestream quantity by dividilrtgby 5,000.

B2.    EVALUATING RCRA HAZARDOUS WASTE

       Under Tier B, RCRA hazardous wastes are treated the same as  all other hazardous
wastestreams. For a wastestream that consists solely of RCRA listed wastes or RCRA characteristic
wastes, the mass of the entire hazardous wastestream is used to calculate hazardous wastestream
quantity. (Note that RCRA hazardous wastes under Tier B are treated differently than under Tier A (see
Section 6.2)).

B3.    EXTRAPOLATING DATA

       Scorers should employ data that support the most accurate estimate of hazardous wastestream
quantity for each source. Generally, the best data to use are those that document wastestream disposal
over the longest time period. If information is available for only one year, extrapolating that information
to multiple years may be acceptable, depending on the documentation available to support the required
assumptions. Extrapolating short-term wastestream data over much longer periods (e.g., six months of
data extrapolated over 20 years of operation) is generally not acceptable.

       The following may provide information to document the extrapolation  of wastestream data over a
longer period:

              Property records
              Production reports
              NPDES signed and finalized permits
              EPA signed and finalized compliance orders
              RCRA manifests
              Annual  reports
              Tax records
              Interviews with former employees
              The Kirk-Othmer Encyclopedia of Chemical  Technology  (this reference provides
              information on constituents normally present in certain process wastestreams, and can
              be used to support reasonableness  of data)
              Effluent guidelines documents
              Trade association information
              Industry studies and data bases from EPA's  Office of Solid Waste.

       If there is sufficient evidence supporting the assumption that a discharge for a particular day was
typical, a discharge estimate based on that day may be sufficient basis for estimating discharge over the
entire year. For example, the scorer could  verify that the production figure is reasonable for the industry
as a whole. The scorer would also need to know the typical number of days of operation per year. In
addition, the scorer needs to provide a convincing argument that the extrapolated value being used is
defensible. Information about continuity of the plant operations could be included in the argument,
especially if data are extrapolated over time. For example,  if the  plant was bankrupt or the local
economy depressed for a portion of the time period, that would need to  be documented and
                                           101                                    Section 6.3

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considered in the calculation. General industry or local economy descriptions could be included as
further evidence of reasonable estimates.

B4.    CALCULATING HAZARDOUS WASTESTREAM QUANTITY

       At this point in the hazardous waste quantity evaluation, the scorer needs to answer the following
question:

       Is the hazardous wastestream quantity adequately determined for the source? That is, is the total
       mass of all hazardous wastestreams and any additional CERCLA pollutants and contaminants in
       the source and associated releases from the source known or estimated with reasonable
       confidence?

              If the answer to the question is YES:

              S      Sum the total mass (in pounds) of hazardous wastestreams plus any
                    additional CERCLA  pollutants  and contaminants and divide the sum by 5,000.
                    This result is the hazardous  wastestream quantity value. Assign the source a
                    value of 0 for the Tier C (volume) and Tier D (area) measures.

              S      Select the highest of the values assigned to the source for hazardous constituent
                    quantity and hazardous wastestream quantity as the value for the source
                    hazardous waste quantity value (do  not round to the nearest integer).

              If the answer to the question is NO,  and the  source is not an unallocated source:

              S      Sum the mass (in pounds) of hazardous wastestreams plus any additional
                    CERCLA pollutants  and contaminants, based on the available data, and divide
                    the sum by 5,000. Assign the result as the value for hazardous wastestream
                    quantity.

              S      Evaluate Tier C for this source.

       S      If the answer to the question is NO,  and the  source is an unallocated source:

              S      Sum the mass (in pounds) of hazardous wastestreams plus any additional
                    CERCLA pollutants  and contaminants based on available data and divide the
                    sum by  5,000. This result is  the hazardous wastestream quantity value.
                    Assign the source a value of 0 for the Tier C (volume) and Tier D (area)
                    measures.

              S      Select the highest of the values assigned to the source for hazardous
                    constituent quantity and hazardous wastestream as the source hazardous
                    waste quantity value. (Do  not round  to the nearest integer).

TIPS AND REMINDERS

       Tier B can be used to evaluate hazardous waste quantity if the mass of some hazardous
       wastestream is known;  the total mass of all wastestreams need not be  determined in order to
       evaluate Tier B.

       Wastestreams can be liquid, sludge, or solid (e.g., wastewater, slag pile).

       Tier B is based on the actual contents of the source not on its hypothetical capacity (e.g., weight
       or volume of contents actually in tank is used, not volume of tank). Tier C or D would involve the
       capacity of the tank.


Section 6.3                                   102

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Drums, tanks, containers, surface impoundments, and waste piles are examples of source types
most likely to have Tier B data.

If long-term information regarding waste disposal at the site is not available, short-term data
regarding waste disposal may be extrapolated to a longer time period depending on the
documentation available to support the required assumptions. However, extrapolating short-term
data over very long periods of time (e.g., six months of data extrapolated over 20 years  of
operation) is generally not acceptable.

Tier B treats RCRA hazardous wastes identical to other hazardous wastes.

Process models can sometimes be used to estimate hazardous wastestrearn quantity. However,
convincing evidence must be presented to demonstrate the applicability of the assumed process
flows to the source being scored.

When extrapolating wastestrearn data, if the Tier B calculation assumes constant and continuous
production levels, the rationale for this assumption needs to be included in the documentation
record.

One way to support a Tier B estimate of wastestrearn quantity is to assume a certain number of
batch processes per year, when the approximate mass of hazardous waste produced is known
per batch.
                                     103                                    Section 6.3

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SECTION 6.4
TIER C -
VOLUME
*mrr\
                                                                             we
       Tier C of the MRS is used when the volume of the source can be determined. Tier C cannot be
used for the unallocated source. MRS Table 2-5 designates volume as V. Highlight 6-7 is a flowchart
that provides step-wise instructions for scoring a source with Tier C.

C1.    LOCATING DATA

       The following may provide accounts of the source volume (i.e., capacity):

             PRP data
             State records
             Property records
             EPA signed and finalized compliance orders
             Permits
             Aerial photographs.

       To calculate the volume of the source, all of the following must be true:

             The volume of the source can be estimated.

             The hazardous constituent quantity and/or hazardous wastestrearn quantity were not
             adequately determined for the source.

C2.    CALCULATING VOLUME

       If the volume of the source can be estimated:

       (1)    Evaluate the volume measure using the dimensions for the source type, specified
             in MRS Table 2-5. This measure can be obtained by using the engineered capacity
             for certain source types (e.g., landfills) or the maximum volume for source types that
             are not specifically engineered (e.g., piles, quarries).

       (2)    Based on the volume, assign the source a value for volume using the appropriate
             Tier C equation found in MRS Table 2-5.

       (3)    Assign the source a value of 0 for the area measure (Tier D). Select the highest of
             the values assigned to the source (hazardous constituent quantity, hazardous
             wastestrearn quantity, and volume) as the source hazardous waste quantity value.
             (Do not round to the nearest integer.)

       If the volume of the source cannot be determined:

       (1)    Assign the source a value of 0 for Tier C.

       (2)    Evaluate Tier D for this source.
                                          105
                                                                               Section 6.4

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                                                       HIGHLIGHT 6-7
                                    FLOWCHART FOR  EVALUATING  TIER C
                                                                           START

                                                                  Source with containment factor
                                                                     valuB greater than zero.
                                                                        (See Section 6.1)
                                                       YES
                                                      YES
  Was hazardous constituent
quantity (Tier A) or hazardous
wastestream quantity (Tier B)
   adequately determined?
                                                                Compile Information on volume of the
                                                                            source.
                                                                           (Seed)
                                                                  Can the volume of the source be
                                                                          determined?
                                                                                 YES
                                                                Calculate volume for the source and
                                                                         designate as V.
                                                                           (See C2)
                                                    Use the appropriate equation below (adapted from Table 2-5) to assign
                                                    the source a value for volume.

                                                    Volume (V)

                                                    Landfill                           cubic yards  V/2,500
                                                    Surface Impoundment                cubic yards  V/2.5
                                                    Surface Impoundment (bured/backfilled)   cubic yards  V/2.5
                                                    Drums                            gallons      V/500
                                                    Tanks and Containers (other than drums) cubic yards  V/2.5
                                                    Contaminated soil                   cubic yards  V/2,500
                                                    Pile                              cubic yards  V/2.5
                                                    Other                            cubic yards  V/2.5
Section 6.4
                                                                106

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TIPS AND REMINDERS

       TierC is based on capacity, not the actual contents of the source (e.g., use the total drum
       volume, not the volume of the waste when deposited; use the surface impoundment once-filled
       volume, not the volume of the waste disposed of in the impoundment).

       Use Tier C for containerized source types (e.g., drums, tanks) and for source types with
       reasonably well-defined horizontal and vertical boundaries (e.g., waste piles).

       Subsurface source types generally need engineered drawings to support volume calculations
       (e.g., landfills, buried surface  impoundments). Obtaining  representative depth measurements of
       these source types during the SI is not recommended. Geophysical surveys generally should not
       be used to document source volume.

       Waste permit applications often include waste unit designs specifying volume capacity.

       Tier C is not applicable for unallocated sources.

       For a quarry, Tier C volume measures cannot be assumed to be equal to the volume of the filled
       quarry unless there is a reasonable basis for making that assumption. The scorer should attempt
       to estimate the level at which the waste accumulated in the quarry. For dry quarries or quarries
       where waste has migrated,  the scorer should look for indicators of the previous maximum depth
       of wastes (such as contaminated waterlines). Volume may be calculated based on this depth. If
       the scorer cannot establish  that waste was historically deposited to a certain depth, calculate
       hazardous waste quantity based on current conditions (i.e., using Tiers A, B, and D, as
       appropriate).
                                            1 07                                    Section 6.4

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SECTION  6.5
TIER D -
AREA
       Tier D is used when data on the surface area of
the base of a source are available. Tier D assumes a
default depth for each source and, thus, provides a less reliable estimate than when the depth of a
source can be estimated. Thus, Tier D is not used when Tier C can be used. Aerial photographs,
especially historical photographs, are particularly helpful in evaluating this tier. Tier D should be used for
source types without reasonably well-defined vertical boundaries (e.g., contaminated soil, landfills').Tier
D cannot be used for unallocated sources MRS Table 2-5 designates area as/A.. Highlight 6-8 is a
flowchart that provides step-wise instructions for scoring Tier D.

D1.    LOCATING DATA

       The following may provide accounts of the areas of sources containing hazardous substances:

              PRP data
              State data
              Property records
              EPA signed and finalized compliance orders
              Permits
              Aerial photographs.

       To calculate the area of the source, all of the following  must be true:

              The area of the source (or a portion of the area) can be estimated.

              The source was not assigned a value for volume.

              The hazardous constituent quantity and/or hazardous wastestrearn quantity were not
              adequately determined for the source.

D2.    CALCULATING AREA

       If the area of the source (or a portion of the area) can be determined:

       (1)     Evaluate area using the required dimensions for the source type, specified in MRS
              Table 2-5.

       (2)     Based on the area, assign the source a value for area using the appropriate Tier D
              equation found in MRS Table 2-5.

       (3)     Select the  highest of the values assigned to the source (hazardous constituent
              quantity, hazardous wastestrearn quantity, and area) as the source hazardous
              waste quantity value. (Do not round to the nearest integer.)
                                           109
                                                                                 Section 6.5

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                                                      HIGHLIGHT 6-8
                                   FLOWCHART FOR  EVALUATING  TIER D
                                                                          START
                                                                         SOURCE #1

                                                                 Source with containment factor
                                                                   value >0. (See Section 6.1)
                                                   YES
                                                   YES
                                                   YES
                          Do not evaluate source
                            for area (Tier D).

                           Assign the source a
                              value of 0 for
                                Tier D.
                                                                Was hazardous constituent quantity
                                                                (Tier A) or hazardous wastestream
                                                                  quantity (Tier B) adequately
                                                                         determined?
                                                                 Is source an unallocated source?
                                                                Was source assigned a value for
                                                                       volume (Tier C)?
                                                                                 NO
Compile information on area of source.
           (See 01)
                                                                    Calculate area for source
                                                                      and designate as A.
                                                                          (See D2)
                                                  Use appropriate equation below (adapted from HRS Table 2-5) to
                                                  assign source a value for area.
                                                  Area (A)

                                                  Landfill                           square feet
                                                  Surface Impoundment               square feet
                                                  Surface Impoundment (buried/backfilled) square feet
                                                  Land treatment                    square feet
                                                  Pile                             square feet
                                                  Contaminated Soil
                              A/3,400
                              A/13
                              A/13
                              A/270
                              A/13
                              A/34,000
Section 6.5
                                                               110

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SECTION  6.6
HAZARDOUS WASTE
QUANTITY
CALCULATION
                                                                         we
      This section discusses, in greater detail, calculating
the hazardous waste quantity factor value and provides the scorer with some examples. Minimum factor
values are also discussed.

SELECTING SOURCE HAZARDOUS WASTE QUANTITY VALUES

      After evaluating all the appropriate tiers for the source, make a list of the scores for each tier.
Select the highest of the values assigned to the source for hazardous constituent quantity, hazardous
wastestream quantity, volume, and area. This value is the source hazardous waste quantity value.
Highlight 6-9 is a typical calculation for the source hazardous waste quantity value.

CALCULATING PATHWAY HAZARDOUS WASTE QUANTITY FACTOR VALUE

      After assigning source hazardous waste quantity values to all the sources (both allocated and
unallocated) at a site, determine the hazardous waste quantity factor value for the migration pathway.
Sum the source hazardous waste quantity values assigned to all the applicable sources (including the
unallocated sources) for the migration pathway being evaluated. Round this sum to the nearest integer,
except if the sum is greater than 0, but less than one, round it to one. Based on this value, select a
hazardous waste quantity factor value for the migration pathway using MRS Table 2-6.

APPLYING THE MINIMUM FACTOR VALUE

      If the hazardous constituent quantity (Tier A) is not adequately determined for all sources, then
the hazardous waste quantity factor value is subject to a minimum value of 10. However, if any target for
the migration pathway is also  subject to Level I or  II concentrations, this factor value is subject to a
minimum of 100.  If a removal  has taken place, see the removal fact sheet for additional considerations
regarding the minimum factor value.
      Highlight 6-10 provides a typical calculation for the pathway hazardous waste quantity factor
value.
                                       111
                                                                           Section 6.6

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                                       HIGHLIGHT 6-9
                       CALCULATION OF SOURCE HAZARDOUS
                                WASTE QUANTITY VALUE
        Site A has a surface impoundment filled to capacity with various wastes. The hazardous
        substances that are present in the surface impoundment include: ethyl acetate, acetone, lead,
        chromium, dichlorophenol, and phenol. All of these hazardous substances were detected in soil
        below the impoundment.
        Tier A:
        Tier B:
        TierC:
        Tier D:

        Final
        Values:
        Source
        HWQ Value
No concentration data are available for any waste in the impoundment.
Representative samples could not be obtained.

Internal waste tracking forms at the site indicate that 475,000 pounds of waste
from a plating operation were deposited into the impoundment between 1965
and 1970.The data are incomplete; however, because there were other
hazardous wastestreams deposited prior to 1965.

For Tier B, the mass (in pounds) of the hazardous wastestreams, based on
incomplete data, is to be divided by 5,000, according to MRS Table 2-5.

475,000 pounds/5,000                    =       95

The surface  impoundment measures 150 x 10 x 8 feet. Therefore, the volume is:

150x10x8 ft            =       12,000ft3        =       444.444yd3

According to MRS Table 2-5, the appropriate divisor for a surface impoundment
that is not buried or backfilled is 2.5. Therefore, the value for source volume is:

444 y3/2.5                               =       176

Because the volume has been determined, assign a value of 0.
Tier A:
Tier B:
TierC:
Tier D:
176
N/A
  95
 176
   0

Section 6.6
                                              112

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                              HIGHLIGHT 6-10
          CALCULATION OF PATHWAY HAZARDOUS WASTE
                        QUANTITY FACTOR VALUE

For each pathway, add source HWQ values for sources with containment values greater than 0 for
that pathway plus the HWQ from any unallocated source. This sample site has three sources and
no targets are subject to Level I or II concentrations:
Source
Surface impoundment
Contaminated soil area
Buried trench
Source HWQ
Value
4,615.38
0.28
177.78
Source Containment Factor Value
Greater than 0 for all pathways
Greater than 0 for all pathways
0 for air pathway; greater than 0 for ground
water and surface water pathways
The air pathway HWQ value is 4,616 (4,615.38 + 0.28). The ground water and surface water pathway
HWQ value is 4,793 (4,615.38 + 0.28 + 177.78). The HRS requires rounding off to the nearest integer.

Based on the HWQ value for each pathway, select the HWQ factor value from HRS Table 2-6. For all
pathways, the value is 100.
                                        113
                                                                               Section 6.6

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CHAPTER 7
GROUND WATER PATHWAY
 LIKELIHOOD OF
 RELEASE

 Observed Release or
 Potential to Release
  Containment
  Net Precipitation
  Depth to Aquifer
  Travel Time
WASTE
CHARACTERISTICS

Toxicity/Mobility
Hazardous Waste
  Quantity
TARGETS

Nearest Well
Population
Resources
Wellhead Protection
  Area

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SECTION  7.1
DETERMINING
AQUIFER  BOUNDARIES
AND  NUMBER OF
AQUIFERS
       In the MRS, a ground water pathway score is developed for each aquifer that underlies either
sources at the site or contamination that is attributable to the site. In addition, aquifers that are in direct
contact with or interconnected with aquifers that underlie sources at the site may be included in the
evaluation. The first step in scoring the ground water pathway, therefore, is to identify the geologic
materials that comprise aquifers that directly underlie sources at the site. This section provides guidance
on information sources that can be used to identify such geologic materials.

       Once the geologic materials under sources at the site are identified, guidance is provided on how
to carry out these next steps:

              Identify boundaries for each aquifer that underlies sources at the site by combining
              appropriate geologic materials;

              Determine if any discontinuities completely transect such aquifers within the 4-mile TDL
              and disregard portions of the aquifers on the far side of the discontinuity from evaluation;

              Examine possible interconnections between aquifers that are separated by  apparent
              aquifer boundaries; and

              Combine aquifers interconnected with aquifers that underlie sources at the  site into a
              single hydrologic unit, and determine how many hydrologic units need to be evaluated
              for the ground water pathway.

       Guidance in this section focuses on the major issues typically arising in aquifer evaluations. To
the maximum extent possible, this information is presented in a form that does not require extensive
expertise in the principles of geology. However, expertise in geology is often required to compile and
analyze the data used to define aquifers for MRS purposes. Further, while this guidance is intended to be
applicable  across a wide range of sites, professional judgment will be needed to apply the evaluation
criteria to site-specific circumstances.

       In general, aquifer boundaries occur between two different geologic materials, only  one of which
is used as  an aquifer (or both are used as aquifers and one has a significantly lower hydraulic
conductivity). However, there can be geologic features that occur within the same geologic  materials and
that present a barrier to ground water flow and hazardous substance transfer. Such features are referred
to as aquifer discontinuities.

       The presence of aquifer interconnections is evaluated only when one or more aquifer boundaries
(including discontinuities) are present within 2 miles of sources at the site  (or within areas underlying
ground water contamination attributable to the site). For MRS purposes, aquifers can be combined into a
single hydrologic unit if they are shown to be  interconnected.

       A precise definition of aquifers requires comprehensive scientific data that may be beyond the
scope of an SI. Further, in complex geologic settings, precise definition  of aquifers may be beyond
                                            115                                    Section 7.1

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current scientific understanding. Therefore, the guidance in this section describes a level of investigation
associated with gathering the necessary information on aquifers and their boundaries to support MRS
scoring of a site that is consistent with the level of investigation that has been employed successfully for
purposes of listing sites on the NPL.
                               RELEVANT MRS SECTIONS

         Section 3.0.1.1          Ground water target distance limit
 Section 3.0.1.2                 Aquifer boundaries
 Section 3.0.1.2.1                Aquifer interconnections
 Section 3.0.1.2.2                Aquifer discontinuities
DEFINITIONS
       Aquifer: One or more strata of rock or sediment that is saturated and sufficiently permeable to
       yield economically significant quantities of water to wells or springs. An aquifer includes any
       geologic material that is currently used or could be used as a source of water (for drinking or
       other purposes) within the TDL.

       Aquifer Boundary: A physical barrier to ground water flow identified as the contact between
       geologic materials defined as an aquifer and materials defined as non-aquifer (or as an aquifer
       but with a significantly lower hydraulic conductivity). Where aquifer interconnections are
       documented, aquifer boundaries are expanded to encompass the interconnected aquifers.

       Aquifer Discontinuities: Geologic and  hydrologic features or structures that entirely transect an
       aquifer (or multiple aquifers, if interconnected) and that are expected to disrupt and/or prevent
       the flow of ground water and hazardous substances across the feature or structure. Aquifer
       discontinuities are a type  of aquifer boundary.

       Aquifer Interconnections: Subsurface  conditions that allow two or more aquifers separated by
       aquifer boundaries to be combined into  a single aquifer (i.e., a single hydrologic unit).
       Subsurface conditions must demonstrate that the aquifer boundaries separating the aquifers do
       not or would not impede the flow of ground water and hazardous substances between the
       aquifers. Aquifer interconnections  are evaluated within two miles of sources at the site and in
       areas underlying contamination attributable to the site.

       Confining Layer: A layer of low hydraulic conductivity (relative to adjacent geologic materials)
       that is not expected to be used as  an aquifer.

       Hydraulic Conductivity:  The overall ability of water to flow through a geologic material,
       accounting for all openings  in the material (e.g., between grains, through fractures, along lava
       tubes). For MRS purposes, the terms hydraulic conductivity and  permeability are used
       interchangeably.

       Layer of Lower Relative Hydraulic  Conductivity: A geologic material with lower hydraulic
       conductivity than adjacent geologic materials.  If used to establish aquifer boundaries, the
       difference in hydraulic conductivity should be at least two orders of magnitude.

       Single Hydrologic Unit:  The combination of geologic materials and aquifers that are
       determined to be within the  same aquifer boundaries, including all interconnected aquifers.
Section 7.1                                       116

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       Target Distance Limit (TDL) for the Ground Water Migration Pathway: The distance over
       which targets are evaluated. The TDL is generally a 4-mile radius from sources at the site,
       except:

               Include any drinking water well with an observed release attributed to the site, regardless
               of its distance from the source.

               Exclude wells completed in portions of an aquifer that are beyond an aquifer
               discontinuity.

       Top of the Aquifer: In unconfined (water table) aquifers, the uppermost elevation of water,
       accounting for temporal variations, as long as the water table occurs in the materials used as an
       aquifer. In confined aquifers, the top of the geologic material producing water.

       Well Log: A record of geologic materials with depth based on data obtained beneath a point on
       the land surface and representative of types, depths, and thicknesses of materials beneath that
       point. The data may represent visual  observations, physical/chemical characterizations, and/or
       geophysical properties. The  record also contains  information on wells (drinking and monitoring),
       where appropriate.

IDENTIFYING AND EVALUATING AQUIFERS

       To understand and describe aquifers and their boundaries for MRS purposes, the scorer must
compile sufficient information to identify the types and boundaries of geologic materials that underlie
sources at the site. The ultimate goal of the evaluation is to determine which drinking water wells within
the 4-mile TDL are located in geologic materials that  either underlie sources at the site (or contamination
attributable to the site) or are interconnected with such geologic materials within 2 miles of sources at the
site. The information should, at a  minimum, identify:

               Types of bedrock and their boundaries (both lateral and vertical);

               Types of surficial deposits and their boundaries (both thicknesses and lateral extents);
               and

               Locations and screened depths of wells being evaluated as targets.

       Scorers are faced with determining the appropriate level of investigation to define aquifers and
their boundaries. Given the level  of effort associated with  PAs, Sis, and preparation of MRS packages,
the definition of aquifers and their boundaries relies principally on existing information. This existing
information may be augmented with site-specific information collected during the SI, such as through the
installation of soil borings, construction of monitoring wells, sampling of monitoring or other wells, visual
observations of springs or any other measurements or observations providing insight into geologic
materials and aquifers.

       The approach used in the MRS evaluation and scoring of aquifers is first to establish an aquifer,
and then to expand its boundaries, combining it with other aquifers for MRS purposes as information
arises to justify the expansion or combination. The types of data and levels of investigation used to
evaluate  aquifer boundaries can be divided into three categories. The first level of investigation is
expected to be adequate to define aquifer boundaries at the majority of sites, The second level of
investigation is expected to be needed at a small percentage of sites to refine aquifer boundary
determinations.  Both the first and second levels of investigation rely on existing data or that collected
during the PA/SI. The third level of investigation defines activities beyond the scope of a typical PA/SI
that, on a limited basis, may be performed to define aquifers for MRS purposes.  Data collected to support
these levels of investigation are described in  more detail \r\Highlights 7-1, 7-2, and 7-3.
                                              117                                      Section 7.1

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                                          HIGHLIGHT 7-1
             AQUIFER DATA USED FOR FIRST LEVEL OF INVESTIGATION

 Although this type of data is expected to be adequate for a majority of sites, some sites may require collection of
 additional data. At some sites, however, aquifer boundaries may be described when only portions of the data in
 this category have been collected.

         Use state, regional, or county bedrock geology maps as a starting point for identifying geologic
         formations and materials within the 4-mile TDL.

         Use state, regional, or county maps on surficial deposits of unconsolidated materials, overburden
         thickness, and depth to bedrock (if available) to augment the bedrock geology map.

         Collect scientific journals on geology or ground water resources in the area published by Federal
         agencies (at a minimum,  check bibliographies  of the USGS and the U.S. Department of Agriculture).
         Look for geologic descriptions, geologic maps, cross-sections of geologic formations, and ground water
         use Information.

         Collect publications, circulars,  bulletins  or any other reports from  state agencies responsible for
         geologic or ground water resource information. The responsibility for geologic and ground water
         resource  information may reside with separate state agencies; Investigate  Departments of
         Environments, Departments of Natural Resources, Pollution Control Agencies, Ground Water Resource
         and/or Protection Offices, Departments  of Health, and any others  with  possibly pertinent information,
         Look for information described above for Federal sources along with well logs for drinking water wells.

         Check with county and other local environmental and health officials for information on geology and
         ground water use, including well logs for drinking water wells.

         Contact site personnel, area residents, local officials, and water supply companies to determine sources
         of drinking water.

         Augment data identified above with site-specific information collected during the  PA/SI, including depth
         to ground water, depth of drinking water wells, geologic materials at the site,  and ground water use.

 The data collected above should serve  in most cases to delineate geologic materials and  to identify which
 geologic materials are being used as drinking water sources. If these data  do not adequately identify aquifers,
 their boundaries, and ground water targets, additional data collection may  be necessary.
Section 7.1                                         118

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                                       HIGHLIGHT 7-2
         AQUIFER DATA USED FOR SECOND LEVEL OF INVESTIGATION

A review of the data identified as primary usually is adequate to evaluate aquifers for MRS purposes. However,
secondary data may be needed to characterize more fully the boundaries of aquifers relative to adjacent
materials. Such data include:

        Existing data on aquifer testing such as pumping and slug test data

        Contaminant migration studies

        Cross-sections generated from well log data by the scorer

        Ground water data and references from other NPL sites within the 4-mile TDL (this is considered
        secondary information since it may only serve to identify sources of information previously undetected)

Secondary aquifer data are not necessary to define aquifers at a site. Rather, they serve to expand aquifer
boundaries, as appropriate, so that the potential threat to ground water targets within the TDL is more accurately
reflected. Nonetheless,  secondary aquifer data should be collected and compiled if encountered during collection
of primary aquifer data.
                                       HIGHLIGHT 7-3
           AQUIFER DATA USED FOR THIRD LEVEL OF INVESTIGATION

Tertiary aquifer data include those data that are determined to be absolutely critical to the scoring of a site, but
are not available after the collection of primary and secondary aquifer data. Under these circumstances, the
allocation of additional resources  may be warranted. The decision to allocate additional resources should
Incorporate a consideration of the costs of acquiring additional information. EPA is prepared to provide technical
support on a case-by-case basis to assist in these decisions. Tertiary aquifer data include the following:

        Installation of additional monitoring wells beyond those included in an SI

        Performance of aquifer (pumping and slug) tests

        Mapping of geology in the field

It is anticipated that tertiary data will only be warranted at a limited number of sites.
                                              119                                       Section 7.1

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       This section describes one approach for identifying and evaluating aquifers. In general, this
approach is based on the fact that much of the geologic literature and information to be collected is
presented and organized by geologic formations. Indeed, aquifers may be identified in the literature as
corresponding to specific geologic formations. However, for MRS purposes, an aquifer may consist of
multiple formations or may be limited to discrete  portions of a single formation which differ from aquifer
boundaries as identified in the literature.Thus, the procedures outlined below are intended to provide
one possible approach  for the compilation of information on geologic formations  and to provide guidance
on evaluating the  data in order to establish aquifer boundaries for purposes of MRS scoring.

(1)     Collect readily available information on geology. Focus on first level data, as detailed in
       Highlight 7-1, but collect any second level data encountered. Proceed until all first level data
       are collected or until  a person knowledgeable about scoring of aquifers for MRS  purposes has
       determined that sufficient information is available to identify aquifers and their boundaries.

(2)     Collect information  on ground water use. Continue to collect data until the source of drinking
       water can be characterized for all ground water targets being evaluated (this effort overlaps with
       identification of drinking water sources for the surface water pathway). Note other, non-drinking
       water uses for ground water within the TDL. Although specific guidance is provided in later
       sections on the detailed evaluation of targets (see Sections 7.4 through 7.9), it is important to
       remember that  if no drinking water wells  are located in geologic materials, it generally is not
       necessary to characterize these materials.

(3)     Compile and analyze data from Steps  (1) and (2). Resolve any real or apparent discrepancies
       in the geologic  or ground water use information. Where  information is deemed credible, give
       preference to local or site-specific information over regional information.  Similarly, give
       preference to regional information overstate-wide information. The result of Step (3) should be
       an understanding of the geologic setting and  ground water use sufficient to do the following:

               Create  a map of the geologic formations within the 4-mile TDL;

               Construct typical cross-sections  of the geologic  formations in several different directions
               through the 4-mile TDL (the  cross-sections do not necessarily have to be prepared, but
               the information available should  be sufficient to  be able to do so); and

               Determine the geologic material  being used if provided with well  location, well log, and
               screened interval.

(4)     Identify the geologic materials being used as aquifers. Note that geologic formations may be
       comprised of multiple layered strata  and  that  materials used as an aquifer may be limited to
       discrete layers  of a specific formation. Using  maps of geologic formations within  the 4-mile TDL
       and/or cross-sections of the geology, mark all geologic materials being used as an aquifer. The
       boundaries of the geologic materials being used as an aquifer represent the initial identification
       of aquifers and  their boundaries for MRS purposes.

(5)     Evaluate  aquifer boundaries  by examining physical relationships between geologic
       materials used as aquifers, as follows:

               If geologic materials are used as aquifers, are in contact with one another within the
               TDL, and have hydraulic conductivities within two  orders of magnitude, then combine the
               materials into a  single aquifer for MRS purposes (see High lights 7-4 and 7-5). Specific
               exceptions and/or clarifications to this rule are provided \r\Highlights 7-6 and 7-7.
Section 7.1                                       120

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                             HIGHLIGHT 7-4
              COMBINING HORIZONTAL FORMATIONS
               (formations are shown in cross-section)
               4 miles
4 miles
                                            Formation 1
                                  Scenario A


All three geologic formations are used as aquifers within the TDL.

Formations 1 and 2 are in direct contact, and Formations 2 and 3 are in direct contact.

The hydraulic conductivities for all three formations are within two orders of magnitude of adjacent
formations.

Therefore, there is no aquifer boundary between Formations 1 and 2, or between Formations 2 and
3; Formations 1, 2, and 3 are combined into a single hydrologic unit (i.e., aquifer) for HRS scoring
purposes.
                4 miles
                                  Scenario B


Formations 1 and 3 are used as aquifers.

Although no specific information is available for Formation 2, there is no evidence of use.

Therefore,  until  more information  becomes available,  Formation 2  is an aquifer boundary for
Formations 1 and 3; thus, Formations 1  and 3 are evaluated as separate aquifers. The documentation
of an aquifer interconnection between Formations 1  and 3 would result in combining  the formations
into a single aquifer.
                                      121
                                                                                   Section 7.1

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                                       HIGHLIGHT 7-5
                          COMBINING VERTICAL FORMATIONS
                         (formations are shown in cross-section)
                        4 miles
                                            [Source I
                           Formation
                               1
                           K=10 E-5
                                   Formation \ Formation ^ Formation //
                                                  3
                                              K=10 E-2
           All four formations are used as aquifers within the TDL

           Hydraulic conductivity (K)  of each the formation  (provided in  units of centimeters per second;
           therefore, 10 E-4 = 0.0001 cm/sec) is within two orders of magnitude of the hydraulic conductivities
           of adjacent formations.

           No aquifer boundaries exist between Formation 3 (which underlies the site) and Formations 1,2, and
           4.

           Therefore, Formations 1, 2, 3, and 4 are combined into a single hydrologic unit (i.e., aquifer).

Section 7.1
                                              122

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                           HIGHLIGHT 7-6
COMBINING VERTICAL FORMATIONS WITH DIFFERENCES IN
                    HYDRAULIC CONDUCTIVITY
              (formations are shown in cross-section)
            4 miles
All four formations are used as aquifers within the TDL, Formation 3 underlies sources at the site.

The hydraulic conductivities of Formations 1,3, and 4 shown in the diagram are provided in cm/sec;
no information exists on the hydraulic conductivity of Formation 2,

Formation 3 and Formation 4 have hydraulic conductivities within two orders of magnitude; thus, no
aquifer boundary exists between Formations 3 and 4.

Formation 2 is considered an aquifer boundary because no hydraulic conductivity information is
available and no aquifer interconnection has been documented between Formation 2 and Formations
1 or 3.

Therefore, Formations 3 and 4 are combined into a single hydrologic unit (i.e., aquifer). Formations
1 and 2 are not evaluated as aquifers because neither underlies sources at the site or areas of
contamination attributable to the site.
                                   123
                                                                             Section 7.1

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                                        HIGHLIGHT 7-7
                     DELINEATING AQUIFER WHEN A BOUNDARY IS
                     CONTINUOUS THROUGHOUT 2-MILE DISTANCE
                          (formations are shown in cross-section)
                           4 miles
4 miles
             Four formations underlie the site within the TDL.

             Formations 1 and 3 are very similar in nature and are both used as aquifers within the TDL

             Formations 2 and 4 are not used as aquifers and are low hydraulic conductivity layers relative to
             Formations 1 and 3.  Therefore, they are aquifer boundaries.

             Formations 1 and 3 are in direct contact within the TDL but are completely separated by a low
             hydraulic conductivity layer throughout the 2-mile radius.

             Therefore, the portion of Formations 1 and 3 that are in direct contact are  combined into a single
             hydrologic unit (i.e., aquifer) indicated by dashed lines on the figure. Those portions separated by
             the aquifer boundary are excluded unless an aquifer Interconnection can be documented between
             Formations 1 and 3 within the 2-mile radius.

             If Formation 2 did not underlie Formation 1 throughout the entire 2-mile radius, Formation 1 would
             be combined with all of Formation 3 for MRS scoring purposes.
Section 7.1
                                                124

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               If materials used as aquifers are not in contact within the TDL, evaluate the potential
               for aquifer interconnections, as explained in the subsection below, Identifying Aquifer
               Interconnections. Where interconnections exist, combine the boundaries of the
               interconnected materials into a single aquifer for MRS purposes.

       Continue with Step (5) until aquifer boundaries are  documented sufficiently to support an
       accurate ground water pathway score, or until all primary and secondary sources of data have
       been exhausted. Evaluate the need for tertiary data on a case-by-case basis.

(6)     Identify aquifer discontinuities. See subsection below,  Identifying Aquifer Discontinuities.
       Where discontinuities are identified, restrict aquifer boundaries as  specified in  MRS section
       3.0.1.2.2. Use all information to evaluate aquifer boundaries to determine if discontinuities
       exist. If this information does not indicate the  presence of potential discontinuities, assume
       that no  discontinuities are present. However,  the identification of potential discontinuities to be
       evaluated further is subject to professional judgment. As necessary, collect further information
       until all potential discontinuities have been evaluated and  incorporated into aquifer
       boundaries, as appropriate. If aquifer boundaries (including discontinuities) are identified
       within two miles of sources at the site or within areas underlying ground water contamination
       attributable to the site (if contamination extends beyond  two miles), proceed to Step (7).
       Otherwise, use the information gathered to identify those aquifers  to be scored.

(7)     Identify aquifer Interconnections. See subsection  below, Identifying Aquifer Interconnections.
       Where  interconnections are identified, combine the aquifers having interconnections in scoring
       the ground water pathway. If data are not adequate to establish aquifer interconnections, only
       evaluate aquifers that underlie sources at the site.

IDENTIFYING AQUIFER  DISCONTINUITIES

       Aquifer discontinuities are physical barriers to flow and do not include boundaries based on
ground water flow directions (e.g., ground water divides and ground water  discharge boundaries). To  be
considered an aquifer discontinuity, the feature must  entirely transect the  aquifer(s) being evaluated.
Examples of aquifer discontinuities include major faults, intrusive formations (e.g., dikes, sills), erosional
channels (e.g.,  rivers, streams), and large bodies of water (e.g.,  lakes, bays, estuaries, and oceans).

       Sources of evidence for aquifer discontinuities include geologic maps, scientific literature, and
topographic maps. In general, any geologic or hydrologic features that are mapped or described and
appear to be of sufficient size to transect an aquifer should be considered  a potential discontinuity. If
sufficient information has been collected to identify aquifer boundaries and ground water targets and  no
discontinuities are identified, it can be assumed for MRS scoring  purposes  that no discontinuities exist.
When a potential discontinuity is identified, evaluate  the data to determine:

               If the discontinuity entirely transects the aquifer(s)  being evaluated within the TDL; for
               interconnected aquifers, a discontinuity must transect the entire interconnected unit (see
               Highlight 7-8); and

               If the discontinuity disrupts the flow of ground water and hazardous substances between
               the materials on opposite sides of the discontinuity (i.e., a  discontinuity does not exist if
               hazardous substances have been shown to migrate across the potential discontinuity
               within the TDL).

       To evaluate whether the feature entirely transects, an aquifer, rely on geologic maps and
cross-sections.  For erosional  channels such as streams and rivers, knowledge of the depth of the
channels with respect to the depth (thickness) of the aquifer usually is sufficient.


                                              125                                      Section 7.1

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                                       HIGHLIGHT 7-8
                      DELINEATING AQUIFER WHEN BOUNDARY
                            PARTIALLY TRANSECTS AQUIFER
                  Scenario A
Scenario B
    Scenario A
           Formations 1 and 2 are in direct contact, both are used as aquifers, and they have similar hydraulic
           conductivities; thus, no aquifer boundaries are established between Formations 1 and 2, and they are
           considered a single hydrologic unit.

           A diabase dike (an intrusive, igneous rock) cuts across the formations; the diabase extends to depths
           below the bottom of Formations 1 and 2.

           The diabase has a significantly lower hydraulic conductivity than Formations 1 and 2.

           Since Formations 1 and 2 are combined into one aquifer for scoring purposes, the diabase is not
           considered a discontinuity because it does not entirely transect the aquifer being scored.
    Scenario B
           Only Formation 2 Is used as an aquifer. Formation 1 has a significantly lower hydraulic conductivity
           than Formation 2.

           A diabase dike of significantly lower hydraulic conductivity cuts across Formation 2.

           The diabase forms an aquifer discontinuity for Formation 2. Because only the dashed portion of the
           formation underlies sources at the site, only that portion is evaluated.
       To show that the feature disrupts the exchange of ground water and hazardous substances, use
the guidance below for documenting aquifer interconnections. If an aquifer interconnection can be
documented, the feature being evaluated does not represent an aquifer discontinuity for MRS
scoring purposes.
Section 7.1
                                               126

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IDENTIFYING AQUIFER INTERCONNECTIONS

       Evaluate the presence of aquifer interconnections only if aquifer boundaries and discontinuities
occur within 2 miles of sources at the site (or within areas underlying ground water contamination
attributable to the site). To identify an aquifer interconnection, evaluate the ability of nonaquifer materials
occurring between aquifers to transfer ground water and hazardous substances. Where the nature of the
intervening materials and/or features penetrating the  intervening materials allows for such transfer with
minimal or no disruption in flow path or velocity, consider the aquifers interconnected.

       Precise definitions are not available for determining when intervening materials would have
"minimal or no disruption" on hazardous substance and ground water flow. Howev*f
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                                        HIGHLIGHT 7-9
                 HORIZONTAL AQUIFERS SEPARATED BY FORMATION
                         OF SIMILAR HYDRAULIC CONDUCTIVITY
                          (formations are shown in cross-section)
                     4 miles
4 miles
                          Aquifer 1 - sand and gravel
                                       ///, Aquifer 2 - bedrock
                                       Y//////////////,
             An upper sand and gravel aquifer is separated from an underlying bedrock aquifer by a layer of
             saprolite (i.e., weathered bedrock).

             The underlying bedrock Is a moderately permeable igneous rock.

             The saprolite is not used  as an aquifer.

             Geologic information Indicates that the saprolite is the equivalent of afine-grained, poorly sorted sand.

             Based on HRS Table 3-6, the hydraulic conductivities of the formations are as follows:

             —      sand and gravel  -10"2 cm/sec
             —      bedrock (moderately permeable igneous rock) -10"4 cm/sec
             —      saprolite (equivalent of a fine-grained, poorly sorted sand) -10"4 cm/sec

             Although the intervening saprolite is not used as an aquifer, it does not have a hydraulic conductivity
             more than two orders of magnitude lower than the sand and gravel aquifer.

             Because the sand and gravel aquifer and the bedrock aquifer are not separated by a layer of
             significantly lower hydraulic conductivity, the aquifers are considered interconnected and combined
             into a single hydrologic unit for HRS scoring purposes.
Section 7.1
                                                128

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                                    HIGHLIGHT 7-10
        USING WELL LOGS TO ASSESS AQUIFER INTERCONNECTION
                      (formations are shown in cross-section)

        An upper sand and gravel aquifer is separated from an underlying bedrock aquifer by a layer of
        interbedded sands and clays.

        Different log results are presented for each of three scenarios below. In all scenarios, well logs at the
        site show that drinking water wells are screened in sands and gravels above 30 feet In depth or in
        bedrock below 70 feet in depth; no wells are screened at depths correlating with the interbedded zone
        of sands and clays.

        The upper  (sand and gravel) aquifer has the same hydraulic conductivity as the lower (bedrock)
        aquifer. Also,  the sand zones between the aquifers have the same hydraulic conductivity as the
        aquifers. In contrast,  the clay zones are of significantly lower hydraulic conductivity relative to the
        aquifers.

        Aquifer interconnections can be identified as follows:
                    2 miles
2 miles
                                         Scenario A

A well log within the 2-mile radius shows a location where no clay layer (or other layers of significantly lower
hydraulic conductivity) separate the surficial and bedrock aquifers.  The upper (sand and gravel) and lower
(bedrock) aquifers are combined for HRS scoring purposes  because there is not a continuous layer of
significantly lower hydraulic conductivity that separates the two aquifers throughout the 2-mile radius.  This
evidence for interconnection is considered conclusive.

                                  (continued on next page)
                                             129
                                                                                           Section 7.1

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                                HIGHLIGHT 7-10 (continued)
            USING WELL LOGS TO ASSESS AQUIFER INTERCONNECTION
                          (formations are shown in cross-section)
                           2 miles
Well logs
   >"     2 miles
                                            Scenario B

     Multiple well logs show that clays are of limited extent and comprise less than 25 percent of the materials
     between 30 and 70 feet.  The upper (sand and gravel) and lower (bedrock) aquifers are combined for HRS
     scoring purposes because it is assumed that there is no continuous layer of significantly lower hydraulic
     conductivity that separates the two aquifers throughout  the 2-mile radius.  The conclusion is based on a
     preponderance of evidence and professional judgment. The use of 25 percent in this highlight is not intended
     to establish a benchmark; rather, it provides a hypothetical example of the use of professional judgment in light
     of site-specific supporting information.
                          2 miles
                                                          Well logs
         2 miles

Sand &
Gravel
Aquifer
                                            Scenario C

     Multiple well logs show a high percentage of clay within the interbedded zone.  The aquifers would not be
     considered interconnected for HRS purposes.
Section 7.1
                                                130

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                              HIGHLIGHT 7-11
           USING CONTAMINANT MIGRATION TO ASSESS
                     AQUIFER INTERCONNECTION
                (formations are shown in cross-section)
                                                                         2 miles
Contaminant
   Plume
  A series of fractured bedrock formations dip in the same direction as follows:  (a) a sandstone
  formation underlies the site and is used as an aquifer, (b) adjacent to the sandstone in the downdip
  direction is a shale formation that is not used as an aquifer and is a low hydraulic conductivity layer
  relative to adjacent formations, and (c) adjacent to the shale in the downdip direction is a limestone
  formation that is used as an aquifer.

  The sandstone (Aquifer 1) and limestone (Aquifer 2) formations are separated by a shale formation
  that is not used as an aquifer and has a significantly lower hydraulic conductivity; thus, the aquifers
  are initially evaluated separately.

  Without documenting aquifer interconnections,  Aquifer 1 can be scored while Aquifer 2  does not
  underlie the site and would not be evaluated.

  Ground water contamination has been shown to have moved from Aquifer 1 to Aquifer 2 across the
  shale and within the 2-mile radius.  This contamination does not have to be attributable to the site.
  Also, contaminant migration from Aquifer  2  to Aquifer 1  may not be  used to document an
  interconnection.

  Therefore, Aquifers 1 and 2 are considered interconnected and are combined into a single hydrologic
  unit for scoring purposes because contamination has been shown to have migrated between two
  aquifers across an aquifer boundary. Although  the mechanism of contaminant transport  does not
  have to be identified, sufficient evidence should be presented to eliminate other likely mechanisms
  for the  introduction of the contaminant into the limestone aquifer.
                                      131
                                                                                   Section 7.1

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                                          HIGHLIGHT 7-12
                           USING  PUMPING TEST DATA  TO ASSESS
                                  AQUIFER INTERCONNECTION
                             (formations are shown in cross-section)
                Aquifer 1
                Limestone
                Dolomite
                Aquifer 2
                Limestone
                                                                             2 miles
                                                                                  -Surficial
                                                                                   Deposits
                                                                                  Water Level
                    Screening Interval

              A  formation is flat-lying and consists of interbedded layers of limestone and dolomite; from the
              surface, there is a 50-foot thickness of limestone, a 40-foot thickness of dolomite, and a 90-foot
              thickness of limestone.

              The limestone layers are used as aquifers while there is no indication that the dolomite is used as an
              aquifer.

              No information on hydraulic conductivity is available for the limestone or dolomite layers.

              Initially, the dolomite layer is considered an aquifer boundary,  and  the limestone aquifers are
              evaluated separately.

              A pumping test is conducted of the lower limestone aquifer, and water levels in the upper limestone
              aquifer are monitored before,  during, and  after the test.

              Static water level was determined in the upper limestone; fluctuations were within 8 inches.

              During pumping, water levels in the upper aquifer dropped, on average, 2 feet and 9 inches; following
              a cessation of pumping, water levels in the upper aquifer returned to static levels.

              Therefore, the upper and lower limestone aquifer are considered interconnected at the location of the
              well being pumped in the lower aquifer; the aquifer test (pumping test) data show that pumping of the
              lower aquifer has  a measurable impact on water  levels in the upper aquifer.
Section 7.1
                                                   132

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                           HIGHLIGHT 7-13
    USING  NUMEROUS MAN-MADE CONDUITS TO ASSESS
                   AQUIFER INTERCONNECTION
              (formations are shown in cross-section)
                                   Abandoned
                                    Boreholes
                                                            2 miles
A sand and gravel formation is separated from a fractured pegmatite (i.e., type of igneous rock)
formation by a layer of gneiss (i.e., type of metamorphic rock).

Well logs show that the sand and gravel formation and the pegmatite are used as aquifers; there is
no indication that the gneiss is used as an aquifer.

No information on hydraulic conductivity of the materials is available; initially, the sand and gravel
aquifer and the pegmatite aquifer are evaluated separately.

Historical records and well log information indicate that uncased boreholes were placed through the
gneiss in order to mine the pegmatite.

Numerous (more than 100) mining shafts could be located, based on boring logs, within 1 mile of the
site; none of the borings had been sealed.

Based on site-specific considerations, the extent, number, and type of boreholes through the gneiss
were sufficient to conclude that the gneiss did not have the ability to disrupt the flow of hazardous
substances between the sand and gravel aquifer and the pegmatite aquifer.

Therefore the aquifers are combined for scoring purposes. The numbers  and sizes of man-made
conduits considered sufficient to document an interconnection cannot be precisely defined; this
determination is made using professional judgment on a  site-specific basis.
                                     133
                                                                                 Section 7.1

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TIPS AND REMINDERS

       As a first step, identifying and locating wells that can potentially be evaluated as ground water
       targets may help to focus remaining data requirements for establishing aquifer boundaries.
       Establishing aquifer boundaries will then determine which targets are evaluated.

       Aquifers can be established in both horizontal and vertical directions.

       For unconfined (water table) aquifers, the uppermost elevation of ground water may not be
       known near the site; this elevation can be estimated as follows:

               In areas where streams are known to be "gaining" (that is, ground water elevations are
               greater than surface water elevations resulting in ground water discharge to the surface
               water), the elevation of the  water surface in a nearby stream can be used to determine
               the minimum elevation of ground water beneath the site. Note that elevations of flood
               stages in the stream would  not be appropriate for this determination because the stream
               is not likely to be a "gaining" stream during the flood.

               Using  well logs, evaluate water elevation data and data on ground water flow gradients
               on a regional basis to approximate the top of the aquifer beneath the site. The use of this
               approach must be based on site-specific considerations regarding the relative accuracy
               of the  data and the degree  to which the site data fits within appropriate MRS ranges.

       For confined aquifers, evaluate the top of the aquifer based on regional well logs, information on
       degree and direction of formation dip, and geologic maps.

       A body of salt water can form an aquifer boundary with the boundary defined by the location of
       the fresh water/saltwater interface. Variations in the location of the interface would potentially
       represent variations in an aquifer boundary (this is not expected to affect the MRS evaluation of
       most sites because fresh water wells generally are not located within the zone of variation of the
       fresh water/salt water interface).

       The presence  of fractures in a geologic material does not in itself establish the material as an
       aquifer or disqualify the material as an aquifer boundary; rather, the ability of the fractures to
       transmit water and the overall hydraulic conductivity of the material are the key data to consider
       (e.g., materials can be fractured and still  have relatively low hydraulic conductivities).

       Information on use of a geologic material as an aquifer outside the TDL does not qualify the
       same material as an aquifer within the TDL; there must be specific information on use within the
       TDL. However, use of the materials as an aquifer outside the TDL could be used to evaluate
       whether the material  is an aquifer boundary inside the TDL. Specifically, professional judgment
       should be used to evaluate whether properties of the material where it is being used as an
       aquifer are likely to be representative of the materials within the TDL.

       Evaluate aquifer discontinuities within the 4-mile TDL.

       An aquifer discontinuity must be a physical barrier that entirely transects all geologic materials
       combined into a single hydrologic unit  for scoring purposes, or else the discontinuity is not
       evaluated.

       If hazardous substances have migrated across a potential discontinuity in the direction of flow
       from the site, do not consider this a discontinuity.
Section 7.1                                       134

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Bodies of salt water, if they entirely transect an aquifer, would be considered a discontinuity (see
Highlight 7-14).

Ground water flow gradients and related features, such as ground water divides (e.g., ridges,
topographic highs), are not sufficient by themselves to establish a discontinuity.

Aquifer interconnections cannot be assumed, but must be supported by evidence.

Evaluate interconnections within 2 miles of sources at the site or within areas underlying ground
water contamination attributable to the site (if contamination extends beyond two miles).

Where aquifer interconnections are documented, combine all interconnected aquifers and
intervening materials into a single hydrologic unit for MRS scoring purposes.

Computer models have not been used to demonstrate interconnections. Documenting that the
assumptions used to construct and run models accurately represent hydrogeologic conditions
throughout the 2-mile distance for aquifer interconnections and the 4-mile TDL has not been
possible.
                                      135                                      Section 7.1

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                                         HIGHLIGHT 7-14
                 BODIES OF SALT WATER AS AQUIFER DISCONTINUITIES
                            (formations are shown in cross-section)
                       0 miles
2 miles
        Island
        Mainland
                           Limestone
              A limestone formation is continuous between the mainland and a nearby island; a salt-water bay
              separates the island from the mainland.

              The limestone is used as an aquifer on both the mainland and the nearby island.

              Salt water occupies the limestone formation for its entire thickness beneath the bay.

              The bay is considered an aquifer discontinuity and the freshwater zones are two separate aquifers for
              HRS purposes.  The aquifer that underlies the sources at the site (i.e., under the island) would be
              evaluated.  The aquifer under the mainland would not ba evaluated as it does not underlie sources
              at the site,  and it is not in direct contact or interconnected with an aquifer that does.

Section 7.1
                                                 136

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SECTION  7.2
TREATMENT
OF  KARST
                                                           LR
WC
       This section provides guidance on the identification of karst terrain and karst aquifers and on the
treatment of karst in the MRS evaluation of the ground water pathway. Guidance provided in Section 7.1
on identification of aquifers also applies in karst terrain and should be consulted in conjunction with this
section.

       Karst refers to a characteristic of a geologic material or formation resulting from the dissolution
of the formation by natural waters overtime. Because of the dissolution cavities and the channels that
comprise them, karst aquifers are considered extremely vulnerable to contamination. The movement of
hazardous substances released into karst aquifers is highly unpredictable, and transport over relatively
long distances can occur very rapidly. For these reasons, a karst aquifer that underlies any portion of the
sources at the site is given special consideration in the evaluation of several MRS factors within potential
to release, waste characteristics, and targets. These factors are:

              Potential to Release

                     Depth to aquifer
                     Travel time

              Waste Characteristics

                     Mobility

              Targets

                     Nearest well
                     Population/potential contamination

       At sites evaluated for potential to release (i.e., no observed release is documented), several
specific considerations for scoring karst aquifers apply. For sites with a documented observed release
(i.e., hazardous substances attributable to the site have reached the aquifer being  evaluated) and targets
subject to actual contamination, there are few, if any, specific scoring considerations for karst aquifers.

       For purposes of identifying aquifers and establishing aquifer boundaries, karst is evaluated in  the
same  manner as any other geologic formation. For each of the factors that is treated differently for karst
aquifers, a highlight presented  in this section compares the general scoring steps for a karst aquifer with
those  for aquifers without karst characteristics.
                                            1 37                                     Section 7.2

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                                RELEVANT MRS SECTIONS
       Section 1.1                 Definitions (karst)
       Section 3.0.1.3             Karstaquifer
       Section 3.1.2.3             Depth to aquifer
       Section 3.1.2.4             Travel time
       Section 3.2.1.2             Mobility
       Section 3.3.1               Nearestwell
       Section 3.3.2.2             Level I concentrations
       Section 3.3.2.3             Level II concentrations
       Section 3.3.2.4             Potential contamination
DEFINITIONS

       Karst:  A kind of terrain with characteristics of relief and drainage arising from a high degree of
       rock solubility. The majority of karst conditions occur in limestone areas, but karst may also occur
       in areas of dolomite, gypsum, or salt deposits. Features associated with karst terrain may include
       irregular topography, abrupt ridges, sinkholes, caverns, abundant springs, disappearing streams,
       and the lack of a well-developed surface drainage system of tributaries and streams. Karst
       aquifers generally are associated with karst terrain on the surface. Karst aquifers at depth may
       not be associated with karst terrain.

IDENTIFYING KARST

       To identify karst, determine the structures and features that characterize karst. This information is
often contained within the scientific literature and other primary data sources for determining aquifer
boundaries, as described in Section 7.1.

(1)     Use geologic maps and other readily available Information to determine If karat features
       are expected within 4 miles of the site. A map of the entire United States that indicates areas
       containing karst features is published by USGS; using this map, Engineering Aspects of Karst
       (document number 38077-AW-NA-07M-00), it is possible to determine if karst features are
       predicted in the site vicinity. Because of the large scale of this map, scorers should also review
       site-specific  information, including more detailed geologic maps. Where information is uncovered
       to identify a karst formation within the TDL, continue with the following steps.

(2)     Compile the available site-specific evidence that Indicates the presence of karat Note on a
       map locations with evidence of a karst feature (e.g., spring, disappearing stream, sinkhole, or
       cave); such information can be obtained from topographic maps,  aerial photographs, maps of
       caves,  and visual  observations. Also, well logs that note a drop of several feet in the bit during
       drilling  may be indicative of karst features.

       It is generally impractical at the level of an SI to perform adequate field investigations to identify
       and evaluate the extent of a karst material. Thus, existing information will be the basis for
       identification of karst. However, where information is available prior to the SI to indicate the
       possible presence of karst, limited field checks for karst features  in the area of the site may be
       compatible with the level of effort normally associated with an SI.

(3)     Estimate the lateral extent of karat. Based on the distribution of the karst features within the
       formation, use professional judgment to delineate laterally the areas containing karst features.

(4)     Estimate the thickness of karat. While the lateral extent of karst is based  on visual
       observations and surface expressions, it can  be more difficult to determine the thickness of
Section 7.2                                      1 38

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       karst. As an initial determination, the depth and thickness of the formation(s) containing the karst
       features should be evaluated. Determining formation depth and thickness for aquifers that
       underlie sources at the site is especially important for MRS scoring purposes. Indications of depth
       and thickness may be available from well log data, scientific literature, or other information
       compiled during the evaluation of aquifer boundaries.

(5)     Define the aquifer boundaries for karst aquifers. The boundary between karst and adjacent
       materials is based  on the boundary between  karst and non-karst characteristics (sed-lighlight
       7-15).

       To identify karst aquifer boundaries, start with geologic maps and information compiled during the
       identification and definition of aquifers. Based on this information, compile a list of geologic
       materials and/or formations that are known to contain karst features. Also note whether the
       information indicates the presence of karst features under sources at the site, within the 4-mile
       radius, or regionally. In those formations with karst features, evaluate the lateral and vertical
       extent of karst within the TDL, as described above.

(6)     Identify wells that draw drinking water from a karst aquifer that underlies sources at the
       site. These drinking water wells qualify for special consideration  when scoring potential
       contamination.
                                        HIGHLIGHT 7-15
                     DEFINING BOUNDARIES FOR A KARST AQUIFER
                           (formations are shown in cross-section)
       The extent of a karst aquifer or formation for MRS purposes is based on the extent of the structures and
       features associated with karst.  Where these structures or features are not present, the rapid and highly
       unpredictable movement of ground water associated with karst would not be expected, and special scoring
       considerations in the ground water pathway would not be appropriate.  In this example, a limestone formation
       forms part of both a valley wall and valley floor. The karst characteristics are present along the valley floor but
       do not occur along the valley wall.  An aquifer underlying Source A would be scored as a karst aquifer,
       because the portion of limestone formation along the valley floor would be considered karst.  An aquifer
       underlying Source B would not be scored as a karst aquifer, however, because the features leading to rapid
       ground water flow do not underlie this source.
                                                139
                                                                                            Section 7.2

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SCORING DIFFERENCES FOR KARST AQUIFERS

       The highlights on the following pages contrast the scoring procedures for each of the factors that
is scored differently (i.e., depth to aquifer, travel time, mobility, nearest well, population/potential
contamination) for karst and  non-karst aquifers.

       Before using these highlights, review Highlight 7-16 to determine which of the factors need to be
cored for the aquifer under evaluation. This highlight divides aquifers depending on how the likelihood of
release factor is evaluated (i.e., observed release by chemical analysis, observed release by direct
observation, potential to release) and by how targets are evaluated (i.e., actual contamination only,
potential  contamination with or without actual contamination). For each scoring situation, factors that
may receive special consideration for karst aquifers are listed. Remember, these special considerations
apply only to karst aquifers underlying at least a portion of the sources at the site.

       When karst aquifers are present, there are either differences from the scoring procedures or
additions to the scoring procedures used in non-karst situations. \rHighlights 7-17 to 7-21, which
explain these differences, the following key is used:

              A bullet (followed by text) in the "non-karst" column and no bullet in the "differences due
              to karst" column: "non-karst" evaluation step is used without change in evaluating a
              karst aquifer.

              Directly parallel bullets in columns labelled "non-karst" and "differences due to karst":
              step in the "differences due to  karst" column replaces the opposing "non-karst" step.

              A bullet in the "differences due to karst" column has no parallel bullet in the "non-karst'
              column: "differences due to karst" step is in addition  to the steps in the "non-karst"
              column.

These highlights are designed to summarize key differences, not to provide detailed scoring instructions.
Section 7.2                                      140

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HF
JS FACTOR GIVEN SPECIE
Type of
Likelihood
of Release
Evaluation
In Karst
Aquifer
Observed Release by
Chemical Analysis
Observed Release by
Direct Observation
Potential to Release
HIGHLIGHT 7-16
U_ CONSIDERATION FOR KARST AQUIFERS
Type of Drinking Water Targets in Karst Aquifer
Evaluated Under Actual
Contamination Only
Mobility (for hazardous
substances that don't
meet observed release
criteria)
Mobility (for all hazardous
substances)
Combination never occurs
Some or All Evaluated Under
Potential Contamination
Population/Potential
Contamination
Mobility (for hazardous
substances that don't meet
observed release criteria)
Mobility (for all hazardous
substances)
Nearest Well
Population/Potential
Contamination
All five factors may be given
special consideration


141
                                                Section 7.2

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HIGHLIGHT 7-17
SCORING CONSIDERATIONS FOR KARST AQUIFERS:
DEPTH TO AQUIFER FACTOR
Non-karst
• Determine the depth to aquifer only at locations within 2
miles of the sources at the site, except: if observed ground
water contamination attributable to sources at the site
extends more than 2 miles beyond these sources, use any
location within the limits of this observed ground water
contamination when evaluating the depth to aquifer for
any aquifer that does not have an observed release.
• Evaluate the depth to an aquifer as the distance from the
surface to the top of the aquifer minus the distance from
the surface to the lowest known point of hazardous
substance eligible to be evaluated for that aquifer.
• Based on the calculated depth, assign a value
from MRS Table 3-5 to the depth to aquifer factor.
Differences Due to Karst
• In evaluating depth to aquifer in karst
terrain, assign a thickness of 0 feet to a
karst aquifer that underlies any portion o
the sources at the site.


Section 7.2
                                                    142

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               HIGHLIGHT 7-18
SCORING CONSIDERATIONS FOR KARST AQUIFERS:
            TRAVEL TIME FACTOR











Non-karst
• Determine the travel time only at locations within
2 miles of the sources at the site, with the same
exception as in evaluating depth to aquifer (see
Highlight 7-17}.
Evaluate travel time factor based on the geologic
materials In the interval between the lowest
known point of hazardous substances at the site
and the top of the aquifer being evaluated.
• If the depth to aquifer is 10 feet or less, assign a
factor value of 35 and skip the remaining steps
for travel time.

• Determine hydraulic conductivities for Individual
layers from MRS Table 3-6 or from in-situ or
laboratory tests. Use representative, measured
hydraulic conductivity values whenever available.
Otherwise, select the lowest hydraulic
conductivity layer(s) from within the above
interval. Consider only layers at least 3 feet thick.
However, do not consider layers or portions of
layers within the first 1 0 feet of the depth to the
aquifer.

If more than one layer has the same lowest
hydraulic conductivity, Include all such layers and
sum their thicknesses.
• Assign a value from MRS Table 3-7 to the travel
time factor, based on the thickness and hydraulic
conductivity of the lowest hydraulic conductivity
layer(s).
Differences Due to Karst





If, for the interval being evaluated, all
layers that underlie a portion of the
sources at the site are karst, assign a
factor value of 35 and skip the remaining
steps for travel time.


• Assign a thickness of 0 feet to a karst
layer that underlies any portion of the
sources at the site.














                     143
                                                 Section 7.2

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HIGHLIGHT 7-19
SCORING CONSIDERATIONS FOR KARST AQUIFERS:








































MOBILITY FACTOR
Non-karst
For any hazardous substance thatmeets the
criteria for an observed release by chemical
analysis to one or more aquifers underlying the
sources at the site regardless of the aquifer being
evaluated, assign a mobility factor value of 1 .
• For any hazardous substance thatdoes not meet
the criteria for an observed release by chemical
analysis to at least one of the aquifers, assign a
mobility factor value from MRS Table 3-8 for the
aquifer being evaluated based on its water
solubility and distribution coefficient (Kj).
See MRS section 3.2.1.2 to determine the water
solubility to be used in MRS Table 3-8 for the
hazardous substance.
• See MRS section 3.2.1.2 to determine the
distribution coefficient to be used in MRS Table
3-8 for the hazardous substance. Use either the
distribution coefficient categories "< 10", " > 10 to
1 ,000", or ">1 ,000", as appropriate, if part or all of
the interval from a source to the aquifer is not
karst.


If a hazardous substance cannot be assigned a
mobility factor value because data on its water
solubility or distribution coefficient are not
available, use other hazardous substances for
which information is available in evaluating the
pathway.





• If none of the hazardous substances eligible to be
evaluated can be assigned a mobility factor value,
use a default value of 0.002 as the mobility factor
value for all these hazardous substances.
Differences Due to Karst














• If the entire interval from a source at the
site to the aquifer being evaluated is
karst, use the distribution coefficient
category "Karst" in MRS Table 3-8 in
assigning the mobility factor value. If
karst is present in the interval, but the
entire interval is not karst, then use the
step listed under "non-karst" instead of
the step in this column.
If a hazardous substance cannot be
assigned a mobility factor value because
data on its water solubility are not
available and the entire interval is karst,
use other hazardous substances for
which solubility information is available
to evaluate the pathway. I karst is
present in the interval, but the entire
interval is not karst, then use the step
listed under "non-karst" instead of the
step in this column.













































Section 7.2
                                                    144

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                                HIGHLIGHT 7-20
           SCORING CONSIDERATIONS FOR KARST AQUIFERS:
                           NEAREST WELL FACTOR
                Non-karst
      Differences Due to Karst
If for the aquifer being evaluated, there is an
observed release by direct observation for a
drinking water well within the TDL, assign Level
11 concentrations to the well.

However, if one or more samples meet the
criteria for an observed release for a target well
for the aquifer,  determine if that well is subject to
Level I or Level II concentrations  as specified in
MRS section 2.5.1 and 2.5.2.

If one or more target drinking water wells for the
aquifer are subject to Level I concentrations,
assign a factor value of 50.

If not, but if one or more target drinking water
wells for the aquifer are subject to Level II
concentrations, assign a factor value of 45.

If none of the target drinking water wells is
subject to Level I or Level II concentrations for
the aquifer, determine the shortest distance to
any drinking water well for the aquifer, as
measured  from any source at the site with a
ground water containment factor value greater
than 0. Select a value from MRS Table 3-11
based on this distance. Assign it  as the value for
the nearest well factor for the aquifer.	
 If none of the target drinking water wells
is subject to Level I or Level II
concentrations for the aquifer, and if one
of the aquifers being evaluated is a karst
aquifer that underlies any portion of the
sources at the site, and if any well draws
drinking water from this karst aquifer
within the TDL, assign  a value of 20 for
the nearest well factor for the aquifer.
                                         145
                                                                                     Section 7.2

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HIGHLIGHT 7-21
SCORING CONSIDERATIONS FOR KARST AQUIFERS:
POPULATION/POTENTIAL CONTAMINATION FACTOR
Non-karat
Determine the number of people served by drinking
water from points of withdrawal (for the aquifer being
evaluated) subject to potential contamination. Do not
include those people already counted under Level I
and/or Level II concentration factors.

! Use the "Non-karst" portion of MRS Table 3-12 for
that portion of the target population served by points
of withdrawal subject to potential contamination,
excluding any points of withdrawal that draw drinking
water from a karst aquifer that underlies any portion
of the sources at the site.
! Calculate the value for the population/potential
contamination factor as directed in MRS section
3.3.2.4.
Differences Due to Karst

• Use the "Karst' portion of MRS Table
3-12 to assign values only for that
portion of the target population served
by points of withdrawal that draw
drinking water from a karst aquifer
that underlies any portion of the
sources at the site.




b




TIPS AND REMINDERS

•   Karst aquifers that do  not underlie any portion of site sources are evaluated in the same manner as
   non-karst aquifers.

•   A significant percentage of karst in the U.S. occurs in limestone. The presence of springs, sinkholes
   and caverns in a limestone formation may be indicative of karst.

       Lava aquifers or aquifers with numerous abandoned mine shafts do not meet the MRS definition
       of karst and, even though hazardous substance transport may be facilitated in such aquifers,
       they cannot be considered karst aquifers for purposes of MRS scoring.
Section 7.2
                                            146

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SECTION 7.3
CONTAINMENT FACTOR
       This section provides definitions for many of the terms used in the ground water containment
descriptions and explains how to score the containment factor. If an observed release to an aquifer
cannot be established, then that aquifer is evaluated based on potential to release. Four factors are used
to evaluate the potential to release factor: containment, net precipitation, depth to aquifer, and travel
time. The containment factor is a measure of the methods (either natural or engineered) that have been
used to restrict the release of hazardous substances from a source to the subsurface or to prevent
released substances from entering ground water.

       Containment criteria have been compiled for several types of sources on a numerical scale
selected to provide a relative degree of discrimination among different levels of containment. HIRS
Table 3-2 includes containment factor rating descriptions for the following specific categories of
hazardous waste sources: surface impoundments, land treatment facilities, containers, and tanks. The
table also provides containment factor rating descriptions that apply to all other hazardous waste
sources, including landfills, piles, and contaminated soil.

       The containment factor is evaluated for each source for the aquifer being evaluated, and the
highest containment factor value for any source that meets the minimum size requirement is assigned as
the containment  factor value.  If none of the sources meets the minimum size requirement, the highest
containment factor value of any source is assigned.
                               RELEVANT MRS SECTION
        Section 3.1.2.1            Containment
DEFINITIONS

       The following definitions elaborate on terms used in the containment descriptions in MRS Table
3-2.
       Above-ground Tank:  Any tank that does not meet the definition of a below-ground tank
       (including any tank that is only partially below the surface).

       Associated Containment Structures: As used in MRS Table 3-2, constructed barriers (e.g.,
       liners, dikes, berms) that may have been placed under, over, or around a source (e.g., a landfill
       or a waste pile) to prevent the release of hazardous substances to the environment.

       Below-ground Tank:  A tank with its entire surface area below the surface and not visible;
       however, a fraction of its associated piping may be above the surface.

       Bulk Liquids:  Noncontainerized liquids  deposited directly into a source by pipe, tanker truck, or
       other means of transport.
                                           147                                    Section 7.3

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       Essentially Impervious Base:  A base underlying containers that is free from cracks and gaps
       and prevents penetration of leaks, spills, or precipitation.

       Evidence of Hazardous Substance Migration:  Chemical analyses and/or visual evidence that
       demonstrate hazardous substances attributable to a source have migrated away from that source
       into the surrounding soil, ground water, surface water, or air (e.g., leachate, containing
       hazardous substances coming out of the source;  stained or contaminated soil that can be
       attributed to migration from the source; evidence  of the overflow from a surface impoundment
       containing hazardous substances).

       Free Liquids:  Liquids that readily separate from the solid portion of a substance under ambient
       temperature and pressure.

       Freeboard: Vertical distance between the top of a tank or surface impoundment dike and the
       surface of the hazardous substance contained therein. Freeboard is intended to prevent
       overtopping resulting from normal or abnormal operations, wind and wave action, rainfall, and/or
       run-on.

       Functioning Ground Water Monitoring System: A system of test wells installed around a
       source to detect migration of hazardous substances. In evaluating the containment factor in the
       ground water pathway, wells should be sampled and maintained to constitute a functioning
       ground water monitoring system.

       Land Treatment Zone: Soil layer in the unsaturated zone  of a land treatment unit within which
       hazardous substances are intended to be degraded, transformed, or immobilized.

       Liner: A continuous barrier that covers all the earth likely to be in contact with a source so that
       hazardous substances or leachate containing hazardous substances would not migrate to the
       surrounding earth. The barrier may be synthetic material (e.g., a thick, continuous, polyethylene
       membrane) or engineered, compacted, natural material  (e.g.,  re-worked and low permeability
       clay). An in-situ clay layer that has not been re-engineered  by compaction or other methods is
       not considered a liner.

       Maintained Engineered Cover: Vegetated cover, usually  made of compacted clean soil. It is
       generally placed over a source at its closure and  is designed  and constructed to minimize the
       migration of liquids through the closed source, function with minimum maintenance, and
       accommodate settling and subsidence. Maintenance of the integrity and effectiveness of the
       final  cover may include repairing it as necessary to correct the effects of settling, subsidence,
       erosion, and other events.

       Secondary Containment: As used in MRS Table 3-2, secondary containment is applicable to
       the evaluation of the containment factor for tanks. Methods of secondary containment include a
       liner external to the tank, a vault, a double-walled tank, or an equivalent device.

       Tank and Ancillary Equipment:  Tanks and associated pipes, pumps, sumps, manifolds,
       fittings, flanges, and valves used to distribute, meter, or control flow of hazardous substances to
       or from the tank.

SCORING THE GROUND WATER CONTAINMENT FACTOR

(1)     Identify the sources at the site.  MRS section 1.1 defines  a source as many area where a
       hazardous substance has been  deposited, stored, disposed, or placed, plus those soils that
       have become contaminated from migration of a hazardous substance.0 The MRS divides
       sources into five categories for evaluating ground water containment: surface impoundments,
       land  treatment, containers, tanks, and all other sources. Each category has a separate list of
       criteria used to assign containment values.


Section 7.3                                     148

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(2)     Use MRS Table 3-2 to assign a containment value to each source. Use the definitions
       provided above to interpret the criteria in Table 3-2.Highlight 7-22 summarizes the types of
       information that generally should be collected during the SI for the purposes of evaluating the
       containment factor.

(3)     For each source for the aquifer being evaluated, determine whether the source hazardous
       waste quantity value is 0.5 or greater. Only sources with a source hazardous waste quantity
       value of 0.5 or greater can be used to assign the containment value, unless no source for the
       aquifer being evaluated has  a source hazardous waste quantity value of 0.5 or greater. This
       limitation is referred to as the "minimum size requirement". Highlight 7-23 summarizes the
       minimum measurements of sources that will give a source hazardous waste quantity value of
       0.5. Any of the hazardous waste quantity tiers can be used to determine whether a source meets
       the minimum size requirement. Detailed guidance on determining hazardous waste quantity
       values is provided in Chapters.

(4)     Assign a pathway containment factor value for the aquifer being evaluated.

               Assign the highest containment value for those sources with hazardous waste quantity
               values greater than or equal to 0.5 as the containment factor value for the ground water
               pathway.

               If none of the sources at the site for the aquifer being evaluated has a source
               hazardous waste quantity value of greater than or equal to 0.5, assign the  highest
               containment value among all sources as the containment factor value for the ground
               water pathway.


                                     HIGHLIGHT 7-22
             DATA NEEDS FOR EVALUATING SOURCE CONTAINMENT

   The following types of information are helpful for evaluating the containment factor:

           The physical location of the hazardous substance(s) (e.g., buried,  in a below-ground tank).

           Evidence of hazardous substance migration (e.g., overflow from surface Impoundments).

           Evidence, or lack thereof, of diking, berms, or other engineered physical barriers that completely
           surround the source area.

           The presence of bulk and/or free liquids.

           Evidence of liners that are continuous and that would prevent the source hazardous
           substance(s) from coming in contact with the earth beneath (or around) the source. In the case
           of liners, the site investigator may assume that there Is not a liner unless evidence indicates
           otherwise.

           Evidence, or lack thereof, of leachate collection systems (functioning or not), and ground water
           monitoring systems.

           Evidence of the existence and condition of physical structures that  provide protection from
           precipitation, and/or run-on  and runoff control.
   The above list is illustrative. It Is meant neither to be all inclusive of the types of information that can be
   used to characterize the containment of any particular hazardous substance source nor to establish
   minimum requirements.

                                              149                                      Section 7.3

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HIGHLIGHT 7-23
SOURCE MEASUREMENTS THAT MEET
THE MINIMUM SIZE REQUIREMENT
Tier
A
B
C
Volume






D
Area




Measure or Source Type
Hazardous constituent
quantity
Hazardous wastestream
quantity
Landfill
Surface impoundment
Surface impoundment
(Buried/backfilled)
Drums
Tanks and containers
other than drums
Contaminated soil
Pile
Other
Landfill
Surface impoundment
Surface impoundment
(buried/backfilled)
Land treatment
Pile
Contaminated soil
Minimum Measurements
for Hazardous Waste
Quantity Value of 0.5
0.5 pounds
2,500 pounds
1,250 cubic yards
1.25 cubic yards
1.25 cubic yards
250 gallons
1.25 cubic yards
1,250 cubic yards
1.25 cubic yards
1.25 cubic yards
1,700 square feet
6.50 square feet
6.50 square feet
135 square feet
6.50 square feet
17,000 square feet














Section 7.3
                                                    150

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TIPS AND REMINDERS

       Regardless of source type, if there is evidence of hazardous substance migration from the
       source, a containment factor value of 10 applies. Note that evidence of migration from a source
       does not have to meet the criteria for observed release.

       Every source may not be evaluated for every aquifer, depending on the location of the source
       and the hydrogeology in the area of the site. Only  sources for the aquifer being evaluated  are
       used in assigning the containment factor value for that  aquifer.

       Only those sources that have a non-zero containment factor value for ground water should  be
       evaluated.

       The presence of a liner that extends under the entire source area is considered when evaluating
       containment; if the liner does not extend under the entire source area (i.e., a partial liner), the
       source should be evaluated as if no liner were present. The condition of the liner (e.g., damaged,
       torn, or leaking) would typically not be discernible during the SI.

       A site may be considered to have a "natural" liner only  if the  clay underlying the site has been
       reworked to  provide an engineered barrier. The mere existence of a natural clay layer or a
       confining layer is not sufficient. However, such a layer would be accounted for when evaluating
       the travel time factor.

       Assign a containment factor value for only those sources with a source hazardous waste quantity
       value of 0.5  or more. If no source meets this minimum size requirement, select the highest
       containment factor value among all sources for the aquifer being evaluated as the containment
       factor value.

       Any hazardous waste quantity tier (A, B, C,  or D) can be used to determine if a source meets the
       minimum size requirement.
                                             151                                      Section 7.3

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SECTION  7.4
ACTUAL
CONTAMINATION
       This section provides guidance on identifying drinking water wells subject to actual
contamination, determining whether wells subject to actual contamination have Level I or Level II
concentrations, and scoring sites with actual contamination. A drinking water well is subject to actual
contamination if it meets specific criteria that demonstrate that the well has been contaminated by
hazardous substances attributable to the site. Target drinking water wells at which actual contamination
is not documented are evaluated based on potential contamination. All wells subject to actual
contamination are classified as Level I or Level II. Wells subject to actual contamination receive higher
values for several factors.
                             RELEVANT MRS SECTIONS

        Section 2.3             Likelihood of release
        Section 2.5             Targets
        Section 2.5.1           Determination of level of actual contamination at sampling location
        Section 2.5.2           Comparison to benchmarks
        Section 3.1.1           Observed release
        Section 3.3.1           Nearest well
        Section 3.3.2.1          Level of contamination
        Section 3.3.2.2          Level I concentrations
        Section 3.3.2.3          Level II concentrations
DEFINITIONS
       Actual Contamination In the Ground Water Pathway: A drinking water well is subject to actual
       contamination if a sample from the well meets the criteria for an observed release. (Highlight
       7-24 discusses the difference between actual contamination and observed release.) Actual
       contamination of a drinking water well cannot be inferred based on other samples (e.g., from
       downgradient wells).

       Level I Concentrations for the Ground Water Pathway: Level  I concentrations are established
       in samples from drinking water wells in which the concentration of a hazardous substance that
       meets the criteria for an observed release is at or above  its drinking water benchmark. A
       drinking water well also may be subject to Level I concentrations if multiple hazardous
       substances that meet the criteria for an observed release are present below their respective
       benchmarks, and the I or J index is greater than or equal to one. Benchmarks for the ground
       water pathway include MCLs, nonzero MCLGs, and screening concentrations for cancer and
       chronic noncancer effects.
                                           153                                  Section 7.4

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                                    HIGHLIGHT 7-24
     COMPARISON OF ACTUAL CONTAMINATION TO OBSERVED RELEASE

 Because actual contamination involves observed release as part of its definition, the two concepts are
 often confused. Observed release is a necessary but not sufficient condition for establishing actual
 contamination of specific targets. Scoring an observed release to ground water generally involves
 detecting a hazardous substance (attributable to the site) in ground water samples at levels significantly
 above background for the site. The samples thatare used to score an observed  release can be taken
 from any  well - monitoring wells,  drinking water  wells, or other types of wells.  Scoring  actual
 contamination requires that the same criteria for an observed release be met, but the samples meeting
 these criteria must be taken from drinking water wells. If the only ground water samples that show
 hazardous substances at levels significantly above background (i.e., an observed release) are taken
 from monitoring wells, no actual contamination can be scored.  In  addition, an observed release to
 ground water can sometimes be scored by direct observation  (e.g., by documenting deposition of
 hazardous substances in the aquifer). Actual contamination of a drinking water well can be documented
 by direct observation only if hazardous substances were disposed in the well itself or were observed
 entering the well, both of which are unlikely scenarios. If actual contamination cannot be scored, all
 targets are scored based on potential contamination. In essence, for the ground water pathway, actual
 contamination is a concept that applies only to targets and target locations, while observed release is
 not so restricted.
       Level II Concentrations for the Ground Water Pathway: Level II concentrations are
       established in samples from drinking water wells in which the concentration of at least one
       hazardous substance meets the criteria for an observed release, but the conditions for Level I
       concentrations are not met. In addition, Level II is assigned for observed releases established by
       direct observation.

       Highlight 7-25 illustrates wells with Level  I, Level II, and potential contamination.

ESTABLISHING ACTUAL CONTAMINATION

       The steps outlined below describe how to  establish actual contamination based on chemical
analysis for a single hazardous substance. Actual  contamination based on direct observation is not
discussed. These steps explain how to meet the observed release criteria at a target well and should be
repeated for other hazardous substances to establish actual contamination for each individual hazardous
substance, or to establish Level I contamination based on several  hazardous substances using the I or J
index. The data needed to establish actual contamination are summarized \r\Highlight 7-26.

(1)     Compile analytical results that indicate  that a hazardous substance has been detected in
       a drinking water well. Results that show  hazardous substances in monitoring wells cannot be
       used to document actual contamination, except for possible use as a background in establishing
       the observed release.

(2)     Determine the background level for the  hazardous substance. Determining the appropriate
       background level requires analytical results from an appropriate background well for substances
       that could be naturally occurring, ubiquitous, or attributable to other sources in the areas. A
       background level of 0 can be assumed for substances that are neither naturally occurring,
       ubiquitous, nor attributable to other sources in the areas (i.e., a background sample may not be
       needed). See Chapter 5 for information on determining the appropriate background level for
       comparison with a drinking water well sample.

(3)     Determine whether the concentration of the hazardous substance is significantly above
       background. Detailed guidance for making this determination  is found in Section 5.1,
       particularly Highlight 5-2.


Section 7.4                                     1 54

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                             HIGHLIGHT 7-25
                  EXAMPLES OF WELLS SUBJECT TO
        LEVEL I, LEVEL II, AND POTENTIAL CONTAMINATION
   Monitoring well #1
   (background)
   Nickel = 100 ppb
   SQL = 50 ppb
        Level II
                                                            Level I
Drinking water well #2
Nickel = 400 ppb
SQL = 50 ppb
Drinking water well #1
Nickel = 800 ppb
SQL = 50 ppb
                                     Potential
                              Drinking water well #3
                              Nickel = 200 ppb
                              SQL = SO ppb
   Drinking water wells #1 and #2 are subject to actual contamination.  The concentration of nickel is
   above the SQL (50 ppb) and greater than three times the background level (3 x 100 ppb = 300 ppb)
   at both wells.  The ground water benchmark for nickel is 700 ppb.

   —      Drinking water well #1 is subject to Level I contamination. The concentration of nickel (800
          ppb) is higher than the benchmark of 700 ppb.

   —      Drinking water well #2 is subject to Level II contamination. The concentration of nickel (400
          ppb) is lower than the benchmark of 700 ppb.

   Drinking water well #3 is subject to potential contamination. The concentration of nickel (200 ppb)
   is above the SQL, but less than three times the background level.
                                     155
                         Section 7.4

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                                   HIGHLIGHT 7-26
                  DATA NEEDS FOR LEVEL OF CONTAMINATION

 Actual Contamination

        Analytical results for drinking water wells

        —     Concentrations of hazardous substances present in samples
        —     Applicable DLs (i.e., SQL, CRQL, or DQ for hazardous substances in each sample.

        Background concentrations and applicable DLs of those hazardous substances detected in
        drinking water wells that are being used to document actual contamination

        —     Should be comparable analytical results if hazardous substances could be naturally
               occurring, ubiquitous, or attributable to other sources in the area
        —     If substances are not naturally occurring, not ubiquitous, and there are no other
               potential sources of that hazardous substance in the area, a background
               concentration of 0 can be assumed.

 Level I or Level II

        Information listed above for actual contamination

        Health-based benchmarks for ground water for substances that meet observed release
        criteria (available in SCDM)
(4)     Determine whether the hazardous substance can be attributed to the site. Sampling results
       or records (e.g., manifests) indicating the presence of the hazardous substance in a source or
       sources at the site are the strongest documentation. Information that the hazardous substance
       was used at the facility also may be acceptable. See Chapter 5 for additional guidance on
       attribution, including attribution of degradation products.

(5)     Repeat this process for as many  hazardous substances as feasible at the site.

DETERMINING LEVEL OF CONTAMINATION

       The steps outlined below and in the flowchart \r\Highlight 7-27 describe how to determine
whether a target well should be scored as Level I, Level II, or potential contamination for an aquifer.

(1)     Determine which wells are target wells for the aquifer being evaluated and perform Steps
       (2) through (4) for each well.

(2)     Determine whether actual contamination can be established for any hazardous substance
       detected  in the well. If actual contamination cannot be established (using the seven steps
       outlined above), score the well under potential contamination. If the well has not been sampled,
       score it under potential contamination, even  if actual contamination has been established at
       downgradient wells. Note that if a well in an upper aquifer is subject to actual contamination and
       that well is also a target well for a lower aquifer, then that well is to be evaluated based on actual
       contamination when scoring the lower aquifer (see Section 7.9, Example 3).

(3)     Compare the concentration of each hazardous substance that meets the observed release
       criteria for the well with its applicable benchmark for the ground water pathway.
       Benchmarks are available in SCDM. If more  than one benchmark applies (e.g., an MCL and a
Section 7.4                                     1 56

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                           HIGHLIGHT 7-27
  FLOWCHART FOR DETERMINING LEVEL I,  LEVEL
               OR POTENTIAL CONTAMINATION
   Has an observed release been
documented at the target weB f or one
  or more hazardous substances?
  Is concentration greater than or
 equal to the benchmark f or any shgle
      hazardous substance?
  Is there more than one hazardous
     substance that meets the
    observed release criteria?
  Score targets for
potential contamination
Score targets as Level I.
                                  NO
Score targets as Level II.
                     Make two lists of hazardous substances that meet observed release criteria:

                     1) Hazardous substances wSh screening concentrations for cancer risk;
                     2) Hazardous substances win screening concentrations for noncancer effects.

                     Calculate I for hazardous substances in ft,
                     Calculate J for hazardous substances in #2.
                           YES
                                                                 Score targets as Level I.
                   NO
                                                                 Score targets as Level II.
                                      157
                       Section 7.4

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       screening concentration), then make the comparison only to the benchmark with the lowest
       concentration.

              If the concentration of any one or more of these hazardous substances is greater than or
              equal to its benchmark, score the well as Level I. Continue with the guidance provided in
              Section 7.5.

              If only one hazardous substance meets the observed release criteria and its
              concentration is less than its benchmark, score the well as Level II. Continue with the
              guidance provided in Section 7.5.

              If more than one hazardous substance meets the observed release criteria, but no single
              substance establishes Level I, continue to Step (4).


(4)     Calculate the I and J indices for all hazardous substances for this well that meet the
       observed release criteria. Make two lists of substances that meet the observed release criteria:
       hazardous substances with screening concentrations for cancer risk; and hazardous substances
       with screening concentrations for noncancer effects. Each hazardous substance may be on one,
       neither, or both of the lists. If more than one sample has been taken from a well and these
       samples are comparable (e.g., taken in the same time frame, collected using the same field
       techniques, analyzed by the same methods), for each hazardous substance, select the highest
       concentration to use in the calculations below.

              Calculate the I index for all hazardous substances with screening concentrations for
              cancer risk that meet the observed release criteria, using the following equation:


                                            ,-LC>
                                                /-1 SC,
       where: Cj      =      concentration of substance i in well;
              SCj     =      screening concentration for cancer risk, which is the concentration
                             corresponding to 10s individual cancer risk for oral exposure for
                             hazardous substance i; and
              n       =      number of hazardous substances that meet observed release criteria
                             and for which an SC is available.

              Calculate the J index for all hazardous substances with screening concentrations for
              noncancer effects that meet the observed release criteria, using the following equation:
       where: Cj      =      concentration of substance j in well;
              CRj     =      screening concentration for noncancer effects, which is the
                             concentration corresponding to the reference dose for oral exposure for
                             hazardous substance j; and
              m      =      number of hazardous substances (1) that meet observed release criteria
                             and (2) for which a CR is available.

              If either the I or J index is greater than or equal to 1, score the well as Level I. If both the
              I  and J indices are less than one, score the well at Level II. An example of calculating
              the I and J indices is presented \r\Highlight 7-28.

Section 7.4                                     1 58

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HIGHLIGHT 7-28
CALCULATING 1 AND J INDICES
A well contains chemicals in the concentrations listed below. While no one of the chemicals alone was found in a
concentration that would place the well in Level 1, consideration of the chemicals in combination places the well
in this category. When the 1 and J indices are calculated, the value for is greater than 1 (i.e., 1 .4) and the well is
scored as Level I. This is true even though the J index is less than 1.

Chemical
X
Y
Z
Concentration
c,
(mg/L)
4.7 x10'4
3.1 x10'4
1.5 x10'4
Cancer Risk Screening
Conentration
SC;
(mg/L)
6.3 x10'4
4.2 x10-3
2.8 x10'4
Ci/SC;
0.75
0.074
0.54
I
1.36


Chemical
X
Y
Z
Concentration
Cj
(mg/L)
4.7 x10'4
3.1 x10'4
1.5 x10'4
Reference Dose
Screening
Concentration
CRj
(mg/L)
1.6x10-1
6.7 x10-1
2.8 x10-1
C/CRj
0.0029
0.00046
0.00054
J
0.0039


SCORING SITES WITH ACTUAL CONTAMINATION

       The determination of level of contamination is necessary to score the nearest well and
population factors. In addition, establishing actual contamination may affect the minimum value for the
hazardous waste quantity factor. Highlight 7-29 summarizes the differences in scoring among wells
subject to Level I Level II, or potential contamination. Detailed instructions for scoring nearest well and
population factors for wells subject to  actual contamination are provided in Section 7.5.

       Highlight 7-30 illustrates scoring for Level I, Level II, and potential targets.
                                            159
Section 7.4

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                                  HIGHLIGHT 7-29
                  COMPARISON OF SCORING LEVEL I, LEVEL II,
                        AND POTENTIAL CONTAMINATION
Level of
Contamination
Actual - Level 1
Actual - Level II
Potential
Nearest Well Factor Value
50
45
0 to 20 - depends on distance
to nearest drinking water well
and presence of karst
Population Factor
Value
10 x number of people
1 x number of people
0.1 x distance-
weighted population
Minimum
HWQ Factor
Value3
100
100
10b
          a Minimum hazardous waste quantity factor values apply if Tier A is not adequately determined
          for all sources.
          b May be 100 in certain cases when there has been a removal action; see MRS section 2.4.2.2
   and EPA's removal policy fact sheet.
Section 7.4
                                         160

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                               HIGHLIGHT 7-30
          SCORING GROUND WATER POPULATION SUBJECT TO
           LEVEL I, LEVEL II, AND POTENTIAL CONTAMINATION
        Monitoring well #1
        (background)
                                                               Level I
           Level II
   Drinking water well #2
   0.7 miles from source
   Serves 340 people
                            Drinking water well #1
                            0.1 miles from source
                            Serves 150 people
                             Potential
                       Drinking water well #3
                       0.8 miles from source
                       Serves 720 people
             Factor

             Level I:
             Level II:
             Potential8:

             Population factor:
                    Factor Value
150    X
340    X
167    X
                           1,857
       a Because the wells are not in a karst aquifer, use the "other than karst" portion of HRS Table 3-12 to determine
the distance-weighted population value.  For a drinking water well 0.8 miles from the source, serving 720 people, the
distance-weighted population value is 167.
                                        161
                                                    Section 7.4

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TIPS AND REMINDERS

       Actual contamination cannot occur without an observed release, but an observed release does
       not necessarily establish actual contamination. Hazardous substances detected in drinking water
       wells or monitoring wells may be used to document a release; however, only hazardous
       substances in drinking water wells may be used to document actual contamination.

       Documenting actual contamination in a municipal well (or other wells serving multiple families)
       will generally result in a large number of targets points. Documenting one municipal well subject
       to actual contamination may provide a score greater than the cutoff. Consider sampling these
       types of wells if there is a possibility that they may be contaminated.

       If there is no Level I contamination, documenting actual contamination (Level II) in a single
       residential well results in 45 targets points for the nearest well factor plus one point for each
       person served  by that well. Unless contamination is at Level I, actual contamination in additional
       residential wells may result in only a moderate number of additional targets points (i.e., one point
       per person served) and requires considerable effort and expense.

       Actual contamination cannot be inferred, even for wells that are within the TDL and between
       groups of contaminated wells.

       Former drinking water wells that have been abandoned can be scored based on actual
       contamination if (1) analytical data indicate an observed release at the wells when they were in
       use, and (2) the wells were closed because of site-related contamination.

       Assuming a maximum value for waste characteristics, for a site to score greater than or equal to
       the cutoff on the basis  of actual contamination:

       —     At least four people must be exposed at Level I contamination, assuming no Level II or
              potential populations;
       —     At least 41 people must be exposed at Level II contamination, assuming no Level I or
              potential populations; or
       —     Various combinations of populations  may be exposed, such as two people exposed at
              Level I and 16  people exposed at Level II.

       Assign a minimum hazardous waste quantity  factor value of 100 for the ground water pathway if
       a drinking water well is actually contaminated for any aquifer (not just the one being evaluated)
       and Tier A is not adequately determined for all sources.

       If wells in an upper aquifer that are subject to actual contamination are also target wells for a
       lower (non-interconnected) aquifer, then these wells still are evaluated based on actual
       contamination  when scoring the lower aquifer. The likelihood of release value, however, is
       based on the lower aquifer (see Section 7.9,  Example 3).

       In determining  Level I contamination, if multiple benchmarks (e.g., an MCL and a cancer risk
       screening concentration) apply to a hazardous substance, use the benchmark with the lowest
       concentration in making the comparison.
Section 7.4                                     162

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SECTION  7.5
POPULATION AND
NEAREST WELL FACTORS
       The population factor in the ground water pathway evaluates the number of residents, students,
and workers served by ground water wells (in the aquifer being evaluated and appropriate overlying
aquifers) located within the TDL. The nearest well factor evaluates the threat to the maximally exposed
individual and takes into account whether that individual is subject to actual or potential contamination.
This section explains how to  estimate the population (i.e., residents, students, and workers) that regularly
uses ground water from wells within the TDL, how to score the ground water population factor, and how
to score the nearest well factor.

       The ground water population  is the people served by wells located within the TDL, not the
residents living within the TDL (see Highlight 7-31). People living within the TDL may obtain drinking
water from wells outside the TDL or from surface water sources, and people living outside the TDL may
obtain drinking water from wells located within the TDL.
                             RELEVANT MRS SECTIONS
          Section 3.0.1           General considerations
          Section 3.0.1.1         Target distance limit
          Section 3.3.1           Nearestwell
          Section 3.3.2           Population
DEFINITIONS
       Nearest Well Factor: Factor for evaluating the maximally exposed well. This factor is based on
       the presence of actual contamination or, for aquifers where no drinking water well is subject to
       actual contamination, the presence of karst and distance to nearest drinking water well.

       Population for the Ground Water Pathway: Number of residents, students, and workers
       regularly served by wells that are located within the TDL for the aquifer being evaluated (and
       appropriate overlying aquifers). This population does not include transient populations, such as
       hotel and restaurant  patrons, but may include seasonal  populations (e.g., a resort area).

       Students: Full- or part-time attendees of an educational institution or day care that is served by
       a well located within the TDL.

       Target Distance Categories: Concentric rings (not necessarily circular) with radii 1/4, 1/2, 1, 2,
       3, and 4 miles from the sources at the site. These distance  categories are used to group the
       wells subject to potential contamination for distance weighting.

       Target Distance Limit for the Ground Water Migration Pathway: The  distance over which
       targets are evaluated. The TDL is generally a 4-mile radius from sources at the site, except:
                                          163                                   Section 7.5

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                                           HIGHLIGHT 7-31
                  IDENTIFYING TARGET AND NON-TARGET RESIDENCES
Area served b
x x X
v X X
X
yyWell B
L X fe
X \i/
x WetlB
X
                                                              Area sorvod by Well A
                                               Source
                                                            4 miles
                Area served by Well/
o     oo     o      o
                                                                                o     o
      X indicates a residence served by a target well
      O Indicates a residence served by a non-target well


      All  persons  living in residences  served by Wells A and B are included in estimating the ground water
      population. Because Well C is outside the TDL, persons served by Well C are not included in the ground water
      population.


      NOTE:  The situation above is presented for illustration purposes only.  Typically, water from wells in a
              municipal system is blended together and distributed to residences in the municipal system. That is,
              a single municipal well generally does not serve a particular group of residences.  Guidance on
              scoring blended water supplies is provided in Section 7.6.

Section 7.5
                                                   164

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              Include any drinking water well with an observed release attributed to the site, regardless
              of its distance from the source.

              Exclude wells completed in portions of an aquifer that are beyond an aquifer
              discontinuity (see Section 7.1).

       Target Wells for Aquifer Being Evaluated: Wells that are located within the TDL, and drawing
       water from the aquifer being evaluated or  an  overlying aquifer through which hazardous
       substances would migrate.

       Workers: Permanent employees (part-time or full-time) of a facility or business that is served by
       a well located within the TDL.

EVALUATING THE GROUND WATER POPULATION FACTOR

       The steps below describe an approach to estimating the population served by target wells for the
aquifer being evaluated. First, contact water authorities that have wells within the TDL to determine or
estimate the population served by municipal water  systems. (SeeHighlight 7-32 for data needs that the
water authority may be able to fulfill.) If the water authority provides an estimate of the population served
by the system, use that number for your ground water  target calculations. The water authority should
know if the  population served includes workers and/or students in addition to residents.  If the population
estimate does not include workers and/or students, it may be possible to modify the following
methodology. The assumptions used should be clearly presented in the documentation record.

       If the water authority provides just the total number of connections, then estimate the population
served by multiplying the number of connections by the county average number of persons per
household.  After making an initial estimate of residential  population served, estimate any student and
worker populations served by the municipal system, and  adjust the total. Next, evaluate  residential
populations served by private wells within the TDL. At  each  stage,  evaluate whether documenting
additional population will be important to the site score.

       Depending on site circumstances, the  scorer may conduct these steps in a different order. For
example, if  many people within the TDL use private wells or if private wells are subject to actual
contamination, it may be more efficient to consider residential populations served by private wells
before considering student or worker populations served by municipal connections.

(1)     Draw target distance categories. Draw concentric rings with radii 1/4, 1/2,  1, 2, 3, and 4 miles
       on a topographic map from the edges of the source. If there is an aquifer discontinuity, exclude
       any areas beyond the discontinuity.  Remember that any well with a documented observed
       release attributable to the site is evaluated regardless of its distance from sources.

(2)     Identity all municipal systems with target wells for the aquifer being evaluated. Repeat
       Steps (3) through  (5)  for  each system if more than one municipal system has wells within the
       TDL. If no municipal system has a well within the TDL, proceed to Step (7).

(3)     Identify all system water supply units In the aquifer being  evaluated or an overlying
       aquifer.  These units may include drinking  water wells and standby wells.  If the  municipal system
       is a blended system, identify all wells inside and  outside the TDL. Also identify all surface water
       intakes and standby intakes contributing  to a blended system.

(4)     Evaluate the population served by the municipal water system, assuming all service
       connections are  residential.  Because connections to schools or businesses generally serve
       more individuals than those in a typical household, this assumption may result in a lower
       estimate of the target population. If this assumption  yields a high score, however, time
       consuming inquiries to document student or worker populations may  be avoided.
                                             165                                     Section 7.5

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                                     HIGHLIGHT 7-32
                  DATA NEEDS FOR GROUND WATER POPULATION
 Obtain from Local, Municipal, or Other Water Authorities:
        Location of all municipal wells within the TDL and the aquifer(s) in which each is completed
        Number of persons reserved or service connections for each well that is not part of a blended system
        —      If number of persons is provided, determine if number includes students and/or workers
        —      If number of service connections is provided, obtain any available information about breakdown
                for connections to residences, schools, and businesses
        For wells in a blended system:
        —      Total  number of wells and intakes in the system (including those outside the TDL)
        —      Total  population served or number of service connections
        —      Whether any well  of intake provides more that 40 percent of the system's water
        —      Average annual pumpage or capacity for each well (only needed if the water authority
                states that one well provides note that 40 percent of the system's water, or if the
                percent contribution of each well to the system needs to be  determined by calculation)
        Delineation of areas within the TDL served by municipal water system
 Obtain from Local Health Department, Water Commission, or Other Entity:
        Delineation of areas within the TDL not connected to the municipal system
        Information on where residents in these areas obtain water
 Obtain from U.S. Bureau of Census Reports:
        Average number of persons per residence for each county served by target wells in the aquifer
        being evaluated.
 Obtain from Business  and Schools:
        Information on how they obtain water
        Number of workers and/or students
Section 7.5                                     166

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              Locate target municipal wells. Mark all municipal wells located within the TDL and
              completed in the aquifer being evaluated (or an overlying aquifer) on the map.

              Estimate population served by municipal wells, assuming all residential connections.

              —      Independent systems. If a single well serves a particular group of residences
                      and is not blended with water from other wells or surface water intakes,
                      determine the number of service connections for that well. Multiply the number
                      of connections by the county average number of persons per residence from, for
                      example, U.S. Bureau of Census reports.

              —      Blended systems.  If the wells are part of a blended system, obtain information
                      about the entire system in order to apportion the total population served to each
                      well or intake. The necessary data include:

                             total number of people served or service connections for the blended
                             system;

                             number of wells inside the TDL;

                             number of wells outside the TDL;

                             number of surface water intakes in the system;

                             whether any individual well or intake provides more than 40 percent of
                             the water to the system; and

                             whether any wells or intakes are standby wells or intakes.

                      If any one well or intake provides more than 40  percent of the water to the
                      system, collect data on the annual average pumpage or capacity for each well or
                      intake (see Section 7.6, which provides additional information on apportioning
                      population in blended systems). Multiply the number of service  connections
                      assigned to  each well within the TDL by the average number of persons per
                      residence.

              Identify any municipal wells subject to Level  I or Level II concentrations for the aquifer
              being evaluated. (See Section 7.4.) Keep a separate count of persons served by wells
              contaminated at Level I or  Level II; do not count them in the population subject to
              potential contamination for that aquifer. Tabulate data on number of persons served by
              level of contamination and, for wells subject to potential contamination,  by
              karst/non-karst and target distance category.

(12)    Calculate a population factor value, assuming all residential connections.  Highlight 7-33
       illustrates tabulating populations and calculating the  population factor value.

              Multiply the total number of individuals served by wells subject to Level I concentrations
              by 10.

              Multiply the total number of individuals served by wells subject to Level II concentrations
              by 1.

              Use MRS Table 3-12 to assign a distance-weighted population value for karst and non-
              karst for populations served by wells subject to potential contamination. For each target
              distance category, sum the karst and non-karst distance-weighted population values.
              Multiply the total distance-weighted population value by 1/10.
                                             167                                      Section 7.5

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HIGHLIGHT 7-33
DOCUMENT GROUND WATER POPULATION FOR AN AQUIFER a
are
tabl
Level 1 Concentrations
Level 1 Well
W-1
Population (individuals)
4
Reference b
32,10, 11
Level I Concentrations Factor Value: 1 x4 =40
Level II Concentrations
Level II Well
W-2
W-3
Population (individuals)
3
4
Level
Reference b
32, 10, 12,
32, 10, 13
II Concentration Factor Value: 1 x [3 + 4] = 7
Potential Contamination
Distance Category
(miles)
0 to 1/4
>1/4to 1/2
>1/2to1
>1 to 2
>2to3
>3to4
Population
(individuals)
None
None
3241
3241
8052
None
Distance-weighted
Population Value
(other than karst)
0
0
1669
939
678
0
Reference b


30,25, 18
30,25, 18
31,25, 18

Potential Contamination Factor Value: 1/1 Ox [1669 + 939 + 678] = 329
Total Population Factor Value: 40 + 70 + 329 = 376

a The document should identify in which aquifer the well being evaluated is screened. All wells in this example
assumed to be screened in the same aquifer. If wells were completed in more than one aquifer, add a column to the
3 that identifies the aquifer.
b The numbers in the reference column would identify particular references in the MRS scoring package.
Section 7.5
                                                    168

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              Sum the values calculated for Level I, Level II, and potential contamination to obtain the
              population factor value (for municipal wells, assuming residential connections only).

(6)     Determine if documenting student or worker populations Is cost effective. If it is, continue
       to Step (7). If not, proceed to Step (9). In making this decision, consider:

              Ground water pathway score assuming all residential connections. If the ground water
              pathway scores well over 100 by assuming all residential connections, it may not be
              cost-effective to document the student or worker populations. However, note the
              presence of student or worker populations using wells within the TDL in the
              documentation record.

              Position within ranges for determining distance-weighted population. If the  population
              served by municipal wells located in a particular target distance category is in the lower
              part or middle of a broad range (MRS Table 3-12), documenting students and workers
              may not change the population factor value. However,  if the population served by
              municipal wells is near the upper end  of a  range, a substantially higher population factor
              value might be achieved by  documenting the students and workers. If the population  is
              at the lower end of a range, evaluating the student or worker population may help
              solidify the score.

(7)     Document student and/or worker  populations.

              Identify schools and businesses served by wells within the TDL. Obtain information from
              water authorities on schools and businesses served by the municipal system. Identify
              schools or businesses within the TDL  that do not use municipal water (and thus may
              have a private well).

              —      Document any schools or businesses served by wells subject to  actual
                      contamination.

              —      For potential contamination, focus efforts generally on large schools (e.g.,
                      universities) or schools and businesses that are supplied by wells in the closer
                      target distance categories.

              —      For any newly identified private well, document that it is completed in the aquifer
                      being evaluated or an overlying aquifer.

              Document the number of students or workers for those schools or businesses identified.

              —      Contact the school officials to document student population.

              —      Contact the business in question to document worker population, or refer to
                      business census data.

(8)     Calculate a population factor value that Includes the student/worker populations. Follow
       the procedure outlined in Step (5) above. Be sure to subtract any service connections to schools
       or businesses from the total number of service connections (i.e., no longer assume all service
       connections are residential).

(9)     Evaluate population served by private/community wells within the TDL.

              Delineate areas served by municipal and private/community wells.
                                             169                                      Section 7.5

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              —     Municipal wells. Some areas may be served by water systems with no wells
                     within the TDL. Mark these areas on a topographic map(s). Generally exclude
                     these areas from the evaluation of private/community wells.

              —     Private/community wells. If some areas within the TDL are not supplied by a
                     municipal water system, determine if they use private/ community wells
                     (completed in the aquifer being evaluated or an overlying aquifer). Sources of
                     this information  include local agencies such as: water authority, public health
                     department, or water commission. It may be helpful to mark areas that rely on
                     private or community wells on a map.

              Estimate population served by private/community wells. Refer to the areas served by
              private/community wells (perhaps using the reference map). Use the most accurate
              information available to  document this population. Computerized census data for small
              areas (e.g., block-by-block) are likely to be most accurate. If such data are not available,
              count the number of houses within these areas for each target distance category as
              indicated on a topographic map and multiply this number by the county average number
              of persons per residence.  If the USGS map is outdated due to recent population growth
              (e.g., a new residential development), consider supplementing this house count using
              land use maps, aerial photographs, field  counts, or other methods.

(10)    Revise the tabulation of ground water population from Step (5). Add the number of persons
       served by private wells to the  appropriate  category based on level of contamination and, for
       wells subject to potential  contamination, karst/non-karst and target distance category. Use this
       revised tabulation to calculate a new population factor value.

(11)    Calculate a population factor value that Includes populations served by private  wells.
       Follow the procedure outlined in Step (5) above.

Highlight 7-34 provides an example of scoring the ground water population factor.

EVALUATING THE  NEAREST WELL FACTOR

       In evaluating the nearest well factor, consider all target drinking water wells for the aquifer being
evaluated used by residents, students, or workers. Do not consider wells other than drinking water wells,
nor wells used exclusively by transient populations.

(1)     Determine  If any drinking water well Is scored based on actual contamination for the
       aquifer being evaluated. If not, continue to Step (2). If so, score the  nearest well factor as
       follows:

              If any target drinking water well is subject to Level I concentrations, assign a  factor value
              of 50.

              If any target drinking water well is subject to Level II concentrations, but no well is
              subject to Level I concentrations, assign  a factor value of 45.

(2)     Determine  If any target drinking water well for the aquifer being evaluated Is In a karst
       aquifer that underlies any portion  of the sources at the site. If not, continue to Step (3). If
       so, assign a nearest well factor value of 20.

(3)     Determine  the shortest  distance to any target drinking water well for the aquifer being
       evaluated from any source at the site with a ground water containment factor value
       greater than 0. Use MRS Table 3-11 to assign a nearest well factor value based on this
       distance.
Section 7.5                                     1 70

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                                 HIGHLIGHT 7-34
   SCORING EXAMPLE OF GROUND WATER POPULATION FACTOR

Water Supply:   Blended municipal system consisting of 12 wells. No single well or intake supplies
                more than 40 percent of the system's water.

Location  of
Water Supply:   Two of the municipal wells are located within the TDL;

                W-A in the >1/2 -1 mile category, and

                W-B in the >1  - 2 mile category.

                Neither well is subject to actual contamination. Both wells are completed in the
                aquifer being evaluated, which is non-karst.

Evaluation:      The total number of service connections for the municipal system is 69,840. The
                entire area served by the municipal system lies within one county. 1990 census data
                indicate that the average number of persons per residence for that county is 2.8.
                Assuming all connections are residential,the total population served by the system
                is:

                      69,840X2.8 = 195,552

                Because no single well supplies more than 40 percent of the blended system's water,
                the scorer apportions the population equally to all 12 wells (see  section 7.6 for
                guidance on evaluating blended systems):

                     W-A: (1/12) X (195,552) = 16,296 persons

                     W-A: (1/12) X (195,552) = 16,296 persons

                Use MRS Table 3-12 to assign distance-weighted population values to each well for
                the aquifer.
Potential Contamination
Distance Category
(miles)
Oto 1/4
>1/4to 1/2
1/2 to 1
>1 to 2
>2to3
>3to4
Population
(individuals)
None
None
16,296
16,296
None
None
Distance-weighted Population
Value
(other than karst)
0
0
5,224
2,939
0
0
Potential Contamination Factor Value: 1/10 x [5,224 + 2,939]
= 816
               Because no well is subject to actual contamination:

                       Population Factor Value = 816
                                         171
                                                                                    Section 7.5

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EVALUATING GROUND WATER PATHWAY WHEN MULTIPLE SOURCES ARE
PRESENT

       This section presents two methods that may be used to evaluate the potential contamination and
nearest well factors when multiple sources are present at a site.

(2)     In the first method (see Highlight 7-35), draw distance categories independently around every
       source, determine aggregate distance categories (e.g., make overlapping rings of the same
       distance category), and total the population subject to potential contamination from drinking
       water wells for each distance category. The total populations for each distance  category are then
       used to determine the potential contamination factor value. Individuals are counted only once
       (except when  an individual is a resident and a student or worker), in the distance category for the
       well nearest to a source and used by the individual. The distance to the nearest well is the
       shortest distance from any source with ground water containment greater than 0 to any target
       drinking water well for the aquifer being evaluated. At sites with a large number of sources, this
       method may be time-consuming and inefficient. Because factor values are assigned based on
       population range within distance categories, a simplified method may be used with little or no
       impact on the pathway score.

(3)     In this method (see Highlight 7-36),  the nearest well is measured from any eligible source (i.e.,
       as in the first method).  However, rather than calculate the population subject to potential
       contamination for all sources, the scorer determines which source or sources will give the most
       representative score for the site based on distances to wells from each source and populations
       served by each well. Distance categories are drawn only for this source (or sources). This
       method is most effective for sites with a large number of sources and for sites with large
       populations using wells within the  TDL. Note, however, that this method may underestimate
       target scores.
Section 7.5                                     1 72

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                                    HIGHLIGHT 7-35
       ESTABLISHING TARGET DISTANCE CATEGORIES:  METHOD 1
Well
W1 - Population = 750
W2 - Population = 1000
W3 - Population = 3000
W4 - Population = 1500
Nearest Well Value = 9

Potential Contamination Factor
Value = 72
(Well 1, > 1/2 to  1 mile from
Source 2)

(>1/2to1 mile = 750
>1 to 2 miles  = 1500
>2 to 3 miles  = 3000
>3 to 4 miles  =1000)
        Measure the nearest well distance from the nearest source.
        Draw distance categories around every source, and then determine aggregate distance categories.

        Sum the population subject to potential contamination assigned to wells within  each  specified
        distance category to determine the total  population for each distance category  (e.g.,  sum the
        populations subject to potential contamination for >1  to 2 mile distance for all sources to get a total
        potential contamination population value for the >1 to 2 mile distance category).

        Count individuals only once (except when an individual is a worker, student, and/or resident). Assign
        each target well to the distance category nearest to a source (e.g., Well 4 in this diagram  would be
        counted only in the 1 to 2 mile distance category for  Source 4 and would not be counted for other
        sources).

        This method may be unwieldy and time-consuming for  sites with many sources.  For such sites, a
        simplified method (method 2) may be followed with little or no impact on the overall site score.
                                             173
                                                                                         Section 7.5

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                                     HIGHLIGHT 7-36
         ESTABLISHING TARGET DISTANCE CATEGORIES:  METHOD 2
  Well
  W, - Population =  750
  W2 - Population = 1000
  W3 - Population = 3000
  W4 - Population = 1500
Nearest Well Value = 9

Potential Contamination Factor
Value = 72
                                                                                0 to 1/4

                                                                                > 1/4 to 1/2

                                                                                > 1/2 to 1

                                                                                >1to2

                                                                                >2to3
                                                                                >3to4
(Well 1,  > 1/2 to 1 mile from
Source 2)

(>1/2to 1 mile = 750
>1 to 2 miles  = 1500
>2 to 3 miles  = 3000
>3 to 4 miles  = 1000)
         Measure the nearest well distance from the nearest source.

         Determine which well or wells may give the most representative score for the site based on distances
         to wells from each source and populations served by each well.

         Draw distance categories around only those sources significantly affecting the potential contamination
         factor.

         In this example, the nearest well is calculated from Source 2 and the population subject to potentiaf
         contamination could be calculated from Sources 2 and 4 because  Sources 1  and 3 would not
         contribute significantly to the total population score (compare with Highlight 7-35).

         This method may simplify scoring efforts at sites with many sources or dense populations, with little
         or no impact on the overall  score.  However, in some instances, ft may underestimate the ground
         water population factor value.
Section 7.5
                                              174

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TIPS AND REMINDERS

       Determine if individuals are within the TDL by the location of their well, not the location of their
       residence, school, or workplace.

       If a maximum score for the ground water pathway can be reached by evaluating only municipal
       wells, it may not be necessary to include the population served by private wells in the scoring. If
       people in the area use private wells, note this fact in the documentation record. One exception is
       that any well subject to Level I concentrations should be evaluated.

       Remember that the distance-weighted population values for potential contamination are
       assigned based on population ranges.  Documenting a few private wells subject to potential
       contamination will result in a different population factor value only if the original population
       estimate was at the higher end of the range.

       The nearest well factor may have a  significant effect on pathway score; therefore, evaluate this
       factor as accurately as possible. The nearest well factor can be scored based only on drinking
       water wells.

       Include the population using wells that were closed because of site-related actual contamination
       in estimates of the ground water population. This population should reflect the number of people
       using the well at the time it was closed.

       If a drinking water system being evaluated includes portions of more than one county and the
       specific number of residences supplied in each county is known, use county-specific estimates of
       persons-per-residence. Otherwise, use the lowest persons-per-residence figure to estimate the
       entire population served.

       An  individual may be counted as a resident and as a student or worker. If an individual  lives and
       attends school at locations served by drinking water wells within the TDL, count that individual as
       a resident and as a student.

       Well logs obtained from  local drillers are a good data source for determining in which aquifer(s)
       private wells are completed. In areas with a large number of private wells, one way of
       documenting how many wells are completed in each of two aquifers is to obtain a representative
       sample of well logs and assume the same ratio for all private wells in the area.
                                             1 75                                      Section 7.5

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SECTION  7.6
BLENDED WATER
SUPPLIES
       The population factor for the ground water pathway is evaluated based on level of contamination
(i.e., Level I, Level II, and potential contamination) and on the locations of the ground water wells that
supply people with drinking water. In some instances, discrete populations can be linked directly to
individual water wells. In other cases, water from multiple wells and/or surface water intakes is blended
prior to or during distribution to a target population. This section provides guidance on evaluating the
population factor in the ground water pathway when water from multiple wells, or wells and surface water
intakes, is blended prior to or during distribution.

       In general, the MRS provides for dividing a  target population among all the water supplies that
contribute to a blended distribution system in either of the following two ways:

       If no supply unit contributes more than 40 percent (based on average annual pumpage or
       capacity) of the total supply, divide population equally among all the units.

       If any one supply unit provides more than 40 percent, estimate the percentage contribution of
       each unit and assign each a percentage of the population based on its relative contribution.
                              RELEVANT MRS SECTION

        Section 3.3.2            Population
DEFINITIONS
       Blended Water Distribution System: A drinking water supply system that can or does combine
       (e.g., via connecting valves) water from more than one well or surface water intake, or from a
       combination of wells and intakes.

       Capacity: The amount of water a well or intake can deliver to a water distribution system.
       Capacity may be expressed in units that are equivalent to a pumpage rate or as a percentage of
       the system's requirements.

       Pumpage Data: A measure of the volume of water per unit of time discharged from a well, or
       collected within an intake, either by pumping or free flow. Well pumpage is commonly measured
       in gallons per minute (gpm), cubic      meters per day (m3/day; 1 gpm = 5.45 M3/day), or cubic
       feet per second (cfs; 1 gpm = 0.0023  cfs). Pumpage data may also be termed well  production
       data, well discharge data, well flow data, well yield data, pumping line data, and for intakes,
       intake pipe flow data. For MRS purposes, pumpage data relate to the measured or estimated rate
       of water withdrawal from a well or intake, not from a storage tank or reservoir used as a
       receptor for water drawn from one or  more wells and/or intakes. See High light 7-37 for more
       information on pumpage data.


                                           1 77                                    Section 7.6

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                                       HIGHLIGHT 7-37
                             PUMPAGE AND CAPACITY DATA

 A water authority may provide data on the contribution of each well or intake to the total blended water system In
 several forms, including pumpage, capacity, or specific capacity. All data used to apportion population must be of
 the same type (e.g., do not use capacity data for some wells or intakes and pumpage data for others) and in the
 same units. An abbreviated conversion table is provided below.
1 gal/min
1 ft 3/sec
1 m 3/day
= 0.00223 ft3/sec
= 448.8 gal min
= 4.09X10-4ft3/sec
= 5.45 m3/day
= 2,447 m3/day
= 0.183 gal/min
 Pumpage. Many water authorities keep pumpage records expressed as the total quantity of water pumped in a given
 interval, usually a day, a month, or a year, not in terms of pumpage for the period during which a well is used.
 Metered pumpage data are the most reliable. However, estimates of pumpage calculated by the water authority
 based on engineering parameters built into the well or intake design, construction, and pump configuration may also
 be acceptable.

 Capacity. The sum of the capacities may represent more than the total needs of the system. The relative capacity
 of each component, however, may be calculated by dividing the capacity of the component by the sum of the
 capacities of all the components. This normalization procedure means that the sum of the relative capacities of all
 the components in the system will total 100 percent.

 Specific Capacity. Because it is difficult to derive an equivalent term for surface water intakes, specific capacity data
 should only be used when the blended water system is supplied exclusively by ground water wells and when the
 specific capacity data are available for all wells In the system. If necessary, convert the specific capacity data for
 multiple wells to uniform units, then calculate the percentage contribution of each well to  the blended system.

 Standby Wells. When using pumpage data for a standby ground water well, use average pumpage for the period
 during which the standby well is used rather than average annual pumpage (MRS section 3.3.2). See Section 7.7
 for additional information.
       Specific Capacity: An alternative term to capacity that is associated with acceptance testing of
       ground water wells. Specific capacity is reported as the rate at which water is discharged from a
       well per unit drawdown in the aquifer in which the well is completed. This is usually expressed in
       gallons per minute per foot of drawdown (gpm/ft) or cubic meters per day per meter of drawdown
       (m3/d/m). The latter term may appear in the technical literature as nf/d.

       Standby Well: A well held  in reserve by a water supply entity (e.g., agency, authority,
       cooperative, private company, or individual) and maintained for use. It is designated as a
       drinking water supply well for use during a water supply shortage or emergency such as pump
       failure, drought, sudden water quality deterioration, or interruption in the regular supply.
       Additional terms commonly used to signify standby wells include reserve wells, drought wells,
       safety wells, emergency wells, backup wells, substitute wells, and uncommitted wells.

SCORING THE POPULATION FACTOR FOR BLENDED WATER SUPPLIES

       The steps below outline the procedure for evaluating the population factor for blended water
supplies, Highlight 7-38 summarizes the data needed.
Section 7.6                                      1 78

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                                       HIGHLIGHT 7-38
                  DATA NEEDFOR EVALUATING BLENDED SYSTEMS

 The typical data needed to evaluate the population factor when blended water systems are involved can include
 all of the following:

         Identification of all the water supply entities potentially affected by site activities

         Number and location of water supply units (i.e., ground water wells, surface water intakes,
         standby/emergency supplies).

         Well completion data for those wells identified as water supply units.

         —      Aquifer used
         —      Screened interval
         —      Water use
         —      Well owner

         Specifics of the water distribution system

         —      Geographic extent
         —      Number and types of connections (residential, industrial, commercial)

         Pumpage and/or capacity data for wells and intakes expressed in comparable units.

 Much of the information required to evaluate blended water systems can be collected directly from the water supply
 entities or local regulatory authorities. Inaddition, because some of the required information relates specifically to
 water resources studies, the  district office of the Water Resources Division of the U.S. Geological Survey and its
 state counterpart should be contacted as necessary. These governmental units can provide more detailed well and
 flow data through such publications as their Water Resources Investigation series, the Hydrologic Atlas series, anc
 annual  reports on specific river basins.
(1)     Identify all blended water supply systems that may have wells within the TDL. If there is
       more than one blended system, repeat the following steps for each system. If a blended
       system supplies water to another blended system or receives water from another blended
       system, refer to the subsection below, Scoring Multiple Blended Systems.

(2)     Identify all water supply units for the blended system. The units may include ground water
       wells, surface water intakes, and standby/emergency supplies. Obtain this information from the
       water supply entity and mark the location of each supply unit on a topographic map. Information
       on surface water intakes and wells that are not within the TDL or not in the aquifer being
       evaluated is needed to correctly apportion the population served.

(3)     Determine which wells to evaluate as targets for the population factor.

               Include as targets only wells that are within the TDL. Remember that any well subject to
               actual contamination is evaluated regardless of its distance from sources.

               Include as targets only wells that are completed in the aquifer being evaluated (or an
               overlying aquifer).

               If the blended system includes standby wells, see Section 7.7 for more detailed guidance
               on evaluating standby wells. Include or exclude some, all, or none of the standby well(s)
               to obtain the highest population factor. Exclude all  standby surface water intakes.
                                               1 79                                      Section 7.6

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(4)     Determine the total number of persons served by the blended system. Obtain this
       information from the water supply entity. If the data are provided in terms of service
       connections rather than persons served, multiply the number of service connections by the
       average number of persons per residence for the county. For more details on this evaluation,
       see Section 7.5.

(5)     Determine whether any single well or intake supplies more than 40 percent of the
       system's water. Obtain this information from the water supply entity, if possible.

(6)     Apportion the population in the blended system as follows:

              If no single well or intake supplies more than 40 percent of the system's water, apportion
              the population equally to all wells and intakes in the system (i.e., divide the total
              population by the number of wells and intakes).

              If a single well or intake supplies more than 40 percent of the system's water,  apportion
              population to each well or intake based on the percentage of water it supplies. Use
              average annual pumpage or capacity (see High light 7-39) to determine the percentage
              of water each well or intake supplies.

(7)     Tabulate the population assigned to target wells for the aquifer being evaluated  by:

              Actual (Level I or II) or potential contamination
              Karst and non-karst (for wells subject only to potential contamination)
              Target distance categories (for wells subject only to  potential contamination).

Highlights 7-39 and 7-40 illustrate scoring the population factor for blended  systems.

SCORING MULTIPLE BLENDED SYSTEMS

       Some blended water systems receive water from (or supply water to) another blended water
system via one or more water mains. The steps below describe how to apportion  population to each
supply well or intake in such cases. The blended system that supplies water is referred to as System S;
the blended system that receives water is referred to as System R.  Note that if two or more blended
systems provide water to each other, evaluate both as just one combined blended system; do  not use the
steps below.

APPORTION POPULATION SERVED BY RECEIVING SYSTEM (SYSTEM R)

(1)     Determine population served by System R. This step is identical to that for a normal
       blended system. Do not include the population served by the supplying system in the total.

(2)     Identify all water supply units for System R. The units are wells in System R, surface water
       intakes in System R, and water mains from the supplying system. Treat each water main in the
       same manner as one well or intake.

(3)     Determine whether any single System R water supply unit provides more than 40 percent
       of System R's total water. Note that the mains from System S are considered in this
       determination.

(4)     Apportion the population in System R as follows:

              If no water supply unit supplies more than 40 percent of the system's water, apportion
              the population equally to each water supply unit in System R.
Section 7.6                                     1 80

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                                    HIGHLIGHT 7-39
           SCORING EXAMPLE OF SINGLE BLENDED SYSTEM WITH WELLS
                        OUTSIDE THE TARGET DISTANCE LIMIT
Site Setting:

Water Supply:
Location of
Water Supply
Population
Served:
Evaluation:
A mixed-use suburban community.

Single  ground water authority with one water treatment plant.  Seven wells (all
completed in the aquifer being evaluated) supply water to the treatment plant prior to
distribution.
     One well between 1/2 and 1 mile of the site
     One well between 2 and 3 miles of the site
     Two wells between 3 and 4 miles of the site
     Three wells in a well field 5 miles from the site

The water authority reports 100,000 residential connections.
The population density in the county in which the site is located is 2.5 persons per
residence. Assuming all residential connections:

Population served = 100,000 x 2.5 = 250,000 people

No Level I  or Level  II contamination is identified. Evaluate population  based on
potential contamination. The water authority reports no well contributes more than 40
percent to the system. Therefore, assign 35,714.3 people (250,000/7) to each well in
the system (do not round at this  point).

Distance-weighted population values (non-karst) are:

     Between 1/2 and 1 mile (one well: 35,714 people)	  16,684
     Between 2 and 3 miles (one well: 35,714 people)	  6,778
     Between 3 and 4 miles (two wells: 71,428 people)	  4,171
     Beyond 4 miles (three wells: 107,143 people)	N/A

Total distance-weighted population value	  27,633

Potential contamination factor value = 1/10 x 27,633 = 2,763

Population factor value = 2,763
                                           181
                                                                                   Section 7.6

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                                     HIGHLIGHT 7-40
             SCORING EXAMPLE FOR TWO SEPARATE BLENDED SYSTEMS
 Site Setting:

 Water Supply:
A densely populated urban center.

Two water authorities (Systems A and B) with separate water treatment plants and
separate distribution systems. All wells are completed In the aquifer being evaluated.

       System A is supplied by four ground water wells.
       System B is supplied by five ground water wells.
 Location of
 Water Supplies:  System A:
                         One well between 1 and 2 miles of the site
                         One well between 2 and 3 miles of the site
                         Two wells between 3 and 4 miles of the site

                  System B:
 Population
 Served:
 Evaluation:
       Two wells between 3 and 4 miles of the site
       Three wells more than 4 miles from the site

The population density inthe county served by the water systems is 2.5 persons per
residence.

Water Authority A reports 80,000 residential connections.

       Population served by System A = 80,000 x 2.5 = 200,000 people

Water Authority B reports 20,000 residential connections.

       Population served by System B = 20,000 x 2.5 = 50,000 people

No Level I  or Level II contamination is  identified. Evaluate population  based on
potential contamination. Both water authorities report no wells contributing more than
40% of their total needs.

Assign 50,000 people (200,000/4) to each System A well.

Assign 10,000 people (50,000/5) to each  System B well.

The distance-weighted population values (non-karst) are:

       Between  1 and 2 miles (System A - 50,000)	  9,385
       Between  2 and 3 miles (System A - 50,000)  	  6,778
       Between  3 and 4 miles (System A-100,000; System B-20,000)  .  13,060
       Beyond 4 miles (System B - 30,000)  	  N/A

Total distance-weighted population value  	  29,223

Potential contamination factor value = 1/10 x 29,223 = 2,922

Population factor value = 2,922
Section 7.6
                                            182

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              If a water supply unit supplies more than 40 percent of the system's water, apportion
              population to each water supply unit based on the percentage of water it supplies Use
              average annual pumpage or capacity to determine the percentage of water supplied by
              each well, intake, or main.

(5)     Apportion the population to the wells and intakes in System R, plus the mains from
       System S. Then, for System  R determine which wells are within the TDL. Tabulate only the
       populatiop served by System R wells. Do not include the population apportioned to mains from
       System S. In some cases, no System R wells will be within the TDL for the aquifer being
       evaluated. Even in these cases, population must be apportioned so that System S can be
       evaluated. As with all blended systems, the population is tabulated by level of contamination
       and, for wells subject to potential contamination, by karst/otherthan karst and target distance
       category.

APPORTION POPULATION SERVED BY THE SUPPLYING SYSTEM  (SYSTEM  S)

(1)     Determine the total population served by System S. This population includes all people
       served by System S plus some  of the people served by System R.

              Refer to Step (4) above for the number of people served by System R that were
              apportioned to each System S water main.

              Add this number to the population served directly by System S to calculate the total
              population served by System S.

       After calculating the total population served by System S, ignore the water mains for the rest of
       these steps.

(2)     Identify all water supply units for System S. The water supply units are ground water wells
       in System S and surface water intakes in System S. The water mains to System R are not
       water supply units for System S.

(3)     Determine whether any single System S well or intake supplies more than 40 percent of
       System S's water.

(4)     Apportion the population in System S as follows:

              If  no well or intake supplies more than 40 percent of the system's water, apportion the
              population equally to all wells and intakes in System S.

              If a well or intake supplies more than  40 percent of the system's water, apportion
              population to each well or intake based on the percentage of water it supplies Use
              average annual pumpage or capacity to determine the percentage of water each  well or
              intake supplies.

(5)     Include the population apportioned to any System S well within the TDL in the tabulation
       of population served for the aquifer being evaluated. As with all blended  systems, the
       population is tabulated by level of contamination and, for wells subject to potential
       contamination, by karst/non-karst and target distance category.

An example of apportioning population to two blended systems in which one is supplying water to the
other is provided in Highlight 7-41.
                                            1 83                                    Section 7.6

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                                      HIGHLIGHT 7-41
                  SCORING EXAMPLE FOR MULTIPLE BLENDED SYSTEMS
 Water Supply: System R:
 Location of
 Wells:
 Population
 Served:
 Population
 Factor:
              System S:


              System R:


              System S:
              System R:
              System S:
Blends water from four wells and receives water from System S via 2
water mains; no single well or main provides >40% of the system's
water.

Blends water from eight wells; no well provides >40% of the system's
water.

2 wells > 1-2 miles from the site
2 wells > 2-3 miles from the site

2 wells > 3-4 miles from the site
Other 6 wells outside TDL

30,000 people
20,000 people
 Evaluation:   Apportion population served by receiving system - System R

               Number of water supply units = 4 wells + 2 mains = 6 units
               People/unit = 30,000/6 = 5,000

               Assign 5,000 people to each System R well and to each water main from System S.a

               Apportion population served by supplying system - System S

               Total Population  =   20,000 (population served by System S) + 10,000 (population
                                    apportioned to the two water mains supplying system  R)  =
                                    30,000
               Number of water supply units = 8 wells
               People/unit = 30,000/8 = 3,750
              Assign 3,750 people to each System S well?

              The distance-weighted population values (non-karst) are:

                     Between 1-2 miles (2 System R wells = 10,000 people)	939
                     Between 2-3 miles (2 System R wells = 10,000 people)	678
                     Between 3-4 miles (2 System S wells = 7,500 people)	417

              Total distance-weighted population  value	  2,034

              Potential contamination factor value = 1/10 x 2,034 = 203

       a Note that the total number of individuals allocated to wells is 50,000 (i.e., 5,000 for each System
R well and 3,750 for each System S well). Although the total allocated is the same total as the population
served (i.e., 20,000 plus 30,000), the population assigned to systems wells is greater than that served
by System S (i.e., 30,000 versus 20,000) while the population allocated to System R wells Is less than that
served by System R (i.e., 20,000 versus 30,000).
Section 7.6
                                            184

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TIPS AND REMINDERS

       If no single well or intake supplies more than 40 percent to the total blended system, apportion
       the population equally to all wells and intakes even if more definitive information is available.
       Equal apportionment simplifies the scoring process and provides a nationally consistent
       approach.

       Allocate population served to each well or intake in the blended system, but only include in the
       evaluation of the aquifer those populations that are allocated to wells located within the TDL.

       When two or more blended systems provide water to each other, evaluate both as one combined
       blended system.

       If some wells in a blended system are subject to actual contamination and some to potential
       contamination, first use the rule for apportioning population for a blended system to assign a
       population to each well. Then score the population assigned to each well based on whether Level
       I, Level II, or potential contamination applies to that well.
                                             1 85                                     Section 7.6

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SECTION 7.7
STANDBY WELLS
       This section defines standby wells and associated terms, provides guidance regarding the use of
standby wells to evaluate certain targets factors in the ground water pathway, and explains how to
apportion population to standby wells. If a standby well located within the TDL draws water from the
aquifer being evaluated or from any overlying aquifer, the well may be used to evaluate both the nearest
well and population factors. To designate a standby well as the nearest well, MRS section 3.3.1 states
that it must be "used for drinking water supply at least once every year." A standby well can be used to
evaluate the population factor when it is "maintained on a regular basis so that water can be withdrawn"
(MRS section 3.3.2). Standby wells are  not considered in the evaluation  of the resources factor.
Highlight 7-42 summarizes the use of standby wells in evaluating targets.
                              RELEVANT MRS SECTIONS
        Section 3.3.1             Nearestwell
        Section 3.3.2             Population
DEFINITIONS
       Annual Use: Criterion for determining whether a standby well may be used to evaluate the
       nearest well factor. To meet this criterion, a standby well generally should supply drinking water
       for at least one 24-hour period in a year.

       Pumpage Data: A measure of the volume of water per unit of time discharged from a well, or
       collected within an intake, either by pumping or free flow. Well pumpage is commonly measured
       in gallons per minute (gpm), cubic meters per day (nf/day; 1  gpm = 5.45 m3/day), or cubic feet
       per second (cfs; 1 gpm = 0.0023 cfs). Pumpage data may also be termed well production data,
       well discharge data, well flow data, well yield data, pumping line data, and for intakes, intake
       pipe flow data. For MRS purposes, pumpage data relate to the measured or estimated rate of
       water withdrawal from a well or intake, not from a storage tank or reservoir used as a receptor
       for water drawn from one or more wells and/or intakes.

       Regular Maintenance: The routine inspection, cleaning, and testing of a well so that it can be
       ready for immediate use. This is a criterion for determining whether a standby well may be used
       to evaluate the population factor. Regular maintenance of a standby well may include direct
       measurement of the static water level,  inspection of the well and pump, and testing of the pump.
       Such activities generally should be conducted at least once a year, and the operating authority
       should consider the  well functional. Rehabilitation activities, with the  intent of retaining a standby
       well in a state of readiness, also can be considered regular maintenance. Such activities include
       pump cleaning and lubrication, screen and gravel pack cleaning, and treatment for encrustation
       and/or biofouling.

       Specific Capacity: An alternative term to capacity that is associated with acceptance testing of
       ground water wells.  Specific capacity is reported as the rate at which water is discharged

                                           187                                   Section 7.7

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                                     HIGHLIGHT 7-42
 DATA NEEDS AND SOURCES FOR STANDBY WELLS

        Considerboth the definition of standby well and the aquifer in which it is completed in identifying
        eligible standby wells.

        Document annual use when evaluating the nearest well factor.

        Document regular maintenance when evaluating the population factor.

        Do not consider when evaluating resources.

        Contact water supply entities (or  regulatory authorities) directly to obtain the following data
        needed to evaluate standby wells:

        —     Ensure that the well is one that is held in reserve to be used during a  water supply
               emergency.

        —     Confirm that the well is regularly maintained.

        —     Obtain well logs or completion records that link the standby well to either the aquifer
               being evaluated or an overlying aquifer.

        —     Additional information (e.g.,  pumpage  or  capacity  data)  may  be required  when
               apportioning populations to standby wells and then using the standby well to evaluate the
               population factor (See Section 7.7).
       from a well per unit drawdown in the aquifer in which the well is completed. This is usually
       expressed in gallons per minute per foot of drawdown  (gpm/ft) or cubic meters per day per meter
       of drawdown (nf/d/m). The latter term may appear in the technical literature as nf /d.

       Standby Well: A well held in reserve by a water supply entity (e.g., agency, authority,
       cooperative, private company, or individual) and maintained for use. It is designated as a
       drinking water supply well for use during a water supply shortage or emergency such as pump
       failure, drought, sudden water quality deterioration, or interruption in the regular supply.
       Additional terms commonly used to signify standby wells include reserve wells, drought wells,
       safety wells, emergency wells, backup wells, substitute wells, and uncommitted wells.

       Wellfield Rotation Program: Program in which wells within a water supply system are  used only
       for specified intervals, Generally, a pattern is repeated until every supply well has been used,
       and then the entire cycle is repeated. Rotation programs are designed to minimize drawdown
       interference and to maximize efficient use of water in relation to varying water demand. Do not
       consider a well that is part of a planned wellfield rotation program a standby well.

SCORING THE NEAREST WELL FACTOR USING STANDBY WELLS

       Follow the general steps given below to evaluate the nearest well factor based  on a standby well.

(1)     Identify target standby wells. The well must meet the definition of standby well and be within
       the TDL for the aquifer being evaluated. If the standby well is subject to actual contamination,
       it can be evaluated regardless of its distance from sources.
Section 7.7                                     188

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(2)     Determine whether a target standby well is eligible to be used to score the nearest well
       factor. The standby well can be used to score the nearest well factor if:

              It is used to supply drinking water.

              It has been used annually (as defined above). It is not necessary to document that the
              well has been used annually for the entire time it has been designated as a standby well.
              Documenting recent annual use (e.g., for the past five years) generally is sufficient. If
              the well was brought into a state of readiness only within the past few years, annual use
              since that time should be documented.

(3)     Use the eligible standby well as the nearest well if it results in a higher factor value score
       than any regular well. This could occur if the standby well is subject to actual contamination
       and the regular wells are not, or if the standby well is closer to the sources at a site (or possibly if
       the standby well is in a karst aquifer and the regular wells are not).

SCORING THE POPULATION FACTOR USING STANDBY WELLS

(1)     Identify target standby wells. The well must meet the definition of standby well and be within
       the TDL for the aquifer being evaluated. If the standby well is subject to actual contamination,
       it can be evaluated regardless of its distance from sources.

(2)     Determine whether a target standby well is eligible to be used to score the population
       factor. The standby well can be used to score the population factor if it:

              Is used to supply drinking water
              Has been regularly maintained (as defined above)

(3)     Calculate the population factor with and without the standby well.

              If there is more than one eligible standby well, calculate the population factor value for
              various combinations of wells. Each  combination must include:

              —     AN  regular wells (and regular surface water intakes)
              —     Some, all, or none of the standby wells (standby switches are not included)
              —     None  of the standby surface water intakes

              Do  not assign the same population to both a standby well and a regular well or surface
              water intake.

              Use the average pumpage (e.g., gallons per minute) for the period during which the
              standby well is used (i.e., do not attempt to annualize pumpage data for standby wells as
              done for regular wells). If these data are not available, use capacity for all wells to
              calculate the population factor. Highlight 7-43 provides additional information on
              pumpage and capacity data for standby wells.

(5)     Choose the combination of regular and standby wells that results  in the highest
       population factor value for the aquifer being evaluated.

       Highlight 7-44 provides an example of calculating average pumpage for a standby well.
Highlight 7-45 provides an example of scoring the population factor using a standby well.
                                             189                                     Section 7.7

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                                       HIGHLIGHT 7-43
               PUMPAGE AND CAPACITY DATA FOR STANDBY WELLS

 If no well or intake provides more than 40 percent of the total water supply for the system, simply apportion the
 population equally among the wells and/or intakes. However, if one well or intake does provide more than 40 percent
 of the total water supply, apportion the population according to each well's or intake's relative contribution to the total
 blended system. Consider the following points when apportioning population in a system with standby wells where
 one water source provides more than 40 percent of the total supply.

 (8)      Use either capacity or pumpage data to calculate the percentage of the population to be assigned to each
         component of the system. Do not use pumpage data for one component and  capacity data for other
         components.  Data from standby wells and regular supply wells must be in the same units.

 (9)      When using pumpage data for a standby well,  use average pumpage for the period during which the
         standby well is used rather thanaverage annual  pumpage. The period during which a standby well Is on
         line but not actually pumping should not be considered part of the period during which the standby well is
         used.

 (10)     Often, pumpage data for standby wells are not based on water flow meter readings, but reflect estimates
         based on pumping test data, pump size, orifice of effluent pipe, or duration of pumping. Use metered
         pumpage data whenever possible; alternatively,  estimate pumpage based on these or other appropriate
         parameters.

 (11)     If possible, attempt to calculate an average over the most recent periods of use. However, calculation of
         the pumpage rate for a standby well can be based on a period of use several years ago.
                                       HIGHLIGHT 7-44
                     USING PUMPAGE DATA FOR STANDBY WELLS


 Standby Well
 Use:                   Used for 28 days in a year.

                        60,480,000 gallons are pumped during the 28 days.

 Calculation of
 Pumpage:              For evaluation purposes, calculate the pumpage rate for the standby well as follows:

                                   60,480,000 gallons         = 1,500 gpm
                               (28 day) (24 hr/day)(60 min/hr)


 Apportionment:         Water from this standby well is blendedwith water from three regular supply wells with
                        pumpage rates of 2,000, 1,000, and 4,000 gpm. The largest contribution of any well is:

                               	4,000	  = 0.47 = 47%
                               1,500 + 2,000+ 1,000 + 4,000


                        Therefore,  apportion population to the four wells based on each well's  relative
                        contribution. Note that if the standby well was not considered, the largest contribution
                        would be 57 percent and apportionment to the three regular supply wells would still be
                        based on relative contribution.
Section 7.7                                        190

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                                       HIGHLIGHT 7-45
          EVALUATING POPULATION FACTOR USING A STANDBY WELL

Site Setting:     Rural location with low population density.

Water Supply:  Local water authority blendswater from one surface water intake (pumping 450 gpm), and one
               well (pumping 550 gpm).

               Another ground water well (capable of pumping at a rate of 550 gpm) is regularly maintained to
               serve as an emergency supply.

Location of
Water Supply:  Intake is located on a  stream within 1/2 mile of PPE for the site.

               Regular well is between 1/2 and 1 mile of the site.

               Emergency well is between 1 and 2 miles of the site.

Population
Served:        1,000 residential connections.

               Population density in the county is 2.4 persons per residence.

               Total  population served = 1,000 x 2.4 = 2,400

Evaluation:     No Level I or Level II contamination is identified. Evaluate population served on the basis of
               potential contamination. Water authority reports that the standby well can provide enough water
               during any interruption in  either the surface water or regular ground water supply.

Alternative 1:   Include the standby well in apportioning population to the blended system.

               The largest relative contribution by any well  or intake is:

                      	55O	   =  35.5%
                      (55O  -t- 450 +  550)

               Because none of the water supply units provides more than 40 percent of the total, assign one-
               third of the total population (800 people) to each well or intake.

               The distance-weighted population values  (non-karst) are:

                       Between 1/2  and 1 mile (800 people)  	  167
                       Between 1 and 2 miles (800 people)	 94

               Total  distance-weighted population value	  261

               Potential contamination factor value = 1/10 x 261 = 26

               Do not evaluate the 800 people assigned to the surface water intake in the ground water pathway;
               they would be evaluated in the surface water pathway. In evaluating the surface water pathway,
               the standby well would not be included.

                                             (continued on next page)
                                               191                                        Section 7.7

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                               HIGHLIGHT 7-45 (continued)
          EVALUATING POPULATION FACTOR USING A STANDBY WELL
 Alternative 2:
 Selected
 Alternative:
Exclude the standby well in apportioning the population to the blended system.

The largest relative contribution to the blended system is provided by the ground water well:

       5507(550 + 450) = 55%

Therefore, assign the total population to the two water units based on their relative percentage
contribution:

       Well   = (2,400)(0.55) = 1,320 people
       Intake  = (2,400)(0.45) = 1,080 people


The distance-weighted population values (non-karst) are:

       Between 1/2 and 1 mile (1,320 people)  	  523

Total distance-weighted population value	  523

Potential contamination factor value = 1/10 x 523 = 52

NOTE:  The 1,080 people assigned to surface water intake are not evaluated for the ground
       water pathway.
Because Alternative 2 results in a higher potential contamination factor value, use it to
evaluate the aquifer.
TIPS AND REMINDERS


(12)   The annual use criterion applies only to the nearest well factor evaluation. A standby well can be
       used to evaluate the population factor without meeting the annual use criterion, providing it is
       regularly maintained so that water can be withdrawn.

(13)    Standby wells need not be evaluated; if they are, evaluate only those that raise the score. The
       apportioning of population using standby wells may differ for each aquifer evaluated (i.e., it is not
       necessary to consider an eligible standby well for one aquifer simply because it is considered for
       a different aquifer). Do not assign the same population to both a standby well and a regular well
       or intake when apportioning drinking water population,

(14)    Do not include standby surface water intakes when scoring the ground water pathway.

(15)    Wells that are part of a planned wellfield rotation program are not considered standby wells.

(16)    Any standby well used to determine relative contributions for a blended system should also be
       used in the apportionment of population.

(17)    Use average pumpage for the period of use, rather than average annual pumpage, when
       evaluating standby wells.
Section 7.7
                                             192

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SECTION 7.8
RESOURCES AND
WELLHEAD  PROTECTION
AREA
       This section provides guidance on scoring the resources and wellhead protection area (WPA)
factors for the targets factor category of the ground water pathway. The resources factor (MRS section
3.3.3) evaluates the possible loss of ground water use value resulting from site-related contamination. It
does not evaluate threats to human health that are considered in the nearest well and population factors.
The wellhead protection area factor (MRS section 3.3.4) evaluates the  possibility that a source or
observed release lies in or near an area that a state has designated for protection under the SDWA.
                           RELEVANT MRS SECTIONS
        Section 3.3.3          Resources
        Section 3.3.4          Wellhead protection area
DEFINITIONS
       Commercial Aquaculture: Cultivation offish or shellfish to be sold for widespread distribution.
       Examples include a rearing pond used to raise catfish or a pond for nonfood crops such as
       goldfish and tropical fish.

       Commercial Food Crops: Crops that are intended to be sold widely, such as in supermarkets,
       and locally, such as those sold at local produce stands. Crops grown for domestic consumption
       or for use in a single restaurant are not considered commercial food crops.

       Commercial Forage Crops: Crops grown to be sold as food for livestock (it is not necessary to
       document that these crops were sold only for commercial livestock), and grasslands used for
       grazing by commercial livestock (including areas technically defined as "pasture/rangeland" by
       the USDA).

       Ingredient In Commercial Food Preparation: Ground water used for wholesale food
       preparation (e.g., a manufacturer that prepares food products to be sold in supermarkets or
       produce stands). Food prepared in restaurants is not included in this category.

       Major or Designated Water Recreation Area: A major water recreation area is an area used by
       a large number of people for recreational purposes (e.g., a water theme park). A designated
       water recreation  area  is  an area designated and maintained by a government body (e.g., local,
       state, or Federal) as an area for public recreation (e.g., municipal swimming  pool).
                                         193                                  Section 7.8

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       Wellhead Protection Area (WPA): Area designated by states according to section 1428 of the
       SDWA, as amended, to protect wells and recharge areas that supply public drinking water
       systems.

SCORING THE RESOURCES FACTOR

(1)     Use the checklist In Highlight 7-46 to determine whether any uses that are assigned
       resource points apply to any target well for the aquifer being evaluated. Standby wells
       cannot be used to score the resources factor. Use the definitions above to assist in making this
       determination. Because the resources factor receives an "all or nothing" value, it may not be
       necessary to continue with the other questions on the  checklist after one resource use is
       identified. Note that the factor can be evaluated based on any target well in the aquifer being
       evaluated or in overlying aquifers. Highlight 7-47 provides sources of information that may help
       document resource use.

(2)     If a resource use can be documented, assign a value of 5 to the resources factor for the
       aquifer. If no resource use can be documented, assign a value of 0.

SCORING THE WELLHEAD  PROTECTION AREA  FACTOR

       WPAs are designated by state or local agencies; however, some states may not have any
designated WPAs. Contact the state department of environmental protection or equivalent agency to
determine the status of the state's WPA program and to obtain information on the location of WPAs.

(1)     Determine whether there is  a designated WPA within the TDL The WPA must be  applicable
       to the aquifer being evaluated or an overlying aquifer through which hazardous substances
       would  migrate to reach the  aquifer being evaluated.

              If not, assign a value  of 0 to the WPA factor
              If so, continue to Step (2).

(2)     Determine whether a source (with a ground water containment factor value greater than 0)
       lies either partially or fully above the designated WPA.

              If so, assign a value of 20 to the WPA factor
              If not, continue to Step (3).

(3)     Determine whether an observed release attributable to the sources at the site can  be
       documented within the designated WPA.

              If so, assign a value of 20 to the WPA factor
              If not, assign a value  of 5 to the WPA factor.
Section 7.8                                     194

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                                   HIGHLIGHT 7-46
                      CHECKLIST FOR RESOURCES FACTOR
For the aquifer being evaluated:

(1)      Is ground water used to irrigate five or more acres of commercial   Yes         No
        food crops or commercial forage crops?

(2)      Is grouped water used to water commercial livestock?            Yes         No


(3)      Is ground water used as an ingredient in commercial food         Yes         No
        preparation?

(4)      Is ground water used as a supply for commercial acquaculture?    Yes         No


(5)      Is ground water used as supply or a major or designated water     Yes         No
        recreation area, other than for drinking water use?

(6)      If there are no drinking water wells within the TDL is ground       Yes         No
        water usable for drinking purposes?

If the answer is "yes" for any of the above possibilities, assign a resources factor value of 5. Otherwise,
assign a resource factor value of 0.
                                   HIGHLIGHT 7-47
                  INFORMATION SOURCES OF RESOURCE USE

The following sources of information on possible ground water uses will help in documenting resource
use for an aquifer:

       Topographical maps
       Field observations
       Well service records
       Interviews with water company officials
       Existing PA/SI reports
       Correspondence with nearby businesses
       Correspondence with other nearby entities, such as farms or universities
       Files from adjacent or nearby CERLIS sites
       USGS hydrogeologic investigation reports
       USGS's Ground Water Site Inventory (GWSI) data base
       The National Water Well Association's WELLFAX data base
       Agricultural extension agents
       Local Chambers of Commerce
                                          195                                    Section 7.8

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TIPS AND REMINDERS

       A maximum of 5 targets points can be assigned for the resources factor. Do not spend a lot of
       time documenting resource use unless those 5 points may be critical to the site score.

       A well used for both drinking water and irrigation can be assigned targets points for the
       population, nearest well, and resources targets factors.

       Standby wells cannot be used to score the resources factor.

       Sole source aquifers do not qualify as WPAs unless they are so designated.

       Proposed WPAs should not be scored as WPAs; however, their proposed designation should be
       mentioned in the documentation record.  If the proposed WPA is designated as a WPA before the
       scoring package goes final, the site score can be adjusted.
Section 7.8                                     196

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SECTION 7.9
SCORING SITES WITH
MULTIPLE AQUIFERS
                                                           LR
       This section provides guidance on scoring the ground water pathway when multiple aquifers are
present. A ground water pathway score is calculated for each aquifer at the site, and the highest score is
selected as the ground water pathway score. When evaluating an aquifer, the MRS specifies that the
targets using water from that aquifer are included as well as targets using water from all overlying
aquifers through which hazardous substances would migrate to reach the aquifer being evaluated. This
section provides several examples of scoring multiple aquifer systems.
        Section 3.0
        Section 3.1.2
        Section 3.3
        Section 3.3.1
        Section 3.3.2
        Section 3.3.2.4
        Section 3.4
RELEVANT MRS SECTIONS

Ground water migration pathway
Potential to release
Targets
Nearest well
Population
Potential contamination
Ground water migration score for an aquifer
DEFINITIONS

       Multiple Aquifer System: A hydrogeologic situation consisting of two or more aquifers that are
       not interconnected and that underlie sources at the site.

SCORING MULTIPLE AQUIFER SYSTEMS

(1)     Determine waste characteristics factor category value. Calculate according to MRS section
       3.2. Generally the waste characteristics factor category value will be the same for all aquifers
       evaluated for the site. However, it is possible for the mobility factor value to vary by aquifers
       (e.g., if there is an observed release to one aquifer but not others).

(2)     Determine likelihood of release factor category value for each of the aquifers being
       evaluated.

              If an observed release to the aquifer being evaluated can be demonstrated based on
              direct observation or chemical analysis, assign that aquifer a likelihood of release factor
              value of 550.

              If an observed release cannot be documented, score potential to release according to
              MRS section 3.1.2. Because several of the components of potential to release (depth to
              aquifer and travel time) are aquifer-specific, the potential to release factor value may be
              different for each of the aquifers being evaluated.
                                          197
                                                                               Section 7.8

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(3)     Determine all targets for the shallowest aquifer being evaluated. Document all targets for
       the shallowest aquifer, including the population, nearest well, resources, and WPAs.

(4)     Determine all targets for each deeper aquifer that Is evaluated at the site. Identify all
       targets in the deeper aquifer, plus those in any overlying aquifer through which hazardous
       substances would migrate to reach  the aquifer being evaluated.

(5)     Calculate a separate ground water score for each aquifer.

(6)     Select the highest score from among the aquifers evaluated as the ground water pathway
       score for the site.

EXAMPLES OF MULTIPLE AQUIFER SYSTEMS

EXAMPLE 1: OVERLYING AQUIFERS EVALUATED UNDER POTENTIAL TO RELEASE (FIRST
SCENARIO)

       The site is located over two non-karst aquifers that are not interconnected. The shallower aquifer
is designated Aquifer A and the deeper one is designated Aquifer B. Aquifer A lies 20 feet below the
lowest known point of the hazardous substances at the site, and Aquifer B is approximately 85 feet below
that same lowest known point. The same sources overly Aquifers A and B, and waste characteristics
values are the same for both aquifers. The  lowest hydraulic conductivity layer in the interval between the
lowest known point of hazardous substances at the site and the top of Aquifer A is a 7-foot layer of silty
clays. For Aquifer B, the lowest hydraulic conductivity layer is a 15-foot layer of clay.

       Several private wells and one municipal well use Aquifer A, the nearest of which is 3/4 mile from
the source. The only well that uses Aquifer  B is 3.5 miles from the source, and serves a small trailer park
community. There is no observed release to either aquifer. For both aquifers, the waste characteristics
factor category value is 56, the containment factor value is 10, and the net precipitation factor value is 6.

Targets

       Nearest Well. For Aquifer A, the nearest drinking water well from any source at the site is 3/4
mile. Assign  it a nearest well factor value of 9 (from MRS Table 3-11). For Aquifer B, the nearest well
factor may be based on the shortest distance from any source to a well in Aquifer B or Aquifer A.
Because the nearest drinking water well in Aquifer B is 3.5 miles from the source, use the nearest well in
Aquifer A to score Aquifer B's nearest well factor. Assign Aquifer B a nearest well factor value of 9.

       Population. The following table presents the population served by drinking wells within  the TDL
for both aquifers. Because Aquifer A Is an overlying aquifer through which hazardous substances would
migrate to reach Aquifer B, the entire population evaluated in Aquifer A is included  in the evaluation of
Aquifer B.

       As specified in MRS section 3.3.2.4, multiply the total distance-weighted population by 1/10 to
determine the value for the potential  contamination factor. Therefore, the potential contamination factor
is 69 for Aquifer A and 74 for Aquifer B.

       Resources. No resource uses, as defined in MRS section 3.3.3, were documented for either
aquifer.

       Wellhead Protection Area. None were designated for either aquifer.
Section 7.9                                     198

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Distance
Category
(miles)


0 to 1/4
>1/4to1/2
>1/2to1
>1 to 2
>2to3
>3to4
Totals
Evaluation of Aquifer A


Wells

0
0
4
12
1
0
-


Population

0
0
16
48
5,000
0
5,064

Distance-
weighted
Population
0
0
5
10
678
0
693
Evaluation of Aquifer B
(Wells




Wells

0
0
4
12
1
1
-
in Overlying Aquifer A
Included)



Population

0
0
16
48
5,000
320
5,384



Distance-
weighted
Population
0
0
5
10
678
42
735
       Targets Factor Category Value. For each aquifer, this value is the sum of the four factors
detailed above (population, nearest well, resource, wellhead protection area). Therefore, the targets
factor category value is 78 for Aquifer A and 83 for Aquifer B.

Likelihood of Release

       There is not an observed release to either aquifer, so potential to release is evaluated separately
for each aquifer. Containment and net precipitation, two of the factor values used to determine potential
to release, are the same for both aquifers and are equal to 10 and 6, respectively.

       The other two factors, depth to aquifer and travel time, are different for Aquifers A and B.
Because Aquifer A is 20 feet from the lowest known point of hazardous substances and Aquifer B is 85
feet from that point, assign Aquifer A and Aquifer B depth to aquifer factor values of 5 and 3,
respectively. The geologic information provided indicates that Aquifer A should be assigned a travel time
factor value of 15  and Aquifer B a  value of 5 (see MRS Tables 3-6 and 3-7).

       Calculate  the likelihood of release factor category value by multiplying the containment factor
value by the sum of the travel time, depth to aquifer, and net precipitation factor values.  Based on this
formula, Aquifer A has a likelihood of release factor category value of 260 (i.e., 10[15+5+6]) and Aquifer
B has a likelihood of release category factor value of 140 (i.e., 10[5+3+6]).

Ground Water Pathway Score

       As defined in MRS section 3.4, calculate a ground water score for each aquifer by multiplying the
likelihood  of release, waste characteristics, and targets factor category values and dividing the product
by 82,500. The ground water score is 13.77 (i.e., [260 x 56 x 78]/82,500) for Aquifer A and 7.89 (i.e.,
[140 x56 x83]/82,500) for Aquifer B. Therefore, the score calculated for Aquifer A is used as the ground
water pathway score for the site.

       Although Aquifer B had a slightly higher targets value than Aquifer A, Aquifer B had a lower
overall ground water score. This is because for this site the extra targets in Aquifer B did not contribute
as much to the pathway score as the higher potential to release value (i.e., depth to aquifer and travel
time factors) in Aquifer A.
                                              199
                                                                                       Section 7.9

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EXAMPLE 2: OVERLYING AQUIFERS EVALUATED UNDER POTENTIAL TO RELEASE (SECOND
SCENARIO)

       The description of this site is the same as in Example 1, except that the drinking water well that
uses Aquifer B is a municipal well that serves 15,000 people. This well is 3.5 miles from the source.

Targets

       Nearest Well. The evaluation of the nearest well factor is performed as described in Example 1.
For both Aquifers A and B, the nearest well factor is assigned a value of 9.

       Population. The following table presents the population served  by drinking water wells within the
TDL for Aquifers A and B.


Distance
Category
(miles)


0 to 1/4
>1/4to1/2
>1/2to1
>1 to 2
>2to3
>3to4
Totals
Evaluation of Aquifer A




Wells Population

0
0
4
12
1
0
-

0
0
16
48
5,000
0
5,064

Distance-
weighted
Population
0
0
5
10
678
0
693
Evaluation of Aquifer B
(Wells



Wells

0
0
4
12
1
1
-
in Overlying Aquifer A
Included)


Population

0
0
16
48
5,000
15,000
20,064


Distance-
weighted
Population
0
0
5
10
678
1,306
1,999
       As specified in MRS section 3.3.2.4, multiply the total distance-weighted population by 1 /10 to
determine the value for the potential contamination factor. Therefore, the potential contamination
factor is 69 for Aquifer A and 200 for Aquifer B.
       Resources. No resource uses, as defined in MRS section 3.3.3, were documented for either
aquifer.

       Wellhead Protection Area. None were designated for either aquifer.

       Targets Factor Category Value. For each aquifer, this value is the sum of the four factors
detailed above (population, nearest well, resource, wellhead protection area). Therefore, the targets
factor category value is 78 for Aquifer A and 209 for Aquifer B.

Likelihood of Release

       The likelihood of release factor category values for Aquifers A and B are the same as in
Example 1 - 260 for Aquifer A and 140 for Aquifer B.
Section 7.9
                                            200

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Ground Water Pathway Score

       As defined in the MRS section 3.4, a ground water score for each aquifer is calculated by
multiplying the likelihood of release, waste characteristics, and targets factor category values and
dividing the product by 82,500. The ground water score is 13.77 (i.e., [260 x56 x78]/82,500) for Aquifer
A and 19.86 (i.e., [140 x56 x209]/82,500) for Aquifer B. Therefore, the score for Aquifer B is used as the
ground water pathway score for the site.

        In this example, the significantly larger targets value for Aquifer B compared with Aquifer A
offsets the fact that Aquifer B has a lower likelihood of release value than Aquifer A.

EXAMPLE 3: ONE AQUIFER EVALUATED UNDER OBSERVED RELEASE AND ONE UNDER
POTENTIAL TO RELEASE

       Aquifer A lies above Aquifer B. An observed release by chemical analysis has been established
to Aquifer A. One well, located 0.7  miles from the source, draws from Aquifer A, and  it serves a family of
five. Level I concentrations have been documented. There is no observed release to Aquifer B.
Approximately 2.8 miles from the source, a municipal well serving 12,000 individuals uses Aquifer B.
The waste characteristics factor category was assigned a value of 32 for both aquifers.

Targets

        Nearest Well. Because Aquifer A is subject to Level I concentrations, assign it a nearest well
factor value of 50 (see MRS section 3.3.1). The distance to the nearest well does not need to be taken
into account.

       The  nearest well factor value for Aquifer B is also 50. Because hazardous substances would
have to migrate  through Aquifer A to reach Aquifer B, evaluate the nearest well factor for Aquifer B and
any overlying aquifers (i.e., Aquifer A). The nearest well in Aquifer B is 2.8 miles from the source and
would therefore  be assigned a nearest well factor value of 3 (see MRS Table 3-11). Use 50, the higher of
the two values, as Aquifer B's nearest well factor value.

        Population. A single, private drinking well uses Aquifer A and serves a family of five. Because
the well is subject to Level I concentrations, multiply the total population by 10. Therefore, the population
factor value for Aquifer A is 50.

       The  municipal well 2.8 miles from the source that serves 12,000 people uses Aquifer B and is
subject to potential contamination. According  to MRS Table 3-12, assign a distance-weighted  population
value  of 2,122. Multiply this value by 1/10 to obtain the potential contamination factor value of 212. Add
to this the factor value of the Level  I concentration population value of 50, which was calculated for
Aquifer A. The total population factor value for Aquifer B is therefore 262.

        Resources. No resource uses, as defined in MRS section 3.3.3, were documented for either
aquifer.

       Wellhead Protection Area. None were designated for either aquifer.

       Targets Factor Category Value. For each aquifer, this value  is the sum of the four factors
detailed above (population, nearest well, resources, wellhead protection area). Therefore, the targets
factor category is 100 for Aquifer A and 312 for Aquifer B.
                                             201                                      Section 7.9

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Likelihood of Release

       Because an observed release by chemical analysis was documented in Aquifer A, assign a
likelihood of release value of 550. A potential to release value of 240 was calculated for Aquifer B, based
on containment, net precipitation, depth to aquifer, and travel time factors.

Ground Water Pathway Score

       As defined  in the MRS section 3.4, calculate a ground water score for each aquifer by multiplying
the likelihood of release, waste characteristics, and targets factor category values and dividing the
product by 82,500.  The ground water score is 21.33 (i.e., [550 x 32 x 100]/82,500) for Aquifer A and
29.04 (i.e., [240 x32 x312]/82,500) for Aquifer B. Therefore, the score calculated for Aquifer B is used
as the ground water pathway score for the site.

TIPS AND REMINDERS

       The nearest well factor value can be based on either the aquifer being evaluatedor  an
       overlying aquifer through which hazardous substances would migrate.

       The population factor for a lower aquifer in a multiple aquifer system includes the population
       served by any  overlying aquifer through which hazardous substances would migrate.
Section 7.9                                     202

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CHAPTER  8
SURFACE  WATER PATHWAY
                              DRINKING WATER THREAT
 LIKELIHOOD
 OF RELEASE
 Observed Release
     or
 Potential to Release

 By Overland Flow
  Containment
  Runoff
  Distance to Surface
   Water

 By Flood
  Containment
  Flood Frequency
                  X
X
                  X
    WASTE
    CHARACTERISTICS

    Toxicity/Persistence
    Hazardous Waste
     Quantity
                  X
 TARGETS

 Nearest Intake
 Population
 Resources
            HUMAN FOOD CHAIN THREAT
WASTE
CHARACTERISTICS

Toxicity/Persistence/
  Bioaccumulation
Hazardous Waste
  Quantity
TARGETS

Food Chain Individual
Population
            ENVIRONMENTAL THREAT
   WASTE
   CHARACTERISTICS

   Ecosystem Toxicity/
     Persistence/
     Bioaccumulation
   Hazardous Waste
     Quantity	
                    TARGETS

                    Sensitive
                      Environments

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SECTION 8.1
HAZARDOUS SUBSTANCE
MIGRATION  PATH
       This section explains how to determine the hazardous substance migration path of the
overland/flood component of the surface water pathway, including how to determine the overland and
in-water segments, and how to identify the PPE and TDL. The guidance in this section does not  apply
to the ground water to surface water component of the surface water pathway.
                            RELEVANT MRS SECTIONS

        Section 4.0.2         Surface water categories
        Section 4.1.1.1       Definition of the hazardous substance migration path for overland
                           flow/flood migration component
        Section 4.1.1.2       Target distance limit
        Section 4.1.2.1.2.1.2  Runoff
        Section 4.1.2.1.2.1.3  Distance to surface water
DEFINITIONS
       Hazardous Substance Migration Path: The path that hazardous substances travel or would
       travel over land from a source to surface water (overland segment) and within surface water to
       the TDL (in-water segment). In certain cases (e.g., sites consisting only of contaminated
       sediments, sites where sources are located m  surface water bodies), the hazardous substance
       migration path consists of only an in-water segment.

       Intermittent Water Body: Water bodies that do not contain water during  all seasons of the year
       under normal conditions.

       In-water Segment: Portion of the hazardous substance migration path from the PPE to the TDL.
       For tidally influenced rivers, the in-water segment may include portions of surface water bodies
       upstream from the PPE to the extent that the in-water migration path is reversed by tides. For
       contaminated sediments  with no identified source, the in-water segment begins at the upstream
       boundary (for streams and rivers) or center (for water bodies with no direction of flow) of the area
       of contaminated sediments.

       Observed Release: An observed release is established for the ground water,  surface water, or
       air migration pathway  either by chemical analysis or by direct observation. Observed release is
       not relevant to the MRS soil exposure pathway. The minimum requirements for establishing an
       observed release by chemical analysis are analytical data demonstrating the presence of a
       hazardous substance  in the medium significantly above background level, and information that
       some portion of that increase is attributable to the site. The minimum criterion for establishing an
       observed release by direct observation is evidence that the hazardous substance was placed into
       or has been seen entering the medium.
                                         203                                  Section 8.1

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       Overland Segment: Portion of the hazardous substance migration path from a source to a
       surface water body.

       Perennial Water Body: Contains water throughout the year under normal conditions. Under
       extreme conditions (e.g., severe drought) some water bodies considered perennial may not
       contain water.

       Probable Point of Entry (PPE): Point at which the overland segment of a hazardous substance
       migration path intersects with surface water. A site may  have multiple PPEs. The PPE is
       assigned as the point at which entry of the hazardous substances to surface water is most likely.

       Surface Water: Water present at the earth's surface. Surface water includes rivers, lakes,
       oceans, ocean-like water bodies, and coastal tidal waters, as defined in MRS section 4.0.2.

       Target Distance Limit (TDL) for the Surface Water Migration Pathway: Distance over which
       the in-water segment of the hazardous substance migration path is evaluated.  The TDL extends
       15 miles from the PPE in the direction of flow (or radially in lakes, oceans, or coastal tidal
       waters) or to the most distant sample  point establishing  an observed release, whichever is
       greater. In tidally influenced surface water bodies, an upstream TDL is also determined. For
       some sites (e.g., sites with multiple PPEs), an overall target distance of greater than 15 miles
       may  result.

       Watershed: Portion of the watershed downgradient of sources at the site. The watershed
       includes the surface water bodies between the PPEs and the TDL (i.e., the in-water segment of
       the hazardous substance migration path). A single watershed includes all in-water segments that
       intersect within the TDL. A site  is in two or more watersheds  if two or more hazardous substance
       migration paths from the sources do not reach a common point within the TDL. In these  cases,
       each distinct watershed is evaluated separately.

DELINEATING THE OVERLAND SEGMENT

       The overland segment is used to evaluate potential to release to surface water and  establish the
PPE. In the simplest case, a site will have one source with a single hazardous substance migration path,
with a single overland segment  (se&ighlight 8-1). Because the overland segment is defined from a
source to surface water, a single site with multiple sources may have more than one hazardous
substance migration path, and  hence more than one overland segment (although they may be very near
to one another and/or may converge). The steps below apply to sources in a single watershed.  These
steps should be repeated for each source within the watershed and for each watershed.

(1)     Identify each source at the site with  a containment factor value greater than 0 for the
surface water pathway. Do not evaluate sources with a surface water containment factor
value of 0.

              In general, each source serves as the beginning of an overland segment.

              Sometimes hazardous substances will have already  migrated from the  source toward
              surface water. If evidence of this migration is  contaminated soil, the contaminated soil is
              itself a source. Use the farthest point of documented soil contamination as the beginning
              of the overland segment (seeHighlight8-2).

              If a site consists of contaminated sediments with no identifiable source, then there is no
              overland segment.
Section 8.1                                    204

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                             HIGHLIGHT 8-1
             HAZARDOUS SUBSTANCE MIGRATION PATH
               Overland Segment
Source
k'"^    I
r       Nx_t--
                                                                       TDL
                            PPE
    The hazardous substance migration path is comprised of two segments:  an overland segment
    and in-water segment.

    The overland segment extends from the source to the PPE.

    The in-water segment extends from the PPE to the TDL

    The overland segment determines the distance to surface water; the in-water segment determines
    the targets that will be evaluated.
                             HIGHLIGHT 8-2
          OVERLAND SEGMENT FOR CONTAMINATED SOILS
                                            If hazardous substances have started to
                                            migrate toward surface water, the overland
                                            segment   is  the  distance   from  the
                                            contaminated soil to surface water.
                                            The contaminated soil must be attributed to a
                                            source  associated with  the  site  being
                                            evaluated.
         Overland Segment
 Determine the overland flow paths that surface water would take from a source to a
 surface water body. Delineate the overland segment by determining the routes that runoff
 would take from a source to surface water. The routes may be determined solely from
 topographic maps;  however, the overland segment generally should be refined from site
 observations.
                                     205
                                                                           Section 8.1

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              Storm sewers and other covered drains (or other man-made runoff controls, such as a
              wall) along the overland migration path must be considered in determining the overland
              flow (see Highlight 8-3).

              If contaminated soil is directly adjacent to the PPE, the distance to surface water is 0.

              At sites with a large source and/or complex topography, there may be more than one
              overland segment from a single source in a single watershed.

       If all the overland segments are greater than 2 miles, assign a value of 0 for the potential to
       release by overland flow component. However, potential to release by flood can still be
       evaluated for that watershed, if applicable.

(3)     Identify the PPE. The PPE is the point where the overland segment reaches an eligible
       surface water body. Eligible surface waters are listed \Highlight8-4.

              Highlight 8-5 provides additional guidance on determining the PPE for water bodies
              with wetlands and for intermittently flowing  streams and ditches.

              At sites with a large source and/or complex topography, there may be more than one
              PPE to a single surface water body (se&lighlight 8-6).

SCORING THE DISTANCE TO SURFACE WATER FACTOR

       Evaluate the distance to surface water factor only for watersheds scored based on potential to
release by overland flow. Do not evaluate this factor for watersheds where an observed release to
surface water has been documented.

(1)     Determine the shortest overland segment from any source with a containment factor
       value greater than 0 to the surface water body. If this distance is near a breakpoint between
       distance ranges in MRS Table 4-7,  use  the  mean high water level for tidal waters or the mean
       water level for other surface waters.
                                     HIGHLIGHT 8-3
               CHARACTERIZATION OF THE OVERLAND SEGMENT FOR
                        STORM SEWERS AND COVERED DRAINS

 Storm sewers and other covered drains along the overland migration pathway have proved difficult to
 characterize for two reasons:

 (2)     Where does the drain discharge come out? Engineering drawings and/or dye tests can help
        determine the migration path through the drain.

 (3)     Are the hazardous substances coming out the far end of the drain attributable to the sources at
        the site? To strengthen the attribution of the hazardous substances to the site:

        —     Carefully document the storm drain's pathway and connections.

        —     Evaluate the contribution of other potential sources to the drain.

        —    Show similarity between the materials from the site that enter the drain and those that come
               out.

 See Section 5.1 for additional guidance concerning attribution.
Section 8.1                                     206

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                                      HIGHLIGHT 8-4
                             ELIGIBLE SURFACE WATERS

MRS section 4.0.2 identifies and categorizes surface water for MRS purposes. Additional guidance on
distinguishing among these types of surface waters is provided  in Section 8.2.

Rivers Include:

       Perennially flowing waters from point of origin to the ocean or to coastal tidal waters;
       Wetlands contiguous to perennially flowing waters;
       Above ground portions of disappearing rivers;
       Man-made ditches that perennially flow into other surface water; and
       Intermittently flowing waters and contiguous intermittently flowing ditches, in arid or semi-arid areas
       with less than 20 inches of mean annual precipitation.

Lakes Include:

       Natural and man-made lakes (including impoundments) that lie along rivers, but excluding the Great
       Lakes;
       Isolated, but perennial lakes, ponds, and wetlands;
       Static water channels or oxbow lakes contiguous to rivers;
       Small rivers, without diking, that merge into surrounding perennially inundated wetlands; and
        Wetlands contiguous to water bodies  defined as lakes.

Ocean and ocean-like water bodies Include:

       Ocean areas seaward from the baseline of the Territorial Sea (I.e., seaward from the generalized
       coastline of the United States);
       The Great Lakes;  and
       Wetlands contiguous to the Great Lakes.

Coastal tidal waters Include:

       Waters that are seaward from mouths  of rivers and landward from the baseline of the Territorial Sea
       (e.g., embayments, harbors, sounds, estuaries, back bays, lagoons, wetlands).

Surface waters specifically excluded from evaluation as surface water bodies for MRS purposes
Include:

       Intermittent rivers in areas with 20 or more inches mean annual precipitation;  and
       Intermittent ponds or lakes, regardless of mean annual precipitation.
              If there is only one overland segment, the distance to surface water is the distance from
              a source to the PPE, measured along the overland segment.

              If there are two or more overland segments, the distance to surface water is the shortest
              distance from any source to the PPE for the watershed being evaluated.

              —      If the in-water segments associated with different overland segments reach a
                     common  point within the TDL, select the shortest overland segment, and use
                     its length as the distance to surface water (seMighlight 8-6).

              —      If the in-water segments associated with different overland segments do not
                     reach a common point within the TDL, the site is in more than one watershed
                     (see Highlight 8-6). Assign a separate distance to surface water factor and
                     calculate a separate surface water pathway score for each watershed. Section
                     8.2 provides guidance on scoring sites with more than one watershed.
                                             207                                       Section 8.1

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                                  HIGHLIGHT 8-5
                           PROBABLE POINT OF ENTRY
                 FOR WETLANDS AND INTERMITTENT STREAMS
                                                        A wetland contiguous to river, lake,
                                                        or coastal tidal water is considered to
                                                        be surface water. PPE1  is where the
                                                        overland segment meets the wetland.
                                                        Intermittently flowing  streams  and
                                                        ditches are considered surface water
                                                        only in arid areas with less than 20
                                                        inches mean annual precipitation.
                                                             is the PPE  in such areas.
                                                        PPE2 is the PPE in areas with 20
                                                        inches  or  more
                                                        precipitation.
(2)     If the shortest overland segment for a watershed exceeds 2 miles, potential to release by
       overland flow cannot be evaluated for the watershed. Assign potential to release by overland
       flow a value of 0 for the watershed.

(3)     Assign a distance to surface water factor value using MRS Table 4-7. Because this factor is
       assigned based on distance ranges, precise measurement of the distance of the overland
       segment is generally not necessary unless the distance is near a breakpoint between two ranges.

SCORING THE FLOOD  FREQUENCY FACTOR

(1)     Determine the floodplain category (i.e., floods annually, 10-year, 100-year, 500-year) in
       which the source is partially or wholly located. Potential to release by flood does not
       consider distance to  surface water. Therefore, a source with an overland segment greater
       than 2 miles can be evaluated if it is located in an appropriate floodplain.
(2)
Assign a flood frequency factor value using MRS Table 4-9.
EVALUATING THE TARGET DISTANCE LIMIT FOR NON-TIDALLY INFLUENCED
WATER BODIES

       This section discusses determining the TDL for sites with and without a PPE, sites with multiple
PPEs, and sites where the in-water segment branches.

A.     SITES WITH A SINGLE PPE

(A1)    Determine the PPE, based on delineation of the overland flow segment.

(A2)    Measure the distance along each surface water body. Measure from the PPE to the most
       distant sampling point that meets the observed release criteria (downstream for rivers and
       streams; or radially for lakes, oceans, and coastal tidal waters).
Section 8.1
                                          208

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                                    HIGHLIGHT 8-6
            PROBABLE POINT OF ENTRY AND TARGET DISTANCE LIMIT
             FOR SITES WITH MORE THAN ONE OVERLAND SEGMENT
                PPE,
                              PPE,
Use the distance of the shortest overland
segment to  assign the distance to surface
water factor value.
               PPE
                   PPE
                                                  The in-water segments for Sources 1  and 2
                                                  reach a common point within the TDL Source
                                                  1 and Source 2 are in the same watershed.
                      PPE
                                                  The in-water  segments for Source 1 and
                                                  Source 2 do not reach a common point within
                                                  the TDL.   Source 1 and Source 2 are  in
                                                  different watersheds.
                                        TDL2
              If no sample meets the observed release criteriapj if the most distant sample that
              meets this criteria is less than 15 miles from the PPE (measured along the surface water
              body), extend the TDL to 15 miles from the PPE (se
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                                  HIGHLIGHT 8-7
                     DETERMINING TARGET DISTANCE LIMIT
                                                 For a river, the TDL Is 15 miles downstream
                                                 from the PPE.
                                                 For a lake, ocean, or coastal tidal water,
                                                 direction of flow is not considered.  The TDL
                                                 is drawn as an arc with radius of 15 miles.
                                                 If the TDL for a water body includes both a
                                                 river/stream and an open water body, the sum
                                                 of the downstream distance and radius of the
                                                 arc equals 15 miles.
                                   HIGHLIGHT 8-8
               DETERMINING TARGET DISTANCE LIMIT FOR SITES
                  WITH OBSERVED RELEASE BEYOND 15 MILES
                         15 mites  Farthest
                                 sample point
                                 establishing
                                 observed release
When the farthest sample  establishing  an
observed release is more than 15 miles from
the PPE, the TDL is extended to this point.
                           establishing observed release
Section 8.1
                                         210

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B.     SITES WITH MORE THAN ONE PPE

       For sites with more than one PPE, define an in-water segment for each PPE, and evaluate
targets in each in-water segment of a watershed.

(B1)   Determine the location of each PPE based on delineation of the overland flow segment.

(B2)   Identify the In-water segment from each PPE.

(B3)   Determine whether the site is within one watershed.

              If all of the in-water segments from each PPE do not join within the TDL, consider the
              site to be in more than one watershed. Evaluate each watershed separately and use the
              highest score for any watershed as the surface water pathway score for the site (see
              Section 8.2).

              If all of 8.2 the in-water segments from each PPE join within the TDL, consider the site to
              be in one watershed and evaluate the in-water segment as follows.


              —     If the PPEs for different sources are in the same water body and are relatively
                     close together, determine  a single PPE. Evaluate the TDL as described for a
                     single PPE.

              —     If hazardous substances from different sources enter the same water body at
                     distant points, the target distance is the distance from the most upstream PPE to
                     15 miles downstream from the most downstream PPE (or the combined
                     overlapping arcs for two or more PPEs into a lake, coastal tidal water, or ocean).
                     This may result in an overall TDL of greater than 15 miles (see High lights 8-9
                     and 8-70). The downstream PPE must be within the TDL of the upstream PPE. If
                     this is not true, each PPE  is considered to be in a separate watershed and each
                     watershed is scored separately.

              —     If the PPEs for different sources are in two different water bodies (e.g., two
                     rivers, two lakes) that later merge into one water body, determine the target
                     distance from each PPE for each source. Total targets are the sum of each
                     segment for each water body. Count targets common to more than one source
                     only once (see Highlights 8-11 and 8-72). The merge point should be within the
                     TDL of each PPE; otherwise the sources are considered to be in two or more
                     watersheds.

C.     SITES WHERE THE IN-WATER SEGMENT BRANCHES

(C1)   Measure the TDL separately for each branch.

(C2)   Determine If the branches join within the TDL.

              If the branches do not rejoin within the TDL, determine the TDL in each branch
              separately (seeHighlight 8-13).

              If the branches rejoin within the TDL,  determine the TDL within each branch and select
              the one that is farthest downstream (see High light 8-13).

(C3)   Score only those surface water targets that are located  partially or wholly within, or
       contiguous to, the TDL. Targets in all branches (see High light 8-13) are considered when
       evaluating the watershed.


                                            211                                    Section 8.1

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                                HIGHLIGHT 8-9
             DETERMINING TARGET DISTANCE LIMIT FOR SITES
     WITH MORE THAN ONE PROBABLE POINT OF ENTRY INTO RIVERS
                                  Flow
                                     TDL,
                                         TDL2
                    PPE,
                                  Flow
                    Souro«2|
                               ,TDL,
                                  ;TDL,
When a site has more than one PPE
and the in-water segments join within
the TDL, the In-water segment for
evaluating the site extends from the
most upstream PPE (PPEt) to the
most downstream TDL CTDLg). The
length of the in-water segment in this
case may be longer than  15 miles,
regardless  of   whether  actual
contamination Is  documented.   In
both illustrated cases, use TDLg as
the TDL for the site.
                                HIGHLIGHT 8-10
      DETERMINING TARGET DISTANCE LIMIT FOR SITES WITH MORE
            THAN ONE PROBABLE POINT OF ENTRY INTO LAKES
                  Source 11 (Soure>4|  j
                                        15 miles    /
        Determine the TDL from PPE1, the PPE to the lake for Source 1.

        Determine the TDL from PPE2, the PPE to the lake for Sources 2, 3, and 4.

        Determine the aggregate TDL  In this example, it is the shape formed by arc ABC and arc CDE.
        If the TDLs do not intersect, the water bodies are considered separate watersheds and each
        watershed is evaluated separately.
Section 8.1
                                        212

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                          HIGHLIGHT 8-11
  DETERMINING TARGET DISTANCE LIMIT FOR SITES WITH
               PROBABLE POINTS OF ENTRY  INTO
                  TWO BRANCHES OF A RIVER
The PPE for Source 4 (PPE2) is in a different water body than the PPE for Sources 1, 2, and 3
(PPE,).

To determine the target distance, include all of the following:

—      The distance from PPE1 to Point Z, the juncture of the two water bodies;
—      The distance from PPE2 to Point Z; and
—      The distance from Point Z to a point 15 miles minus the distance (Z - PPE.,) or 15 miles
       minus the distance (Z - PPE2), whichever is greater.

Consider all waters with PPEs when calculating the total target population values. In this example,
consider segment PPE1 - Z, segment PPE2 - Z, and segment Z - end of TDL when determining the
target populations.

If the distance from either PPEt to Point Z or PPE2 to Point Z is greater than 15 miles, this example
should be scored as two separate watersheds.
                                  213
                                                                         Section 8.1

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                                    HIGHLIGHT 8-12
                   DETERMINING TARGET DISTANCE LIMIT FOR
          SITES WITH PROBABLE POINTS OF ENTRY INTO TWO LAKES
   NOTE: Graphic not to scale.

   •     In this example, the site has probable points of entry into two lakes (PPE1 and PPE2) with outflow to
         the same river. In this situation, the lakes should be considered in the same watershed because their
         in-water segments meet within 15 miles.

   •     Measure the TDL in each lake. Also, measure the distance from the PPE to the point of outflow to the
         river.

   •     In this example, the TDLs would be:

         —      The 15-mile target distance in each lake;
         —      The river segments from the lake outfall to the point the outfalls from each lake meet, A-B
                 and D-B; and
         —      The 11-mile distance from point B to point C, which is 15 miles from the PPE for Lake 2.
                 This distance Is used because it is farther downstream than the TDL for the PPE into Lake
                 1 (which would end 1 mile upstream of point C).
Section 8.1
                                            214

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                                  HIGHLIGHT 8-13
                DETERMINING TARGET DISTANCE LIMIT WHEN
                      THE IN-WATER SEGMENT BRANCHES
           Flow
                                                 If the branches do not rejoin within the TDL,
                                                 mark the TDL in each branch independently.
                                                 Count targets in each branch.
                                                  If  the  branches  rejoin  within the TDL,
                                                  determine the TDL for each branch and select
                                                  the one that is farthest downstream.  Count
                                                  targets in each branch and in the combined
                                                  portions.
D.     SITES CONSISTING SOLELY OF CONTAMINATED SEDIMENTS WITH NO IDENTIFIED
       SOURCE

(D1)    Determine if the surface water body containing the contaminated sediments has a clearly
       defined direction of flow.

             If there is a clearly defined direction of flow, proceed to Step (D2).
             If there is no clearly defined direction of flow, proceed to Step (D4).

(D2)    When there is a clearly defined direction of flow, begin measuring the TDL from the
       farthest upstream sediment sampling point that meets the criteria for an observed
       release.

(D3)    Use the sediment sampling point Identified in Step (D2) in lieu of the PPE.

             Follow Steps (A2) and (A3) for sites with a single  PPE to determine the TDL.
             Skip Steps (D4), (D5), and (136) below.

(D4)    When there is no clearly defined direction of flow, begin measuring the TDL at the center
       of the area of observed sediment contamination. Determine the center using only those
       sediment sampling points that meet the criteria for an observed release.

(D5)    Extend the TDL as an arc with a radius extending either 15 miles along the surface water, or to
       the most distant sample point that meets the observed release criteria to surface water,
       whichever is greater. See Highlight 8-14 for an example of determining  the TDL in this case.

(D6)    Score only those surface water targets that are located partially or wholly within, or contiguous to,
       the TDL.
                                          215
                                                                                 Section 8.1

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                                  HIGHLIGHT 8-14
                 DETERMINING TARGET DISTANCE LIMIT FOR
         SITES CONSISTING SOLELY OF CONTAMINATED SEDIMENTS

           Area of observed
           sediment contamination
                                                 Clearly Defined Flow Direction:
                                                 Use the most upstream sediment sampling
                                                 point that meets the observed release criteria
                                                 as the beginning  of the in-water segment.
                                                 TDL is 15 miles downstream from this point.
   Beginning of
   in-water
   segment
                                                 No Clearly Defined Flow Direction:
                                                 Use the center  of the area of observed
                                                 sediment contamination as the beginning of
                                                 the in-water segment. Draw the 15-mile arc for
                                                 the TDL from this point.
       Center of area of
       observed sediment
       contamination
EVALUATING THE TARGET DISTANCE LIMIT FOR TIDALLY INFLUENCED WATER
BODIES

       In tidally influenced water bodies, the TDL may extend upstream from the PPE of hazardous
substances. Evaluate the downstream TDL for such water bodies in the same manner as for other
surface water bodies. The following procedures describe how to  establish the upstream TDL for tidally
influenced water bodies.

(1)     Because the evaluation of tidal Influence Is complex, determine If there are any significant
       upstream targets (e.g., sensitive environments, wetlands, fisheries).

              If there are  no significant upstream targets, do not evaluate the effect of tidal influence
              on the TDL.

              If there are  significant upstream targets, proceed to Step (2).

(2)     Document how far upstream the tide can carry hazardous substances. Use existing
       documentation on the upstream point of flow reversal, extent of brackish water, or salt water
       intrusion data. Such documentation is often available from  local water authorities. Often,
       these data can be obtained from appropriate state agencies such as water resource
       commissions.

(3)     Locate the farthest upstream sample establishing an  observed release.

(4)     Determine the upstream boundary of the TDL. The upstream boundary of the TDL depends
       on the extent of tidal carry and the farthest upstream observed release sample.Highlight 8-15
       illustrates these  considerations.
Section 8.1
                                          216

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        If the farthest upstream sampling point establishing an observed release is located
        greater than 15 miles from the PPE, use the location of that sampling point as the
        upstream boundary of the TDL.

        If the tidal influence is at least 15 miles upstream from the PPE, use 15 miles upstream
        from the PPE as the upstream boundary of the TDL.

        If the tidal influence is less than 15 miles upstream from the PPE, use the documented
        distance to which the tide could carry hazardous substances as the upstream boundary
        of the TDL.
                              HIGHLIGHT 8-15
         DETERMINING UPSTREAM TARGET DISTANCE LIMIT
                   FOR TIDALLY INFLUENCED RIVERS
                     TDL
                              Flow-
                                 Sourcej
                     Extent  ~
                     of Tidal  Farthest PPE
                     Carry   Upstream
                            Observed Release
                            Sample
                        Upstream TDL is the documented
                        point to which the tide can carry the
                        hazardous substance, because this
                        is less than 15 miles from the PPE.
              TDL
        Extent
        of Tidal
        Cany
               15 mile
                                 Flow-
                                    Source
Farthest
Upstream   PP
Observed Release
Sample
Upstream TDL is 15 miles from the
PPE, because the documented point
to   which  the  tide  can  carry
hazardous substances is greaterthan
15 miles from the PPE.
       TDL
             15 mile
        Farthest
Extent   Upstream
of Tidal  Observed Release
Carry    SamP|e
                                 Flow
       Source
           PPE
Upstream  boundary  of  TDL  is
location of the farthest upstream
sampling  point  establishing  an
observed release, because this point
is greater than  15 miles from the
PPE.
                                     217
                                                                             Section 8.1

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TIPS AND REMINDERS

       Consider a perennially flowing irrigation ditch as part of the in-water segment of the hazardous
       substance migration path.

       If there is no HRS-defined surface water body within 2 miles of the site, do not evaluate the
       surface water pathway, unless there is an observed release to surface water from the site or the
       site is in a 500-year (or less) floodplain of the nearest surface water.

       Intermittent rivers in areas with 20 or more inches mean annual precipitation and  intermittent
       lakes (regardless of annual precipitation) are not evaluated as surface water bodies for MRS
       purposes.
Section 8.1                                      218

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SECTION 8.2
DELINEATION  OF
WATERSHEDS AND
DRAINAGE AREAS
                                                                  LR
       This section provides guidance on the determination of watersheds, drainage areas and their
boundaries, and discusses the use of watershed and drainage area evaluations within the MRS. A
watershed is the area drained by, or contributing water to, a surface water body. If the sources at a site
are in more than one watershed, each watershed is evaluated separately, and the highest score for any
watershed is assigned as the surface water pathway score. The portion of a watershed upgradient from
the sources at the site is delineated to determine a drainage  area category, which is used to score the
runoff factor for potential to release.
              Section 4.0.2
              Section 4.1.1.1
              Section 4.1.1.2
              Section 4.1.2.1.2.1.2
                             RELEVANT MRS SECTIONS
Surface water categories
Definition of the hazardous substance migration path for
overland flow/flood migration component
Target distance limit
Runoff
DEFINITIONS
       Direction of Overland Flow: Determined on a topographic map by drawing flow lines
       perpendicular to contour lines. Direction of flow will normally be along these flow lines, from
       areas of higher elevation toward areas of lower elevation but can be affected by man-made
       barriers such as walls and sewers. The determination of flow direction is important for identifying
       the drainage area upgradient of sources at the site and for identifying the overland segment of
       the hazardous substance migration path.

       Drainage Area: The area upgradient of sources contributing water to the sources via overland
       flow; this area is based on topography,  except where overland flow is captured and/or diverted
       (e.g., storm sewers, run-on control features,  walls) around the source. In cases where upland
       flow is captured or diverted, only the area of the source and areas upgradient of the source
       between the source and the device or structure diverting overland flow from the source are
       included in the drainage area.

       Hazardous Substance Migration Path: The path that hazardous substances travel  or would
       travel over land from a source to surface water (overland segment) and within surface water to
       the TDL (in-water segment).  In certain cases (e.g., sites consisting only of contaminated
       sediments, sites where sources are located iri  surface water bodies), the hazardous substance
       migration path consists of only an in-water segment.

       In-water Segment: Portion of the hazardous substance migration path from the PPE to the TDL.
       Fortidally influenced  rivers, the in-water segment may include portions of surface water bodies
       upstream from the PPE to the extent that the in-water migration path is reversed by
                                          219
                                                                               Section 8.2

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       tides. For contaminated sediments with no identified source, the in-water segment begins at the
       upstream boundary (for streams and rivers) or center (for water bodies with no direction of flow)
       of the area of contaminated sediments.

       Overland Segment: Portion of the hazardous substance migration path from a source to a
       surface water body.

       Probable Point of Entry (PPE): Point at which the overland segment of a hazardous substance
       migration path intersects with surface water. A site may have multiple PPEs. The PPE is
       assigned as the point at which entry of the hazardous substances to surface water is most likely.

       Target Distance Limit (TDL) for the  Surface Water Migration Pathway: Distance  over which
       the in-water segment of the hazardous substance migration path is evaluated. The TDL extends
       15 miles from the PPE in the direction of flow (or radially in lakes, oceans, or coastal tidal
       waters) or to the most distant sample  point establishing an observed release, whichever is
       greater. In tidally influenced surface water bodies, an upstream TDL is also determined. For
       some sites (e.g., sites with multiple  PPEs), an overall target distance of greater than 15 miles
       may result.

       Watershed: Portion of the watershed downgradient of sources at the site. The watershed
       includes the surface water bodies between the PPEs and the TDL (i.e., the in-water  segment of
       the hazardous substance migration path). A single watershed includes all in-water segments that
       intersect within the TDL. A site is in two or more watersheds if two or more hazardous substance
       migration paths from the sources do not reach a common point within the TDL. In these cases,
       each distinct watershed is evaluated separately.

DELINEATING WATERSHEDS

       The key to evaluating watersheds is to first identify the hazardous substance migration paths
(see Section 8.1). Most sites are in a single watershed. However, multiple watersheds may be identified
for larger sites. Where multiple watersheds occur, evaluate each watershed separately.

(1)     Compile maps that show the sources being evaluated and all surface water bodies within
       the TDL.

              Locate all sources on a map.

              Examine topography and surface water bodies around the site to identify PPEs (if this is
              not possible, use a straight line distance  between sources at the site and surface water
              bodies to estimate locations of PPEs).

              Compile sufficient maps to evaluate 15 miles radially or downstream of all PPEs, as
              appropriate. Additional maps  may be needed as the  hazardous substance migration path
              is refined to reflect precise locations of PPE's, TDLs within a water body, and tidal
              influences.

(2)     Identify the overland segment from each source to all surface water bodies within 2 miles
       of the source. Identify all other routes of migration to surface water, such as flooding.
       (Remember,  for surface water migration by flooding, sources in a 500-year or less floodplain do
       not need to be within 2 miles of a surface water body.)

              Each source may have multiple overland segments to a single surface water body or to
              different surface water bodies, establishing multiple PPEs. These PPEs may or may not
              differ for sources.
Section 8.2                                    220

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              Locate each overland segment and associated PPE on the maps. The overland segment
              may not be able to be determined solely from a topographic map. Supplement the maps
              with field observations, if needed, to determine the presence of man-made impediments.

              Locate all other PPEs due to flooding or observed releases by direct observation to
              surface water.

(3)     For each PPE, draw the In-water segment of the hazardous substance migration path to
       the TDL.

(4)     All hazardous substance migration paths with in-water segments that intersect within the
       TDL are considered to be In the same watershed for scoring purposes.

              Targets for a watershed are evaluated along all portions of the hazardous substance
              migration paths comprising the watershed.

              All sources with PPEs in a watershed are assigned to that watershed for scoring
              purposes. A source can be assigned to more than one watershed.

       Highlight 8-16 provides an example of delineating a single watershed.Highlight 8-17 provides
an example of evaluating multiple watersheds.

DETERMINING DRAINAGE AREA

       Drainage area includes both the area of the sources and the areas upgradient of sources that
can contribute runoff to the sources. Drainage area is evaluated under potential to release via overland
flow and is evaluated separately for each watershed. It is not necessary to evaluate drainage area if an
observed release has been established.

       MRS Table  4-3 provides factor values assigned to drainage areas. As shown in that table,
drainage area is evaluated within broad ranges, with ranges between 50, 250, and 1,000 acres. The level
of precision required for drainage area calculations should be consistent with the need to identify the
appropriate range.

       Both the area  of sources for each watershed and the areas upgradient of these sources can be
readily estimated  from USGS topographic maps. Observations from the SI may be critical for identifying
runoff control or diversion structures (e.g.,  storm drains) that may not appear on topographic maps.

(1)     Determine  the area (or portion of the area) of each source applicable for the watershed
       being evaluated. Information may be available from hazardous waste quantity evaluations.

              If source dimensions are known from site visits or other information, use this to
              determine  area.

              If source dimensions are not known, locate each source on a topographic map and
              approximate dimensions using the map scale.

(2)     Determine  the area upgradient of each source.

              Identify structures or features that prevent the flow of runoff onto, across, and/or off
              sources at the site; field observations should identify locations of such structures.

              Determine upgradient areas based  on a topographic map (or other representations of
              elevation data).
                                            221                                     Section 8.2

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                                   HIGHLIGHT 8-16
                     DEFINING A SINGLE WATERSHED WITH
                     MULTIPLE PROBABLE POINTS OF ENTRY
       Flow/ North
           Run
         Row
                 Contour lines
                 Water body
          _ _ _.  overland segment

         In this example, two sources are located along a topographic high.

         Establish all PPEs for each source.

         Determine the TDLs from each PPE:

         —      The TDL from PPE1 ends farthest downstream, past the confluence of the East and West
                Branches (TDL^.

         —      The TDL from PPE2 ends just past the confluence of the East and West Branches (TDLg).

         —      The TDL from PPE3 ends on the East Branch (TDLg).

         Since the hazardous substance migration paths for both sources overlap within the TDL, evaluate the
         in-water segments of North Run, East Branch, and West Branch  as a single watershed, using TDL1
         as the TDL for the site.
Section 8.2
                                            222

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                               HIGHLIGHT 8-17
                   DEFINING MULTIPLE WATERSHEDS
                  Red
1
                                                               TDU
        L
[Source 41
                              Watershed 1
                                Watershed Bourtfar^
   In this example, four sources are located at a single site.

   Establish PPEs for each source.

   Determine the in-water segment for each PPE.

   The hazardous substance migration paths for Sources 1,2, and 3 overlap to establish one watershed.

   The hazardous substance migration path for Source 4 does not overlap with any others; a second
   watershed is established.

   Sources 1, 2, and 3 are assigned to Watershed 2 for scoring purposes and Source 4 is assigned to
   Watershed 1.

   If the  hazardous substance migration path for Source 2 did  not reach Blue River  (TDL^j, three
   watersheds would be scored — Source 1 with a PPE into Blue River, Sources 2 and 3 with PPEs into
   Yellow River, and Source 4 with a PPE into Red River.
                                        223
                                                                                   Section 8.2

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               Outline the areas upgradient of each source, as follows:

               —     Draw flow lines on the topographic maps, perpendicular to the contour lines.

               —     Place arrows on the flow lines in the direction of decreasing elevation.

               —     For flow lines that intersect sources, extend the flow lines in the upgradient
                      direction (i.e., direction of increasing  elevation) until one of the following is
                      reached:

                             A structure or feature that prevents runoff from crossing the source (e.g.,
                             railroad track, wall, road); or

                             An area where  elevation ceases to increase.

               —     Draw an  outline around the areas contained by flow lines that intersect a source
                      and meet the criteria outlined above.

               Calculate the area within the outline of the drainage area using the scale of the
               topographic map.

       Highlights 8-18 and 8-19 provide examples of determining drainage area.
Section 8.2                                      224

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                             HIGHLIGHT 8-18
                 DRAINAGE AREA DETERMINATION
        .'High  y

                Drainage boundary

                Drainage direction


                Contour line
Draw flow lines perpendicular to the nearest upgradient contour line from the edges of each source.

Extend the flow lines between contour lines in the upgradient direction until a topographic high is
encountered (a closed ring on a topographic map).

Close off the drainage area at the topographic high.

—      For circular topographic highs, use the center of the area enclosed by the highest contour
        line as the highest point of elevation.

—      For elongated topographic highs, draw a ridge line along the center of the length of the area
        enclosed by the highest contour line to represent the highest points of elevation.
                                      225
                                                                                  Section 8.2

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                                     HIGHLIGHT 8-19
           DRAINAGE AREA RESTRICTED BY MAN-MADE STRUCTURES
                          I   ""	I	'	*	

                        Drainage boundary

                        Drainage area excluded

                        Drainage direction


                        Contour line
           Draw flow lines perpendicular to the nearest upgradient contour line from the edges of each source.

           Extend the flow lines between contour lines in the upgradient direction until a topographic high is
           encountered (a closed ring on a topographic map).

           A roadway and railroad tracks are located on opposite sides of the surface water body.

           The roadway and railroad tracks  are upgradient of the sites and are considered to divert runoff from
           the sites.

           Boundaries of the drainage area do not extend beyond the railroad tracks or roadway.
Section 8.2
                                              226

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TIPS AND REMINDERS

       Score each watershed separately within the surface water migration pathway. Use the
       watershed with the highest score as the pathway score for the site.

       Establish a single watershed for all hazardous substance migration paths whose in-water
       segments intersect within the TDL.

       An isolated body of surface water (e.g., small lake or pond) is evaluated as a separate
       watershed. In an area with several isolated ponds, wetlands, lakes, or quarries, consider each
       to be a separate watershed.

       Evaluate drainage area at the level of detail needed to identify the appropriate factor value
       range, which has breakpoints defined at 50, 250, and 1,000 acres. Often the measure or
       estimate of drainage area does not need to be very precise because of these ranges.

       Drainage area boundaries are  important for evaluating the soil group factor, which considers
       the  predominant soil group within the drainage area boundaries.
                                            227                                     Section 8.2

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SECTION  8.3
CHARACTERIZATION OF
SURFACE WATER BODIES
       This section explains how to characterize several aspects of surface water for the purpose of
evaluating the surface water pathway. Specifically, this section explains how to determine the surface
water body category, how to determine the salinity category of surface water, and  how to evaluate
targets in multiple water body categories. The surface water body category is important for determining
TDLs, dilution weights, and persistence factors. Salinity categories are important for selecting
bioaccumulation potential and ecosystem bioaccumulation potential factor values, ecosystem toxicity
values, and ecological-based benchmarks.
                              RELEVANT MRS SECTION

              Section 4.0.2        Surface water categories
              Section 4.1.2.3.1      Nearest intake
              Section 4.1.3.2.1.3    Bioaccumulation potential
              Section 4.1.4.2.1.1    Ecosystem toxicity
              Section 4.1.4.2.1.3    Ecosystem bioaccumulation potential
              Section 4.1.4.3.1      Sensitive environments
DEFINITIONS
       Bioaccumulation Potential: Evaluates the tendency for a substance to accumulate in the tissue
       of an aquatic human food chain organism and forms one component of the
       toxicity/persistence/bioaccumulation and toxicity/mobility/persistence/bioaccumulation factors
       within the human food chain threat-waste characteristics factor category.

       Brackish Water: Water with an average tidal cycle chloride concentration of greater than 250
       mg/l but less than 18,700 mg/l (corresponding to salinity of greater than 0.45 but less than 34
       parts per thousand).

       Dilution Weight: A unitless parameter that adjusts the assigned point value for certain targets
       subject to potential contamination based on the flow or depth of the water body at the target.

       Ecosystem Bioaccumulation Potential: Evaluates the tendency for a substance to accumulate
       in the tissue of any aquatic organism, not just human food chain organisms (as in
       bioaccumulation potential), and forms one component of the ecosystem toxicity/
       persistence/bioaccumulation and ecosystem toxicity/mobility/persistence/bioaccumulation factors
       within the environmental threat-waste characteristics factor category. MRS Table 4-15 and
       sections 4.1.3.2.1.3 and 4.1.4.2.1.3 provide the data hierarchy to follow when evaluating
       bioaccumulation potential.

       Ecosystem Toxicity: The toxicity of a substance to aquatic organisms. It forms one component
       of the ecosystem toxicity/persistence/bioaccumulation and ecosystem
                                          229                                    Section 8.3

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       toxicity/mobility/persistence/bioaccumulation factors within the environmental threat-waste
       characteristics factor category. MRS Table 4-19 provides the data hierarchy to follow when
       evaluating ecosystem toxicity.

       Flow: The long-term average annual discharge of a river or stream (i.e., the annual discharge
       averaged over many years of record).

       Fresh Water: Water with an average tidal cycle chloride concentration of 250 mg/l or less
       (corresponding to salinity of 0.45 parts per thousand or less).

       Salt Water: Water with an average tidal cycle chloride concentration of 18,700 mg/l or greater
       (corresponding to salinity of 34 parts per thousand or greater).

DETERMINING  BREAKPOINTS BETWEEN  SURFACE WATER CATEGORIES

       Determining  the breakpoint between surface water categories is the first step in identifying the
water body type in which a target is located. If targets clearly are located within a particular category, it
generally is sufficient to approximate these breakpoints (e.g., by drawing lines on a scale map or
diagram). When targets are  located close to a breakpoint, determine the breakpoints with greater
precision, as follows.

(1)     Determine the breakpoint between rivers and coastal tidal waters. The mouths of rivers are
       the breakpoints between rivers and coastal tidal waters. Estuarine portions of rivers affected by
       tidal waters are classified as rivers under the MRS. The presence of tidal water is not  a criterion
       for separating  rivers from coastal tidal waters. Identify the mouths of rivers using the following
       sources.

              Contact the  appropriate river basin commission, state or local planning commission,
              district office of the U.S. Army Corps of Engineers, or the state or district office of the
              USGS Water Resources Division to identify the river mouth. For many areas,  river
              mouths have been established through intergovernmental processes and legal definition.

              Refer to river reach data bases (e.g., STORET) to  determine river mile 0 for the  river in
              question. This can be used as a surrogate for the river mouth.

              Manually draw the river mouth from headland to headland (e.g., the mouth of the
              Potomac River is drawn from Point Lookout, MD to Smith Point, VA). Where headlands,
              points, or other topographic features are not identifiable, delineate the mouth  of the river
              so as not to  depart from the general direction of the shoreline of the coastal tidal water
              body into which the river flows. In general, the area of the river lying within the line
              should be subject to the net seaward flow.

(2)     Determine the breakpoint between coastal tidal waters and the ocean. The baseline of the
       Territorial Sea is the breakpoint between coastal tidal waters and the ocean. Consider the
       following to identify the baseline of the Territorial  Sea.

              The  baseline of the Territorial Sea is indicated on some nautical maps, especially when
              local intergovernmental agreements have established an unusual baseline configuration.

              If the baseline of the Territorial Sea is not indicated on available charts, determine the
              baseline from maritime boundaries (3, 9, or 12 nautical  mile lines) shown on
              conventional nautical coast charts prepared by the National Oceans Service,  or similar
              coastal maps.


Section 8.3                                     230

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       —     Measure back toward the shoreline from the maritime boundaries nearest to the shore
              shown on the available charts. See Highlight 8-20.

       —     On December 27, 1988, the maritime boundary was moved from 3 miles to  12 miles
              from the baseline of the Territorial Sea. Therefore, measure back either 3 or 12 nautical
              miles from the maritime boundary, depending on the date of the nautical chart.

       —     The maritime boundary is 3 leagues from the baseline of the Territorial Sea in the Texas
              and Florida Gulf Coasts and in Puerto Rico.

       —     A maritime boundary may meander as it aligns with offshore sandbars or other features.
              In such cases, waters located offshore, but shoreward of a sandbar, are classified as
              coastal tidal waters for MRS purposes.

(3)     Determine the breakpoints between lakes and rivers. The heads of rivers leading from a lake
       or the mouths of rivers entering a lake are the breakpoint between lakes and rivers.

              Breakpoints between rivers and lakes should be determined by  looking at maps for
              obvious areas of in-flow or out-flow.

              A constant elevation across a water surface is indicative of a lake, while a drop in
              elevation is indicative of a river. This criterion may be used to determine breakpoint
              between the two.

              If not easily determined (i.e., broad widening of river into lake), approximate the
              breakpoint as half the distance between the start and end points of the widening.

ASSIGNING SURFACE WATER DILUTION WEIGHTS

       Targets subject to potential contamination are evaluated using dilution weights as outlined in
MRS Table  4-13. The dilution weight reduces the  point value assigned to targets subject to  potential
contamination as the  flow or depth of the surface water body increases. To  assign a dilution weight in a
river, estimate the flow at targets. For lakes, assign the dilution weight based on flow into or out of the
lake. For oceans and the Great Lakes, assign the dilution weight based on depth of the ocean or Great
Lake. Dilution weights are assigned  based on ranges of flow or depth; precise measurement generally is
needed only near a range breakpoint.

(1)     Identify locations where flow must be estimated.

              For rivers, flow is estimated at locations of targets subject to potential contamination.

              For lakes, flow is estimated as follows:

              —      For a lake with  surface water flow entering, assign a dilution weight based on the
                      sum of the average annual flows for the surface water bodies entering the lake,
                      up to the location of the target.

              —      For a lake with  no surface water flow entering, but that does have surface water
                      flow leaving, assign a dilution weight based on the sum  of the average annual
                      flows for the surface water bodies leaving the lake.

              —      For a lake with  no surface water flow entering or leaving, assign a dilution weight
                      based on the average annual ground water flow into the lake, if available. If not
                      available, assign a default dilution weight of 1.
                                             231                                      Section 8.3

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                                      HIGHLIGHT 8-20
         BREAKPOINT BETWEEN COASTAL TIDAL WATERS AND OCEAN
                                                                 Maritime Boundary
                                                               (e.g., 3 or 12 nautical mile line)
                       Inland Bay
                    (Coastal Tidal Water)
                  Coastal Tidal Water
             Generalized Coastline
             (Basetine at Territorial Sea)
   The baseline of the Territorial Sea is the boundary between coastal tidal waters and the ocean.  If the baseline
   of the Territorial Sea is not indicated on a nautical map, determine it as follows:
          Find the maritime boundary on a nautical map.
          Determine whether the boundary Is 3 or 12 nautical miles from the baseline of the Territorial Sea,
          depending on the date of the map. On December 27,1988, the boundary was moved from 3 to 12
          nautical miles from the baseline.
          Measure the appropriate distance (3 or 12 nautical miles) shoreward from the maritime boundary.
(2)     Determine If flow data are available at the locations Identified above. If gauging stations are
       located near the locations identified in Step (1), assign a dilution weight using average annual
       discharge or flow data from these stations. Highlight 8-21 lists sources of flow data. When no
       gauging stations are located near these locations, estimate the average annual discharge or flow
       for the target as summarized in the subsection below, Estimating Flow.

(3)     Estimate the flow at each location Identified In Step (1). Four methods that can be used to
       estimate flow are: (1) interpolation of flow data, (2) extrapolation of flow data, (3) estimation of
       flow using downstream gauging stations, and (4) estimation of flow using the runoff-area method.
       The level of precision required in determining the flow should be consistent with being able to
       place the flow at the target in the appropriate range. These methods are detailed below.
Section 8.3
                                             232

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                                      HIGHLIGHT 8-21
                                SOURCES OF FLOW DATA
 Primary Source
      The Water Resources Data Annual Report,
      published for each state by USGS. This Report
      lists varous water quality and quantity
      parameters for each gauging station in the USGS
      network for the water year (October 1 -
      September 30)

 Secondary Sources

 •  National Water Data Exchange (NAWDEX) data
    base, maintained and admisistered by USGS
    Headquarters in Reston, VA, or NAWDEX
    Assistance Centers at the Water Resources
    Division district offices can help acquire data.

 •  EPA Regional STORE! data.

 •  Average Annual Runoff in the United States, 1951-
    80, published by USGS.

 •  Map of the Mean Annual Runoff for the
    Northeastern, Southwestern, and Mid-Atlantic
    United States, Water Years 1951-80, published by
    USGS.
Other Possible Sources

•  Federal Agencies

    USGS
    Army Corps of Engineers
    National Weather Service
    Forest Service
    Soil Conservation Service (SCS)
    Bureau of Land Management
    Bureau of Reclamation
    Bonneville Power Administration
    Tennessee Valley Authority

•  Canadian Agencies

    Inland Water Directorate, Water Resources
    Branch

•  State Agencies

    Departments of Water Resources
    Departments of Natural Resources
    Departments of Environmental Protection
    Water Control Boards

•  River Basin Commissions

    Susquehanna River Basin Commission
    Upper Colorado River Basin Commission

•  Non-profit Organizations

    Alliance for the Chesapeake Bay

•  Local Agencies and Organizations

    Departments of Health
    Municipal Water Authorities
    Electric Power Utilities
(4)     If applicable, evaluate short-term streamflow information. Estimating streamflow information
       is described \r\Highlight8-22.

(5)     Use estimate of flow to assign dilution weight to targets. Use MRS Table 4-13 to assign a
       dilution weight.

ESTIMATING FLOW

       When estimating flow,  first identify where gauging stations are located and determine which
methods are appropriate. In many instances, no gauging stations will be located near a target or
within the TDL, but one or more gauging stations may be found some distance upstream or
downstream from the target. In these cases, it may be possible to use interpolation or extrapolation to
                                              233
                                                                                        Section 8.3

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                                       HIGHLIGHT 8-22
                 EXTENDING SHORT-TERM STREAMFLOW RECORDS


            In some cases, short-term streamflow Information maybe available for fewer than five complete
    water years as required by the USGS for calculating "average because the years of record may have been
    unusually wet or dry and the mean may be skewed accordingly. A better approach Is to compare the
    mean flow calculated to a nearby gauging station which has a long-term data record. A ratio (DR,B) is
    calculated between the mean flow at the short-term station (QJ and the mean flow at the long-term
    station (QB) for the same years. The ratio Is then multiplied times the discharge from the long-term
    gauging  station for all years as follows:


                                                                   Discharge (cfs)

    A.       Available Data                                     Station A             Station B
            Water Year                                      (Short-term)           (Long-term)
1989
1988
1987
1986
1985
1984
Means for period of record;
Means for 87-89
94
85
95
—
—
-
91
91
188
176
195
219
233
220
205
186
    B.      Calculate ratio between mean discharges for Station A and Station B for the same period of
           record (87-89):

                          DRAB = QA / QB = 91 cfs /186 cfs = 0.49

    D.      Estimate the long-term corrected annual discharge at Station A using discharge ratio and data
           from Station B:

                          QA(84-89 Estr QB(84-89)xDRAB =205 cfs x 0.49 = 100 cfs
estimate the flow at the target. In other cases, it may not be possible to interpolate or extrapolate, but it
may possible to estimate the flow using downstream gauging stations or by the runoff-area method.

        When interpolating or extrapolating, follow these guidelines:

               Rivers or streams should have flows greater than 100 cfs when interpolating, and
               greater than 1,000 cfs when extrapolating.

               There should be no significant inflows from tributaries relative to the discharge in the
               main branch.

               Watershed should be fairly uniform  in  character and not be in an and or semi-arid region.

               No major lakes, dams, significant diversions, withdrawals, or other controls should be
               between the gauging stations and the  target areas.

               Area between gauging stations (not necessarily the entire watershed) should not be
               subject to significant variations in rainfall patterns.
Section 8.3                                       234

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In addition use the following guidelines when extrapolating:

              The gauging station should be as close to the target as possible.

              For downstream targets, the gauged discharge value of the station nearest to the target
              should be at the low to middle portion of the flow characteristics range listed in
              MRS Table 4-13; conversely, for upstream targets, the gauged discharge value should
              be at the middle to high portion of the range.

ESTIMATING FLOW BY INTERPOLATION

       When using interpolation to estimate flow at a target, the gauging stations generallyshould
not be located far apart. The maximum acceptable distance will depend on the characteristics of the
river or stream, the tributary inflows, and the characteristics of the watershed. Fora large river with  no
inflows equaling a significant percentage of the main flow, it may be possible to interpolate 50 miles or
more. For small streams, linear interpolation may only be valid for short distances.Highlight 8-23
provides an example of estimating flow using interpolation.

(1)     Identify two gauging stations. One gauging station should be upstream (station A) and the
       other downstream (station B) of the target.

(2)     Using MRS Table 4-13, determine the assigned dilution weight for each gauging station.

              If the dilution weights are the same for station A and station B, document that the annual
              discharge values yield the  same dilution weight in MRS Table 4-13, and assign that
              dilution weight to the target.

              If the dilution weights are different, proceed to Step (3).

(3)     Perform linear Interpolation. In more complex cases, there is a change in the assigned
       dilution weight from station A to station B. If the size of the river or stream is much larger than
       the size of any tributary inflows (e.g., a 0h order stream with 1st and 2nd order tributaries) and
       the watershed  between the two stations is uniform (e.g., the tributary inflows are about equal
       in magnitude and uniformly distributed along the length of the stream segment between the
       two stations), it may be possible to perform a linear interpolation.

              Determine the incremental discharge. Subtract the average annual discharge of the
              upstream station, QA (in cfs), from the downstream station, QB, to determine what is
              known as the incremental discharge, Q.

                                          Q, = QB - QA

              Calculate a  change in discharge per unit length. Divide the incremental discharge by
              the length of the stream segment from station A to station B, LAB (units of length may
              be chosen as needed, but  use the same units throughout), to yield a change in
              discharge per unit length, QX.

                                         Qx = QI / LAB

              Calculate the estimated discharge at the target. Multiply the change in discharge per
              unit length, Qx, times the distance from the upstream station A (in the same units
              used for LAB) to the target of concern, LAT, and add the result to the discharge at
              station A, QA, to yield the estimated discharge at the target, Q^est).

                                    QT(est.) = (Qx x LAT) + QA
                                             235                                      Section 8.3

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                                        HIGHLIGHT 8-23
                 ESTIMATING TARGET FLOW USING INTERPOLATION
              -Station A: 8,000 ds
                             Station B: %
(SourceJ-.    .Target Location   12.000 cfs'

       _AjE___^____—

1.UU


   A site is located in a mixed use suburban community, in close proximity to a river.  The river is subject to
   potential contamination, and the PPE for hazardous substances has been identified. The river is not subject
   to tidally influenced waters.

   In order to evaluate a target subject to potential contamination, a dilution weight must be assigned to the target.
   Because there is no gauging station located at or in close proximity to the target, the flow rate at the target
   must be estimated.  Existing conditions (e.g., there are no significant inflows from tributaries relative to the
   discharge in the main branch) allow for the interpolation method to be used.

   (1)      Identify two gauging stations—one upstream (station A) and one downstream (station B) of the
           target.

           Station A —  QA = 8,000 cfs
           Station B —  QB = 12,000 cfs

   (2)      Using HRS  Table 4-13, determine the assigned dilution weight for each gauging station.

           Station A =  0.001
           Station B =  0.0001

           Because the dilution weights are different, proceed to Step (3).

   (3)      Perform linear interpolation.

           •       Determine the incremental discharge.
                   Q!  =  12,000 cfs -  8,000 cfs = 4,000 cfs

           •       Calculate a discharge per unit length.
                   QL = 4,000 cfs / 25 ml = 160 cfs/mi

           •       Calculate the estimated discharge at the target.
                   QT(est.) =  (160 cfs/mi x 15 mi) + 8,000 cfs = 10,400 cfs

           •       Using HRS Table 4-13, assign a dilution weight to the target based on the estimated flow for
                   the target, 10,400  cfs.  The dilution weight for the target is 0.0001.
Section 8.3
                                                  236

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ESTIMATING FLOW BY EXTRAPOLATION

       If two gauging stations are located either upstream or downstream from the target, an estimate
of flow at the target can be obtained by extrapolation, as described below.

(1)     Identify the nearest gauging station upstream or downstream of the target.

              If this gauging station is located relatively close to a target, assign the dilution weight
              that corresponds to the gauged flow to the target.

              If this gauging station is located too great a distance from the target to allow
              confidence in using this method, proceed to Step (2).

(2)     Perform linear extrapolation. This method may be used in situations where a target is located
       in a river or stream in which two gauging stations (C and D) are located on a river or
       stream segment that does not include the target area. The  linear extrapolation method uses
       the linear interpolation calculation described above to estimate a rate of change for the
       discharge in the segment of the river or stream bounded by stations C and D, and then
       assumes that the rate of change is constant from the nearest station to the target.

              Identify two gauging stations, both either upstream or downstream of the target.

              Calculate a change in discharge per unit length (Q), as discussed for the interpolation
              method.

              Calculate the estimated discharge at the target. Multiply the change in discharge per unit
              length, Qx, times the distance from the target to the nearest gauging station, L^
               or LCT, to yield an estimated incremental discharge value.

              —      If the target is located downstream from the nearest gauging station, the
                      estimated incremental discharge value is added to the gauged discharge
                      value for the nearest station.

                                   QT(est.) = QD + (Qx x LDT)

              —      If the target is located upstream from the nearest station, the estimated
                      incremental discharge value is subtracted from the gauged discharge value for
                     the nearest station.

                                   QT(est.) = Qc - (Qx x LCT)

ESTIMATING FLOW USING ONE DOWNSTREAM GAUGING STATION

       In some instances, only one gauging station is present on a river or stream,  but at some
distance from a target.  In these cases, it may be possible to extrapolate the flow data to the target
location. However, this technique should be applied only over relatively short distances since there is no
way to estimate the rate of change of the discharge between the gauging station and the target.

       To use this method, the flow at target locations is set equal to the flow at a downstream gauging
station, as long as the flow at the target will not exceed this value. This approach is acceptable  because
it will not underestimate the actual flow and thus, overestimate target values.

ESTIMATING FLOW FOR UNGAUGED WATERSHEDS

       Some rivers or streams may not have gauging stations.  To estimate the average flow in an
ungauged river or stream, use the runoff-area method described below.
                                             237                                     Section 8.3

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(1)     Draw the watershed boundaries for the point In the stream where the flow Is to be map
       estimated on the topographic map. The scale of the map to be used will depend on the size of
       the watershed to be measured. The 7.5 minute (1:24,000) topographic maps can be used for
       small watersheds (e.g., less than 25 miles), especially if they fit on one or two adjacent map
       sheets. For larger watersheds or elongated watersheds spanning several map sheets, a larger
       scale such as 1:50,000 or 1:100,000 should be used.  Maps with scales greater than 1:250,000
       should be avoided because the resolution of the topographic lines is too crude to estimate
       boundaries correctly.

(2)     If there are multiple targets, delineate the additional downstream watershed area for the
       farthest downstream target area. If, after advancing  through this procedure, it is found that a
       change in the dilution weighting factor occurs somewhere upstream of the last target, estimate
       where the transition may occur, delineate the watershed for the point, and then estimate flow at
       that point. The best place to look for transitions is where a major tributary meets the stream.

(3)     For each watershed delineated, determine the enclosed area This may  be done by any of
       several methods including using a planimeter, counting squares, weighing paper, or digitizing the
       boundaries with a CAD or CIS system, The area should be expressed in units of square miles.

(4)     Select gauging stations using the following guidelines.

              The gauged watersheds should be as close to the ungauged watershed as possible.

              The gauged watersheds should be of a similar character in terms of topography,
              precipitation, and land use.

              The gauged watersheds should be approximately the same size as the ungauged
              watershed area.

(5)     Divide the "average flow" value (Qgauge, in cfs) for each selected station by the "drainage
       area" (Agauge, In mi2) to derive a flow per unit area parameter, Rgauge(ln cfs/mi2).

                                     "^gauge ~~ Agauge ' Agauge

               If any value varies from the others by more than 25 percent, examine the watershed
              that it drains and try to determine whether the  station is actually representative of the
              ungauged area.

              Average the Rgauge values of the selected stations to yield a regional unit flow value
              P
              ^region-

              Another procedure to obtain F^egion is to use average annual runoff maps, such as the
              Average Annual Runoff in the United States, 1951-80, which is published  by the  USGS,
              to calculate an estimate of a regional unit flow value. The map displays the U.S. with
              contour lines of equal average runoff. If the drainage area under investigation is in an
              area on the map that exhibits little variation in  runoff, it may be possible to visually
              estimate an  average runoff value. This average annual runoff value in  inches can then
              be converted to flow per square mile (cfs/mi2)  by multiplying it by 0.07362.

(6)     For each ungauged flow point to be estimated, multiply the regional unit flow value times
       the watershed area determined for that point.

                                          Q= R    Y A
                                       target  "Vegion A "target


Section 8.3                                      238

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EVALUATING TARGETS IN MULTIPLE WATER BODY CATEGORIES

       Some targets in the surface water pathway (i.e., wetlands, other sensitive environments,
 fisheries) may span more than one water body category. The steps below describe how to evaluate
such targets. Highlight 8-24 provides an example of evaluating targets in two dilution weight
categories.

(1)     For listed sensitive environments, identify all dilution weights applicable to the water
       bodies in which the sensitive environment is located. Choose the dilution weight that
       results in the highest target value for that sensitive environment. .

(2)     For wetlands and fisheries, determine where the breakpoint(s) between the surface
       waters and/or water body categories occur.

              Divide the wetland or fishery into two or more portions, based on the breakpoints
              determined above.

              Evaluate each portion as a separate wetland or fishery, applying the appropriate
              dilution weight from MRS Table 4-13.

DETERMINING SALINITY CATEGORY OF WATER BODY

       The use of certain reference data to score bioaccumulation potential, ecosystem
bioaccumulation potential, and ecosystem toxicity, and to select ecological-based benchmarks
depends  on the salinity of the water body in which targets are located. Most lakes and portions of
rivers are fresh water, and oceans and most portions of coastal tidal waters are saltwater. In tidally
influenced waters (and certain non-tidally influenced waters), determining which data to use may be
complicated by the presence of water of relatively low salinity, known as brackish water.

(1)     Gather the following Information about the surface water bodies within the TDL, as
       necessary and available:

              Average tidal cycle salinity;
              Average tidal cycle chloride concentration; and
              Presence of certain aquatic organisms.

(2)     Determine if targets are  located In fresh water, salt water, and/or brackish water.

              If data on salinity  or chloride concentration are available, use the definitions given at the
              beginning of this section to classify the water body,

              If no data are available, contact a state or Federal agency representative (e.g., National
              Marine Fishery Service (NMFS) personnel) or a recognized expert to provide a judgment
              based on the presence or absence of "indicator" species. Certain species are sensitive to
              salinity, and their  presence may indicate fresh water. The same is true for some species
              that only inhabit salt water. In addition,  assemblages of species are indicative of salinity
              gradients. Documenting salinity by use of indicator species should be supported by either
              a professional's statement or by scientific literature confirming the correlation of the
              indicator species with the water body's salinity.

              If no data or professional judgment regarding indicator species are available, assume
              that the portion of the river from the mouth upstream to the extent of salt water intrusion
              is brackish, all areas upstream  from this point are fresh water, and all coastal tidal waters
              are salt water.
                                             239                                      Section 8.3

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Station A: 800 oh Station B: 1,100 dt
y | Source t.pr[. Breakpoint -^^ \
Flow »'

^TDL

                                       HIGHLIGHT 8-24
          SCORING TARGETS  IN TWO DILUTION WEIGHT CATEGORIES
   The site is located adjacent to a stream. The two gauging stations located nearest the site are approximately
   5 miles upstream from the PPE (Station A) and approximately 16 miles downstream from the PPE (Station B).
   Annual average discharge for these stations is as follows:

                  Station A: 800 cfs
                  Stations: 1,100 cfs

   Wetlands are adjacent to the stream beginning at the PPE and continue for 17 miles. The entire wetland is a
   critical habitat for a Federal designated endangered species.

   The TDL for this site includes water bodies in two different flow categories. To evaluate targets correctly, you
   must determine the breakpoint in the flow categories, so that the appropriate dilution weights can be assigned.

   (1)      Determine the incremental flow between the two gauging stations  (Q() and then calculate the
           flow per unit length (QL).

           QI = 1,100 cfs - 800 cfs  = 300 cfs
           QL = 300 cfs/21 mi =  14.3 cfs/mi

   (2)      Determine breakpoint between dilution weight categories.

           800  cfs + (14.3 cfs/mi) (B mi)  = 1,000 cfs
           B = 200 cfs/14.3 cfs/mi = 14 mi
           Breakpoint is 14 mites  downstream from Station A, or 9 miles downstream of the PPE.

   (3)      Score targets.

           For  critical habitat, choose dilution weight that gives higher score (i.e., 0.01). Critical habitat for
           Federal designated endangered species receives value of 100 from HRS Table 4-23. Therefore,

                  Sensitive Environment Value = 100 x 0.01  = 1

           For wetland, divide the wetland into two parts, and score each segment separately:

                  Segment A: 9 mi frontage, dilution  weight = 0.01
                  Wetland Value = 250 x 0.01 = 2.5

                  Segment B:  6 mi frontage, dilution  weight = 0.001
                  Wetland Value = 150 x 0.001  = 0.15

           Potential Contamination Factor Value = 1/10 x [1 + 2.5 + 0.15] = 0.365
Section 8.3
                                                240

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(3)     Select appropriate reference data, based on salinity of water body at target locations.
       Determine the salinity category for each threat based on the location of targets (e.g., the food
       chain targets may be in salt water and the sensitive environment targets may be in fresh water).

               Select a bioaccumulation potential, ecosystem toxicity, and ecosystem bioaccumulation
               potential value (as needed) for the watershed.

                      If all targets for the threat are located in fresh water, use fresh water reference
                      data values to score the appropriate factor. If the applicable fresh water data for
                      the  hazardous substances being evaluated are not available, use salt water
                      (marine) reference data.

                      If all targets for the threat are located in salt water, use salt water reference data
                      values to score the appropriate factor. If the applicable salt water data for the
                      hazardous substances being evaluated are not available, use fresh water
                      reference data.

                      If some targets for the threat are located in fresh water and others are located in
                      saltwater, or if any targets are located in brackish water, select the applicable
                      reference data value that  results in the higher score for the appropriate factor.

               Select appropriate benchmarks for each  sensitive environment target subject to actual
               contamination.

                      If target being evaluated  is located in fresh water,  use the fresh water reference
                      data value to determine a benchmark. If applicable fresh water data for the
                      hazardous substances being evaluated are not available, use saltwater
                      reference data if available.

                      If the target being evaluated is located in salt water, use the salt water reference
                      data value to determine a benchmark. If applicable salt water data for the
                      hazardous substances being evaluated are not available, use fresh water
                      reference data if available.

                      If the target being evaluated is located in both fresh water and salt water, or if it
                      is located in brackish water, use  the lower of the fresh water or marine values to
                      determine the benchmark.

TIPS AND REMINDERS

       It may not be necessary to define precise  breakpoints between water body types unless
       important targets are located near the breakpoints.

       If the fresh and salt  water reference values are identical, do not spend significant  time
       documenting whether waters are fresh, brackish, and/or salt. However, if reference values differ
       for one or more of the factors, the distinction needs to be made.

       In the case of ecological-based benchmarks for sensitive environments subject to actual
       contamination, the use of the  lower  benchmark concentration results in the higher factor score.

       Score inland waters with high salinity due primarily to sodium chloride (e.g., Great Salt Lake,
       Salton Sea,  and saline water-draining salt beds)  as brackish waters. Score inland waters with
                                              241                                      Section 8.3

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       high salinity due primarily to salts other than sodium chloride (e.g., mineral springs, volcanic
       lakes, and playa lakes) as fresh water.

       If salinity for a water body varies significantly over time, determine water type based on the
       presence  of fresh and/or salt water indicator species.

       MRS dilution weights are assigned  based on order-of-magnitude ranges of flow or depth.
       Therefore, estimate flow or depth at a target with a degree of precision that places the flow or
       depth within one of these ranges.

       The SCS  often has flow data for small (10 to 50 cfs) streams that are not gauged.

       Before applying the runoff-area method, carefully consider the watershed especially in areas
       where runoff patterns are highly variable (e.g., the Southwest and Pacific Northwest).
Section 8.3                                      242

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SECTION  8.4
SURFACE WATER
CONTAINMENT FACTOR
                                                                                LR
       This section provides definitions for many of the terms used in the surface water containment
descriptions and explains how to score the containment factor in the surface water pathway. If an
observed release to a watershed cannot be established, then that watershed is evaluated based on
potential to release. Two factors are used to evaluate the potential to release factor: potential to release
by overland flow and potential to release by flood. The containment factor is a measure of the methods
(either natural or engineered) that have been used to restrict the release of hazardous substances from a
source to the watershed or to prevent released substances from entering surface water.

       Containment criteria have been compiled for several types of sources on a numerical scale
selected to provide a relative degree of discrimination among different levels of containment. MRS Table
4-2 includes containment factor rating descriptions for the following specific categories of hazardous
waste sources: surface impoundments, land treatment facilities, containers, and tanks. The table also
provides containment factor rating descriptions that apply to all other hazardous waste sources, including
landfills, piles, and contaminated soil.

       The containment factor is evaluated for each source for the watershed being evaluated, and the
highest containment factor value for any source that meets the minimum size requirement is assigned  as
the containment factor value. If none of the sources meets the minimum size requirement, the highest
containment factor value of any source is assigned.
                             RELEVANT MRS SECTIONS

        Section 4.1.2.1.2.1.1    Containment
        Section 4.1.2.1.2.2.1    Containment (flood)
        Section 4.1.2.1.2.2.2    Flood frequency
        Section 4.1.2.1.2.2.3    Calculation of factorvalue for potential to release by flood
        Section 4.1.2.1.2.3      Calculation of potential to release factorvalue
DEFINITIONS

       The following definitions elaborate on terms used in the containment descriptions in MRS Table
4-2.
       Above-ground Tank: Any tank that does not meet the definition of a below-ground tank
       (including any tank that is only partially below the surface).

       Associated Containment Structures:  As used in MRS Table 4-2, constructed barriers (e.g.,
       liners, dikes, berms) that may have been placed under, over, or around a source (e.g., a landfill
       or a waste pile) to prevent the release of hazardous substances to the environment.
                                           243                                   Section 8.4

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Below-ground Tank:  A tank with its entire surface area below the surface and not visible; however, a
fraction of its associated piping may be above the surface.

Bulk Liquids:  Noncontainerized liquids deposited directly into a source by pipe, tanker truck or other
means of transport.

Essentially Impervious Base: A base underlying containers that is free from cracks and gaps and
prevents the penetration of leaks, spills, or precipitation.

Evidence of Hazardous Substance Migration: Chemical analyses and/or visual evidence that
demonstrate hazardous substances attributable to a source have migrated away from that source into the
surrounding soil, ground water, surface water, or air (e.g., leachate containing hazardous substances
coming out of the source; stained or contaminated soil that can be attributed to migration from the
source; evidence of overflow from a surface impoundment containing hazardous substances).

Free Liquids:  Liquids that readily separate from the solid portion of a substance under ambient
temperature and pressure.

Freeboard: Vertical distance between the top of a tank or surface impoundment dike and  the surface of
the hazardous substance contained therein. Freeboard is intended to prevent overtopping resulting from
normal or abnormal operations, wind and wave action, rainfall, and/or run-on.

Land Treatment Zone: Soil area in the unsaturated zone of a land treatment unit within which
hazardous substances are intended to be degraded, transformed, or immobilized.

Liner: A continuous barrier that covers all the earth likely to be in contact with a source so that
hazardous substances or leachate containing hazardous substances would not migrate to  the
surrounding earth. The barrier may be synthetic material (e.g., a thick, continuous, polyethylene
membrane) or engineered, compacted natural,  material (e.g., re-worked and low permeability clay). An
in-situ clay layer that has not been re-engineered  by compaction or  other methods is not considered a
liner.

Maintained Engineered Cover:  Vegetated cover, usually made of  compacted clean soil.  It is generally
placed over a source at its closure and  is designed and constructed to minimize the migration of liquids
through the closed source, function with minimum maintenance, and accommodate settling and
subsidence. Maintenance of the integrity and effectiveness of the final cover may include repairing the
cap as necessary to correct  the effects of settling, subsidence, erosion, and other events.

Run-on Control/Runoff Management System, Functioning and Maintained: A functioning and
maintained, engineered system or structure designed to prevent flow into or onto a source or,
alternatively, to control runoff from a source and prevent hazardous substance migration.

Secondary Containment:  As used in MRS Table 4-2, secondary containment is applicable to the
evaluation of the containment factor for tanks. Methods of secondary containment include  a liner
external to the tank, a vault,  a double-walled tank, or an equivalent device.

Tank and Ancillary Equipment:  Tanks and associated pipes, pumps, sumps, manifolds,  fittings,
flanges, and valves used to  distribute, meter, or control flow of hazardous substances to or from the tank.
Section 8.4                                     244

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SCORING SURFACE WATER CONTAINMENT FOR OVERLAND FLOW

(1)     Identify the sources at the site. (See Section 4.1 for discussion of potential sources.) MRS
       section 1.1 defines a source as "any area where a hazardous substance has been deposited,
       stored, disposed, or placed, plus those soils that have become contaminated from migration of a
       hazardous substance." The MRS divides sources into five categories for evaluating ground water
       containment: surface impoundments, land treatment, containers, tanks, and all other sources.
       Each category has a separate list of criteria used to assign containment values.

(2)     Determine If one or more sources are located In surface water in the watershed being
       evaluated (e.g., intact sealed drums In surface water).

              If so, assign a containment factor value of 10 for that watershed.
              If not, continue to Step (3).

(3)     For each source within the watershed, determine whether the source hazardous waste
       quantity value is 0.5 or greater.

              Only sources with a source hazardous waste quantity value of 0.5 or greater can be used
              to assign the containment value, unless no source for the watershed being evaluated has
              a source hazardous waste quantity value of 0.5 or greater. This limitation is referred to
              as "minimum size requirement." Highlight 8-25 summarizes the measurements of
              sources that will  give  a source hazardous waste quantity value of 0.5. Any of the
              hazardous waste quantity tiers can be used to determine whether a source meets the
              minimum size requirement. Detailed  guidance on determining hazardous waste quantity
              values is provided in Chapters.

              If no source meets the minimum size requirement, evaluate containment for all sources.

(4)     Assign a containment value to each eligible source.

              Use the definitions provided above to interpret the containment criteria  in MRS Table
              4-2.

              Highlight 8-26 summarizes the information requirements to evaluate source
              containment.

(5)     Assign a containment factor value for the potential to release by overland  flow
       component for the watershed.

              Assign the highest containment value for those sources with hazardous waste quantity
              values greater than or equal to 0.5 as the containment  factor value for the watershed.

              If none  of the sources in the watershed being evaluated at the site has a source
              hazardous waste quantity value greater than or equal to 0.5, assign the highest
              containment factor value from all eligible sources for the watershed as the containment
              factor value for the watershed.

SCORING SURFACE WATER CONTAINMENT FOR FLOOD

       Assign the flood containment factor value as described below.

(1)     Identify the sources at the site. (See Section 4.1 for discussion of potential sources.)
                                           245                                    Section 8.4

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HIGHLIGHT 8-25
SOURCE MEASUREMENTS THAT MEET THE














MINIMUM SIZE REQUIREMENT

Tier
A
B
C

Volume





D

Area




Measure or Source Type
Hazardous constituent
quantity
Hazardous wastestream
quantity
Landfill
Surface impoundment
Surface impoundment
(buried/backfilled)
Drums
Tanks and containers
other than drums
Contaminated Soil
Pile
Other
Landfill
Surface impoundment
Surface impoundment
(buried/backfilled)
Land treatment
Pile
Contaminated soil
Minimum Measurements
for Hazardous Waste
Quantity Value of 0.5
0.5 pounds
2,500 pounds
1,250 cubic yards
1.25 cubic yards
1.25 cubic yards
250 gallons
1.25 cubic yards
1,250 cubic yards
1.25 cubic yards
1.25 cubic yards
1,700 square feet
6.50 square feet
6.50 square feet
135 square feet
6.50 square feet
17,000 square feet















(2)     Determine if each source meets the minimum size requirement.

              Only sources with a source hazardous waste quantity value of 0.5 or greater can be used
              to assign the containment value, unless no source for the watershed being evaluated has
              a source hazardous waste quantity value of 0.5 or greater.

              If no source  meets the minimum size requirement, evaluate containment for all sources.

(3)     Assign potential to release by flood factor value to each eligible source in the watershed.

              Determine the floodplain category in which the source (or portion of the source) lies.
Section 8.4
                                            246

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                                      HIGHLIGHT 8-26
             DATA NEEDS FOR EVALUATING SOURCE CONTAINMENT


 The following types of information is helpful for evaluating the containment factor:

         The physical location of the hazardous substance(s) (e.g., buried, impounded, in a below-ground
         tank).

         Evidence of hazardous substance migration (e.g., overflow from surface impoundments or stained
         soil).

         Evidence, or lack thereof, of diking, berms or other engineered physical barriers that completely
         surround the source area.

         The presence of bulk and/or free liquids.

         Evidence of liners that are continuous and that would prevent the source hazardous substance(s)
         from coming in contact with the earth beneath (or around) the source. In the case of liners, the site
         Investigator may assume that there is not a liner unless evidence indicates otherwise.

         Evidence, or lack thereof, of leachate collection systems (functioning or not), and ground water
         monitoring systems.

         Evidence of the existence and condition of physical structures that provide protection from
         precipitation, and/or run-on and runoff control.

 The above list Is illustrative in nature. It is meant neither to be all inclusive of the types of information that can
 be used to characterize the containment of any particular hazardous substance source nor to establish
 minimum requirements.
               Assign a floodplain frequency value (see MRS Table 4-9) for each applicable floodplain
               category.

               Assign a containment factor value (see MRS Table 4-8) for each floodplain category in
               which the source is located.

               Multiply the floodplain containment value by the floodplain flood frequency value for
               each floodplain in which the source  is located.

               Select the highest product as the source's  potential to release by flood factor value.

(4)     Assign the highest potential to release by flood factor value for the watershed from
       sources meeting the minimum size requirement.

               Assign the highest potential to release by flood factor value for those sources with
               hazardous waste quantity values greater than or equal to 0.5 as the factor value for this
               component of the surface water pathway.

               If none of the sources in the watershed being evaluated at the site has a hazardous
               waste quantity value  greater than or equal to 0.5, assign the highest potential to release
               by flood factor value  from all eligible sources for the watershed as the factor value for
               this component of the surface water pathway.


                                              247                                       Section 8.4

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TIPS AND REMINDERS

       Regardless of source type, if there is evidence of hazardous substance migration from the
       source, assign a containment factor value of 10 for the overland flow component for that
       watershed.

       Any hazardous waste quantity tier can be used to determine that a source meets the minimum
       size requirement.
Section 8.4                                    248

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SECTION 8.5
OVERVIEW OF ACTUAL
CONTAMINATION  FOR ALL
THREE THREATS
       This section provides guidance on establishing actual contamination in the surface water
migration pathway for the drinking water, human food chain, and environmental threats. This section
presents a summary table of sample types that can be used in each of the three threats. Detailed
guidance for each threat is contained in subsequent sections of this chapter.

       In evaluating the surface water migration pathway, a water body is subject to actual
contamination if it meets specific criteria that demonstrate that hazardous substances attributable to the
site have migrated to targets for the water body. Additional criteria apply for the human food chain threat
(see Sections 8.12 and 8.13). Surface water bodies subject to actual contamination are classified as
being subject to either Level I or Level II concentrations. Several targets factors receive higher weighting
when surface water bodies are subject to actual contamination. Targets not subject to actual
contamination are evaluated based on potential contamination.Highlight 8-27 summarizes the
requirements for establishing actual contamination of a surface water body.  Sections on each threat
within the surface water pathway provide details on how to determine the level of contamination.
        Section 2.3
        Section 2.5
        Section 2.5.1

        Section 2.5.2
        Section 4.1.1.2
        Section 4.1.2.1.1
        Section 4.1.2.3
        Section 4.1.3.3
        Section 4.1.4.3
RELEVANT MRS SECTIONS
  Likelihood of release
  Targets
  Determination of level of actual contamination at a sampling
  location
  Comparison to benchmarks
  Target distance limit
  Observed release
  Drinking water threat - targets
  Human food chain threat - targets
  Environmental threat - targets

DEFINITIONS
       Actual Contamination for the Surface Water Pathway: A portion of a surface water body is
       subject to actual contamination if it meets the criteria for an observed release. Sampling data
       from aqueous, sediment, or essentially sessile, benthic organisms may be used to establish
       actual contamination. However, the requirements for establishing actual contamination vary by
       threat.

       Level I Concentration for the Surface Water Pathway: Level I concentrations are established
       in samples in which the concentration of a hazardous substance that meets the criteria for an
       observed release is  at or above  its specific health-based benchmark for the
                                         249
                                                                               Section 8.5

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surface water threats, with certain exceptions for the human food chain threat. Targets also may be
subject to Level I concentrations if multiple hazardous substances that meet the criteria for an observed
release are present below their respective benchmarks and the I  or J index is greater than or equal to
one. Benchmarks for the surface water pathway include MCLs, non-zero MCLGs, Food and Drug
Administration Advisory Levels (FDAAL) for fish or shellfish, ambient water quality criteria (AWQC) for
protection of aquatic life, ambient aquatic life advisory concentrations (AALAC), and screening
concentrations for cancer and chronic noncancer effects.

Level II Concentration for the Surface Water Pathway:  Level II concentrations are established in
samples in which the concentration of at least one hazardous substance meets the criteria for an
observed release, but the conditions for Level I concentrations are not met, with certain exceptions for
the food chain threat. In addition, Level II is assigned for observed releases established by direct
observation.

Observed Release: An observed release is established for the ground  water, surface water, or air
migration pathway either by chemical analysis or by direct observation. Observed release is not relevant
to the MRS soil exposure pathway. The minimum requirements for establishing an observed release by
chemical analysis are analytical data demonstrating the presence of a hazardous substance in the
medium significantly above background level, and information that some portion of that increase is
attributable to the site. The minimum criterion for establishing an  observed release by direct observation
is evidence that the hazardous substance was placed into or has been seen entering the medium.
Section 8.5                                     250

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                                                       HIGHLIGHT 8-27
             SAMPLES AND CRITERIA FOR LEVEL I AND LEVEL II CONCENTRATIONS BY THREAT3
Sample Type II Drinking Water Threat
Human Food Chain
Threat
Environmental Threat
Level 1
Surface Water
Bethnic or
Other Tissue
Sediment
[C]b must meet criteria for
an observed release and be
at or above concentrations
corresponding to:
• Non-zero MCLG,
• MCL,
• Oral 10"6 cancer risk
level,
or
• Oral RfD.
Cannot be used to establish
Level I.
Cannot be used to establish
Level I.
Cannot be used to
establish Level I.
[C]bc must meet criteria
for an observed release
and be at or above
concentrations
corresponding to:
• FDAAL for fish or
shellfish,
• Oral 10"6 cancer risk
level, or
• Oral Rfd.
Cannot be used to
establish Level I
[C]b must meet criteria
for an observed release
and be at or above
concentrations
corresponding to:
• AWQC for protection
of aquatic life, or
• AALAC.
Cannot be used to
establish Level I.
Cannot be used to
establish Level I.
Level II '
Surface Water
Bethnic or
Other Tissue
Sediment
[C] must meet criteria for an
observed release.
[C] must meet criteria for an
observed release.
[C] must meet criteria for an
observed release.
[C]ef must meet criteria
for an observed release.
[C]c must meet criteria
for an observed release.
[C]ef must meet criteria
for an observed release.
[C] must meet criteria for
an observed release.
[C] must meet criteria for
an observed release.
[C] must meet criteria for
an observed release.
     a Only those drinking water intakes, portions of fisheries, and portions of wetlands within the boundaries of Level I or Level II contamination are
considered subject to such contamination. However, ifany_ portion of a sensitive environment other than a wetland is subject to Level I or Level II
contamination, the entire sensitive environment is evaluated as that level of contamination.
      b[C] refers to the concentration of a hazardous substance in a sample. Only one of the listed benchmarks needs to be equalled or exceeded by
this concentration for Level I to be established (or, for multiple substances, the I or J index needs to exceed 1).
     0 Concentrations of hazardous substances must be measured in a sample from an essentially sessile benthic human food chain organism from
the watershed or in a tissue sample from an organism (1) taken from a location within the boundaries of the actual food chain contamination and (2) from
a species of human food chain organism that spends extended periods of time within the boundaries of the actual food chain contamination but is not an
essentially sessile benthic organism. Hazardous substances in this latter type of tissue sample do not need to meet the criteria for an observed release
but must meet the criteria for actual food chain contamination In a surface water, benthic, or sediment sample.
     d Level II contamination in all threats also is established by an observed release by direct observation.
     e The hazardous substance  also must have a bioaccumulation potential factor value greater than or equal to 500, with certain exceptions for a
closed fishery.
     f A fishery also may be considered subject to Level 11  contamination if the fishery is closed, a hazardous substance for which the fishery has
been closed has been documented In an observed release to the watershed from the site, and at least a portion of the fishery is within the boundaries of
the observed release. The bioaccumulation potential factor value greater than or equal to 500 does not apply in this case.
                                                                251
                                                                                                                            Section 8.5

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SECTION  8.6
EFFICIENCY OF SCORING
THE  DRINKING WATER
THREAT
                                                        LR
we
       The drinking water threat is one of three threats used to evaluate the surface water pathway; the
other two are the human food chain threat and the environmental threat. The drinking water threat for
each watershed is evaluated based on three factor categories: likelihood of release, waste
characteristics, and targets. The drinking water threat targets factor category reflects the human
population and resources potentially at risk from exposure to hazardous substances in the surface water.
Three factors are used to evaluate drinking water threat targets: nearest intake, population, and
resources. Populations and intakes actually exposed to contaminated drinking water are weighted more
heavily than those potentially exposed.

       This section provides guidance for estimating the score that can be expected from the drinking
water threat before the detailed scoring and documentation process begins. This is done by presenting
look-up tables that provide rough estimates of drinking water threat scores based on estimates for the
likelihood of release, waste characteristics, and population factors. Such a determination may already
have been made during the PA and/or SI. This section provides guidance on how to estimate the
drinking water threat score when a single water body is present. If more than one water body  is present
within the watershed, the scorer should estimate the score of the water body with the greatest population
served by drinking water intakes to determine the efficiency of scoring this threat. However, this method
may underestimate the actual drinking water threat. This section is intended to be  used as a general
guideline and not as an absolute determination of whether to score the drinking water threat.

DEFINITIONS

       Actual Contamination for a Drinking Water Intake: A drinking water intake is subject to actual
       contamination if it is located in a  portion of a surface water body that meets the criteria for an
       observed release.

       Dilution Weight: A unitless parameter that adjusts the assigned point value for certain targets
       subject to  potential contamination as a function of the flow or depth of the water body at the
       target.

       Target Distance Limit (TDL) for the Surface Water Migration Pathway: Distance over which
       the in-water segment of the hazardous substance migration path is evaluated. The TDL extends
       15 miles from the PPE in the direction of flow (or radially in lakes, oceans,  or coastal tidal
       waters) or to the most distant sample point establishing an observed release, whichever is
       greater. In tidally influenced surface water bodies, an upstream TDL is also determined. For
       some sites (e.g., sites with multiple PPEs), an overall target distance of greater than 15 miles
       may result.

ESTIMATING ACTUAL CONTAMINATION

       Score the  drinking water threat whenever a drinking water intake is considered subeect to actual
contamination (i.e., Level I or Level II concentrations'). Because populations and nearest intake subject
to actual contamination receive higher weight and higher scores, respectively, than those
                                          253
                                                                                Section 8.6

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subject to potential contamination, the drinking water threat score based on actual contamination may be
sufficient for NPL consideration. Highlight 8-28 provides an analysis of approximate drinking water
threat scores obtained when intakes are subject to actual contamination. If intakes subject to potential
contamination are also present, consider whether documenting the population served by these additional
intakes will significantly affect the pathway score. At a minimum, discuss the presence of intakes subject
to potential contamination in the documentation record even if they are not scored.

ESTIMATING POTENTIAL CONTAMINATION
       Many factors must be scored when evaluating the drinking water threat based on potential
contamination. This section provides a step-wise procedure and look-up tables that can be used to
estimate the drinking water threat score for a site before beginning the detailed documentation process.
If a preliminary score has been developed for the site during the PA or SI, many of the estimates in the
steps below will already have been made In this case, proceed to Step (3).

(1)     Estimate the waste characteristics factor category value.The waste characteristics factor
       category value generally will not vary significantly among the  migration pathways (except for the
       human food chain threat and environmental threat). If you have already determined the waste
       characteristics factor category value for the ground water pathway (or any other migration
       pathway), use it to approximate the value (although the drinking water threat waste
       characteristics are based on toxicity/persistence rather than toxicity/mobility). Note that if the
       drinking water threat is actually scored, waste characteristics  must be determined as outlined in
       MRS sections 4.1.2.2 and 4.2.2.2 (i.e., do not use any estimated values for actual MRS scoring).
HIGHLIGHT 8-28
APPROXIMATE DRINKING WATER THREAT SCORES









FOR POPULATION SUBJECT TO ACTUAL CONTAMINATION a
Contamina-
tion Type
Level I




Level II




Likelihood
of
Release
550




550




Nearest
Intake
50




45




Waste
Charac-
teristics
100
56
32
18
10
100
56
32
18
10
Population Served by Intake(s)
1 5 10 25 50 100 250 500
43 70 100 100 100 100 100 100
24 39 58 100 100 100 100 100
14 22 33 65 100 100 100 100
8 13 19 37 67 100 100 100
4 7 10 20 37 70 100 100
34 37 40 50 67 100 100 100
19 21 22 28 37 56 100 100
11 12 13 16 21 32 64 100
6 7 7 9 12 18 36 66
3445 7 10 20 37
3 These drinking water threat scores are rounded to the nearest integer and assume a resources factor value equal to
Likelihood of Release Is assigned a value of 550 If an observed release to surface water can be established.








5.
Section 8.6
                                             254

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(2)     Determine the type of surface water body and, If appropriate, estimate the flow (or depth).
       The targets factor value for intakes subject to potential contamination is derived using dilution
       weights based on the flow or depth at the intake. If available, use actual flow and/or depth data.
       If data for flow are not readily available, estimate the flow according to instructions in Section 8.3
       of this guidance. After an estimate for flow and/or depth is obtained, use MRS Table 4-13 to
       determine the water body type and the appropriate dilution weight.

(3)     Estimate the population served by drinking water Intakes subject to potential
       contamination within the TDL. Determine the approximate number of people with sufficient
       accuracy to determine the population range category (from MRS Table 4-14) for all intakes
       subject to potential contamination within the TDL. Section  3.6.2 of EPA's Guidance for
       Performing Preliminary Assessments (OSWER Publication 9345.0-01 A, September 1991)
       provides guidance on obtaining population counts for each intake.

(4)     Determine approximate maximum drinking water threat score for a single water body In
       the watershed. Use the table in Highlight 8-29 to determine the approximate maximum
       drinking water threat score for the water body. As a first approximation, assume a likelihood
       of release factor category value of 550 (there can be an observed release without actual
       contamination of targets). The resultant threat score may indicate whether it is worthwhile to
       score the drinking water threat.  Note that the watershed score  requires combining scores
       from all water bodies in the watershed and could be significantly higher than a score based
       on a single water body. If it appears to be efficient to score the drinking water threat, proceed
       to Step (5). If a very low score is obtained even assuming  maximum likelihood of release,
       then documenting potential drinking water contamination is probably not an  efficient use of
       scoring resources, unless those few points will be important to the total site score.  If not, stop
       here.

(5)     Estimate the likelihood of release factor category value. Likelihood of release consists of
       observed release and two types of potential to release:  potential to release by overland flow,
       and potential to release by flood. The value for potential to release by overland flow is
       calculated based on three factors:  containment, runoff, and distance  to surface water. The
       value for potential to release by flood is calculated based on two factors: containment (flood)
       and flood frequency. The values assigned to the watershed for potential to release by
       overland flow and potential to release by flood are summed, and this sum is assigned as the
       likelihood of release value, with a maximum value of 500. Section 3.6 of EPA's Guidance  for
       Performing Preliminary Assessments (OSWER Publication 9345.0-01 A, September 1991)
       provides information on estimating a value for likelihood of release.

(6)     Determine the approximate drinking water threat score. Using the value  estimated for
       likelihood of release in Step (5), determine the approximate drinking water threat score for this
       water body by using the table \r\Highlight8-29, based on  the population estimated in Step (3).
       Because the scores in the table \r\Highlight8-29 include the nearest intake and resources factor
       values, scores for intakes on two different water body types cannot be added to get a pathway
       score. (Adding them would result in double counting the nearest intake and resources factor
       values.)

       Highlight 8-30 provides an example of how to use the table in Highlight 8-29.
                                             255                                      Section 8.6

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HIGHLIGHT 8-29
APPROXIMATE DRINKING WATER THREAT SCORES
















FOR POPULATION SUBJECT TO POTENTIAL CONTAMINATION a
Likeli-
hood of
Release
550°









400






Waste
Char.
100



56



32



100



56



Water BodyType"
minimal stream
3-mile mixing zone
small to moderate
steam
all other water
bodiesd
minimal stream
3-mile mixing zone
small to moderate
steam
all other water
bodiesd
minimal stream
3-mile mixing zone
small to moderate
steam
all other water
bodiesd
minimal stream
3-mile mixing zone
small to moderate
steam
all other water
bodiesd
minimal stream
3-mile mixing zone
small to moderate
steam
all other water
bodiesd
Popuation Served by Intake(s)
31- 101- 301- 1,001- 3,001- 10,001- 30,001-
100 300 1,000 3,000 10,000 30,000 100,000
20 28 51 100 100 100 100
12 15 27 64 100 100 100
5 6 8 16 39 100 100
444 5 7 14 38e
11 15 29 70 100 100 100
7 9 15 36 100 100 100
335 9 22 64 100
2 2 2 3 4 8 21e
6 9 16 40 100 100 100
4 5 9 21 59 100 100
223 5 13 36 100
111 1 2 5 12e
15 20 37 91 100 100 100
9 11 20 47 100 100 100
4 4 6 11 29 82 100
333 3 5 10 28e
8 11 21 51 100 100 100
5 6 11 26 75 100 100
223 6 16 46 100
1 1 2 2 3 6 16e
(Continued on next page)
















Section 8.6
                                                     256

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HIGHLIGHT 8-29 (continued)
APPROXIMATE DRINKING WATER THREAT SCORES
FOR POPULATION SUBJECT TO POTENTIAL CONTAMINATION a
Likeli-
hood of
Release

300


Waste
Char.
32
100
56
32
Water Body
Typeb
minimal stream
3-mile mixing zone
small to moderate
stream
all other water
bodiesd
minimal stream
3-mile mixing zone
small to moderate
stream
all other water
bodiesd
minimal stream
3-mile mixing zone
small to moderate
stream
all other water
bodiesd
minimal stream
3-mile mixing zone
small to moderate
stream
all other water
bodiesd
aThese drinking water threat scores as
nearest Intake factor, Consequently, scores from
different water body types.
b All water bodies with a dilution weigh
water bodies." The drinking water threat scores i
category, but the scores of the larger water bodie
will serve as a useful approximation for all water
0 Note that it is possible to score an ob
potential contamination.
d Lakes with flow characteristics simila
three water body types.
e These drinking water threat scores w
stream.
Population Served by Intake(s)
31- 101- 301- 1,001- 3,001- 10,001- 30,001-
100 300 1,000 3,000 10,000 30,000 100,000
5 6 12 29 85 100 100
3 4 6 15 43 100 100
1124 9 26 82
1111 2 3 9e
11 15 28 68 100 100 100
7 8 15 35 75 100 100
3 3 4 8 21 62 100
2223 4 8 21e
6 8 16 38 100 100 100
4 5 8 20 56 100 100
2225 12 35 100
11112 4 12e
3 5 9 22 64 100 100
2 3 5 11 32 97 100
1113 7 20 61
1111 1 2 T
sume a resources factor value equal to 5 and incorporate the appropriate
this tablecannot be summed to provide an estimated score for intakes on
equal to or less than 0.01 are grouped together in the category "all other
T this grouped row are equal to that of the "moderate to large stream"
s are generally sufficiently close that the "all other water bodies" category
sodies included in the category (except where otherwise noted).
served release to a watershed but still have all targets scored under
r to the first three water body types would have values similar to the first
II be substantially lower for water bodies larger than a moderate to large
b
257
                                                Section 8.6

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                                       HIGHLIGHT 8-30
          EXAMPLE OF ESTIMATING DRINKING WATER THREAT SCORE

 Site Description:       The site is adjacent to surface water. Waste characteristics have been scored at 100.

 Water Body Type:      The hazardous substance migration path involves only one stream approximately 30
                       feet in width. Estimated flow is approximately 70 cfs, indicative of a "small to
                       moderate stream."

 Population Estimate:   Population served by all intakes along the stream is between 1,001 and 3,000. All
                       population is subject to potential contamination.

 Maximum Estimated
 Drinking Water
 Threat Score:          Given these parameters, the estimated maximum drinking water threat score for the
                       site Is 16 based on potential contamination. This score of 16 is assumes that the
                       likelihood of release Is scored at its maximum value (i.e., 550 points for an observed
                       release).  If scoring the drinking water threat would appear to affect the site score
                       significantly, then the actual likelihood of release would be estimated in order to
                       arrive at a closer approximation of the drinking water threat score. If the stream had
                       been In the "moderate to large stream" category, the maximum drinking water threat
                       score would have been 5.
Section 8.6                                       258

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SECTION  8.7
ACTUAL CONTAMINATION
IN  THE DRINKING  WATER
THREAT
       A drinking water intake is subject to actual contamination if it meets specific criteria that
demonstrate that the intake has been contaminated with hazardous substances attributable to the site.
See Section 8.5 for general guidance on establishing actual contamination of targets in the surface water
pathway. All intakes subject to actual contamination are classified as Level I or Level II. Drinking water
intakes subject to actual contamination receive higher values for the nearest intake factor and higher
weight for the population factor than intakes subject to potential contamination. This section provides
guidance on differentiating between Level I and Level II contamination, including information on the
types of samples and health-based benchmarks that can be used. Information on scoring the drinking
water threat for sites with intakes subject to actual contamination is also provided in this section.
        Section 2.5
        Section 2.5.1

        Section 2.5.2
        Section 4.1.1.2
        Section 4.1.2.3
        Section 4.1.2.3.1
        Section 4.1.2.3.2
        Section 4.1.2.3.2.1
        Section 4.1.2.3.2.2
        Section 4.1.2.3.2.3
RELEVANT MRS SECTIONS

 Targets
 Determination of level of actual contamination at a sampling
 location
 Comparison to benchmarks
 Target distance limit
 Drinking water threat - targets
 Nearest intake
 Population
 Level of contamination
 Level I concentrations
 Level II concentrations
DEFINITIONS
       Actual Contamination for a Drinking Water Intake:  A drinking water intake is subject to
       actual contamination if it is located in a portion of a surface water body that meets the criteria for
       an observed release.

       Level II Concentrations for the Drinking Water Threat:  Level I concentrations are
       established in aqueous samples in which the concentration of a hazardous substance that meets
       the criteria  for an observed release is at or above  its drinking water benchmark. A drinking
       water intake also may be subject to Level I concentrations if multiple hazardous substances that
       meet the criteria for observed release are present below their respective benchmarks, and the I
       or J index is greater than or equal to one. Benchmarks for the drinking water threat include
       MCLGs, MCLs, and screening concentrations for cancer and chronic noncancer effects.

       Level II Concentrations for the Drinking Water Threat:  Level II concentrations are
       established in samples in which the concentration of at least one hazardous substance meets
                                          259
                                                                                Section 8.7

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       the criteria for an observed release, but the conditions for Level I concentrations are not met. In
       addition, Level II is assigned for observed releases established by direct observation.

       Nearest Intake Factor: Factor for evaluating the maximally exposed intake. This factor is
       based on the presence of actual contamination or, for watersheds where no intake is subject to
       actual contamination, the flow or depth of the water body at the intake nearest to the PPE within
       the TDL.

       Population for the Drinking Water Threat: Number of residents, students, and workers
       regularly served by surface water intakes that are located within the  TDL for the surface water
       bodies evaluated for a given watershed. This population does not include transient populations,
       such as hotel and  restaurant patrons, but may include seasonal populations (e.g., a resort area).

       Target Distance Limit (TDL) for the Surface Water Migration Pathway:  Distance over which
       the in-water segment of the hazardous substance migration path is evaluated. The TDL extends
       15 miles from the PPE in the direction of flow (or radially in  lakes, oceans, or coastal tidal
       waters) or to the most distant sample point establishing  an observed release, whichever is
       greater. In tidally influenced surface water bodies, an upstream TDL Is also determined. For
       some sites (e.g., sites with multiple  PPEs), an overall target distance of greater than 15 miles
       may  result.

ESTABLISHING ACTUAL CONTAMINATION FOR A DRINKING WATER
INTAKE

       The steps outlined below describe how to establish actual contamination for a drinking water
intake. These steps should be repeated for multiple hazardous substances and/or samples as necessary.

(1)     Determine if an observed release can be established by direct observation. If an observed
       release is established by direct observation, actual contamination of a drinking water intake  can
       be established only if the observation is made at the location of the drinking water intake. Direct
       observation cannot be used to  establish Level I  concentrations.

(2)     Identify sampling locations that can establish actual contamination for the intake based
       on chemical analysis. Surface water, sediment, or benthic samples taken at, or downstream
       from, a drinking water intake can be used to establish actual contamination for the intake. Select
       one hazardous substance in one of these samples and proceed to Step (3). If no such sampling
       locations are identified  and actual contamination is not established based on direct observation,
       score the intake based on potential contamination.

(3)     Determine the background level for the hazardous substance. Determine the appropriate
       background level (e.g., concentration from an appropriate background sample) for hazardous
       substances that could be naturally occurring, ubiquitous, or attributable to other sources in the
       area. A background level of 0 can be assumed for substances that are neither naturally
       occurring, ubiquitous, nor attributable to other sources in the areas (i.e., a background sample
       may  not be needed). See Section 5.1 for detailed information on determining the appropriate
       background level for comparison with a sample.

(4)     Determine whether the concentration of the hazardous substance is significantly above
       background. If yes, proceed to Step (5); if no, select another hazardous substance and/or
       sample and return to Step (3).  Detailed guidance for making this determination is found in
       Section 5.1, particularly Highlight 5-2.
Section 8.7                                    260

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(5)     Determine if the hazardous substance can be attributed to the site. If yes, actual
       contamination is established; if no, select another hazardous substance and/or sample and
       return to Step (3). Obtain sampling results or records (e.g., manifests) indicating the presence of
       the hazardous substance in a source at the site. Information that the hazardous substance was
       used at the facility also may be acceptable. See Sections 5.1 and 5.3 for additional guidance on
       attribution and transformation products.

DETERMINING LEVEL OF CONTAMINATION

       After identifying intakes within the TDL and establishing whether the intake is subject to actual
contamination, determine the level  of contamination for the intake. The steps outlined below describe
how to determine if the intake should be scored as Level I, Level II,  or potential contamination.

(1)     Determine whether actual contamination can be established for the surface water intake
       for any detected hazardous substance. Follow the guidance in the above section,
       Establishing Actual Contamination for a Drinking Water Intake. SeeHighlight 8-27 for a
       summary of the  types of samples and criteria used to establish the level of contamination for
       the drinking water threat.

              If actual contamination cannot be established for the intake (e.g.,  there is neither
              sampling data nor direct observation), score the  drinking water intake based on potential
              contamination.

              If actual contamination can be established for the intake, proceed to  Step (2).

(2)     Evaluate the level of contamination for the intake, based on the data  used to establish
       actual contamination at that intake.

              For sites that consist of contaminated sediments with an unknown source  evaluate all
              intakes subject to actual contamination as Level  II, regardless of the  surface water
              concentration of hazardous substances at an intake.

              If actual contamination is established by direct observation, evaluate the intake based
              on Level II concentrations.

              If actual contamination is established using only  sediment or benthic samples (i.e.,
              actual contamination cannot be established for that intake using surface water samples),
              evaluate the intake based on Level II concentrations.

              If actual contamination is established by surface  water samples, compare the
              concentration of each  hazardous substance that meets the observed release criteria with
              its appropriate health-based benchmark for surface water. SeeHighlight 8-31  for a list
              of applicable benchmarks.

              —      If the concentration of any hazardous substance that meets the observed release
                      criteria is greater than or equal to its benchmark, evaluate the intake based on
                      Level I concentrations.

              —      If no hazardous substance that meets the observed release criteria intake has an
                      applicable  health-based benchmark, evaluate the intake based on Level II
                      concentrations.

              —      If only one  hazardous substance meets the observed release criteria intake and
                      its concentration is less than  its benchmark, evaluate the  intake based on Level
                      II concentrations.
                                             261                                     Section 8.7

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                                     HIGHLIGHT 8-31
                BENCHMARKS FOR THE DRINKING WATER THREAT

        The following benchmarks apply to the drinking water threat. Values for specific hazardous substances
 are available in SCDM underthe health-based benchmarks section. For evaluating the drinking water threat.these
 benchmarks are applicable to surface water samples only (i.e., do not use with sediment or benthic samples).
 If several benchmarks are provided for a substance, choose the benchmark with the lowest concentration. For
 some hazardous substances, values are not available for all benchmarks.

             MCLG (use only values greater than 0).

             MCL.

             Screening concentration for  cancer,  corresponding to a 10?  individual cancer risk for oral
             exposures.

             Screening concentration for noncancer effects, corresponding to the RfD for oral exposures.

              —      If more than one hazardous substance meets the observed release criteria
                      intake and none of these substances exceeds its applicable benchmark,
                      continue to Step (3).

(3)     Calculate the I and J indices for all hazardous substances that meet the observed release
       criteria. Make two lists of substances that meet the observed release criteria: hazardous
       substances with screening concentrations for cancer risk, and hazardous substances with
       screening concentrations for noncancer effects. Each hazardous substance may be on one,
       neither, or both of the lists. If more than one sample has been taken, and these samples are
       comparable (e.g., taken in the same time frame, collected using the same field techniques,
       analyzed by the same methods), then for each  hazardous substance select the highest
       concentration to use in the calculations below.

              Calculate the I index for all hazardous substances with screening concentrations for
              cancer  risk that meet the observed release criteria, using the following equation:
       where: Cj  =   concentration of substance i in sample;
              SCj =   screening concentration for cancer risk for hazardous substance i; and
              n   =   number of hazardous substances that meet observed release criteria
                      and for which an SC is available.

              Calculate the J index all hazardous substances with screening concentrations for
              noncancer effects that meet the observed release criteria, using the following equation:
       where: Cj  =   concentration of substance j in sample;
              CRj  =  screening concentration for noncancer effects for hazardous
                      substance]; and
              m  =   number of hazardous substances that meet observed release criteria
                      and for which a CR is available.
Section 8.7                                     262

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              If either the I or J index is greater than or equal to 1, evaluate the drinking water intake
              based on Level I concentrations. If both the I and J indices are less than one, evaluate
              the surface water intake based on Level II concentrations.

SCORING INTAKES  SUBJECT TO ACTUAL CONTAMINATION

       The level of contamination must be determined to score the nearest intake and population
factors and may affect the minimum value for the hazardous waste quantity factor. Once the level of
contamination has been established for each intake within the TDL, score these targets as shown in
Highlight 8-32. Section 8.8 provides detailed instructions for scoring nearest intake and population
factors for intakes subject to actual contamination.
fc
HIGHLIGHT 8-32
COMPARISON OF SCORING LEVEL I, LEVEL II,
AND POTENTIAL CONTAMINATION
Level of
Contamination
Actual - Level I
Actual - Level II
Potential
Nearest intake
Factor Value
50
45
(dilution weight) x 20
Population Factor Value
10 x number of people
1 x number of people
0.1 x dilution-weighted
population
Minimum HWQ
Factor Value3
100
100
10b

a Minimum hazardous waste quantity factor values apply if Tier A is not adequately determined for all sources.
b May be 1 00 in certain cases when there has been a removal action; see MRS section 2.4.2.2 and EPA's removal policy
ct sheet.
 TIPS AND REMINDERS

       Actual contamination cannot be established without an observed release to surface water, but an
       observed release to surface water is not necessarily sufficient to document actual contamination
       of a drinking water intake.

       Benthic tissue and sediment samples cannot be used to establish Level I concentrations for the
       drinking water threat, but can be used to establish Level II concentrations. Only analytical data
       from surface water samples can be used to establish Level I concentrations.

       To use multiple hazardous substances to establish Level I concentrations using the I or J index,
       all hazardous substance concentrations must be from the same sample or comparable samples,
       Comparable samples are samples taken at essentially the same location and at essentially the
       same time, and analyzed by equivalent methods.

       The area of actual contamination  and the level of actual contamination within that area can vary
       for each of the three surface water threats.

       Intakes at sites that consist solely of contaminated sediments with an unknown source cannot be
       evaluated at Level I, regardless of surface water concentrations at the intake.
Section 8.7
                                            263

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SECTION 8.8
POPULATION  AND
NEAREST INTAKE
FACTORS
       The population factor in the drinking water threat evaluates the number of residents, students,
and workers regularly served by surface water intakes within the TDL for the watershed being evaluated.
This evaluation is essentially the same as that for the ground water pathway, except that surface water
intakes are considered instead of drinking water wells. This section also briefly discusses the nearest
intake factor.
                           RELEVANT MRS SECTIONS
        Section 4.1.1.2        Target distance limit
        Section 4.1.2.3.1       Nearest intake
        Section 4.1.2.3.2       Population
DEFINITIONS
       Dilution Weight: A unitless parameter that adjusts the assigned point value for certain targets
       subject to potential contamination as a function of the flow or depth of the water body at the
       target.

       Nearest Intake Factor: Factor for evaluating the maximally exposed intake. This factor is
       based on the presence of actual contamination or, for watersheds where no intake is subject to
       actual contamination, the flow or depth of the water body at the intake nearest to the PPE within
       the TDL.

       Population for the Drinking Water Threat:  Number of residents, students, and workers
       regularly served by surface water intakes that are located within the TDL for the surface water
       bodies evaluated for a given watershed. This population does not include transient populations,
       such as hotel and restaurant patrons, but may include seasonal populations (e.g., a resort area).

       Students: Full- or part-time attendees of an educational institution or day care facility that is
       served by an intake located within the TDL.

       Target Distance Limit (TOIL) for the Surface Water Migration Pathway: Distance over which
       the in-water segment of the hazardous substance migration path is evaluated. The TDL extends
       15 miles from the PPE in the direction of flow (or radially in lakes, oceans, or coastal tidal
       waters) or to the most distant sample point establishing an observed release, whichever is
       greater. In tidally influenced surface water bodies, an upstream TDL is also determined. For
       some sites (e.g., sites with multiple PPEs), an overall target distance of greater than 15 miles
       may result.
                                         265                                   Section 8.8

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       Workers: Permanent employees (part-time or full-time) of a facility or business that is served by
       an intake within the TDL.

EVALUATING THE DRINKING WATER POPULATION FACTOR

       The steps below describe an approach for estimating the population served by surface water
intakes located within the TDL. First, estimate the population served by municipal water systems with
intakes within the TDL. Contact municipal water authorities to obtain estimates of populations served.
The water authority should know whether the population served includes workers and students in addition
to residents. If the population estimate does not include workers and/or students, modify the
methodology presented below as necessary.Highlight 8-33 summarizes the information  needed to
obtain drinking water population estimates.
                                     HIGHLIGHT 8-33
            DATA NEEDS FOR DRINKING WATER THREAT POPULATION

 Obtain from Local, Municipal, or Other Water Authorities:

         Identification of all municipal surface water intakes located within the TDLs for surface water bodies in the
         watershed being evaluated;

         Number of persons saved or service connections for each intake that is not part of a blended system; and

         For intakes that are part of a blended system:

         —      Total population served or number of service connections;

         —     Total number of wells and intakes in the system (including those outside the TDL);

         —     Whether any wells or intakes are standby;

         —     Whether any well  or intakes provides mote than 40 percent of the system's water; and

         —     Average annual pumpage or capacity for each intake and well (only needed if one intake or well
               provides more than 40 percent of the systems's water).

 Obtain from Local, Municipal, or Other Water Authorities, or Local Health Agencies:

         Identification of private intakes located within the TDL; and

         Identification of schools and large businesses possibly served by intakes located within the TDL.

 Obtain from U.S. Bureau of Census Reports (or more recent source if appropriate):

         Average number of persons per residence for each county served by a system with intake located within
         the TDL.

 Obtain from Business and Schools:

         Information on how they obtain water; and

         Number of workers and/or  students.
Section 8.8                                     266

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       If the water authority can only provide the total number of connections, estimate the population
using the following process.

(1)     Identify all municipal systems with intakes within the TDL. Repeat Steps (2) through (4) for
       each system if more than one system has intakes within the TDL. If no municipal systems have
       intakes within the TDL, proceed to Step (5).

(2)     Identify all water supply units that are components of the municipal system.  These units
       may include surface water intakes, ground water wells, and standby intakes or wells. If the
       municipal system is a blended system, all water supply units- both within and outside of the TDL
       - must be identified.

(3)     Evaluate the population served by the municipal system, assuming all service
       connections are residential. This assumption may underestimate the target population
       because typically more people are served at a school or business than at a residence. However,
       if a high score is achieved assuming only residential connections, time-consuming inquiries to
       document student or worker populations may not be necessary.

              Identify locations of surface water intakes. Contact local water authorities to
              determine the locations of surface water intakes within the TDL and applicable blended
              intakes outside the TDL. Mark the locations on a map that includes the PPE and surface
              water sample collection points.

              Identify any Intakes contaminated at Level I or Level II. Section 8.7 provides
              instructions for identifying intakes subject to Level I and Level II concentrations. Keep a
              separate count of persons served by intakes that are subject to Level I concentrations,
              Level II concentrations, and  potential contamination.

              Estimate the flow or depth for the surface water body at each intake.  This
              information may be available from the water authority for major drinking water intakes. If
              flow at the intake has not been gauged, refer to Section 8.3 for guidance on estimating
              flow for each intake. Flow (or for some types of water bodies, depth) is used to assign a
              water body type for the purpose of dilution weighting.

              Estimate population served by municipal intakes, assuming all service
              connections are residential.

              —     Independent systems.  If an intake serves an independent system (i.e., a
                     single intake serves a particular group of residences and is not blended with
                     water from ground water wells or other surface water intakes), determine the
                     number of service connections. Multiply the number of service connections by
                     the county average number of persons per residence (available from U.S.
                     Bureau of the Census reports). Tabulate the number of persons served for
                     each independent system intake within the TDL, by level of contamination; for
                     intakes subject to potential contamination, tabulate by water body type.

              —     Blended systems.  If the intakes are part of a blended system, obtain
                     information about the entire system so that the total  population served can be
                     apportioned to each intake or well.  The necessary data include:

                     —     total number of people served or service connections for the blended
                            system,
                     —     number of surface water intakes inside the TDL,
                     —     number of surface water intakes outside the TDL,
                     —     number of ground water wells in the system,

                                            267                                     Section 8.8

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                      —     whether any individual well or intake provides more than 40 percent of
                             the water to the system, and
                      —     whether any wells or intakes are standby wells or intakes.

                      If any well or intake provides more than 40 percent of the water to the system,
                      obtain annual average pumpage or capacity data for each intake or well
                      (standby intakes or wells require slightly different information; refer to Section
                      8.10). Apportion the population served to the intakes and wells in the blended
                      system, following the guidance given in Section 8.9. Multiply the number of
                      service connections assigned to each intake within the TDL by the average
                      number of persons per residence. Tabulate the number of persons served for
                      each intake within the TDL, by level of contamination; for intakes subject to
                      potential contamination, tabulate by water body type.

(4)     Calculate a population factor value for the drinking water threat assuming all service
       connections are residential. Highlight 8-34 provides an example of the tabulation of
       populations and calculation of the population factor value.

              Tabulate the total number of persons served by all drinking water intakes within the
              TDL by (1) level of contamination (i.e., Level I, Level II, potential) and  (2) water body
              type for intakes subject to potential contamination.

              For intakes subject to Level I concentrations, multiply the number of individuals served
              by 10 to calculate the Level I concentrations factor value.

              For intakes subject to Level II  concentrations, the number of individuals served is the
              Level II concentrations  factor value.

              For intakes subject to potential contamination,  assign a dilution-weighted population
              value for each water  body type using MRS Table 4-14. Sum the dilution-weighted
              population values assigned for each water body type. Multiply the result by 0.1 to
              obtain the potential contamination factor value. If the potential contamination
              population factor value  is less than 1, do not round to the nearest integer. If it is
              greater than 1, round to the nearest integer.

              Sum the factor values assigned for Level I,  Level II, and potential contamination to
              obtain the population factor value (for municipal intakes, assuming residential
              concentrations only).

(5)     Determine if student or worker populations should  be documented. This evaluation may
       involve a number of considerations, including  those listed  below.

              Surface water pathway score assuming all residential connections. If the surface
              water pathway score  for the site is over 100 points assuming all service connections are
              residential, it may not be cost-effective to document the student or worker populations
              for scoring purposes. The presence of student or worker populations served by intakes
              within the TDL, however, should be noted in the documentation record.

              Position within ranges for determining dilution-weighted population value. If the
              population served by municipal intakes drawing from a particular water body type is in
              the lower part or middle of a broad range (MRS Table 4-14), documenting the population
              served at schools or  businesses may  not change the population factor value. If the
              population is near the upper end  of a  range, however, a substantially higher population
              factor value might be achieved by documenting the additional
Section 8.8                                     268

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                                    HIGHLIGHT 8-34
             DOCUMENTING DRINKING WATER THREAT POPULATION
LEVEL 1 CONCENTRATIONS
Level 1 Intake
None
Population (individuals)
-
Reference3
-
Level 1 Concentrations Factor Value: 0
LEVEL II CONCENTRATIONS
Level II Intake
1-1
Population (individuals)
34,000
Reference3
32, 18,21
Level II Concentrations Factor Value: 34, 000 x 1 = 34,000
POTENTIAL CONTAMINATION
Potential Intake
Water Body Type
I-2
large stream to river
I-3
large river
Population
(individuals)
34,000
34,000
Dilution-weighted
Population Value
52
5
Reference3
32, 33, 25
32, 33, 25
Potential Contamination Factor Value: [52 + 5] x 0.1 = 5.7, which is rounded to 6
TOTAL POPULATION FACTOR VALUE: 34,000 + 6 = 34,006
         aThe numbers in the reference column would identify particular references in the MRS scoring package.
              population served at schools or businesses. If the population is near the lower end of a
              range, evaluating the student or worker population may help solidify the score.

       To document student/worker populations, continue to Step (6); otherwise continue to Step (8).

(6)     Document student and/or worker populations served by municipal systems.

              Identify schools and businesses served by intakes within the TDL. Obtain from
              water authorities information on the schools and businesses they serve.

              —    Document any schools or businesses served by intakes subject to actual
                    contamination.

              —    For potential contamination, focus efforts on large schools (e.g., universities) or
                    businesses and on those served by intakes on small water bodies.

              Document the number of students or workers.

              —    Contact the school officials to document student population.
                                           269
                                                                                  Section 8.8

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              —     Contact the individual businesses to document worker population or refer to
                     business census data. The local Chamber of Commerce may be able to provide
                     helpful data.

(7)     Calculate a population factor value that includes the student/worker populations. See
       Step (4). Make sure not to double count drinking water system connections as both
       residential and serving students or workers.

(8)     Determine if private intakes should be documented. This determination involves the same
       considerations listed in Step (5). In addition, any private intake subject to actual contamination
       should be documented. If documenting private intakes is necessary, proceed to Step (9). If not,
       evaluation of the population factor is complete.

(9)     Evaluate population served by private intakes within the TDL. If private intakes are
       identified, contact the owners to determine if the intakes are used for drinking water.

(10)    Revise the previous tabulation of drinking water population. Add the number of persons
       served by private intakes to the appropriate population totals according to level of contamination
       and, for those subject to potential contamination, water body type.

(11)    Calculate a population factor value that includes populations served by private intakes.
       Follow the procedure outlined in Step (4).

Highlight 8-35 provides an example of scoring the population factor for the drinking water threat.
                                     HIGHLIGHT 8-35
         EXAMPLE OF SCORING DRINKING WATER POPULATION FACTOR

 WaterSupply: Independentsystem consisting of a single surface water Intake located approximately 1/2
               mile downstream from the PPE on a moderate to large stream (7OO cfs).

 Population
 Served:       The total number of service connections for this system is 1,500. The entire area served
               by the system lies within one county. 1990 Census data Indicate that the average number
               of persons  per residence for that county is 2.8.  Assuming that all  connections are
               residential,  the total population served by the system is:

                       1,500 x 2.8 = 4,200 people

 Evaluation:    The intake is subject to potential contamination. Use MRS Table 4-14 to assign a dilution-
               weighted population value.

 The population served by this intake gives the following potential contamination factor value:

        Potential contamination factor value = 1/10 x 52 = 5.2, rounded to 5

 Because this is the  only drinking  water intake within the TDL,

        Population factor value = 5.
Section 8.8                                     270

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EVALUATING THE NEAREST INTAKE FACTOR

(1)     Determine if any drinking water intake for the watershed being evaluated is subject to
       actual contamination. If not, continue to Step (2). If so, score the nearest well factor as
       follows:

              If any drinking water intake is subject to Level  I concentrations, assign a factor value of
              50.

              If any drinking water intake is subject to Level  II concentrations, but no intake is
              subject to Level I concentrations, assign a factor value of 45.

(2)     Identify the nearest drinking water intake within the TDL for the watershed being
       evaluated. Measure from the PPE (or, for contaminated sediments with no identified source,
       from the point where measurement of TDLs begins).

(3)     Assign a dilution weight to the nearest intake. Use  MRS Table 4-13 to assign a dilution
       weight based on the type of surface water body in which the intake is located.

(4)     Calculate the nearest intake factor value. Multiply the dilution weight from Step (3) by 20.
       Round the product to the nearest integer, and assign the result as the nearest intake factor
       value.

TIPS AND REMINDERS

       Determine target populations by the location of the intake,  not the location of the residence,
       school, or workplace served by the intake.

       If a drinking water system  includes portions of more than one county and the specific number
       of residences supplied in each county is known,  use county-specific estimates of
       persons-per-residence. Otherwise, use the lowest known persons-per-residence figure for the
       applicable counties to estimate the entire population served.

       The definition of students may include students at nontraditional schools (e.g., fire training
       class, truck driving school). Use the school's daily average enrollment as the figure for
       number of students. For example, if the school has four classes per year, each lasting three
       months and each with an enrollment of 30 students, then the  number of students is thirty.

       For water bodies other than small streams, dilution weights are very small. Consequently,
       intakes subject to potential contamination often result in relatively few targets points, even if
       they serve a large population.

       Private intakes subject to actual contamination (particularly Level I) can result in a substantial
       drinking water threat score. Because of the broad population  ranges used to evaluate intakes
       subject to potential  contamination and the small dilution-weighting factors for all but the smallest
       water bodies, private intakes subject to potential contamination generally will not
       increase the drinking water threat score based on municipal intakes.

       Include the population using intakes closed because of site-related actual contamination  in
       estimating the drinking water population. This population should reflect the number of people
       using the intake at the time it was closed.
                                             271                                     Section 8.8

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SECTION  8.9
BLENDED WATER
SUPPLIES
       This section presents guidance and background information regarding the evaluation of the
population factor for the drinking water threat when a surface water intake is part of a blended water
supply system. The population factor for the drinking water threat is evaluated based on the level of
contamination (i.e., Level I, Level II, and potential contamination), the number of people, and for
potential contamination, the flows (or depths) at surface water intakes within the TDL. In some instances,
discrete populations can be linked directly to individual intakes. In other cases, water from multiple
intakes (or multiple intakes and ground water wells) is blended together prior to or during distribution to a
target population. The MRS specifies a method for apportioning the total population served by such a
system among the units (i.e., intakes, wells, or mains) making up the system.

       The MRS provides for dividing a target population equally among all the water supply units
that contribute to the blended system, as long as no single supply (i.e.,  intake, well, or main)
contributes more than 40 percent (based on average annual pumpage or capacity) of the total supply.
If any one unit provides more than 40 percent, the percentage contributed by each of the water
supply units needs to be determined. Under these circumstances, each intake or well is assigned a
percentage of the population based on its relative contribution.
        Section 4.1.2.3
        Section 4.1.2.3.2
 RELEVANT MRS SECTIONS

Drinking water threat — targets
Population
DEFINITIONS
       Blended Water Distribution System: A drinking water supply system that can or does
       combine (e.g., via connecting valves) water from more than one well or surface water intake,
       or from a combination of wells and intakes.

       Capacity: The amount of water a well or intake can deliver to a water distribution system.
       Capacity may be expressed in units that are equivalent to a pumpage rate or as a percentage
       of the system's requirements.

       Pumpage Data: A measure of the volume of water per unit of time discharged from a well, or
       collected within an intake, either by pumping or free flow. Well pumpage is commonly
       measured in gallons per minute (gpm), cubic meters per day (nf/day; 1 gpm = 5.45  m3/day),
       or cubic feet per second (cfs; 1 gpm = 0.0023 cfs). Pumpage data may also be termed well
       production data, well discharge data, well flow data, well yield data, pumping line data, and for
       intakes, intake pipe flow data. For MRS purposes, pumpage data relate to the measured or
       estimated rate of water withdrawal from a well or intake, not from a storage tank or  reservoir
       used as a receptor for water drawn from one or more wells and/or intakes. SeeHighlight
       8-36 for more information on pumpage data.
                                           273
                                                                                 Section 8.9

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                                     HIGHLIGHT 8-36
                            PUMPAGE AND CAPACITY DATA

 Data on the contribution of each intake or well to the total blended water system may be supplied in several forms,
 including pumpage or capacity. All data used to evaluate a given system for the purposes of apportioning
 population should be of the same type (e.g., do not use capacity data for some intakes or wells and pumpage data
 for others). In addition, the data must be in the same units. An abbreviatedconversion table is provided below.
         1 gal/min                      = 0.00223 ft3/sec               = 5.45 m3/day
         1 ft3/sec                       = 448.8 gal/min                = 2,447 m3/day
         1 m3/day                      = 4.09 x 10'4 ft3/sec             = 0.183 gal/min.
 Pumpage. Many water authorities keep pumpage records expressed as the total quantity of water pumped in
 a given interval, usually a day, month, or year, not in terms of pumpage for the period during which a well is
 used. Metered pumpaqe  data are the most reliable  and, therefore, the preferred type of data. However,
 estimates of pumpage calculated by the water authorities based on engineering parameters built into the well
 or intake design, construction, and  pump configuration may also be acceptable.

 Capacity. The sum of the capacities may represent  more than the total needs of the system. The relative
 capacity of each component, however,  may be calculated by dividing the capacity of the component by the
 sum of the capacities of all the components. This normalization procedure means that the sum of the relative
 capacities of all the components in  the system will total  100 percent.

 Standby intakes. When using pumpage data for a standby surface water intake, use average pumpage for
 the  period during which the standby intake is used rather than average annual pumpage (MRS section
 4.1.2.3.2). See Section 8.10 for additional information.
       Standby Intake: A surface water intake held in reserve by a water supply entity (e.g., agency,
       authority, cooperative, private company, or individual) and maintained for use. It is designated
       as a drinking water supply to be used during a water supply shortage or emergency such as
       pump failure, drought, sudden water quality deterioration, or interruption In the regular supply.

       Standby Well: A well held in reserve by a water supply entity (e.g., agency, authority,
       cooperative, private company, or individual) and maintained for use. It is designated as a
       drinking water supply well for use during a water supply shortage or emergency such as pump
       failure, drought, sudden water quality deterioration, or interruption In the regular supply.
       Additional terms commonly used to signify standby wells include reserve wells, drought wells,
       safety wells, emergency wells, backup wells, substitute wells, and uncommitted wells.

       Population for the Drinking Water Threat: Number of residents, students, and workers
       regularly served  by surface water Intakes that are  located within the TDL for the surface water
       bodies evaluated for a given watershed. This population does not include transient populations,
       such as hotel and restaurant patrons, but may include seasonal populations (e.g., a resort area).

SCORING THE POPULATION FACTOR FOR BLENDED WATER SUPPLIES

       The steps described  below outline the procedures for evaluating the population factor for
blended water supplies. Highlight 8-37 summarizes the data needed for the evaluation.
Section 8.9                                      274

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                                     HIGHLIGHT 8-37
               DATA NEEDS FOR EVALUATING BLENDED SYSTEMS

 The typical data used to document the evaluation of the population factor when blended water systems are
 involved may Include all of the following:

         Identification of all the water supply entities with intakes within the TDL.

         Number and  location  of  water supply units (i.e., surface water intakes, ground  water wells,
         standby/emergency supplies) and flow (or depth) data for surface water intakes subject to potential
         contamination.

         Specifics of the water distribution system:

         —      Geographic extent
         —      Number and types of connections (residential, industrial, commercial)

         Pumpage and/or capacity data for Intakes and wells expressed in comparable units.

 Much of the information required to evaluate blended water systems can be collected directly from the water supply
 entities or local regulatory authorities. In addition, because some of the required Information relates specifically
 to water resources studies, the district office of the Water Resources Division of the USGS and its counterpart in
 the state should be contacted as necessary. These sources may provide more detailed well and flow data through
 such publications as their Water Resources Investigation series, the Hydrologic Atlas series, and annual reports
 on specific river basins.
(1)     Identify all blended water supply systems that may have drinking water intakes within the
       TDL. If more than one blended system is present, repeat Steps (2) through (6) for each
       system. If a  blended system supplies water to another blended system or receives water from
       another blended system, refer to the subsection, Scoring Multiple Blended Systems.

(2)     Identify all water supply units (i.e.,  intakes and/or wells) for the blended system. Identify
       all water supply units of the blended system including units within and outside the TDL. The
       water supply units may include surface water intakes, ground water wells, and
       standby/emergency supplies. Mark the location of each intake or well relative to the site on a
       scale map or diagram.

(3)     Determine which intakes will be evaluated as targets for the population factor.

              Although all water supply units must be identified to apportion population, include only
              intakes that are within the TDL for the watershed in scoring the population factor.
              Remember that any intake subject to actual contamination is evaluated regardless of its
              distance from the site.

              If the blended system includes standby intakes, include or exclude some, all, or none of
              the standby intakes to obtain the highest population factor value. Exclude all standby
              ground water wells. See Section 8.10 for more detailed  guidance on evaluating standby
              intakes.

(4)     Determine the total number of persons served by the blended system.  If the data are
       provided in terms of service connections rather than persons  served, multiply the number of
       service connections by the average number of persons per residence for the county.
                                              275                                       Section 8.9

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(5)     Determine whether any single intake or well supplies more than 40 percent of the
       system's water. Base this determination on average annual pumpage or capacity data.

(6)     Apportion the population served by the blended system as follows:

              If no single intake or well supplies more than 40 percent of the system's water, apportion
              the  population equally to all intakes and wells in the system (i.e., divide the total
              population by the number of intakes and wells).

              If a  single intake or well supplies more than 40 percent of the system's water,  apportion
              population to each intake or well based  on the percentage of water it supplies. Use
              average annual pumpage or capacity to determine the percentage of water each intake
              or well supplies.

(7)     Tabulate the population assigned to intakes within the TDL. Add this population to any other
       target population (e.g., from other independent or blended systems) to evaluate the drinking
       water population factor for the watershed. See Section 8.8 for detailed information on  scoring the
       population factor.

Highlights 8-38 and 8-39 provide examples of scoring the population factor for blended water systems.

SCORING MULTIPLE BLENDED SYSTEMS

       Some blended water systems receive water from (or supply water to) another blended water
system via one or more water mains. The steps below describe how to apportion  population to each
supply intake or well in such cases. The blended system that receives water is referred to as System R;
the blended system that supplies water is referred to as System S. If two or more blended systems
supply water to each other, evaluate the systems as one combined blended system; do not use the steps
below.

APPORTION POPULATION SERVED BY RECEIVING SYSTEM (SYSTEM R)

       When evaluating a blended system that receives water from another system, include the water
mains through which the system receives water as water supply units (i.e., treat as a well or intake).

(1)     Determine  population served by System R. This step is identical to that for a normal
       blended system.

(2)     Identify all  water supply units for System R. The water supply units are ground water wells
       in System R, surface water intakes in System R, and water mains from System S. Each water
       main is treated in the same manner as one well  or intake.

(3)     Determine whether any single System R water supply unit provides more than 40 percent
       of System R's total water. Consider all wells and intakes in System R, and all water mains from
       System S.

(4)     Apportion the population in System R as follows:

              If no  water supply unit supplies more than 40 percent of the system's water, apportion
              the  population equally to each water supply unit in System R.

              If a  water supply unit supplies more than 40 percent of the system's water, apportion
              population to each water supply unit based on the percentage of water it supplies  Use
              average annual pumpage or capacity to determine the percentage of water each well,
              intake, or water main supplies.

Section 8.9                                     276

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                                     HIGHLIGHT 8-38
      SCORING  EXAMPLE OF SINGLE BLENDED SYSTEM WITH INTAKES
                    OUTSIDE OF THE TARGET DISTANCE LIMIT
Site Setting:
Water Supply:


Location of
Water Supply
Population
Served:
Evaluation:
The site is located in a suburban community, close to a river. The river is subject to
potential contamination, and a PPE has been identified. For MRS purposes, the river
is classified as a "large stream to river" (i.e., flow of > 1,000 to 10,000cubic feet per
second) at both intakes within the TDL (see MRS Table 4-13).

Three surface water intakes and three groundwater wells supply water to a blended
system prior to distribution.
•      One intake 2 miles downstream of the PPE;
       One intake 5 miles downstream of the PPE;
       One intake 2 miles upstream of the PPE; and
       Three wells in a well field adjacent to the site.

The water authority reports 80,000 connections.

The population density in the county in which the site is located is 2.5 persons per
residence. Assuming all residential connections:

Population served = 80,000 x 2.5 = 200,000 people.

No Level  I or Level II contamination  Is identified. Evaluate population based on
potential contamination. The water authority reports no intake or well contributes more
than 40 percent of its total  need. Therefore, assign 33,333.3 people (200,000/6) to
each intake and well In the  system.

66,666.6 people are assigned to the two intakes within the TDL, which are on a water
body of the type "large stream to river."

Using MRS Table 4-14, the dilution-weighted population  value is 52.

Potential contamination factor value (to nearest integer) = 1/10 x 52 = 5

Population factor value = 5
                                             277
                                                                                       Section 8.9

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                                       HIGHLIGHT 8-39
           SCORING EXAMPLE OF TWO SEPARATE BLENDED SYSTEMS
 Site Setting:

 Water Supply:
 Location of
 Water Supplies:
 Population
 Served:
 Evaluation:
The site is located in a densely populated urban center.

Two water authorities (Systems A and B) with separate water treatment plants and
separate distribution systems.

        System A is supplied by five surface water intakes.
        System B is supplied by three surface water intakes and one ground water
        well.

All intakes are within the TDL for surface water.

System A's intakes are located on a river with an average annual flow of 25,000 cfs(a
"large river' by MRS definition from Table 4-13).

System B's intakes are located on a river with an average annual flow of 8,000 cfs (a
"large stream to river' by MRS definition from Table 4-13).

The population density in the county servedby the water systems is 2.5 persons per
residence.

Water authority A reports 100,000 residential connections.

        Population served by System A = 100,000 x2.5 =250,000 people

Water authority B reports 40,000  residential connections.

        Population served by System B = 40,000 x 2.5 = 100,000 people

No Level I or Level II contamination is identified. Evaluate population  based  on
potential contamination. Both water authorities report that no well or intake contributes
more than 40 percent of their total needs.

Assign 50,000 people (250,000/5)to each of the five intakes in System A. Because all
intakes are on the same water body and are within the TDL, all 250,000 people in
System A are evaluated for a "large  river."

Assign 25,000  people (100,000/4) to each of the three System B intakes  and the
System B well.  75,000 people from System B (3 intakes x 25,000) are evaluated for
a "large steam to river." Do not include the population served by the ground water well
when  calculating the surface water population factor value.

The dilution-weighted population values are as follows (from MRS Table 4-14):

        Value for 250,000 people served by intakes on a
        "large, river'.'	16

        Value for 75,000 people served  by intakes on a
        "large  steam to river"	 52

Total dilution-weighted population value	 68

Potential contamination factor value (to the nearest Integer) = 1/10 x 68 = 7

Population factor value = 7
Section 8.9
                                                278

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(5)     Determine which System R intakes are within the TDL and tabulate the population served.
       In determining the population served, consider only the population apportioned to intakes within
       the TDL. Tabulate only the population served by System R intakes. Do not include the population
       apportioned to mains from System S. As with all blended systems, the population is tabulated by
       level of contamination and, for intakes subject to potential contamination, by dilution weighting
       category.

APPORTION POPULATION SERVED BY THE SUPPLYING SYSTEM (SYSTEM S)

       When calculating the total population served by a blended system that supplies water to another
blended system, include the total population served by the supplying system.

(1)     Determine the total population served by System S. This population includes all people
       served by System S plus some of the people served by System R.

       (6)     Refer to Step (4) above for the number of people served by System R that were
              apportioned to each System S water main.

       (7)     Add this number to the population served directly by System S to calculate the total
              population served by System S.

       After the total population served by System S is calculated, the water mains are not considered
       further in the evaluation for System S.

(2)     Identify all water supply units for System S. The water supply units are ground water wells in
       System S and surface water intakes in System S. The water mains to System R are not water
       supply units for System S.

(3)     Determine whether any single System S well or intake supplies more than 40 percent of
       the water for System S.

(4)     Apportion the population in System S as follows:

              If  no well or intake supplies more than 40 percent of the system's water, apportion the
              population  equally to all wells and intakes in the system.

              If a well or intake supplies more than 40 percent of the system's water, apportion
              population to each well or intake  based on the percentage of water it supplies  Use
              average annual pumpage or capacity to determine the percentage of water each well or
              intake supplies.

(5)     Include the population apportioned to any System S intake within the TDL in the
       tabulation of population served. As with all blended systems, the population is tabulated by
       level of contamination and, for intakes subject to potential contamination, by dilution weighting
       category.

An example of apportioning population to two blended systems in which one is supplying water to the
other is provided in Highlight 8-40.
                                            279                                     Section 8.9

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                                     HIGHLIGHT 8-40
             SCORING EXAMPLE FOR MULTIPLE BLENDED SYSTEMS
 Water Supply:   System S:


                System R:
 Location
 of Intakes:
 Population
 Served:
 Population
 Factor:
System S:
                System R:
               Blends water from four intakes; no  intake  provides >40 percent of the
               system's water.

               Blends water from four intakes and receives water from System S via 1 water
               main; no intake or main provides >40 percent of the system's water.
Two intakes are within 10 miles downstream from the PPE. The other two
intakes are outside of the TDL.

All four intakes are within 10 miles downstream from the PPE.
                All intakes within the TDL for both systems are subject to Level II contamination.
System S:
System R:
10,000 people
20,000 people
 Evaluation:     Apportion Population Served by Receiving System - System R

                Number of water supply units = 4 Intakes + 1 main = 5 units
                People/unit = 20,000/5 = 4,000

                Assign 4,000 people to each System R intake and the water main from System S.

                Apportion Population Served by Supplying System - System S

                Total Population = 10,000 (System S) + 4,000 (System R) = 14,000
                Number of water supply units = 4 intakes
                People/unit = 14,000/4 = 3,500
Assign 3,500 people to each System S intake.


Two System S intakes within TDL = 7,000 people
Four System R intakes within TDL = 16,000 people

Total Level II concentrations factor value = 23,000

Population factor value = 23,000
TIPS AND REMINDERS

       If no single intake or well supplies more than 40 percent of a system's total needs, apportion the
       population equally to all intakes and wells even if more definitive information is available.

       Allocate population served to each well or intake in a blended system, but only include as targets
       those populations allocated to intakes located within the TDL for the watershed.

       When two or more blended systems regularly provide water to each other, evaluate the systems
       as one combined blended system.
Section 8.9
                                              280

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SECTION 8.10
STANDBY
INTAKES
       This section defines standby intakes and associated terms, provides guidance and background
information on the use of standby intakes to evaluate certain factors within the targets factor category of
the drinking water threat, and explains how to apportion population to standby intakes. Standby intakes in
the drinking water threat are treated in the same manner as standby wells In the ground water pathway.
A standby intake that meets certain criteria may be used to score the nearest intake and/or the
population factors. To designate a standby intake as the nearest intake, it must be used for drinking
water supply at least once a year. In order to include a standby intake when evaluating the population
factor, the intake must be maintained  regularly so that water can be withdrawn. Standby intakes are not
considered in the evaluation of the resources factor.
                              RELEVANT MRS SECTIONS
        Section 4.1.2.3.1        Nearest intake
        Section 4.1.2.3.2        Population
DEFINITIONS
       Annual Use: Criterion for determining whether a standby intake may be used to evaluate the
       nearest intake factor. To meet this criterion, a standby intake generally should supply drinking
       water for at least one 24-hour period in a year.

       Regular Maintenance: The routine inspection, cleaning, and testing of a standby intake so that
       it can be ready for immediate use. This is a criterion for determining whether a standby intake
       may be used to evaluate the population factor. Regular maintenance of a standby intake may
       include direct measurement of (or knowledge of) the surface water level, inspection of intake
       screen and pump, and testing of the pump. Such activities generally should  be conducted at
       least once a year and the operating authority should consider the intake functional. Rehabilitation
       activities, with the intent of retaining a standby intake in  a state of readiness, also can be
       considered regular maintenance. Such activities include pump cleaning and lubricating or screen
       cleaning.

       Standby Intake: A surface water intake held in reserve by a water supply entity (e.g., agency,
       authority, cooperative, private company, or individual) and maintained for use. It is designated
       as a drinking water supply to be used during a water supply shortage or emergency, such as
       pump failure, drought, sudden water quality deterioration, or interruption in the regular water
       supply.

       Water Withdrawal Rotation Program: Program in which intakes within a water supply system
       are used only for specified  intervals, after which other intakes or wells are used. Rotation
       programs are designed to minimize drawdown interference and to maximize efficient use of
                                           281                                    Section 8.10

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       water in relation to varying water demand. Do not consider an intake that is part of a planned
       water withdrawal rotation program a standby intake

       Nearest Intake Factor: Factor for evaluating the maximally exposed intake. This factor is based
       on the presence of actual contamination or, for watersheds where no intake is subject to actual
       contamination, the flow or depth of the water body at the intake nearest to the PPE within the
       TDL.

       Population for the Drinking Water Threat: Number of residents, students, and workers
       regularly served by surface water intakes that are located within the TDL for the surface water
       bodies  evaluated for a given watershed. This population does not include transient populations,
       such as hotel and restaurant patrons, but may include seasonal populations (e.g., a resort area).

       Pumpage Data: A measure of the volume of water per unit of time discharged from a well, or
       collected within an intake, either by pumping or free flow. Well pumpage is commonly measured
       in gallons per minute (gpm), cubic meters per day (nf/day; 1 gpm = 5.45 m3/day), or cubic feet
       per second  (cfs; 1 gpm = 0.0023 cfs). Pumpage data may also be termed well production data,
       well discharge data, well flow data, well yield data, pumping line data, and for intakes, intake
       pipe flow data. For MRS purposes, pumpage data relate to the measured or estimated rate of
       water withdrawal from a well or intake, not from a storage tank or reservoir  used as a receptor
       for water drawn from one or more wells and/or intakes.

       Capacity: The amount of water a well or intake can deliver to a water distribution system.
       Capacity may be expressed in units that are equivalent to a pumpage rate or as a percentage of
       the system's requirements.

SCORING  THE NEAREST INTAKE FACTOR USING STANDBY INTAKES

(1)     Identify the standby Intake(s).

              Water supply entities generally refer to standby intakes by any of the following terms:
              standby intakes, reserve intakes, drought intakes, safety intakes, emergency intakes,
              backup intakes, substitute intakes, and uncommitted intakes.

              Even when one of the above terms  is applied to an intake, the intake should not be
              considered a standby intake  unless it meets MRS criteria.

              Standby intakes may be located either upstream of or downstream from the primary
              intake or even in a different watershed. They are commonly found where waterworks
              facilities have been upgraded or where municipalities have merged  or collaborated to
              form a single water supply system.

              Some water supply entities utilize multi-level water withdrawal intakes at a single point in
              a lake or impounded portion of a river. One or more of these intakes may be used for
              water withdrawal on a regular basis, while  other intakes may be designated for use only
              under critical water level conditions. Multi-level intakes with  at least one level used on a
              regular basis should not be evaluated as standby intakes.

(2)     Determine whether the standby Intake Is  eligible to be used to score the nearest intake
       factor.  The  standby intake may be used if it meets both of the following conditions:

              The standby intake is within the TDL for the watershed being evaluated; and

              The standby intake has been used annually. It is not necessary to document that the
              intake has been used  annually for the entire time it has been designated as a standby
Section 8.9                                     282

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              intake. Documenting annual use in recent years (e.g., during the past five years)
              generally is sufficient. If the intake has been brought into a state of readiness only within
              the past few years, annual use since that time should be documented.

(3)     Use an eligible standby intake as the nearest intake if it results In a higher nearest Intake
       factor value than any regular Intake.

SCORING THE POPULATION FACTOR USING STANDBY INTAKES

(1)     Identify the standby Intake(s).

(2)     Determine whether any standby intake is eligible to be used to score the population
       factor. The standby intake may be used to score the population factor if it meets both of the
       following  conditions:

              The standby intake is within the TDL for the watershed  being evaluated; and

              The standby intake is receiving regular maintenance (as defined above). If a standby
              intake meets the annual use criterion for the nearest intake factor,  it is likely to  have  also
              received regular maintenance.

(3)     Evaluate the population factor with and without the standby intake(s).

              For a system consisting entirely of surface water intakes within the TDL, including  or
              excluding an eligible standby intake will only affect the score if the intake is at a different
              level of contamination or dilution weight from the regular intakes, or if it is in a different
              watershed.

              If there is more than one standby intake, calculate the population factor value for various
              combinations of intakes and wells. PREscore can be very useful for scenario testing.
              Each combination of wells and intakes must include:

              S      All regular intakes and wells;
              S      Some, all, or none of the standby intakes; and
              S      None of the standby wells.

              Note that the inclusion or exclusion of standby intakes may change the relative
              contribution of each water supply unit to the total water supply. In some cases,  this may
              affect whether one well or intake provides more than 40 percent of the system's water.

              Do not double count by assigning the same population to both a standby intake and to a
              regular intake or well. Each segment of the population must be assigned to  one and only
              one intake or well.

              When apportioning the population of a blended system based on pumpage  data, use
              average pumpage (e.g., gallons per minute) for the period during which the standby
              intake is used, rather than average annual pumpage. Highlight 8-41 provides additional
              information on pumpage and capacity data for standby  intakes. Section 8.9  provides
              detailed guidance on scoring the population factor for blended systems.

(4)     Choose the combination of regular and standby intakes that results In the highest
       population factor value.
                                             283                                    Section 8.10

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                                   HIGHLIGHT 8-41
            PUMPAGE AND CAPACITY DATA FOR STANDBY INTAKES


 If no well or intake provides more than 40 percent of the total water supply for the system, simply
 apportionthe population equally among the wells and/or intakes. However, if one intake orwell provides
 more than 40 percent of the total water supply forthe system, population must be apportioned according
 to each well's or Intake's share of the total supply. Consider the following points when apportioning
 population In a system with standby Intakes where one water source provides more than 40 percent of
 the total supply.

        Use either capacity or pumpage data to calculate the percentage  of the  population to be
        assignedto each component of the system. Do not use pumpage data for one component and
        capacity data for other components.  Data from standby intakes and regular intakes and wells
        must be in the same units.

        When using pumpage data for a stand by intake, use average pumpage for the period during
        which the standby Intake is used ratherthan average annual pumpage. The period during which
        a standby intake is on line but not actually pumping should not  be considered part of the
        period during which the standby intake is used.

        Often pumpage data forstandby Intakes are not based on water flow meter readings, but reflect
        estimates based on pumping test data, pump size, orifice of effluent pipe, or duration of pump
        operation. Although metered pumpage data should be used whenever possible, pumpage may
        be estimated based on these or other appropriate parameters.

        If possible, attempt to calculate pumpage rates based  on an average over the most recent
        periods of use. However, calculation of the pumpage rate for a standby intake can be based
        on a period of use several years aqo.
       Highlight 8-42 summarizes the data needed for evaluating standby miakes.Highlight 8-43
provides an example of (1) calculating average pumpage for a standby intake and (2) calculating the
relative contributions for a blended system including a standby m\ake.Highlight 8-44 provides an
example of scoring the population factor using a standby intake.
Section 8.10                                   284

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                                    HIGHLIGHT 8-42
                        DATA NEEDS FOR STANDBY INTAKES

Contact local water supply entities (or regulatory authorities) directly to obtain the following data needec
to evaluate standby intakes:

       Ensure that the Intake is one that is held in reserve to be used during a water supply emergency.

       Confirm that the intake has a working pump

       For the nearest Intake factor,  document that the intake has been used annually (e.g., for a
       24-hourperiod during acalendaryear). Documenting annual use in recent years (i.e..during the
       past five years) generally is sufficient.

       For the population factor,  document that the intake has been regularly maintained since
       established as a standby intake.

       Additional information (e.g., pumpage or capacity data) may be required when apportioning
       population to standby intakes and then  using the standby intake to evaluate the population
       factor.
                                    HIGHLIGHT 8-43
                   USING PUMPAGE DATA FOR STANDBY INTAKES

                    A standby intake is used for 28 days

                    30,240,000 gallons of water are drawn from the intake during the 28-day period


                         	Total pumpage for period of use	.           =
Standby
Intake
Use:
Calculation
of Pumpage:
Apportionment:
                         (# days used) (24 hours/day) (60 minutes/hour)
                                  30,240.000   =  750 gpm
                                  (28) (24) (60)


                    Water from this standby Intake Is blended with two regular Intakes that have
                    pumpage rates of  1,600  gpm and 4,000  gpm  respectively. The  relative
                    contribution of each is:
                               75O
                                                        75O   =   12%
                        (750 + 1,600 + 4,000)


                              1,600	
                        (750 + 1,600 + 4,000)


                              4.000	
                        (750 + 1,600 + 4,000)
                                                       6,350


                                                       1.600
                                                       6,350


                                                       4,000
                                                       6,350
=  25%
=   63%
                    Because one intake provides more than 40 percent of the total supply, population
                    apportionment is based on each intake's relative contribution to the total.

                                           285
                                                                                  Section 8.10

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                                        HIGHLIGHT 8-44
         EVALUATING POPULATION FACTOR USING A STANDBY INTAKE


   Site Setting:    The site is in a suburban location with moderate population density.

   Water Supply:  The local water system utilizes two surface water intakes, S1 and S2 (each pumping at a rate
                  of 1,500 gpm), along a small river and one ground water well (also pumping at a rate of
                  1,500 gpm) as part of a water withdrawal rotation program.  Each Is used as the primary
                  drinking water source approximately one-third of the time, as part of a rotation program.

                  Another surface water intake (with a pump capacity of 1,500 gpm) Is regularly maintained
                  to serve as an standby supply.

   Location of     Regular surface water intakes are located between 1/2 and 1  mile (S^) and between 1 and
   Water Supply:  2 miles (S2) downstream from the site. The standby intake draws from a location near intake
                  S.,. Average flows at these intakes range from 8,000 to 9,000 cfs.

                  The ground water well, G.,, is located between 1/2 and 1  mile from the site.
   Population
   Served:
   Evaluation:
           Source
                            PPE
Standby
 Intake
                                                           Regular
                                                            Intake
                 1mile
   Alternative 1:
The local water purveyor reports 2,400 residential connections.

The population density In the county  in which the site is located Is 2.5 persons per
residence.

Total population served = 2,400 x 2.5 = 6,000

Evaluate the water withdrawal rotation system as a blended system.  Level II concentrations
have been  documented at  intake S,, well G,, and the standby intake.  Sz is subject to
potential contamination only. The water authority reports that the capacity of the standby
intake is sufficient to replace any interruption in either the ground water or regular surface
water supply.

Include the standby Intake in apportioning population to the system.

Each of the four water supply units provides 25 percent.

Because  none of the four provides more than 40 percent of the total water supply, assign
one-fourth of the  population (1/4 x 6,000 = 1,500 people) to each well or intake.

(1)      Sum the population served  by  surface water intakes subject to  Level II
        concentrations.

                    (continued on next page)
Section 8.10
                                                286

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Alternative 2:
                              HIGHLIGHT 8-44 (continued)
           EVALUATING POPULATION FACTOR USING A STANDBY INTAKE
       1,500 (S., population) + 1,500 (Standby intake population) = 3,000

       Level II concentrations factor value = 3,000

(2)     Assign dilution-weighted population values from MRS Table 4-14 to
       surface water Intake subject to potential contamination (S2).

       1,500 people served by an intake located on a river are assigned 2 points.

       Potential contamination factor value = (1/10)(2) = 0.2

       (Note that the MRS specifies that this value is not rounded if it is less than 1.)

(3)     Add the values from Steps (1) and (2) to get the population factor value.

       3,000 + 0.2 = 3,000.2

Note:   The 1,500 people assigned to the ground water well are not included as
       surface water pathway targets; they would be evaluated in the ground water
       pathway.

Exclude the standby well In apportioning population to the system.

Each of the three water supply units provides 33 percent.

Because none of the  3 provides more than 40 percent of the total water supply,
assign one-third of the population (1/3 x 6,000 = 2,000 people) to each well or intake.
Selected
Alternative:
(1)     Sum the population served by surface water intakes subject to Level II
       concentrations.

       Level II concentrations factor value = 2,000 (S., population)

(2)     Assign dilution-weighted population values from MRS Table 4-14 to
       surface water Intake subject to potential contamination (S2).

       2,000 people  served  by an intake located along a small river  receive a
       dilution-weighted population value of 2.

       Potential contamination factor value = (1/10)(2) = 0.2

(3)     Add the values from Steps (1) and (2) to get the population factor value.

       2,000 + 0.2 = 2,000.2

Note:   The 2,000 people assigned to the ground water well are not evaluated forthe
       surface water pathway.

Because Alternative 1 results in the higher population factor value, Alternative
1 is used to evaluate the factor.
                                           287
                                                                                  Section 8.10

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TIPS AND REMINDERS

       The annual use criterion applies only to the nearest intake factor evaluation. A standby intake
       can be used to evaluate population without meeting the annual use criterion, providing it is
       regularly maintained so that water can be withdrawn.

       Including a standby intake is likely to yield a higher population score if its level of contamination
       is higher than that of regular intakes within the system (e.g., the standby intake is subject to
       Level I contamination and the regular supply intakes are subject only to Level II or potential
       contamination).

       If only potential contamination is scored, including a standby intake Is likely to yield a higher
       population factor score if it is located on a smaller water body than the regular supply intakes or
       if the blended system includes ground water wells.

       Do  not include standby ground water wells when scoring the surface water pathway.

       Use average pumpage for the period in which the standby intake is used, rather than average
       annual pumpage, when evaluating standby intakes.

       Standby intakes do not have to be Included in scoring. Even if one standby intake is included, it
       is not necessary to include all of them.  Include only those standby intakes that will increase the
       population factor value. The apportioning may be different than for the ground water pathway
       and may also differ for each watershed evaluated.
Section 8.10                                    288

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SECTION 8.11
RESOURCES
       This section provides guidance on scoring the resources factor for the targets factor category of
the surface water drinking water threat. The resources factor evaluates the possible loss of surface water
use resulting from site-related contamination of the surface water. The resources factor does not
evaluate threats to human health, which are considered in the nearest intake and population factors, and
in the human food chain threat. Unlike the ground water resources factor, the surface water resources
factor does not address commercial aquaculture, which is evaluated in the human food chain threat.
MRS section 4.1.2.3.3 discusses the resources factor.

DEFINITIONS

       Commercial Food Crops:  Crops that are intended to be sold widely, such as in supermarkets,
       and locally, such as those sold at local produce stands. Crops grown for domestic consumption
       or for use in a single restaurant are not considered commercial food crops.

       Commercial Forage Crops:  Crops grown to be sold as food for livestock (it is not necessary to
       document that these crops were sold only for commercial livestock), and grasslands used for
       grazing by commercial livestock (including areas technically defined as "pasture/rangeland1 by
       the USDA).

       Commercial Livestock: Livestock raised for sale to commercial wholesalers or supermarkets.
       Livestock raised for private or domestic use is not considered commercial livestock.

       Designated for Drinking Water Use:  Section 305(a) of the Clean Water Act requires states to
       prepare a water quality inventory that designates and classifies certain waters for drinking water
       use. The water can have such a classification even if it is not currently used for or is not currently
       suitable to be used for drinking water.

       Ingredient In Commercial Food Preparation:  Surface water used for wholesale food
       preparation (e.g., a manufacturer that prepares food products to be sold in supermarkets or
       produce stands). Food prepared in restaurants is not included in this category.

       Major or Designated Water Recreation Area:  A major water recreation area is an area used by a
       large number of people for recreational purposes (e.g., swimming or fishing). A designated water
       recreation area is an area designated and maintained by a government body (e.g. local, state, or
       Federal) as an area for public recreation.

SCORING THE RESOURCES FACTOR

(1)     Use the checklist In Highlight 8-45 to determine if any surface water uses that are
       assigned resource points apply to the watershed. Do not use standby intakes to evaluate the
       resources factor.
                                           289                                    Section 8.11

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The following sources of information on possible surface water uses will help in documenting resource
use fora watershed:

       USGS topographic maps and land use data
       USDA county crop records and irrigated acreage data
       Field observations
       Interviews with water company officials
       Public utility trade association online services (e.g., American Water Works Association's
       WaterNet data base)
       Existing PA/SI reports for the site or nearby sites.
       Correspondence with nearby businesses
       Correspondence with other nearby institutions, such as farms or universities
       EPA's FRDS
       Agricultural extension agents
       Local chambers of commerce
       Federal, state,  or regional parks and recreation departments
       State public water supply offices (usually found in state departments of health or environment)
       State water classification and designation maps

(2)     If a resource use Is documented, assign a value of 5 to the resources factor for the
       watershed; otherwise, assign a value of 0.
                                     HIGHLIGHT 8-45
                        CHECKLIST FOR THE RESOURCES FACTOR


 For the watershed being evaluated:

 (1)     Is surface water used to irrigate five or more acres of commercial food         Yes    No
        crops or commercial forage crops?

 (2)     Is surface water used to water commercial livestock?                        Yes    No


 (3)     Is surface water used as an ingredient In commercial food preparation?        Yes    No

 (4)     Is surface water used as, or used to supply, a major or designated water       Yes    No

        recreation area, excluding drinking water use?

 (5)     If.surface water Is not used for drinking water within  the TDL, is any           Yes    No
        portion of the surface water designated by the state  for drinking water
        use under Section 305(a) of the Clean Water Act, as amended, or is any
        portion usable for drinking purposes?

 If the answer to any of the above questions is "yes", assign a resources factor value of 5. If the answer
 to all questions is "no", assign a resources factor value of 0.
Section 8.11                                    290

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TIPS AND REMINDERS

       Because the surface water resources factor receives only 5 target points, this factor generally
       has little impact unless the site score is near the cutoff score.

       A surface water body used for drinking water and other specified resource use (e.g., irrigation)
       can be assigned target points for both the population and resources target values.

       A major or designated recreation area may also overlap with a sensitive environment and/or a
       fishery. Such an area may receive  points for resources and  sensitive environments and
       fisheries, if each type of use is documented.

       Resources for the surface water pathway are evaluated anywhere within the TDL for the
       watershed.
                                             291                                     Section 8.11

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SECTION  8.12
ACTUAL HUMAN FOOD
CHAIN  CONTAMINATION
       A fishery (or portion of a fishery) is subject to actual contamination if specific criteria
demonstrate the fishery has been contaminated by hazardous substances attributable to the site.
Fisheries subject to actual contamination are weighted more heavily than fisheries subject to potential
contamination in the human food chain target evaluation. In many cases, documenting actual human
food chain contamination results in a site score above the MRS cutoff.

       This section provides guidance on identifying and scoring fisheries (or portions of fisheries)
subject to actual human food chain contamination. When a fishery is present,  data used to document an
observed release to surface water may also satisfy the criteria for establishing actual human food chain
contamination. This section also provides  guidance on determining whether fisheries (or portions of
fisheries) subject to actual contamination are exposed to Level I or Level II concentrations, and scoring
sites with actually contaminated fisheries.
        Section 2.3
        Section 2.5
        Section 2.5.1

        Section 2.5.2
        Section 4.1.1.2
        Section 4.1.2.1.1
        Section 4.1.3.2.1.3
        Section 4.1.3.3
        Section 4.1.3.3.1
        Section 4.1.3.3.2
        Section 4.1.3.3.2.1
        Section 4.1.3.3.2.2
RELEVANT MRS SECTIONS

    Likelihood of release
    Targets
    Determination of level of actual contamination at a
    sampling location
    Comparison to benchmarks
    Target distance limit
    Observed release
    Bioaccumulation potential
    Human food chain threat - targets
    Food chain individual
    Population
    Level I concentrations
    Level II concentrations
DEFINITIONS
       Actual Contamination for the Human Food Chain Threat: Any portion of a fishery is subject
       to actual contamination if a hazardous substance with a BPFV of 500 or greater meets the
       criteria for an observed release; a fishery is closed, and a hazardous substance for which the
       fishery was closed is documented in an observed release; or a hazardous substance is present in
       a tissue sample from an essentially sessile, benthic food chain organism at a level that meets
       the criteria for an observed release.

       Aquatic Human Food Chain Organism: Aquatic species directly consumed by humans,
       including certain finfish, shellfish, crustaceans, amphibians, and amphibious reptiles.
                                          293
                                                                                Section 8.12

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       Benthic Organisms: Organisms that live on or at the bottom (i.e., not in the water column) of
       water bodies for most of their adult life cycle, such as clams, lobsters, and crayfish.

       Bioaccumulation Potential Factor Value (BPFV):  BPFV is a measure based on a hierarchy of
       three types of data:  bioconcentration factor; n-octanol-water partition coefficient (k£J; and water
       solubility. BPFV reflects the tendency for a substance to accumulate in the tissue of an aquatic
       organism - the greater the BPFV, the greater the relative tendency of a substance to
       accumulate. BPFVs for commonly encountered hazardous substances are listed in SCDM.

       Closed Fishery: A fishery closed or restricted by a government entity. Such closure prohibits
       fishing for commercial,  recreational, or subsistence purposes.  To be evaluated for the MRS,
       closure must be due to hazardous substances released from sources at the site.

       Essentially Sessile Benthic Organisms: Organisms that essentially stay at or near a localized
       spot in a water body during the adult stage of their life cycle (e.g., barnacles, oysters, muscles,
       sponges, and stalked diatoms). These organisms may not live on the bottom, but must not live
       suspended in the water column. They may be attached to rocks, pilings, or submerged banks at
       or near the surface. Samples from these organisms  can be used in the MRS for two purposes:

       (1)     To establish an observed release (use any essential sessile benthic organism); and

       (2)     To establish actual contamination and the level of contamination (use only human food
              chain organisms).

       Fishery: Any area of a surface water body from which human  food chain organisms are taken or
       could be taken  for human consumption  on a commercial, recreational, or subsistence basis.
       Food chain organisms include fish, shellfish, crustaceans, amphibians, and amphibious reptiles.
       Fisheries are delineated by changes in  dilution weights, level of contamination, or annual
       production. To  establish a  fishery, document that human food  chain organisms are present and
       that people fish in the surface water body.

       Level I Concentrations for the Human Food Chain Threat:  Level I concentrations are
       established in tissue samples from aquatic human food chain organisms in which the
       concentration of a hazardous substance that meets the criteria for an observed release isat or
       above its specific health-based benchmark. The tissue sample must also be taken from within
       the boundaries of the area of actual contamination. Aqueous and sediment sample results
       cannot be used to establish Level I concentrations for this threat. Benchmarks for the human
       food chain threat include FDAAL for fish or shellfish and screening concentrations for cancer and
       chronic noncancer effects.

       Level II Concentrations for the Human Food Chain Threat: Level II concentrations  are
       established in samples in which the concentration of at least one hazardous substance meets the
       criteria for an observed release, but the conditions for Level I concentrations are not met. In
       addition, Level  II is assigned for observed releases established by direct observation.

       Sessile Organisms: Organisms permanently attached to some substrate for most of their life
       cycle, such as sponges, barnacles, stalked diatoms,  and oysters.

DOCUMENTING PRESENCE OF A FISHERY

       Before evaluating the level of contamination, document that the surface water body under
evaluation is a fishery.  Collect evidence to document both  of the following:

              Human food chain organisms are present in the surface water body; and
              Some attempt has been made to catch those human food chain organisms.

Section 8.12                                    294

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       Useful sources of information include state and local fish and wildlife agencies, local bait and
tackle shops, visual observation during the SI of individuals fishing or of past fishery activity (e.g., fishing
lines and hooks left behind near the surface water body).

ESTABLISHING ACTUAL CONTAMINATION OF A FISHERY

       The following steps describe the procedures used to establish actual contamination. Because a
necessary criterion for establishing actual contamination is documentation of an observed release, the
first five steps are designed to document an observed release by chemical analysis. To establish an
observed release by direct observation, follow the procedures in the first step. To establish an observed
release by chemical analysis, use Steps (2) to (5). These steps should be repeated for each hazardous
substance attributable to the site detected in applicable surface water samples High light 8-46
summarizes procedures for determining whether fisheries are actually contaminated.

(1)     Establish an observed release by direct observation. An observed release can be
       demonstrated if at least one of the following criteria is met:

              A material that is documented to contain one or more site-related hazardous substances
              has been directly deposited into or has been seen entering surface water through
              migration (e.g., leachate, outfall, effluent);

              A source (or a portion of a source) has been flooded and at that time hazardous
              substances in  the source were in contact with flood waters (e.g., a wet surface
              impoundment  inundated by flood waters); or

              Evidence supporting the inference of a release of hazardous substances from the site
              exists and adverse effects associated with the inferred release can be  demonstrated
              (e.g., a significant fish kill occurred after electroplating wastes containing heavy metals
              were inadvertently spilled in a work area immediately adjacent to surface water).

(2)     Compile analytical results Indicating that a hazardous substance has been detected in
       surface water samples. To establish an observed release by chemical analysis to surface water
       and/or actual fishery contamination, review sediment, aqueous, and tissue sample data. To be
       eligible for establishing an observed release, tissue samples must be from essentially sessile
       benthic organisms (e.g., oysters) (seeHighlight 8-47).

(3)     Determine the background level for the hazardous substance. Determining the background
       level usually requires analytical results from one or more appropriate sample locations for each
       type of sample being evaluated (e.g., aqueous, sediment), particularly for substances that could
       be naturally occurring, ubiquitous, or attributable to other sites. A background level of 0 generally
       can be assumed for a  substance that is not naturally occurring, ubiquitous, or attributable to other
       sites.

(4)     Determine whether the  concentration of the hazardous substance Is significantly above
       background. Detailed guidance for making  this determination is found in Section 5.1,
       particularly Highlight 5-2.

(5)     Determine whether the  hazardous substance can be  attributed to the site. Sampling results
       or records (e.g., manifests, permits) indicating the presence of the hazardous substance in a
       source or sources at the  site are one useful  type of documentation. Information that the
       hazardous substance was used at the facility also may be acceptable. See Chapter 5 for
       additional guidance on attribution, including attribution of degradation products.
                                             295                                     Section 8.12

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                                                          HIGHLIGHT  8-46
                 FLOWCHART  FOR  IDENTIFYING CONTAMINATED  FISHERIES
                                                                                                      Actual contamination of
                                                                                                     the fishery is established;
                                                                 Does the observed release
                                                               certain a hazardous substance
                                                                  wihiWoaccumulation
                                                               potential factor value 2 500?
   Is there an observed release
     documented by direct
observation, from site sources to
       tha fishery area?
                                                                                   portion of the fishery into
                                                                                                     substances were directly
                                                                                                    Actual contamnalion of the
                                                                                                   fishery is established; ana of
                                                                                                   tdual contamination is the area
                                                                                                     between the PPE and the
                                                                                                   farthest sample containing at
                                                                                                   bast one hazardous substance
                                                                                                   that meets the criteria for an
                                                                                                    observed release and has a
                                                                                                   bioaccumulation potential factor
                                                                                                          value 2 500.
                                               Dots the sample contain a
                                              hazardous substance with a
                                               bioaccumulation potential
                                             factor value 2 500 that meets
                                              the criteria for an observed
                                                     release?
 Is there a sediment or aqueous
sample from within or beyond the
fishery area meeting the criteria
   for an observed release?
                                                                                                  Actual contamination of the
                                                                                                  fishery is established; area of
                                                                                                   actual contamination is the
                                                                                                   area between the PPE and
                                                                                                    the farthest essential/
                                                                                                    sessile banthic organism
                                                                                                   tissue sample meeting the
                                                                                                    critera lor an observed
                                                                                                          release.
 Is there a tissue sample from «n
 essentially sessile benthic human
 food chain organism meeting the
 criteria for an observed release,
 rom within or beyond the fishery?
                                                          Actual contamination of the
                                                        fishery is established; area of
                                                          actual contamination is the
                                                          area of the dosed fishery
                                                          between the PPE and the
                                                        farthest sample establishing
                                                          an observed release of the
                                                          hazardous substance for
                                                          which the fishery is dosed.
                                                                    The overall portion of the
                                                                                                If answers to questions
                                                                     Isnery subject to actual
  Is the fishery closed due to a
 hazardous substance that is also
documented in an observed release
 from the site to the watershed
  within or beyond the fishery?
                                                                                               fishery a not established;
                                                                                                score thai portion of the
                                                                     actually contaminated in
fishery wlnm the TDL as
                                                                                                potentially contaminated
Section 8.12
                                                                       296

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                                        HIGHLIGHT 8-47
               USE OF TISSUE SAMPLES FROM AQUATIC ORGANISMS
For the human food chain threat, tissue samples can be used to establish actual contamination and are required to
establish Level I concentrations. Aquatic organisms canbe divided into two groups: (1) essentially sessile benthic
organisms and (2) organisms likely to spend extended periods of time within a fishery that are not essentially sessile
benthic organisms. Only tissue samples from essentially sessile benthic human food chain organisms can be used
to establish both an observed release to surface water and actual human food chain contamination. Tissue samples
from other aquatic organisms, in certain circumstances, can be used to establish Level I contamination, but only
within an area of actual contamination  established with other samples (or by direct observation). Evaluate tissue
samples, as follows.


        Compare samples from similar organisms (e.g.,  similar age) of the same species.

        Compare samples of the same tissue type (e.g., liver samples should be compared with liver samples, roe
        samples with roe samples).

        The hierarchy of preference for sample types is: edible tissues (e.g., fillets for most finfish), edible tissues
        with associated tissues attached  or only partially removed, whole-body samples, and samples of  other
        specific tissues or organs.  Use less desirable sample types only when other data are not available.

        Verify the sample locations and note possible influences on sample data such as intervening tributaries.

The following table provides examples  of different tissue samples used  for MRS scoring and the function the
samples serve when evaluating the  human food chain threat.
             Sample Type
           Sample Use
  Example Organisms
  Essentially Sessile Benthic Organisms
                                       Used to establish an observed release.
                                    Barnacles
                                    Stalked Diatoms
                                    Sponges
  Essentially Sessile Benthic Human Food
  Chain Organisms
Used to establish an observed release and
actual contamination.
Mussels
Oysters
  Organisms Likely to Spend Extended
  Periods of Time Within the Boundaries of
  Actual Food Chain Contamination but not
  Essentially Sessile Benthic Organisms
Can be used to raise Level II concentrations
to Level I concentrations but cannot be
used to establish an observed release or
actual contamination.
Non-sessile Benthic:
   Lobsters
   Crabs
   Snails
   Shrimp
   Crayfish
   Scallops
Finfish:
   Pike
   Bass
   Tuna
   Flounder
   Trout
   Salmon
Other Food Chain Organisms:
   Frogs
   Salamanders
   Squid
                                                 297
                                                                                             Section 8.12

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(6)     Establish actual contamination. To establish actual contamination of a fishery (or portion of a
       fishery), the fishery must be within the area bounded by an observed release and at least one
       of the following criteria must be met:

              A hazardous substance with a BPFV of 500 or greater is present in an observed release
              sample (aqueous or sediment), or by direct observation;

              For a closed fishery, a hazardous substance for which it was closed must be
              documented in an observed release from the site. The hazardous substance need not
              have a BPFV of 500 or greater to establish actual contamination;  or

              A hazardous substance attributable to the site is present in tissue samples from an
              essentially sessile benthic human food chain organism at levels that meet the criteria for
              an observed release. The hazardous substance need not have a BPFV of 500 or greater
              to establish actual contamination.

       Only fisheries (or portions of fisheries) located within the boundaries of actual contamination are
       evaluated as subject to actual contamination. A fishery (or portion of a fishery) may be located
       within the boundaries of an  observed release to surface water but not be subject to actual
       contamination. For example, assume asbestos contamination was detected in aqueous and
       sediment samples at concentrations demonstrating an observed release to surface water. The
       BPFV for asbestos is less than 500. In the absence of other data, the fishery must be evaluated
       as subject to potential contamination because no substance with a BPFV greater than 500 has
       been documented in an observed release.

DETERMINING THE LEVEL OF ACTUAL CONTAMINATION

       A fishery (or portion of a fishery) is subject to actual contamination if it is located within the
boundaries of an observed release and the other criteria specified in Step (6) above, are met. The
following procedures outline  how to determine if a fishery for which actual contamination has been
established should be evaluated for Level I or Level II concentrations.Highlight 8-48 describes sample
types and criteria used to establish Level I and Level II concentrations.

(1)     If actual contamination is established based only on aqueous samples, sediment
       samples, or direct observation, score the portion of the fishery within the area of actual
       contamination as Level II concentrations.

(2)     If tissue samples from a human food chain organism are available, determine if such
       samples are eligible to be used to establish Level I, as follows.

              For essentially sessile benthic human food chain organisms, both of these criteria must
              be met:

              —     One or more hazardous substances in the tissue samples must establish an
                     observed release to surface water from the site; and

              —     The tissue samples must be from an aquatic species typically consumed by
                     people.

              For non-sessile or non-benthic human food chain organisms, all three of the following
              criteria must be met:

              —     The species sampled spends extended periods of time within the boundary of
                     actual fishery contamination; and
Section 8.12                                    298

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(3)
       —     Actual contamination is established through aqueous or sediment samples or
              from tissue samples from an essentially sessile benthic organism; and

       —     The hazardous substances found in tissues and compared to benchmarks are
              also present in the aqueous sample used to establish actual human food chain
              contamination.

For samples that meet the criteria In Step (2), compare the concentration of each
hazardous substance with Its health-based benchmarks for the human food chain threat.
If the hazardous substance concentration equals or exceeds its lowest applicable benchmark
concentration, consider the sampling location subject to Level I  concentrations for the human
food chain threat. See Highlight 8-49. If more than one hazardous substance meets the criteria
in Step (2), but no single hazardous substance establishes Level I, continue to Step (4).
n
c
s
s
HIGHLIGHT 8-48
SAMPLES AND CRITERIA FOR LEVEL 1 AND LEVEL II CONCENTRATIONS
IN THE HUMAN FOOD CHAIN THREAT
Sample Type
Usefulness for Human Food Chain Threat
Level 1
Surface Water/Sediment
Tissue From Essentially Sessile Benthic
Human Food Chain Organisms (e.g.,
clams)
Tissue From Non-Sessile or Non-Benthic
Human Food Chain Organisms (e.g.,
finfish, crabs)3
Cannot be used to establish Level 1 concentrations.
Hazardous substance concentrations must equal or
exceed lowest human food chain benchmark
concentration (or indices 1 or J must equal or exceed 1);
must also meet criteria for an observed release.
Hazardous substance concentrations must equal or
exceed lowest human food chain benchmark
concentrations (or indices for I orJ must equal or exceed
1).
Level II
Surface Water/Sediment
Tissue From Essentially Sessile Benthic
Human Food Chain Organisms (e.g.,
clams)
Tissue From Non-Sessile or Non-Benthic
Human Food Chain Organisms (e.g.,
finfish, crabs)
A hazardous substance with a BPFV of 500 or greater
must meet criteria for an observed release.
Hazardous substance concentrations less than lowesl
HFC benchmark concentrations (or indices for 1 and J
are less than 1); must also meetcriterialforan observed
release
Cannot be used to establish actual contamination and
therefore cannot be used to establish Level II (i.e., Level
II must already be established).

a Concentrations of hazardous substances must be measured in a tissue sample from a
on-sessile or non-benthic human food chain organism taken from within the boundary of actual food
hain contamination and from a species that spends extended periods of time within this boundary. The
pecific hazardous substance which is comparedto its benchmark must also be present in an aqueous,
ediment or benthic sample that establishes actual food chain contamination for the fishery.
                                            299
                                                                                  Section 8.12

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                                    HIGHLIGHT 8-49
              BENCHMARKS FOR THE HUMAN FOOD CHAIN THREAT

        FDAALs for fish or shellfish
        Screening concentration corresponding to oral RfD
        Screening concentrations corresponding to oral 1X1 tf cancer risk level.
(4)     Calculate the I and J indices based on all hazardous substances that meet the criteria for
       actual contamination. Make two lists of hazardous substances that meet the criteria in Step (2)
       above: hazardous substances with screening concentrations for cancer risk; and hazardous
       substances with screening concentrations for noncancer effects. Each hazardous substance may
       be on one, neither, or both of the lists. If more than one tissue sample has been taken and these
       samples are comparable (e.g., taken in the same time frame, collected using the same field
       techniques, analyzed by the same methods), select the highest concentration for each
       hazardous substance to use in the calculations below.

              Calculate the I index for all hazardous substances in the tissue sample that meet the
              criteria in Step (2) above, and  that have screening concentrations for cancer risk using
              the following equation:
       where:
              SC;


              n
                                                SC,
concentration of substance j in tissue sample
screening concentration for cancer risk corresponding to Id5 individual
cancer risk for oral exposure for hazardous substance i; and
number of hazardous substances that meet the criteria in Step (2) above
and have a SC available.
              Calculate the J index for all hazardous substances that meet criteria in Step (2) above
              and that have oral screening concentrations for noncancer effects using the following
              equation:
       where:
              CR,
              m
concentration of substance j in tissue sample
screening concentration for noncancer effects corresponding to the
reference dose for oral exposure for hazardous substance j; and
number of hazardous substances in sample that meet the criteria in Step
(2) above and for which a CR is available.
              If either the I or J index is greater than or equals 1, consider the sample location to be
              subject to Level I concentrations for the human food chain threat. If both the I and J
              indices are less than 1, consider the sample location to be subject to Level II.

SCORING SITES WITH ACTUAL CONTAMINATION

       Establishing actual human food chain contamination can affect the scoring of three MRS factors:
food chain individual, human food chain population, and hazardous waste quantity .Highlight 8-50
summarizes the scoring for these three factor values in relation to various levels of contamination.
Section 8.12
                                            300

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HIGHLIGHT 8-50
COMPARISON OF SCORING LEVEL 1, LEVEL II, AND
POTENTIAL CONTAMINATION
Level of
Contamination
Level 1
Concentrations
Level II
Concentrations
Potential Food
Chain
Contamination
Food Chain Individual
Factor Value
50
45
0 to 20 - depends on
dilution weight and whether
there is an observed
release
Population Factor Value
10 x Level I Human Food
Chain Population Value
1 x Level II Human Food
Chain Population Value
0.1 x Potential Human Food
Chain Population Value x
Dilution Weight
Minimum
Surface Water
HWQ Factor
Value3
100
100
10
a Only applies if Tier A is not adequately determined.

(1)     Assign a Food Chain Individual Factor Value.

              If any fishery (or portion of a fishery) is subject to actual contamination, base the value
              on the highest level of contamination present. Assign a value of 50 if Level I
              concentrations are present, or a value of 45 if only Level II concentrations exist.

              If no fishery is subject to actual contamination, but there is an observed release of a
              hazardous substance having a BCFV of 500 or greater to the watershed, assign a value
              of 20.

              If there is no observed release of a hazardous substance having a BCFV of 500 or
              greater, assign a value by multiplying the highest applicable dilution weight by 20 and
              round to the nearest integer.

(2)     Calculate Human Food Chain Population Factor Value (see Section 8.13). Calculate the
       human food chain population factor value for all fisheries (or portions of fisheries) being
       evaluated as follows:

              For the Level I concentrations factor value, sum HRS-assigned human food chain
              population values (MRS Table 4-18) and multiply by 10. If the product is less than 1, do
              not round to nearest integer;  if the product is greater than or equal to 1, round to the
              nearest integer.

              For the Level II concentrations factor value, sum the HRS-assigned human food chain
              population values (MRS Table 4-18) and multiply by 1.  If the product is less than 1, do
              not round to nearest integer;  if the product is greater than or equal to 1, round to the
              nearest integer.

              For the potential human food chain factor value, multiply the HRS-assigned human food
              chain population value (MRS Table 4-18) for each fishery by the surface water body
              dilution weight (MRS Table 4-13), sum the values, and  multiply by 0.1. If the
                                             301
                                                                                     Section 8.12

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(3)
       product is less than 1, do not round to nearest integer; if the product is greater than or
       equal to 1, round to the nearest integer.

       Sum the values for the Level I concentrations, Level II concentrations, and potential
       human food chain factors. Do not round the sum to the nearest integer.  Assign the sum
       as the population factor value for the watershed.

Review the Hazardous Waste Quantity Factor Value. If the hazardous waste  quantity
evaluation is  not based on complete hazardous constituent quantity data (i.e.,  Tier A) and if
Level I or Level  II concentrations are demonstrated for any of the three surface  water threats, the
minimum factor value for hazardous waste quantity is 100 for all surface water threats.
       Highlight 8-51 provides a site-specific example for determining whether a fishery (or portion of a
fishery) is subject to Level I concentrations, Level II concentrations, or potential contamination.
                                     HIGHLIGHT 8-51
            IDENTIFYING LEVEL OF CONTAMINATION FOR FISHERIES
   Site Description:
                 Operations at this site consisted of recycling wood preserving solutions that
                 contained hazardous substances X, Y, and Z. Adjacent to the site is Little Creek,
                 which flows through a predominantly rural,  non-agricultural area.  The average
                 annual flow is 30 cfs.  Little Creek is salt water and is used for both commercial and
                 recreational fishing. Sampling locations are shown below.
                              Source
                          PPE;
                                    (continued on next page)
     ED  Station for finfish sample

     O  Sediment sample location
Section 8.12
                                             302

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                               HIGHLIGHT 8-51  (continued)
             IDENTIFYING LEVEL OF CONTAMINATION FOR FISHERIES
Compound
X
Y
Z
Sediment Sampling
Data by Location3
(ppm)
SD2
440
25
50
SD3
18
500) compared to levels in  SD.,. The portion of the fishery between
               Samples SD2 and SD3is also actually contaminated based on levels  of X in SL^.Station B and C
               sample results indicate the presence of X in finfish samples, but levels are below the benchmark,
               so results do not support Level I concentration.

Level of
Contamination: Because sediment samples cannot be used to establish concentrations in the human food chain
               threat, the finfish samples are the only possibility for establishing Level I.

               —      Although the substance Z concentration detected at Station C is above the applicable
                       benchmark, it cannot be used to  establish Level  I concentration because this finfish
                       sampling location is beyond the boundary of actual contamination for substance Z(e.g.,
                       substance Z concentrations  from finfish samples are not applicable beyond SQ}.

               —      Similarly, substance X detected in finfish at Station D cannot  be used  because the
                       boundary for actual contamination besed on substance X ends at SQ.

               —      In this sample, Level I cannot be demonstrated by calculating I and J indices based on
                       finfish sample results.

Conclusion:    Therefore, the portion of the fishery between the PPE and SO, is evaluated based on Level II
               concentrations. The portion of the fishery between Sample SO, and the TDL is subject to potential
               human food chain contamination.
                                              303
                                                                                         Section 8.12

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TIPS AND REMINDERS

       In general, hazardous substance concentrations from edible tissue samples (i.e., fillets for most
       finfish, soft tissue for mussels and oysters) are preferred for evaluating the level of actual
       contamination.

       When evaluating fisheries in brackish water, use the higher BPFV (i.e., salt water or fresh water
       value) when determining actual contamination.

       Use only BPFVs associated with those substances that establish an observed release to
       surface water to determine if actual human food chain contamination exists.

       If an observed release is based on chemical analysis, analytical results for comparing release
       to background must be from the same medium (e.g., sediment samples should be compared
       with sediment samples; aqueous samples should be compared with aqueous  samples).

       An observed release is a necessary but not sufficient condition for establishing actual human
       food chain contamination.

       Not all aquatic human food chain species can be used to establish an observed release to
       surface water; however, all aquatic human food chain species can be used to establish Level
       I contamination if an observed release is already established (by use of other sample types).

       Finfish tissue  samples (and samples from any non-sessile or non-benthic organisms) cannot
       establish an observed release or actual contamination by themselves.

       When documenting actual contamination of a closed fishery, a BCFV of 500 or greater is not
       required if the substance being used to establish the observed release (and actual
       contamination) Is one for which the fishery was closed.

       Consider analytical results from tissue samples from non-benthic or non-sessile human food
       chain organisms only if they are collected in  an area of actual contamination.

       Assign a minimum hazardous waste quantity factor value of 100 for the human food chain
       threat if a fishery is subject to actual contamination and Tier A is not adequately determined.

       Direct observation cannot  be used to establish Level I concentrations.

       Because no aqueous or sediment benchmarks exist for evaluation of the  food chain threat,
       surface water and sediment samples cannot be used to establish Level I  concentrations.

       Tissue samples from non-sessile and non-benthic human food chain organisms can only be
       used to establish Level I concentrations in an area of actual human food  chain contamination
       established by other samples.

       When using tissue sample results from essentially sessile benthic human food chain
       organisms to evaluate Level  I or Level II concentrations, establish background levels using
       similar organisms of the same species.
Section 8.12                                    304

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SECTION  8.13
HUMAN FOOD CHAIN
PRODUCTION
       This section provides guidance on estimating human food chain production for fisheries within
the surface water TDL. Human food chain production can be estimated based on production data or
stocking rate data. In order to assign a human food chain population value from MRS Table 4-18,
estimates must be expressed in pounds of edible species or organisms harvested annually from  a portion
of the fishery subject to a specific level of contamination - Level I concentrations, Level II
concentrations, and  potential human food chain contamination. Guidelines are provided to determine
when it is necessary and efficient to score the human food chain population factor.
          Section 4.1.3.3
          Section 4.1.3.3.2
          Section 4.1.3.3.2.1
          Section 4.1.3.3.2.2
          Section 4.1.3.3.2.3
RELEVANT MRS SECTIONS


    Human food chain threat - targets
    Population
    Level I concentrations
    Level II concentrations
    Potential human food chain contaminiation
DEFINITIONS
       Actual Contamination for the Human Food Chain Threat: Any portion of a fishery is subject
       to actual contamination if a hazardous substance with a BPFV of 500 or greater meets the
       criteria for an observed release; a fishery is closed, and a hazardous substance for which the
       fishery was closed is documented in an observed release; or a hazardous substance is present in
       a tissue sample from an essentially sessile, benthic food chain organism at a level that meets
       the criteria for an observed release.

       Actual Human Food Chain Organism: Aquatic species directly consumed by humans,
       including certain finfish, shellfish, crustaceans, amphibians, and amphibious reptiles.

       Fishery: Any area of a surface water body from which human food chain organisms are taken
       or could be taken for human consumption on a commercial, recreational, or subsistence basis.
       Food chain organisms include fish, shellfish, crustaceans, amphibians, and amphibious reptiles.
       Fisheries are delineated by changes in dilution weights, level of contamination, or annual
       production. To establish a fishery, document that human food chain organisms are present and
       that people fish  in the surface water body.

       Production:  Estimate of annual pounds of human food chain organisms harvested for human
       consumption through all activities, including commercial, recreational, and subsistence fishing.
       Often times, production can be determined from harvest, catch, or commercial landings data, if
       the reported data refer only to human food chain organisms.
                                          305
                                                                                Section 8.13

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       Productivity: Common surrogate for yield data, often expressed as pounds of human food
       chain organisms present per acre per year. Productivity data are not equivalent to production
       estimates and generally are not used for MRS purposes.

       Standing Crop:  Biomass of all human food chain organisms in a given area of a surface water
       body at one time. Standing crop data are not equivalent to production estimates and generally
       are not used for MRS purposes.

       Stocking Rate:  Number of human food chain organisms (or pounds of human food chain
       organisms) per unit time introduced into a given surface water body by local, state, or Federal
       fishery agencies.

       Yield: Maximum  amount of human food chain organisms that could be caught by commercial,
       recreational, and  subsistence fishermen from a given water body. Yield is expressed as weight of
       human food chain organisms present per unit area (or volume) per unit time. Yield data are not
       equivalent to production estimates and generally are not used for MRS purposes.

ESTIMATING THE HUMAN FOOD CHAIN  POPULATION FACTOR

       This section provides lookup tables to determine the annual production required to assign  a
certain number of target points to the human food chain population factor. If a preliminary estimate of the
likely range of annual production (in pounds  of human food chain organisms) can be made, these tables
assist in determining the range of target points likely to be assigned after fully documenting a food chain
production value.

(1)     Evaluate actual contamination. If there is actual contamination within a portion of the fishery,
       the human food chain individual will score significantly (i.e., at least 45 points). Therefore,
       pursue production data not readily available only when production is expected to be
       significant (e.g., greater than 1,000 pounds/year).

              See Highlight B-52 to determine the level of production that would be needed to assign
              the indicated number of points to the human  food chain  population factor under actual
              contamination. A higher score may result when more than one fishery or several levels
              of contamination are present within the TDL.

(2)     Evaluate potential  contamination.  Potential human food chain contamination only contributes
       significantly to the human food chain threat target score when:

              High production in pounds per year is documented within the TDL; and

              A water body with  a large surface water dilution weight (e.g., minimal and small to
              moderate streams having average annual flows less than or equal to 100 cfs, closed
              lakes, or lakes with low flows entering or leaving) is being evaluated.

       In many circumstances, only one of these conditions will be present.  For example, oceans and
       Great Lakes generally  have large production levels, but they also have relatively small dilution
       weights (e.g., 0.0001 or less), greatly reducing  the target points. For a fishery with dilution weight
       of 0.0001 subject to potential contamination to receive more than 3 target points, annual
       production of more than 108 pounds would need to be documented.

              See Highlight 8-53 to determine the level  of production that would be needed to assign
              the indicated number of points to the human  food chain  population factor under potential
              contamination. The highlight focuses on a  single fishery evaluated under potential
              contamination. A higher score may result when more than one fishery or several levels
              of contamination are present within the TDL. However, the score is

Section 8.13                                    306

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rep
ass
HIGHLIGHT 8-52
VALUES FOR HUMAN FOOD CHAIN POPULATION FACTOR
GIVEN ACTUAL CONTAMINATION IN A FISHERY
Factor Values for Human
Food Chain Population3
0.03
0.30
3.00
30.00
31.00
310.00
3,100.00
31,000.00
310,000.00
3,100,000.00
31,000,000.00
Annual Production in Pounds
Required - Level I
Not Applicable
>0to 102
>102to 103
>103 to 104
Not Applicable
>104to 105
>105to 106
>106to 107
>107to 108
>108to 109
>109
Annual Production in Pounds
Required - Level II
>0to 102
>102to 103
>103to 104
Not Applicable
>104to 105
>105to 106
>106to 107
>107to 108
>108to 109
>109
Not Applicable

aAssumes a single fishery and a single level of actual contamination. Note that these values do not
resent assigned values from Table 4-18; they represent the factor value for Level I or Level II which is the
igned value multiplied by 10 for Level I, or the assigned valued multipled by 1 for Level II.
                not likely to be significantly higher if all fisheries are evaluated based on potential contamination.

        For many sites, expending extensive effort to evaluate fisheries subject to potential contamination when
        productivity data are not readily available may not be the most efficient use of resources.

(3)      Use the guidance below to document production. If the above assessment indicates that it is efficient
        to document human food chain production,  the subsections below present the generally preferred type of
        documentation first, followed by alternative approaches.

                Document production using site-specific data. Apportion that data to include only surface water
                bodies within the fishery being evaluated,  if necessary.

                Estimate production using surrogate data  (e.g., estimates of production from nearby fisheries with
                similar characteristics).

                If specific production data are not available and a reasonable estimate of production cannot be
                made,  use a production estimate of greater than 0 pounds per year to evaluate the human food
                chain population factor.
                                                   307
                                                                                               Section 8.13

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0
t\
s
HIGHLIGHT 8-53
VALUES FOR HUMAN FOOD CHAIN POPULATION FACTOR GIVEN
POTENTIAL CONTAMINATION IN A FISHERY
Factor Values for Human Food
Chain Population3
0.02
0.03
0.16
0.31
1.6
3.1
31
310
3,100
31,000
310,000
Dilution Weights
0.000005
1
0.1
0.01
0.001
0.0001
0.00001
0.000005
1
0.1
0.01
0.001
0.0001
0.00001
0.000005
1
0.1
0.01
0.001
0.0001
0.00001
1
0.1
0.01
0.001
0.0001
1
0.1
0.01
0.001
1
0.1
0.01
1
0.1
1
Annual Production in
Pounds Required
>107-108
>102-103
>103-104
>104-105
>105-106
>106-107
>107-108
>108-109
>103-104
>104-105
>105- 106
>106-107
>107-108
>108-109
>109
>104-105
>105- 106
>106-107
>107-108
>108-109
>109
>105-106
>106-107
>107-108
>108-109
>109
>106-107
>107-108
>108 -109
>109
>107-108
>108-109
>109
>108-109
>109
>109

aAssumes a single fishery and a single level of potential contamination. Note that the dilution weight of
.5 is not used for the population factor. Note that these values do not represent assigned values from Table 4-1 8;
ley represent the factor value for potential contamination which is the assigned value multiplied by the applicable
urface water body dilution weight multiplied by 0.1.
Section 8.13
                                                    308

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DETERMINING PRODUCTION USING SITE-SPECIFIC DATA

(1)     Collect available data. Collect data on fishery production within the TDL. General data
       sources are listed \r\Highlight8-54. Additional information on the types of data typically
       available from NMFS is detailed in Highlight 8-55.

              Confirm that the data collected represents the fish biomass removed from the water
              body that is used for human consumption. In heavily fished areas, production data
              (commercial, recreational, and/or subsistence) needed for evaluating population often
              will be available.

              Review units associated with production data. If available production data are reported in
              numbers or pounds harvested per hour, attempt to convert these into pounds harvested
              per year  by using estimates of average weight per organism and/or total number of hours
              the water body is fished per year.

              Select data from an appropriate time frame. Depending on the records available, annual
              production may be best represented by an average of data from several years. However,
              if data are available for only a few non-consecutive  years,  (e.g., 1967 and 1985), it may
              be appropriate to use only the more recent production.

              Avoid relying on data sources that do not represent a reasonable estimate of annual
              production from a specific surface water body.

              —     Creel surveys of recreational and subsistence fishing may be available where
                     fishing is substantial and, therefore, likely to be studied  by state agencies
                     involved in managing fishery resources. The creel survey is aimed at obtaining
                     broad information on fishing trends such as kinds of fishing, amount of time
                     spent fishing, species and size offish caught. Because creel surveys are not
                     performed routinely, they are frequently outdated.

              —     Local fish consumption  rates are generally not relevant because it is the amount
                     offish consumed from a specific water body that is of interest, not the total
                     amount offish consumed by individuals in the vicinity of the site.

              —     If the fishery management technique has changed (e.g., a stream is no longer
                     stocked by the state), production data from  earlier time periods may not be
                     representative.

              If conflicting production estimates are generated from different sources, select the most
              defensible production data.

(2)     Apportion production data. If actual annual production data are available for the TDL, but
       include production for a portion of the surface water body not within the fishery being evaluated,
       apportion data to determine production within the TDL. Multiply the total production for the
       fishery by the ratio of the area of fishery being evaluated (or the length  of coastline) to the total
       area of the fishery (or length of coastline) for which production data were obtained.  There are
       several circumstances where apportioning may be necessary:

              Production data are given for a  stretch of river, only a portion of which is within the TDL.
              See Highlight 8-56.

              Production data are available for a NMFS distance category (e.g., 3 to 12 miles
              offshore), and the fishery being evaluated does not extend the whole distance category
              (e.g.,  extends to 7 miles offshore). See Highlight 8-57.

                                             309                                    Section 8.13

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                                    HIGHLIGHT 8-54
                    SOURCES OF FISHERY PRODUCTION DATA

 Sources of information for production data for fresh water and marine habitats include:

        Literature searches (e.g., published reports) from FWRS. The FWRS receives materials
        regarding fresh water habitats from Federal, state, and private sources, including: Federal Aid
        in  Fish and Wildlife Restoration Program; Anadromous Sport Fish Conservation Program;
        Cooperative Fish and Wildlife Units; State Game and Fish Agencies; and Endangered Species
        Grants Program;

        NMFS, NOAA, U.S. Department of Commerce;

        Dingell-Johnson State Fish Chiefs and their staffs-these personnel coordinate and conduct
        fishery surveys with funding established under the Federal Aid In Fish and Wildlife Restoration
        Program;

        State Game and Fish Departments, and Parks and Recreation Departments;

        Local fishery laboratories;

        USFWS; and

        University biology departments which may have field research labs,  and may also have
        specialists in ichthyology or fish management.

 Additional  sources of Information for production data for fresh water habitats Include:

        Local Office of Bass Unlimited, Trout Unlimited, and other associations;

        SCS (stocks and maintains small impoundments);

        Associations and Commissions (e.g., Sport Fishing Institute);

        River Basin Commissions; and

        National Sport Fishing Federation (NSFF).

 Additional  sources of Information for production data for marine habitats Include:

        Sea Grant Advisory Service, NOAA; and

        Great Lakes Fish Commission.
Section 8.13                                    310

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                                     HIGHLIGHT 8-55
           PRODUCTION  DATA TYPICALLY AVAILABLE FROM NMFS

Salt Water Fishery Production - Commercial Fisheries

NMFS maintains and updates annually extensive data bases on commercial and recreational marine production.
Commercial data are kept for inland marine areas such as estuaries and bays, as well as for offshore areas.
For most coastal states, these data are provided  for three distance categories, and as state and  country
landings. The distance categories are:

        0 to 3 miles offshore

        3 to 12  miles offshore

        12 to 200 miles offshore

Because commercial marine data are often reported as landings (i.e., the numbers or pounds of human food
chain organisms brought to a port), data on commercial landings by state and by county do not indicate where
the human food chain  organisms were actually caught. For example,  human food  chain organisms caught off
the Texas coast  might be landed in Louisiana and reported as Louisiana landings. As a result, the geographic
location associated with commercial catch data may bear only a tenuous relationship to the locations where the
human food chain organisms were harvested or caught.       However, commercial landings data forthe county
(or counties) that a fishery Is located adjacent to orcontiguous with can generally be used for up to 12 miles
offshore. Human food chain organisms landed but not caught in the county are assumed to be offset by human
food chain organisms  caught in the county but landed elsewhere. Production data for 0 to 3 miles and 3 to 12
miles, therefore, are often         representative for  a particular area of interest.

Commercial data from NMFS are available for finfish and shellfish.  For shellfish, data are  available  on live
weight (i.e., weight with the shell) and on meat weight  (i.e., weight without the shell). For commercial shellfish
harvest data, use the meat weight and only the proportion of the county commercial production that is used for
human consumption to estimate human food chain production. If only  the live weight is available, use this data
as a reasonable production estimate.  NMFS data  are sometimes broken down  by  end-use disposition, for
example, human consumption, bait, animal food, and reduction to meal and oils. When possible, determine the
proportion of the commercial harvest that is for human consumption.

Salt Water Fishery Production - Recreational Fisheries

Data on recreational production are available from NMFS for finfish from 0 to 3 miles offshore. However, these
data generally are reported as state or county totals and cannot be broken down by a  specific water body (e.g.,
by a bay or estuary) within the state or within a particular county. Because NMFS does  not maintain recreational
marine shellfish  production data, recreational production  data for shellfish are generally not available even
though this production can be significant and can equal or exceed the commercial production. Alternate sources
for recreational shellfish production are appropriate fish management officials.

Fresh Water Fishery Production - Recreational Fisheries

Data on recreational production are available from NMFS for finfish from fresh waters.  These  data are reported
by state, and generally are not broken  down by a specific water body within the state or within a particular
county.
                                                311                                        Section 8.13

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                                      HIGHLIGHT 8-56
               APPORTIONMENT OF PRODUCTION DATA IN A RIVER
                            Y>—Level I
                     Potential
                  Contamination
   Site Setting:    Spearfish Creek is a cold water fishery for both brown and brook trout, The average annual
                  recreational production for the entire length (approximately 35 miles) of Spearfish Creek is
                  250 pounds based on information provided by the State Department of Game, Fish, and
                  Parks.

   Level II
   Contamination: The fishery in approximately 2 additional miles of Spearfish Creek is subject to Level II
                  concentrations from the site based on Samples SED-01  and SED-02,
                  2 miles  =  0.0571
0.0571 x 250 Ibs/yr = 14 Ibs/yr
                  35 miles

                  Assigned human food chain population value = 0.03 (from MRS Table 4-18)

   Potential
   Production:     Approximately 13 miles of Spearfish Creek is within the surface water TDL and subject to
                  potential contamination.

                  13 miles  = 0.3714      0.3714 x 250 Ibs/yr = 93 Ibs/yr
                  35 miles

                  Assigned human food chain population value = 0.03 (from HRS Table 4-18)
Section 8.13
                                               312

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                                    HIGHLIGHT 8-57
        APPORTIONMENT OF PRODUCTION DATA ALONG A COASTLINE

 NMFS collects data on the total annual catch In pounds from the nearshore zone (i.e., Oto 3 miles from
 shore). To apportion this data when the TDL includes waters in the nearshore area, determine the tota
 acreage within that area for a state and divide the total annual catch for that state to derive production
 in pounds per acre. Multiply the acreage within the TIDL by this production figure and use the result a
 a production estimate.

 For example, New Hampshire has 13 miles of coastline. The nearshore zone, therefore, has 39 square
 miles (i.e,, 13 miles x3 miles) and 24,960 acres (i.e,, 39 square miles x640 acres/square mile). NMFS
 determined that 689,000 pounds of shellfish and fish were commercially captured in the 0- to 3-mile
 region in a recent year. Based on this data, the annual  catch Is approximately 28 pounds per acre.
 Assuming that the PPE Is along a portion of the shoreline that is straight (i.e., an arc with a 3-mile radius
 encompasses a semi-circle), approximately 9,000 acres are within the TDL, corresponding to a
 production of about 250,000 pounds per year. Additional  production could be determined using NMFS
 data in the 3- to 12-mile region  to estimate commercial landings and by documenting recreational
 production.
              State recreational marine production data are available for the whole state, and the
              production can be apportioned based on the length, of coastline within the TDL.

       It may also be necessary to apportion production so that a production value can be associated
       with each surface water body type and dilution weight (e.g., to account for changes in flow rate or
       depth when evaluating potential contamination), and portions of fisheries subject to potential,
       Level II or Level I concentrations.

(3)     Apply stocking rates. If annual production data are not available, a stocking  rate for the fishery
       may be used. Stocking data can provide an indication of food chain production when:

              The stocking is a put-and-take operation;

              The stocked fish population will be caught for human consumption; and

              The stocked fish population will be caught within the TIDL or within the boundaries of the
              fishery being evaluated.

       Appropriate stocking data have been used for places like Colorado and West  Virginia where trout
       are released for the spring fishing season and are usually all caught by early summer. Stocking
       data are usually not appropriate when yearlings or juveniles are released to maintain natural
       species balance or to build up populations after a decline.

(4)     Evaluate closed fisheries. For a closed fishery subject to actual  human food  chain
       contamination (i.e., when a hazardous substance for which the fishery or a portion of the  fishery
       was closed is documented in  an observed release to the fishery from the site), estimate fishery
       production based on data collected before the fishery was closed.

(5)     Sum all data. If data represent different types of fisheries (i.e., subsistence, commercial,  or
       recreational) or different species (e.g., finfish and shellfish), the production for each type  of
       fishery and species can be summed to determine the total production for the fishery being
       evaluated. For an example, see Highlight 8-58.

(6)     Evaluate fisheries with no production data. If neither annual production data nor stocking
       rates are available, continue with the guidance  in the next subsection.

(7)     Calculate the human food chain production factor. See Section 8.12.
                                             313                                    Section 8.13

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                                     HIGHLIGHT 8-58
              SCORING EXAMPLE FOR POTENTIAL CONTAMINATION

        Big River Is a fishery for four salmon species (chinook, chum, coho, and pink). The river Is about
        90 miles long when measured from its headwaters to coastal tidal waters (i.e., Deep Sound), and
        its average width Is 200 yards. Thus, the entire river covers an area of approximately 6550 acres.
        The TDL Includes 12 miles of Big River and 3 miles of Deep Sound. Each fishery is subject only
        to potential contamination and each Is associated with a different flow rate (i.e., Big River ranges
        from 9,600-9,900 cfs/year; Deep Sound is characteristic of coastal tidal waters).

        The state maintains production data for several stations along the Big River and one station falls
               within the TDL. The state fishery management official commented that the production for
        this station was not representative of the actual production within this portion of the salmon
        fishery. Thus, the  scorer apportioned annual  production associated with the entire river to the
        portion of the fishery within the TDL.

        The 10-year average total production for pink salmon Is about 200,000 fish/year, and all of these
        fish pass through in-water segment and spend an extended period of time within Big River. The
        average weight usable for human consumption of each adult pink salmon is  about 5.0 pounds.
        Thus, the annual production  for pink salmon within the  entire length  of the Big  River is
        approximately 1,000,000 pounds/year or roughly 150 pounds/acre-year.

        Since the 12 miles of Big River within the TDL covers about 870 acres.

        870 acres x 150 pounds/year-acre = 130,500  pounds/year

        This value equals the annual production for  pink salmon  within the TDL. Based on similar
        estimations for the other salmon species, the total annual production for the portion of the Big
        River within the TDL for all  four salmon species is  640,000 pounds. A human food chain
        population value of 310 is assigned from MRS Table 4-18.

        Annual production for the Deep Sound fishery was based on 5 years of commercial harvest data,
        and 3 years of recreational harvest data, Production estimates based on State Department of
        Fisheries recreational salmon management and catch reporting data were added to production
        from commercial harvest records provided by NMFS. The total annual production for Deep Sound
        is 2,300,000 pounds. A human food chain population value of 3,100 Is assigned from MRS Table
        4-18.

        Calculate annual  production for each fishery  separately, multiply by the appropriate dilution
        weight, sum, and multiply by 0.1 for potential human food chain contamination.

        Big River       310X0.001=0.31
        Deep Sound    3,100 X 0.0001 = 0.31
        Potential Human Food Chain Contamination Factor Value for the Watershed = 0.62X0.1 = 0.06

        This value of 0.06 represents the population factor value for the watershed since no fisheries were
        subject to actual contamination.
Section 8.13                                    314

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ESTIMATING PRODUCTION USING SURROGATE DATA

       If estimates of annual production data specific to the fishery are not available, estimate
production by collecting information for similar surface water bodies containing comparable fisheries.
Determine if the surrogate fishery (and the water body itself is similar to the fishery being evaluated in
terms of:
              Fish species or other human food chain organisms present (e.g., production data for a
              fishery consisting primarily of pike should not be used when evaluating a fishery
              consisting primarily of smallmouth bass);

              Flow rate (or depth for oceans);

              Characteristics (e.g., salinity, flow, depth, subsurface bottom, state classification, overall
              water quality);

              Distance from each water body to possible surrogate water body; and

              Fishing activities.

       Consider these criteria before assuming that production data from a similar water body can be
used for estimating production for the fishery (or portions of the fishery) within the TDL. State fish and
game officials are a likely source for such information. Document the rationale for using surrogate data
from another fishery for the fishery being evaluated.

       For example, production data for a fishery consisting primarily of trout could be used for a fishery
consisting of trout that is 30 miles away. The average annual flows of both water bodies should be similar
even though the surface water dilution weight assigned to each water body may be different (e.g., a
small to moderate stream may have a flow of 90 cfs (an assigned dilution weight of 0.1) while an
acceptable surrogate fishery may be a moderate to large stream having a flow of 140 cfs (an assigned
dilution weight of 0.01)). In  addition, the characteristics of both the surrogate water body and the water
body within the TDL should share similar attributes. Both should be either managed as a high quality
cold-water fishery or be managed as a limited warm-water fishery. Likewise, both should  be either
annually stocked and aggressively managed for sport fishing or not stocked.

ESTIMATING PRODUCTION WITHOUT ACTUAL OR SURROGATE  DATA

       If surface water is documented to be a fishery and production data (actual and surrogate) are not
available, assign the fishery a minimum  human food chain production of greater than 0 pounds per year.
Then, assign the fishery a human food chain population value of 0.03 based on MRS Table 4-18. Use
this human food chain population value to assign factor values for Level I concentrations, Level II
concentrations, and potential human food chain contamination. Show that the fishery supports human
food chain organisms by documenting that at least one human food chain organism lives within fishery
boundaries and that fishing occurs in the surface water body.
                                             315                                    Section 8.13

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TIPS AND REMINDERS

       To evaluate human food chain production:

       —      Determine the population factor value needed to significantly affect the site score.

       —      Review Highlights 8-52 and 8-53 to determine the annual production that would
               required to achieve this population factor value.

       —      Determine if such production is likely. If so, try to obtain production data from local
               officials. If unsure about the amount of annual production for a fishery, or about using a
               particular production surrogate value, ask the officials if such production is likely.

       —      If such production is  unlikely, or if production data are not readily available, either assign
               a value based on the level of contamination present using a production value of greater
               than 0 pounds per year or see below. For all fisheries scored using a production value
               greater than 0, assign a value  of 0.03 for human food chain population for that fishery.

       —      In many cases, evaluating production for those fisheries subject to potential
               contamination will not significantly affect the human food chain threat targets score;
               therefore, the minimum assigned value of 0.03 for the human food chain population
               factor does not  have to be used for evaluating a fishery subject to potential
               contamination. Instead, reference the absence of this information and indicate in the
               MRS documentation  record that no reasonable production estimate can be made at the
               time of scoring.

       For potential contamination,  do not use that the dilution weight for the 3-mile mixing zone in
       quiet flowing rivers; rather, assign the dilution weight based on average annual flow.

       In the absence of actual contamination, large productions are generally necessary to significantly
       affect the human food chain threat targets score. Therefore, pursue production data for potential
       contamination only if production for a particular water body is expected to be significant.

       For MRS purposes, standing crop measures or other productivity estimates are not used for
       estimating food chain production. These  estimates do not correlate well with production for
       various water body types, and are more reflective of biomass (weight of all living organisms in
       the water body), than of productivity. However, standing crop estimates may help check the
       validity and adequacy of actual production data,  particularly when there are large differences
       between standing crop and production data, or between several estimates of actual production
       data, Production data should always be smaller than standing crop.
Section 8.13                                     316

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SECTION 8.14
SENSITIVE  ENVIRONMENTS
       This section provides general guidance for evaluating sensitive environments in the surface
water pathway as well as specific guidance and examples for evaluating more complex situations in
which multiple sensitive environments overlap. Sensitive environments include those environments
described in MRS Table 4-23 - hereafter referred to as listed sensitive environments - and wetlands as
defined in 40 CFR 230.3. Assigning point values to sensitive environments is straightforward in most
cases. In other cases (e.g., when the boundaries of several sensitive environments overlap, or if more
than one designation may apply to a single environment), this determination  may be less obvious;
however, most scoring difficulties can be eliminated by treating each sensitive environment as a
separate, independent target. This section addresses only the pathway-specific information necessary to
evaluate sensitive environments in the surface water pathway. Specific definitions of sensitive
environments, sources of information, and steps for identifying sensitive environments are provided in
Appendix A. Guidance for determining level of actual contamination is presented in Section 8.15.
Wetlands are discussed  in more detail in Section 8.16.
        Section 2.5
        Section 2.5.1
        Section 2.5.2
        Section 4.1.4.3
        Section 4.1.4.3.1
        Section 4.1.4.3.1.1
        Section 4.1.4.3.1.2
        Section 4.1.4.3.1.3
        Section 4.1.4.3.1.4
RELEVANT MRS SECTIONS

 Targets
 Determination of level of actual contamination at a sampling location
 Comparison to benchmarks
 Environmental threat - targets
 Sensitive environments
 Level I concentrations
 Level II concentrations
 Potential contamination
 Calculation of environmental threat - targets factor category value
DEFINITIONS
       Actual Contamination for Listed Sensitive Environments: Any portion of a listed sensitive
       environment is subject to actual contamination if it falls within an area that meets the criteria for
       an observed release. Direct observation and/or analytical data from aqueous, sediment samples,
       or essentially sessile benthic organism may be used to establish actual contamination. However,
       only surface water samples may be used to establish Level I concentrations.

       Listed Sensitive Environment: Areas that are evaluated as one or more of the sensitive
       environments  listed  in MRS Table 4-23, even if these areas (or portions of these areas) also are
       being evaluated as a wetland. The distinction is necessary because a wetland that is also a listed
       sensitive environment (e.g., a wetland area that also is habitat known to be  used by an
       endangered species) would be evaluated as two separate sensitive environments. Point values
       are assigned differently for wetlands than for the other types of sensitive environments.
                                            317
                                                                                  Section 8.14

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       Sensitive Environment In the Surface Water Pathway A sensitive environment is defined as
       a wetland (as defined in 40 CFR 230.3) or any area that meets the criteria listed in MRS Table
       4-23. No  other areas are considered sensitive environments for the surface water pathway.

SENSITIVE ENVIRONMENTS  ELIGIBLE TO BE EVALUATED IN THE SURFACE
WATER PATHWAY

       All areas  that are located along the hazardous substance migration path for a watershed and that
meet the definition for a wetland and/or at least one category listed in MRS Table 4-23 are eligible to be
evaluated in the surface water pathway for that watershed. In all cases, surface water sensitive
environments (including wetlands) along or contiguous to the hazardous substance migration path are
eligible. In some cases, terrestrial sensitive environments (as defined in MRS Table 5-5), or the terrestrial
portions of sensitive environments, also are eligible to be evaluated in the surface water pathway.

              Terrestrial sensitive environments not defined by the presence of one or more particular
              species (e.g., wildlife refuges) and whose boundaries cross or border a surface water
              body within the TDL are always eligible to be evaluated in the surface water pathway.

              Terrestrial sensitive environments defined by the presence of one or more particular
              species (e.g., habitat known to be used by an endangered or threatened species,
              terrestrial areas used for breeding by large or dense aggregations of animals) and whose
              boundaries cross or border a surface water body within the TDL are eligible to be
              evaluated in the surface water pathway unless there is clear information that the
              particular species of concern is unlikely to come Into contact with surface water bodies
              within the TDL.

              Terrestrial sensitive environments defined by the presence of one or more particular
              species and whose boundaries do not cross or border a surface water body within the
              TDL are eligible to be evaluated in the surface water pathway only if there is clear
              information that the particular species of concern is likely to come into contact with
              surface water bodies within the TDL.

       Additional guidance for determining if terrestrial sensitive environments are eligible to  be
evaluated in the surface water pathway is provided in Appendix A.

CALCULATING THE SENSITIVE ENVIRONMENTS FACTOR VALUE

(1)     Identify all listed sensitive environments within the TDL. For each sensitive environment,
       assign the appropriate point value from HFIS Table 4-23. See Appendix A for guidance in
       identifying sensitive environments. Use the following guidelines in identifying and assigning  point
       values to  each sensitive environment:

              Evaluate each discrete sensitive environment as a separate target, regardless of the
              degree to which it overlaps with other sensitive environments. For example, a critical
              habitat for an endangered species has the same point value whether located in a  state
              wildlife refuge or not; the wildlife refuge is evaluated as a separate sensitive
              environment in either case (see High light 8-59).
Section 8.14                                    318

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                                      HIGHLIGHT 8-59
             SCORING EXAMPLE FOR SENSITIVE ENVIRONMENTS
                                                                          TDL
                                                         Critical Habitat forth*
                                                         Fork Billed Frog Muncher
                                                            Critical Habitat for
                                                            the Green Fringed <
                                                            Elegentia
The above figure is a schematic map (not to scale) of the 15-mile TDL associated with a hypothetical site.
From background  documents and discussions with appropriate Federal and state agencies, the following
information is available:

The entire length of the river between the PPE and the TDL is a Federal designated Scenic River and is a state
designated area for the  protection of aquatic life.  The areas identified as Wetland A and B  are wetlands.
Wetland  B is also designated  as  Critical Habitat for the Green Fringed Elegentia, a hypothetical  Federal
designated plant species.  The labelled area delineated by large dashed lines is a designated State Wildlife
Refuge. The labelled area delineated by a continuous line is designated as Critical Habitat for the Fork Billed
Frog Muncher,  a hypothetical Federal designated endangered bird species whose diet consists entirely of
frogs.

Based on this information, and  by  referring to HRS  Tables 4-23 and  4-24,  seven  separate sensitive
environments are  identified:

•       The entire length  of the river between the PPE and the TDL is identified as a Federal designated
        Scenic River and  assigned a value of 50 points;
•       The entire length of the river between the PPE and the TDL is also identified as a state designated
        area for the protection of aquatic life and assigned a value of 5 points;
«       Wetland A is identified as a wetland and will be assigned a point value based on  its total linear
        frontage with the river and the levels of contamination under which it is evaluated (see  Section 8.16);
•       The area delineated by dashed lines is identified as a designated State Wildlife Refuge and assigned
        a value of 75 points;
        The area  delineated by a continuous line is identified  as Critical Habitat for a Federal designated
         endangered species and  assigned a value of 100 points;
        Wetland  B is identified as a wetland and will be assigned a point value based on  its total linear
        frontage with the river and the level(s) of contamination under which it is evaluated (see Section 8.16);
«        Wetland  B is also identified as Critical Habitat for a  Federal  designated threatened species and
         assigned  a value  of 100 points.

These seven sensitive environments are  illustrated further on the following page.

                                     (continued on next page)

                                               319
                                                                                             Section 8.14

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                            HIGHLIGHT 8-59 (continued)
              SCORING EXAMPLE FOR SENSITIVE ENVIRONMENTS
                                                               TDL
          Sensitive Environment
    PPE
    PPE
        Designation
1)  Federal designated Scenic
   River
2)  Designated area for the
   maintenance of aquatic life
                                     3) Wetland
                                     4) State Wildlife Refuge
                                     5) Critical Habitat for the Fork
                                       Billed Frog Muncher
                                     6) Wetland


                                     7) Wetland as Critical Habitat for
                                       the Green Fringed Elegentla
Assigned Value


          50
                               Dependent on
                               linear frontage
                                        75
                                       100
                               Dependent on
                               linear frontage
Section 8.14
                                             320

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              Evaluate "critical habitat for" or "habitat known to be used by" endangered or threatened
              species as follows:

               —     Identify at least one distinct habitat for each individual species (e.g., if there are
                      three different species, identify three or more habitats, even if they partially or
                      completely overlap (see Highlight 8-59)).

               —     For each individual species, assign only the endangered or threatened category
                      that results in the highest point value. For example, if the same species is both a
                      Federal proposed threatened species (75 points), and a state designated
                      endangered species (50 points), evaluate the species as a Federal proposed
                      threatened species for MRS scoring purposes.

               —     If both "critical habitat for" and "habitat known to be used by" the same species
                      occur within the TDL, consider each a separate sensitive environment for MRS
                      scoring purposes. However, if these areas overlap within the TDL, evaluate the
                      overlapping area only as "critical habitat for" the species (i.e., do not consider
                      the zone of overlap  as  both "critical habitat for" and "habitat known to  be used
                      by" the species). In other words, overlapping areas designated as "critical habitat
                      for" an endangered  or threatened species cannot also be evaluated as "habitat
                      known to be used by" the same species.

(2)     Evaluate level of contamination for each  listed sensitive environment. See Section 8.15 for
       guidance on determining level of actual contamination (see High light 8-60).

              Level I: Identify each listed  sensitive environment subject to Level I concentrations and
              sum their assigned point values (from MRS Table 4-23) to obtain the Level I value for
              listed sensitive environments.

              Level II:  Identify each listed sensitive environment subject to Level II concentrations  and
              sum their assigned point values (from MRS Table 4-23) to obtain the Level II  value for
              listed sensitive environments.

              Potential contamination:

              —      Identify each listed sensitive environment subject to potential contamination.

              —      Multiply its assigned point value (from MRS Table 4-23) by the appropriate
                      dilution weight (from MRS Table 4-13) for the surface water body within which
                      the sensitive environment is located.

              —      Sum these products to obtain the potential contamination value for listed
                      sensitive environments.

(3)     If wetlands are present, determine whether each discrete wetland should be  evaluated
       under Level I concentrations, Level  II concentrations, potential contamination, or a
       combination of these. See Section 8.15 for guidance on  determining level of contamination for
       wetlands. (Also see Highlight 8-60).

(4)     Determine the length of each discrete wetland evaluated under each level of
       contamination and assign the appropriate wetland rating value. Wetland scoring depends
       on size (i.e., linear frontage or perimeter) while all other sensitive environments are scored
       independently of their size. Guidance on determining wetland length under Level I
       concentrations, Level II concentrations, and potential  contamination is provided in Section  8.16.
                                             321                                     Section 8.14

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                                        HIGHLIGHT 8-60
        SCORING EXAMPLE FOR  LEVEL I AND LEVEL II CONTAMINATION
                                                                         TDL
                                                         Critical Habitat forth.
                                                         Fork Bi««d Frog Mundwr
                                                            Crftfeii Habitat for !
                                                            »• OfMn Fringtd j
                                Sample
                                Location
   The above figure is a schematic map (not to scale) of the 15-mile TDL associated with the same hypothetical
   site as illustrated in Highlight 8-59. In this example, however, analytic sampling results indicate that Level I
   concentrations are  present from  the  PPE to Point 1 (i.e., the  Level  I Sample Location), and  Level II
   concentrations are present from Point 1 to Point 2 (i.e., the Level II Sample Location).

   Based on the location of the sensitive environments within the TDL relative to the sampling points, they are
   scored under the following contamination levels:

   •       The length of the river between the PPE and TDL identified as a Federal designated Scenic River Is
          scored under Level I  concentrations (both Level I and Level II concentrations are present within this
          sensitive environment).
   •       The length of the river between the PPE and TDL identified as a state designated  area for the
          protection of aquatic life is scored under Level I concentrations  (see above).
   •       Wetland A is scored under both Level I and Level II concentrations as a result of its location relative
          to Point 1.  The length of Wetland A adjacent to the river upstream of Point 1 is scored under Level
          I  concentrations; the length of Wetland A adjacent to the river downstream of Point 1 is scored under
          Level II concentrations.
   •       The entire area identified as a State Wildlife Refuge is scored under Level II concentrations.
   •       The entire area identified as Critical Habitat for the Fork Billed Frog Muncher is scored under Level
          II concentrations.
   •       Wetland B, when being evaluated as a wetland,  Is scored under both Level II concentrations and
          potential contamination as a result of its location relative to Point 2. The length of Wetland B adjacent
          to the river upstream of Point 2 is scored under Level II concentrations; the length of Wetland B
          adjacent to the river downstream of Point 2 is scored under potential contamination.
   •       Wetland B, when being scored as critical habitat, is scored under Level II concentrations.

   These seven sensitive environments are illustrated further on the following page.

                                       (continued on next page)
Section 8.14
                                                   322

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                     HIGHLIGHT 8-60 (continued)
SCORING EXAMPLE FOR LEVEL I AND LEVEL  II CONTAMINATION
                                                           TDL
   Sensitive Environment
 PPE
 PPE
                     TDL
         Designation

1)  Federal designated Scenic
   River
2)  Area for the maintenance of
   aquatic life

3)  Wetland
Contamination Level

     Level I
                                                                  Level I
                                                           Level I upstream of Point
                                                           1, Level II downstream
                                                           of Point 1

                              4)  State Wildlife Refuge
                                    Level II
                              5)  Critical Habitat for the Fork
                                 Billed Frog Muncher
                              6)  Wetland
                                 Wetland as Critical Habitat for
                                 the Green Fringed Elegentia
                                    Level II
                             Level II upstream of
                             Point 2, potential
                             downstream of Point 2

                                    Level II
                                     323
                                                                            Section 8.14

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               Level I: Determine the total length of the wetlands subject to Level I concentrations, and
               assign the appropriate wetland rating value using MRS Table 4-24. Assign this value as
               the Level  I value for wetlands.

               Level II:  Determine the total length of the wetlands subject to Level II  concentrations,
               and assign the appropriate wetland rating value using MRS Table 4-24. Assign this value
               as the Level II value for wetlands.

               Potential contamination:

               —      Determine the total length of wetlands subject to potential contamination for
                      each type of surface water body (as defined in MRS Table 4-13).

               —      Based on this total length for each type of surface water body, obtain the
                      appropriate wetlands rating value using MRS Table 4-24.

               —      Multiply the wetlands rating value for each surface water body by the appropriate
                      dilution weight for the surface water body as defined in MRS Table 4-13.

               —      Sum these products and  assign this value as the  potential contamination value
                      for wetlands.

(5)     Calculate the Level I concentrations factor value, the Level II concentrations factor value,
       and the potential contamination factor value.

               Level I: Sum the assigned Level  I values for wetlands and listed sensitive environments
               and multiply that value by 10. Assign this value as the Level I concentrations factor
               value.

               Level II:  Sum the assigned Level II values for wetlands and listed sensitive
               environments and assign this value as the Level II concentrations factor value.

               Potential contamination:  Sum the assigned potential contamination values for wetlands
               and listed sensitive environments and divide that value by 10. If the result is one or
               greater, round to the nearest integer. If the result is less than one, do  not round. Assign
               this value as the potential contamination factor value.

(6)     Calculate the environmental threat-targets factor category value. Sum the factor values for
       Level I concentrations, Level II concentrations, and potential contamination. Assign this value as
       the environmental threat-targets factor category value.

TIPS AND REMINDERS

       Identify at least one separate sensitive environment (i.e., "critical  habitat for" or "habitat known
       to be used  by") for each endangered or threatened species, but assign only one category
       (e.g., Federal endangered, state threatened) to each  species.

       Designation of state threatened or endangered species are valid only within that state.

       A wetland area can be evaluated both as a wetland and as a listed sensitive environment
       (e.g., critical habitat).

       The minimum total wetland length within a given level of contamination or dilution category to
       obtain  a non-zero wetlands rating value from MRS Table 4-24 is 0.1  miles.
Section 8.14                                    324

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SECTION 8.15
LEVEL I  AND   Level  II
CONCENTRATIONS FOR
LISTED SENSITIVE
ENVIRONMENTS
       This section provides guidance for the types of observations, samples, and benchmarks used to
establish Level I or Level II concentrations and potential contamination for listed sensitive environments.
The sensitive environments factor value in the surface water pathway is assigned based on whether
sensitive environments within the TDL are considered subject to actual contamination (i.e., Level I or
Level II concentrations) or potential contamination, and on the assigned value for each sensitive
environment. In order to establish actual contamination, an observed release must be documented
(either by direct observation or by chemical analysis) for the location in the surface water body where
targets are present. To determine the level of actual contamination by chemical analysis, concentrations
of hazardous substances are measured in samples that meet the criteria for an observed release and
that are taken within, beyond, or adjacent to a sensitive environment within the TDL; these
concentrations are then compared to ecological-based benchmarks. Wetlands are discussed in more
detail in Section 8.17.
        Section 2.5
        Section 2.5.1
        Section 2.5.2
        Section 4.1.4.3
        Section 4.1.4.3.1
        Section 4.1.4.3.1.1
        Section 4.1.4.3.1.2
RELEVANT MRS SECTIONS

 Targets
 Determination of level of actual contamination at a sampling location
 Comparison to benchmarks
 Environmental threat - targets
 Sensitive environments
 Level I concentrations
 Level II concentrations
DEFINITIONS
      Actual Contamination for Listed Sensitive Environments: Any portion of a listed sensitive
      environment is subject to actual contamination if it falls within an area that meets the criteria for
      an observed release. Direct observation and/or analytical data from aqueous, sediment samples,
      or essentially sessile benthic organism may be used to establish actual contamination. However,
      only surface water samples may be used to establish Level I concentrations.

      Level I Concentrations for the Environmental Threat: Level I concentrations are established
      in aqueous samples in which the concentration of a hazardous substance that meets the criteria
      for an observed release is at or above the appropriate ecological-based benchmark.
      Benchmark for the environmental threat include AWQC and AALAC. I and J indices do not apply
      because there are no screening concentration benchmark for sensitive environments.
                                         325
                                                                             Section 8.15

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       Level II Concentrations for the Environmental Threat: Level II concentration are established
       in samples in which the concentration of at least one hazardous substance meets the criteria for
       an observed release, but the conditions for Level I  concentrations are not met. In addition, Level
       II is assigned for observed established by direct observation.

       Listed Sensitive Environment: Areas that are evaluated as one or more of the sensitive
       environments listed in MRS Table 4-23, even if these areas (or portions of these areas) also are
       being evaluated as a wetland. The distinction is necessary because a wetland that is also a  listed
       sensitive environment (e.g., a wetland area that also is habitat known to be used by an
       endangered  species) would be evaluated as two separate sensitive environments. Point values
       are assigned differently for wetlands than for the other types of sensitive environments.

       Observed Release: An observed release is established for the ground water, surface water, or
       air migration pathway either by chemical analysis or by direct observation. Observed release is
       not relevant to the MRS soil exposure pathway. The minimum requirements for establishing an
       observed release by chemical analysis are analytical data demonstrating the presence of a
       hazardous substance in the medium significantly above background level, and information that
       some portion of that increase is attributable to the site. The minimum criterion for establishing an
       observed release by direct observation is evidence that the hazardous substance was placed into
       or has been seen entering the medium.

DETERMINING LEVEL OF CONTAMINATION

       The following steps describe how to determine whether a listed sensitive environment is
considered  subject to Level I concentrations, Level II concentrations, or potential contamination.

(1)     Identify all listed sensitive environments within the TDL. Guidance for identifying and
       delineating listed sensitive environments is provided in Appendix A. Delineate the position and
       boundaries of these sensitive environments and their position relative to the hazardous
       substance migration path. It may be helpful to note these locations on a scale map or diagram.

(2)     Delineate all areas of actual contamination within the TDL. The procedures for delineating
       areas of actual contamination depend on whether actual contamination is established based on
       chemical analysis or direct observation.

               Delineate areas of actual contamination based on chemical analysis:

              —     For rivers and streams, the area of actual contamination is the area between the
                     PPE for a hazardous substance and the location of the farthest "hit" (i.e., the
                     farthest sampling location that meets the criteria for an observed release by
                     chemical analysis). At sites where there are multiple sources and PPEs, it may
                     be necessary to establish an area of actual contamination for each  hazardous
                     substance (i.e., the area between the PPE for that substance and the location of
                     the farthest "hit" for that substance). On a scale map or diagram, draw a line
                     from bank-to-bank at the appropriate PPE, and draw a second line from
                     bank-to-bank at the location of the  farthest "hit." The lines from bank-to-bank
                     should be drawn roughly perpendicular to both  banks. The portion of the river or
                     stream  between the two lines is the area of actual contamination for that
                     hazardous substance. In tidally influenced rivers and streams, the area of actual
                     contamination can be both upstream and downstream of the appropriate  PPE(s).

              —     For lakes, coastal tidal waters,  and oceans, the  area of actual contamination for
                     a hazardous substance is the area within an arc with a radius from the PPE for
                     that hazardous  substance to the location of the farthest "hit." At sites
Section 8.15                                     326

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                     where there are multiple sources and PPEs, it may be necessary to establish an
                     area of actual contamination for each hazardous substance. On a scale map or
                     diagram, draw an arc using the appropriate PPE as the center point and the
                     distance between this point and the location of the farthest "hit" as the radius.
                     Continue drawing this arc in each direction until it  reaches the shores of the
                     water body or completes a circle. The area within this arc is the area  of actual
                     contamination.

              Delineate areas of actual contamination based on direct observation. Actual
              contamination of a sensitive environment based on direct observation can be
              established at Level II concentrations if the observation is  made at some point within the
              sensitive environment. It may be helpful to note these locations on a scale map or
              diagram.

(3)     Delineate areas subject to Level I and Level  II concentrations within  areas of actual
       contamination based on chemical analysis. Delineate areas subject to Level I and Level II
       concentrations as follows:

              For each surface water sample location that meets the observed  release criteria,
              determine whether the sample location is considered subject to Level I or Level II
              concentrations as follows:

              —     If the concentration of any hazardous substance is equal to or greater than its
                     ecological-based benchmark, the sample location  is subject to Level  I
                     concentrations.

              —     If the concentrations of all  hazardous substances for which an applicable
                     benchmark is available are lower than their respective ecological-based
                     benchmarks, the sample location is subject to Level II concentrations.

              —     If none of the hazardous substances has an applicable benchmark, the sample
                     location is considered subject to Level II concentrations.

              Use EPA's AWQC and AALAC as the only ecological benchmarks, To determine the
              appropriate benchmark for the hazardous substance, use the lower of the applicable
              AWQC and AALAC values, if available, as follows:

              —     Use the chronic value; otherwise use the acute value.

              —     If the sensitive environment is in fresh water, use the fresh water value;
                     otherwise, use the marine value.

              —     If the sensitive environment is in salt water use the marine value; otherwise, use
                     the fresh water value.

              —     If the sensitive environment is in both fresh water and salt water, or is in brackish
                     water, use the lower of the applicable fresh water and marine values.

              For each sediment or benthic sample location, if any hazardous substance meets the
              criteria for an observed release, the location  is considered subject to  Level II
              concentrations. Sediment and benthic samples cannot be  used to establish Level I
              concentrations.

              Delineate areas subject to Level I concentrations as follows (if both fresh and brackish or
              salt water bodies are within the TDL, note the final two bullets in  Step (3) below):


                                             327                                     Section 8.15

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              —      For rivers and streams, the area subject to Level I concentrations is the area
                      between the PPE and the location of the farthest sample location subject to
                      Level I concentrations. On a scale map or diagram, draw a line from bank-to-
                      bank at the farthest location subject to Level I concentrations. The portion of the
                      river or stream between the two lines at the appropriate PPE (see Step (2)
                      above)  is the area subject to Level  I concentrations.

              —      For lakes, coastal tidal waters, and oceans, the area subject to Level I
                      concentrations generally is the area within an arc with a radius from the PPE to
                      the farthest location subject to Level I concentrations. On a scale map or
                      diagram, draw an arc using the appropriate PPE as the center point and the
                      distance between this point and the farthest location  subject to Level  I
                      concentrations as the radius. Continue drawing this arc in each direction until it
                      reaches the shores of the water body or completes a circle. The area within  this
                      arc is the area subject to Level I concentrations.

              Delineate areas subject to Level II concentrations as follows  (if both fresh and brackish
              or salt water bodies are within the TDL,  note the final two bullets in Step (3)):

              —      For rivers and streams, the area subject to Level II concentrations generally is
                      the area between the location of the farthest sample  location that is considered
                      subject to Level I concentrations and the location of the farthest sample location
                      considered subject to Level II concentrations (i.e., the area of actual
                      contamination that is not considered subject to Level I concentrations). The
                      portion  of the river or stream between the line at the farthest sample location
                      subject to Level I concentrations (see above) and the line at the farthest sample
                      location that meets the criteria for an observed release (see Step (2) above) is
                      the area subject to Level II concentrations.

              —      For lakes, coastal tidal waters, and oceans, the area subject to Level II
                      concentrations generally is the area between the arc drawn through the farthest
                      sampling location considered subject to Level I concentrations (see above) and
                      the arc  drawn through the farthest sample location considered subject to actual
                      contamination (see Step (2) above). The area within  these two arcs is the area
                      considered subject to Level II concentrations.

              If the listed sensitive environments within the TDL are present in, or adjacent to, both
              fresh water and brackish or salt water, then it may be necessary to establish separate
              areas of Level I and Level  II concentrations for the fresh water and the brackish or salt
              water. For some hazardous substances, the marine ecological-based  benchmark is lower
              than the fresh water benchmark. Thus it is possible for areas subject to Level I
              concentrations  (based on the marine benchmark) to be farther from the PPE than areas
              subject to Level II concentrations (based on the fresh water benchmark).

              If the stream or river is tidally influenced, see Section 8.1.

(4)     Determine which listed sensitive environments are considered subject to Level I
       concentrations, Level  II concentrations, and potential contamination. Level of
       contamination for each  listed sensitive environment is determined by the relative position of its
       boundaries to areas subject to Level I and Level II concentrations. Determine the appropriate
       level of contamination for each listed sensitive environment within the TDL as noted below.

              If any portion of the listed sensitive environment falls within an area considered subject
              to Level I concentrations, the entire sensitive environment is  considered subject to Level
              I  concentrations.


Section 8.15                                    328

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               If any portion of the listed sensitive environment falls solely within an area subject to
               Level II concentrations (or actual contamination), the entire sensitive environment is
               considered subject to Level II concentrations.

               If no portion of the listed sensitive environment falls within an area of actual
               contamination (i.e., Level I or Level II concentrations), the sensitive environment is
               considered subject to potential contamination.

               If any portion of the listed sensitive environment is considered subject to both Level I
               and Level II concentrations (or potential contamination), evaluate the sensitive
               environment under Level I concentrations. For example, if one portion of a National Park
               is within an area considered subject to Level I concentrations, and another portion  of the
               Park is within an area considered subject to Level II concentrations, the entire National
               Park is considered subject to Level I concentrations.

TIPS AND REMINDERS

       Direct observation can establish Level II concentrations for a sensitive environment, but only if
       the observation is within the boundaries of the sensitive environment.

       Surface water samples can be used to establish both Level I and Level II concentrations;
       sediment and benthic samples can  be used only to establish Level II concentrations.

       Only those hazardous substances that meet the criteria for an observed release at a surface
       water sample location should  be compared to ecological-based benchmarks.

       Level I concentrations for a sensitive environment cannot be established using the I or J  index.

       If any portion of a listed sensitive environment is considered subject to a given level of
       contamination, the entire sensitive environment is considered subject to that level of
       contamination. Only wetland scoring is based on the size of the sensitive environment subject to
       a particular level of contamination.

       If a listed sensitive environment can be considered subject to more than one level of
       contamination, evaluate that sensitive environment under the level of contamination that will
       result in the highest targets factor value (i.e., evaluate it under Level I concentrations, if possible;
       otherwise, under Level II concentrations, if possible; otherwise, under potential contamination).

       Any samples (surface water, sediment, or benthic) taken within, adjacent to, or beyond a
       sensitive environment can establish actual contamination.

       The area of actual contamination in the environmental threat will be identical to that in the
       drinking water threat. However, the areas of Level I and Level II concentrations within the area of
       actual contamination may differ between the two threats and will need to be established
       separately. The area of actual contamination in the human food chain threat may differ from that
       in the drinking water and environmental threats (e.g., if the hazardous substance that establishes
       actual contamination has a BPFV of less than 500, actual contamination may not be established
       for the human  food chain threat).

       If sensitive environments for the site are present in both fresh water and salt or brackish water,
       then areas of Level I and Level II concentrations may need to be established separately for the
       fresh water and the salt or brackish water bodies.
                                              329                                     Section 8.15

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SECTION 8.16
WETLANDS
       This section provides guidance to assist the scorer in identifying wetlands, evaluating wetlands,
and developing effective scoring strategies for wetlands. The guidance in this section is limited to
considerations for the surface water pathway (environmental threat). In the environmental threat,
wetlands are evaluated based on level of contamination (i.e., Level I, Level II, or potential) and size (i.e.,
length or perimeter of wetland area subject to a given level of contamination). To evaluate wetlands, the
scorer should document the presence of all wetlands within the TDL, delineate their boundaries
sufficiently so that length or perimeter may be estimated, and determine what portions of each wetland
are considered subject to Level I concentrations,  Level II concentrations, or potential contamination.
        Section 4.0.2
        Section 4.1.4.3
        Section 4.1.4.3.1
        Section 4.1.4.3.1.1
        Section 4.1.4.3.1.2
        Section 4.1.4.3.1.3
RELEVANT MRS SECTIONS

 Surface water categories
 Environmental threat - targets
 Sensitive environments
 Level I concentrations
 Level II concentrations
 Potential  contamination
DEFINITIONS

       Wetlands: Generally include swamps, marshes, bogs, and similar areas. As defined in 40 CFR
       230.3, wetlands are those areas that are inundated or saturated by surface or ground water at a
       frequency and duration sufficient to support, and that under normal circumstances do support, a
       prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands can be
       natural or man-made. Wetlands identified using other definitions (e.g., the Food Security Act of
       1985, the wetlands classification system of the U.S., the 1989 Federal Manual for Identifying and
       Delineating Jurisdictional Wetlands) are not eligible  unless they also meet the 40 CFR 230.3
       definition. A discussion of the wetland classification system used on NWI maps and its
       relationship to the 40 CFR 230.2 definition is provided in Appendix A.

IDENTIFYING AND DELINEATING WETLANDS

       Identify and delineate wetlands using readily available maps, brief written documentation (e.g., a
statement that hydrophytic vegetation is present), or photographs. If historical data document the
presence of a wetland (e.g., an old topographic map), and the SI shows that the wetland no longer exists,
score the wetland if it was eliminated because of activity related to the site. However, the wetland should
not be scored if it was eliminated for reasons not related to the site.
                                           331
                                                                                  Section 8.16

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       There are two common methods to identify and determine the length (or perimeter) of wetlands
subject to actual or potential contamination:

              Using maps (e.g., National Wetland Inventory maps, USGS topographic maps, Soil
              Conservation Service (SCS) soil maps) or other documentation (e.g., aerial photo); and

              Contacting a wetlands expert to delineate the wetlands.

       For most wetland evaluations, NWI maps can support reasonable estimates of the presence and
boundaries of wetlands. However, wetlands identified on these maps may not meet the definition of a
wetland as stated in 40 CFR 230.3 and may not be eligible for MRS scoring (see Appendix A). When
wetlands may significantly impact the site score (i.e., result in a site score greater than 28.50), further
documentation may be needed to show that the wetlands meet the definition in 40 CFR 230.3
(documentation may include contacting a wetlands expert to delineate the wetlands).

DETERMINING WETLAND SIZE (LENGTH OR PERIMETER)

       To develop a targets score for the environmental threat pathway, the scorer must assess the
length or perimeter of all wetlands within the TDL. Common situations for which the scorer determines
wetland length include:

              Wetlands contiguous to a river or stream (see High light 8-61);

              Wetlands contiguous to a lake, coastal tidal water, or ocean (seeHighlight 8-62);

              A watershed with wetlands contiguous both to a river and to a lake or ocean  (see
              Highlight 8-63); or

              Wetlands divided by a stream or river (see Highlight 8-64).

Common situations for which the scorer determines wetland  perimeter include:

              Isolated wetlands (seeHighlight 8-65); or

              Wetlands where the PPE into surface water is in the wetland (seeHighlight 8-65).
Section 8.16                                    332

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                           HIGHLIGHT 8-61
   DETERMINING  LENGTH FOR WETLANDS ALONG A RIVER
                How
                                            Wetland 3
  Wetland 1
                         Wetland 2
The length of wetlands along a river or stream is determined by the frontage of wetlands contiguous
to the waterway. The distance should be measured as the actual shoreline (frontage) distance and
not the straight-line distance between the upstream and downstream points where the wetland meets
the surface water body.  In this example:

—     Frontage for Wetland 1 is the distance A to C, not the distance A to B to C,
—     Frontage for Wetland 2 is the distance H to I to J, not the distance H to J.
—     Length for Wetland 3 is the distance D to E.
                                    333
                                                                            Section 8.16

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                                      HIGHLIGHT 8-62
       DETERMINING LENGTH FOR WETLANDS ALONG A LAKE,  COASTAL
                                TIDAL WATER, OR OCEAN
                  Example 1
Example 2
           In Example 1, the arc A-G (15-mile radius) centered on the coastline length to be considered.

           The length of wetlands to be considered Is the sum of wetlands within the arc.  Length of wetlands
           should be determined as the coastline length and not a straight-line distance.  For this example the
           following should be considered:

           —      Frontage for Wetland 1 (the distance A to B to C); and
           —      Frontage for Wetland 2 (the distance D to E to F).

           In Example 2, the arc H-K (15-mile radius)  centered on the PPE is drawn to determine the coastline
           length to be considered.

           The length of wetlands to be considered is the sum of wetlands within the arc.  Length of wetlands
           should be determined as the coastline length and not a straight-line distance. For this example, the
           following should be considered:

           —      Frontage for Wetland 4 (the distance L to M to N); and
           —      Frontage for Wetland 6 (the distance I to J to K).

Section 8.16
                                                334

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                          HIGHLIGHT 8-63
  DETERMINING LENGTH FOR WETLAND IN A WATERSHED
    WITH A RIVER AND LAKE, OR COASTAL TIDAL WATER
The wetlands frontage is calculated as the sum of the length of wetlands contiguous to the river
portion of the hazardous substance migration pathway and the length of wetlands contiguous to the
coastline in the lake or ocean.

In this example, the total length of wetlands is equal to the length of wetlands associated with the river
and the length of wetlands associated with the coastline within the TDL. The radius of the arc into the
lake or ocean should be  drawn from the center of the river emptying into the lake or ocean and is
equal to the TDL (15 miles) minus the length of the TDL in the river or stream (in this example, 10
miles). The following lengths of wetlands should be included:

—      The distance of  wetlands along the river, A to B to C and D to E to F; and
—      The distance of  wetlands along the coastline within the TDL, G to H to I and K to L to M.
                                   335
                                                                           Section 8.16

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                                      HIGHLIGHT 8-64
          DETERMINING LENGTH FOR WETLAND DIVIDED BY A STREAM
                                                  2.7 miles
1
       Stream P
                                                   2.3 miles
          Stream Q
           For surface water systems with no discernible flow (e.g., a defined channel) through a wetland, the
           perimeter of the wetland should be considered the wetland length.

           For all surface water systems with a discernible flow through a wetland, the wetlands on opposite
           banks of the  stream should be considered as two wetlands.  The length  of wetland should be
           determined for both sides of the water body and  added together when determining total length of
           wetlands.

           In this example, Stream P has no discernible flow through the wetland, and, therefore, the perimeter
           of the wetland (5 miles) should be considered the length.  However, in Stream Q, the stream has a
           discernible continuous flow through the wetland, and therefore lengths E to F and G to H should be
           considered as two separate wetlands with a length of 8 miles (4 miles each).
Section 8.16
                                                336

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                             HIGHLIGHT 8-65
            DETERMINING PERIMETER OF A WETLAND
WHEN THE PROBABLE POINT OF ENTRY IS IN THE WETLAND
            Wetland 1
                            Wetland 2
        Example 1
Example 2
For isolated wetlands or wetlands where the PPE into the surface water body is the wetland, the
perimeter of the wetland is used for wetland length rather than the frontage contiguous with the in-
water segment of the hazardous substance migration path.

In Example 1, the PPE is within a perennial, isolated wetland. The scorer should do the following:

—      Measure from the PPE to the end of the TDL and draw an arc.
—      If the boundaries of the isolated wetland are entirely within the arc, the total perimeter should
        be used as the wetland length.
—      If the wetland is not completely within the arc,  measure the perimeter of the wetland within
        the arc and the length of the arc to determine the wetland length.
—      If the wetland is entirely within the TDL, sum the overland distance from the source to the
        isolated wetland, the distance of the hazardous substance migration pathway within the
        isolated wetland, and the overland distance from the isolated wetland to the next surface
        water body.  If this distance is greater than 2 miles, evaluate only the isolated wetland.
—      If the sum  of these distances is less than 2 miles, evaluate the next surface water body as
        a separate watershed.  Remember to evaluate the hazardous substance migration path, not
        the straight-line distance.

In Example 1, if distance A is less than 2 miles and the total perimeter of Wetland 1 is within the 15-
mile TDL, the entire  perimeter is used as the wetland length. If the sum of distances A, B (the shortest
distance from the PPE to the hazardous substance migration pathway from the wetland), and C is
less than 2 miles, evaluate Wetlands 1 and 2 as two separate watersheds (i.e., draw a 15-mile TDL
in each wetland). If  the distance is greater than 2 miles, evaluate only Wetland 1. Continue evaluating
the overland distance until the sum of distances for the hazardous substance migration pathway is
greater than 2 miles.

In Example 2, the PPE is in an isolated wetland. The 15-mile TDL is completely within the wetland.
The length of wetland to be considered is the perimeter distance ABDCA (i.e.,  the length of the arc
in the wetland and  the perimeter of wetland bisected by the arc), assuming the entire wetland is
subject  to the  same level of contamination (for wetlands with various levels of contamination, see
Highlight 8-68).
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                                                                                  Section 8.16

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ESTABLISHING ACTUAL AND POTENTIAL CONTAMINATION

       The criteria for establishing whether a wetland (or portion of a wetland) is considered subject to
Level I concentrations, Level II concentrations, or potential contamination generally are identical to those
for a listed sensitive environment (see Section 8.15):

              Actual contamination can be established based on direct observation and/or surface
              water, benthic, or sediment samples taken within or beyond the wetland (or adjacent to
              the wetland if it is contiguous to the hazardous substance migration path).

              Level I concentrations can be established only if at least one hazardous substance in an
              applicable aqueous surface water sample is present at a concentration that is equal to or
              greater than the applicable ecological-based benchmark (i.e., EPA AWQL or EPA
              AALAC for the substance).

              Level II concentrations are established:

              —     If the concentration of all applicable  hazardous substances from all applicable
                     surface water samples are lower than their respective ecological-based
                     benchmarks;

              —     If none of the applicable hazardous substances in all applicable surface water
                     samples has an ecological-based benchmark; or

              —     If actual contamination is established based on sediment samples, benthic
                     samples, or direct observation.

              Potential contamination is established for wetlands within the TDL if Level I or Level II
              concentrations (i.e., actual contamination) cannot be established.

       However, only those portions of wetlands subject to a given level of contamination are evaluated
under that level of contamination (e.g., different portions of the same wetland can be evaluated under
Level I concentrations, Level II concentrations, and potential contamination).

DETERMINING WETLAND LENGTH (OR PERIMETER) SUBJECT TO ACTUAL AND
POTENTIAL CONTAMINATION

       This section provides guidance for determining wetland length or perimeter associated with  Level
I concentrations, Level II concentrations, and potential contamination.Highlights 8-66 through 8-68
provide examples of evaluations of wetlands contiguous to rivers, lakes or oceans, and isolated
wetlands. For guidance on calculating the environmental threat targets factor value, see Section 8.14.

(1)     Determine wetland length (or perimeter) associated with Level I concentrations.

              For rivers and streams, use the length of the wetlands contiguous to the in-water
              segment of the hazardous substance migration path (i.e., wetland frontage) from the
              PPE to the farthest downstream sample establishing Level I concentrations (see
              Highlight 8-66).

              For lakes, oceans,  coastal tidal waters, and Great Lakes, use the length of the wetland
              frontage along the  shoreline subject to Level I concentrations from the PPE to the
              intersection of the arc of the most distant sample establishing Level I concentrations and
              the shoreline (seeHighlight 8-67).
Section 8.16                                    338

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                                  HIGHLIGHT 8-66
DELINEATING ACTUAL CONTAMINATION FOR WETLANDS  IN A RIVER

                          Wetland 1
                                                                                TDL
                                                          Wetland 2
     In this figure, two wetlands (Wetland 1 and Wetland 2) contiguous to a river are evaluated for actual
     and potential contamination.

     Point 2 represents the farthest downstream sample establishing Level I  concentrations; Point 3
     represents the farthest downstream sample establishing Level II concentrations.

     The wetland length considered subject to Level I concentrations is measured from the upstream
     boundary of Wetland 1 to the farthest downstream sample that establishes Level I concentrations (i.e.,
     Point 2).

     Length considered subject to Level II concentrations is measured from the farthest downstream
     sample that establishes Level I concentrations to the farthest downstream sample that establishes
     Level II concentrations (i.e., Point 3).

     Potential contamination is measured from the farthest downstream sample that establishes Level II
     concentrations to the TDL (i.e., Point 4).  However, if the TDL is greater than 15 miles due to samples
     that establish actual contamination, potential contamination is not  scored.

     In this example:

     —       The shoreline length A to B is subject to Level I concentrations;
     —       The shoreline length B to C and D  to E is subject to Level II concentrations; and
     —       The shoreline length E to F is subject to potential contamination.

     In areas with both fresh and brackish water  (i.e, tidal areas), the applicable benchmark for a given
     hazardous substance may be different in the  fresh water portion of the river than the brackish portion
     of the river (e.g., a given concentration could be below the benchmark in fresh water but above the
     benchmark in brackish water).

     Special consideration should be given to tidal areas.
                                            339
                                                                                       Section 8.16

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                                     HIGHLIGHT 8-67
      DELINEATING ACTUAL CONTAMINATION FOR WETLANDS  IN A LAKE,
                        OCEAN, AND COASTAL TIDAL WATERS
                                                   15 Miles
                                         • Level V
                           'Level II
                                                Level I
                                          PPE
              Wetland 1
Wetland 2
                                                           Wetland 3
          For lakes, oceans, and coastal tidal waters, an arc bisecting the coastline is drawn from the PPE to
          the TDL. To determine the coastline subject to different levels of contamination, draw separate arcs,
          each with a distance equal to the length from the PPE to the most distant sampling point that
          establishes Level I and Level II concentrations, each arc bisecting the coastline.

          In this example, the lengths of wetland subject to Level I concentrations are the lengths E to F and
          G to H measured along the coastline (i.e, not a straight-line distance).  Note that even though a
          sample that establishes Level II concentrations was found within the Level I concentration arc, the
          Level I concentration arc is determined by the most distant sample establishing Level I concentrations.

          Lengths of wetland subject to Level II concentrations are the coastline lengths D to E and  H to I.

          Potential contamination includes those portions of wetlands outside the Level I and/or Level II arc(s),
          but within the TDL  In this example, lengths subject to  potential contamination are A to B to C, and
          I  to J to K.
Section 8.16
                                               340

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              For an isolated wetland, or for a wetland where the PPE to surface water is in the
              wetland, use the perimeter of that portion of the wetland considered subject to Level I
              concentrations as the length. If the PPE to surface water is within a wetland and other
              wetlands within the TDL are subject to Level I concentrations, use the perimeter for the
              wetland in which the  PPE is located and the length for all other wetlands within the TDL
              (see Highlight 8-68).

              See Section 8.1 if the surface water bodies being evaluated are tidally influenced.

              See Section 8.3 if both  fresh water and salt water (or brackish) surface water bodies are
              within the TDL.

(2)     Determine wetland length (or perimeter) associated with Level II concentrations.

              For rivers and streams, use the length of the wetlands contiguous to the in-water
              segment of the hazardous substance  migration path (i.e., wetland frontage) between the
              farthest downstream  samples establishing Level I and  Level II concentrations. In the
              absence of Level I concentrations, use the length from the PPE to the farthest
              downstream sample establishing Level II concentrations (seeHighlight8-66).

              For lakes, oceans, coastal tidal waters, and Great Lakes, use the length of wetland
              frontage along the shoreline between  the farthest downstream samples establishing
              Level I concentrations.  In the absence of Level I and Level II concentrations, use the
              length from the PPE to  the farthest sample establishing Level II concentrations (see
              Highlight 8-67).

              For an isolated wetland, or for a wetland where the PPE to surface water is within the
              wetland, use the perimeter of the portion of the wetland considered subject to Level II
              concentrations as the length (see High light 8-68).

              See Section 8:1 if the surface water bodies being evaluated are tidally influenced.

              See Section 8.3 if both  fresh water and salt water (or brackish) surface water bodies are
              within the TDL.

(3)     Determine wetland length associated with  potential contamination.

              For rivers and streams, use the length of wetlands contiguous to the in-water segment of
              the hazardous substance migration path. Include the length of wetlands within the TDL
              from the farthest downstream sampling point establishing actual contamination or from
              the PPE, if no sampling points establish Level  I or Level II concentrations.

              For lakes, oceans, coastal tidal waters, and the Great Lakes, use the length of wetlands
              along the shoreline within the TDL not subject  to Level I or Level II concentrations.

              For an isolated wetland or for a wetland where the PPE to surface water is within the
              wetland, use the perimeter of that portion of the wetland not subject to Level I or Level II
              concentrations as the length.

              See Section 8.1 if the surface water bodies being evaluated are tidally influenced.

              See Section 8.3 if both  fresh water and salt water (or brackish) surface water bodies are
              within the TDL.
                                             341                                     Section 8.16

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                                      HIGHLIGHT 8-68
      DELINEATING ACTUAL CONTAMINATION FOR WETLANDS WHEN THE
                 PROBABLE  POINT OF ENTRY IS IN THE WETLAND
                                                                            PPE
           In this example, there is an observed release to an isolated wetland. To determine the perimeter of
           wetland subject to actual and potential contamination, draw an arc with a radius equal to the distance
           from the PPE to the farthest sampling point that establishes Level I and/or Level II concentrations.
           This arc will have the PPE as the center, pass through the farthest sampling point, and intersect with
           the wetland boundaries,

           For Level I concentrations,  the perimeter is equal to those portions  of the arc delineating Level I
           concentrations within the wetland plus the length of wetland boundary the arc intersects.  For Level
           II concentrations, the perimeter is equal to the arc drawn from the PPE to the farthest Level II sample,
           the arc delineating  Level I concentrations (if applicable), and the  length  of wetland  boundary
           connecting these arcs.

           In this example, the arc delineating Level I concentrations is shown by arc A-C. Therefore, the length
           of wetland subject to Level I concentrations is shown by  ABCA.

           The perimeter of the arc marking Level II concentrations intersects the wetland boundaries at points
           D and F.  The perimeter of wetland to be considered for Level II concentration is shown by ACDFA.

           Potential contamination is scored as the remainder of the isolated wetland and other surface water
           bodies within the TDL. For this isolated wetland, the perimeter of the wetland subject to potential
           contamination is FDEF.
TIPS AND REMINDERS

       A significant environmental threat score based solely on potentially contaminated wetlands can
       generally be achieved only with a large wetland area and a water body type of minimal stream or
       small to moderate stream.

       Under potential contamination, minimize efforts to identify and delineate wetlands unless the
       waste characteristics factor category value is greater than  100, and river size (or lake size) is
       less than a moderate to large stream.
Section 8.16
                                              342

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CHAPTER 9
SOIL EXPOSURE PATHWAY
                 RESIDENT POPULA TION THREA T
 LIKELIHOOD OF
 EXPOSURE

 Observed
  Contamination Area
  with Resident
  Targets
X
WASTE
CHARACTERISTICS

Toxicity
Hazardous Waste
 Quantity
X
TARGETS

Resident Individual
Resident Population
Workers
Resources
Terrestrial Sensitive
  Environments
                    NEARBY POPULATION THREAT
 LIKELIHOOD OF
 EXPOSURE

 Attractiveness/
  Accessibility
 Area of
  Contamination
X
WASTE
CHARACTERISTICS

Toxicity
Hazardous Waste
  Quantity
X

TARGETS

Nearby Individual
Population Within 1
 Mile


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SECTION  9.1
AREAS OF OBSERVED
CONTAMINATION
       The soil exposure pathway evaluates the threat to individuals and sensitive environments of
exposure to surficial contamination. The purpose of this section is to assist the scorer in identifying and
delineating areas of observed contamination. It is essential to identify and delineate areas of observed
contamination because:

             The pathway can be evaluated only if there are areas of observed contamination;

             Target values are assigned based on their distance from areas of observed
             contamination; and

             The hazardous waste quantity is based on areas of observed contamination.

The soil exposure pathway is based on current conditions; potential migration to additional targets is not
evaluated. Although called the soil exposure pathway, any surficial contamination is eligible to be
evaluated.
                             RELEVANT MRS SECTIONS

        Section 2.2.2            Identify hazardous substances associated with a source
        Section 2.3              Likelihood of release
        Section 5.0.1            General considerations
        Section 5.1.1            Likelihood of exposure
        Section 5.1.2            Waste characteristics
        Section 5.2.1            Likelihood of exposure
DEFINITIONS
       Area of Observed Contamination: Established based on sampling locations as any of the
       following:

              Generally, for contaminated soil, consider the sampling locations that indicate observed
              contamination and the area lying between such locations to be an area of observed
              contamination, unless information indicates otherwise.

              For sources other than contaminated soil, if any sample taken from the source indicates
              observed contamination, consider that entire source to be an area of observed
              contamination.

       If an area of observed contamination (or a portion of such an area) is covered by a permanent,
       or otherwise maintained, essentially impenetrable material (e.g., asphalt), exclude the covered
       area from the area of observed contamination. However,  asphalt or other impenetrable materials
       contaminated by site-related hazardous substances may be considered areas of observed
       contamination.


                                          343                                   Section 9.1

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       Observed Contamination: Surficial contamination related to a site. It must be established by
       chemical analysis. Observed contamination is present at sampling locations where analytic
       evidence indicates that:

              A hazardous substance attributable to the site is present at a concentration significantly
              above background levels for the site (i.e., meets the observed release criteria in MRS
              Table 2-3).

              The hazardous substance is present at the surface or covered by two feet or less of
              cover material (e.g., soil).

ESTABLISHING AREAS OF OBSERVED CONTAMINATION

(1)     Identify sampling locations that meet the criteria for observed contamination. Consult
       Highlight 9-1 for appropriate source-specific background samples.

(2)     Define the areas of observed contamination.

              For all sources other than contaminated soil, consider the  entire source to be an area of
              observed contamination if any sampling location within the source meets the criteria for
              observed contamination (see Highlight 9-2).

              For contaminated soils, consider sampling locations that meet the criteria for observed
              contamination and the areas lying between such sampling locations to be areas of
              observed contamination, unless information indicates otherwise (seeHighlights 9-3 and
              9-4).

HIGHLIGHT 9-1
BACKGROUND SAMPLES FOR AREAS OF
OBSERVED CONTAMINATION
SOURCE
Contaminated Soil
Tanks/Drums Filled with
Contaminated Soil
Tanks/Drums Containing
Liquid or Solid Wastes
Landfill3
Piles3
Surface Impoundment3
(liquid)
Surface Impoundment3
(sludges or backfilled)
Other Sources
Background Sample
Soil in vicinity of the site. See Sections 5.1 and 5.2 for additional
considerations.
Same as for the soil at the site.
Background is zero.
Soil in vicinity of the site.
Soil in vicinity of the site.
Aqueous samples from vicinity of the site. Background may be zero.
Soil in the vicinity of the site.
review on a site-specific basis
a For these source types, the indicated sample is likely to be the most appropriate background.

Section 9.1
                                            344

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                                  HIGHLIGHT 9-2
        DELINEATING AREAS OF OBSERVED CONTAMINATION FOR
               SOURCES OTHER THAN CONTAMINATED SOIL
      Xx m Sample location that establishes observed contaminiation

      Yx = Boundaries of landfill

      OK » Sample location that does not establish area of observed contamination

      Lined areas - Areas of observed contamination

Several samples indicate observed contamination, others do not. The scorer should consider the following:

•      Because the landfill is a source type other than contaminated  soils,  and at least one sample
       establishes observed contamination, consider the entire landfill as the area of contamination. The
       area does not need to be delineated by samples.
    Information that may indicate that areas lying between sampling locations do meet the criteria for
    observed contamination includes the following:

           The route by which hazardous substances could have migrated to areas at the site
           involves wide dispersion of contamination (e.g., if stack emissions are the principal
           mechanism of deposition, areas between sampling locations are likely to  be subject to
           observed contamination, see Highlight 9-5).

           If the principal mechanism of deposition is spills (e.g., at a loading dock or process
           area), then generally, the entire area delineated by samples is likely to be subject to
           observed contamination.

           Downgradient portions of a well-defined hazardous substance migration route meet the
           criteria for observed contamination, even if some discrete sampling locations within the
           migration route do not meet the criteria.
                                         345
                                                                                Section 9.1

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                                      HIGHLIGHT 9-3
           DELINEATING AREAS OF OBSERVED CONTAMINATION FOR
                                  CONTAMINATED SOIL
                        Xx - Sample location that establishes observed contaminiation

                        Ox - Sample location that does not establish observed contamination

                        Lined areas - Areas of observed contamination
   The area of observed contamination resulted from spills and is not limited to a specific area.  Consider the
   following:

   •       Delineate the area of observed contamination.  In this example, it would be the polygon formed by
          sampling locations X1, Xg, X3, and X4. The left boundary of the contamination area would be X4 to
          X1 rather than X4 to X5 to X1, because site-specific evaluations indicate the area to the left of X5 may
          be subject to contamination.

          Include the sampling locations that do not indicate surficial contamination (e.g., O^ O2, and Og) In
          the area of observed  contamination because, based  on the site operations, topography, and
          hazardous substance  migration route, there  is reason to infer these  areas  are  subject to
          contamination.
(3)     Refine areas of observed contamination. Consider information that might indicate areas
       lying between sampling locations meeting the criteria for observed contamination should not
       be included:

               Areas are covered by a permanent or otherwise maintained, essentially impenetrable
               material (e.g., asphalt, concrete).

               Contamination is the result of run-off from a site, and topography indicates that certain
               areas within an area of contamination are on higher land and not influenced by run-off
               (see Highlight 9-6).

               The location and type of operations at a facility could preclude hazardous wastes from
               being in certain areas (e.g., soils near a process area and near a loading dock may be
               contaminated, but the area between these locations may not be expected to be
               contaminated).

               Cover material or fill (e.g., soil) has been deposited on top of contaminated surficial
               material, resulting in no observed  contamination within two feet of the surface (see
               Highlight 9-6).
Section 9.1                                       346

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                                   HIGHLIGHT 9-4
           DELINEATING AREAS OF OBSERVED CONTAMINATION
                          USING COMPOSITE SAMPLES
                                                                    A
                                                                    A
               Sampling grid with samples establishing observed contamination
           ^ Sampling grid with inferred contamination
           A Sampling grid with samples not establishing observed contamination
Soil has been contaminated by atmospheric deposition. As part of an emergency action, extensive sampling
was conducted to delineate the extent of contamination. All samples were taken within two feet of the soil
surface. To delineate the area of observed contamination using the grid sampling:

•       Consider each grid with a sampling location meeting the criteria for observed contamination part of
        the area of observed contamination.

•       Consider grids with no sampling data located between grids with observed contamination (inferred
        or sampled) to be contaminated unless information indicates otherwise (e.g., the grid is covered by
        asphalt).

•       Exclude grids with sampling data indicating no observed contamination.

•       Exclude portions of grids that are covered by a permanent or otherwise maintained, essentially
        impenetrable material from the area of observed contamination.

        Therefore, the grids outlined above by the dashed line are the area of observed contamination.
                                           347
                                                                                      Section 9.1

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                                     HIGHLIGHT 9-5
               INFERRING CONTAMINATION BETWEEN MULTIPLE
                      AREAS OF OBSERVED CONTAMINATION
                                                                        AOC
             Sample location that establishes observed contamination
             Sample location that establishes observed contamination
  Two areas of observed contamination (AOC 1 and 2) are defined by sampling locations.  Determine if the area
  between these areas can be inferred to be contaminated.  Consider the following:

  •       If the contamination results from atmospheric deposition (e.g., releases from a smelter located in the
         vicinity), consider the area between AOC 1  and AOC 2 (i.e., the outlined area) to be an area  of
         observed contamination.

  •       If the two areas of observed contamination are located in two separate work areas (e.g., two loading
         docks)  and the contaminated  soil results from processes performed in the work area, it may not be
         reasonable to infer the area between these locations to be an area of observed contamination.

  •       If the two areas of observed contamination are associated with different hazardous constituents and
         sampling data do not indicate  an overlap of hazardous substances, do not include the area between
         these two areas of observed contamination.
Section 9.1
                                             348

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                                    HIGHLIGHT 9-6
       DELINEATING AREAS OF OBSERVED CONTAMINATION WHEN
                UNCONTAMINATED SOILS ARE INTERMINGLED
                                                                          Hilltop
        X  = Sample location that establishes observed contamination

        O  = Sample location that does not establish observed contamination

        Lined areas = Areas of observed contamination



Soil has been contaminated by run-off. Areas in the center of the contamination have been disturbed and two
feet of topsoil has been brought in to fill and cover an excavated area near sampling locations O1, O2, and
O3. In  this case, consider the following:
        Delineate the area of observed contamination as the polygon formed by sampling locations X1,  Xg,
        X3, and X4. The left boundary of the contaminated area would be X4 to X1 rather than X4 to X5 to
        X1(  because  site-specific evaluations  indicate the area to the left of X5 may be subject to
        contamination.

        Delineate the area marked by the samples indicating no surficial contamination.  In this example, two
        or more feet of topsoil has been deposited in the vicinity of sampling locations O1, Og and O3 to fill
        an excavated area.  Because the topsoil was deposited in this area and analytic samples indicate no
        observed contamination,  assume the surficial soil is not contaminated in this area.
        Since the hilltop is not in the hazardous substance migration route (i.e., it is at a higher elevation and
        the run-off flows around the hill), do not consider the hilltop subject to observed contamination
        (samples are not necessary in this situation).

        Subtract the area of no observed contamination (i.e., the area marked by samples and the hilltop)
        from the total area of observed contamination to determine the actual area of observed contamination.
                                             349
                                                                                        Section 9.1

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TIPS AND REMINDERS

       Score the soil exposure pathway only if observed contamination is established.

       Analytic evidence supported with non-sampling evidence may be used to infer the extent of
       observed contamination. Non-sampling evidence may include soil staining, documented
       historical waste deposition patterns, stressed vegetation patterns, and data derived from
       investigations such as soil gas surveys.

       An area of observed contamination can be defined by one sampling location. For example, one
       sample is collected from a residential property to which site-related contamination has migrated.

       Contaminated samples from leachate and sediments can be used to document observed
       contamination if they are attributable to the site, and for sediments, if they are not covered by
       water at all times.
Section 9.1                                     350

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SECTION 9.2
WASTE CHARACTERISTICS
FOR THE SOIL  EXPOSURE
PATHWAY
UHjJfSaUU
                                                                            we
       This section compares the differences in evaluating toxicity and hazardous waste quantity for the
soil exposure pathway and the migration pathways. (For guidance on evaluating hazardous waste
quantity for the migration pathways, see Chapters.)

       Because the soil exposure pathway assesses the risks associated with exposure to existing
surficial contamination, evaluation of waste characteristics for the soil exposure pathway differs from the
evaluation for the migration pathways. There are differences in both the contaminant characteristics and
the hazardous waste quantity components of waste characteristics. In evaluating contaminant
characteristics, only substances that establish observed contamination can be used (e.g., do not use any
other hazardous substance in the source). Furthermore, toxicity is the only contaminant characteristic
included in the soil exposure pathway; other factors such as mobility and persistence are not considered.

       This section details differences in the evaluation of hazardous waste quantity. In general, the
evaluation performed for the migration pathways is modified to include only hazardous waste present in
the top two feet of surficial matter. Thus, several divisors in the default equations are different (i.e., MRS
Table 5-2 is used instead of MRS Table 2-5). Although termed the "soil exposure" pathway, all sources
on which areas of observed contamination are established can be included in the site hazardous waste
quantity factor value.
                            RELEVANT MRS SECTIONS

        Section 2.2.2            Identify hazardous substances associated with a source
        Section 2.4.1.1           Toxicity factor
        Section 2.4.2            Hazardous waste quantity
        Section 5.1.2.1           Toxicity
        Section 5.1.2.2           Hazardous waste quantity
        Section 5.2.1.2           Area of contamination
        Section 5.2.2.1           Toxicity
DEFINITIONS
       Area of Observed Contamination:  Established based on sample locations as any of the
       following:

             Generally, for contaminated soil, consider the sampling locations that indicate observed
             contamination and the area lying between such locations to be an area of observed
             contamination, unless information indicates otherwise.
                                         351                                  Section 9.2

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              For sources other than contaminated soil, if any sample taken from the source indicates
              observed contamination, consider that entire source to be an area of observed
              contamination.

       If an area of observed contamination (or a portion of such an area) is covered by a permanent,
       or otherwise maintained, essentially impenetrable material (e.g., asphalt), exclude the covered
       area from the  area of observed contamination. However, asphalt or other impenetrable materials
       contaminated  by site-related hazardous substances may be  considered areas of observed
       contamination.

       Observed Contamination: Surficial contamination related to a site. It must be established by
       chemical analysis. Observed contamination is present at sampling  locations where analytic
       evidence indicates that:

              A hazardous substance attributable to the site is present at a concentration significantly
              above background levels for the site (i.e., meets the observed release criteria in MRS
              Table 2-3).

              The hazardous substance is present at the surface or covered by two feet or less  of
              cover material (e.g., soil).

EVALUATING TOXICITY

       Select the hazardous substance with the highest human toxicity factor value from among the
substances that meet  the criteria for observed contamination for the  threat  evaluated. In addition,  for the
nearby threat, the substance must also be from an area with an attractiveness/accessibility factor  value
greater than zero.

       Assign a toxicity factor value for a hazardous substance in the soil  exposure pathway the  same
as for any other pathway (except the surface water environmental threat). The process, described in
MRS section 2.4.1.1 and presented in MRS Table 2-4, is based on this hierarchy:

              Chronic toxicity  using RfDs/carcinogenicity using SFs and weight-of-evidence ratings;
              and, if these are not available,

              Acute toxicity using LD50s and LC50s.

       Both PREscore  and SCDM can  help determine the toxicity value of a particular hazardous
substance. See MRS section 2.4.1.1 for detailed direction in obtaining toxicity values and assigning a
toxicity factor value for hazardous substances not included in PREscore or SCDM.

EVALUATING HAZARDOUS WASTE QUANTITY

       Primary differences in evaluating hazardous waste quantity in the soil exposure pathway
compared to the migration pathways, include the following:

              Only areas of observed  contamination  are considered.

              Only the first two feet of depth of an area of observed contamination are considered
              (except  as specified for volume measures).

              Areas covered by essentially permanent, impenetrable material are excluded (e.g.,
              contaminated soil covered by uncontaminated asphalt).

              Tier C (volume)  can be used only for drums, tanks and containers other than drums,
              and surface impoundments containing  liquid hazardous substances.


Section 9.2                                      352

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              Some equations for assigning a source hazardous waste quantity value in Tier D are
              different (Note that, if available, Tier A and B data can also be used for drums, tanks,
              and surface impoundments).

              If Tier A is not adequately determined, the minimum factor value is always 10.

These differences are summarized in Highlight 9-7.

EVALUATING TIER A— HAZARDOUS CONSTITUENT QUANTITY

       To evaluate Tier A for an area of observed contamination:

(A1)    Determine whether the source Is an area of observed contamination. See Section 9.1. For
       the nearby population threat, also determine if the area of observed contamination has an
       attractiveness/accessibility factor value greater than 0 (see Section 9.8). If not, do not
       evaluate hazardous waste quantity for that particular area of observed contamination.

(A2)    Determine whether CERCLA hazardous substances meet the criteria for observed
       contamination (i.e., attributable to the site, present at a concentration significantly above
       background levels, and present within 2 feet of the surface).

       For each area of observed contamination, consider only those hazardous substances that meet
       the criteria for observed contamination within that area (e.g., if substance X meets the criteria for
       observed contamination in Source A, it cannot be evaluated in Source B unless it also meets the
       criteria for observed contamination in Source B);

              If there  are such substances, continue to Step (A3).

              If not, do not evaluate the area of observed contamination  with Tier A. Assign a value of
              zero for source hazardous constituent quantity and evaluate the area of observed
              contamination with Tier B.

       (A3)    Evaluate the area of observed contamination using Tier A In the same manner as
              for migration pathways.  See Section 6.2. There are two exceptions to this  evaluation:

              Consider only the top two feet of the area of observed contamination, based on present
              conditions at the site.

              Assign  a value for the area of observed contamination using the Tier A equation in MRS
              Table 5-2 (Note the Tier A equation is identical in MRS Tables 5-2 and 2-5).

       Hazardous substance concentration data that is representative of the top two feet of an area of
observed contamination may be used.

EVALUATING TIER B — HAZARDOUS WASTESTREAM QUANTITY

       To evaluate Tier B for an area of observed contamination in the soil exposure pathway:

(B1)    Determine whether the source Is an area of observed contamination. See Section 9.1. For
       the nearby population threat, also determine if the area of observed contamination has an
       attractiveness/accessibility factor value greater than 0 (see Section 9.8). If not, do not evaluate
       hazardous waste quantity for that particular area  of observed contamination.
                                           353                                    Section 9.2

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HIGHLIGHTS-?
COMPARISON OF HAZARDOUS WASTE QUANTITY
EVALUATION IN THE MIGRATION PATHWAYS AND
THE SOIL EXPOSURE PATHWAY
Migration Pathways
Evaluate all sources.
Consider entire source when evaluating all four
tiers.
Tier C (volume) can be used for these types of
sources:
Landfill
Surface impoundment
Surface impoundment (buried/backfilled)
Drums
Tanks and containers other than drums
Contaminated soil
Pile
Other
Table 2-5 provides the equations for assigning the
source hazardous waste quantity value.
If hazardous constituent quantity (Tier A) Is not
adequately determined for all sources, the
minimum factor value depends on:
• Whether the targets are subject to actual
contamination, and
• Whether there has been a removal action.
Soil Exposure Pathway
Evaluate only areas of observed contamination.
Consider only top two feet of an area of observed
contamination, except when evaluating TierC
(volume).
Tier C (volume) can be used only for these types
of sources:
Surface Impoundment containing
hazardous substances present as liquids
Drums
Tanks and containers other than drums
Table 5-2 provides the equations for assigning the
source hazardous waste quantity value.
If hazardous constituent quantity (Tier A) is not
adequately determined for all areas of observed
contamination, the minimum factor value is
always 10.


       (B2)   Determine whether Tier A has been adequately determined for the area of
              observed contamination. If so, do not evaluate Tiers B, C, or D for this area. If Tier A
              is not adequately determined, continue to Step (B3).

       (B3)   Determine If the hazardous wastestream contains hazardous substances that meet
              the criteria for observed contamination (i.e., attributable to the site, present at a
              concentration significantly above background levels, and present within 2 feet of
              the surface). Only hazardous wastestreams that contain at least one hazardous
              substance that meets the criteria for observed contamination within an area of observed
              contamination are considered present  in that area of observed contamination.

                     Do not evaluate those wastestreams, that do not contain at least one hazardous
                     substance that meets the criteria for observed contamination.

                     If no wastestreams contain hazardous substances that meet the criteria for
                     observed contamination do not evaluate the area of observed contamination
                     with Tier B. Assign
Section 9.2
                                            354

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              a value of 0 for source hazardous wastestream quantity and evaluate the area of
              contamination with Tier C.

              If wastestreams contain hazardous substances that meet the criteria for observed
              release, continue to Step (B4).

(B4)   Evaluate the area of observed contamination using Tier B in the same manner as for the
       migration pathways. See Section 6.3. There are two exceptions:

              Consider only the top two feet of the area of observed contamination, based on present
              conditions at the site.

              Assign a value for the area of observed contamination using the Tier B equation in MRS
              Table 5-2. (Note the Tier B equation is identical in MRS Tables 5-2 and 2-5.)

       Manifests and process records usually provide good accounts of wastestreams. However, since
the evaluation of hazardous wastestreams in the soil exposure pathway is restricted  to the top two feet of
the area of observed contamination and is based on present conditions, it should be documented that the
waste, reported in the manifests and process  records, was deposited or migrated within the top two feet.
As general guidance, if manifests specify how much waste was deposited  into a landfill and the landfill is
known to be, for example, 10 feet deep, then 24/10 (or 1/5) of the manifested wastestream quantity can
be assumed to be within the top two feet, unless information indicates otherwise.

EVALUATING TIER C — VOLUME

       To evaluate Tier C for an area of observed contamination in the soil exposure pathway:

(C1)   Determine whether the source Is an area of observed contamination. See Section 9.1. For
       the nearby population threat, also determine if the area of observed contamination has an
       attractiveness/accessibility factor value greater than 0 (see Section 9.8). If not, do not evaluate
       hazardous waste quantity for that particular area of observed contamination.

(C2)   Determine whether Tier A or B has  been adequately determined for the area of observed
       contamination. If so, do not evaluate Tier C or D for this area. If Tier A or B is not adequately
       determined, continue to Step (C3).

(C3)   Determine It the type of area of observed contamination Is eligible to be evaluated under
       Tier C in the soil exposure pathway.

              Use Tier C only for the following types of areas of observed contamination:

              S      Surface impoundments containing hazardous substances present as  liquids
                     (evaluate dry, buried or backfilled surface impoundments under Tier D);

              S      Drums; or

              S      Tanks and containers other than drums.

              If the area of observed contamination is eligible to be evaluated under Tier C, continue
              to Step (C4).

              If not, do not evaluate the area of observed contamination with Tier C. Assign a value of
              0 for source volume, and evaluate the area of contamination using Tier D.
                                            355                                    Section 9.2

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(C4)   In evaluating volume for the eligible types of areas of observed contamination, use the
       full volume, not just the volume within the top two feet. Evaluate the area of observed
       contamination using Tier 0 in the same manner as for migration pathways (see Section 6.4)
       except:

              Assign a value for the area of observed contamination using the Tier C equation in MRS
              Table 5-2.

EVALUATING TIER D — AREA

       To evaluate Tier D (area), for an area of observed contamination not eligible to be evaluated
under Tier C (volume):

(D1)   Determine whether the source Is an area of observed contamination. See Section 9.1. For
       the nearby population threat, also determine if the area of observed contamination has an
       attractiveness/accessibility factor value greater than 0 (see Section 9.8). If not, do not evaluate
       hazardous waste quantity for that particular area of observed contamination.

(D2)   Determine whether Tier A, B, or C has been adequately determined for the area of
       observed contamination. If so, do not evaluate Tier D. If Tier A, B, or C is not adequately
       determined, continue to Step (D3).

(D3)   Determine If the area of contamination Is one of the following:

              Surface impoundments containing hazardous substances present as liquids (evaluate
              dry, buried or backfilled surface impoundments under Tier D);

              Drums; or

              Tanks and containers other than drums.

       If the area of contamination is one of these three types, evaluate  using Tier C. Do not  evaluate
       using Tier D.

       If the area of contamination is not one of these three types, continue to Step (D4).

(D4)   Evaluate the area of observed contamination using Tier D In the same manner as for
       migration pathways. See Section 6.5. There is one exception:

              Assign a value for the area of observed contamination using the Tier D equations in
              MRS Table 5-2.

CALCULATING HAZARDOUS WASTE QUANTITY FACTOR VALUE

       Select the highest of the values assigned to each area of observed contamination from all tiers
evaluated. This value is the source hazardous waste quantity for the area of observed contamination.

       Sum the source hazardous waste quantity values assigned to each area of observed
contamination to determine the hazardous waste quantity factor value. Round this sum to the nearest
integer, except if the sum is greater than 0, but less than 1, then round it to 1. Based on this value, select
the hazardous waste quantity factor value for the soil exposure pathway using MRS Table 2-6.

       The minimum hazardous waste quantity factor value for the soil exposure pathway is 10, unless
Tier A is adequately determined, regardless of whether targets are actually contaminated or whether a
qualifying removal action has taken place.
Section 9.2                                     356

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TIPS AND REMINDERS

       The hazardous waste quantity value calculated for the resident population threat will be equal to
       or greater than the hazardous waste quantity value calculated for the nearby population threat.
       This is because of the additional requirement that only areas of observed contamination with an
       attractiveness/accessibility factor value greater than 0 can be evaluated for the nearby
       population threat.

       Use available volume measurements for surface  impoundments containing hazardous
       substances as liquids, drums, and other containerized wastes. Otherwise, use the area measure
       of the upper two feet for all sources.

       Consider only substances that meet the criteria for observed contamination when calculating
       waste characteristics.
                                             357                                     Section 9.2

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SECTION  9.3
RESIDENT
POPULATION THREAT
      This section provides an overview of the targets factor category of the resident population threat
of the soil exposure pathway and explains how to identify targets for that threat. High light 9-8
summarizes the targets considered in the resident population threat, the maximum factor value assigned
to each of these targets, and references to the sections of this guidance and the section in the MRS that
discuss each target. All targets evaluated in the resident population threat are subject to actual
contamination. If no targets are identified, the resident population threat receives a score of 0; however,
the nearby population threat may still be evaluated.
                           RELEVANT MRS SECTIONS

          Section 5.1.3            Targets
          Section 5.1.3.1           Resident individual
          Section 5.1.3.2           Resident population
          Section 5.1.3.3           Workers
          Section 5.1.3.4           Resources
          Section 5.1.3.5           Terrestrial sensitive environments

HIGHLIGHT 9-8
TARGETS IN THE RESIDENT POPULATION THREAT
Target
Resident Individual
Resident Population
Workers
Resources
Terrestrial Sensitive
Environment
Maximum Factor Value
50
no maximum
15
5
site-specific-limited to that
which results in a pathway
score of 60 based solely on
sensitive environments
HRSGM Section
9.4
9.4
9.5
9.6
9.7
MRS Section
5.1.3.1
5.1.3.2
5.1.3.3
5.1.3.4
5.1.3.5


                                        359
                                                                            Section 9.3

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DEFINITIONS
       Area of Observed Contamination: Established based on sampling locations as any of the
       following:

               Generally, for contaminated soil, consider the sampling locations that indicate observed
               contamination and the area lying between such locations to be an area of observed
               contamination, unless information indicates otherwise.

               For sources other than contaminated soil, if any sample taken from the source indicates
               observed contamination, consider that entire source to be an area of observed
               contamination.

       If an area of observed contamination (or a portion of such an area) is covered by  a permanent,
       or otherwise maintained, essentially impenetrable material (e.g., asphalt), exclude the covered
       area from the area of observed contamination. However, asphalt or other impenetrable materials
       contaminated by site-related hazardous substances may be considered areas of observed
       contamination.

       Observed Contamination: Surficial contamination related to a site. It must be established by
       chemical analysis. Observed contamination is present at sampling  locations where analytic
       evidence indicates that:

               A hazardous substance attributable to the site is present at a concentration significantly
               above background levels for the site (i.e., meets the observed release criteria in MRS
               Table 2-3).

               The hazardous substance  is present at the surface or covered by two feet or less of
               cover material (e.g., soil).

       Resident Individual:  A person who lives or attends school or day care on a property with an
       area of observed contamination and whose residence, school, or day care center, respectively,
       is on or within 200 feet of the area  of observed contamination.

       Resources: Resources considered for the soil exposure pathway are commercial agriculture,
       commercial silviculture, and commercial livestock production or grazing.  Resources must be
       located on an area of observed contamination. See Section  9.5 for additional guidance.

       Students: Full- or part-time attendees  of an educational institution or day care facility located on
       or within 200 feet of an area of observed contamination. That area  must also be within the
       property boundaries of institution of facility.

       Terrestrial Sensitive Environment: A terrestrial sensitive environment is defined as any area
       that meets the criteria listed in MRS Table 5-5. No other areas are considered terrestrial sensitive
       environments. Appendix A defines  each terrestrial sensitive  environment and provides sources
       for identifying terrestrial sensitive environments. See Section 9.6 for additional guidance on
       scoring terrestrial sensitive environments.

       Worker: A person working on a property with an area of observed contamination and whose
       workplace area is on or within 200  feet of an area of observed contamination. Both full and
       part-time workers are considered. Section 9.5 provides additional guidance.
Section 9.3                                     360

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IDENTIFYING RESIDENT INDIVIDUALS AND WORKERS

       Identify resident individuals and workers as follows (seeHighlight 9-9 for an example):

(1)     Delineate areas of observed contamination. Section 9.1 provides step-by-step instructions
       for delineating areas of observed contamination. Mark these areas on a map that also
       indicates property boundaries (usually legal boundaries are the most appropriate) in the
       vicinity of the site.

(2)     Identify those properties with areas of observed contamination. If an area of observed
       contamination is located within the property boundaries of a residential property, school/day-
       care center, or workplace, continue to Step (3).

(3)     Determine whether the residence, school, day care center, or workplace is within 200 feet
       of an area of observed contamination.

              Measure this distance as a straight line from the part of the building nearest the area of
              observed contamination unless there is a major obstacle (e.g., building, fence) between
              the two points. If the residence, school, day care center, or workplace area is within 200
              feet of an area of observed contamination, then the resident, student, day care attendee,
              or worker is a target for the resident population threat.  If the distance is greater than 200
              feet, then those persons are  not targets for the resident population threat.
                                     HIGHLIGHT 9-9
                        IDENTIFYING RESIDENT INDIVIDUALS

                                      AREA OF OBSERVED
                                        CONTAMINATION
            200 feel
             Sample location
          People living in Residences A, B, and D are resident individuals—the area of observed contamination
          lies within the property boundaries of these residences and the residences are 200 feet or less from
          the area of observed contamination.

          People living in Residence C are not resident individuals—the area of observed contamination does
          not lie within the property boundaries of Residence C.

          People living in Residence E are not resident individuals — Residence E is more than 200 feet from
          the area of observed contamination.
                                             361
                                                                                      Section 9.3

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              Evaluate multiple-unit residences such as apartments and condominiums as follows:

              —     If the area of observed contamination is located in a common area, count all
                     residents that regularly use the area as resident individuals, regardless of the
                     distance from the area of observed contamination to the individual residences
                     (e.g., if an apartment has four playgrounds, counti/4 of the residents for each
                     playground).

              —     If the entire area of observed contamination is located in private areas (e.g.,
                     individual backyards), count only those residents living within 200 feet of the
                     area of observed contamination as resident individuals.

IDENTIFYING RESOURCES AND TERRESTRIAL SENSITIVE
ENVIRONMENTS

(1)     Delineate areas of observed contamination. Section 9.1 provides step-by-step instructions for
       delineating areas of observed contamination. Mark these  areas on a scale map or diagram.

(2)     Identify resources or terrestrial sensitive environments present on an area of observed
       contamination.

              If one of the designated resource uses (see Section 9.5) is on an area of observed
              contamination, that use is a target for the resources factor.

              If one of the terrestrial sensitive environments listed in MRS Table 5-5 is on  an area of
              observed contamination, that terrestrial sensitive  environment is a target for the resident
              population threat.

       Resources or terrestrial sensitive environments must be on an area of observed contamination to
be scored; if they are within 200 feet, but not on an area of observed contamination, they cannot be
scored.

LEVEL I  AND LEVEL  II CONCENTRATIONS

       Evaluate only targets subject to actual contamination in the resident population threat; do not
evaluate targets subject to potential contamination. For resident individuals (i.e., residents, students, and
children attending day care), the scorer should determine whether the targets are subject to Level I or
Level II concentrations (see Section 9.4). Workers, terrestrial sensitive environments, and resources are
not differentiated by Level  I and Level II.

TIPS AND REMINDERS

       Assuming a maximum value for waste characteristics, a site can score greater than 28.50 based
       on the soil exposure pathway  resident population if:

       —     Four resident individuals are exposed to Level I concentrations; or
       —     41 resident individuals are exposed to Level II concentrations.

       If no resident individuals are identified, do not determine it the observed contamination is  at
       Level I concentrations or Level II  concentrations.
Section 9.3                                     362

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SECTION 9.4
RESIDENT  INDIVIDUAL
AND RESIDENT
POPULATION
       This section provides instructions for determining the level of contamination for resident
individuals, and scoring resident individual and resident population factors in the soil exposure pathway.
The resident individual and resident population factors are two components used to score the targets
factor category of the resident population threat. The scorer should consider the number of qualifying
residents on or near the area of observed contamination, and determine if they are subject to Level I or
Level II concentrations.
                            RELEVANT MRS SECTIONS
         Section 5.1.3          Targets
         Section 5.1.3.1         Resident individual
         Section 5.1.3.2         Resident population
DEFINITIONS
       Resident Individual: A person who lives or attends school or day care on a property with an
       area of observed contamination and whose residence, school, or day care center, respectively,
       is on or within 200 feet of the area of observed contamination. Section 9.3 provides guidance for
       identifying resident individuals.

       Resident Individual Subject to Level I Concentrations:  A resident individual is subject to
       Level I concentrations if the concentration of a hazardous substance that meets the criteria for
       observed contamination is at or above the  appropriate benchmark and the sampling location is
       within the property boundary and within 200 feet of the residence/school. Level I concentrations
       also may be established if multiple hazardous substances are present below their respective
       benchmarks, but the I or J index is greater than or equal to one. Benchmarks for the soil
       exposure pathway include screening concentrations for cancer and screening concentrations for
       chronic noncancer effect.

       Resident Individual Subject to Level II Concentrations: A resident individual not subject to
       Level I concentrations.

       Resident Population: Total number of people meeting  the criteria for resident individual.

       Students: Full- or part-time attendees of an educational institution or day care facility located
       on or within 200 feet of an area of observed contamination. That area must also be within the
       property boundaries of the institution or facility.
                                         363                                  Section 9.4

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       Worker:  A person working on a property with an area of observed contamination and whose
       workplace area is on or within 200 feet of an area of observed contamination. Both full and
       part-time workers are considered. Section 9.5 provides additional guidance.

EVALUATING LEVEL OF CONTAMINATION

       To score the resident individual and resident population factors, the scorer should first determine
the areas of observed contamination (see Section 9.1) and identify all resident individual targets (see
Section 9.3). (Do not count workers in the resident individual or resident population factors. Section 9.5
describes how to score workers in the soil exposure pathway.) Next, determine whether each target is
subject to Level I or Level II concentrations.  Finally, evaluate the resident individual and resident
population factors.

       All resident individuals identified as targets for the resident population threat will be either at
Level I or Level II. No targets in the resident population threat are evaluated as subject to potential
contamination.

(1)     Identify sampling locations that meet the criteria for observed contamination. See Section
       9.1.

(2)     Determine the level of contamination for each sampling location. Compare the
       concentration of each hazardous substance that meets the observed contamination criteria for
       that sampling location with its benchmark(s) for the soil exposure  pathway. These benchmarks
       are available in SCDM.

              If the concentration of any one of these hazardous substances is greater than or equal to
              its benchmark, that sampling location is Level I. Go to Step (4).

              If only  one hazardous substance meets the criteria for observed  contamination and its
              concentration is less than the benchmark, that sampling location is Level II. Go to Step
              (4).

              If more than one hazardous  substance meets the observed contamination criteria for that
              sampling location  but no single substance by itself can be used to establish Level I,
              continue  to Step (3).

(3)     Calculate the  I and J indices for all hazardous substances that meet the observed
       contamination criteria. Make two lists of substances that meet the observed contamination
       criteria: (1) hazardous substances with screening concentrations for cancer risk and (2)
       hazardous substances with screening concentrations for noncancer effects. Each hazardous
       substance may be on one, neither, or both of the lists. If more than one sample has been taken
       at a sampling location and these samples are comparable (e.g., taken in the same time frame,
       collected using the same field techniques, analyzed by the same methods) for each hazardous
       substance, select the highest  concentration to use in the calculations below.

              Calculate the I index for all hazardous substances with screening concentrations for
              cancer risk that meet the observed contamination criteria  for that sampling location,
              using the following equation:


                                              f GI
                                            = M~SC,
Section 9.4                                     364

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       where: C,     =       concentration of hazardous substance i at sampling location;

              SCj    =       screening concentration for cancer corresponding to a concentration
                             associated with a risk of 10s from oral exposure for hazardous
                             substance i; and

              n      =       total number of hazardous substances that meet observed
                             contamination criteria; that are carcinogens; and for which an SC is
                             available.

              Calculate the J  index for all hazardous substances with screening concentrations for
              noncancer effects that meet the observed contamination criteria, using the following
              equation:
       where: Cj     =       concentration of hazardous substance j at sampling location;

              CRj    =       screening concentration for noncancer effects corresponding to oral
                             exposure at reference dose for hazardous substance j; and

              m     =       number of hazardous substances that meet observed  contamination
                             criteria and for which a CR is available.

              If either the I or J index is greater than or equal to 1, the sampling location is Level I. If
              both the I and J indices are less than 1, the sampling location is Level II.

(4)     Indicate  on the site map(s) (with property boundaries marked) where areas of observed
       contamination have been delineated and Identify each sampling location as Level I or
       Level II.

(5)     Identify targets subject to Level I concentrations.  For each resident individual (see Section
       9.3), determine whether a Level I sampling location is located within the property boundaries
       and  within 200 feet of the residence, school, or day care center. If so, evaluate the target as
       Level I. Remember, an inferred area of observed contamination between Level I sampling
       locations is generally evaluated as Level II. If Level I  concentrations cannot be established,
       continue  to Step (6).

(6)     Identify targets subject to Level II concentrations. All resident individuals not subject to
       Level I concentrations are subject to Level  II concentrations.

EVALUATING RESIDENT INDIVIDUAL

       Evaluate  this factor based on whether a resident individual, as specified above, is subject to
Level I or Level II concentrations. Assign a value to the resident individual factor as follows:

              Assign a value of 50 if at least one resident individual is subject to Level I
              concentrations.

              Assign a value of 45 if no resident  individual  is subject to  Level I concentrations, but at
              least one resident individual is subject to Level  II concentrations.

              Assign a value of 0 if no resident individual is identified.
                                             365                                     Section 9.4

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EVALUATING RESIDENT POPULATION

       The resident population factor value is scored based on the number of resident individuals
subject to Level I and Level II concentrations. The Level I  and Level II concentration factor values are
summed to calculate the resident population factor value.

       Evaluate properties that have been subdivided as follows: if a subdivision consists of individual
lots that are owned by the residents, then treat them as individual properties. If the individual lots are
rented by the individuals living on them, but are still owned by one separate entity (e.g. a trailer park),
treat them as one common property.

(1)     Evaluate the Level I concentration factor.

               Determine the total number of resident individuals subject to Level I concentrations.
               Take an exact count or multiply the number of residences by the average number of
               people per residence for that county. This number should reflect the number of resident
               individuals at the time of SI scoring. However, if a residence or school was abandoned
               for reasons related to site contamination, use the population at the time it was
               abandoned.

               Calculate  the Level I concentration factor value. Multiply the number of persons subject
               to Level I concentrations by 10 to calculate the  factor value. Round the number to the
               nearest integer.

(2)     Evaluate the Level II concentration factor.

               Determine the total number of resident individuals subject to Level II concentrations.
               Determine as indicated in Step (1). Do not include anyone already counted in the Level I
               concentration factor.

               Calculate  the Level II concentration factor value. The number of persons subject to
               Level II  concentrations is the Level II  concentration factor value. Round the number to
               the nearest integer.

(3)     Calculate the resident population factor value. Sum the factor values for Levels I and II
       concentrations.  This number is the  resident population factor value.

Highlights 9-10 and 9-11  provide examples of determining the  level of contamination, scoring the
resident individual factor value, and scoring the resident population factor value.
Section 9.4                                     366

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                                    HIGHLIGHT 9-10
               SCORING EXAMPLE FOR RESIDENT POPULATION
                            ON ADJACENT PROPERTIES

This example illustrates how to determine whether targets are subject to Level I or Level II concentrations and
how to score the resident individual and resident population factors for several residences on individual
properties located adjacent to the site.
(1)
(2)


(3)


t
AREA OF OBSERVED CONTAMINATION
Level 1
k
Level 1

0
t
Level 1
C


0

L

eve
E
I

fc
II
0


G


H
             50 feet
  •  Sample location

Determine the level of contamination.

•       People living  in residences A and C are subject to Level I concentrations because their
        residence is within 200 feet of a Level I sample on their property.

•       People living in residence B are subject to Level II concentrations because their residence
        is within 200 feet of an inferred area of contamination on their property.

Assign points for the  resident individual factor.  In this example,  assign a value of 50, because at
least one resident individual Is subject to Level I concentrations.

Evaluate the resident population factor.

•       The 8 people living in residences A and C are subject to Level I concentrations.  Level  I
        concentration factor value = 8 x 10 = 80

•       The 3 people living  in residence  B are subject to Level II concentrations.  Level  II
        concentration factor value = 3

•       Sum the Level I and Level II values to obtain the resident population factor value,. Resident
        population factor value = 80 + 3 = 83
                                             367
                                                                                         Section 9.4

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                                      HIGHLIGHT 9-11
    SCORING EXAMPLE FOR  MULTIPLE RESIDENCES ON ONE PROPERTY

  This example illustrates how to determine whether targets are subject to Level I or Level II concentrations, and
  how to score the resident individual and resident population factors for a single property containing a number
  of residences (e.g., trailers). All residences in the figure below are within one property boundary.
  (1)
  (2)


  (3)
          Level I
                            AREA OF OBSERVED
                             CONTAMINATION
                                                 Level II
              Level I

                A
                         Level I

                         C
 Level II

E        F
H
              100 feet
              Sample location
Determine the level of contamination.

        People living in residences A, B, C, D, and E are subject to Level I concentrations because
        they are within 200 feet of a Level I sample on their property.

.       People living In residences F and G are subject to Level II concentrations because F and G
        are within 200 feet of a Level II sampling point on their property, but not within 200 feet of
        a Level I sampling point.

•       People living in residence H are not evaluated as resident individuals because H is not within
        200 feet of an area of observed contamination.

Assign points for the resident Individual factor. In this example, assign a value of 50, because
there is at least one resident individual subject to Level I  concentrations.

Evaluate the resident population factor.

•       The 18 people living in residences A, B, C, D, and E are subject to Level I concentrations.
        Level I concentration factor value  = 18 x 10 = 180

•       The 8 people living in residences  F and G are subject to Level II concentrations. Level II
        concentration factor value = 8

•       Sum the Level I and Level II values to obtain the  resident population factor value. Resident
        population factor value = 180 + 8 = 188
Section 9.4
                                                 368

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TIPS AND REMINDERS

       Evaluate and document the resident population factor accurately because a relatively small
       increase in the number of targets can significantly affect the site score.

       Because individuals can be exposed both at home and at school, count a student twice if that
       student attends school and resides within 200 feet of an area of observed contamination on a
       property with an area of observed contamination. Count teachers who both live and work in
       such areas once in the resident population factor value and once in the worker factor value (see
       Section 9.5).

       A property can be inferred to have observed contamination if the property lies between points of
       observed contamination, unless information indicates otherwise. Level I concentrations,
       however, generally should  not be inferred across property boundaries.

       Do not count transient populations such as customers and travelers passing through the area.

       When scoring a school population for the resident threat, score teachers as workers and score
       students (including college students) as resident individuals if the school is on a  property with an
       area of observed contamination and the school is within 200 feet of the  area of observed
       contamination.

       If individuals abandoned schools, homes, or workplaces for reasons related to site
       contamination, score these individuals as targets in the appropriate factor. If the  individuals
       abandoned their schools, homes, or workplaces for reasons other than the site contamination, do
       not score the individuals as targets.
                                             369                                      Section 9.4

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SECTION  9.5
WORKERS  AND
RESOURCES
       This section provides guidance for evaluating workers and scoring the resources factor for the
targets factor category in the resident population threat of the soil exposure pathway. The workers factor
is used to score the targets factor category of the resident population threat. The scorer must consider
the number of workers who frequent workplace areas on or near the area of observed contamination.
The resources factor evaluates the possible loss of resource use resulting from surficial contamination at
a site. The factor evaluates the presence of commercial agriculture, commercial silviculture, commercial
livestock production, and commercial livestock grazing; it does not evaluate threats to human health or
sensitive environments.
                              RELEVANT MRS SECTION

        Section 5.1.3              Targets
        Section 5.1.3.3             Workers
        Section 5.1.3.4             Resources
        Section 5.1.3.6             Calculation of resident population targets factor category value
DEFINITIONS
       Commercial Agriculture: Production of crops for sale, including crops intended for widespread
       distribution (e.g., supermarkets) and more limited distribution (e.g., local produce stands), and
       any nonfood crops such as cotton and tobacco. Commercial agriculture does not include
       livestock production, livestock grazing, or crops grown for household consumption (e.g.,
       backyard garden or fruit trees).

       Commercial Livestock Production or Commercial Livestock Grazing:  Raising or feeding of
       livestock for sale.

       Commercial Silviculture: Cultivation of trees for sale  (e.g., Christmas tree farm, trees raised
       for lumber).

       Worker: A person working on a property with an area of observed contamination and whose
       workplace area is on or within 200 feet of an area of observed contamination. Both full and
       part-time workers are considered.

       Workplace Area: Any area where workers are regularly present. Areas receiving only brief but
       regular use (e.g., parking areas, lunch areas) may qualify as work areas.
                                           371                                    Section 9.5

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EVALUATING THE WORKERS FACTOR

       Workers are not resident individuals and therefore cannot be used to score either the resident
individual or resident population factors. Workers can  be used to score the workers factor of the
resident population threat as long as their workplace qualifies as an area of observed contamination.
Highlight 9-12 provides an example of scoring workers in the soil exposure pathway. Follow the steps
below to score the workers factor.

(1)     Identify areas of observed contamination. Section 9.1 provides detailed instructions for
       identifying areas of observed contamination.

(2)     Determine which groups of workers have workplace areas within 200 feet of the  area of
       observed contamination.  Refer to facility maps and descriptions of job responsibilities.

(3)     Evaluate the workers factor value based on the number of workers that meet the criteria
       above. Contact the workplace directly, remembering that the factor value is assigned  based on
       broad ranges of numbers. Thus, it is not necessary to obtain an exact count of workers.

(4)     Assign a value for these workers using MRS Table 5-4.
                                    HIGHLIGHT 9-12
          EVALUATING WORKERS AT A MULTIPLE-BUILDING FACILITY

  This example illustrates how to evaluate workers at a facility with more than one workplace area.
                                               200 feet
                 Building 1
                                         Building 2
                                                                     Building 3
  Building 1 has approximately 50 workers,  Building 2 has approximately 125 workers, and Building 3 has
  approximately 250 workers.  All the buildings and the area of observed contamination are within the same
  property boundary.

  Count workers in Buildings 1  and 2 as targets in the soil exposure pathway.  Do not count workers in
  Building 3 because they do not work within 200 feet of the area of observed contamination and are not
  expected to frequent Buildings 1 or 2 on a regular basis.

  The total number of qualifying workers is 175. Assign the workers factor a value of 10, using HRS Table 5-9.
Section 9.5
                                             372

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SCORING THE RESOURCES FACTOR

(1)     Determine if any land uses for which resource points are assigned are located on areas of
       observed contamination. See Highlight 9-13. Use the definitions above in making this
       determination. The resource use must be within the boundary of the area of observed
       contamination. Highlight 9-14 provides sources of information that may help document
       resources at the site.

(2)     If a resource use Is documented, assign a value of 5 to the resources factor for the site.
       If no resource use is documented, assign a value of 0.
                                    HIGHLIGHT 9-13
                    CHECKLIST FOR THE RESOURCES FACTOR

 For the site being evaluated:

  (1)    Is commercial agriculture present on an area of observed              Yes      No
        contamination at the site?

 (2)     Is commercial silviculture present on an area of observed              Yes      No
        contamination at the site?

 (3)     Is commercial livestock production or commercial                    Yes      No
        livestock grazing present on an area of observed
        contamination at the site?
 If the answer is "yes" for any of the possibilities above, assign a resources factor value of 5. Otherwise, assign
 a resources factor value of 0. Remember that "yes" should be circled only if an activity takes place ori an area
 of observed contamination.
                                    HIGHLIGHT 9-14
                  DATA SOURCES FOR THE RESOURCES FACTOR

 The following sources of information may help in documenting resource use for a site:

 •      Agricultural extension agents
 •      Correspondence with nearby businesses
 •      Correspondence with other nearby institutions, such as farms or universities
 •      County land use maps
        PA/SI reports
 •      Field observations
 •      Files from adjacent or nearby CERCLIS sites
 •      Local chambers of commerce
 •      Soil Conservation Service State departments of natural resources or state environmental
        departments, especially forestry departments
 •      The U.S. Department of Agriculture/U.S. Forest Service
 •      Topographic maps.
                                            373                                     Section 9.5

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TIPS AND REMINDERS

       Likelihood of exposure rather than duration is the important factor in determining if an individual
       may be exposed to hazardous substances at a workplace area. For example, workers who
       frequent a lunch area or administrative building located within 200 feet of an area of observed
       contamination may be counted as workers, even if their "regular" workplace area is more than
       200 feet from the area of observed contamination.

       When evaluating school populations, score students as resident individuals if they attend school
       on a property with an area of observed contamination and the school is within 200 feet of the
       area of observed contamination. Score teachers at such a school as workers, and not as
       residents.

       In general, do not expend resources to determine if there is any overlap in student, worker, and
       resident populations (i.e., do not try to determine where students or workers live).

       Only 5 targets points are assigned for the resources factor. Do not spend significant time
       documenting resource use unless those 5 points may be critical to the site score.
Section 9.5                                     374

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SECTION  9.6
TERRESTRIAL
SENSITIVE
ENVIRONMENTS
       This section provides a method for identifying terrestrial sensitive environments and for
calculating the terrestrial sensitive environments factor value in the soil exposure pathway. Definitions of
all terrestrial sensitive environments and specific sources of information for identifying terrestrial
sensitive environments are provided in Appendix A. Only those areas that meet the definitional criteria
for one or more terrestrial sensitive environments listed in MRS Table 5-5 are eligible for evaluation. All
terrestrial sensitive environments located partially or wholly on the area of observed contamination are
eligible. Because there are no applicable benchmarks for sensitive environments in the soil exposure
pathway, they are always considered subject to Level II concentrations.
                             RELEVANT MRS SECTIONS

          Section 5.1             Resident population threat
          Section 5.1.3            Targets
          Section 5A.3.5          Terrestrial sensitive environments
DEFINITIONS
       Area of Observed Contamination:  Established based on sampling locations as any of the
       following:

              Generally, for contaminated soil, consider the sampling locations that indicate observed
              contamination and the area lying between such locations to be an area of observed
              contamination, unless information indicates otherwise.

              For sources other than contaminated soil, if any sample taken from the source indicates
              observed contamination, consider that entire source to be an area of observed
              contamination.

       If an area of observed contamination (or a portion of such an area) is covered  by a permanent,
       or otherwise maintained, essentially impenetrable material (e.g., asphalt), exclude the covered
       area from the area of observed contamination. However, asphalt or other impenetrable materials
       contaminated by site-related hazardous substances may be considered areas  of observed
       contamination.

       Observed Contamination:  Surficial contamination related to a site. It must be established by
       chemical analysis. Observed contamination is present at sampling locations where analytic
       evidence indicates that:

              A hazardous substance attributable to the site is present at a concentration significantly
              above background levels for the site (i.e., meets the observed release criteria in MRS
              Table 2-3).


                                          375                                   Section 9.6

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              The hazardous substance is present at the surface or covered by two feet or less of
              cover material (e.g., soil).

Terrestrial Sensitive Environment: A terrestrial sensitive environment is defined as any area that
meets the criteria listed in MRS Table 5-5. No other areas are considered terrestrial sensitive
environments. Appendix A defines each terrestrial sensitive environment and provides sources for
identifying terrestrial sensitive environments. Sensitive environments that are eligible to be scored in the
soil exposure pathway and their assigned point values are as follows:

              Terrestrial critical habitat for Federal designated endangered or threatened species (100
              points);
              National Park (100 points);
              Designated Federal Wilderness Area (100 points);
              National Monument (100  points);
              Terrestrial habitat known  to be used by Federal designated or proposed threatened or
              endangered species (75 points);
              National Preserve (terrestrial) (75 points);
              National or state Wildlife  Refuge (terrestrial) (75 points);
              Federal land designated for protection of natural ecosystems (75 points);
              Administratively proposed Federal Wilderness Area (75 points);
              Terrestrial areas utilized for breeding by large or dense aggregations of animals  (75
              points);
              Terrestrial habitat known  to be used by state designated endangered or threatened
              species (50 points);
              Terrestrial habitat known  to be used by species under review as to its Federal designated
              endangered or threatened status (50 points);
              State lands designated for wildlife or game management (25 points);
              State designated Natural Areas (25 points); and
              Particular areas, relatively small in size, important to maintenance of unique biotic
              communities (25 points).

SCORING TERRESTRIAL SENSITIVE ENVIRONMENTS

       Many terrestrial sensitive environments will be relatively easy to identify and delineate with
readily available  materials (e.g., maps or  EPA Regional files for other sites located near the site being
evaluated); more in-depth investigation may be necessary to determine if other types of terrestrial
sensitive environments are within the area of observed contamination. The following steps will help
identify and score the terrestrial sensitive environments listed in MRS Table 5-5.

(1)     Determine the areas of observed contamination. See Section 9.1. Determining Level I or
       Level II concentrations Is not necessary in evaluating terrestrial sensitive environments

(2)     Identify and delineate all eligible terrestrial sensitive environments. All terrestrial sensitive
       environments (i.e., those listed in MRS Table 5-5) that are at least partially on an area of
       observed contamination are eligible. The 200-foot rule for resident populations does not apply to
       terrestrial sensitive environment targets.  Property boundaries are not considered.

              Obtain a USGS topographic map of the area. Maps  are available from USGS map
              stores, most outdoor stores, and local outfitters. Delineate areas of observed
              contamination on the topographic map.

              Identify terrestrial sensitive environments delineated on the map. The following
              terrestrial sensitive environments are likely to be found on USGS topographic maps:
Section 9.6                                     376

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—     National Park
—     Designated Federal Wilderness Area
—     National Monument
—     National Preserve (terrestrial)
—     National or state terrestrial wildlife refuge
—     State lands designated for wildlife or game management (in some cases).

In many cases, the level of detail provided by USGS maps will be sufficient for HIRS
purposes. In other cases, more specialized maps or professional judgment may be
needed.

Obtain additional maps, documents, or other relevant information to determine whether
other terrestrial  sensitive environments are at least partially on an area of observed
contamination. The following sensitive environments may be delineated on specialized
maps, charts, or other special documents available from various  Federal and state
agencies:

—     Terrestrial critical habitat for Federal designated endangered or threatened
       species (in some cases);

—     Federal land designated for the protection of natural ecosystems;

—     Administratively proposed Federal Wilderness Areas;

—     State lands designated for wildlife or game management; and

—     State designated Natural Areas.

Sources of information on sensitive environments and specific guidance for obtaining
specialized maps is provided in Appendix A.

If all potential terrestrial sensitive environments can be identified and delineated using
USGS topographic maps and other specialized maps, no further investigation will be
necessary. However, many sensitive  environments are not delineated on either USGS or
specialized maps, so other sources may need to be consulted.

Contact appropriate Federal, state, or local agencies if an area not delineated on a map
may be a terrestrial sensitive environment. The following terrestrial sensitive
environments generally are not delineated on maps or otherwise described in specialized
publications.

—     Terrestrial habitat known to be used by Federal designated or proposed
       endangered or threatened species;

—     Terrestrial areas utilized for breeding by large or dense aggregations of
       animals;

—     Terrestrial habitat known to be used by state designated endangered or
       threatened species;

—     Terrestrial habitat known to be used by species under review as to its Federal
       endangered or threatened status; and

—     Particular areas, relatively small in size, important to maintenance of unique
       biotic communities.
                               377                                      Section 9.6

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               The assistance of appropriate Federal, state, or local agencies or recognized experts in
               identifying these sensitive environments is encouraged. Try to obtain copies of any
               published information that helps to establish the area as a sensitive environment and/or
               delineate its boundaries. If possible, obtain a written statement from a responsible
               agency official verifying the existence and boundaries of the terrestrial sensitive
               environments. For guidance on identifying these sensitive environments and on sources
               of information to delineate these sensitive environments, see Appendix A.

               Draw the boundaries of each terrestrial sensitive environment on the USGS topographic
               map or a scale map of the site. While this step is optional, it may be helpful in
               delineating the terrestrial sensitive environments.

(3)     Assign a point value for the terrestrial sensitive environment(s). Assign the appropriate
       point value from MRS Table 5-5 to each terrestrial sensitive environment at least partially on an
       area of observed contamination. If more than one point value applies to a single area of
       observed contamination, go to Step (4), otherwise go to Step (5).

(4)     If more than one point value applies to a single area of observed contamination:

               Score each discrete physical area  identified as a terrestrial sensitive environment as a
               separate target for MRS purposes, regardless of the degree of overlap with other
               terrestrial sensitive environments.

               Treat "critical habitat for" or "habitat known to be used by" endangered or threatened
               species as follows:

                      Identify at least one distinct habitat for each  individual species (e.g., if there are
                      three different species, identify three or more habitats - even if they partially or
                      completely overlap).

                      For each species, assign the category with the highest point value. For example,
                      if the same species is both a Federal proposed threatened species (75 points),
                      and a state designated endangered species (50 points), evaluate the species as
                      a Federal proposed threatened species.

                      If there is overlap between "critical habitat for" and "habitat known to be used by"
                      the  same species, consider the overlapping area to be only a "critical habitat"
                      for MRS purposes (i.e., do  not consider the zone of overlap as both "critical
                      habitat for" and  "habitat used by" the species).

(5)     Calculate the total targets value for terrestrial sensitive environments. Because only those
       terrestrial sensitive environments wholly or partially on an area of actual contamination are
       evaluated as targets in the soil exposure pathway, and no ecological-based benchmarks are
       used, do not evaluate levels of concentrations for terrestrial sensitive environments in the soil
       exposure pathway. To obtain the total targets value for sensitive environments (ES), sum
       assigned point values for all terrestrial sensitive environments wholly or partially on an area of
       actual  contamination.

(6)     Calculate the terrestrial sensitive environments factor value. Because the soil exposure
       pathway score based solely on terrestrial sensitive environments is limited to 60 points, the
       method for determining the terrestrial sensitive environments factor value depends on the total
       targets value for sensitive environments (ES - calculated in Step (5) above), the likelihood of
       exposure value for the resident population  threat  (LE - 550 points for the resident population
       threat), and the waste characteristics value for the resident population threat (waste
       characteristics (WC) - see Section 9.2).


Section 9.6                                      378

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               Multiply the values assigned to the resident population threat for LE, WC, and ES and
               divide this product by 82,500.

                                       s _ (LE)(WC)(ES)
                                               82,500

               If the resulting score (S) is 60 or less, assign  ES as the terrestrial sensitive environments
               factor value.

               If the resulting score (S) is greater than 60, assign only that portion of ES that will result
               in a resident population threat score of 60 as the terrestrial sensitive environments factor
               value. This value, termed EC, is calculated as follows:
                                                     4,950,000
(7)
                          PC - (6°)(82'50°)
                                 (LE)(WQ

       Since all the values in this equation are constants except WC, only one EC value
       corresponds to each WC value. These values are presented \r\Highlight9-15. Do not
       round EC to the nearest integer.

       Highlight 9-16 illustrates how to score terrestrial sensitive environments.

The value calculated In Step (6) (either ES or EC) Is added to the values for resident
individual, resident population, workers, and resources, to calculate the total targets
score.
Becai
thepr
by 82
envirc
ECar
HIGHLIGHT 9-15
EC VALUES CORRESPONDING TO
WASTE CHARACTERISTICS FACTOR VALUES
jsethe soil exposure pathway score based solely on terrestrial sensitive environments is limited to 60 points,
oduct of the likelihood of exposure (LE), waste characteristics (WC), and sensitive environments (ES) divided
500 cannot exceed 60. If this value does exceed 60, the scorer calculates the maximum value for sensitive
)nments that will not exceed 60. (I.e., the value of EC). Because all the values in this equation for calculating
e constants except WC, there is only one EC value associated with each WC factor value.
Waste Characteristics Factor Value
1
2
3
6
10
18
32
56
100
EC Value
9000
4500
3000
1500
900
500
281.25
160.71
90


                                             379
                                                                                       Section 9.6

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                                       HIGHLIGHT 9-16
      SCORING EXAMPLE FOR TERRESTRIAL SENSITIVE ENVIRONMENTS
                                               Terrestrial Habitat
                                              Known to be Used by
                                               Federal Designated
                                              Endangered Species
National Park
                                                            State Terrestrial
                                                             Wildlife Refuge
                          Area of Observed
                           Contamination
  At this site, the area of observed contamination has been determined, the assigned value for likelihood of
  exposure (LE) is 550, and the assigned value for waste characteristics (WC) is 100. Three terrestrial sensitive
  environments are identified and delineated as shown.

  •       The National Park and the terrestrial habitat known to be used by a Federal endangered species are
          identified as eligible to be evaluated in the soil exposure pathway because each  is partially on the
          area of observed contamination.  The state terrestrial wildlife refuge is not eligible because It is not
          partially within the area of observed contamination.

          The National Park is assigned a point value of 100 from HRS Table 5-5 and the habitat known to be
          used by the endangered species is assigned a point value of 75 from HRS Table 5-5.

  •       The total targets value for sensitive environments (ES) is determined by summing the assigned point
          values for the National Park and the habitat known to be used by the endangered species (i.e.,  100
          + 75  = 175).

  •       The terrestrial sensitive environments factor value is  determined as follows:

          —      The values for LE, WC, and ES are multiplied and divided by 82,500 to obtain the score (S)
                  of 116.67.

          —      Because 116.67 is greater than 60, the value EC = 90 is calculated by dividing (60 x 82,500)
                  by (LE x WC).
                  EC = 4,950,000/55,000 = 90

          —      The terrestrial sensitive environments factor was assigned a value of 90  (i.e., EC).
Section 9.6
                                                 380

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TIPS AND REMINDERS

       The 200-foot rule for resident populations does not apply to sensitive environment targets.
       Sensitive environments must be listed in MRS Table 5-5 and be at least partially on the area of
       observed contamination to be evaluated as a terrestrial sensitive environment in the soil
       exposure pathway.

       If overlapping sensitive environments (i.e., those listed in MRS Table 5-5) are at least partially on
       an area of observed contamination, evaluate each sensitive environment separately, with certain
       restrictions for habitats of endangered or threatened species.

       The sensitive environment category "wetland" is not evaluated in the soil exposure pathway.
       However, portions of wetlands that are periodically out of water and  that meet the criteria for one
       or more terrestrial sensitive environment categories may be evaluated as that type of sensitive
       environment.

       Terrestrial sensitive environments are evaluated only  in the resident population threat, not in the
       nearby population threat.
                                             381                                      Section 9.6

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SECTION 9.7
ESTIMATION  OF
NEARBY  POPULATION
THREAT SCORES
E
       This section is designed to estimate the maximum score that can be expected from the nearby
population threat of the soil exposure pathway before beginning the detailed scoring process. This
section presents general formulae and took-up tables that provide estimates of nearby population threat
scores. Section 9.8 provides guidance on scoring the nearby population threat. Because the nearby
population threat evaluates only non-residents and students coming onsite, nearby population threat
scores tend to be low. Therefore, sites must be relatively accessible and attractive, with a fairly large
nearby population, to obtain a significant score or to warrant detailed scoring of the threat. This section
provides guidance for estimating nearby population, the area of observed contamination, and the
maximum expected nearby population threat score.  This section is intended as a general guideline and
should not be used to determine whether nearby population threat should be scored.

DEFINITIONS

       Nearby Population: Total number of people who live or attend school within a 1 -mile travel
       distance of an area of observed  contamination and  who do not meet the criteria for resident
       individual.

       Resident Individual: A person who lives or attends school or day care on a property with an
       area of observed contamination  and whose residence, school, or day care center, respectively,
       is on or within 200 feet of the area of observed contamination. Section 9.3 provides guidance for
       identifying resident individuals.

ESTIMATING NEARBY POPULATION THREAT SCORE

       Follow these steps to quickly determine if detailed scoring and documentation of the nearby
population threat is warranted.

(1)     Estimate nearby population. Estimate nearby population using one of the following three
       approaches:

              In the first method, if nearby population data are readily available for each of the three
              travel distance categories (i.e., >0 to 1/4 mile, >1/4 to 1/2 mile,  >1/2 to 1 mile),
              determine the distance-weighted population value from MRS Table 5-10.

              In the second method, nearby population data are not readily available, obtain a recent
              estimate of population density in the vicinity of the site and  use this estimate to
              approximate nearby  population (seeHighlight 9-17). Assume that the travel distance
              categories are delineated by concentric circles  around the areas of observed
              contamination and that the local population  is evenly distributed within the TDL. If
              information suggests otherwise (e.g., no one lives within 1/2 mile of the site), adjust the
              estimate of nearby population.

                                         383                                  Section 9.7

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                                    HIGHLIGHT 9-17
               APPROXIMATE DISTANCE-WEIGHTED POPULATION
              VALUES BASED ON LOCAL POPULATION DENSITY (D)a
Approximate Dimension of
Area of Observed
Contamination
1 .8 acres
1 26 acres
3.2 square miles
Travel Distance Category
>Oto1/4
>1/4to1/2
>1/2to1
>Oto1/4
>1/4to1/2
>1/2to1
>Oto1/4
>1/4to1/2
>1/2to1
Approximate Population b|C
0.2 xD
0.6 xD
2.4 xD
0.6 xD
1.0 xD
3.1 xD
1.8 xD
2.2 xD
5.5 xD
               a D = local population density (people per square mile).
               b Formulas assume concentric travel distance categories.
               c See MRS Table 5-10 to determine the approximate distance-weighted population value.
              In the third method, if local population density cannot be readily estimated, estimate
              population density based on whether the site is located in an urban, suburban, or rural
              area. Typically population densities (people per square mile) for these areas are as
              follows: 5,100 (large urban area), 1,300 (suburban or urban in small city),  300 (rural).

(2)     Determine the approximate maximum nearby threat score assuming maximum values for
       waste characteristics and likelihood of exposure. To determine an approximate upper-bound
       limit for the nearby population threat score, assume the maximum waste characteristics factor
       category value (i.e., 100) and the maximum likelihood of exposure factor category value (i.e.,
       500).

              If an approximate distance-weighted population value is obtained using methods 1  or 2
              under Step (1), determine the approximate maximum nearby population threat score by
              multiplying the result by 0.061  (i.e., (100 x 500)782,500).

              If a nearby population is estimated using method 3 under Step (1),Highlight 9-18 can
              be used to estimate maximum nearby population threat score (Highlight 9-18 also
              assumes concentric travel distance categories and an evenly distributed population).

       Highlight 9-18 can also be used to determine a range of maximum nearby population threat
       scores when  population density data are available from method 2  under Step (1). From the
       population density data, area of observed contamination, and likelihood of exposure factor,
       estimate the maximum nearby population threat score. For example, for a medium site with
       maximum values for likelihood of exposure and waste characteristics factor categories, and a
       population density of 2,500 people per square mile, the maximum nearby population threat score
       is between 4  and 13.

       If the approximate maximum nearby threat scores suggest that it may be worthwhile to score the
       nearby population threat,  proceed to Step (3).
Section 9.7
                                            384

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HIGHLIGHT 9-18



















APPROXIMATE NEARBY POPULATION THREAT SCORES a
Area of
Observed
Contamination



1.8 acres






126 acres






3.2 square miles



Likelihood
of
Exposure
500
375
250
125
50
25
5
500
375
250
125
50
25
5
500
375
250
125
50
25
5
Population Density (people per square mile)
50 100 500 1,000 5,000 10,000 50,000
1 1 1 2 9 13 83
1 1 1 1 7 10 62
00114 7 41
00012 3 21
00001 1 8
00000 1 4
00000 0 1
1 1 2 4 13 32 100
111 3 10 24 95
0 0 1 2 7 16 63
00013 8 32
00001 3 13
00001 2 6
00000 0 1
1 1 3 6 27 58 100
1 1 2 5 20 43 100
012 3 14 29 100
0 0 1 2 7 14 66
00013 6 26
00001 3 13
00000 1 3
a The scores presented in this table assume a waste characteristics factor category value of 1 00, nearby
individual factor value equal to one, concentric travel distance categories, and uniformly distributed population (see text).
Also, these values reflect the nearby population threat's overall effect on the soil exposure pathway score (i.e., they are
divided by 82,500).



















385
                                                Section 9.7

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(3)     Determine the approximate maximum nearby population threat score assuming maximum
       value for waste characteristics. If the maximum approximate nearby population threat score
       suggests that it may be worthwhile to score the nearby population threat, obtain a more realistic
       upper bound on the nearby population threat score by estimating likelihood of exposure (and
       continuing to assume maximum waste characteristics). The likelihood of exposure factor
       category value is based on area of contamination and attractiveness/accessibility.

               Determine the approximate area of observed contamination. If the area of contamination
               is known or can easily be determined  or estimated (e.g., areas of observed
               contamination are limited to surface impoundments or other areas with known
               dimensions), determine the area of contamination factor value using MRS Table 5-7. If
               the area of contamination is less apparent, use Highlight 9-19 \o determine the area of
               contamination factor value that best approximates the maximum size of the  area(s) of
               observed  contamination for the site.

               Determine the approximate maximum attractiveness/accessibility factor value. If any
               area of observed contamination is within a designated recreational area, national park,
               or other similar area, assign an attractiveness/accessibility factor value of 100.
               Otherwise, assume an attractiveness/accessibility factor value of 75.

               Estimate likelihood of exposure. Use the estimated  area of contamination factor value
               and the estimated attractiveness/accessibility factor value to approximate the likelihood
               of exposure factor category value, using Highlight 9-20.

               Determine the approximate nearby population threat score. FromHighlight9-18,
               estimate the approximate nearby population threat score using the estimate for the
               likelihood of exposure factor category. Remember that this step still assumes a waste
               characteristics factor value equal to 100. Score the nearby population threat only if this
               approximate nearby population threat score suggests that it is worth proceeding further.
               To  actually score the nearby population threat, follow MRS section 5.2 and Section 9.8.
Section 9.7                                     386

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HIGHLIGHT 9-19
ESTIMATED AREA OF CONTAMINATION FACTOR VALUES







Assigned Factor Value for
Area of Contamination
5
20
40
60
80
100
Minimum Area of
Contamination Needed to
Score Factor Value
(square feet)
>0
>5,000
>125,000
>250,000
>375,000
>500,000
Diameter of Contaminated
Circular Area Needed to
Achieve Value (feet)
>0
80
400
565
690
800








HIGHLIGHT 9-20
ESTIMATED NEARBY POPULATION LIKELIHOOD OF
EXPOSURE FACTOR VALUES

Attractiveness/
accessibility
Factor Value
100
75
Area of Contamination Factor Value
100 80
500 500
500 375
60
375
250
40
250
125
20
125
50
5
50
25


387
                                                Section 9.7

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SECTION  9.8
EVALUATION  OF NEARBY
POPULATION THREAT
       This section provides guidance for scoring the nearby population threat of the soil exposure
pathway. The nearby population threat targets factor category reflects the non-resident population
potentially at risk from exposure to contaminated soil or other contaminated surficial materials. This
section provides instruction for scoring the likelihood of exposure, waste characteristics, and targets
factor categories. In addition, this section clarifies how to determine travel distance.
          Section 5.0.1
          Section 5.2
          Section 5.2.1.1
          Section 5.2.1.2
          Section 5.2.3
                             RELEVANT MRS SECTIONS
General considerations
Nearby population threat
Attractiveness/accessibility
Area of contamination
Targets
DEFINITIONS
       Nearby Individual: Resident or student with the shortest travel distance to any area of
       observed contamination. If one or more individuals meet the criteria for resident individual, the
       nearby individual factor value is zero.

       Nearby Population: Total number of people who live or attend school within a 1-mile travel
       distance of an area of observed contamination and who do not meet the criteria for resident
       individual.

       Public Recreation Area: Publicly or privately owned area used for recreation by individuals not
       evaluated as workers in the resident  population threat.

       Resident Individual: A person who  lives or attends school or day care on a property with an
       area of observed contamination and  whose residence, school, or day care center, respectively,
       is on or within 200  feet of the area of observed contamination. Section 9.3 provides guidance for
       identifying resident individuals.

       Travel Distance: The shortest overland distance an individual would travel from a residence or
       school to the nearest area of observed contamination, considering natural barriers (e.g., ravines,
       streams). If there are no natural barriers, the travel distance is the shortest straight-line distance.
                                          389
                                                                               Section 9.8

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SCORING THE LIKELIHOOD OF EXPOSURE FACTOR CATEGORY

       To score the likelihood of exposure factor category for the nearby population threat, determine
the attractiveness/accessibility factor value and the area of contamination factor value for the areas of
observed contamination as follows.

(1)     Assign the attractiveness/accessibility factor value. Assign each area  of observed
contamination a value for attractiveness/accessibility, excluding any area of observed contamination on
a residential property. If an area falls into two or more categories, use the higher score. Select the
highest value assigned to the areas evaluated and use it as the attractiveness/accessibility factor value
for the site. If the attractiveness/accessibility factor value fora site is 0, the nearby population threat
score will be 0.

       Highlight 9-21, which is based on MRS Table 5-6, provides attractiveness/accessibility factor
       values along with examples of the types of areas that would receive a given value. Public
       recreation use can  be activities such as walking, sports, fishing, air shows, and hayrides, and  can
       occur on public or private lands. The examples presented \r\Highlight9-21 are not exhaustive.
       Select the best-fitting category and document why it was selected.

(2)     Determine the area of contamination factor value.  The area of contamination factor value is
       based on the total area of all areas of observed contamination at the site with an
       attractiveness/accessibility factor value greater than 0. To determine the area of contamination
       factor value:

              Identify all areas of observed contamination with an attractiveness/accessibility value
              greater than 0.

              Determine their total area.

              Assign the  approximate area of contamination factor value using MRS Table 5-7.

       Section 9.1 provides instruction on identifying areas of observed contamination.

(3)     Determine the likelihood of exposure factor category value. The likelihood of exposure
       factor category value is based on the values assigned to the attractiveness/accessibility and area
       of contamination factors. Use MRS Table 5-8 to assign this value. The maximum value is 500.

SCORING WASTE CHARACTERISTICS FACTOR  CATEGORY

       The waste characteristics factor category for the nearby population threat is scored as it is scored
for the resident population threat, except that the nearby threat considers only those areas of observed
contamination that have an attractiveness/accessibility factor value greater than 0. The waste
characteristic factor category value for the nearby population  threat, therefore, will be equal to or less
than that for the resident population threat. Section 9.2 provides guidance on scoring the waste
characteristics factor.

SCORING TARGETS FACTOR CATEGORY

       The targets factor category value for the nearby population threat is based on two factors: nearby
individual and population within a one-mile travel distance from the site. Sum these two factor values for
the targets factor category value.
Section 9.8                                     390

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HIGHLIGHT 9-21
EXAMPLES OF ATTRACTIVENESS/ACCESSIBILITY VALUES
Area of Observed Contamination
Designated recreational areas
Includes areas designed specifically to encourage recreational use.
Playground
Golf course (public or private)
Baseball field with backstop and maintained basepaths or infield
Areas with Improvements aimed at enabling people to view scenic attractions
Areas regularly used for public recreation
Includes areas used regularly for public recreation but not designated for such use.
Open fields where people play frisbee
Fields where people play baseball (provided that they are not maintained for
such use)
Accessible and unique recreational areas
Vacant lot in an urban area
Shoreline of stream in an urban area
Moderately accessible areas with some public recreation use
Includes areas used for recreation with some Improvements that increase accessibility
even if these improvements are not made specifically for the areas In question.
Undeveloped land along corridors to a recreational area where there are not
thousands of acres of similarly undeveloped land (e.g., areas adjacent to a road
or trail leading to a public lake or river)
Shoreline of public lakes or rivers that can be reached via moderately improved
roads (e.g., gravel or dirt)
Slightly accessible areas with some public recreation use
Includes areas used for public recreation but with few improvements that increase
accessibility to the areas. It can also include areas that have nothing unique about them
relative to their surroundings.
Shorelines of relatively remote public lakes (e.g., lakes that cannot be reached
by automobile)
Undeveloped land along corridors to a recreational area where there are
thousands of other acres of similarly undeveloped land along the corridor
Accessible areas with no public recreation use
Unfenced industrial or commercial site (guarded or not) with no vacant lots,
sand piles, or other recreational attractions
Abandoned lagoons or other surface impoundments in an industrial area
Areas surrounded by maintained fence or combination of maintained fence and
natural barriers
Fenced, unguarded industrial or commercial sites
Areas physically Inaccessible to public, with no evidence of public recreation use
Includes areas where (1 ) steps have been taken to absolutely preclude public access to
the areas or (2) natural conditions make access physically impossible.
Area off-limits to unauthorized personnel at guarded and fenced military base or
industrial complexes.
Assigned
Value
100
75
75
50
25
10
5
0


391
                                                 Section 9.8

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(1)     Determine the nearby Individual factor value. Determine the nearby individual factor value as
       follows:

               If one or more persons meet the criteria for resident individual (as specified in MRS
               section 5.1.3 and Section 9.4), assign a value of 0 for the nearby individual factor.

               If no person meets the criteria for a resident individual, determine the shortest travel
               distance from the site to  any residence or school. The travel distance is the shortest
               overland distance an individual would travel from a residence or school to the nearest
               area of observed contamination for the site with an attractiveness/accessibility factor
               value greater than 0.

               —      If there are no natural barriers to travel, measure the travel distance as the
                      shortest straight-line distance from the residence or school to the area of
                      observed contamination.

               —      If natural barriers exist (e.g., a river, a ravine), measure the travel distance as
                      the shortest distance that a person would be expected to travel to get from the
                      residence or school to the area of observed contamination, assuming the person
                      avoided these barriers (e.g., did not wade the stream or scale the ravine).

               If the travel distance of the nearby individual is less than or equal to 1/4 mile, the nearby
               individual factor value is 1; otherwise, this factor value is 0.

(2)     Determine the population within 1 mile. To score the population within 1 mile, determine the
       population within  each travel distance category (i.e., >0 to 1/4 mile, >1/4 to 1/2 mile, >1/2 to  1
       mile).

               Count residents and students who attend school within this travel distance. Do not
               include those people already counted in the resident population threaUexcept for
               individuals evaluated as workers in the resident population threat who are  not also
               resident individuals and who live within a one-mile travel distance).

               Determine travel distances for the population within one mile as specified for the nearby
               individual (i.e., determine the approximate travel distance from each residence and
               school to  the area of observed contamination; do not simply draw distance rings unless
               there  is only one area of observed contamination and there are no natural  or constructed
               barriers).

               For sites with multiple areas of observed contamination, two methods are generally used
               to determine a  representative score for populations within one mile for the  nearby threat.

               —      In the first method (see Highlight 9-22),  draw travel distance categories around
                      each area of observed contamination (however, do not draw distance categories
                      across natural barriers), determine aggregate travel distance categories (e.g.,
                      make overlapping rings of the same travel distance one travel distance
                      category), and total the population within each travel distance category. The total
                      population is then used to determine the factor value assigned for population
                      within one mile. Assign each individual to the travel distance category nearest to
                      an area of observed contamination (e.g.,  an individual within one-quarter mile of
                      one area of observed contamination and one-half mile of another area of
                      observed contamination is counted only  in the zero to one-quarter  mile distance
                      category). Also, count individuals only once, except for  individuals  who are both
                      residents and students.

Section 9.8                                      392

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                             HIGHLIGHT 9-22
         ESTABLISHING TARGET DISTANCE CATEGORIES
                 FOR NEARBY THREAT:  METHOD 1
                                                                   > 1/4 to 1/2
                                                                   >1/2to1
 'IT = Residence

AOCX = Area of observed contamination
 Each sample location establishes an area of observed contamination. Due to site-specific conditions,
 it is not appropriate to connect the points into one area of observed contamination.

 Draw travel distance categories from each area of observed contamination and then aggregate travel
 distance categories.

 Sum the population within each travel distance category (excluding those counted in the resident
 population) to determine the total population within each travel distance category. From HRS Table
 5-10, determine the population within one mile factor value,

 If no individual qualifies  as a resident individual, use the resident nearest  an area of observed
 contamination to determine the nearby individual factor value.

 Do not include residences on the far side of the river, even though they are within one mile in straight-
 line distance,  because they are  not within a one-mile  travel distance of the area of observed
 contamination.

 This method may be unwieldy for sites with many areas of observed contamination.

                                     393
                                                                               Section 9.8

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              —     At sites with a large number of areas of contamination, this method may be
                     time-consuming and inefficient. Because factor values are assigned based on
                     population ranges within each travel distance category, a simplified method may
                     be used with little or no impact on the threat source.

              —     In the second method (see Highlight 9-23), rather than calculate the population
                     within one mile for all areas of contamination, determine which area(s) of
                     observed  contamination will give the highest  score for the site based on travel
                     distances to populations and population densities. Draw travel distance
                     categories only for these areas of contamination. This method is most effective
                     for sites with a large number of areas of contamination, and for sites with large
                     population densities, but it may underestimate target scores.

              When the number of residences within a travel distance category are used to estimate
              the population,  multiply each residence by the average number of people per residence
              for the county in which the residence is located.

              When the number of people within each travel distance have been determined, assign
              the appropriate distance-weighted population value for that travel distance from MRS
              Table 5-10. Sum these distance-weighted population values and divide the total by ten.
              If this number is less than one, do not round it to the  nearest integer; otherwise,  round to
              the nearest integer.  This value is the population within one-mile factor value.

(3)     Determine the nearby  population targets factor category value. Sum the values for the
       nearby individual factor and  the population within one mile factor. This sum is the targets factor
       category value for the nearby population threat.

CALCULATING THE NEARBY POPULATION THREAT SCORE

       To assign a score to the nearby population threat, multiply the values for likelihood of exposure,
waste characteristics, and targets for the nearby population  threat, and round the product to the  nearest
integer. Assign this product as the nearby population threat  score.
Section 9.8                                     394

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                            HIGHLIGHT 9-23
        ESTABLISHING TARGET DISTANCE CATEGORIES
                 FOR NEARBY THREAT:  METHOD 2
     River
                        AOC
                   AQ<
                           AOC,
VOC4
                                                                 > 0 to 1/4
                                                                 > 1/4 to 1/2
                                                                 >1/2tOl
 •  a Residence
AOCX % Area of observed contamination
  Each sample location establishes an area of observed contamination. Due to site-specific conditions,
  it is not appropriate to connect the points into one area of observed contamination.

  Decide which area(s) of observed contamination will likely give the most representative HRS score,
  and then draw travel distance categories from only those areas of observed contamination.

  Sum the population for each travel distance category and calculate the population within one mile
  factor value from HRS Table 5-10.

  If no individual qualifies as a resident, use the resident nearest an area of observed contamination to
  determine the nearby individual factor value.

  Do not include residences on the far side of the river, even though they are within one mile in straight-
  line  distance, because  they are not within a one-mile travel distance of the area of observed
  contamination.

  This method may underestimate target scores in some instances, but it may simplify  efforts at sites
  with many areas of observed contamination or dense populations, with little or no impact on the threat
  score.
                                      395
                                                                                Section 9.8

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TIPS AND REMINDERS

       Do not include in the nearby population individuals evaluated as resident individuals.

       Include in the nearby population individuals evaluated as workers for the resident population
       threat who are not resident individuals but live within a one-mile travel distance.

       Assign 0 as the nearby individual factor value if one or more persons meet the criteria for
       resident individual.

       Evaluate travel distance based on the shortest distance a person would be expected to travel,
       given existing natural barriers, which may not be the straight-line distance.

       Evaluate only areas of contamination with an attractiveness/accessibility factor value greater
       than 0 in the nearby population threat.

       When population  estimates are based on number of residences, multiply by average number of
       persons per residence for the county.
Section 9.8                                     396

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CHAPTER 10
AIR PATHWAY
 LIKELIHOOD OF
 RELEASE

 Observed Release or
 Potential to Release
  Gas
   Gas Containment
   Gas Source Type
   Gas Migration
      Potential
  Particulate
   Particulate
     Containment
   Particulate Source
     Type
   Particulate Migra-
     tion Potential
X
    WASTE
    CHARACTERISTICS

    Toxicity/Mobility
    Hazardous Waste
      Quantity
X
    TARGETS

    Nearest Individual
    Population
    Resources
    Sensitive
     Environments

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SECTION 10.1
OBSERVED  RELEASE
       This section provides guidance on demonstrating and documenting observed releases in the air
pathway and discusses observed releases established both by direct observation and by chemical
analysis. See Chapters for general guidance on scoring observed releases. The emphasis in this section
is on MRS scoring rather than field activities; only limited information is provided on monitoring,
sampling, handling, and analysis procedures. For the air pathway, documentation of observed releases
by direct observation does not involve the use of atmospheric sampling but is established through visual
observation of a release or through inferential observations (see discussion below). Observed releases
by chemical analysis require atmospheric sampling and laboratory analysis to establish the presence of
the chemical. EPA's Guidance for Conducting Site Inspections Under CERCLA (OSWER Publication
9345.1-05) provides information on sampling strategies for the air pathway.
                              RELEVANT MRS SECTIONS

        Section 2.3                Likelihood of release
        Section 6.1                Likelihood of release
        Section 6.1.1              Observed release
DEFINITIONS
       Attribution: The determination that a hazardous substance in a release is likely to have
       originated in one of the sources at a site. Attribution usually requires documenting that at least
       one hazardous substance found in a release at a concentration significantly above background
       (or directly observed in the release) was produced, stored, deposited, handled, or treated at the
       site; and at least a portion of the significant increase could have come from a source at the site.

       Background Level: The concentration of a hazardous substance that provides a defensible
       reference point that can be used to evaluate whether or not a release from the site has occurred.
       The background level should reflect the concentration of the hazardous substance in the medium
       of concern for the environmental setting on or near a site. Background level does not necessarily
       represent pre-release conditions, nor conditions in the absence of influence from source(s) at the
       site. A background level may or may not be less than the DL, but if it is greater than the DL, it
       should account for variability in local concentrations. A background level need not be established
       by chemical analysis.

       Background Sample: A sample used in establishing a background level.

       Contract Laboratory Program (CLP): The analytical program developed for CERCLA waste
       site samples to fulfill the need for legally defensible analytical results supported by a high level of
       quality assurance and documentation.
                                           397                                   Section 10.1

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       Contract-required Detection Limit (CRDL):  A term equivalent to the CRQL, but used
       primarily for inorganic substances.

       Contract-required Quantitation Limit (CRQL): The substance-specific level that a CLP
       laboratory must be able to routinely and reliably detect in specific sample matrices. The CRQL is
       not the lowest detectable level achievable, but rather the level that a CLP laboratory must
       reliably quantify. The CRQL may or may not be equal to the quantitation limit of a given
       substance in a given sample.  For MRS purposes, the term CRQL also refers to the CRDL.

       Detection Limit (DL):  The smallest quantity of a hazardous substance that can be distinguished
       from the normal random "noise" of an analytical instrument or method. For MRS purposes,  DL is
       the MDL or, for real-time field  instruments, the IDL as used in the field.

       Method Detection Limit (MDL): The lowest concentration of a hazardous substance that a
       method can detect reliably in either a sample or blank.

       Observed Release:  An observed release is established for the ground water, surface water, or
       air migration pathway either by chemical analysis or by direct observation. Observed release is
       not relevant to the MRS soil exposure pathway. The minimum requirements for establishing an
       observed release by chemical analysis are analytical data demonstrating the presence of a
       hazardous substance in the medium significantly above background level, and information that
       some portion of that increase  is attributable to the site. The minimum criterion for establishing an
       observed release by direct observation is evidence that the hazardous substance was placed into
       or has been seen entering the medium.

       Release Sample: A sample taken to determine whether the  concentration of a hazardous
       substance is significantly above its background level in order to determine whether an observed
       release (or observed contamination) has occurred.

       Sample Quantitation Limit (SQL): The quantity of a substance that can be reasonably
       quantified given the limits of detection for the methods of analysis and sample characteristics
       that may affect quantitation (e.g., dilution, concentration).

       Similar Samples: Samples from the same environmental medium that are identical or similar in
       every way (e.g., field collection procedure, analytical technique) except the degree to which they
       are affected by a site.

ESTABLISHING AN OBSERVED RELEASE  BY  DIRECT OBSERVATION

       An observed release by direct observation can be established in the air pathway by one of two
methods:

              A material containing  one or more hazardous substances is seen entering the
              atmosphere directly. Visually observing dust blow off a pile into the atmosphere during
              an SI is an example of an observed release by direct observation.  However, sampling
              from the dust's point of origin (e.g., the area on the pile from which the dust is released)
              should indicate that the dust contains  hazardous substances. Although not required,
              photographs are helpful in documenting an observed release by direct observation.

              If evidence supports an inference of a release to the  atmosphere, a demonstrated
              adverse effect may be used to establish an observed release. This approach for
              establishing an observed release by direct observation will be useful when visual
              evidence is not available. Visual evidence  is preferable for establishing an observed
              release, but may not be practical in cases where the  hazardous substance is an invisible
              gas or in cases where the  release of the hazardous substance can only be
Section 10.1                                    398

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              documented historically. For example, if available evidence demonstrates that two
              substances, which may react to form a poisonous gas, are present in an open surface
              impoundment, an adverse effect that would satisfy the criteria for an observed release
              would be an individual at the site overcome by fumes from the impoundment. Even if the
              fumes were invisible (and thus could not be "seen"), an observed release  by direct
              observation could be established based on demonstrated adverse effects  (e.g., a
              hospital report stating that a person was overcome by fumes containing a  hazardous
              substance). The emphasis of this example is the ability to support the inference of a
              release (i.e., that the two reactive chemicals are present) and the occurrence of the
              demonstrated adverse effect. There are other cases in which a scorer may infer that a
              release to the atmosphere probably has occurred but cannot score an observed release.
              For example, if a row of trees near the site is dead, it would usually not be possible to
              determine if the trees died from a hazardous substance in the atmosphere that was
              released from the site or from another, unrelated cause.

ESTABLISHING AN OBSERVED RELEASE BY CHEMICAL ANALYSIS

       An observed release by chemical analysis  in the air pathway is established based on analytical
data that indicate that hazardous substances have been detected in the air. Perform the following steps
for each detected hazardous substance.

(1)     Determine whether a detected hazardous substance can be attributed to sources at the
       site. Sampling results or records (e.g., manifests) indicating the presence of the hazardous
       substance in a source at the site are the strongest documentation. Information that the
       hazardous substance was used at the facility is also acceptable.

(2)     Determine the background level for the hazardous substance. Determining the appropriate
       background level requires analytical results from an appropriate  background sampling location
       (e.g., upwind from the site, outside a smoke plume) for substances that could be naturally
       occurring, ubiquitous, or attributable to other sources in the area. A background level of 0 can be
       assumed for hazardous substances that are not naturally occurring, not ubiquitous, and not
       attributable to other sources in the area (i.e., a background sample may not be needed).

(3)     Determine the appropriate quantitation limit for the hazardous substance.  If  available, the
       SQL should be used. If the SQL cannot be established and the sample analysis was performed
       under the EPA CLP, use the EPA CRQL in place of the SQL. If the SQL cannot be established
       and the sample analysis was not performed under the EPA CLP, use the DL (as defined in MRS
       section 1.1) in place of the SQL.

(4)     Compare the hazardous substance concentration at the sampling location (e.g.,
       downwind from the site, crosswind from the site) to the appropriate quantitation limit.  If
       the concentration of the hazardous substance at an appropriate sampling location is less than the
       quantitation limit, an observed release is not established at the sampling location. If other
       hazardous substances were detected at the sampling location, start again with Step (1). If the
       concentration is greater than or equal to the quantitation limit, continue to the next step.

(5)     Compare the hazardous substance concentration at the downwind or crosswind
       sampling location to the background level. If the background concentration is  not detected or
       is less than the DL (includes cases where the background level is 0), an observed release is
       established  if the sample measurement equals or exceeds the quantitation limit and at least
       some portion of this significant increase is  attributable to the site. If the background
       concentration is greater than or equal to the DL, the minimum requirements for establishing an
       observed release are:
                                            399                                    Section 10.1

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              The sample concentration should be greater than or equal to three times the background
              concentration; and

              At least some portion of this significant increase should be attributable to the site.

       See Section 5.1 fora discussion of significance above background.

       The ability to obtain reliable sampling data (i.e., from background and test samples) that
document an observed release is limited by the highly variable nature of the atmosphere and its effects
on emissions from a site. In recognition of the difficulties of atmospheric sampling, EPA has published
several relevant guidance documents. Highlight 10-1 presents guidance of particular interest.

       In reviewing sampling data for the air migration pathway, the scorer should determine whether
background samples and samples with significant concentration increases attributable to the site (e.g.,
downwind samples) can be considered similar. Meteorological monitoring (e.g., temperature, relative
humidity, precipitation, and especially wind speed and direction) should be conducted at the same time
and location as sampling so that non-site-related factors possibly influencing the samples can be
identified. The most important of these meteorological measurements are wind speed and direction,
which are crucial to an accurate sampling  regimen. In addition, the scorer should determine if all of the
following are true for background samples and samples with significant concentration increases
attributable to the site:

              Samples are taken at nearly the same time or during the same approximate time period;

              Samples are taken at approximately the same elevation relative to the suspected
              sources at the site; and

              Samples are collected and analyzed using equivalent methodologies.
                                     HIGHLIGHT 10-1
                      SELECTED EPA GUIDANCE ON AIR SAMPLING

 The documents listed below do not discuss the particular requirements ofthe MRS, but rather provide
 general information on atmospheric monitoring, sampling, and analysis. Theseare suggested sources
 of information; other documents also may provide appropriate guidance.

        Air/Superfund National Technical Guidance Study Series. Volume II - Estimation of Baseline Air
        Emissions at Superfund Sites (EPA-450/1-89-002a, August 1990).

        Air/Superfund National Technical Guidance Study Series. Volume IV - Procedures for Dispersion
        Modeling  and Air  Monitoring  for  Superfund  Air Pathway  Analysis  (Interim   Final)
        (EPA-450/1-89-004, July 1989).

        Compendium of Methods for the Determination of Toxic Organic Compounds in Ambient Air
        (EPA600/4-89-017, June 1988).

        Guidance on Applying the Data Quality Objectives Process for Ambient Air Monitoring Around
        Superfund Sites (Stage III) (EPA-450/4-90-005, March 1990).

        Technical Assistance Document for Sampling and Analysis of Toxic Organic Compounds in
        Ambient /A/r (EPA-600/4-83-027, June 1983).
Section 10.1                                     400

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TIPS AND REMINDERS

       Any accepted monitoring, sampling, and analysis methods that are equivalent to EPA standards
       may be used to establish an observed release. EPA has produced a number of guidance
       documents that may assist scorers in the selection of appropriate monitoring, sampling, and
       analysis methods (see Highlight 10-1 for a discussion of suggested guidance documents), but
       other methods may be appropriate.

       Sampling is  not restricted to the "breathing zone;" however, sampling elevation for background
       and contaminated samples should be similar. Often site-specific meteorological and
       topographical considerations will determine the appropriate  sampling elevation.

       Stationary ambient air monitors may be used to establish an observed release provided that the
       methods used  in monitoring, sampling, and analysis are equivalent to EPA standards.

       Data collected with real-time instruments (e.g., Organic Vapor Analyzers (OVA)), which provide
       instantaneous  results, may be used to identify locations for more accurate sampling, but in most
       cases should not be used to establish an observed release  by chemical analysis.

       Indoor air samples cannot be used to establish an observed release by chemical analysis.

       Stack analyses from operating facilities generally should not be used to establish an observed
       release.

       In some cases, wipe samples may be used to document historical releases to air, although it is
       often difficult to attribute contamination to the site based on  this type of data alone.

       Regional background levels  may be used on a case-by-case basis, when the regional
       background is  deemed to reflect conditions at the site. Site-specific atmospheric monitoring at
       the time of sample collection is always preferable for establishing background concentrations.

       The presence of an active fire is not considered to be evidence that a hazardous substance has
       been released to the air unless appropriate sampling has been conducted that confirms the
       release of a hazardous substance.
                                             401                                    Section 10.1

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SECTION 10.2
POTENTIAL  TO RELEASE
       This section provides guidance on evaluating selected features of the air pathway potential to
release factor. This section addresses the distinction between gaseous and particulate hazardous
substances, provides guidelines for combining sources with similar characteristics, and discusses
selected issues related to the gas and particulate containment factors. Flowcharts that summarize the
scoring steps for potential to release are presented at the end of this section.

       The potential to release factor in the air pathway is only scored if an observed release cannot be
established (see Chapter 5 and Section 10. 1 for guidance on establishing an observed release). If no
observed release to air can be established at the site, the potential to release factor value for the air
pathway is determined by separately evaluating the gas potential to release and the particulate potential
to release for each source at the site.

              The gas potential  to release value for a source is calculated by multiplying the gas
              containment factor value for the source by the sum of its gas source type factor value
              and its gas migration  potential factor value.

              The particulate potential to release value for a source is calculated by multiplying the
              particulate containment factor value for the source by the sum of its particulate source
              type factor value and  its  particulate migration potential factor value.

       In evaluating gas source type and particulate source type, consider only sources that meet the
minimum size requirement based on MRS Table 2-5 (i.e., those with a source  hazardous waste quantity
value of 0.5 or greater), unless there are no sources at the site that meet the minimum size requirement.
If there are no sources at the site that meet the minimum size requirement, assign each source at the
site a source type factor value from MRS Table 6-4.

       The highest gas potential  to release and the highest particulate potential to release values from
among all sources are selected. The higher of these two potential to release values is the potential to
release value for the air pathway.
                              RELEVANT MRS SECTIONS

        Section 6.1.2              Potential to release
        Section 6.1.2.1            Gas potential to release
        Section 6.1.2.2            Particulate potential to release
        Section 6.1.2.3            Calculation of potential to release factor value for the site
                                           403                                   Section 10.2

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DEFINITIONS

       Source: Any area where a hazardous substance has been deposited, stored, disposed, or
       placed, plus those soils that may have become contaminated from hazardous substance
       migration. In general, however, the volumes of air, ground water, surface water, and surface
       water sediments that may have become contaminated through migration are not considered
       sources.

DISTINGUISHING BETWEEN GASEOUS AND PARTICULATE HAZARDOUS
SUBSTANCES

       Before evaluating potential to release, determine whether each source has only gaseous, only
particulate, or both gaseous and particulate hazardous substances associated with it. Evaluate the
gaseous potential to release factor only for sources that have gaseous hazardous  substances. Similarly,
evaluate the particulate potential to release factor only for sources that have particulate hazardous
substances. Many sources will have both gaseous and particulate hazardous substances and potential to
release factors and should be evaluated for both.

              A hazardous substance is considered to be a gaseous hazardous substance whenever
              its vapor pressure (at or near 25°C) is greater than or equal to 1 &  torr (I torr = 1
              millimeter of mercury).

              A hazardous substance is considered to be a particulate  hazardous substance
              whenever its vapor pressure (at or near 25°C) is less than or equal to 1 d torr.

       Highlight 10-2 provides an illustration of the vapor pressure ranges for which hazardous
substances are considered gaseous and/or particulate. Note that in the mid-portion of the range,
hazardous substances are considered to be both gaseous and particulate for purposes of MRS scoring.

       Vapor pressure varies with temperature, so it is very important to be certain that the value given
is at or near 25°C. Data on vapor pressures at or near 25°C for many common hazardous substances
can be found in SCDM. Alternatively, vapor pressure data can be found in many common chemical data
references or can be calculated from available data on boiling pomt.Highlight 10-3 provides examples
of vapor pressures for several selected hazardous substances.  Values from information sources (e.g.,
chemistry reference books) other than SCDM may need to be adjusted to reflect vapor pressure at the
appropriate temperature. Units besides torr are frequently used for pressure and need to be converted
(e.g., 1 torr equals 1 mm Hg, I torr equals 1/760 of an atmosphere (atm)).

COMBINING SOURCES BEFORE CALCULATING POTENTIAL TO RELEASE

       The MRS states that when evaluating either gas potential to release or particulate potential to
release, the scorer can combine sources with similar characteristics Into a single source. It is most useful
to evaluate two sources with similar characteristics as a combined source if the combined source
exceeds the minimum size requirement, but the sources when evaluated separately do not exceed this
minimum. Scorers can also combine sources to lessen the complexity of a documentation record.

       For two sources to have similar characteristics in the gas (or particulate) potential to release
evaluation, they should meet all of the following guidelines:

              The same gas (or particulate) containment factor value
              The same gas (or particulate) source type
              Significantly overlapping hazardous substances.
Section 10.2                                   404

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                        HIGHLIGHT 10-2
   VAPOR PRESSURE RANGES FOR GASEOUS AND/OR PARTICULATE
                   HAZARDOUS SUBSTANCES
torr
       0
                     -9
         -6
-1
10     10     10     10     1
                               gas
                 paniculate
particulate only
gas and particulate
gas only
NOTE: Diagram not drawn to scale.

HIGHLIGHT 10-3
VAPOR PRESSURES FOR SELECTED HAZARDOUS SUBSTANCES3
Hazardous Substance
benzene
chlordane
chromium
1,2- dichlorobenzene
hexachloroethane
lead
methylene
terachloroethene
vinyl chloride
Vapor Pressure (torr)
9.5 x101
9.8 x10'6
0
1.5
2.1 x10-1
0
4.4 x102
1.9x101
3.0 x103
Evaluate Potential to
Release for
gas only
gas and particulate
particulate only
gas only
gas only
particulate only
gas only
gas only
gas only
a Vapor pressures In this table were obtained from SCDM; they are presented for illustrative purposes only. When
preparing MRS packages, the most current version of SCDM should be consulted.
L
                               405
                                                           Section 10.2

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       To combine sources, determine the containment factor value for each of the sources separately.
Hazardous substances present in either source may be used to calculate the gas (or particulate)
migration potential value. A single containment factor value is assigned as the containment factor value
for the combined source. Sources with gas and particulate hazardous substances should be scored
separately (i.e., their scores should not be combined) regardless of other similarities between the
sources.

EVALUATING GAS AND PARTICULATE CONTAINMENT

       In the air pathway, containment refers to the physical characteristics of a source that impede or
preclude the release of hazardous substances to the atmosphere. Containment in the air pathway is
evaluated using MRS Table 6-3 for gas containment and MRS Table 6-9 for particulate containment. The
evaluation is based on the presence of characteristics that match a description given in the applicable
table (Section 4.1 provides assistance in characterizing sources). The descriptions in both Tables 6-3
and 6-9 have a number of limitations placed on the types of sources that will match each description.
Some of these limitations are listed below:

               "Source covered with essentially impermeable, regularly inspected, maintained cover"
               includes only engineered containment structures (e.g., asphalt, concrete, or clay) that
               are in place  over the entire source and by their physical structure prevent migration of
               hazardous substances into the atmosphere.

               "Soils that are resistant to gas migration" include only moist fine-grained (e.g., silt loams
               and clays) and saturated  coarse-grained  (e.g., sands  and sandy loams) soils. For
               purposes of assigning gas or particulate containment  factor values, consider soils with
               USGS classifications of ML, CL, CH (fine-grained), orGC (coarse-grained) resistant to
               gas migration.

               "Particulate hazardous substances totally covered by  liquids" includes only hazardous
               substance particulates that are overlain by liquids (thereby preventing their migration).
               Particulates that are controlled by application  of a liquid to the land surface (e.g., dust
               control chemicals) would  not fall under this description unless the application of the liquid
               resulted in the particulate being totally covered.

       Several common features between the two containment evaluation tables (MRS Tables 6-3 and
6-9) should be noted.

               As in the other migration pathways, the maximum containment factor value is 10, with
               lower values indicating a greater degree of containment; a value of 0 indicates
               essentially complete containment.

               If the characteristics of a source do not match any of the descriptions, then a value of 10
               is assigned to the applicable containment factor. In other words, only those
               characteristics specifically described in Tables 6-3 and 6-9 constitute containment
               barriers sufficient to warrant assignment of a value other than 10.

               With the caveats noted below (i.e., biogas release, active fire), any source covered with
               an essentially impermeable, regularly inspected, maintained cover would be assigned a
               containment of 0 for both  gas  and particulate containment. It should be  noted, however,
               that some containment types may be "essentially impermeable" to particulates,  but
               permeable to gases. For this reason, this description may apply to a particulate release,
               but not to a gas release from the same source.

               As indicated in Highlight 10-4, many of the containment descriptions most likely to be
               encountered are assigned the same gas and particulate containment values.
Section 10.2                                    406

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                                     HIGHLIGHT 10-4
      SELECTED CONTAINMENT DESCRIPTIONS THAT ARE ASSIGNED THE
              SAME GAS AND PARTICULATE CONTAINMENT VALUES


     GAS/PARTICULATE CONTAINMENT DESCRIPTION                ASSIGNED VALUE IN BOTH
                                                                   MRS TABLES 6-3 AND 6-9
     Source substantially surrounded by engineered windbreak
     and no other containment specifically described in this table applies	 7
     Uncontaminated soil cover > 3 feet:
            Source substantially vegetated with little exposed soil	 0
            Source lightly vegetated with much exposed soil  	 3
            Source substantially devoid of vegetation	 7

     Uncontaminated soil cover > 1 foot and < 3 feet:
            Source heavily vegetated with essentially no exposed soil
            —     Cover soil type resistant to gas migration	 3
            —     Cover soil type not resistant to gas migration or unknown	 7
            Source substantially vegetated with little exposed soil and
            cover soil type resistant to gas migration	 7
            Other	  10

     Uncontaminated soil cover < 1 foot:
            Source heavily vegetated with essentially no exposed soil and
            cover soil type resistant to gas migration	 7
             Other  	  10

     Totally or partially enclosed within structurally intact building and
     no other containment specifically described in MRS Tables 6-3 and 6-9 applies	 7
               Several of the descriptions in both tables are only assigned if no other containment
               description applies (e.g., "source substantially surrounded by engineered windbreak").
               Values associated with these descriptions should only be assigned to the source if none
               of the other descriptions apply.

       The key to evaluating most of the containment descriptions in the air pathway is visual
observation of the surface characteristics of the source and, in the case of containerized wastes, the
condition of the containers. Important physical characteristics to note at each source include:

               The extent of vegetation on the entire source;

               The presence of windbreaks designed to impede air flow over the source;

               The condition of containers (e.g., whether they are intact and sealed); and

               In the case of particulate containment, the presence of liquids that act as a barrier
               between the particulate and the atmosphere.

       Each source should be evaluated as a single entity based on its source type. While several
containment types may apply to a given source, only the highest applicable containment value should be
assigned (i.e., assign only one containment value for each source). For example, if one  portion of a
source with greater than 3 feet of Uncontaminated cover matches one containment description (e.g.,
source substantially vegetated with little or no exposed soil) and  another portion of the same source
                                             407                                     Section 10.2

-------
matches another description (e.g., source substantially devoid of vegetation), a separate description that
describes the source as a whole should be  used instead and the corresponding value should be
assigned. In this case, neither 0 (source substantially vegetated with little or no exposed soil) nor 7
(source substantially devoid of vegetation) would be assigned.  Instead, the description "source lightly
vegetated with much exposed soil" would be used and its corresponding value of 3 would be assigned.

        There are two special situations in which the gas containment factor is not based on the type of
source containment present. If either of the descriptions  "evidence of biogas release" or "active fire within
source" applies, then a  gas containment value of 10 is assigned to the source. For example, consider a
landfill with a 4-foot uncontaminated soil cover that has grass growing-over the entire surface. Based on
these characteristics, a gas containment value of 0 would be assigned using the description
"uncontaminated soil cover > 3 feet: source substantially vegetated with little exposed soil."  However, if
evidence of a biogas release from the landfill was available, then a gas containment value of 10 would
be assigned. Similarly,  if an active fire is present within the landfill, a gas containment value of 10 would
be assigned.

        Determining whether evidence of a biogas (e.g.,  methane) release exists may involve site-
specific considerations  and require professional judgment. Evidence of biogas release can be based on
field measurements collected on or near a source. Several types of field measurements are commonly
used to document a biogas release, including:

               Direct reading colorimetric Indicator tube for methane

               Use of an OVA with a methane scrubber

               Use of both an OVA and a photoionization analyzer. If the OVA gets a hit and the
               photoionization analyzer does not, there is probably a methane release.

        In order to receive the 10-point value for biogas  release, the release should  be attributable to the
site and the supporting  documentation should verify that no other potential sources of biogas (e.g., a
nearby swamp) are present. Visual observations, such as physical evidence that an  explosion due to
biogas buildup has occurred, may also be acceptable documentation provided that the explosion
occurred because of the presence of biogas and not from the presence of other substances at the site.
For purposes of scoring the gas containment factor, the biogas released does  not have to be a
hazardous substance.

        Flowcharts that illustrate the methodology for evaluating the  gas potential to release factor and
the particulate potential to  release factor are presented \r\Highlights 10-5 and  70-6,  respectively.
Section 10.2                                     408

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                                                                                               HIGHLIGHT  1O-5
                          FLOWCHART FOR  POTENTIAL  TO  RELEASE:   PARTICULATE HAZARDOUS SUBSTANCES
                                                                                     START

                                                                   Source containing paflicL'talo hazardous substancefs}
                                                                     (vapor pressure less than or equal to 10-1 ton).
                   EVALUATE PARTICULATE CONTAINMENT (pC)
O
CD
                                   J   [
EVALUATE PARTICULATE SOURCE TYPE
                (pST)	
                                                                                                                                      EVALUATE PARTICULATE MIGRATION  POTENTIAL
    Based on a paniculate
containment description, use HRS
 Tabte 6-9 to assign a value for
 paniculate containment (or ttie
          source.

 Use the lowest value from HRS
  Tabte 6-9 thai applies to the
          source.
                                                                                  the source meet ma
                                                                              minimum size requirement
                                                                                (i.e., receive a source
                                                                              hazardous waste quantity
                                                                                value of 0.5 or morej?
                                               Are thora any other
                                              sources at the ste that
                                              meet BIB mWmum size
                                                  requirement?
                                                                                Assign the source a value
                                                                                lor paniculate source type
                                                                                  using HRS Tabte ^4.
                                                                                 Assign the scores a value
                                                                                    of 0 for partteulate
                                                                                       source type.
                                                                               Is the Bte located near
                                                                               the boundary points on
                                                                                  HRS Figure 6^7
 Calculate a Thomthwaite P-E
Index using the aquation found in
     HRS Section 6.122,3.

Based on the Thomthwaite P-E
   Index, assign a value tor
 paniculate migration potential
 using HRS Tabte 6-10. Assign
 this value to all sources a! the
            ste.
                                         CALCULATE PARTICULATE POTENTIAL TO
                                                     RELEASE VALUE
                                          For the source, sum the partfculatB source type
                                          factor value and participate migrator potential
                                            factor value and muWpfy this sum by the
                                              paniculate containment factor value
                                                     (pC(pST + pMP)].
                                                                                                                      Based on site location, assign a
                                                                                                                      value tor particulaia migration
                                                                                                                      potential using HRS Figure 6-2.
                                                                                                                      Assign 6m value to al sources
                                                                                                                              at the ste.
cf
a
o
3

p
k>
                     Evaluate (he next source using
                     the same process p.e., return to
                             START).
                Select the Nghest product calculated tor
                 the sources evaluated and assign it as
                the paniculate potential to release value
                           forthe site.

                              END.

-------
V
a
o
3

p
k>
                                                                  HIGHLIGHT  1O-6
FLOWCHART  FOR  POTENTIAL TO  RELEASE:   GASEOUS  HAZARDOUS  SUBSTANCES
                                                                                Soiree attaining gaseous hazardous
                                                                                substances) (vapor pressure greater
                                                                                   than or equal to 10 -' too).
                                                                                                                                                         EVALUATE GAS MIGRATION POTENTIAL (gMPj
                            EVALUATE GAS CONTAINMENT taC)
                                                                              EVALUATE GAS SOURCE  TYPE {gSTJ
                                                                                                                        For a gaseous hazardous substance associated w»h the
                                                                                                                       source, assign values from HRS Table 6-5 based on vapor
                                                                                                                          pressure and Henry's constant to each hazardous
                                                                                                                        substance.  (SpecifteJIy, assign a value based on vapor
                                                                                                                       pressure and a separate value based on Henry's constant
                                                                                                                         sucfi that two values are assigned to each hazardous
                                                                                                                                          substance.)
                                       there evidence of
                                       Wogas release?
                                                                                    Does the source meet the
                                                                                  rrWram size requirement (Le
                                                                                   receive a source hazardous
                                                                                  waste quantity value of 0.5 or
                                                                                            morel?
 Are there arrv other
  sowcss at
that meet the rrmmum
                                                                                                                                                          B Henry's constant eanrwt be determined for a hazardous
                                                                                                                                                          substance, assign that hazardous substance a value of 2
                                                                                                                                                                   for the Henrys constant component
                                    Is there an active tire
                                     wOTn the source'?
                                                                                                                                                            Sum the two values
                                                                                                                                                         assigned to •» hazardous
                                Based on a gas attainment
                              description, use HRS Table 6-3 to
                            assign a vate lor gas containment for
                                        the SOUKS,
                                 Based on this sun, assign
                                the hazardous substance a
                                  value for gas migration
                                 potential using HRS Table
                                          M.
 Are there a^ more
 gaseous hazardous
substances associated
   «Ah the source?
                                                  type using HRS Table
                            Use the lowest value from W5S Tat*
                                6-3 that applies to the source.
                                                                                                   Average the gas migration potential
                                                                                                     values assigned to the selected
                                                                                                         hazardous substances.
                                                                                                           Select the three
                                                                                                         hazardous substances
                                                                                                       thai hava the highest gas
                                                                                                       migration potanM values.
                                                  Are there more than
                                                three gaseous hazasfeus
                                                 substances associated
                                                    *Bh the source?
                                      CALCULATE GAS POTENTOU. TO RELEASE VALUE
                                                                                                   Based on this awre^ed value, assign
                                                                                                   the source a S£B migration potortiai
                                                                                                       value from HRS TaUe 6-7.
                                                                                                                                                                             Select afl of the
                                                                                                                                                                          hazardous substances
                                           For the source, sum the gas source type factor
                                           vaiue and gas mig.-at ton potential factor va'ue
                                           and muttlprf thfe sum by the gas containment
                                                        taC or value

*
Evaluate tf» next source using
the same process
(La, reiim to START).



Seteet *• Mshest product
catotMed forhe sourcac
ovatuatad and assign It as
the gas potential to
release value for the ste.
END.

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SECTION  10.3
ACTUAL CONTAMINATION
AND NEAREST  INDIVIDUAL
       This section provides guidance on establishing actual contamination in the air pathway. The
entire population within a target distance category in the air pathway is evaluated for actual
contamination when an observed release is established anywhere within that target distance category. In
addition, this section provides guidance on how to evaluate the nearest individual factor.
                               RELEVANT MRS SECTIONS

        Section 2.3                Likelihood of release
        Section 2.5                Targets
        Section 2.5.1               Determination of level of actual contamination at a sampling
                                 location
        Section 2.5.2               Comparison to benchmarks
        Section 6.3                Targets
        Section 6.3.1               Nearest Individual
        Section 6.3.2               Population
        Section 6.3.2.1             Level of contamination
        Section 6.3.2.2             Level I concentrations
        Section 6.3.2.3             Level II concentrations
DEFINITIONS
       Actual Contamination In the Air Migration Pathway: A target population is subject to actual
       contamination if a sample location within its distance category meets the criteria for an observed
       release. Targets located within distance categories closer to the source than the distance
       category where the observed release is established are also subject to actual contamination.

       Level I Concentrations for the Air Migration Pathway:  Level I concentrations are established
       for sampling locations at which the concentration of a hazardous substance that meets the
       criteria for an observed release is at or above its health-based benchmark. Targets also may be
       subject to Level I concentrations if multiple hazardous substances that meet the criteria for an
       observed release are present below their respective  benchmarks, and the I or J index is greater
       than or equal to one. Benchmarks for air include National Ambient Air Quality Standards
       (NAAQS),  National Emission Standard for Hazardous Air Pollutants (NESHAPs), screening
       concentrations for cancer, and screening concentrations for chronic effects.

       Level II Concentrations for the Air Migration Pathway: Level II concentrations are established
       for sampling locations where the concentration of at least one hazardous substance meets the
       criteria for an observed release, but the conditions for Level I concentrations are not met. In
       addition, Level II is assigned for observed releases established by direct observation.
                                          411                                  Section 10.3

-------
       Nearest Individual: Factor evaluated based on the presence of actual contamination or, for
       potential contamination, the shortest distance from any source at the site to any residence or
       regularly occupied building or area.

       Population for the Air Migration Pathway: Number of residents, students, and workers
       regularly present within the TDL. This population does not include transient populations, such as
       hotel and restaurant patrons, but may include seasonal populations (e.g., a resort area).

       Students: Full- or part-time attendees of an educational institution or day care facility located
       within the TDL.

       Target Distance Limit for the Air Migration Pathway:  Distance over which population and
       other targets are evaluated. The TDL generally is a 4-mile radius from the sources at the site.
       However, if a sampling point meeting the criteria for an observed release is located beyond the
       4-mile radius, that point defines the outer boundary of the TDL. For example, if an observed
       release is established 6 miles from the source, the TDL is 6 miles.

       Workers:  Permanent employees (part-time or full-time) of a facility or business that is located
       within the TDL.

DETERMINING LEVEL OF ACTUAL CONTAMINATION

       In order to evaluate level of actual contamination, an observed release should  first be
established (see Section 10.1 for establishing observed releases in the air pathway). If an observed
release to air is established in or beyond a distance category, actual contamination is also established for
that distance category and the level of contamination for the observed release location need to be
determined. The steps  below explain how to determine if a location is evaluated as Level I or Level II.

(1)     Determine whether an observed release can be established for any hazardous substance
       detected In air samples or based  on direct observation. See Section 10.1 for information on
       establishing an observed release.

              If an observed release is established only by direct observation, Level  I cannot be
              established and all locations for the direction observation are Level II. Continue with the
              guidance in the next subsection, Evaluating Sites with Actual Contamination.

              If an observed release is established based on chemical analysis, continue to Step (2).

              If no observed release can be established, evaluate the entire population within the 4-
              mile TDL for potential contamination.

(2)     For each sample location, compare the concentration of each hazardous substance that
       meets the observed release criteria to Its applicable benchmark(s). When comparing
       sampling  results to benchmarks, concentrations from longer collection times may be compared
       to shorter time-frame benchmarks, but concentrations from shorter collection times may not be
       compared to longer time-frame benchmarks. Sample concentrations tend to decrease as
       sampling time increases (e.g., 8-hour concentrations generally are lower than 3-hour
       concentrations). Applicable benchmarks (available in SCDM) for hazardous substances include:

              NAAQS;

              NESHAPs;

              Screening concentrations for cancer, which correspond to the 1 tf individual cancer risk
              for inhalation exposure; and

Section 10.3                                   412

-------
(3)
       Screening concentrations for noncancertoxicological responses, which correspond to the
       RfD for inhalation exposure.

If more than one benchmark applies to a substance, use the benchmark with the lowest
concentration. If no benchmark for the air pathway is available for a substance, that substance
cannot be used to establish Level I.

       If the  concentration of any one or more of the hazardous substances for which an
       observed release has been established is greater than or equal to its benchmark, score
       the sample location as Level I. Continue with the guidance in the next subsection.

       If only one hazardous substance meets the observed release criteria and its
       concentration is less than the lowest applicable benchmark, score the sample location as
       Level II. Continue with the guidance in the next subsection.

       If more than one hazardous  substance meets the observed release criteria and no single
       substance can be used to establish Level I, continue to Step (3).

Calculate the I and J indices for all hazardous substances for this sampling location that
meet the observed release criteria. Make two lists of substances that meet the observed
release criteria: hazardous substances with screening concentrations for cancer risk, and
hazardous substances with screening concentrations for noncancer effects. Each hazardous
substance may be on one, neither, or both lists. If more than one sample has been collected at a
location and these samples are comparable (e.g., taken in the same time frame, collected using
the same field techniques, analyzed by the same methods), for each hazardous substance select
the highest concentration to use in  the calculations below.

       Calculate the I index for all hazardous substances with screening concentrations for
       cancer risk that meet the observed release criteria, using the following equation:
                                            / =
       where: C,
              SC;


              n
                      concentration of substance i at the sample location;
                      screening concentration for cancer risk corresponding to a Id5 individual
                      cancer risk for inhalation exposure for hazardous substance i; and
                      number of hazardous substances that meet observed release criteria
                      and for which an SC is available.
              Calculate the J index for all hazardous substances with screening concentrations for
              noncancer effects that meet the observed release criteria, using the following equation:
       where:
              CRj

              m
                      concentration of substance j at the sample location;
                      screening concentration for noncancer effects corresponding to the
                      reference dose for inhalation exposure for hazardous substance j; and
                      number of hazardous substances that meet observed release criteria
                      and for which a CR is available.
                                             413
                                                                                    Section 10.3

-------
              If either the I or J index Is greater than or equal to 1, score the sample location as Level
              I. If both the I and J indices are less than 1, score the sample location as Level II.

EVALUATING SITES WITH ACTUAL CONTAMINATION

       The steps outlined below describe how to evaluate sample locations with actual contamination.

(1)     If only one source is being evaluated, skip to Step (2). If multiple sources are being
       evaluated:

              Determine the source to which the observed release is attributable. If this determination
              cannot be made, select a single source to which the hazardous substance could be
              attributable (see Highlight 10-7).

              When scoring potential contamination, aggregate identical distance categories that
              partially or totally overlap (see Highlight 10-8).

(2)     Determine the most distant sample location (observed release) that meets the criteria for
       Level I concentrations and the most distant location that meets the criteria for Level II
       concentrations. The most distant location meeting the criteria for Level II concentrations can be
       either a sample location (seeHighlight 10-9) or a direct observation location. If the most distant
       Level II location is closer to the source than the most distant Level I sample location, do not
       score any distance categories as Level II.

(3)     If a sample location (observed release) meets the criteria for Level I concentrations,
       determine the distance category Into which that sample location falls. That distance
       category and all distance categories closer to the source are scored as Level I concentrations. If
       the Level I sample location is beyond the 4-mile TDL, no distance categories would be scored as
       Level II and all populations and sensitive environments between the sample location and the
       source would be scored at Level I.

(4)     If the most distant observed release meets the criteria for Level II concentrations and is
       beyond the most distant sample location meeting the criteria for Level I concentrations,
       Level II concentrations should be scored. The distance category containing the most distant
       Level II location and all distance categories between that distance category and the most distant
       category containing a Level I sampling location should be scored at Level II (seeHighlight
       10-10). If no distance category contains  a Level  I sampling location, then the distance category
       containing the Level II location and all distance categories closer to the source are  scored as
       Level II.

(5)     Score all distance categories not scored as Level I or Level II as potential contamination.
       Note that if the most distant Level I or Level II sampling location is beyond the 4-mile TDL, all
       distance categories should be scored as Level I or Level II; therefore, potential contamination
       would not be scored.
Section 10.3                                    414

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                                   HIGHLIGHT 10-7
  DETERMINING AREAS OF ACTUAL AND POTENTIAL CONTAMINATION
                             WITH MULTIPLE SOURCES
           L 1 = Level I sample location

           L 2 = Level II sample location

           P  = Sample location subject to potential contamination

           fH = Scored at Level I

           £3 = Scored at Level II

Actual Contamination

(1)      Determine the source to which the observed release is attributable.

(2)      If this  determination  cannot be made, select a single source (S1 in this example) to which the
        observed release could be attributable.

(3)      Draw distance categories around the source selected in Step (1) or (2).

        •       Targets within the outermost distance category containing a Level I sample location (>1/4
               to 1/2 in this example) and targets within all distance categories closer to the source (>0 to
               1/4 in this example) are subject to Level I  contamination.

        •       Targets within any distance category containing a Level II location that is beyond the
               outermost distance category containing a Level I sample location (i.e.,  >1/2 to 1 in this
               example)  are  scored at Level II.  If there were distance categories  between the  one
               containing the Level II location and the Level I distance category most distant from the
               source, targets within those distance categories would also be scored at Level II.

                                  (continued on next page)
                                             415
                                                                                       Section 10.3

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                              HIGHLIGHT 10-7 (continued)
      DETERMINING AREAS OF ACTUAL AND POTENTIAL CONTAMINATION
                               WITH  MULTIPLE SOURCES

 Potential Contamination

 (1)     Targets should be assessed for potential contamination based on the nearest source. To determine the
        nearest source, draw distance categories around the remaining sources (§and S3 in this example). All
        distance categories outside the area of actual contamination (established above) and within the 4-mile
        TDL are subject to potential contamination.

 (2)     Aggregate distance categories that are subject to potential contamination for all sources where identical
        distance categories would overlap.

                For S2 and S3, the first distance category to be aggregated is the >1/4 to 1/2.

                The first distance category  to be aggregated for all sources is the > 1 to 2.

 (3)     Score targets subject to potential contamination based upon the distance category into which they fall.
EVALUATING NEAREST INDIVIDUAL FACTOR

       In evaluating the nearest individual factor, consider all residences, regularly occupied buildings,
and areas that are within a 1-mile radius of the site.

(1)     Determine whether any residences or regularly occupied buildings or areas are subject to
       Level I or Level II concentrations. If not, continue to Step (2). If so, score the nearest
       individual as follows:

              If one or more residences or regularly occupied buildings or areas is subject to Level I
              concentrations, assign a factor value of 50.

              If one or more residences or regularly occupied buildings or areas is subject to Level II
              concentrations, but none is subject to Level I concentrations, assign a factor value of 45.

(2)     Determine the shortest distance to any residence or regularly occupied building or area,
       as measured from any source at the site with an air migration containment factor value
       greater than 0. Based on this shortest distance, use MRS Table  6-16 to assign a value to the
       nearest individual factor. Note that the distance categories used  for evaluating the nearest
       individual factor differ slightly from the categories  used for distance-weighted population values
       in MRS Table 6-17 (e.g.,  the 0 and  >0 to 1/4 mile category are replaced by the 0 to 1/8 and the
       >1/8 to 1/4 mile categories).
Section 10.3                                    416

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                           HIGHLIGHT 10-8
          DETERMINING POTENTIAL CONTAMINATION
                     WITH MULTIPLE SOURCES
Draw distance categories around each  individual source and then determine aggregate distance
categories (i.e., combined categories reflecting overlap of identical distance categories for multiple
sources).

Count each individual only once (however, do not expend extra resources to determine if a resident
is also being evaluated as a student or worker) and  sum the populations subject to potential
contamination for each distance category (e.g., all those individuals located between 1 to 2 miles at
each source are added together).

Determine the  nearest individual as the  single individual located nearest to any source.  Distance
categories for assigning a value to the nearest individual factor replace the on-source (0)  and >0 to
1/4 category (shown in the diagram) with 0 to 1/8 and >1/8 to 1/4 mile distance categories.
                                     417
                                                                              Section 10.3

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                                   HIGHLIGHT 10-9
           EFFECT OF SAMPLE LOCATION ON TARGET POPULATION
                  • - Sample location
                  0- Target population subject to actual contamination

  These figures indicate that by placing a sampler (or making a direct observation for Level II) just beyond a
  distance category boundary versus just inside a distance category boundary, a population over a greater area
  can be evaluated as subject to actual contamination.
Section 10.3
                                           418

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                             HIGHLIGHT 10-10
    ILLUSTRATION OF TARGET POPULATIONS SUBJECT TO LEVEL I,
               LEVEL II, AND POTENTIAL CONTAMINATION
         L i = Level I sample location
         L 2 = Level II sample location
              Level I target population
              Level II target population
              Targets population subject to potential contamination
Distance categories for assigning a value to the nearest individual factor replace the 0 and >0 to 1/4 category
(shown in the diagram) with 0 to 1/8 and >1/8 to 1/4 mile distance categories.
                                     419
                                                                         Section 10.3

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TIPS AND REMINDERS

       The basic approach for scoring actual contamination in the air pathway is to set up distance
       categories around the sources and assign each distance category to Level I, Level II, or potential
       contamination, depending upon the location of observed releases and the results of comparisons
       of sample concentrations to benchmarks. Note that an observed release detected just off a
       source can result in the entire population within the greater than 0-1/4 mile distance category
       being evaluated as Level I or Level II.

       Any resident, student, or worker located anywhere within the distance  category in which the
       observed release is located is evaluated as subject to actual contamination. In addition, any
       resident, student, or worker located in distance categories closer to the source is also evaluated
       as subject to actual contamination.

       The TDL for the air pathway is 4 miles from the edge of a source, unless  an observed release is
       established beyond 4 miles.

       For the nearest individual factor, note that the distance category nearest the source is >0 to 1/8
       mile, not >0 to 1/4 mile as it is for the population factor.

       The distance-weighted population value drops sharply farther from the site. Hence, it is most
       important that the population close to sources be documented carefully.
Section 10.3                                    420

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SECTION  10.4
RESOURCES
       This section provides guidance for scoring the resources factor in the air pathway. The resources
factor evaluates potential damage to recreation areas, commercial agriculture, and commercial
silviculture due to site-related atmospheric contaminants. It does not evaluate threats to human health or
sensitive environments.
                             RELEVANT MRS SECTIONS
        Section 6.3           Targets
        Section 6.3.3         Resources
DEFINITIONS

       Commercial Agriculture: Production of crops for sale, including crops intended for widespread
       distribution (e.g., supermarkets) and more limited distribution (e.g., local produce stands), and
       any nonfood crops such as cotton and tobacco. Commercial agriculture does not include
       livestock production, livestock grazing, or crops grown for household consumption (e.g.,
       backyard garden or fruit trees).

       Commercial Silviculture: Cultivation of trees for sale (e.g., Christmas tree farm, trees raised for
       lumber).

       Major or Designated Recreation Area: A major recreation area is an area used  by a large
       number of people for recreational purposes (e.g., swimming or baseball). A designated
       recreation area is an area designated and maintained by a government body (e.g. local, state,
       Federal) as an area for public recreation.

SCORING THE RESOURCES  FACTOR

(1)     Using the checklist In Highlight 10-11, determine if there are any commercial agricultural
       or silvicultural areas, or major or designated recreation areas within 1/2 mile of a source
       at the site. Use the above definitions in making this determination. Highlight 10-12 lists
       examples of data sources for the resources factor.

(2)     If any of these areas are present within 1/2 mile of a source with an air migration
       containment factor value greater than 0, assign a resource factor value of 5. If none of
       these areas  is  present within 1/2 mile of a source, or if the source has an air migration
       containment factor of 0,  assign a resource factor value of 0.
                                           421                                   Section 10.4

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                                   HIGHTLIGHT 10-11

                       CHECKLIST FOR RESOURCES FACTOR

    For the site being evaluated:

    (1)     Is commercial agriculture present within 1/2            Yes     No
           mile of a source at the site?

    (2)     Is commercial silviculture present within 1/2            Yes     No
           mile of a source at the site?

    (3)     Is there a major or designated recreation area          Yes     No
           within 1/2 mile of a source at the site?

    If the answer is "yes" for any of the questions above, assign a resources factor value of 5. If the answer is
    "no" for each question, assign a resources factor value of 0. Remember that the answer is "yes" only if the
    activity takes place within 1/2 mile of a source with an air migration containment factor value greater than 0.
                                    HIGHLIGHT 10-12
                  DATA SOURCES FOR THE RESOURCES FACTOR

   The following sources of information may help in documenting resource use at the site.

          Agricultural extension agents
          Correspondence with nearby businesses
          Correspondence with other nearby institutions, such as farms or universities
          County land use maps
          Existing PA/SI reports
          Field observations
          Files from adjacent or nearby CERCLIS sites
          Local Chambers of Commerce
          Soil Conservation Service (SCS)
          State departments of natural resources or state environmental departments, especially
          forestry departments
          The USDA/U.S. Forest Service (USFS)
          Topographic maps
TIPS AND REMINDERS

       Only 5 target points are assigned for the resources factor, regardless of the number of resources
       present within 1/2 mile of the site. Do not expend significant efforts documenting resource use
       unless those 5 points  may be critical to the site score.

       Resources are only evaluated within 1/2 mile of sources at the site. Resources documented for
       other pathways may not be close enough to the site to score in the air migration pathway.
Section 10.4                                    422

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SECTION 10.5
EVALUATION OF
SENSITIVE
ENVIRONMENTS
       This section provides general guidance for evaluating sensitive environments for the air
migration pathway as well as specific guidance and examples for evaluating more complex situations in
which multiple sensitive environments overlap. Assigning point values to sensitive environments is
straightforward in most cases. In other cases (e.g., when the boundaries of several sensitive
environments overlap, or if more than one designation may apply to a single environment), this
determination may be  less obvious; however, most scoring difficulties can be eliminated by treating each
sensitive environment as a separate, independent target. This section addresses only the
pathway-specific information necessary to evaluate sensitive environments (including wetlands) in the air
pathway. Specific definitions of sensitive environments, sources of information, and steps for identifying
sensitive environments are provided in Appendix A.
        Section 6.3
        Section 6.3.4
        Section 6.3.4.1
        Section 6.3.4.2
        Section 6.3.4.3
RELEVANT MRS SECTIONS

 Targets
 Sensitive environments
 Actual contamination
 Potential contamination
 Calculation of sensitive environments factor value
DEFINITIONS

       Actual Contamination for Listed Sensitive Environments: A listed sensitive environment is
       considered subject to actual contamination if any portion of the sensitive environment falls within
       a distance category where an observed release has been established, or in any distance
       category closer to the site. Direct observation and/or analytical data from air sampling may be
       used to establish actual contamination.

       Sensitive Environment In the Air Pathway: A sensitive environment is a wetland (as defined in
       40 CFR 230.3) or any area that meets the criteria listed in MRS Table 4-23. No other areas are
       considered sensitive environments for the air migration pathway.

CALCULATING THE  SENSITIVE  ENVIRONMENTS FACTOR VALUE

       The following steps describe how to  calculate the sensitive environments factor value.

(1)     Identify all sensitive environments listed In MRS Table 4-23 within the TDL. For each
       sensitive environment, assign the appropriate point value from MRS Table 4-23. For guidance in
       identifying sensitive environments, see Appendix A.  Use the following guidelines in identifying
       and assigning point values to each sensitive environment.
                                         423
                                                                              Section 10.5

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               Treat each discrete physical area that can be designated as a sensitive environment as
               a separate environmental target for MRS scoring purposes, regardless of the degree to
               which it overlaps with other sensitive environments. For example, critical habitat for an
               endangered species has the same point value whether located in a state wildlife refuge
               or not. The state wildlife refuge would be evaluated as a separate sensitive environment
               (see Highlight 10-13).

               Treat "critical habitat for" or "habitat known to be used by" endangered or threatened
               species as follows.

               —      Identify at least one distinct habitat for each individual species (e.g., if there are
                      three different species, identify three or more habitats, even if they partially or
                      completely overlap).

               —      For each individual species, assign only the endangered or threatened category
                      that results  in the highest point value. For example, if the same species is both a
                      Federal proposed threatened species (75 points), and a state designated
                      endangered species (50  points), evaluate the species as a Federal proposed
                      threatened species for MRS scoring purposes.

               —      If both "critical habitat for" and "habitat known to be used by" the same species
                      occur within the TDL, consider each a separate  sensitive environment for MRS
                      scoring purposes. However, if these areas overlap within the TDL, evaluate the
                      overlapping area only as "critical habitat for" the species (i.e., do not consider
                      the zone of overlap as both critical habitat for"  and "habitat known to be used
                      by" the species).

(2)     Based on the most distant location establishing an observed release to air, determine
       which listed sensitive environments are subject to actual contamination.

               If multiple sources are present, determine to which source the observed release is
               attributable. If this determination  cannot be made, select a single source to which the
               hazardous substance could  be attributable (see Highlight 10-7 for guidance on drawing
               distance categories at sites with multiple sources).

               If this location is within the 4-mile TDL, use MRS Table 6-15 to identify the distance
               category in which the observed release is located. Consider that distance category and
               all distance categories closer to the source as subject to actual contamination; all other
               distance categories (i.e., those farther from the source than the distance category in
               which the observed release is  located) should be considered  subject to potential
               contamination.  Note that because no appropriate benchmarks exist, no distinction is
               made between  Level I and Level  II contamination when scoring sensitive environments
               in the air migration pathway. Sensitive environments within the TDL are evaluated
               simply as subject to either actual or potential contamination (i.e., actual contamination is
               not divided into Level I and Level II).

               If this location is beyond the 4-mile TDL, draw the boundary of a distance category
               extending to that location. Any sensitive environments located partially or entirely within
               that distance category or a distance category closer to the source are considered subject
               to actual contamination. In such a case, no sensitive environments are considered
               subject to potential contamination (see Highlights 10-14 and  10-15).
Section 10.5                                     424

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                                    HIGHLIGHT 10-13
       IDENTIFYING SENSITIVE ENVIRONMENTS IN THE AIR PATHWAY
              TDL
                                    State Wildlife
                                  -.. ^ Refuge   \.,
The above figure is a schematic map (not to scale) of the 4-mile TDL associated with a hypothetical site.  From
background documents and discussions with appropriate Federal and state agencies, the following information
is available:

The area labelled Critical Habitat (Y) is a critical habitat for Federal  endangered species. The area labelled
Critical Habitat (X) is a critical habitat for a different Federal endangered species.  The outlined area at the
bottom of the map, directly beneath the source, is a state wildlife refuge. The areas designated as Wetland
1 and Wetland 2 are wetlands as defined in 40 CFR 230.3.

Based on this information, and by referring to HRS Tables 4-23 and 6-18 of the HRS Rule, the following
sensitive environments are identified:

(1)      The area labelled Critical Habitat (Y) is identified as a critical habitat for Federal endangered species
        (Y) and assigned a value of 100 points;

(2)      The area labelled Critical Habitat (X) is identified as a critical habitat for Federal endangered species
        (X) and assigned a value of 100 points;

(3)      The state wildlife refuge is assigned a value of 75 points;

(4)      The area designated as Wetland 1 and the area designated as Wetland 2 are assigned a point value
        based on total acreage within the TDL (see Highlight 10-15).
                                              425
                                                                                          Section 10.5

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                                     HIGHLIGHT 10-14
            DETERMINING ACTUAL AND POTENTIAL CONTAMINATION
                           FOR SENSITIVE ENVIRONMENTS
   If an observed release location falls within a distance category less than 4 miles from the nearest edge of the
   source, the distance category that contains the observed release and all distance categories that are closer
   to the site are considered subject to actual contamination.
                       iv w i m Actual contamination
                            = Observed release
                              Actual contamination
                              Observed release
   For sensitive environments in the air pathway, there are no established benchmarks and, therefore, there is no
   distinction between areas of Level I  and Level II contamination.
   If an observed release location is more than 4 miles from the nearest edge of the source, the entire area
   between the source and a distance ring established by the radii extending to the location of the observed
   release is considered subject to actual contamination. In such cases, no distance categories are considered
   subject to potential contamination.
Section 10.5
                                              426

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                                  HIGHLIGHT 10-15
            SCORING EXAMPLE FOR SENSITIVE ENVIRONMENTS
                                                         Critical Habitat for
                                                         Fed. Endangered
            1 mile distance category

            2 mile distance category

            3 mile distance category

            4 mile distance category (TDL)
At this site, the area of actual contamination has been determined, the assigned value for likelihood of release
(LR) is 550, and the assigned value for waste characteristics (WC) is 56.  Five sensitive environments were
identified and delineated as shown.  Portion (a) of Wetland 1 (i.e., portion within >3 to 4 miles of the source)
was determined to be 43 acres.  Portions (a), (b), and (c) of Wetland 2 were determined to be 13 acres, 34
acres, and 60 acres, respectively.  The sensitive environments factor value was obtained using the steps
outlined below.

                                  (continued on next page)

                                             427
                                                                                       Section 10.5

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                               HIGHLIGHT 10-15 (continued)
                SCORING EXAMPLE FOR SENSITIVE ENVIRONMENTS

    (1)   Critical habitats (X) and (Y) are considered subject to actual contamination because they are each partially
         within the area of actual contamination (identified with diagonal lines). The combined value for these two
         environments is 200. Portion (a) of Wetland 2 is subject to  actual contamination and  is assigned a
         wetland rating value of 25. These two values are added (200 +  25  = 225) to  calculate the actual
         contamination value.

    (2)   The state wildlife refuge, portion (a) of wetland 1, and portions (b) and (c) of wetland 2 are outside the area
         of  actual  contamination,  but  within  the TDL,  and therefore,  are considered  subject to  potential
         contamination. The state wildlife refuge, at a distance of >2 to 3 miles, is assigned a value of 75 and a
         distance weight of 0.0023. Portion (b) of Wetland 2 is also assigned a distance weight of 0.0023 and a
         wetlands rating value of 25. The 43 acres in Portion (a) of Wetland 1 and the 60 acres in Portion (c) of
         Wetland 2 are summed (43 + 60 = 103 acres), and this total acreage is assigned a wetlands rating value
         of 125. Portion (a) of Wetland 1 and  Portion (c) of Wetland 2 are also assigned a distance weight of
         0.0014 because they are within the >3 to 4-mile distance category. The sensitive environment rating
         values for each distance category are summed and then multiplied by the distance weight for that distance
         category. All of these values are summed, such that [(0.0023)(75 + 25) + (0.0014) (125) = 0.41]. This
         value divided by 10 (i.e., 0.041) is the potential contamination value. This figure is not rounded because
         it is less than one.

    (3)   The total  targets value  for sensitive  environments (EB) was  determined  by  summing the actual
         contamination value and the potential contamination value [225 + 0.041 = 225.041].

    (4)   The sensitive environments factor value was determined as follows:

         •  The values for LR, WC, and EB were multiplied together and then divided by 82,500 to obtain the score
           (S)of 84.015.

         •  Because 84.015 is greater than 60, it was necessary to calculate the value EC = 160.71, which was
           obtained by dividing 4,950,000 by (LR x WC).

         •  The sensitive environments factor was assigned a value of 160.71 (i.e., EC).
               —      Note that if any portion of a sensitive environment listed in MRS Table 4-23 is
                       subject to actual contamination, the entire sensitive environment is scored as
                       subject to actual contamination.

               Sum all of the sensitive environments values (from MRS Table 4-23) for sensitive
               environments subject to actual contamination. Do not distance weight these values.
               Assign this total as the  actual contamination value for listed sensitive environments not
               being evaluated solely as wetlands.

(3)      Determine which listed sensitive environments are subject to potential contamination.

               If the distance category containing the most distant observed release to air is closer than
               the 4-mile TDL,  any listed sensitive environments entirely beyond that distance category,
               but at least partially within the TDL, are considered subject to potential contamination.
               Note that if a sensitive environment is subject to actual contamination, it cannot also  be
               considered subject to potential contamination. If no observed release to air is
               established, all sensitive environments at least partially within the 4- mile TDL would be
               considered subject to potential contamination.
Section 10.5                                      428

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              Determine the distance category that each listed sensitive environment subject to
              potential contamination falls within. If a listed sensitive environment falls into more than
              one distance category, assign only the highest applicable distance weight (i.e., count it
              only once and use the closest distance category).

              Sum the assigned values for all of the listed  sensitive environments that fall within a
              single distance category and multiply that total by the appropriate distance weight.
              Remember to count each listed sensitive environment only once in the closest distance
              category. Sum all of these distance weighted values and assign this total as the potential
              contamination value for listed sensitive environments not being evaluated solely as
              wetlands.

              When scoring potential contamination, aggregate identical distance categories that
              partially or totally overlap (see Highlight 10-8 for guidance on drawing distance
              categories at sites with multiple sources).

(4)     If wetlands are present within the TDL, determine which portions of the wetlands are
       subject to actual contamination and which portions are subject to potential
       contamination.

              Only the portion of each discrete wetland area that is within the distance category
              established  by the most distant observed release location (or a distance category closer
              to the sources) should be considered subject to actual contamination.

              Wetlands or portions of wetlands farther from the source than the distance category
              containing the most distant observed release location, but within the 4-mile TDL, should
              be considered subject to potential contamination.

(5)     Determine the total acreage of wetlands subject to actual contamination and the total
       acreage of wetlands subject to potential contamination. There are a number of relatively
       simple quantitative methods for estimating the acreage of a given area. These include:

              Using a digitizing tablet;

              Using graph paper as an overlay for a map with an accurate scale (e.g., a USGS
              topographic map); or

              Cutting  out a standard (e.g., a 10-acre square of the map) and comparing the mass of
              the standard against the mass of the clippings from the portion of the map for which the
              acreage is to be determined. This can be done using a standard laboratory balance
              scale.

(6)     Assign the appropriate wetland rating value using MRS Table 6-18 based on the total
       acreage of wetlands subject to actual contamination. Assign this value as the actual
       contamination value for wetlands.

(7)     Identify the distance categories (listed in MRS Table 6-15) that  include portions of
       wetlands subject to potential contamination. Based on total acreage of all wetlands within a
       particular distance category, assign the appropriate wetland rating  value for the portions of
       wetlands subject to potential contamination. For example, if 10 acres of a 100-acre wetland are
       within a particular distance category, only those 10  acres should be evaluated for that particular
       distance category.

              Sum the total acreage of wetlands or portions of wetlands present within a single
              distance category.

                                              429                                     Section 10.5

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               Assign a single wetlands rating value to that distance category based on the total
               acreage of all wetlands within that distance category.

               Multiply the sum of the wetlands rating values for a single distance category by the
               distance weight for that distance category. Distance weights are provided in MRS Table
               6-15.

       Repeat the above procedure for each distance category subject to potential contamination (i.e.,
       those within the TDL not subject to actual contamination).

       Sum the potential contamination values calculated for each distance category and assign this
       value as the potential contamination value for wetlands.

(8)     Calculate the actual contamination factor value and the potential contamination factor
       values.

               Sum the assigned actual contamination values for listed sensitive environments and for
               wetlands. Assign this value as the actual contamination factor value.

               Sum the assigned potential contamination values for listed sensitive environments and
               for wetlands. Divide that value by ten. If this value is less than 1, do not round it to the
               nearest integer. If this value is greater than 1, round  it to the nearest integer. Assign this
               value as the potential contamination factor value.

(9)     Calculate the total value for sensitive environments. Sum the factor values for actual
       contamination and potential contamination. Assign this value as the sensitive environments total
       value (EB).

(10)    Calculate the sensitive environments factor value. Because the air migration pathway score
       based solely on sensitive environments is limited to 60 points, the method for determining the
       sensitive environments factor value depends on the total value for sensitive environments  (EB,
       as calculated in Step (9) above), the likelihood of release value for the air pathway (LR), and the
       waste characteristics value (WC).

               Multiply the values assigned to LR, WC, and EB for the site and divide this  product by
               82,500.

               If the resulting score (S) is 60 or less, assign EB as the sensitive environments factor
               value.

               If the resulting score (S) is greater than 60, assign only that portion of EB that will result
               in a score of 60 as the sensitive environments factor value. This value, termed EC, is
               calculated as follows:


                                  EC   (60)(82,500)    4,950,000
                                                    "
       Note: Do not round EC to the nearest integer.
Section 10.5                                     430

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TIPS AND REMINDERS

       Only wetlands (as defined in 40 CFR 230.3) and areas that are listed in MRS Table 4-23 are
       considered sensitive environments in the air pathway.

       Treat each discrete sensitive environment as a separate, independent target for assigning point
       values and determining level of contamination, regardless of the degree to which its boundaries
       overlap with those of other sensitive environments.

       Identify at least one  separate sensitive environment for each endangered or threatened species,
       but assign only one  category (e.g., Federal endangered or state threatened, but not both) to each
       species.

       Designations of threatened or endangered species listed at the state level are valid only within
       the borders of that state.

       Wetland areas can be evaluated both  as a wetland and as other types of sensitive
       environments (e.g., critical habitat).

       If any portion of a listed sensitive environment is subject to actual contamination, the entire
       sensitive environment is considered subject to actual contamination. Note that this is not true
       for wetlands.

       Wetland acreage estimates  must be based on the portion  of each wetland area within each
       distance category (e.g., only the portion of a wetland within a distance category subject to actual
       contamination is evaluated under actual contamination).

       In evaluating wetlands for potential contamination, evaluate  all wetlands in a single distance
       category as a distinct sensitive environment.

       There is no limit to the air pathway targets factor category score; however, the air pathway score
       based solely on sensitive environments is subject to a maximum of 60 points.
                                             431                                     Section 10.5

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APPENDIX A
SENSITIVE ENVIRONMENTS

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                               CONTENTS OF APPENDIX A

                                                                                   Page

APPENDIX A   SENSITIVE ENVIRONMENTS

Section A.1 Pathway-specific Eligibility Reguirements for Sensitive Environments	A-1

       Air Pathway 	A-1
       Soil Exposure Pathway	A-1
       Surface Water Pathway	A-1

Section A.2 Definitions of Sensitive Environments Including Wetlands  	A-3

Section A.3 Process for Identifying and Delineating Sensitive Environments	A-25

       Sensitive Environments Likely to Be Delineated on USGS Topographic Maps	A-25
       Sensitive Environments Likely to Be Delineated on Specialized Maps or
          in Special Documents	A-25
       Sensitive Environments That Require Professional Judgment and/or Specific
          Expertise to Identify and Delineate.	A-26

Section A.4 Sources of Information for Identifying Sensitive Environments	A-33
                                           A-i                           Contents of Appendix A

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                                HIGHLIGHTS IN APPENDIX A

Highlight A-1   Eligibility Requirements for Evaluating Terrestrial
              Sensitive Environments in Surface Water Pathway	A-2

Highlight A-2   Key Terms Used in Defining Sensitive Environments	A-3

Highlight A-3   Determining  HRS Categories for Coastal Barrier	A-6

Highlight A-4   HRS Categories for Wild and Scenic Rivers.	A-8

Highlight A-5   CERCLA Natural Resource Trustees	A-12

Highlight A-6   Appropriate Documentation for Migratory Pathways and
              Feeding Areas Critical for Maintenance of Anadromous Fish
              Species Within Rivers, Lakes, or Coastal Tidal Waters	A-13

Highlight A-7   Appropriate Documentation for Spawning Areas Critical
              for Maintenance of Fish/Shellfish Species Within Rivers,
              Lakes, or Coastal Tidal Waters	A-17

Highlight A-8   Comparison  of HRS Wetlands Definition and Wetlands
              Classification System Used for NWI Maps	A-22

Highlight A-9   Eligibility of Wetland Categories on NWI Maps for HRS Scoring	A-30

Highlight A-10   U.S. Geological  Survey Earth Science Information Center Offices.	A-43

Highlight A-11   U.S. National Park Service Regional Offices	A-44

Highlight A-12   U.S. Fish and Wildlife Service Regional Offices	A-45

Highlight A-13   U.S. Bureau of Land Management State Offices	A-46

Highlight A-14   U.S. National Forest Service Regions	A-47

Highlight A-15   National Estuarine Research Reserve System	A-48

Highlight A-16   Near Coastal Waters Program EPA Regional  Contacts	A-50

Highlight A-17   EPA Regional Clean Lakes Program Offices	A-51

Highlight A-18   Nautical Chart Numbers for Marine Sanctuaries	A-52

Highlight A-19   National Estuary Program Information Sources	A-53

Highlight A-20   EPA Regional Offices	A-54

Highlight A-21   National Park Service Regional Boundaries	A-55

Highlight A-22   U.S. Fish and Wildlife Service Regional Boundaries	A-56

Highlight A-23   U.S. Forest  Service Regional Boundaries	A-57
                                                                           Highlights in Appendix A

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                               ACRONYMS IN APPENDIX A
BIA          Bureau of Indian Affairs
BLM         Bureau of Land Management
BTAG        Biological Technical Assistance Group
CFR         Code of Federal Regulations
EIS          environmental impact statement
MRS         Hazard Ranking System
MMS         Minerals Management Service
NMFS        National Marine Fisheries Service
NOAA        National Oceanic and Atmospheric Administration
NPS         National Park Service
NWI         National Wetlands Inventory
OSM         Office of Surface Mining
OWRS       Office of Water Regulations and Standards
SAV         submerged  aquatic vegetation
SCS         Soil Conservation Service
TDL         target distance limit
USC         U. S. Code
USFS        U. S. Forest Service
USFWS      U. S. Fish and Wildlife Service
USGS        U. S. Geological Survey
                                          A-v
                                                                       Acronyms in Appendix A

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SECTION A.1
PATHWAY-SPECIFIC
ELIGIBILITY
REQUIREMENTS  FOR
SENSITIVE  ENVIRONMENTS
       The Hazard Ranking System (MRS) evaluates environmental threat only for a specified set of
targets (i.e., sensitive environments) that meet certain criteria. With some pathway-specific exceptions,
sensitive environments located partially or wholly within the target distance limit (TDL) for the surface
water, soil exposure, and/or air pathway(s) are eligible targets. Two key steps to evaluate an area as a
sensitive environment in the MRS are  (1) determine if the area meets MRS criteria for one or more
sensitive environments, and (2) delineate boundaries of the area eligible for scoring with respect to the
pathway being evaluated. Sensitive environments include:

             Those defined and delineated by statute (e.g., National Parks, Designated Federal
             Wilderness Areas);

             Those that meet  a particular classification (e.g., spawning areas critical for the
             maintenance offish/shellfish species, habitat known to be used by a proposed Federal
             endangered species)  or statutory definition (e.g., wetlands) but are not statutorily
             delineated.

       Evaluating sensitive environments that fall  into the first category is relatively straightforward,
because the areas are  officially designated and delineated. Evaluating environments that fall into the
second category requires professional judgment both to determine if an area is eligible for scoring and to
delineate the eligible area. This section provides descriptive criteria and examples to assist  in evaluating
sensitive environments in the latter category.

       General pathway-specific eligibility requirements are listed below.

AIR PATHWAY

       All portions of all sensitive environments at least partially within the TDL are eligible, with the
following qualifier: terrestrial areas utilized for breeding  by large or dense aggregations of animals are
limited to those used by terrestrial vertebrate species.

SOIL EXPOSURE PATHWAY

       Only terrestrial sensitive  environments (as  listed in MRS Table 5-5) that are at least  partially on
an area of observed contamination are eligible. Terrestrial portions of other sensitive environments, and
portions of wetlands that are periodically out of water, may be eligible to be evaluated as a terrestrial
sensitive environment (see Section 9.6).

SURFACE WATER PATHWAY

       All surface water (and wetland) portions of the sensitive environment at least partially within the
TDL for a watershed are eligible  to be evaluated for that watershed. Circumstances under which
                                          A-1
                                                                               Section A-1

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terrestrial sensitive environments or terrestrial portions of a sensitive environment are eligible are
illustrated in Highlight A-1 and described below.

               Terrestrial sensitive environments that are not defined by the presence of one or more
               particular species (e.g., wildlife refuges) and whose boundaries cross or border a surface
               water body within the TDL for a watershed are eligible to be evaluated for that
               watershed.

               Terrestrial sensitive environments that are defined by the presence of one or more
               particular species (e.g., habitat known to be used by an endangered  or threatened
               species, terrestrial areas used for breeding by large or dense aggregations of animals)
               and whose boundaries cross or border a surface water body within the TDL for a
               watershed are eligible to be evaluated for the watershed unless there is clear information
               that the particular species of concern is unlikely to come into contact with the surface
               water body or bodies within the TDL. Examples include terrestrial plant species not
               located in floodplains and terrestrial animal species that rarely or never drink water.

               Terrestrial sensitive environments that are defined by the presence of one or more
               particular species and whose boundaries do not cross or border a surface water body
               within the TDL are eligible to be evaluated for that watershed only if there is clear
               information that the particular species of concern is likely to come into contact with the
               surface water body or bodies within the TDL. Examples of such information include
               evidence that grouse from a display ground some distance from water regularly use a
               surface water body within the TDL for drinking or bathing; evidence that a bald eagle
               nesting several miles from water is known to forage in a surface water body within the
               TDL (note that such evidence probably would be sufficient to demonstrate that the
               surface water body was habitat known to be used by the bald eagle).

HIGHLIGHT A-1
ELIGIBILITY REQUIREMENTS FOR EVALUATING TERRESTRIAL
SENSITIVE ENVIRONMENTS IN SURFACE WATER PATHWAY
Area Delineated by
Presence of One or
More Species
Yes
No
Boundary of Area Crosses or
Borders Surface Water Body
within TDL
Yes
No
Yes
No
Eligibility Requirements
Eligibility unless species of
concern is unlikely to contact
surface water within TDL
Not eligible unless species of
concern is likely to contact
surface water within TDL
Always eligible
Never eligible


Section A-1
                                              A-2

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SECTION  A.2
DEFINITIONS OF
SENSITIVE
ENVIRONMENTS
INCLUDING WETLANDS
WWUHJOIGMIMII
       This section defines all sensitive environments in MRS Tables 4-23 and 5-5, as well as wetlands.
These definitions, presented in alphabetical order, are intended to assist the scorer in identifying
sensitive environments that may be applicable to the surface water, soil exposure, or air pathway(s).
Each definition includes a general section applicable to all pertinent pathways (i.e., surface water, soil
exposure, and air), followed by a pathway-specific discussion. The statutory authority for designating the
sensitive environment, where appropriate, also is \nc\uded.Highlight A-2 defines key terms used in
defining sensitive environments. This section also includes a discussion of the relationship between
wetlands definitions used by the U.S. Fish and Wildlife Service (USFWS) and the MRS.
                                       HIGHLIGHT A-2
                   KEY TERMS USED IN DEFINING SENSITIVE ENVIRONMENTS

 Aquatic Vertebrate Species: Vertebrate species that lay eggs or bear young in water. Includes all fishes, nearly
 all amphibians, and a few mammals (i.e., manatees, whales, porpoises).

 Recognized Expert: A university professor  or member of a professional society in a discipline such as
 ornithology, herpetology, ichthyology, entomology, or botany. The individual also must have authored at least one
 peer-reviewed scientific publication on the geographic area or species of concern.

 Species Habitat: The place where a population of a species normally lives and its surrounding area, both living
 and nonliving. Habitat generally is characterized by dominant plant form (e.g., broadleaf deciduous forest) and/or
 physical characteristics (e.g., fast-moving stream with rocky substrate).
 Species Range: The geographic extent over which a species occurs, including areas that comprise suitable
 habitat as well as those that do not. Current range is the geographic extent over which the species occurs a
 present; historic range Is the geographic extent over which the species occurred at some time in the past.

 Terrestrial Vertebrate Species: Vertebrate species that lay eggs or bear young outside of water. Includes all
 reptiles, all birds, most mammals, and amphibians that lay their eggs in shaded, moist sites on land.

 Vertebrate Species: Animals belonging to the Phylum Chordata Subphylurn Vertebrata. Includes organisms
 in the Class Aqnatha  (e.g., lampreys), Class Chondrichthyes (e.g., sharks, rays), Class Osteichthyes (most
 living forms of fishes),  Class Amphibia  (e.g., frogs, toads, salamanders), Class Reptili  (e.g., snakes, lizards,
 turtles, alligators), Class Aves (birds), and Class Mammalia (mammals).

 Vertebrate Species with Semi-aquatic Habits: Vertebrate species that either breed in water but live primarily
 on land (e.g., many amphibians) or breed out of water but live primarily in water (e.g., waterfowl, turtles, alligators,
 seals). Species in the former category are termed aquatic species with semi-aquatic habits; species in the latter
 category are termed terrestrial species with semi-aquatic habits.

                                             A-3
                                                                                     Section A.2

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ADMINISTRATIVELY PROPOSED FEDERAL WILDERNESS AREA

General

       Remote areas of undeveloped Federal lands proposed by U.S. Forest Service (USFS), National
Park Service (NPS), USFWS, or the Bureau of Land Management (BLM) to become a Federal
Wilderness Area based on their primeval character and influence, lack of permanent roads, and lack of
permanent improvements or human habitation. Areas must be proposed in the Federal Register for
Federal Wilderness Area status to meet this definition. Areas already designated by Congress as Federal
Wilderness Areas are considered a separate sensitive environment in the MRS (see subsection below,
Designated Federal Wilderness Area). Statutory Authority:  National Wilderness Preservation Act (16
U.S.C. § 1131,efseg.).

Pathway Specific

              Air - General eligibility requirements apply.
              Soil exposure - General eligibility requirements apply.
              Surface water - General eligibility requirements apply.

AREAS IDENTIFIED UNDER THE COASTAL ZONE MANAGEMENT ACT

General

       Areas of coastal waters, the Great Lakes, and their connecting waters identified in state Coastal
Zone Management Plans as requiring protection because of their ecological value. The following areas
meet this definition for MRS purposes:

              Areas designated by the Secretary of Commerce as a National Estuarine  Research
              Reserve (proposed areas are not eligible).

              Areas (identified in the Act) designated as of particular concern in a final State Coastal
              Zone Management Plan that has been approved by the National Oceanic and
              Atmospheric Administration  (NOAA):

              —     Areas of unique, scarce, fragile, or vulnerable habitat.

              —     Areas of high natural productivity or essential habitat for living resources,
                     including fish, wildlife, endangered species, and the various trophic levels in
                     the food web critical to their well-being.

              —     Areas needed to protect, maintain, or replenish coastal lands or resources,
                     including coastal flood plains, aquifers and their recharge areas, estuaries,
                     sand dunes, coral and other reefs, beaches, offshore sand deposits,  and
                     mangrove stands.

              Areas proposed, designated, or otherwise identified in draft plans that have not been
              approved by NOAA are not eligible for MRS  purposes.  Moreover, areas designated as of
              particular concern for reasons (defined by the Act) other than their ecological value do
              not meet this definition. Examples  include areas of urban concentration where shoreline
              utilization and water uses are highly competitive and areas where developments and
              facilities are dependent upon the utilization of or access to coastal waters. Note that
              some National Estuarine Research Reserves were formerly designated as National
              Estuarine Sanctuaries. Statutory Authority:  Coastal Zone Management Act (16 U.S.C. §
              1451, e/set/.; 15 CFR921, etseq.; 15 CFR 923, et seq.)


Section A.2                                   A-4

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Pathway Specific

              Air - General eligibility requirements apply.
              Soil  exposure - Category is not evaluated.
              Surface water - General eligibility requirements apply.

COASTAL BARRIER - PARTIALLY DEVELOPED

General

       Coastal barriers that are  no more than 50 percent developed and that are not designated as units
of the Coastal Barrier Resources System. A coastal barrier is a depositional geologic feature (e.g., a bay
barrier, tombolo, barrier spit, or barrier island) that consists of unconsolidated sedimentary materials; is
subject to wave, tidal, and wind energies; and protects landward aquatic habitats from direct wave attack.
The coastal barrier includes all associated  aquatic habitats, including the adjacent wetlands, marshes,
estuaries, inlets, and nearshore waters. Under the Coastal Barrier Resources Act, a coastal  barrier is
considered partially developed if no more than 50 percent of the fastland area (i.e., the area between the
landward and shoreward sides of the barrier) is covered by one or more man-made structures (i.e.,
walled and roofed buildings constructed in  conformance with legal requirements, with a projected ground
area exceeding 200  square feet)  per 5 acres  of fastland area. A coastal barrier that is more than 50
percent developed is not eligible  for evaluation  as a partially developed coastal barrier. Partially
developed coastal barriers that are designated  as units of the Coastal Barrier Resources System are
considered a separate sensitive environment for MRS purposes (see subsection below, Coastal Barrier -
Undeveloped). Highlight A-3 summarizes  criteria for determining the appropriate MRS sensitive
environments category for a coastal barrier. Statutory Authority: Units of the Coastal Barrier Resource
System are designated under the Coastal Barrier Resources Act (16 U.S.C. § 3501,ef seq.); coastal
barriers that meet the definition for this sensitive environment are not statutorily defined.

Pathway Specific

              Air - General eligibility  requirements apply.
              Soil  exposure - Category is not evaluated.
              Surface water - General eligibility requirements apply.

COASTAL BARRIER - UNDEVELOPED

General

       Undeveloped coastal barriers that  are not designated as units of the Coastal Barrier Resources
System. A coastal barrier is a depositional  geologic feature (e.g., a bay barrier, tombolo, barrier spit, or
barrier island) that consists of unconsolidated sedimentary materials; is subject to wave, tidal, and wind
energies; and protects landward  aquatic habitats from direct wave attack. The coastal barrier includes all
associated aquatic habitats, including any  adjacent wetlands,  marshes, estuaries, inlets, and/or
nearshore waters. Under the Coastal Barrier  Resources Act, the definition of an undeveloped barrier
varies according to whether the entire barrier is being considered or only a portion is being considered. If
the entire barrier is being considered, it must contain (on average) fewer than one man-made structure
(i.e., a walled and roofed building constructed in conformance with legal requirements, with a projected
ground area exceeding 200 square feet) per 5 acres of fastland area (i.e., the area  between  the landward
and shoreward sides of the barrier). If only a  portion of the barrier is being considered, the portion must
have at least 1/4-mile of undeveloped shoreline on the shoreward side  of the coastal barrier, and the
undeveloped area must extend through the fastland from the beach to the associated landward aquatic
habitat. Undeveloped coastal barriers that  are designated as units of the Coastal Barrier Resources
System are considered a separate sensitive environment for MRS purposes (see subsection above,
Coastal Barrier- Partially Developed). See Highlight A-3 for a summary of criteria for determining the
appropriate MRS sensitive

                                             A-5                                     Section A.2

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HIGHLIGHT A-3
DETERMINING HRS CATEGORIES FOR COASTAL BARRIER
Description
Area designated as a Unit of the Coastal Barrier Resources System
"Otherwise Protected" area depicted on Coastal Barrier Resources System maps
Area not designated
as a Unit of the
Coastal Barrier
System
Entire barrier — fewer than one man-made structure per
5 acres of fastland area
Portion of barrier — at least 1/4-mile of undeveloped
shoreline on the shoreward side, with the undeveloped
area extending through the fastland area from the beach
to the associated landward aquatic habitat
No more than 50 percent of fastland area covered by one
or more man-made structures per 5 acres of fastland area
At least 50 percent of fastland area covered by one or
more man-made structures per 5 acres of fastland area
HSR Category
Unit of Coastal Barrier
Resources System
Not eligible unless it
can be classified as
partially developed or
undeveloped coastal
barrier
Coastal Barrier
(Undeveloped)
Coastal Barrier
(Partially Developed)
Not eligible


environments category for a coastal barrier. Statutory Authority: Units of the Coastal Barrier Resource
System are designated under the Coastal Barrier Resources Act (16 U.S.C. § 3501,ef seq.); coastal
barriers that meet the definition of this sensitive environment are not statutorily defined.

Pathway Specific

              Air - General eligibility requirements apply.
              Soil exposure - Category is not evaluated.
              Surface water - General eligibility requirements apply.

CRITICAL AREAS IDENTIFIED UNDER THE CLEAN LAKES PROGRAM

General

       Subareas within publicly owned lakes, or in some cases entire, small, publicly owned lakes,
identified in State Clean Lakes Plans as critical habitat under the Clean Water Act (commonly referred to
as the section 305(b) report). Each state is required to submit:  a Clean Lakes plan to receive grant
assistance under section 314 of the Clean Water Act. Statutory Authority:  section 314 of the Clean
Water Act (33 USC § 1324).
Section A.2
                                           A-6

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Pathway Specific

              Air - General eligibility requirements apply.
              Soil exposure - Category is not evaluated.
              Surface water - General eligibility requirements apply.

CRITICAL HABITAT FOR FEDERAL DESIGNATED ENDANGERED OR THREATENED SPECIES

General

       Habitat designated by the Secretary of the Interior as critical to the survival of an endangered or
threatened species. Only those areas listed in 50 CFR 17.95 (critical habitats for fish and wildlife species)
or 17.96 (critical habitats  for plant species) meet this definition for MRS purposes; areas proposed as
critical habitat do not meet this definition. Other habitat areas known to be used by the species are
considered a separate sensitive environment in the MRS (see ). Note that critical habitat  has not been
designated for all endangered or threatened species. Statutory Authority: Endangered Species Act (16
U.S.C. § 1531,efseqf.;  50 CFR 424.02).

Pathway Specific

              Air - General eligibility requirements apply.

              Soil exposure - Category is evaluated for the soil exposure pathway only if the
              designated critical habitat includes one or more terrestrial areas within an area of
              observed contamination.

              Surface water- Category is evaluated only if the designated critical habitat includes one
              or more surface water bodies within the TDL.

DESIGNATED FEDERAL WILDERNESS AREA

General

       Remote areas of  undeveloped Federal land designated by an act of Congress as a Federal
Wilderness Area based on their primeval character and influence and lack of permanent  roads,
improvements, or human  habitation. Federal Wilderness Areas are administered either by the USFS,
NPS, USFWS, or BLM. Proposed Federal Wilderness Areas are considered a separate sensitive
environment in the MRS. Statutory Authority:  National Wilderness Preservation Act (16 U.S.C. § 1131,
et seq.).

Pathway Specific

              Air - General eligibility requirements apply.
              Soil exposure - General eligibility requirements apply.
              Surface water - General eligibility requirements apply.

FEDERAL DESIGNATED SCENIC OR WILD  RIVER

General

       Rivers or segments of rivers (and the related adjacent land area) that are (1)  designated as
National Wild  and Scenic Rivers by an act of Congress or the Secretary  of the Interior based on their
degree of free-flow; lack of development; and the outstanding scenic, natural, and cultural characteristics
of the segments and their surrounding environments and (2) classified as wild or scenic.  Under the Wild
and Scenic Rivers Act,  segments are designated wild because they are free of impoundments and
generally accessible only by trail, with essentially primitive watersheds or


                                            A-7                                    Section A.2

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shorelines, and unpolluted waters. Segments are designated scenic because they are free of
impoundments, with shorelines or watersheds still largely undeveloped, but accessible In places by
roads. Administering agencies and the conditions under which a river segment is designated a National
Wild and Scenic River are listed under National River Reach Designated as Recreational. Note that
National Wild and Scenic Rivers may be classified either as wild, scenic, or recreational; segments
classified as recreational are considered a separate sensitive environment in the MRS (see subsection
below, National River Reach Designated as Recreational). River segments designated by a state as wild
or scenic, but not included in the national system, also are considered a separate sensitive environment
in the MRS (see subsection below, State Designated Scenic or Wild R\ver).HighlightA-4 summarizes
criteria for determining the appropriate MRS sensitive environments category for a wild or scenic river.
Statutory Authority:  National Wild and Scenic Rivers Act (16 U.S.C. §§ 1271-1287).

Pathway Specific

              Air - General eligibility requirements apply.
              Soil exposure - Category is not evaluated.
              Surface water - General eligibility requirements  apply.

FEDERAL LAND DESIGNATED FOR THE PROTECTION  OF NATURAL ECOSYSTEMS
General

       This sensitive environment includes two types of areas:  (1) public lands designated by an
appropriate Federal Agency (e.g., USFS, BLM, Bureau of Indian Affairs (BIA), Minerals Management
Service (MMS), Office of Surface Mining (OSM)) in a relevant document as an area for protecting
natural ecosystems (e.g., a BLM Area of Critical Environmental Concern), and (2) public lands
established as Wildlife Mitigation Areas in accordance with an environmental impact statement (EIS) for
Federal land. Statutory Authority: sections 103(a) and 202(c)(3) of the Federal Land Policy and
Management Act (43 U.S.C. §§ 1702(a), 1712(c)(3)).
HIGHLIGHT A-4
HRS CATEGORIES FOR WILD AND SCENIC RIVERS

Designation
National Wild and
Scenic River
Classification
Recreational
Wild
Scenic
State Scenic River or State Wild River
not included in National Wild and
Scenic River System
State Scenic River or State Wild River
included in National Wild and Scenic
River System
HRS Category
National River Reach Designated as Recreational
Federal Designated Scenic or Wild River
Federal Designated Scenic or Wild River
State Designated Scenic or Wild River
National River Reach Designated as Recreational or
Federal Designated Scenic or Wild River, as
appropriate (see above)


Section A.2
                                            A-8

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Pathway Specific

              Air - General eligibility requirements apply.
              Soil  exposure - General eligibility requirements apply.
              Surface water - General eligibility requirements apply.

HABITAT KNOWN TO BE USED BY FEDERAL DESIGNATED OR PROPOSED ENDANGERED OR
THREATENED SPECIES

General

       Areas known to be used by a species designated or proposed for designation by the Secretary of
the Interior as endangered or threatened by listing in 50 CFR 17.11 (fish and wildlife), listing in 50 CFR
17.12 (plants), or notification in the Federal Register. Definition  does not include those areas that are
designated as critical habitat for the endangered or  threatened species; such areas are considered a
separate sensitive environment in the MRS. To evaluate this sensitive environment, provide evidence
that at least one member of the species is present in and is using the  habitat within the TDL. Field survey
evidence (not necessarily direct sightings) should be sufficient  to  conclude that the species would likely
be found in the habitat. Note that evidence of presence but not use, (e.g., sighting an individual member
of a species flying over the habitat) generally will not be sufficient. Examples of sufficient evidence
include (but are not limited to):

              A recent sighting (e.g., within the past five years) has been made by a representative of
              an appropriate Federal, state, county, or local agency (e.g., USFWS, National Marine
              Fisheries  Service (NMFS), state fish and game department, state Natural Heritage
              program) or by a recognized expert, preferably written on official letterhead, of at least
              one  individual member of the species within and using the area of concern.

              A written statement from a representative of an appropriate Federal, state, county, or
              local agency, or from a recognized expert indicates that the area of concern is suitable
              habitat for and is within the current range of the species in question.

              Evidence  from a published document or logbook indicates that the area of concern is
              suitable habitat for and is within the current range of the species of concern. Only
              original, primary sources are suitable; secondary sources such as an EIS are not. For
              example, a statement in an EIS that an endangered species was seen using the surface
              water body during a site survey is not sufficient evidence; the logbook or original notes of
              the individual making the observation may be sufficient evidence. Statutory Authority:
              endangered and threatened species are designated or proposed under the Endangered
              Species Act (15 U.S.C. § 1531, et seq.); habitat known to be used by these species is
              not statutorily defined.
Pathway Specific
              Air- Document suitable terrestrial or aquatic habitat and current range of the species
              within the TDL.

              Soil exposure - It generally will be sufficient to document suitable terrestrial habitat and
              current range or the presence of the species within at least one area of observed
              contamination. Evidence will  be strengthened by documenting that the species spends
              all or a considerable portion of its time in direct contact with surface soils (e.g., plants,
              snakes, burrowing mammals) or consumes such organisms (e.g., birds that eat worms,
              owls or hawks that eat small  rodents).

              Surface water - For aquatic species (e.g.,  fish, whales) or aquatic species with semi-
              aquatic habits (e.g., toads, salamanders),  it generally will be sufficient to document
                                             A-9                                     Section A.2

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              suitable habitat used by the species (e.g., for feeding or breeding) or the presence of the
              species within one or more surface water bodies (or wetlands) within the TDL. For
              terrestrial species with semi-aquatic habits (e.g., herons, mink), it generally will be
              necessary to document that the species of concern is likely to come into contact with one
              or more surface water bodies within the TDL (e.g., the species consumes fish or other
              aquatic organisms that might inhabit the surface water body or drinks water from similar
              types of surface water bodies). Habitat used by terrestrial species that are unlikely to
              contact surface water within the TDL is generally not eligible (e.g., terrestrial plant
              species not located in floodplain areas, terrestrial animal species that rarely or never
              drink water).

HABITAT KNOWN TO BE USED BY SPECIES UNDER REVIEW AS TO ITS FEDERAL
ENDANGERED OR THREATENED STATUS

General

       Areas known to be used by a species which the Secretary of the  Interior has formally  announced
is under review as to its Federal endangered or threatened status by notification in  the most recent
Comprehensive Notice of Review (fish, wildlife, and plant species) or Candidate Species List  (marine
animal species) published in the Federal Register. The USFWS publishes one Comprehensive Notice of
Review each year with plant and  animal species included in alternating years (e.g., animals were
published in 1989, plants were published in 1990). NOAA publishes a candidate species list periodically,
as needed. The definition of this sensitive environment category is identical to habitat known to be used
by Federal designated endangered or threatened species, with the following exceptions:

              If the species of concern also is a state designated or proposed endangered or
              threatened species, evaluate the habitat either as habitat used by a state endangered or
              threatened species, or as habitat used by a species under review as to its Federal
              endangered or threatened status, but not as both, using the higher of the appropriate
              scores.

              For eligible species, this definition includes areas designated as critical or important
              habitat for the endangered or threatened species of concern, as long as it can be
              established that the species  is  present In and uses these areas.

Statutory Authority: Endangered  Species Act (15 U.S.C. § 1531,ef seq.).

Pathway Specific

              See subsection above, Habitat Known to be  Used by Federal Designated Endangered or
              Threatened Species, for pathway-specific information.

HABITAT KNOWN TO BE USED BY STATE DESIGNATED ENDANGERED OR THREATENED
SPECIES

General

       Areas known to be used by a species designated as endangered or threatened within the  state by
the Governor, administering agency, or state legislature. The definition of this sensitive environment
category is identical to habitat known to be used by Federal designated endangered or threatened
species, with the following exceptions:

              If the species of concern also is a Federal designated or proposed  endangered or
              threatened species, the species should not be  considered a state endangered or
Section A.2                                    A-10

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              threatened species for MRS purposes. Evaluate habitat known to be used by a Federal
              designated or proposed endangered or threatened species).

              Species that are proposed for designation as endangered or threatened by the state do
              not meet this definition for MRS purposes.

              For eligible species, this definition includes areas designated as critical or important
              habitat for the endangered or threatened species of concern.

       Note that species listed as "significantly rare" or "of special concern" in the state are not eligible
under this category unless they have been designated as endangered or threatened within the state.
Statutory Authority: state endangered species laws.

Pathway Specific

              See subsection above, Habitat Known to be Used by Federal Designated Endangered or
              Threatened Species, for pathway-specific information.

MARINE SANCTUARY

General

       Areas of coastal and ocean waters, the Great Lakes, and their connecting waters designated as a
National Marine Sanctuary by the Secretary of Commerce based on their conservation, recreational,
ecological, or aesthetic values. All National Marine Sanctuaries are administered by NOAA. Proposed
National Marine Sanctuaries do not meet this definition for MRS purposes. Statutory Authority: Marine
Protection Research and Sanctuaries Act (16 U.S.C. § 1431,ef seq,; 15 CFR 922.1 and 15 CFR 922.2).

Pathway Specific

              Air—  General eligibility requirements apply.
              Soil exposure —  Category is not evaluated.
              Surface water—  General eligibility requirements apply.

MIGRATORY PATHWAYS AND FEEDING AREAS CRITICAL FOR MAINTENANCE OF
ANADROMOUS FISH SPECIES WITHIN RIVER  REACHES OR AREAS IN LAKES OR COASTAL
TIDAL WATERS  IN WHICH THE FISH SPEND EXTENDED PERIODS OF TIME

General

       Surface water bodies along or contiguous to the hazardous substance migration path  that are
identified by a representative of an appropriate Federal, state, county, or local agency or by a recognized
expert as critical migratory pathways or feeding areas for anadromous fish species (i.e., species such as
salmon and striped bass that spend most of their  adult lives in the ocean but migrate to freshwater or low
salinity coastal tidal waters for breeding). Only areas in which adult, juvenile, or larval forms of the
species of concern spend prolonged  periods of time meet this definition for MRS purposes. Appropriate
agencies are limited to the Comprehensive Environmental Response, Compensation, and Liability Act
(CERCLA) natural resource trustees  highlight A-5) and state or local agencies that have statutory
responsibility for or involvement in management of the area or species of concern (e.g., state fish and
game departments). Provide the individual with the definitional criteria (i.e., as stated in MRS Table 4-23)
to determine whether any surface water body or bodies within the TDL meets this definition. Obtain
written documentation (on appropriate letterhead) that the area of concern is a critical migratory pathway
and/or feeding area as well as some  information about the species and habitats of concern (e.g., some
explanation as to why the habitat is critical). Examples of appropriate documentation are provided in
Highlight A-6. Statutory Authority: Not statutorily defined.

                                            A-11                                    Section A.2

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Seer
natu
desi
toth
they
HIGHLIGHT A-5
CERCLA NATURAL RESOURCE TRUSTEES
Government Level
Federal3
State"
Native American Tribes0
Designated Trustee
Secretary of the Interior
Secretary of Commerce
Secretary of Agriculture
Secretary of Energy
Secretary of Defense
State official designated
by the Governor
Tribal Chairman or head
of the governing body
of a tribe
Delegated Trustee
USFWS
uses
NPS
MMS
BLM
Bureau of Indian Affairs
Bureau of Reclamation
NOAA Costal Resource Coordinators

Individual designated by Tribal
Chairman or head of governing body
BIA, if requested by tribe

aBy Executive Order 12580, and in the National Contingency Plan (NCR), the President has designated the
etary of the Departments of the Interior, Commerce, Agriculture, Energy, and Defense as Federal trustees for
ral resources.
b Superfund Amendments and Reauthorization Act (SARA) Section 107(d) requires each Governor to
gnate state trustees for natural resources within the boundaries of, belonging to, controlled by, or appertaining
e state; most Governors have done so.
c Native American Tribes are trustees for resources on or related to tribal lands or for resources for which
may have treaty rights.
Pathway Specific

              Air— General eligibility requirements apply.
              Soil exposure —  Category is not evaluated.
              Surface water—  General eligibility requirements apply.

NATIONAL LAKESHORE RECREATIONAL AREA

General

       A lakeshore designated by an act of Congress as a National Lakeshore Recreational Area
because of its recreational and ecological values. All National Lakeshore Recreational Areas are
administered by NPS. Not all lakeshore areas administered by NPS (or other agencies) are designated
National Lakeshore Recreational Areas. Statutory Authority:  16 U.S.C. § ~\,et seq.
Section A.2
                                           A-12

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                                    HIGHLIGHT A-6
                       APPROPRIATE DOCUMENTATION FOR
          MIGRATORY PATHWAYS AND FEEDING AREAS CRITICAL FOR
             MAINTENANCE OF ANADROMOUS FISH SPECIES WITHIN
                   RIVERS, LAKES, OR COASTAL TIDAL WATERS

 Based on written statements from CERCLA Natural Resource Trustee Agency

 Example 1: "Information from the [state fish and game department] that [identified surface water bodies]
 are moderately to heavily used by anadromous fishes for transportation and/or rearing. Substantial runs
 of [identified fish  species] use these waters en route to or from upriver spawning grounds. [Identified
 surface water bodies] provide critical salt/fresh water transition habitat where [identified fish species] must
 acclimate before moving from one environment to the other. This site is near critical migratory pathways
 and feeding areas."

 Example 2:  "The [identified surface water body] in this area is a major migration and feeding area for
 salmon [referenced personal communication from representative of state fish and game department].
 Anadromous species of concern are: [identified fish species]. The [identified fish species] is a candidate
 species for listing  under the Endangered Species Act, and a petition for listing has been submitted for the
 [identified fish species]. This site is near a critical migratory pathway and feeding area."
Pathway Specific

              Air— General eligibility requirements apply.
              Soil exposure — Category is not evaluated.
              Surface water— General eligibility requirements apply.

NATIONAL MONUMENT

General

       Areas designated by an act of Congress as National Monuments because of their cultural or
historical significance. All National Monuments are administered by NPS. Not all lands administered by
NPS are designated National Monuments. Statutory Authority: 16 U.S.C. § 1, etseq.

Pathway Specific

              Air— General eligibility requirements apply.
              Soil exposure — Category is not evaluated.
              Surface water— General eligibility requirements apply.

NATIONAL OR STATE WILDLIFE REFUGE

General

       Area designated for the protection offish and wildlife, within which hunting and fishing are either
prohibited or strictly controlled. National Wildlife Refuges are designated by an act of Congress or
through Executive Order, by the President, and are administered by USFWS. State Wildlife Refuges are
designated by a state Governor, administrative agency, or legislature, and are administered by the
appropriate state  agency. Proposed National and State Wildlife Refuges do not meet this definition for
MRS purposes. Statutory Authority: National Wildlife Refuge Administration Act of 1966 (16 U.S.C. §§
668dd-668ee) or comparable state law.
                                           A-13                                   Section A.2

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Pathway Specific

              Air— General eligibility requirements apply.
              Soil exposure — General eligibility requirements apply.
              Surface water— General eligibility requirements apply.

NATIONAL PARK

General

       Area designated by an act of Congress as a National Park for purposes of protection and
recreation based on its uniquenatural, historic, or cultural values. All National Parks are administered by
NPS. Not all lands administered by NPS are designated as National Parks. Statutory Authority: 16
U.S.C. § 1, etseq.).

Pathway Specific

              Air— General eligibility requirements apply.
              Soil exposure — General eligibility requirements apply.
              Surface water— General eligibility requirements apply.

NATIONAL PRESERVE

General

       Area designated by an act of Congress as a National Preserve because of its unique flora and
fauna. All National Preserves are administered by NPS. Not all areas administered by NPS (or other
agencies) are designated National Preserves. Statutory Authority: 16 U.S.C. § 1,ef seq.

Pathway Specific

              Air— General eligibility requirements apply.
              Soil exposure — General eligibility requirements apply.
              Surface water— General eligibility requirements apply.

NATIONAL RIVER REACH DESIGNATED AS RECREATIONAL

General

       Rivers or segments of rivers (and the related  adjacent land area) that are both (1) designated as
National Wild and Scenic Rivers by an act of Congress or the Secretary of the Interior based on their
degree of free-flow, lack of development, and the outstanding scenic natural and cultural characteristics
of the segments and their surrounding environments  and  (2) classified as recreational. Under the Wild
and Scenic Rivers Act, segments are classified  as recreational because they are readily accessible by
road or railroad, may have some development along their shoreline, and may have undergone some
impoundment or diversion in the past. The Secretary  of the Interior can designate a river segment as a
National Wild and Scenic River only if the river has been designated  "wild and scenic" by one or more
state(s). To obtain designation the Governor of the state(s) submits an application to the Secretary, the
Secretary determines that the river has the necessary outstanding values to meet the criteria for
inclusion in the National Wild and Scenic Rivers System, and the Secretary determines that the state(s)
will protect these values. National Wild and Scenic Rivers are administered either by a Federal agency
(i.e., NPS, USFWS, USFS, or BLM), a state agency, or a Native American Tribe. Note that National Wild
and Scenic Rivers may be classified either as wild, scenic, or recreational; segments classified as wild or
scenic are considered a separate sensitive environment in the MRS (see subsection above, Federal
Designated Scenic or Wild River). See Highlight Xl-4for a summary of criteria for determining the
appropriate MRS sensitive environments


Section A.2                                    A-14

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category for a wild or scenic river. Statutory Authority: National Wild and Scenic Rivers Act (16 U.S.C.
§§ 1271-1287).

Pathway Specific

              Air— General eligibility requirements apply.
              Soil exposure — Category is not evaluated.
              Surface water— General eligibility requirements apply.

NATIONAL SEASHORE RECREATIONAL AREA

General

       Coastline designated by an act of Congress as a National Seashore Recreational Area because
of its recreational and ecological values. All National Seashore Recreational Areas are administered by
NPS. Not all coastal  areas administered by NPS are designated National Seashore Recreational Area.
Statutory Authority: 16 U.S.C. § 1, et seq.

Pathway Specific

              Air— General eligibility requirements apply.
              Soil exposure — Category is not evaluated.
              Surface water— General eligibility requirements apply.

PARTICULAR AREAS,  RELATIVELY SMALL IN SIZE, IMPORTANT TO MAINTENANCE OF UNIQUE
BIOTIC COMMUNITIES

General

       Areas that are important for the maintenance of unique, rare, or otherwise ecologically valuable
biotic communities. Eligible areas differ by pathway (see below). This definition generally includes but is
not limited to the following four types of areas:

              Areas with a high proportion of species with highly restrictive habitat requirements due to
              unusual natural biotic and/or abiotic conditions;

              Highly isolated area that may or may not have an  unusual community structure per se,
              but because of its geographic isolation is particularly important to the continued
              existence of that community;

              Areas with a high proportion of species that are locally endemic because of a relatively
              long  period of geographic isolation and/or are exceptional examples of "climax"
              communities because of minimal human  disturbance; or

              Areas vital for a species that are important to the maintenance of a community.

Statutory Authority: Not statutorily defined.

Pathway Specific

              Air — Eligible areas include those areas listed for the surface water and soil exposure
              pathways that are at least partially within the TDL.

              Soil exposure — Eligible areas are limited to terrestrial areas at least partially within an
              area of observed contamination. Examples of the  first type of area may include riparian
              woodlands in arid/semi-arid areas; sand  dunes and other coastal areas with


                                            A-15                                     Section A.2

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              high salinity; high-altitude tundra; coastal pine barrens, and cove forests. Examples of
              the second type of area may include small patches of tall grass prairie within agricultural
              areas and old-growth forest areas.  Examples of the third type of area may include
              "hammocks" of Florida and some mountain-top communities in arid/semi-arid areas.
              Examples of the fourth type of area may include traditional roosting areas for species
              important to a community (e.g., turkey vulture roosts). Note that communal roosts for
              other types of species (e.g., starlings, blackbirds) generally are not eligible.

              Surface water— Eligible areas include surface water bodies (including wetlands)
              located along the hazardous substance migration path for a watershed. Examples of the
              first type of area may include volcanic lakes, hot springs, salt lakes, alkali lakes, peat
              bogs, and bog lakes. Examples of the second type of area may include small water
              bodies or wetlands in otherwise dry areas (e.g., prairie potholes, playas, pocosins, vernal
              pools, wet meadows) or other unique surface water bodies (e.g., alligator holes). Note
              that other types of wetlands do not  qualify under this  category. Examples of the third
              type of area may include water bodies located in relatively ancient or remnant geological
              formations. Examples of the fourth type of area may include isolated surface water
              bodies in arid areas that are important amphibian breeding ponds.

SENSITIVE AREAS IDENTIFIED UNDER NATIONAL ESTUARY PROGRAM OR NEAR COASTAL
WATERS PROGRAM

General

       Subareas within estuaries or near coastal waters identified in state Comprehensive Conservation
and Management Plans, filed with EPA, because they support critical life stages of key estuarine or
coastal species. Statutory Authority:  Sections 104(b)(3), 304(1), 319, and 320 of the Clean Water Act
(33 U.S.C. §§ 1254(b)(3), 1314(1), 1329, and 1330).

Pathway Specific

              Air— General eligibility requirements apply.
              Soil exposure — Category is not evaluated.
              Surface water— General eligibility requirements apply.

SPAWNING AREAS CRITICAL FOR THE MAINTENANCE OF FISH/SHELLFISH SPECIES WITHIN
RIVER, LAKE, OR COASTAL TIDAL WATERS

General

       Areas that are used for intensive or concentrated spawning by fish or shellfish species and are
identified by a representative of an appropriate Federal,  state, county, or local agency or by a recognized
expert as critical for the maintenance of fish or shellfish  species within river, lake or coastal tidal waters.
Appropriate agencies are limited to the natural resource  trustees designated under CERCLA (see
Highlight A-5) and state or local agencies that have statutory responsibility for or involvement in
management of the area or species of concern (e.g., state fish and game departments), even if these
agencies are not designated CERCLA natural resource trustees. The scorer should provide the
appropriate agency representative or recognized expert with the definitional criteria (i.e., as stated in
MRS Table 4-23) to determine whether any surface water body or bodies within the TDL meets this
definition. Obtain written documentation (on appropriate  letterhead) that the area of concern is a critical
spawning area as well as some information about the species and habitat(s) of concern (e.g., some
explanation as to why the habitat is critical). Examples of appropriate documentation are provided in
Highlight A-7. Fish and shellfish spawning typically involves the release of gametes (ova and sperm)
into the water column; however, species with internal fertilization are  not necessarily excluded. Areas
critical for the survival or maintenance of larval or
Section A.2                                    A-16

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                                     HIGHLIGHT A-7
                 APPROPRIATE DOCUMENTATION FOR SPAWNING
             AREAS CRITICAL FOR  MAINTENANCE OF FISH/SHELLFISH
          SPECIES WITHIN RIVERS, LAKES, OR COASTAL TIDAL WATERS

 Based on written statements from CERCLA Natural Resource Trustee Agency

 Example 1:  "Salmonid spawning is widespread; generally any tributary that is physically accessible within
 [water bodies within the  TDL] is utilized for spawning by salmon and trout [literature citations]. As noted
 earlier, regionally heavy watershed development has impacted fish production capabilities of upstream
 tributaries. Also, it must be noted that the study area is a small percentage of the entire spawning habitat
 available, particularly for [specified water  basins]. Further, these systems each have numerous small
 unnamed tributaries. As such, a large percentage of preferred spawning habitat is outside of the study
 area or unmentioned. Nonetheless, recognized important spawning tributaries for each sub-basin are
 identified as follows: [lists of specific rivers, creeks, and watersheds (or portions thereof) for three river
 basins]".

 Example 2:   "Wetland composition and distribution issimilarto that found in the main basin [literature
 citation].  Unlike the main basin, larger areas of intertidal emergent habitat are evident particularly in
 [identified embayments]. These wetlands are characterized as excellent fish and invertebrate habitats
 noted for high productivity and value [literature citation]. Numerous freshwater, moderate gradient streams
 feed the [identified river  basin]. Most are typical of lowland drainages: sand/gravel substrates,  riffle/pool
 profiles, shallow depths, total lengths between 1-6 km, and high water quality; each highly conducive to
 productive anadromous fish habitat [literature citation]. Principal streams noted include:  [identified creeks]
 [referenced personal communication]."
juvenile forms are not included in this definition unless they also are used by adults for spawning; such
areas may qualify as feeding areas critical for maintenance of anadromous fish species (a separate MRS
sensitive environment). Note that state, Federal, commercial, or other hatcheries or aquaculture facilities
are not included and should be evaluated only under the human food chain threat. Statutory Authority:
Not statutorily defined.

Pathway Specific

              Air— General eligibility requirements apply.
              Soil exposure — Category is not evaluated.
              Surface water— General eligibility requirements apply.

STATE DESIGNATED AREAS FOR PROTECTION OF AQUATIC LIFE

General

       Navigable waters (as defined by the Clean Water Act) listed by a state as adequate, or
reasonably expected to be made adequate, to provide for the protection and  propagation of a balanced
population of shellfish, fish, and wildlife pursuant to section 305 of the Clean Water Act. This designation
is based solely on the classification assigned to the water body in the Section 305(a) Report and updated
biennially in the Section 305(b) Report. The specific procedure for classifying these areas varies among
states. Note that in some states, waters designated for drinking water use also are considered to be
designated for protection of aquatic life and would be included in this category; in other states, waters
classified for drinking water use are not automatically considered to be designated for the protection of
aquatic life and would not be included in this category. The specific classification scheme must be
determined on a state-by-state basis. Statutory Authority: sections 305(a) and (b) of the Clean Water Act
(33U.S.C. §1315).


                                            A-17                                    Section A.2

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Pathway Specific

              Air— General eligibility requirements apply.
              Soil exposure — Category is not evaluated.
              Surface water— General eligibility requirements apply.

STATE DESIGNATED NATURAL AREAS

General

       Areas designated by a state Governor, administrative agency, or legislature as a natural area
based on their unique aesthetic, ecological, or recreational values. Statutory Authority: State laws.

Pathway Specific

              Air— General eligibility requirements apply.
              Soil exposure — General eligibility requirements apply.
              Surface water— General eligibility requirements apply.

STATE DESIGNATED SCENIC OR WILD RIVER

General

       Rivers or segments of rivers (and the related  adjacent land area, if so designated) that are
designated as wild and/or scenic by a state Governor, administrative agency, or legislature under an
appropriate state law. Segments generally are designated as wild or scenic because of their degree of
free-flow, lack of development, and the outstanding scenic, natural and cultural characteristics  of the
segment and their surrounding environments; however, specific criteria may vary among states. Note
that state-designated wild or scenic rivers that have been included in the National Wild and Scenic
Rivers System are considered Federal Wild and  Scenic Rivers or National River Reaches Designated as
Recreational for MRS purposes (see subsections above, Federal Designated Scenic or Wild River and
National River Reach Designated as Recreational). SeeHighlight A-4 for a summary of criteria for
determining the appropriate MRS sensitive environments category for a wild or scenic river. Statutory
Authority:  State laws.

Pathway Specific

              Air— General eligibility requirements apply.
              Soil exposure — Category is not evaluated.
              Surface water— General eligibility requirements apply.

STATE LAND DESIGNATED FOR WILDLIFE OR GAME MANAGEMENT

General

       Land set aside or managed for the propagation and maintenance of wildlife or game under some
type of state sponsorship and approval. Some of these areas are open on a limited basis to hunting
and/or fishing, but this is not an eligibility criterion. As a general rule, eligible areas would include any
land for which use for wildlife or game management can be altered only with state approval, and only
under certain circumstances. Eligible areas include (but are not limited to) lands owned by a state and
designated by the state Governor, legislature, or appropriate administrative agency for the propagation
and maintenance of wildlife or game; lands leased  by the state; privately owned lands maintained for
eventual sale to the state; and state-owned lands that are privately managed. All Pittman-Robertson
Preserves and some Nature Conservancy lands  are eligible. Statutory Authority: State laws.
Section A.2                                    A-18

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Pathway Specific

              Air— General eligibility requirements apply.
              Soil exposure —  General eligibility requirements apply.
              Surface water—  General eligibility requirements apply.

TERRESTRIAL AREAS UTILIZED FOR BREEDING BY LARGE OR DENSE AGGREGATIONS OF
ANIMALS

General

       Terrestrial areas used for intensive or concentrated breeding by terrestrial vertebrate species.
Eligible areas differ by pathway (see below). Evidence for the existence of this sensitive environment will
be strengthened if the breeding habitat requirements (e.g., substrate, vegetation) of the species of
concern is defined, suitable breeding habitat within the TDL is delineated, and it can be shown that the
species typically nests or breeds in large colonies or dense aggregations. Examples of areas that may
meet these criteria include heron or cormorant rookeries, beaches used for rearing young by seals or sea
lions, and sand cliffs used by bank swallows. Only the areas utilized for breeding (i.e., nesting or brood
rearing areas) meet this definition for MRS purposes; areas used solely for feeding (e.g.,  open fields near
nest sites) are excluded. Note that eligible areas include areas used for breeding by seals, sea lions,
turtles, and other vertebrates that spend most of their time in the water but breed on  land. However,
ponds and other surface water bodies used for breeding by amphibians and other aquatic vertebrate
species with semi-aquatic habits do not meet this definition because these are not terrestrial areas. Note
also that  it is not necessary to demonstrate that these areas are  critical for the maintenance  of the
species of concern. Statutory Authority: Not statutorily defined.

Pathway Specific

              Air — Eligible areas are limited to terrestrial areas that are at least partially  within the
              TDL and are used by terrestrial vertebrate species. Eligible areas for this pathway
              include areas used for breeding by terrestrial vertebrates with semi-aquatic habits.

              Soil exposure —  Eligible areas are limited to terrestrial areas that are at least partially
              within the area of observed contamination and are used for breeding by vertebrate
              species. Eligible areas include areas used for breeding by terrestrial vertebrates with
              semi-aquatic habits.

              Surface water—  Eligible areas are limited to terrestrial areas that are  located along or
              contiguous to the hazardous substance migration path and are used for breeding by
              terrestrial vertebrate species with aquatic or semi-aquatic foraging habits (i.e., birds,
              mammals, or reptiles that consume fish or other aquatic organisms that inhabit or might
              inhabit the surface water bodies within the TDL). Such species generally correspond to
              those defined as "terrestrial vertebrates with semi-aquatic habits" (seeHighlightA-2).

UNIT OF COASTAL BARRIER RESOURCES SYSTEM

General

       Coastal barriers (e.g., bay barrier, tombolo, barrier spit, or barrier island) selected by the
Secretary of the Interior and designated by an act of Congress as a unit of the Coastal  Barrier Resources
System. Areas depicted as "otherwise protected" on the Coastal  Barrier Resources System maps do not
meet this definition for MRS purposes because they are not part  of the System (these are areas held for
conservation purposes under Federal, State, or local law, or by an organization primarily  for conservation
purposes). "Otherwise protected" areas may be eligible for evaluation as a separate sensitive
environment in the MRS if they meet the definition of undeveloped and partially developed


                                             A-19                                     Section A.2

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coastal barriers (see subsections above, Coastal Barrier— Partially Developed and Coastal Barrier —
Undeveloped). Maps that depict the Coastal Barrier Resources System are administered by USFWS.
Statutory Authority: Coastal Barrier Resources Act (16 U.S.C. § 3501 ,et seq.).

Pathway Specific

               Air—  General eligibility requirements apply.
               Soil exposure — Category is not evaluated.
               Surface water— General eligibility requirements apply.

WETLANDS

General

       Wetlands generally include swamps, marshes,  bogs, and similar areas. As defined in 40 CFR
230.3, wetlands are those areas that are inundated or saturated by surface or ground water at a
frequency and duration sufficient to support, and that under normal circumstances do support, a
prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands can be  natural or
man-made. Wetlands identified using other definitions (e.g., the Food Security Act of 1985, the wetlands
classification system of USFWS, the 1989 Federal Manual for Identifying  and Delineating Jurisdictional
Wetlands) are not eligible to be evaluated with the MRS unless they also  meet the 40 CFR 230.3
definition. A discussion of the wetland classification system used on National Wetlands  Inventory (NWI)
maps and its relationship to the 40  CFR 230.3 definition is provided below.

Pathway Specific

               Air—  General eligibility requirements apply.
               Soil exposure — Category is not evaluated.
               Surface water— General eligibility requirements apply.

Relationship between USFWS and 40 CFR 230.3 Wetland Definitions

       The MRS uses the following definition of wetlands (40 CFR 230.3): /Areas that are inundated or
saturated by surface or ground water at a frequency and duration sufficient to support, and that under
normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil
conditions. USFWS uses the following definition of wetlands (for NWI maps)- Lands that are transitional
between terrestrial and aquatic systems where the water table is usually at or near the surface or the
land is covered by shallow water, and have one of the following three attributes: at least periodically, the
land supports predominantly hydrophytes; the substrate is predominantly undrained hydric soil; and/or the
substrate is nonsoil and is saturated with water or is covered by shallow water at some time during the
growing season of each year.

       The primary difference between the  MRS and USFWS definitions is that under the MRS
definition, wetlands must, under normal circumstances, support a prevalence of rooted emergent
hydrophytes. Hydrophytes are a sufficient, but not necessary,  requirement for the USFWS definition.
Areas that under normal  circumstances do not support hydrophytes may be classified as a wetland by
USFWS,  but would not be classified as a wetland for MRS purposes.

       USFWS describes five categories of wetlands. Two of these fall within the MRS  definition of
wetlands:

               Areas with hydrophytes and hydric soils (e.g., marshes, swamps, and bogs); and

               Areas where hydrophytes have become established but hydric soils have not yet
               developed (e.g.,  margins of  impoundments or excavations).

Section A.2                                     A-20

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Three other categories do not meet the MRS definition of wetlands:

              Areas without hydrophytes but with hydric soils (e.g., flats where drastic fluctuation in
              water level, wave action, turbidity, or high concentration of salts may prevent the growth
              of hydrophytes);

              Areas with hydrophytes but without soils (e.g., seaweed-covered portions of rocky
              shores); and

              Areas without hydrophytes and soils (e.g., gravel beaches or rocky shores without
              vegetation).

       Deepwater habitats that support submerged aquatic vegetation (SAV) but not emergent
vegetation do not fall within either the MRS or the USFWS definition. Although SAV is hydrophytic, it is
not "vegetation typically adapted for life in saturated soil conditions" because substrates that support
SAV but not emergent vegetation are considered nonsoil.

       USFWS divides wetlands (and deepwater systems) into five categories based on salinity, tidal
influence, and wave action. Hydrophytes and hydric soils exist in each of these categories:

              The marine  system includes all wetlands that occur along the high energy coastline of
              the open ocean overlying the continental shelf. Salinities exceed 30 parts per thousand
              (ppt), with little or no dilution except near the mouths of estuaries.

              The estuarine system includes all wetlands in areas, partially enclosed by land, with
              open, partly obstructed, or sporadic access to marine waters. Salinities are 0.5 ppt or
              greater and fluctuate due to evaporation and mixing of fresh water and seawater.

              The riverine  system includes all wetlands within channels (i.e., open conduits which at
              least periodically contain  moving water or which form a connection between two bodies
              of standing water). The riverine system also includes wetlands dominated by trees,
              shrubs, persistent emergents, and emergent mosses or lichens; and wetlands in areas
              with water containing ocean derived salts  in concentrations exceeding 0.5 ppt.

              The lacustrine system includes all wetlands situated in topographic depressions or
              dammed river channels in areas where trees, shrubs, persistent emergents, and
              emergent mosses and lichens cover less than 30 percent of the total area. Lacustrine
              systems must be at least 8 hectares (ha) in size and  are subdivided into two zones:
              limnetic (all deepwater habitats),  and  littoral (areas from the shoreward boundary to a
              depth of 2 meters below low water or to the maximum extent of non-persistent
              emergents). All wetlands fall into the littoral zone.

              The palustrine system includes all non-tidal wetlands dominated by trees, shrubs,
              persistent emergents, emergent mosses and  lichens, and ail such wetlands that occur in
              tidal areas where the salinity due to ocean derived salts is less than 0.5 ppt. A wetland
              lacking  the above vegetation is also palustrine if: it is less than 8 ha in size;  it does not
              have an active wave-formed  or bedrock shoreline; water depth in the deepest part of the
              basin is less than 2 meters at low water; or salinity due to ocean derived salts is less
              than 0.5 ppt.

       Note that salinity category does not affect whether or not an area qualifies as a wetland under
either the MRS or the USFWS definition.

       Highlight A-8 divides wetland and deepwater categories defined on NWI maps into three
categories: those presumed to be eligible for MRS purposes, those that may under certain


                                             A-21                                     Section A.2

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circumstances be eligible for MRS purposes, and those that generally will not be eligible for MRS
purposes.
HIGHLIGHT A-8
COMPARISON OF HRS WETLANDS DEFINITION AND WETLANDS





















CLASSIFICATION SYSTEM USED FOR NWI MAPS
Wetlands Category
on NWI Maps
Marine System
Subtidal
Rock Bottom
Unconsolidated Bottom
Aquatic Bed
Reef
Intertidal
Aquatic Bed
Reef
Rocky Shore
Unconsolidated Shore
Estuarine System
Subtidal
Rock Bottom
Unconsolidated Bottom
Aquatic Bed
Reef
Intertidal
Aquatic Bed
Reef
Streambed
Rocky Shore
Unconsolidated Shore
Emergent Wetland
Scrub-Shrub Wetland
Forested Wetland
Palustrine System
Rock Bottom
Unconsolidated Bottom
Aquatic Bed
Unconsolidated Shore
Moss-Lichen Wetland
Emergent Wetland
Scrub-Shrub Wetland
Forested Wetland
Eligible as HRS wetlands?
Yesa















/
/
/



/
/
/
/
Possibly b






/
/






/
/
/



/
/



Generally Not c

/
/
/
/

/
/


/
/
/
/

/
/




/

/



a Can be presumed to meet the 40 CFR 230.3 definition of a wetland.
b May meet the 40 CFR 230.3 definition of a wetland if emergent hydrophytes are present.
0 Generally will not meet the 40 CFR 230.3 definition of a wetland, except for some unique types of wetlands (e.g.
shoals or reefs).




















some
(continued on next page)
Section A.2
                                             A-22

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HIGHLIGHT A-8 (continued)
COMPARISON OF MRS WETLANDS DEFINITION AND WETLANDS























wetlands
CLASSIFICATION SYSTEM USED FOR NWI MAPS
Wetlands Category
on NWI Map
Riverine System
Tidal
Rock Bottom
Unconsolidated Bottom
Aquatic Bed
Streambed
Rocky Shore
Unconsolidated Shore
Emergent Wetland
Lower Perennial
Rock Bottom
Unconsolidated Bottom
Aquatic Bed
Rocky Shore
Unconsolidated Shore
Emergent Wetland
Upper Perennial
Rock Bottom
Unconsolidated Bottom
Aquatic Bed
Rocky Shore
Unconsolidated Shore
Intermittent
Stream Bed
Lacustrine System
Limnetic
Rock Bottom
Unconsolidated Bottom
Aquatic Bed
Littoral
Rock Bottom
Unconsolidated Bottom
Aquatic Bed
Rocky Shore
Unconsolidated Shore
Emergent Wetland
Eligible as MRS wetlands?
Yesa





/




/













/
Possibly b



/
/
/




/
/



/
/

/







/
/

Generally Not c

/
/
/



/
/
/

/
/
/



/
/
/

/
/
/

























a Can be presumed to meet the 40 CFR 230.3 definition of a wetland.
b May meet the 40 CFR 230.3 definition of a wetland if emergent hydrophytes are present.
c Generally will not meet the 40 CFR 230.3 definition of a wetland, except for some unique types of
(e.g., some shoals or reefs).
A-23
                                               Section A.2

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SECTION A.3
PROCESS FOR
IDENTIFYING
AND  DELINEATING
SENSITIVE ENVIRONMENTS
latjJfS^uu
      This section provides guidance for obtaining the information required to identify and delineate
sensitive environments evaluated in the MRS. The steps in this section are based on the definitions of
sensitive environments in Section A.2 and the data sources found in Section A.4.  This section divides
the MRS sensitive environment categories into three groups: those likely to be delineated on USGS
topographic maps, those likely to be delineated on specialized maps or in special documents, and those
that require professional judgement to identify and delineate. Each category requiring professional
judgement is followed by a stepwise approach to assist the scorer in identifying whether or not the
specific sensitive environment is at least partially within the TDL or area of observed contamination. The
steps presented for each sensitive environment category should not be viewed as a list of definitive
criteria, but rather are intended to guide professional judgment in identifying non-statutorily defined
sensitive environments. The definitions provided in Section A.2 and the information sources provided in
Section A.4 supplement the guidance provided in this section.

SENSITIVE ENVIRONMENTS LIKELY TO BE DELINEATED ON USGS
TOPOGRAPHIC  MAPS

      The following sensitive environments are likely to be identified and delineated on U.S.
Geological Survey (USGS) topographic maps:

            Designated Federal Wilderness Area
            National Lakeshore Recreational Area
            National Monument
            National or State Wildlife Refuge
            National Park
            National Preserve
            National Seashore Recreational Area
            State Lands Designated for Wildlife or Game Management (in some cases)
            Wetlands (in some cases).

      If site topographic maps are outdated, the scorer may need to check Federal Register notices
and other materials (e.g., state  publications) to update information.  A list of sources for updating
information on these sensitive environments is provided in Section A.4. In many cases, the level of
detail provided by USGS topographic maps in delineating the above sensitive environments will be
sufficient for MRS scoring (see discussions of scoring strategies in pathway-specific sections of this
document). In other cases, more specialized maps will be required.

SENSITIVE ENVIRONMENTS LIKELY TO BE DELINEATED ON SPECIALIZED
MAPS OR IN SPECIAL DOCUMENTS
      The sensitive environments listed below are likely to be delineated on specialized maps or
described in special documents, Most of the sensitive environments delineated on USGS topographic
                                       A-25
                                                                          Section A.3

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maps also are delineated on specialized maps; these specialized maps should be used if more precise
delineations are required.

              Administratively Proposed Federal Wilderness Area
              Areas Identified Under the Coastal Zone Management Act
              Critical Areas Identified Under the Clean Lakes Program
              Critical Habitat for Federal Designated Endangered or Threatened Species
              Federal Designated Scenic or Wild River
              Federal Land Designated for Protection of Natural Ecosystems
              Marine Sanctuary
              National River Reach Designated as Recreational
              Sensitive Areas Identified Under the  National Estuary Program or Near Coastal Waters
              Program
              State Designated Areas for Protection and Maintenance of Aquatic Life
              State Designated Natural Areas
              State Designated Scenic or Wild River
              State Land Designated for Wildlife or Game Management (in some cases)
              Unit of the Coastal  Barrier Resources System
              Wetlands (in some  cases).

       If needed, check Federal Register notices and other materials (e.g., state publications) to update
information about these sensitive environments. A list of specialized maps and other sources for
obtaining updated information is provided in Section A.4. Specialized maps may not be sufficient to
evaluate wetlands; professional judgment may also be required.

SENSITIVE ENVIRONMENTS THAT REQUIRE  PROFESSIONAL JUDGMENT
AND/OR SPECIFIC EXPERTISE TO  IDENTIFY AND DELINEATE

       The sensitive environments listed alphabetically below generally are not delineated on maps or
described in specialized  publications. Identifying and delineating these sensitive environments generally
require assistance from appropriate Federal, state, or local agencies  or recognized experts. It may be
necessary to meet with these individuals and/or provide them with maps and other site information.
Agencies designated as  CERCLA natural resource trustees (seeHigblight A-5, page A-12) and state or
local agencies that have statutory responsibility for or involvement in  management of sensitive
environment generally should be consulted (e.g., state fish and game departments). If the Superfund
remedial program has a biological technical assistance group (BTAG) in the Region, the BTAG
chairperson may be able to identify appropriate  agencies and/or individuals to contact. The Regional Site
Assessment Manager can provide the name and phone number of the BTAG chairperson.

COASTAL BARRIER - PARTIALLY DEVELOPED

(1)     Determine whether any coastal barriers (as defined in Section A.2) are at  least partially within the
       air and surface water pathway TDLs. A state coastal zone management agency, EPA's Near
       Coastal Waters program, or county real estate officials may be able to offer assistance in making
       this determination. If no such areas are found, stop; otherwise, proceed to Step (2).

(2)     Determine if any of the areas is a unit of the National Coastal Barrier Resources System. If so,
       the  area qualifies as a separate sensitive environment for MRS purposes and should  be
       evaluated based on that classification. If all areas in question are units of the  National Coastal
       Barrier Resources System,  stop; otherwise proceed to Step (3).
Section A.3                                   A-26

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(3)     Determine which of the areas meet the definitions of a partially developed coastal barrier or an
       undeveloped coastal barrier (as specified in Section A.2):

              The entire coastal barrier is undeveloped if it contains (on average) fewer than one
              man-made structure per 5 acres of fastland area.

              A portion of the coastal barrier is undeveloped if it has at least 1/4-mile of undeveloped
              shoreline on the shoreward side of the coastal barrier and the undeveloped area extends
              through the fastland from the beach to the associated landward aquatic habitat.

              A coastal barrier is partially developed if it contains (on average) one or more manmade
              structures per 5 acres of fastland, but no more than 50 percent of the fastland area is
              covered by one or more man-made structures per 5 acres of fastland area. A coastal
              barrier that is more than 50 percent developed is not eligible for evaluation as a partially
              developed coastal barrier.

(4)     Evaluate each of the qualifying areas as an undeveloped or partially developed coastal barrier. If
       the same coastal barrier has portions that qualify as both undeveloped and  partially developed,
       evaluate either the undeveloped  or partially developed portions, but not  both (i.e., do not score
       the same coastal barrier as both  undeveloped and partially developed).

COASTAL BARRIER - UNDEVELOPED

              See subsection above, Coastal Barrier — Partially Developed.

HABITAT KNOWN TO BE USED BY A FEDERAL DESIGNATED OR PROPOSED ENDANGERED OR
THREATENED SPECIES

(1)     Determine whether any of the species (as defined in Section  A.1) are  known to be present in
       and using suitable habitat within the TDLs (or areas of observed contamination) for the site.
       Contact a representative of an appropriate Federal, state, county, or local agency (e.g.,
       USFWS, NMFS, state fish and game department, state Natural Heritage program) or a
       recognized expert to help determine if suitable habitat for any of the species exists within the
       TDLs or areas of contamination and if the habitat is currently occupied and  used  by the
       species. It may be difficult to obtain information beyond the known presence of a species
       within a given area, distance ring, or surface water body. If it  is not possible to document the
       presence of one or more of the species within the TDLs (or areas of contamination), stop;
       otherwise, proceed to Step (2).

(2)     Document all  habitat known to be used  by each eligible species within the TDL. Appropriate
       documentation includes (but is not limited to):

                      A written or documented oral statement from  a representative of the appropriate
                      Federal, state, or local agency (or from a recognized expert) that establishes the
                      presence of the species within the TDLs or area of observed contamination; or

                      Any other evidence that documents the recent presence of the  species in
                      suitable habitat within the TDLs or areas of observed contamination (e.g., within
                      a 5-year period prior to MRS package preparation).

              Ensure that a habitat identified as used by a Federal  designated or  proposed endangered
              or threatened species (or a portion thereof) is not listed as a critical habitat for that
              species as defined  in Section A.2. If an area is a critical habitat for a Federal designated
              species, the area qualifies as a separate sensitive environment for MRS scoring and
              should be evaluated for that species based solely on that classification.


                                            A-27                                     Section A.3

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HABITAT KNOWN TO BE USED BY A SPECIES UNDER REVIEW AS TO ITS FEDERAL
ENDANGERED OR THREATENED STATUS

       See subsection above, Habitat Known to be Used by a Federal Designated or Proposed
       Endangered or Threatened Species.

HABITAT KNOWN TO BE USED BY A STATE DESIGNATED ENDANGERED OR THREATENED
SPECIES

       See subsection above, Habitat Known to be Used by a Federal Designated or Proposed
       Endangered or Threatened Species.

MIGRATORY PATHWAYS AND FEEDING AREAS CRITICAL FOR MAINTENANCE OF
ANADROMOUS FISH SPECIES WITHIN RIVER REACHES OR AREAS IN LAKES OR COASTAL
TIDAL WATERS IN WHICH THE FISH SPEND EXTENDED PERIODS OF TIME

(1)     Contact one or more of the following, provide them with the definitional criteria for these
       sensitive environment categories (i.e., as stated in HRS Table 4-23), and ask them to determine
       whether any surface water bodies within the TDLs-s meet one or all of the definitional criteria:

              Representatives of agencies designated as CERCLA natural resource trustees (see
              Highlight A-S),

              Representatives of state or local agencies that have statutory responsibility for or
              involvement in management of the area or types of species of concern (e.g., state fish
              and game departments), even if these agencies are not designated CERCLA natural
              resource trustees; and/or

              Recognized  experts familiar with the area or types of species of concern.

(2)     Request written documentation (on appropriate letterhead)  that the area of concern is a critical
       spawning area and some information about the species and habitat(s) of concern (e.g., some
       explanation as to why the habitat is critical). The documentation should be legally defensible for
       CERCLA damage assessment purposes. Examples of suitable evidence are provided in
       Highlights A-6 and A-7). If these individuals do not identify any qualifying areas, stop;
       otherwise, proceed to Step (3).

(3)     Evaluate each qualifying area identified as a critical spawning area, migratory pathway, or
       feeding area.

PARTICULAR AREAS, RELATIVELY SMALL IN SIZE, IMPORTANT TO MAINTENANCE OF UNIQUE
BIOTIC COMMUNITIES

(1)     Contact representatives from State Natural Heritage Programs, state natural resources agencies,
       and recognized experts to determine if any unique, rare, or otherwise ecologically valuable biotic
       areas (e.g., old growth areas, pine barrens, bogs) are located within the TDLS-s (or areas of
       observed contamination) for the site. If there are no such areas within the TDLS-s of the site,
       stop; otherwise, proceed to Step (2).

(2)     Determine if each area in question meets the definitional criteria as specified in Section A.2.
       Four types of areas generally will meet the following definitional criteria for this sensitive
       environment (note that other areas that do  not meet these criteria may be eligible):

             Areas with a high proportion of species with highly restrictive habitat requirements due to
              unusual natural biotic and/or abiotic conditions;

Section A.3                                   A-28

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              Isolated areas that may or may not have an unusual community structure per se, but are
              particularly important to the continued existence of their biotic communities because of
              their geographic isolation;

              Areas with a high proportion of locally endemic species because of a relatively long
              period of geographic isolation and/or are exceptional examples of "climax" communities
              because of minimal human disturbance; or

              Areas that are vital to a species for maintenance of a community.

SPAWNING AREAS CRITICAL FOR THE MAINTENANCE OF FISH/SHELLFISH SPECIES WITHIN
       RIVER, LAKE, OR COASTAL TIDAL WATERS

       See subsection  above, Migratory Pathways and Feeding Areas Critical for Maintenance of
       Anadromous Fish Species Within River Reaches or Areas in Lakes or Coastal Tidal Waters in
       which the Fish spend Extended Periods of Time.

TERRESTRIAL AREAS USED FOR BREEDING BY LARGE OR DENSE AGGREGATIONS OF
ANIMALS

(1)     Contact state fish and game officials, USFWS officials,  or recognized experts to determine
       whether any terrestrial species that normally breed in large or dense aggregations have been
       observed or are expected to br present within the air and surface water pathway TDLs or areas
       of observed contamination of the site.  If no such species have been observed or are expected
       to be present within the  TDL or area of observed contamination, stop; otherwise, proceed to Step
       (2).

(2)     Determine if each area in question meets the definitional criteria specified in Section A.2 and if
       such breeding occurs within that area. Support documentation may include defining the
       breeding habitat requirements of the species of concern and demonstrating that the species
       typically nests or breeds in large colonies  or dense aggregations. Additional pathway-specific
       criteria include:

              In the surface water pathway, eligible areas are limited to terrestrial areas that are used
              for  breeding by terrestrial vertebrate species with aquatic or semi-aquatic foraging habits
              (i.e., birds, mammals, or reptiles that consume fish or other aquatic organisms that
              inhabit or might  inhabit the surface water bodies within the TDL).  Such species generally
              correspond to those defined in Section A.2 as "terrestrial vertebrates with semi-aquatic
              habits".

              In the soil exposure pathway, eligible areas are limited to terrestrial areas that are at
              least partially on the area of observed contamination and  are used for breeding by
              terrestrial vertebrate species.

              In the air pathway, eligible areas are limited to terrestrial areas that are at least partially
              within the TDL and are used for breeding by terrestrial vertebrate species.

WETLANDS

(1)     Determine if there are any wetlands within the air or surface water pathway TDLs. As a starting
       point, use existing maps to delineate wetlands within the TDL. The preferred maps are the NWI
       Maps or state maps of equivalent quality.  If these maps are not available, use USGS
       topographic maps or Soil Conservation Service  (SCS) maps to initially screen wetlands
       locations.
                                            A-29                                     Section A.3

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(2)
       Some wetlands delineated on NWI maps do not meet the 40 CFR 230.3 wetlands
       definition required for MRS eligibility. Highlight A-9 provides a guide to which wetlands
       delineated on NWI maps definitely can, possibly can, and generally cannot br presumed
       to meet the 40 CFR 230.3 definition of a wetland.

       Most wetlands delineated on USGS topographic maps meet the 40 CFR 230.3 definition.
       Because these areas are mapped based largely on aerial photographs, wetlands less
       than 40 feet wide may not appear on the maps, and wetlands boundaries are relatively
       crude.

       Areas delineated as wetlands on SCS maps are based largely on the presence of hydric
       soils and may not meet the 40 CFR 230.3 definition.

If the NWI, USGS, SCS, and/or state maps are out of date, verify the areas delineated as
wetlands on maps (e.g., during site reconnaissance). For many wetland  areas, a photograph will
be sufficient documentation.  Some eligible wetlands may not appear on  any map. For areas not
delineated as a wetland on maps to be eligible for MRS evaluation as wetland, there should be
adequate documentation (e.g., photographs, identification by a recognized wetlands expert) that
the area meets the 40 CFR 230.3 definition. If there are no wetland areas within the TDLs; stop;
otherwise proceed to Step (3).
                                    HIGHLIGHT A-9
                  ELIGIBILITY OF WETLAND CATEGORIES ON NWI
                               MAPS FOR HRS SCORING
Wetlands Category on NWI
Maps
Emergent wetland
Scrub-shrub wetland
Forested wetland
Moss-lichen wetland
Streambed
Rocky Shore
Unconsolidated shore
Streambed (vegetated)
Unconsolidated Shore
(vegetated)
Unconsolidated bottom
Aquatic bed
Reef
Rock bottom
Eligible as HRS wetlands?
Yesa
/
/
/
/


Possibly"

/
/
/
/
/

Generally Not c


/
/
/
/
        a Can be presumed to meet the 40 CFR 230.3 definition of a wetland.
        b May meet the 40 CFR 230.3 definition of a wetland if emergent hydrophytes are present.
        c Generally will not meet the 40 CFR 230.3 definition of a wetland, except for some unique types of
 wetlands (e.g., some shoals or reefs).
Section A.3
                                           A-30

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(3)     If historical data (e.g., an old aerial photograph) document the presence of a wetland, and the SI
       shows that the wetland no longer exists, the area still may be eligible if the wetland was
       eliminated because of site-related activity. Conversely, the area generally will not be eligible if
       the wetland was eliminated for non-site-related reasons.

(4)     Under certain circumstances, surface impoundments that meet the 40 CFR 230.3 definition of a
       wetland may be considered  wetlands for MRS purposes.

              Surface impoundments constructed in an area that was previously occupied by a wetland
              generally are eligible (e.g., if a natural wetland was used as a surface impoundment).

              Surface impoundments that have inadvertently become wetlands may be eligible on a
              case-by-case basis  (e.g., a surface impoundment that has become a wetland due to poor
              waste management  practices may be eligible on a case-by-case basis).

              Surface impoundments created solely as waste management units generally are not
              eligible. However, surface impoundments created both as waste management units and
              as wetland mitigation areas may be eligible on  a case- by-case basis.

              Surface impoundments created in an area that originally was non-wetland but has
              become a wetland area due to site- or non-site related activities (e.g., altered streamflow
              patterns) may be eligible on a case-by-case basis.

(5)     Evaluate each qualifying wetland based on linear frontage or perimeter as specified in Section
       8.16 and/or Section 9.6.

(6)     If the targets score for wetlands is critical for Nation Priorities List (NPL) listing (i.e., the site
       would not score above 28.50 unless the wetland areas are scored), there  should be adequate
       documentation that the presumed wetlands meet the 40 CFR 230.3 definition of a wetland.
       Delineation by a recognized wetlands expert may be necessary.
                                             A-31                                      Section A.3

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luuuJSSuu
SECTION A.4
SOURCES OF
INFORMATION
FOR IDENTIFYING
SENSITIVE ENVIRONMENTS
       This section provides sources of information for identifying and delineating wetlands and all
sensitive environments listed in MRS Tables 4-23 and 5-5. Many MRS sensitive environments are
identified and delineated with readily available materials (e.g., maps or U.S. Environmental Protection
Agency (EPA) regional site files); however, more in-depth investigation may be necessary to determine
whether they are present within the TDLs or areas of observed contamination for the site. If an area
within the TDL could be a sensitive environment, identify whether it is an MRS sensitive environment and
document the point value rating into which the area could be classified.

       This section provides names of maps and other documents where sensitive environments are
likely to be delineated, and appropriate contacts for additional information. The EPA regional office is
encouraged  to develop and maintain a library of all relevant documents  listed in this section. The
National Wildlife Federation's Conservation Directory, which is revised annually, is a valuable reference
that lists governmental and nongovernmental organizations and personnel engaged in conservation work
at state, national, and  international levels. The MRS sensitive environments categories can be divided
into three groups:

             Those likely to be delineated on USGS topographic maps. Many categories of sensitive
             environments are delineated on USGS topographic maps. However, if site topographic
             maps  are out of date, it may be necessary to check Federal Register notices and other
             materials to obtain updated information. In many cases,  the level of detail provided by
             USGS topographic maps will be sufficient for MRS purposes. In some cases, more
             specialized maps (available from the appropriate administering agency) or professional
             judgment (e.g., for wetlands) will be required. USGS topographic maps are available
             from USGS Earth Science Information Centers (see Highlight A-10), most outdoor sport
             stores, and local outfitters. Categories of sensitive environments in this group include:

             —     Designated Federal Wilderness Area
             —     National Lakeshore Recreational Area
             —     National Monument
             —     National or State Wildlife Refuge
             —     National Park
             —     National Preserve
             —     National Seashore Recreational Area
             —     State Lands Designated for Wildlife or Game Management (in some cases)
             —     Wetlands (in some cases).

             Those requiring special maps or charts from specific agencies and other sources.
             Several categories of sensitive environments are delineated  on specialized maps, charts
             or other documents available from various Federal and state agencies. Note that most of
             the sensitive environments delineated on USGS topographic maps also


                                         A-33                                  Section A.4

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              are delineated on specialized maps; these specialized maps should be used if more
              precise delineations are required. Beneath each of the following sensitive environments,
              the name and source of the specific map, chart, or document is provided along with a
              contact in case additional information is needed. Categories of sensitive environments in
              this group include:

              —     Administratively Proposed Federal Wilderness Area
              —     Areas  Identified Under the Coastal Zone Management Act
              —     Critical Areas Identified Under the Clean Lakes Program
              —     Critical Habitat  for Federal Designated Endangered or Threatened Species
              —     Federal Designated Scenic or Wild River
              —     Federal Land Designated for Protection of Natural Ecosystems
              —     Marine Sanctuary National River Reach Designated as Recreational
              —     Sensitive Areas Identified Under the National Estuary Program or Near Coastal
                     Waters Program
              —     State Designated Areas for Protection and Maintenance of Aquatic Life
              —     State Designated Natural Areas
              —     State Designated Scenic or Wild River
              —     State Land Designated for Wildlife or Game Management (in some cases)
              —     Unit of the Coastal Barrier Resources  System
              —     Wetlands (in some cases).

              Those that may require professional judgment to identify and delineate.  Several
              categories of sensitive environments generally are not delineated on maps or otherwise
              described  in specialized publications. Identifying and delineating these sensitive
              environments generally will require professional judgment. The assistance of appropriate
              Federal, state, or local agencies or experts in identifying these sensitive environments is
              encouraged, The scorer should try to obtain copies of any published information that
              helps to establish the area as a sensitive environment and/or delineate its boundaries. If
              possible, obtain a written statement from a responsible agency official or individual
              verifying the existence and boundaries of the sensitive environments. Sources of
              information provided below are not exhaustive and focus primarily on the national level.
              EPA regional offices are encouraged to develop lists of sources at a regional, state,
              and/or local level. Categories of sensitive environments in this group include:

              —     Coastal Barrier — Partially Developed

              —     Coastal Barrier — Undeveloped

              —     Habitat Known to  be Used by a Federal Designated or Proposed Endangered or
                     Threatened  Species

              —     Habitat Known to  be Used by a Species under Review as to its Federal
                     Endangered or Threatened Status

              —     Habitat Known to  be Used by a State Designated Endangered or Threatened
                     Species

              —     Migratory Pathways and Feeding Areas Critical for Maintenance of Anadromous
                     Fish Species within River Reaches or Areas in Lakes or Coastal Tidal Waters in
                     which the Fish Spend Extended Periods of Time

              —     Particular Areas, Relatively Small in Size, Important to Maintenance  of Unique
                     Biotic Communities

Section A.4                                    A-34

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              —     Spawning Areas Critical for the Maintenance of Fish/Shellfish Species Within
                     River, Lake, or Coastal Tidal Waters

              —     Terrestrial Areas Used for Breeding by Large or Dense Aggregations of Animals

              —     Wetlands.

ADMINISTRATIVELY PROPOSED FEDERAL WILDERNESS AREA

       Federal Wilderness Areas may be proposed by BLM, USFS, NPS, or USFWS.

(1)     The boundaries of the proposed wilderness area should  be available in a public docket or
       Federal Register notice. Contact the appropriate BLM, USFS, NPS, or USFWS regional office
       listed in Highlights A-11 through A-14io obtain information on proposed Federal Wilderness
       Areas.

AREAS IDENTIFIED UNDER THE COASTAL ZONE MANAGEMENT ACT

       Areas designated under the Coastal Zone Management Act include:  those nominated, proposed,
and designated as National Estuarine Research Reserves by NOAA, and those designated as being of
particular concern in State Coastal Zone Management Plans that have been approved by NOAA.

(2)     Highlight A-15 lists all proposed and  designated National Estuarine Research Reserves as of
       September, 1991. Latitudes and longitudes of these areas are available from NOAA's Marine
       and Estuarine Management Division, Office of Ocean and Coastal Resource Management,
       NOS/NOAA, 1825 Connecticut Ave., Washington, DC 20235; (202) 606-4126.

(3)     A list of locations for areas nominated for the National Estuarine Research Reserve System and
       copies of State Coastal  Zone Management Plans that delineate other areas designated as being
       of particular concern are available from the appropriate state coastal zone management agency
       or NOAA's Office of Ocean and Coastal Resource Management at (202) 606-4126.

(4)     Many eligible coastal areas are delineated on USGS topographic maps or NOAA nautical charts.
       USGS topographic maps can be obtained from one of the Earth Science Information Centers
       listed in Highlight A-10, most outdoor sport stores, and local outfitters. NOAA nautical charts
       can be obtained from NOAA's Document Distribution Office at (301) 436-6990 and from various
       commercial stores specializing in marine recreation (e.g., boating, fishing).

(5)     Other potential sources of information on estuaries and near coastal waters include EPA's Office
       of Marine and Estuarine Protection at (202) 260-7166 and Sea Grant program offices (located at
       major universities in coastal areas).

(6)     If further assistance is needed to delineate an area identified under the Coastal Zone
       Management Act, contact the appropriate state coastal zone management agency or the
       appropriate regional office of the National Estuarine Research Reserve System listed in
       Highlight A-15.

COASTAL BARRIER — PARTIALLY DEVELOPED

       Undeveloped and partially developed  coastal barriers are generally administered by a state
coastal zone management agency or by EPA's Near Coastal Waters Program.
                                           A-35                                   Section A.4

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(1)     If the coastal barrier is publicly owned and administered by a state coastal zone management
       agency or a Federal agency, contact the appropriate agency for assistance in determining and
       uses on the coastal barrier.

(2)     Other sources of information for undeveloped and partially developed coastal barrier areas
       include aerial photographs, flood hurricane insurance maps, developers, real estate agents, and
       planning commissions. Alternatively, the regional contacts for the Near Coastal Waters Program
       (Highlight A-16) may be able to provide assistance in  determining land uses on the particular
       coastal barrier.

COASTAL BARRIER — UNDEVELOPED

       See subsection above, Coastal Barrier — Partially Developed.

CRITICAL AREAS IDENTIFIED  UNDER THE CLEAN LAKES PROGRAM

       The Clean Lakes Program is administered by state water quality and natural resource agencies
and receives funding from EPA.

(1)     The Clean Lakes Program Data Table lists latitudes and longitudes for all elements of the Clean
       Lakes Program. Contact EPA's Office of Water Regulations and Standards (OWRS) at (202)
       260-5404 for a copy of this table.

(2)     Many eligible areas are delineated on USGS topographic maps. They can be obtained from one
       of the Earth Science Information Centers listed \r\HighlightA-10, most outdoor sport stores,
       and local outfitters.

(3)     Further assistance in delineating a given area can be obtained from the Clean Lakes Program
       Regional contacts (Highlight A-17), EPA's OWRS at (202) 260-5404, or the appropriate state
       water quality/natural resources agency.

CRITICAL HABITAT FOR FEDERAL DESIGNATED ENDANGERED OR THREATENED SPECIES

       Critical habitat has not been designated  for all endangered or threatened species. Although
USFWS and NMFS can still designate critical habitat, in  recent years they have been reluctant to do so
because pinpointing specific habitats in public documents can pose a danger for the species of concern
(e.g., from poachers). Only those areas listed in  50 CFR 17.95 (critical habitats for fish and wildlife
species), 50 CFR 17.96 (critical habitat for plant  species), or aFederal Register notice, are designated
critical habitat. Areas proposed as critical habitats are not evaluated in the MRS.

(1)     All critical habitat for Federal endangered or threatened species are identified  in  50 CFR 17.95
       and 50 CFR 17.96 in the form of maps and/or detailed descriptions.

(2)     If further assistance is needed to delineate a critical habitat, contact the appropriate USFWS
       regional office listed in Highlight A-12.

DESIGNATED FEDERAL WILDERNESS AREA

       A designated Federal Wilderness Area may be administered  by USFWS, BLM, USFS, or NPS.

(1)     The Wilderness Society  publishes  a map entitled The National Wilderness Preservation System,
       1964-1989 which locates all Federal Wilderness Areas designated before 1989. Contact the
       Wilderness Society at (202) 842-3400 to obtain a current  listing of all designated Federal
       Wilderness Areas.
Section A.4                                   A-36

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(2)     Federal Wilderness Areas should be delineated on USGS topographic maps of the area. In most
       cases, this delineation will be adequate for MRS purposes.

(3)     If a Federal Wilderness Area is not identified or adequately delineated on USGS topographic
       maps, contact the appropriate regional office of the appropriate administering agency listed in
       Highlights A-11 through A-14.

FEDERAL DESIGNATED SCENIC OR WILD RIVER

       Rivers or segments of rivers that are designated asNational Wild and Scenic Rivers are
administered by either a Federal agency (i.e., NPS, USFWS, USFS, or BLM), a state agency, or a
Native American nation.

(1)     All Federal designated scenic or wild rivers are delineated on a map entitled,/Vaf;ona/ Wild and
       Scenic Rivers System, Map Number 38077-BQ-NA-05M-00, December 1990. A listing of each
       unit, along with the name and address of the administering agency, is included with the map.
       This map can be obtained from the USGS Earth Science Information Centers listed \r\Highlight
       A-10.

(2)     NPS maintains a computerized database of information for each unit of the National Wild and
       Scenic River System. Information includes: the name of the unit, statutory or other authority for
       inclusion in the system, administering agency, total number of miles, and number of miles
       designated as wild, scenic, or recreational. Contact NPS's Division of Park Planning and
       Protection at (202) 208-4290 for this listing.

(3)     The Wild and Scenic Rivers Act identifies each river or river segment as wild, scenic, or
       recreational.  Contact NPS's Division of Park Planning and Protection at (202) 208-4290 to obtain
       a copy of the act.

(4)     If additional information is needed for a particular river segment, contact the appropriate BLM,
       USFS, NPS,  or USFWS regional office listed in Highlights A-11 through A-14.

(5)     River reaches designated under the Clean Water Act and identified in STORET are not eligible
       for MRS evaluation.

FEDERAL LAND DESIGNATED FOR THE PROTECTION OF NATURAL ECOSYSTEMS

       These areas  are usually administered by BLM or USFS.

(1)     Resource Management Plan (or other similar document)  published by BLM or USFS will identify
       areas designated for the protection of natural ecosystems in Resource Areas administered by
       those agencies. Resource Management Plans provide maps and latitude and  longitude for
       delineating these areas (note that prior to 1980 these documents were known as Management
       Framework Plans and provided less complete  environmental daia).HighlightA-13 or A-14 lists
       BI-M and USFS regional offices that can supply most Resource Management Plans.

(2)     EIS documents delineating public lands designated as Wildlife Mitigation Areas can be obtained
       by contacting the appropriate BLM or USFS regional office.

(3)     If an area designated for the protection of natural ecosystems is not identified or adequately
       delineated in the Resource Management Plan, contact the appropriate BLM or USFS regional
       office. If the area is managed by another Federal agency (e.g., BIA, MMS, OSM), contact the
       appropriate agency for copies of the appropriate Resource Management  Plan(s) or EIS(s).
                                           A-37                                    Section A.4

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HABITAT KNOWN TO BE USED BY FEDERAL DESIGNATED OR PROPOSED ENDANGERED OR
THREATENED SPECIES

       Endangered or threatened fish, wildlife, and plant species fall under the jurisdiction of USFWS.
Endangered or threatened marine animals (e.g., marine mammals, sea turtles) fall under the jurisdiction
ofNMFS.

(1)     All Federal designated endangered or threatened species are listed in 50 CFR 17.11 (fauna) and
       17.12 (flora) or in a Federal Register notice. Species proposed by the Secretary of the Interior for
       designation as Federal endangered or threatened species are published in thfederal Register.
       To obtain current lists of designated  and proposed Federal endangered or threatened species,
       contact the appropriate USFWS regional office listed \r\HighlightA-12 or NMFS's Office of
       Protected Resources at (301) 427-2322.

(2)     A number of sources can provide assistance in determining whether habitat known to be used by
       any of the species identified in Step (1) is within the TDLs, They include: state fish and game or
       wildlife, natural resource, or environmental conservation agency, the state Natural Heritage
       program, other local or regional experts (e.g., faculty members at a nearby university, members
       of the local Audubon society), the appropriate USFWS regional office and/or NMFS at (301)
       427-2322. If the Superfund remedial program has a BTAG in the region, the BTAG chairperson
       may be able to direct you to the appropriate agencies and individuals. Contact the regional Site
       Assessment Manager to obtain the name and phone number of the BTAG chairperson.

HABITAT KNOWN TO BE USED BY SPECIES UNDER REVIEW AS  TO ITS  FEDERAL
ENDANGERED OR THREATENED STATUS

(1)     Plant and animal species under review as to their Federal endangered or threatened status are
       listed in a Comprehensive Notice of Review, published biennially in the Federal Register by
       USFWS. Marine animals under review as to their Federal endangered or threatened status are
       listed periodically in a Candidate Species List, published in theFectera/ Register by NOAA. To
       obtain current lists of species under review as to their endangered or threatened status, contact
       the appropriate USFWS regional office or NMFS's Office of Protected  Resources at (301)
       427-2322.

(2)     A number of sources can provide assistance in determining whether habitat known to be used by
       any of the species identified in Step (1) is within the TDLs. They include:  state fish and game or
       wildlife, natural resource, or environmental conservation agency, the state Natural Heritage
       program, other local or regional experts (e.g., faculty members at a nearby university, members
       of the local Audubon society), the appropriate USFWS regional office and/or NMFS at (301)
       427-2322. If the Superfund remedial program has a BTAG in the region, the BTAG chairperson
       may be able to direct you to the appropriate agencies and individuals. Contact the regional Site
       Assessment Manager to obtain the name and phone number of the BTAG chairperson.

HABITAT KNOWN TO BE USED BY STATE DESIGNATED ENDANGERED OR THREATENED
SPECIES

       A number of agencies can provide assistance to identify and delineate this sensitive environment
category. They include: the state fish and game or wildlife, natural resource, or environmental
conservation agency, other local or regional  experts (e.g., faculty members at a nearby  university,
members of the local Audubon society), and/or the appropriate USFWS regional office.  Note that the
USFWS Small Wetlands Acquisition Program protects prairie potholes and other small wetlands
important for waterfowl production. If the Superfund remedial program has a BTAG in the region, the
BTAG chairperson may be able to direct you to the appropriate agencies and individuals.
Section A.4                                   A-38

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Contact the regional Site Assessment Manager to obtain the name and phone number of the BTAG
chairperson.

MARINE SANCTUARY

       These areas are administered by NOAA.

(1)     NOAA has mapped the general locations of National Marine Sanctuaries. Contact NOAA's Office
       of Ocean and Coastal Resource Management at (202) 606-4126 fora copy of this map.
       Highlight A-18 provides a listing of the nautical chart numbers of all of the National Marine
       Sanctuaries.

(2)     National Marine Sanctuaries will be delineated on the appropriate nautical chart(s) available from
       the NOAA's Document Distribution Office at (301) 436-6990 and from various commercial stores
       specializing in marine recreation (e.g., boating, fishing).

(3)     If further information is needed to delineate a National Marine Sanctuary, contact NOAA's Office
       of Ocean and Coastal Resource Management at (202) 606-4126.

MIGRATORY PATHWAYS AND FEEDING AREAS CRITICAL FOR MAINTENANCE OF
ANADROMOUS FISH SPECIES WITHIN RIVER REACHES OR AREAS IN LAKES OR COASTAL
TIDAL WATERS IN WHICH THE FISH SPEND EXTENDED PERIODS OF TIME

       See subsection above, Habitat Known to be used by State Designated Endangered or
Threatened Species.

NATIONAL LAKESHORE RECREATIONAL AREA

       These areas are administered by the NPS.

(1)     The boundaries of these sensitive environments generally are delineated on USGS topographic
       maps. In most cases, this delineation will be adequate for MRS purposes.

(2)     If the sensitive environment is not identified or adequately delineated on USGS topographic
       maps, contact the appropriate NPS regional office listed \r\HighlightA-11.

(3)     NPS  maintains a computerized database that lists all lands under its jurisdiction. Contact NPS at
       (202) 343-7014 to obtain a copy.

NATIONAL MONUMENT

       See subsection above, National  Lakeshore Recreational Area.

NATIONAL OR STATE WILDLIFE REFUGE

       National Wildlife Refuges are administered by the USFWS. State wildlife refuges generally are
administered by a state fish and game or wildlife management agency.

(1)     All lands under USFWS jurisdiction, including national wildlife refuges, are identified in the
       Annual Report of Lands Under Control of the USFWS. Contact the USFWS Division of Realty at
       (703) 358-1816 to obtain a copy of the report. Lists of state wildlife refuges should be available
       from the appropriate fish and game or wildlife management agency.

(2)     National and state wildlife refuges generally are delineated on USGS topographic maps. State
       wildlife refuges also may be delineated on some official state highway maps. In most cases, this
       delineation will be adequate for MRS purposes.


                                          A-39                                   Section A.4

-------
(3)     If a wildlife refuge is not identified or adequately delineated on USGS topographic maps or other
       maps, contact the appropriate USFWS regional office listed \r\HighlightA-12 or the appropriate
       state fish and game or wildlife management agency.

NATIONAL PARK

       See subsection above, National Lakeshore Recreational Area.

NATIONAL PRESERVE

       See subsection above, National Lakeshore Recreational Area.

NATIONAL RIVER REACH DESIGNATED AS RECREATIONAL

       See subsection above, Federal Designated Scenic or Wild River.

NATIONAL SEASHORE RECREATIONAL AREA

       See subsection above, National Lakeshore Recreational Area.

PARTICULAR AREAS, RELATIVELY SMALL IN SIZE, IMPORTANT TO MAINTENANCE OF UNIQUE
BIOTIC COMMUNITIES

       See subsection above, Habitat Known to be used by State Designated Endangered or
Threatened Species.

SENSITIVE AREAS IDENTIFIED UNDER THE NATIONAL ESTUARY PROGRAM OR NEAR
COASTAL WATERS PROGRAM

       This sensitive environment category includes areas identified in both the National Estuary
Program and the Near Coastal Waters Program.  Both programs are administered by EPA.

(1)     Highlight A-19 identifies the components of the National Estuary Program for each EPA region.
       Contact the appropriate office to delineate the estuary program component in question.

(2)     Highlight A-16 lists the EPA Regional contacts for the Near Coastal Waters Program. Contact
       the appropriate office to delineate sensitive areas identified under the Near Coastal Waters
       Program. (Note that as of December 1991, no areas within the Near Coastal Waters Program
       had been designated as sensitive areas.)

(3)     Other potential sources of information on estuaries and near coastal waters include EPA's Office
       of Marine and Estuarine Protection at  (202) 260-7166 and Sea Grant program offices  (located at
       major universities In coastal areas).

SPAWNING AREAS CRITICAL FOR THE MAINTENANCE OF FISH/SHELLFISH SPECIES WITHIN
RIVER, LAKE, OR COASTAL TIDAL WATERS

       See subsection above, Habitat Known to be used by State Designated Endangered or
Threatened Species.

STATE DESIGNATED AREAS FOR PROTECTION OF AQUATIC LIFE

       These areas generally are administered by a state environmental protection or water quality
agency.


Section A.4                                  A-40

-------
(1)     Locations and boundaries of these areas can be found in the Clean Water Act Section 305(a)
       Report filed by the state, and is updated biennially with Section 305(b) Reports filed with EPA.

(2)     Copies of these reports can be obtained from the state environmental protection or water quality
       agency, the appropriate EPA regional office listed \r\HighlightA-20, or in the Environmental
       Reporter (under state regulations).

STATE DESIGNATED NATURAL AREAS

       These areas generally are administered by a state natural resources or land management
agency.

(1)     If available, obtain copies of any relevant documents (e.g., maps or state regulatory codes)
       delineating the designated  natural area.

(2)     If no official maps or documents are available, request a signed statement from a responsible
       official of the appropriate state natural resources or land management agency to document the
       boundaries of state designated natural areas within the TDLs of the site.

STATE DESIGNATED SCENIC OR WILD RIVER

       These areas generally are administered by a state park service or natural resources agency.

(1)     Maps or other documents that specify river reaches designated as state scenic or wild rivers may
       be available from a state park service, state natural resources agency or local outfitters.

(2)     Contact NPS's Division of Recreation Resources Assistance, Washington, D.C. at (202) 343-
       3780 to obtain information on state systems.

(3)     If no official maps or documents are available, request a signed statement from a responsible
       official of the appropriate state park service or natural resources agency to document the
       boundaries of state designated scenic or wild rivers within the TDLs of the site.

STATE LAND DESIGNATED FOR WILDLIFE OR GAME MANAGEMENT

       Some state lands designated for wildlife or game management are delineated on  USGS maps.
These lands generally are administered by a state fish and game or wildlife management agency.

(1)     Lists of state wildlife or game management areas should be available from the appropriate fish
       and game or wildlife management agency.

(2)     In some cases, state lands designated for wildlife and game  management will be delineated on
       USGS topographic maps.

(3)     If an area is not identified or adequately delineated on USGS maps, contact the appropriate state
       fish and game or wildlife management agency.

TERRESTRIAL AREAS UTILIZED FOR BREEDING BY LARGE OR DENSE AGGREGATIONS OF
ANIMALS

       See subsection above, Habitat Known to be used by State Designated Endangered or
Threatened Species.
                                           A-41                                    Section A.4

-------
UNIT OF COASTAL BARRIER RESOURCES SYSTEM

       The Coastal Barrier Resources System is administered by state coastal zone management
agencies; maps that depict the system are maintained by USFWS.

(1)     All units of the Coastal Barrier Resources System are listed in Part VI of the June 6, 1991
       Federal Register, which contains an index to the map series entitled Coastal Barrier Resources
       System, numbered A01 through T12 (excluding maps T02 and T03), and the maps designated
       T02A and T03A.

(2)     Using the index referenced in Step (1), obtain the appropriate map from the USGS Book Sales
       Office at (303) 236-7476, or order them using the order form provided in theFectera/ Register
       notice.  Alternatively, maps covering a particular state are available for inspection at selected
       regional and field USFWS offices listed in the Federal Register notice and at the state coastal
       zone management agency.

(3)     After May 15, 1992, no units will be added to the Coastal Barrier Resource System; however,
       individual units may change in size or location due to natural forces (e.g. wave action). If any
       major natural changes have occurred in the coastal barrier since the map was published, contact
       the state coastal zone management agency or USFWS.

WETLANDS

       The level of documentation required for identifying and delineating wetlands will vary among
sites (see Sections  8.17, 9.6,  and A.3 for guidance in determining required level of documentation). In
many cases, wetlands delineation provided by maps may be sufficient for MRS purposes.

(1)     The preferred maps are the NWI Maps or state maps of equivalent quality (e.g., Wisconsin).
       NWI maps are available from USGS Earth Science  Information Centers listed in Highlight A-10.
       The availability of state maps must be determined on a state-by-state basis. Note that wetlands
       identified on these maps may not meet the MRS definitional criteria for a wetland.

(2)     USGS topographic maps or wetlands maps  provided by the SCS can be used to approximate
       wetland boundaries. USGS topographic maps are available from USGS Earth Science
       Information Centers (see Highlight A-10), most outdoor sport stores, and local outfitters. SCS
       maps are available from each state office of the SCS. Note that not all areas listed as wetlands
       on these maps meet the MRS definitional criteria for a wetland. Note also that SCS maps often
       err on the side of listing areas as wetlands that are  not actually wetlands.

(3)     Other wetlands maps can be used to verify wetlands boundaries. Again, note that wetlands
       identified on these maps may not meet the MRS definitional criteria for a wetland.

       —     The USFWS Small Wetlands Acquisition Program protects prairie potholes and other
              small wetlands important for waterfowl production and may have maps.

       —     USGS has computerized maps delineating wetlands in Alabama, Florida, North Carolina,
              and Texas.

       —     BIA has delineated 400,000 acres of wetlands on Native American reservations in
              Minnesota and Wisconsin.

       —      Wetlands maps are included in North American Waterfowl Management Plans.

       —     Other contacts include:  the Isaak Walton League, Ducks Unlimited, Trout Unlimited, and
              The Wilderness Society.


Section A.4                                    A-42

-------
(4)     If an even greater level of detail is required to verify the presence of a wetland and
       determine its length (or perimeter), a wetlands expert should be contacted. These other
       contacts include:

       —     The U.S. Army Corps of Engineers Civil Works district offices and EPA regional
              offices (see Highlight A-20) have wetlands experts who deal with permitting
              issues under Section 404 of the Clean Water Act.

       —     State soil and water conservation offices often have wetlands experts who deal
              with various permitting and regulatory issues.
                              HIGHLIGHT A-10
                U.S. GEOLOGICAL SURVEY EARTH SCIENCE
                      INFORMATION CENTER OFFICES






























ESIC Office
Virginia
(National
Headquarters)

Alaska



California



Colorado




Mississippi



Missouri



South Dakota



Address
Earth Science Information Center
uses
507 National Center
Reston, VA 22092
Earth Science Information Center
uses
4230 University Dr., Room 101
Anchorage, AK 99508-4664
Western Mapping Center-ESIC
uses
345 Middlefield Rd. MS 532
Menlo Park, CA 94025
Rocky Mountain Mapping Center-
ESIC
uses
Box 25046, Stop 504 Federal Center
Denver, CO 80225
Earth Science Information Center
uses
Building 3101
Stennis Space Center, MS 39529
Mid-Continent Mapping Center-ESIC
uses
1400 Independence Rd. MS 231
Rolla, MO 65401
uses
EROS Data Center
Mundt Federal Building
Sioux Falls, SD 57198
Telephone
1-800-USA-MAPS
or
(703) 648-6045

(907)786-7011



(415)329-4309



(303) 236-5829




(601)688-3544



(314)341-0851



(605)594-6161


































                                    A-43
                                                                            Section A.4

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See J
HIGHLIGHT A-11
U.S. NATIONAL PARK SERVICE
REGIONAL OFFICES
Region
North Atlantic
Mid-Atlantic
Southeast
Midwest
Rocky Mountain
Southwest
Western
Pacific Northwest
Alaska
Regional Office Address
1 5 State St.
Boston, MA 021 09
143S. 3rd Street
Philadelphia, PA 19106
75 Spring St.
Atlanta, GA 30303
1709 Jackson St.
Omaha, NE 68102
P.O. Box 25287
Denver, CO 80225
P.O. Box 728
Santa Fe, NM 87504-0728
600 Harrison St.
Suite 600
San Francisco, CA 94107
83 S. King St.
Suite 21 2
Seattle, WA 981 04
2525 Gamble St.
Anchorage, AK 99503
Telephone
(617)223-5200
(215)597-7013
(404)331-4998
(402)221-3471
(303)969-2100
(505)988-6012
(415)745-3955
(206) 553-5565
(907) 257-2687
Highlight A-21 for NPS regional boundaries.









Section A.4
                                                    A-44

-------







Seel
HIGHLIGHT A-12
U.S. FISH AND WILDLIFE SERVICE
REGIONAL OFFICES
Region
1
2
3
4
5
6
7
8
Regional Office Address
911 NE11th Ave
Portland, OR 97232-41 81
P.O. Nox1306
500 Gold Ave SW
Room 301 8
Albuquerque, NM 87103
Whipple Federal Building
1 Federal Dr.
FortSnelling, MN55111
Richard B. Russell Federal Building
Room 1200
75 Spring St. SW
Atlanta, GA 30303
One Gateway Center
Suite 700
Newton Corner, MA 02158
P.O. Box25486
Denver Federal Center
Denver, CO 80225
1011 East Tudor Rd.
Anchorage, AK 99503
1 849 C St. SW
MS 725 - ARLSQ
Washington, DC 20240
Telephone
(503)231-6118
(505) 766-2321
(612)725-3502
(404)331-3588
(617)965-5100
(303) 236-7920
(907) 786-3542
(703)358-1801
Highlight A-22 for USFWS regional boundaries.








A-45
                                               Section A.4

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HIGHLIGHT A-13
U.S. BUREAU OF LAND MANAGEMENT STATE OFFICES
State
Alaska
Arizona
California
Colorado
Eastern States Office
Idaho
Montana
Nevada
New Mexico
Oregon
Utah
Wyoming
State Office Address
222 West 7th Ave #13
Anchorage, AK 99513-7599
3707 North 7th St.
Phoenix, AZ 85011
2800 Cottage Way
Sacramento, CA 95825
2850 Youngfield St.
Lakewood, CO 8021 5
350 South Pickett St.
Alexandria, VA 22304
3380 Americana Terrace
Boise, ID 83706
P.O. Box 36800
Billings, MT59107
P.O. Box1200
Reno, NV 89520-006
P.O. Box27115
Santa Fe, NM 87502-71 15
P.O. Box2965
Portland, OR 97208
324 South State St.
Salt Lake City, UT 841 1 1 -2303
P.O. 60x1828
Cheyenne, WY 82003
Telephone
(907)271-5076
(602) 640-5501
(916)978-4743
(303) 239-3700
(703)461-1400
(208) 384-3001
(406) 255-2904
(702) 785-6590
(505) 438-7400
(503) 280-7026
(801)539-4010
(307) 775-6001













Section A.4
                                                    A-46

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See J
HIGHLIGHT A-14
U.S. NATIONAL FOREST SERVICE REGIONS
Region
Northern (Region 1)
Rocky Mountain (Region 2)
Southwestern (Region 3)
Intermountain (Region 4)
Pacific Southwest (Region 5)
Pacific Northwest (Region 6)
Southern (Region 8)
Eastern (Region 9)
Alaska (Region 10)
Regional Office Address
P.O. Box 7669
Missoula, MT 59807
P.O. Box 251 27
Denver, CO 80225
Federal Building
517GoldAve. SW
Albuquerque, NM 87102
Federal Building
324 25th St.
Ogden, UT 84401
630 Sansome St.
San Francisco, CA 941 1 1
P.O. Box3623
Portland, OR 97208
1720PeachtreeRd. NW
Atlanta, GA 30367
310 West Wisconsin Ave.
Room 500
Milwaukee, Wl 53203
P.O. Box21628
Juneau, AK 99802
Telephone
(406)329-3316
(303) 236-9427
(505) 842-3300
(801)625-5352
(415)705-2870
(503) 326-3625
(404)347-4177
(414)297-3693
(907) 586-8863
Highlight A-23 for USFS regional boundaries.









A-47
                                               Section A.4

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HIGHLIGHT A-15






















a
des
NATIONAL ESTUARINE RESEARCH RESERVE SYSTEM3
Project Name
Ahepoo-Combahee-Edisto
Basin


Apalachicola

Chesapeake Bay (VA)

Chesapeake Bay (MD)

Delaware

Elkhorn Slough

Great Bay

Hudson River


Jobos Bay

Narragansett Bay

North Carolina
Address
ACE Basin
S. Carolina Wildlife & Marine Resource Center
P.O. Box 12559
Charleston, SC29412
Apalachicola National Estuarine Research
Reserve System
261 7th Street
Apalachicola, FL 32320
Virginia Institute of Marine Sciences
P.O. Box1346
Gloucester Point, VA 23062
Dept. of Natural Resources Tidewater Admin.
Coastal Resources Division CBNERR/MD
Towes State Office Bldg B-3
580 Taylor Ave.
Annapolis, MD 21401
Delaware Estuarine Reserve
89 Kings Highway
P.O. Box 1401
Dover, DE 19903
Elkhorn Slough Reserve
1700 Elkhorn Rd.
Watsonville, CA 95076
New Hampshire Fish and Game Department
37 Concord Rd.
Durham, NH 03824
Hudson River National Estuarine Research
Reserve
c/o Bard College
P.O. Box 67
Annandale-on-Hudson, NY 12505
Jobos Bay Estuarine Reserve
P.O. Box 11 70
Guayama, PR 20785
Narragansett Bay National Estuarine Research
Reserve
Department of Environmental Management
22 Hayes St.
Providence, Rl 02908
Center for Marine Research
7205 Wrightsville Ave.
Wilmington, NC 28403
Status
Proposed


Designated

Proposed

Designated

Proposed

Designated

Designated

Designated


Designated

Designated

Designated
Phone
(803) 762-5052


(904) 653-8063

(804) 642-71 35

(410)974-2784

(302) 739-3091

(408) 728-2822

(603)868-1095

(914)758-5193


(809) 864-01 05

(401 ) 683-6780

(919)256-3721
Mote that proposed reserves are not eligible for MRS scoring but are included because they may be
gnated in the near future.























(continued on next page)
Section A.4
                                                   A-48

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HIGHLIGHT A-15 (continued)






















NATIONAL ESTUARINE RESERVE SYSTEM
Project Name
North Inlet-Winyah Bay

Old Woman Creek

Padilla Bay
Rookery Bay

St. Lawrence River
Basin

Sapelo Island

South Slough

Tijuana River
Waimanu Valley
Waquoit Bay

Weeks Bay

Wells


Address
Baruch Marine Lab
P.O. Box1630
Georgetown, SC 29442
Old Woman Creek
251 4 Cleveland Rd. East
Huron, OH 44839
Padilla Bay
1043 Bayview-Edison Rd.
Mt. Vernon, WA 98273
Rookery Bay
10 Shell Island Rd.
Naples, FL 33962
St. Lawrence Eastern Ontario
Commission
317 Washington St.
Watertown, NY 13601
Department of Natural Resources
P.O. Box 15
Sapelo Island, GA 31327
South Slough
P.O. Box 5417
Charlestown, OR 97420
Tijuana River
301 Caspian Way
Imperial Beach, CA91932
Dept. of Land and Natural Resources
Division of Forestry 7 Wildlife
567 S. King St. Room 132
Honolulu, HI 96813
Waquoit Bay (WBNERR)
P.O. Box3092
Waquoit, MA 02536
Weeks Bay Estuarine Research Reserve
10936-B
US Highway 98
Fairhope, AL 36532
Wells Estuarine Reserve
RR2
6ox 806
Wells, ME 04090
Status
Proposed

Designated

Designated
Designated

Proposed

Designated

Designated

Designated
Designated
Designated

Designated

Designated


Phone
(803) 546-3623

(419)433-4601

(206)428-1558
(813)775-8845

(315)785-2460

(912)485-2251

(503) 888-5558

(619)575-3613
(808) 587-0054
(508) 457-0495

(205) 928-9792

(207)646-1555

























A-49
                                               Section A.4

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HIGHLIGHT A-16
NEAR COASTAL WATERS PROGRAM EPA REGIONAL CONTACTS
EPA Region
Headquarters
1
2
3
4
5
6
9
10
Regional Office Address
401 M Street SW
Washington, DC 20036
JFK Federal Building (WQE-425)
Boston, MA 12203
Marine and Wetland Protection Branch
26 Federal Plaza
New York, NY 10278
Marine and Estuary Section
841 Chestnut St.
Philadelphia, PA 19104
Coastal Planning Unit
345 Courtland St. NE
Atlanta, GA 30365
Water Division
77 West Jackson Boulevard (WQ-16J)
Chicago, IL 60604
Marine and Estuary Section
1445 Ross Avenue
Suite 1200
Dallas, TX 75202
Wetland and Coastal Planning Section
75 Hawthorne St.
San Francisco, CA94105
Office of Coastal Waters
12006th Ave.
Seattle, WA 981 01
Telephone
(202) 260-5554
(617)565-4870
(212)264-5170
(215)597-9589
(404)347-1740
(312)353-2079
(214)655-6680
(415)744-1974
(206) 553-0966










Section A.4
                                                    A-50

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HIGHLIGHT A-17
EPA REGIONAL CLEAN LAKES PROGRAM OFFICES
EPA Region
1
2
3
4
5
6
7
8
9
10
Regional Office Address
JFK Federal Building
Boston, MA 02203
26 Federal Plaza
New York, NY 10278
841 Chestnut St.
Philadelphia, PA 19107
345 Courtland St.
Atlanta, GA 30365
77 West Jackson Boulevard
Chicago, IL 60604
First Interstate Bank Tower
1445 Ross Avenue
Dallas, TX 75202
726 Minnesota Ave.
Kansas City, KS66101
One Denver Place
999 18thSt, Suite 500
Denver, CO 80202-2406
75 Hawthorne Street
San Francisco, CA 94105
1200 Sixth Ave.
Seattle, WA 981 01
Telephone
(617)565-3515
(212)264-8708
(215)597-3429
(404)347-2126
(312)886-0209
(214)655-7140
(913)551-7500
(303)293-1574
(415)744-2018
(206)553-6911











A-51
                                                Section A.4

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indivic
HIGHLIGHT A-18
NAUTICAL CHART NUMBERS FOR MARINE SANCTUARIES
National Marine Sanctuary
Monitor
Grays Reef
Florida Keys
Key Largo
Looe Key
Cordell Banks
Gulf of the Farallones
Channel Islands
Fagatele Bay
State or
Territory
NC
GA
FL
FL
FL
CA
CA
CA
American
Samoa
Nautical Chart Number3
12200
13003
11009
11009
11480
111013
411
11450
111013
411
11450
111013
411
11450
11434
11420
18640
18640
18680
18645
18740
(San Miguel Pass) 18727
(Santa Cruz Channel) 18728
(Anacapa Pass) 18729
(Santa Barbara Island) 18756
(San Nicolos Island) 18755
83484

aProvided by NOAA for ordering purposes. May represent categories of charts rather than
ual charts; this will be clarified in a subsequent draft.
Section A.4
                                                    A-52

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HIGHTLIGHTA-19
NATIONAL ESTUARY PROGRAM INFORMATION SOURCES
Project Name (EPA Region)
Buzzards Bay (1)
Casco Bay (1)
Long Island Sound (1)
Massachusetts/Cape Cod Bays (1)
Narragansett Bay (1)
Delaware Bay (2)
Long Island Sound (2)
Delaware Bay (3)
New York/New Jersey Harbor (2)
Delaware Inland Bays (3)
Albemarle-Pamlico Sounds (4)
Indian River Lagoon (4)
Sarasota Bay (4)
Tampa Bay (4)
Barrataria-Terrebone Estuarine
Complex (4)
Galveston Bay (6)
San Francisco Bay (9)
Santa Monica Bay (9)
Puget Sound (10)
Headquarters Address
(all projects)
OCPD
U.S. EPA
401 M Street SW
Washington, DC 20460

















Phone Number
(at Headquarters)
(202)260-9176
(202)260-9176
(202)260-9176
(202) 260-6504
(202) 260-6466
(202) 260-9799
(202)260-9176
(202) 260-6466
(202) 260-6779
(202) 260-9799
(202)260-9137
(202)260-9137
(202)260-9137
(202)260-9137

(202) 260-6467
(202) 260-6467
(202) 260-9038
(202) 260-9038
(202) 260-9038



















A-53
                                               Section A.4

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HIGHLIGHT A-20
EPA REGIONAL OFFICES
EPA Region
1
2
3
4
5
6
7
8
9
10
Regional Office Address
JFK Federal Building
Boston, MA 12203
26 Federal Plaza
New York, NY 10278
841 Chestnut St.
Philadelphia, PA 19107
345 Courtland St. NE
Atlanta, GA 30365
77 West Jackson Boulevard
Chicago, IL 60604
First Interstate Bank Tower
1445 Ross Avenue
Dallas, TX 75202
726 Minnesota Ave
Kansas City, KS66101
One Denver Place
999 18th St. Suite 500
Denver, CO 80202-2406
75 Hawthrone Street
San Francisco, CA 94105
1200 Sixth Ave.
Seattle, WA 981 01
Telephone
(617)565-3420
(212)264-2657
(215)597-9800
(404) 347-4727
(312)353-2000
(214)655-6444
(913)551-7000
(303)293-1603
(415)744-1180
(206)442-1200











Section A.4
                                                    A-54

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                                                    HIGHLIGHT A-21
                               NATIONAL PARK SERVICE REGIONAL BOUNDARIES
Alaska;
Hawaii:
Guam and American Samoa:
Puerto Rico:
U.S. Virgin Islands:
Alaska Region
Western Region
Western Region
Southeast Region
Southeast Region
                                                                                                                   RI
Not all Park Service boundaries follow state boundaries.

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a
o
en
05
                                                                   HIGHLIGHT A-22
                                         U.S.  FISH AND WILDLIFE SERVICE REGIONAL BOUNDARIES
                                                                NORTH DAKOTA 1 MINNESOTA
                                                                SOUTH DAKOTA
                                                                                                                PENNSYLVANIA
                                       ARIZONA   /  NEW MEXICO
                                     Region 7
                                     Region 1
                                     Region 4
                                     Region 4
Alaska:
Hawaii;
Puerto Rico;
U.S. Virgin Islands:

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                                                   HIGHLIGHT A-23
                                 U.S. FOREST SERVICE REGIONAL BOUNDARIES
                                                NORTH DAKOTA 1 MINNESOTA
Alaska:
Hawaii:
Puerto Rico:
U.S. Virgin Islands:
Alaska Region
Pacific Southwest Region
Southern Region
Southern Region
Not all Forest Service regional boundaries follow state boundaries

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                                      MAR
                                                                    OSWEm-9200,0-66
SUBJECT:   Transmittal of Amendments to Superfund                     Guidance
             Incorporating Native American Traditional Lifeways
FROM:      JaimS/K Woolford, Dirytor
             Office of Superfund Remediation and Technology Innovation

TO:                          Policy                  1-10



      The attached document amends the November 1992 Hazard Ranking System (HRS)
Guidance Manual (EPA 540-R-92-026, November 1992) by adding examples, consistent with
the HRS, on ways Native American lifeways can be considered under the HRS; It does not
otherwise supersede or change the guidance. This will help the Superfund program to better
         and account for Native American traditional lifeways in the National Priorities List
(NPL)



      In 1998 the Assistant Administrator of EPA' s Office of Solid Waste and Emergency
Response (OSWER)       to examine technical scoring guidance for the HRS, a mathematical
model used to determine site eligibility for the NPL,  This examination would identify ways in
which the HRS Guidance could better take into account Native American cultural practices
          lifeways). The Office of Inspector General, in a 2004 evaluation report on the
         Tribal                         HRS and                      more




      When the HRS Guidance Manual was first developed over a decade ago, the preparers
did not explicitly consider using Native American cultural examples. However, there are a
number of ways in which EPA's HRS Guidance can appropriately consider traditional lifeways.
            to the 1992 HRS Guidance Manual follow as an attachment.  In these amendments
we                             the HRS, of some of the ways site         can consider
Native                                        HRS

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Encourage Active Tribal Involvement

       Regional Superfund staff should follow the consultation procedures presented in
"Consulting with Indian Tribal Governments at Superfund Sites: a Beginner's Booklet"
(http://www.epa.gov/superfund/partners/oerr/stsi.htm), OSWER 9200.3-42, November 2006.
Staff should make other personnel working in site assessment aware of the guidance as well.
Further, EPA Regional assessment personnel should involve interested tribes in assessment and
potential listing activities, since tribes can be a valuable source of information.  As the
consultation booklet says: "EPA is better able to fulfill its responsibility to 'protect human health
and the environment' if the Agency utilizes the tribal consultation process by taking advantage of
the insight and knowledge tribal governments can provide."

Limitations of this Guidance

   Several tribes have provided feedback on several concerns that unfortunately cannot be
addressed in these amendments.

       Tribal  Populations - Small and/or rural tribal populations believe they are at a
disadvantage in the HRS formula provided at 40 CFR 60, Appendix A.  They believe that risks
posed to an entire reservation or tribe, regardless of number, should have greater weight than
what the current HRS provides. Addressing this concern would require a regulatory change to
the HRS, which is beyond the scope of this guidance.

       Potential scoring misperception - There was a perception that sites with higher HRS
scores are always riskier and will  be cleaned up sooner than sites with lower scores. This is not
true. The HRS is not a risk assessment and a site's HRS score does not determine risk.
Moreover, the HRS score does not determine site priority for EPA. It is usually only used to
document the eligibility of a site for inclusion on the NPL.

Conclusion

       EPA should consider, to the extent  allowed under the HRS, Native American traditional
lifeways when assessing a site for listing. Further, Native Americans should be aware that there
are many other options that may be available to address environmental problems. Other
programs within OSWER, such as Superfund removal, brownfields cleanup, solid waste,
underground storage tanks or oil spill prevention and cleanup, may be appropriate mechanisms
for reducing the human health and ecological risks on tribal lands. Similarly, programs under
other Federal agencies,  such as those of trustee agencies, may be able to perform response
activities.

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Contact

      For additional information or questions concerning this guidance amendment, please
contact me or have your staff contact Robert Myers, the Superfund Headquarters Tribal
Coordinator, at (703) 603-8851.

Attachments

cc:    OSRTI Managers
      Susan Bodine, OSWER
      Barry Breen, OSWER
      Scott Sherman, OSWER
      Ed Chu, Land Revitalization Staff
      Debbie Deitrich, OEM
      David Lloyd, OBCR
      Matt Hale, OSW
      Cliff Rothenstein, OUST
      Mary-Kay Lynch, OGC
      Susan Bromm, OSRE
      David Kling, FFEO
      Marsha Minter, IPCO
      Gail Cooper, FFRRO
      Joanne Marinelli, Superfund Lead Region Coordinator, US EPA Region 3
      NARPM Co-Chairs
      OSRTI Documents Coordinator

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                                                               OSWER 9200.0-66

                             HRS Guidance Amendments

Native American Advice on Sensitive Environments l

The HRS Guidance Manual explains the categories used for identifying contaminated sensitive
environments in the surface water, soil, and air pathways.

The guidance indicates that Natural Resource Trustees should determine whether a potentially
sensitive area meets the definition of the following two categories:

    •   Migratory pathways and feeding areas critical for maintenance of anadromous fish
       species within river reaches or areas in lakes or coastal tidal waters in which the fish
       spend extended periods of time.
    •   Spawning areas critical for maintenance offish/shellfish species within river, lake, or
       coastal tidal waters.

Tribes are identified in the HRS Guidance as Natural Resource Trustees.2  Thus, for these
sensitive environments, no changes to the HRS Guidance are necessary, but the Office of
Superfund Remediation and Technology Innovation (OSRTI) would like to remind site assessors
that Native American tribes are trustees for resources on or related to tribal lands or for resources
for which they may have treaty rights.3

Example: Salmon are a significant part of some tribes' traditional lifeways. If a tribe is the
Natural Resource Trustee for a salmon spawning area, a designated tribal fish and wildlife
official could make the determination whether the area meets the definition of a "spawning area
critical for maintenance offish/shellfish species within rivers, lakes, or coastal tidal waters."4

For other sensitive environment categories, the HRS Guidance asks the site assessor to consult
with various governmental agencies to make the determination. These categories are:

    •   Habitat known to be used by federal designated or proposed endangered or threatened
       species.
    •   Particular areas, relatively small in size, important to maintenance of unique biotic
       communities.
    •   Terrestrial areas utilized for breeding by large or dense aggregations of animals.

For these, the guidance does not include the example of consulting with tribal agencies or
officials. However, the guidance does say to consult with appropriate federal, state, county, or
1 HRS Tables 4-23 and 5-5, HRS Sections 4.1.4.3.1 for surface water, 5.1.3.5 for soil and 6.3.4 for air
2 Guidance Manual Highlight A-5
3 Guidance Manual Highlight A-5, footnote c
4 Guidance Manual Highlight A-7

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local representatives of agencies,5 and tribal officials could also be knowledgeable and
appropriate representatives. We are amending the guidance to explicitly include tribal officials as
contacts for identifying these sensitive environments.

Example: A tribal fish and wildlife official might identify an area of traditional medicinal plant
growth as a "unique, rare, or otherwise ecologically valuable biotic area."6

See guidance amendments in Appendix 1.
Native American Resource Usage 7

The HRS guidance resources factor discussion clarifies the possible loss of resource use resulting
from site-related contamination in the ground water, surface water, soil, and air pathways.  The
HRS identifies the uses, including crop irrigation, watering of commercial livestock, ingredients
for commercial food preparation, commercial aquaculture (or agriculture or silviculture), and
supply for a major or designated recreational area. The uses vary depending on the pathway.
The HRS Guidance Manual defines these terms more specifically and provides illustrations.8
Many of the resources listed are commercial resources, but some Native American communities
use a barter system in which food or other products are traded rather than purchased.  Although
such a system is outside the mainstream U.S. currency economy, it is consistent with the
examples provided in the HRS Guidance Manual to consider products widely traded or
distributed similarly as products widely sold.  The tribal system merely removes the extra step of
currency exchange.  Including the tribal system also is consistent with the standard definition of
commercial as "engaged in or related to commerce", and commerce as the "exchange or buying
and selling of commodities."9  The guidance is changed to apply tribal trading to all of the
commercial resource categories.

Native American  recreation resource use areas (such as canoeing for surface water and
community gathering areas such as sweat lodges for ground water and pow wow grounds for the
air pathway) are appropriate examples of major recreational areas and they are consistent with
the guidance definitions of major or designated recreation area for ground water,10 surface
water,11 and air.12 The guidance is amended to include these examples.

The guidance  applicable to the surface water pathway includes a list of sources of information on
possible  surface water uses, and includes local chambers of commerce, state or regional parks
and recreation departments and state water supply offices.13 We are amending the guidance to
5 Guidance Manual, p. A-27-29
6 Guidance Manual p. A-28
7 HRS sections 3.3.3, 4.1.2.3.3, 5.1.3.4, 6.3.3
8 Guidance Manual p. 193 for ground water, p. 289 for surface water, p. 371 for soil, and p. 421 for air
9 Webster's Ninth New Collegiate Dictionary, 1985
10 Guidance Manual p. 193
11 Guidance Manual p. 289
12 Guidance Manual p. 421
13 Guidance Manual p. 290

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add Native American officials as a source in determining resource uses. Finally, site assessors
                                                         14
are reminded they should also use the checklist for resources,   provided in the original
guidance, in identifying potential Native American resources.

See guidance amendments in Appendix 2.
Native American Workers15

The HRS ground water migration pathway discusses how to evaluate the population factor. The
population factor includes residents, students, and workers who regularly use the water, but
excludes transient populations such as customers and travelers passing through the area. Similar
population considerations of workers occur for the surface water and air pathways. The soil
pathway has additional constraints; workers must be working on a property with observed
contamination and in a workplace area within 200 feet of that contamination.

The HRS Guidance generally defines workers as permanent employees (part-time or full-time) of
a facility or business.16  Clearly, Native American or other outdoor artisans or  craft people can
be considered workers in calculating the target population, provided they meet all other
appropriate HRS target criteria. Although we might typically think of workers as located in
office buildings or manufacturing facilities, this is not necessarily true of Native American or
other outdoor artisan workers. Workers include those working outdoors, as well as indoors.
Workplace areas (unique to the soil pathway) include areas outdoors,  as well as indoors.17

The guidance is amended to include this change in all four pathways.

See guidance amendments in Appendix 3.
Native American Seasonal Populations18

As mentioned under workers above, the HRS specifies that "Population" for the ground water,
surface water, and air pathways includes resident, worker, or student populations. The HRS
Guidance clarifies this by saying workers and students can be part-time, and seasonal
populations (such as at a resort area) are included.19 Clearly, a seasonal tribal camp or work area
population could be considered a seasonal population.

The guidance is amended to add this tribal example in the surface water, ground water, and air
pathways.
14 Guidance Manual Highlight 8-45
15 HRS sections 3.3.2, 4.1.2.3.2, 5.1.3, and 6.3.2
16 Guidance Manual p. 165 for ground water, p. 266 for surface water, p. 371 for soil, and p. 412 for air
17 Guidance Manual p. 371 for soil
18 HRS sections 3.3.2, 4.1.2.3.2, and 6.3.2
19 Guidance Manual p. 163-165 for ground water, p. 265-266 for surface water, and p. 412 for air

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See guidance amendments in Appendix 4.
Attractiveness/Accessibility of Native American Recreational Use Areas20

The HRS provides, for the soil pathway only, assigning a value for attractiveness/accessibility to
areas of observed contamination. The HRS Guidance Manual21 adds examples, such as open
fields where people play frisbee or non-maintained baseball fields, under the areas regularly used
for public recreation.

Evaluations of the attractiveness/accessibility of an area of observed contamination for the soil
exposure pathway should take into account Native American recreational areas, such as
traditional hunting or community gathering areas such as camping or pow wow grounds. Pow
wow grounds, regularly used in late summer and fall and containing bleachers and coverings for
the performers, would fit under "designated recreational areas",22 and the attached amendments
add the pow wow grounds example to the guidance. The appropriate categories for other tribal
recreational areas would depend on the specific usage of those areas. It is necessary to document
why each assigned value was selected.  As mentioned in other sections, tribal officials may be
helpful in identifying such areas, which could be unique to the tribe.

See guidance amendments in Appendix 5.

Notice: This document provides guidance to EPA personnel regarding ways to consider Native
American traditional lifeways when scoring sites under the HRS. This document does not create
any legally binding requirements, but rather suggests an approach that may be used,  as
appropriate, given the site-specific circumstances. This document does not substitute for EPA's
statutes and regulations,  and interested parties are free to raise questions and objections about the
appropriateness of applying the approach presented in this guidance to  a particular situation.
EPA may change this guidance in the future.
20 HRS section 5.2.1.1 and Table 5-6
21 Guidance Manual p. 390 and Highlight 9-21
22 Guidance Manual Highlight 9-21

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                                     Appendix  1
(3)     Determine which of the areas meet the definitions of a partially developed coastal barrier or an
       undeveloped coastal barrier (as specified in Section A.2):

              The entire coastal barrier is undeveloped if it contains (on average) fewer than one
              man-made structure per 5 acres of fastland area.

              A portion of the coastal barrier is undeveloped if it has at least 1/4-mile of undeveloped
              shoreline on the shoreward side of the coastal barrier and the undeveloped area extends
              through the fastland from the beach to the associated landward aquatic habitat.

              A coastal barrier is partially developed if it contains (on average) one or more manmade
              structures per 5 acres of fastland, but no more than 50 percent of the fastland area is
              covered by one or more man-made structures per 5 acres of fastland area. A coastal
              barrier that is more than 50 percent developed is not  eligible for evaluation as a partially
              developed coastal barrier.

(4)     Evaluate each of the qualifying areas as an undeveloped or partially developed coastal barrier. If
       the same coastal barrier has portions that qualify as both undeveloped and partially developed,
       evaluate either the undeveloped or partially developed portions, but not both (i.e., do not score
       the same coastal barrier as both undeveloped and partially developed).

COASTAL BARRIER - UNDEVELOPED

              See subsection above, Coastal Barrier — Partially Developed.

HABITAT KNOWN TO BE USED BY A FEDERAL DESIGNATED OR PROPOSED ENDANGERED OR
THREATENED SPECIES

(1)     Determine whether any of the species (as defined in Section A. 1) are known to be present in
       and using suitable habitat within the TDLs(DC-afoao of obcorvod oontaminati.oo)ijbr the site.
       Contact a representative of an appropriateJFederal, state, county, or local agency)e.g.,
       USFWS, NMFS, state fish and game department, state Natural I leritage prograrfi) or a
       recognized expert to help determine if suitable habitat for any of the species exists within the
       TDLs or areas of contamination and if the habitat is currently  occupied and used  by the
       species. It may be difficult to obtain information beyond the known presence of a  species
       within a given area, distance ring, or surface water body. If it is not possible to document the
       presence of one or more of the species within the TDLs (or areas of contamination), stop;
       otherwise, proceed to Step (2).

(2)     Document all habitat known to be used  by each eligible species within the TDL. Appropriate
       documentation includes (but is not limited to):

                     A written or documented oral statement from a representative of the appropriate
                     Federal, state, or local agency (or from a recognized expert) that establishes the
                     presence of the species within the TDLs or area of observed  contamination; or

                     Any other evidence that documents the recent presence of the species in
                     suitable habitat within the TDLs or areas of observed contamination (e.g., within
                     a 5-year period prior to  HRS package preparation).

              Ensure that a habitat identified as used by a Federal  designated or proposed endangered
              or threatened species (or a portion thereof) is not listed as a critical habitat for that
              species as defined in Section A.2. If an area is a critical habitat for a Federal designated
              species, the area qualifies as a separate sensitive environment for HRS scoring and
              should be evaluated for that species based solely on  that classification.


                                           A-27                                    Section A.3
                           .Federal, state, tribal, county,  or local  agency...
                                Appendix 1 - page 1 of 3

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HABITAT KNOWN TO BE USED BY A SPECIES UNDER REVIEW AS TO ITS FEDERAL
ENDANGERED OR THREATENED STATUS

       See subsection above, Habitat Known to be Used by a Federal Designated or Proposed
       Endangered or Threatened Species.

HABITAT KNOWN TO BE USED BY A STATE DESIGNATED ENDANGERED OR THREATENED
SPECIES

       See subsection above, Habitat Known to be Used by a Federal Designated or Proposed
       Endangered or Threatened Species.

MIGRATORY PATHWAYS AND FEEDING AREAS CRITICAL FOR MAINTENANCE OF
ANADROMOUS FISH SPECIES WITHIN RIVER REACHES OR AREAS IN LAKES OR COASTAL
TIDAL WATERS IN WHICH THE FISH SPEND EXTENDED PERIODS OF TIME

(1)     Contact one or more of the following, provide them with the definitional criteria for these
       sensitive environment categories (i.e., as stated in MRS Table 4-23), and ask them to determine
       whether any surface water bodies within the TDLs meet one or all of the definitional criteria:

              Representatives of agencies designated as CERCLA natural resource trustees (see
             Highlight A-5);

              Representatives of state or local agencies that have statutory responsibility for or
             involvement in management of the area or types of species of concern (e.g., state fish
             and game departments), even if these agencies are not designated CERCLA natural
             resource trustees; and/or

              Recognized experts familiar with the area or types of species of concern.

(2)     Request written documentation (on appropriate letterhead) that the area of concern is a critical
       spawning area and some information about the species and habitat(s) of concern (e.g., some
       explanation as to why the habitat is critical). The documentation should be legally defensible for
       CERCLA damage assessment purposes. Examples of suitable evidence are provided in
       Highlights A-6 and A-7). If these individuals do not identify any qualifying areas, stop;
       otherwise, proceed to Step (3).

(3)     Evaluate each qualifying area identified as a critical spawning area, migratory pathway, or
       feeding area.

PARTICULAR AREAS, RELATIVELY SMALL IN SIZE, IMPORTANT TO MAINTENANCE OF UNIQUE
BIOTIC COMMUNITIES
                                          I Heritage ProgramsTstate natural resources agencies^)
                                          ' unique, rare, or otherwise ceatogically valuable biotie
(1)     Contact representatives from State Natural I
       and recognized experts to determine if any i
       areas (e.g., old growth areas, pine barrens, bogs) are located within the TDLs (or areas of
       observed contamination) for the site. If there are no such areas within the TDLs of the site,
       stop; otherwise, proceed to Step (2).
(2)     Determine if each area in question meets the definitional criteria as specified in Section A.2.
       Four types of areas generally will meet the following definitional criteria for this sensitive
       environment (note that other areas that do not meet these criteria may be eligible):

             Areas with a high proportion of species with highly restrictive habitat requirements due to
             unusual natural biotic and/or abiotic conditions;

Section A.3                                   A-28
                                               .state or tribal natural resources agencies.
                               Appendix 1 - page 2 of 3

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              Isolated areas that may or may not have an unusual community structure per se, but are
              particularly important to the continued existence of their biotic communities because of
              their geographic isolation;

              Areas with a high proportion of locally endemic species because of a relatively long
              period of geographic isolation and/or are exceptional examples of "climax" communities
              because of minimal human disturbance; or

              Areas that are vital to a species for maintenance of a community.

SPAWNING AREAS CRITICAL FOR THE MAINTENANCE OF FISH/SHELLFISH SPECIES WITHIN
       RIVER, LAKE, OR COASTAL TIDAL WATERS

       See subsection above, Migratory Pathways and Feeding Areas Critical for Maintenance of
       Anadromous Fish Species Within River Reaches or Areas in Lakes or Coastal Tidal Waters in
       which the Fish spend Extended Periods of Time.

TERRESTRIAL AREAS USED FOR BREEDING BY LARGE OR DENSE AGGREGATIONS OF
ANIMALS
(1)     Contact state fish and game officials, U^FWS officials, or recognized experts to determine
       whemer-any terrestrial species that-nofmally breed in large or dense aggregations have been
       observed or are expected to be present within the air and surface water pathway TDLs or areas
       of observed contamination of the site. If no such species have been observed or are expected
       to be present within the TDL or area of observed contamination, stop; otherwise, proceed to Step
       (2).

(2)     Determine if each area in question meets the definitional criteria specified in Section A.2 and if
       such breeding occurs within that area. Support documentation may include defining the
       breeding habitat requirements of the species of concern and demonstrating that the species
       typically nests or breeds in large colonies or dense aggregations. Additional pathway-specific
       criteria include:

              In the surface water pathway, eligible areas are limited to terrestrial areas that are used
              for breeding by terrestrial vertebrate species with aquatic or semi-aquatic foraging habits
              (i.e., birds, mammals, or reptiles that consume fish or other aquatic organisms that
              inhabit or might inhabit the surface water bodies within the TDL). Such species generally
              correspond to those defined in Section A.2 as "terrestrial vertebrates with semi-aquatic
              habits".

              In the soil exposure pathway, eligible areas are limited to terrestrial areas that are at
              least partially in the area of observed contamination and  are used for breeding by
              terrestrial vertebrate species.

              In the air pathway, eligible areas are limited to terrestrial  areas that are at least partially
              within the TDL and are used for breeding by terrestrial vertebrate species.

WETLANDS

(1)     Determine if there are any wetlands within the air or surface water pathway TDLs. As a starting
       point, use existing  maps to delineate wetlands within the TDL. The preferred maps are the NWI
       Maps or state maps of equivalent quality.  If these maps are not available, use USGS
       topographic maps or Soil Conservation Service (SCS) maps to initially screen wetlands
       locations.
                                           A-29
C
                               ...state or tribal fish and game  officials...
                        .»»____                                              ^__
                                Appendix 1 - page 3 of 3

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            Appendix 2
    SECTION 7.8
    RESOURCES AND
    WELLHEAD PROTECTION
    AREA
      This section provides guidance on scoring the resources and wellhead protection area (WPA)
    factors for the targets factor category of the ground water pathway. The resources factor (MRS section
    3.3.3) evaluates the possible loss of ground water use value resulting from site-related contamination. It
    does not evaluate threats to human health that are considered in the nearest well and population factors.
    The wellhead protection area factor (MRS section 3.3.4) evaluates the possibility that a source or
    observed release lies in or near an area that a state has designated for protection under the SDWA.
      Section 3.3.3
      Section 3.3.4
RELEVANT MRS SECTIONS

Resources
Wellhead protection area
    DEFINITIONS
      Commercial Aquaculture: Cultivation of fish or shellfish to be sold for widespread distribution.
      Examples include a rearing pond used to raise catfish or a pond for nonfood crops such as
      goldfish and tropical fish.
      ^z:s~~*==     • ^   -    =~-
      Commercial Food Crops: Crops that are intended to be sold widely, such as in supermarkets,
      and locally, such as those sold at local produce stands. Crops grown for domestic consumption
      .jirfpr use in a single restaurant are not considered commercial food crops.

     /'"Commercial Forage Crops: Crops grown to be sold as food for livestock (it is not necessary to
     f document that these crops were sold only for commercial livestock), and grasslands used for
     V grazing by commercial livestock (including areas technically defined as "pasture/rangeland" by
     V^jheUSDA).
      J""~ 	 ' 	 	 	    	 	
      gredient In Commercial Food Preparation: Ground water used for wholesale food
      sparation (e.g., a manufacturer that prepares food products to be sold in supermarkets or
      Dduce stands). Food prepared in restaurants is not included in this category.
      ^^—__	 _1B—
      r_—,—  .	.	•



      state, or Federal) as an area for public recreation (e.g., municipal swimming pool).
   Commercial Aquaculture:
 sold or traded for widespread distribution...
   193
           Section 7.8
   Commercial Food Crops: Crops that ~~~~~-~-x
  are intended to be sold or traded widely, such as in
supermarkets, and locally, such as those sold at local produce
  stands or traded within a Native community....
  CommercfaS Forage Crops:
 ..sold or traded as food for livestock..
   Ingredient in Commercial Food Preparation:
       Major or Designated Water
       Recreation Area: ...for recreational
     purposes (e.g., a water theme park or sweat
     lodge). ...by a government body (e.g. local,
        state, tribe, or Federal)...
...sold or traded in supermarkets, produce stands, or traded within a
      Native community..
           Appendix 2 - page 1 of 5

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                   SECTION 8.11
                   RESOURCES
                         This section provides guidance on scoring the resources factor for the targets factor category of
                  the surface water drinking water threat. The resources factor evaluates the possible loss of surface water
                  use resulting from site-related contamination of the surface water. The resources factor does not
                  evaluate threats to human health, which are considered in the nearest intake and population factors, and
                  in the human food chain threat. Unlike the ground water resources factor, the surface water resources
                  factor does not address commercial aquaculture, which is evaluated in the human food chain threat.
                  MRS section 4.1.2.3.3 discusses the resources factor.
                   DEFINITIONS
                         Commercial Food Crops: Crops that are intended to be sold widely, such as in supermarkets,
                         and locally, such as those sold at local produce stands. Crops grown for domestic consumption
                         or for use in a single restaurant are not considered commercial food crops.
                        j-—•—"""^J	             	                   	  	 """"
                         Commercial Forage Crops: Crops grown to be sold as food for livestock (it is not necessarylo"*
                         document that these crops were sold only for commercial livestock), and grasslands used for
                         grazing by commercial livestock (including areas technically defined as "pasture/rangeland1 by
                        4heUSDA).
                        «———  	
                         Commercial Livestock: Livestock raised for sale to commercial wholesalers or supermarkets.^
                         Livestock raised for private or domestic use is not considered commercial livestock.

                         Designated for Drinking Water Use: Section 305(a) of the Clean Water Act requires states to
                         prepare a water quality inventory that designates and classifies certain waters for drinking water
                         use. The water can have such a classification even if it is not currently used for or is not currently
                         suitable to be used for drinking water.
                           J" "~~~~~    ~" '
                           iredient In Commercial Food Preparation: Surface water used for wholesale food
                           iparation (e.g., a manufacturer that prepares food products to be sold in supermarkets or
                           iduce stands). Food prepared in restaurants is not included in this category.
                          _^—__,	__	
                        ^—•—  —•—•—.	.	•—
                         Major or Designated Water Recreation Area:  A major water recreation area is an area used by a
                         large number of people for recreational purposes (e.g., swimming or fishing). A designated water
                         recreation  area is an area designated and maintained by a government body (e.g. local, state, or
                         Federal) as an area for public recreation.
                        —-	
                  SCORING THE RESOURCES FACTOR

                  (1)     Use the checklist In Highlight 8 45  det rmine if any surf              h
                         assigned resource points apply to the      bed. Do not use standby intakes to evaluate the
                         resources factor.
  Commercial Food Crops: Crops that are
  intended to be sold or traded widely, ...and
  locally, such as those sold at local produce
stands or traded within a Native community..
289
               Commercial Forage Crops:
          ...sold or traded as food for livestock...
            Commercial Livestock:
            ...raised for sale or trade...
   Ingredient in Commercial  Food Preparation:
   sold or traded in supermarkets, produce stands, or
           traded within a Native community..
    Major or Designated Water Recreation Area:
    ...for recreational purposes (e.g., swimming, ©f
  fishing,  or canoeing). ...by a government body (e.g
              local, state, tribe, or Federal)...
                                               Appendix 2 - page 2 of 5

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             SECTION  9.5
             WORKERS AND
             RESOURCES
                   This section provides guidance for evaluating workers and scoring the resources factor for the
             targets factor category in the resident population threat of the soil exposure pathway. The workers factor
             is used to score the targets factor category of the resident population threat. The scorer must consider
             the number of workers who frequent workplace areas on or near the area of observed contamination.
             The resources factor evaluates the possible loss of resource use resulting from surficial contamination at
             a site. The factor evaluates the presence of commercial agriculture, commercial silviculture, commercial
             livestock production, and commercial livestock grazing; it does not evaluate threats to human health or
             sensitive environments.
                    Section 5.1.3
                    Section 5.1.3.3
                    Section 5.1.3.4
                    Section 5.1.3.6
RELEVANT MRS SECTION

 Targets
 Workers
 Resources
 Calculation of resident population targets factor category value
             DEFINITIONS
                   Commercial Agriculture: Production of crops for sale, including crops intended for widesprea
                   distribution (e.g., supermarkets) and more limited distribution (e.g., local produce stands), and
                   any nonfood crops such as cotton and tobacco. Commercial agriculture does not include
                   livestock production, livestock grazing, or crops grown for household consumption (e.g.,
                  ^backyard garden or fruit trees).

                   Commercial Livestock Production or Commercial Livestock Grazing: Raising or feeding of
                   livestock for sale.

                   Commercial Silviculture: Cultivation of trees for sale (e.g., Christmas tree farm, trees raised
                   for lumber).

                   Worker: A person working on a property with an area of observed contamination and whose
                   workplace area is on or within 200 feet of an area of observed contamination. Both full and
                   part-time workers are considered.

                   Workplace Area: Any area where workers are regularly present. Areas receiving only brief but
                   regular use (e.g.,  parking areas, lunch areas) may qualify as work areas.
                                                     371
                                                                                         Section 9.5
  Commercial Agriculture: ...crops
for sale or trade...(e.g., local produce
   stands or traded within a Native
             community),...
                                                         Commercial Silviculture:
                                                             ...for sale or trade...
                                                        Commercial Livestock Production or Commercial
                                                                Livestock Grazing: ...for sale or trade..
                                          Appendix 2 - page 3 of 5

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            SECTION  10.4
            RESOURCES
                  This section provides guidance for scoring the resources factor in the air pathway. The resources
            factor evaluates potential damage to recreation areas, commercial agriculture, and commercial
            silviculture due to site-related atmospheric contaminants. It does not evaluate threats to human health or
            sensitive environments.
                   Section 6.3
                   Section 6.3.3
 RELEVANT MRS SECTIONS

Targets
Resources
            DEFINITIONS
                  Commercial Agriculture: Production of crops for sale, including crops intended for widespread
                  distribution (e.g., supermarkets) and more limited distribution (e.g., local produce stands), and
                  any nonfood crops such as cotton and tobacco. Commercial agriculture does not include
                  livestock production, livestock grazing, or crops grown for household consumption (e.g.,
                 Jbackyard garden or fruit trees).
                  Commercial Silviculture: Cultivation of trees for sale (e.g., Christmas tree farm, trees raised for
                  lumber).

                  Major or Designated Recreation Area: A major recreation area is an area used by a large
                  number of people for recreational purposes (e.g., swimming or baseball). A designated
                  recreation area is an area designated and maintained by a government body (e.g. local, state,
                  Federal) as an area for public recreation.

            SCORING THE RESOURCES FACTOR

            (1)    Using the checklist In Highlight 10-11, determine if there are any commercial agricultural
                  or silvicultural areas, or major or designated recreation areas within 1/2 mile of a source
                  at the site. Use the above definitions in making this determination. Highlight 10-12 lists
                  examples of data sources for the resources factor.

            (2)    If any of these areas are present within 1/2 mile of a source with an air migration
                  containment factor value greater than 0, assign a resource factor value of 5. If none of
                  these areas is present within 1/2 mile of a source, or if the source has an air migration
                  containment factor of 0, assign a resource factor value of 0.
                                                   421
Commercial Agriculture:  ...crops for sale or
 trade...(e.g.,  local produce stands or traded
         within a Native community),...

      Commercial Silviculture:
          ...for sale or trade...
                         Major or Designated Recreation Area:
                       ...for recreational purposes (e.g., swimming,
                       ef baseball or Native American pow wows).
                         ...by a government body (e.g. local, state,
                                      tribe, or Federal)...
                                         Appendix 2 - page 4 of 5

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The following sources of information on possible surface water uses will help in documenting resource
use for a watershed:

       USGS topographic maps and land use data
       USDA county crop records and irrigated acreage data
       Field observations
       Interviews with water company officials
       Public utility trade association online services (e.g., American Water Works Association's
       WaterNet data base)
       Existing PA/SI reports for the site or nearby sites.
       Correspondence with nearby businesses
       Correspondence with other nearby institutions, such as farms or universities
       EPA's FRDS
       Agricultural extension agents
       Local chambers of commerce
       Federal, state,  or regional parks and recreation departments
       State public water supply offices (usually found in state departments of health or environment)
  —	State water cla55ification-afl44esignation maps
       Native American officials  ")
  ")	If a resource use-h> duumrrgnted, assign a value of 5 to the resources factor for the
       watershed; otherwise, assign a value of 0.
                                     HIGHLIGHT 8-45
                        CHECKLIST FOR THE RESOURCES FACTOR


 For the watershed being evaluated:

 (1)     Is surface water used to irrigate five or more acres of commercial food          Yes    No
        crops or commercial forage crops?

 (2)     Is surface water used to water commercial livestock?                        Yes    No


 (3)     Is surface water used as an ingredient in commercial food preparation?        Yes    No

 (4)     Is surface water used as, or used to supply, a major or designated water       Yes    No

        recreation area, excluding drinking water use?

 (5)     If.surface water Is not used for drinking water within the TDL, is any            Yes    No
        portion of the surface water designated by the state for drinking water
        use under Section 305(a) of the Clean Water Act, as amended, or is any
        portion usable  for drinking purposes?

 If the answer to any of the above questions is "yes", assign a resources factor value of 5. If the answer
 to all questions is "no", assign a resources factor value of 0.
                                            290
                                 Appendix 2 - page 5 of 5

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                                         Appendix  3
                  Include any drinking water well with an observed release attributed to the site, regardless
                  of its distance from the source.

                  Exclude wells completed in portions of an aquifer that are beyond an aquifer
                  discontinuity (see Section 7.1).

           Target Wells for Aquifer Being Evaluated: Wells that are located within the TDL, and drawing
           water from the aquifer being evaluated or an  overlying aquifer through which hazardous
           substances would migrate.	
         ^^_____

        f  Workers: Permanent employees (part-time or full-time) of a facility or business that is served by
        \a well located within the TDL.

    EVALUATING THE GROUND WATER POPULATION FACTOR

           The steps below describe an approach to estimating the population served by target wells for the
    aquifer being evaluated. First, contact water authorities that have wells within the TDL to determine or
    estimate the population served by municipal water systems. (See Highlight 7-32 for data needs that the
    water authority may be able to fulfill.) If the water authority provides an estimate of the population served
    by the system,  use that number for your ground water  target calculations. The water authority should
    know if the population served includes workers and/or students in addition to residents. If the population
    estimate does not include workers and/or students, it may be possible to modify the following
    methodology. The assumptions used should be clearly presented  in the documentation record.

           If the water authority provides just the total number of connections, then estimate the population
    served by multiplying the number of connections by the county average number of persons per
    household. After making an initial estimate of residential population served, estimate any student and
    worker populations served by the municipal system, and adjust the total. Next, evaluate residential
    populations served by private wells within the TDL. At  each stage, evaluate whether documenting
    additional population will be important to the site score.

           Depending on site circumstances, the scorer may conduct these steps in a different order. For
    example, if many people within the TDL use private wells or if private wells are subject to actual
    contamination, it may be more efficient to consider residential populations served by private wells
    before  considering  student or worker populations served by municipal connections.

    (1)     Draw target distance categories. Draw concentric rings with radii 1/4,1/2,1, 2, 3, and 4 miles
           on a topographic map from the edges of the source. If there is an aquifer discontinuity, exclude
           any areas beyond the discontinuity. Remember that any well  with a documented observed
           release attributable to the site is evaluated regardless of its distance from sources.

    (2)     Identity all  municipal systems with target wells for the aquifer being evaluated. Repeat
           Steps (3) through (5) for each system if more than one municipal system has wells within the
           TDL. If no municipal system has a well within the TDL, proceed to Step (7).

    (3)     Identify all system water supply units In the aquifer being evaluated or an overlying
           aquifer. These units may include drinking water wells and standby wells. If the municipal system
           is a blended system, identify all wells inside and outside the TDL. Also identify all surface water
           intakes and standby intakes contributing to a blended system.

    (4)     Evaluate the population served by the municipal water system, assuming all service
           connections are residential. Because connections to schools or businesses generally serve
           more individuals than those in a typical household, this assumption may result in a lower
           estimate of the target population. If this assumption yields a high score, however, time
           consuming inquiries to document student or worker populations may be avoided.
                                                165
Workers: ... 'Workers' include those working outdoors, as well as indoors.
                                    Appendix 3 - page 1 of 4

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Workers: ... 'Workers' include those working outdoors, as well as indoors.
           Workers:  Permanent employees (part-time or full-time) of a facility or business that is served by
           an intake within the TDL.

    EVALUATINGTHE DRINKING WATER POPULATION FACTOR

           The steps below describe an approach for estimating the population served by surface water
    intakes located within the TDL. First, estimate the population served by municipal water systems with
    intakes within the TDL. Contact municipal water authorities to obtain estimates of populations served.
    The water authority should know whether the population served includes workers and students in addition
    to residents.  If the population estimate does not include workers and/or students, modify the
    methodology presented below as necessary.Highlight 8-33 summarizes the information needed to
    obtain drinking water population estimates.
                                        HIGHLIGHT 8-33
               DATA NEEDS FOR DRINKING WATER THREAT POPULATION

     Obtain from Local, Municipal, or Other Water Authorities:

            Identification of all municipal surface water intakes located within the TDLs for surface water bodies in the
            watershed being evaluated;

            Number of persons saved or service connections for each intake that is not part of a blended system; and

            For intakes that are part of a blended system:

            —      Total population served or number of service connections;

            —     Total number of wells and intakes in the system (including those outside the TDL);

            —     Whether any wells or intakes are standby;

            —     Whether any well or intakes provides more than 40 percent of the system's water; and

            —     Average annual pumpage or capacity for each intake and well (only needed if one intake or well
                   provides more than 40 percent of the system's water).

     Obtain from Local, Municipal, or Other Water Authorities, or Local Health Agencies:

            Identification of private intakes located within the TDL; and

            Identification of schools and large businesses possibly served by intakes located within the TDL.

     Obtain from U.S. Bureau of Census Reports (or more recent source if appropriate):

            Average number of persons per residence for each county served by a system with intake located within
            the TDL.

     Obtain from Business and Schools:

            Information on how they obtain water; and

            Number of workers and/or students.
    Section 8.8                                    266
                                    Appendix 3 - page 2 of 4

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          SECTION 9.5
          WORKERS AND
          RESOURCES
                 This section provides guidance for evaluating workers and scoring the resources factor for the
          targets factor category in the resident population threat of the soil exposure pathway. The workers factor
          is used to score the targets factor category of the resident population threat. The scorer must consider
          the number of workers who frequent workplace areas on or near the area of observed contamination.
          The resources factor evaluates the possible loss of resource use resulting from surficial contamination at
          a site. The factor evaluates the presence of commercial agriculture, commercial  silviculture, commercial
          livestock production, and commercial livestock grazing; it does not evaluate threats to human health or
          sensitive environments.
                  Section 5.1.3
                  Section 5.1.3.3
                  Section 5.1.3.4
                  Section 5.1.3.6
RELEVANT MRS SECTION

 Targets
 Workers
 Resources
 Calculation of resident population targets factor category value
          DEFINITIONS
                 Commercial Agriculture: Production of crops for sale, including crops intended for widespread
                 distribution (e.g., supermarkets) and more limited distribution (e.g., local produce stands), and
                 any nonfood crops such as cotton and tobacco. Commercial agriculture does not include
                 livestock production, livestock grazing, or crops grown for household consumption (e.g.,
                 backyard garden or fruit trees).

                 Commercial Livestock Production or Commercial Livestock Grazing:  Raising or feeding of
                 livestock for sale.

                 Commercial Silviculture: Cultivation of trees for sale (e.g., Christmas tree farm, trees raised
                 for lumber).
                .-—-—"     ~                          \                              ~~
                 Worker: A person working on a property with an area of observed contamination and whose
                 workplace  area is on or within 200 feet of an area of observed contamination. Both full and
                 part-time workers are considered.

                 Workplace Area: Any area where workers are regularly present. Areas receiving only brief but
                 regular use (e.g.,  parking areas, lunch areas) may qualify as work areas.
                                                   371
  Worker: ...'Workers' include
those working outdoors, as well
            as indoors.
             Workplace Area: ...  'Workplace        include
                    those outdoors, as well as indoors.
                                        Appendix 3 - page 3 of 4

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           Nearest Individual:  Factor evaluated based on the presence of actual contamination or, for
           potential contamination, the shortest distance from any source at the site to any residence or
           regularly occupied building or area.

           Population for the Air Migration Pathway:  Number of residents, students, and workers
           regularly present within the TDL. This population does not include transient populations, such as
           hotel and restaurant patrons, but may include seasonal populations (e.g., a resort area).

           Students: Full- or part-time attendees of an educational institution or day care facility located
           within the TDL.

           Target Distance Limit for the Air Migration Pathway:  Distance over which population and
           other targets are evaluated. The TDL generally is a 4-mile radius from the sources at the site.
           However, if a sampling point meeting the criteria for an observed release is located beyond the
           4-mile radius, that point defines the outer boundary of the TDL. For example, if an observed
           releaseis established 6 miles from the source, the TDL is 6 miles.	   	
          ,-	'     ~~                                                           ~~     '
           Workers:  Permanent employees (part-time or full-time) of a facility or business that is located
           within the TDL.

    DETERMJMWJLhVhLOFACIUALCUNIAMINAIlUN	

           In order to evaluate level of actual contamination, an observed release should first be
    established (see Section 10.1 for establishing observed releases in the air pathway). If an observed
    release to air is established in or beyond a distance category, actual contamination is also established for
    that distance category and the level of contamination for the observed release location needs to be
    determined. The steps below explain how to determine if a location is evaluated  as Level I or Level II.

    (1)    Determine whether an observed release can be established for any hazardous substance
           detected in air samples or based on direct observation. See  Section  10.1 for information on
           establishing an observed release.

           •      If an observed release is established only by direct observation,  Level I cannot be
                  established and all locations for the direction observation are Level II. Continue with the
                  guidance in the next subsection, Evaluating Sites with Actual Contamination.

           •      If an observed release is established based on chemical analysis, continue to Step (2).

           •      If no observed release can be established, evaluate the  entire population within the 4-
                  mile TDL for potential contamination.

    (2)    For each sample location, compare the concentration of each hazardous substance that
           meets the observed release criteria to its applicable benchmark(s). When comparing
           sampling results to benchmarks, concentrations from longer collection times may be compared
           to snorter time-frame benchmarks, but concentrations from shorter collection times may not be
           compared to longer time-frame benchmarks. Sample concentrations tend to decrease as
           sampling time increases (e.g., 8-hour concentrations generally are lower than 3-hour
           concentrations). Applicable benchmarks (available in SCDM) for hazardous substances include:

                  NAAQS;

                  NESHAPs;

           •      Screening concentrations for cancer, which correspond to the Iff individual cancer risk
                  for inhalation exposure; and

    Section 10.3                                  412
Workers: ... 'Workers' include those working outdoors, as well as indoors.
                                    Appendix 3 - page 4 of 4

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                                      Appendix 4
    SECTION 7.5
    POPULATION  AND
    NEAREST WELL  FACTORS
           The population factor in the ground water pathway evaluates the number of residents, students,
    and workers served by ground water wells (in the aquifer being evaluated and appropriate overlying
    aquifers) located within the TDL. The nearest well factor evaluates the threat to the maximally exposed
    individual and takes into account whether that individual is subject to actual or potential contamination.
    This section explains how to estimate the population (i.e., residents, students, and workers) that regularly
    uses ground water from wells within the TDL, how to score the ground  water population factor, and how
    to score the nearest well factor.

           The ground water population includes the people served by wells located within the TDL, not the
    residents living within the TDL (see Highlight 7-31). People living within the TDL may obtain drinking
    water from wells outside the TDL or from surface water sources, and people living outside the TDL may
    obtain drinking water from wells located within the TDL.
                                RELEVANT MRS SECTIONS


             Section 3.0.1          General considerations
             Section 3.0.1.1         Target distance limit
             Section 3.3.1          Nearest well
             Section 3.3.2          Population
    DEFINITIONS
           Nearest Well Factor: Factor for evaluating the maximally exposed well. This factor is based on
           the presence of actual contamination or, for aquifers where no drinking water well is subject to
           actual contamination, the presence of karst and distance to nearest drinking water well.
          ^—„«.*•.— __
           Population for the Ground Water Pathway: Number of residents, students, and workers
           regularly served by wells that are located within the TDL for the aquifer being evaluated (and
           appropriate overlying aquifers). This population does not include transient populations, such as^
           hotel and restaurant patrons, but may include seasonal populations (e.g., a resort area).

           Students: Full- or part-time attendees of an educational institution or day care that is served by
           a well located within the TDL.

           Target Distance Categories: Concentric rings (not necessarily circular) with radii  1/4,1/2, 1, 2,
           3, and 4 miles from the sources at the site. These distance categories are used to group the
           wells subject to potential contamination for distance weighting.

           Target Distance Limit for the Ground Water Migration Pathway: The distance over which
           targets are evaluated. The TDL is generally a 4-mile radius from sources at the site, except:
                                             163
                                                                                  Section 7.5
Population for the Ground Water Pathway: ... but may include seasonal
populations (e.g., a resort area or seasonal tribal camp or work       population).
                                  Appendix 4 - page 1 of 3

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     SECTION 8.8
     POPULATION AND
     NEAREST INTAKE
     FACTORS
-VK*H
           The population factor in the drinking water threat evaluates the number of residents, students,
     and workers regularly served by surface water intakes within the TDL for the watershed being evaluated.
     This evaluation is essentially the same as that for the ground water pathway, except that surface water
     intakes are considered instead of drinking water wells. This section also briefly discusses the nearest
     intake factor.
                               RELEVANT MRS SECTIONS

            Section 4.1.1.2        Target distance limit
            Section 4.1.2.3.1       Nearest intake
            Section 4.1.2.3.2       Population
     DEFINITIONS
           Dilution Weight:  A unitless parameter that adjusts the assigned point value for certain targets
           subject to potential contamination as a function of the flow or depth of the water body at the
           target.

           Nearest Intake Factor:  Factor for evaluating the maximally exposed intake. This factor is
           based on the presence of actual contamination or, for watersheds where no intake is subject to
           actual contamination, the flow or depth of the water body at the intake nearest to the PPE within
           the TDL.
          ——.  -                                                       —
           Population for the Drinking Water Threat:  Number of residents, students, and workers
           regularly served by surface water intakes that are located within the TDL for the surface water
           bodies evaluated for a given watershed. This population does not include transient populations,
           such as hotel and restaurant patrons, but may include seasonal populations (e.g., a resort area)^
          —'	•—
           Students: Full- or part-time attendees of an educational institution or day care facility that is
           served by an intake located within the TDL.

           Target Distance Limit (TOIL) for the Surface Water Migration Pathway: Distance over which
           the in-water segment of the hazardous substance migration path is evaluated. The TDL extends
           15 miles from the PPE in the direction of flow (or radially in lakes, oceans, or coastal tidal
           waters) or to the most distant sample point establishing an observed release, whichever is
           greater. In tidally influenced surface water bodies, an upstream TDL is also determined. For
           some sites (e.g., sites with multiple PPEs), an overall target distance of greater than 15 miles
           may result.
                                            265
Population for the Drinking Water Threat: ... but may include seasonal
populations (e.g., a resort area or seasonal tribal camp or work      population).
                                 Appendix 4 - page 2 of 3

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Population for the Air Migration Pathway: ... but may include seasonal
populations (e.g., a resort area or seasonal tribal camp or work       population).
            Nearest Individual: Factor evaluated based on the presence of actual contamination or, for
            potential contamination, the shortest distance from any source at the site to any residence or
            regularly occupied building or area.	
           .---—"~~~~~   —
            Population for the Air Migration Pathway:  Number of residents, students, and workers
            regularly present within the TDL. This population does not include transient populations, such as
            hotel and restaurant patrons, but may include seasonal  populations (e.g., a resort area).
           		
            Students: Full- or part-time attendees of an  educational institution or day care facility located
            within the TDL.

            Target Distance Limit for the Air Migration Pathway:  Distance over which population and
            other targets are evaluated. The TDL generally is a 4-mile radius from the sources at the site.
            However, if a sampling point meeting the criteria for an observed release is located beyond the
            4-mile radius, that point defines the outer boundary of the TDL. For example, if an observed
            release is established 6 miles from the source, the TDL  is 6 miles.

            Workers:  Permanent employees (part-time or full-time) of a facility or business that is located
            within the TDL.

     DETERMINING LEVEL OF ACTUAL CONTAMINATION

            In order to evaluate level of actual contamination, an observed release should first be
     established (see Section 10.1 for establishing observed releases in the air pathway). If an observed
     release to air is established in or beyond a distance category, actual contamination is also established for
     that distance category and the level of contamination for the observed release location needs to be
     determined. The steps below explain how to determine if a location is evaluated  as Level I or Level II.

     (1)     Determine whether an  observed release can be established for any hazardous substance
            detected in air samples or based on direct observation. See Section 10.1 for information on
            establishing an observed release.

                   If an observed release is established only by direct observation, Level I cannot be
                   established and all locations for the direction observation are Level II. Continue with the
                   guidance in the  next subsection, Evaluating Sites with Actual Contamination.

                   If an observed release is established based on chemical analysis, continue to Step (2).

                   If no observed release can be established, evaluate the entire population within the 4-
                   mile TDL for potential contamination.

     (2)     For each sample location, compare the concentration of each hazardous substance that
            meets the observed release criteria to its applicable  benchmark(s). When comparing
            sampling results to benchmarks, concentrations from longer collection times may be compared
            to shorter time-frame benchmarks, but concentrations from shorter collection times may not be
            compared to longer time-frame benchmarks. Sample concentrations tend to decrease as
            sampling time increases (e.g., 8-hour concentrations generally are lower than 3-hour
            concentrations). Applicable benchmarks (available in SCDM) for hazardous substances include:

                   NAAQS;

                   NESHAPs;

                   Screening concentrations for cancer, which correspond to the 1Cf individual cancer risk
                   for inhalation exposure; and

     Section 10.3                                   412
                                    Appendix 4 - page 3 of 3

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                                     Appendix 5
SCORING THE LIKELIHOOD OF EXPOSURE FACTOR CATEGORY

       To score the likelihood of exposure factor category for the nearby population threat, determine
the attractiveness/accessibility factor value and the area of contamination factor value for the areas of
observed contamination as follows.

(1)    Assign the attractiveness/accessibility factor value. Assign each area of observed
contamination a value for attractiveness/accessibility, excluding any area of observed contamination on
a residential property. If an area falls into two or more categories, use the higher score. Select the
highest value assigned to the areas evaluated and use it as the attractiveness/accessibility factor value
for the site. If the attractiveness/accessibility factor value fora site is 0, the nearby population threat
score will be 0.
      „—-—  ~    ~""~~    "~
       Highlight 9-21, which is based on HRS Table 5-6, provides attractiveness/accessibility factor'
       values along with examples of the types of areas that would receive a given value. Public
       recreation use can be activities such as walking, sports, fishing, air shows, and hayrides, and can
       occur on public or private lands.  The examples presented mHighlight 9-21 are not exhaustive.
       Select the best-fitting category and document why it was selected.

(2)    Determine the area of contamination factor value. The area of contamination factor value is
       based on the total area of all areas of observed contamination at the site with an
       attractiveness/accessibility factor value greater than 0. To determine the area of contamination
       factor value:

       •      Identify all areas of observed contamination with an attractiveness/accessibility value
              greater than 0.

       •      Determine their total area.

              Assign the approximate area of contamination factor value using HRS Table 5-7.

       Section 9.1  provides instruction on identifying areas of observed contamination.

(3)    Determine the likelihood of exposure factor category value. The likelihood of exposure
       factor category value is based on the values assigned to the attractiveness/accessibility and area
       of contamination factors. Use HRS Table 5-8 to assign this value. The maximum value is 500.

SCORING WASTE CHARACTERISTICS FACTOR CATEGORY

       The waste characteristics factor category for the nearby population threat is scored as it is  scored
for the resident population threat, except that the nearby threat considers only those areas of observed
contamination that have an attractiveness/accessibility factor value greater than 0. The waste
characteristic factor category value for the nearby population threat, therefore, will be equal to or less
than that for the resident population threat. Section 9.2 provides guidance on scoring the waste
characteristics factor.

SCORING TARGETS FACTOR CATEGORY

       The targets factor category value for the nearby population threat is based on two factors: nearby
individual and population within a one-mile travel distance from the site. Sum these two factor values for
the targets factor category value.
                                           390
   Highlight 9-21,... Public recreation use can be activities such as  ...,
                          Native American powwows, ...
                                Appendix 5 - page 1  of 2

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HIGHLIGHT 9-21
EXAMPLES OF ATTRACTIVENESS/ACCESSIBILITY VALUES
Area of Observed Contamination
Designated recreational areas
Includes areas designed specifically to encourage recreational use.
Playground
Golf course (public or private)
Baseball field with backstop and maintained basepaths or infield
Areas with Improvements aimed at enabling people to view scenic attractions
Areas regularly used for public recreation
Includes areas used regularly for public recreation but not designated for such use.
Open fields where people play frisbee
Fields where people play baseball (provided that they are not maintained for
such use)
Accessible and unique recreational areas
Vacant lot in an urban area
Shoreline of stream in an urban area
Moderately accessible areas with some public recreation use
Includes areas used for recreation with some improvements that increase accessibility
even if these improvements are not made specifically for the areas In question.
Undeveloped land along corridors to a recreational area where there are not
thousands of acres of similarly undeveloped land (e.g., areas adjacent to a road
or trail leading to a public lake or river)
• Shoreline of public lakes or rivers that can be reached via moderately improved
roads (e.g., gravel or dirt)
Slightly accessible areas with some public recreation use
Includes areas used for public recreation but with few improvements that increase
accessibility to the areas. It can also include areas that have nothing unique about them
relative to their surroundings.
• Shorelines of relatively remote public lakes (e.g., lakes that cannot be reached
by automobile)
• Undeveloped land along corridors to a recreational area where there are
thousands of other acres of similarly undeveloped land along the corridor
Accessible areas with no public recreation use
Unfenced industrial or commercial site (guarded or not) with no vacant lots,
sand piles, or other recreational attractions
Abandoned lagoons or other surface impoundments in an industrial area
Areas surrounded by maintained fence or combination of maintained fence and
natural barriers
• Fenced, unguarded industrial or commercial sites
Areas physically inaccessible to public, with no evidence of public recreation use
Includes areas where (1) steps have been taken to absolutely preclude public access to
the areas or (2) natural conditions make access physically impossible.
• Area off-limits to unauthorized personnel at guarded and fenced military base or
industrial complexes.
Assigned
Value
100
75
75
50
25
10
5
0


                                    391
                                                                Section £
Designated recreational areas...
•  Community gathering       such as Native American
pow wow grounds
                             Appendix 5 - page 2 of 2

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