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
-------
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
-------
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.
-------
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
ill Contents
-------
CONTENTS (continued)
Page
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
-------
CONTENTS (continued)
Page
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
-------
CONTENTS (continued)
Page
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
-------
CONTENTS (continued)
Page
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
Vll Contents
-------
CONTENTS (continued)
Page
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
-------
CONTENTS (continued)
Page
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
ix Contents
-------
CONTENTS (continued)
Page
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
-------
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
-------
HIGHLIGHTS
Page
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
Xiii Highlights
-------
HIGHLIGHTS (continued)
Page
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
Highlights
XIV
-------
CHAPTER 7
Highlight 7-1:
Highlight 7-2:
Highlight 7-3:
Highlight 7-4:
Highlight 7-5:
Highlight 7-6:
Highlight 7-7:
Highlight 7-8:
Highlight 7-9:
Highlight 7-10:
Highlight 7-11:
Highlight 7-12:
Highlight 7-13:
Highlight 7-14:
Highlight 7-15:
Highlight 7-16:
Highlight 7-17:
Highlight 7-18:
Highlight 7-19:
Highlight 7-20:
Highlight 7-21:
Highlight 7-22:
Highlight 7-23:
HIGHLIGHTS (continued)
Page
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
Highlights
-------
Highlight 7-24:
Highlight 7-25:
Highlight 7-26:
Highlight 7-27:
Highlight 7-28:
Highlight 7-29:
Highlight 7-30:
Highlight 7-31:
Highlight 7-32:
Highlight 7-33:
Highlight 7-34:
Highlight 7-35:
Highlight 7-36:
Highlight 7-37:
Highlight 7-38:
Highlight 7-39:
Highlight 7-40:
Highlight 7-41:
Highlight 7-42:
Highlight 7-43:
Highlight 7-44:
Highlight 7-45:
Highlight 7-46:
Highlight 7-47:
HIGHLIGHTS (continued)
Page
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
-------
CHAPTER 8
Highlight 8-1:
Highlight 8-2:
Highlight 8-3:
Highlight 8-4:
Highlight 8-5:
Highlight 8-6:
Highlights-?:
Highlight 8-8:
Highlight 8-9:
Highlight 8-10:
Highlight 8-11:
Highlight 8-12:
Highlight 8-13:
Highlight 8-14:
Highlight 8-15:
Highlight 8-16:
Highlight 8-17:
Highlight 8-18:
Highlight 8-19:
Highlight 8-20:
HIGHLIGHTS (continued)
Page
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
Highlights
-------
HIGHLIGHTS (continued)
Page
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
-------
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
Highlight 8-46:
Highlight 8-47:
Highlight 8-48:
Highlight 8-49:
Highlight 8-50:
Highlight 8-51:
Highlight 8-52:
Highlight 8-53:
Highlight 8-54:
Highlight 8-55:
Highlight 8-56:
Highlight 8-57:
Highlight 8-58:
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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.
1 7 Chapter 2
-------
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
Chapter 2 1 8
-------
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.
1 9 Chapter 2
-------
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.
Chapter 2 20
-------
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.
21 Chapters
-------
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.
Chapter 3 22
-------
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.
23 Chapter 3
-------
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
-------
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.
25 Chapter 3
-------
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
Chapter 3 26
-------
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:
27 Chapter 3
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
CHAPTER 4
SOURCES
Contaminated
So
Surface
Impoundment
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
SECTION 5.1
ESTABLISHING AN
OBSERVED RELEASE
AND OBSERVED
CONTAMINATION
HHMwRlwNMI
* ;
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
(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
-------
CHAPTER 6
HAZARDOUS WASTE QUANTITY
TIER A
TIERB
TIERC
HERD
HAZARDOUS CONSTITUENT
QUANTITY
HAZARDOUS WASTESTREAM
QUANTITY
VOLUME
AREA
POUNDS
POUNDS
CUBIC YARDS
SQUARE FEET
-------
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
-------
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).
-------
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
-------
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
-------
(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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
(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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
(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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
(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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
(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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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 stationsone 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
-------
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
-------
(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
-------
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
-------
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
-------
(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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
(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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
(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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
(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
-------
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
-------
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
-------
(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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
(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
-------
(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
-------
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
-------
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
-------
(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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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).
337
Section 8.16
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
(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
-------
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
-------
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
-------
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
-------
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 individualsthe 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 individualsthe 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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
(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
-------
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
-------
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
-------
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
-------
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
-------
(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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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.
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
APPENDIX A
SENSITIVE ENVIRONMENTS
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
(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
-------
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
-------
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
-------
(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
-------
(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
-------
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
-------
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
-------
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
-------
(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
-------
(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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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.
-------
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:
-------
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
-------
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
-------
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.
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
------- |