Hazard Ranking System Issue Analysis:
 Options for Revising the Air Pathway
                MITRE

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Hazard  Ranking  System  Issue Analysis:
 Options  for  Revising the Air Pathway
                  Thomas F. Wolfinger
                     August 1987
                      MTR-86W53
                       SPONSOR:
                U.S. Environmental Protection Agency
                     CONTRACT NO.:
                      EPA-68-01-7054
                   The MITRE Corporation
                    Civil Systems Division
                     7525 Colshire Drive
                   McLean, Virginia 22102-3481

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  Department Approval:
MITRE Project Approval:
                            ii

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                              ABSTKACT
     This report presents two options for revising the air pathway
of the EPA Hazard Ranking System (HRS).   The HRS is used by EPA to
rank uncontrolled wastes sites based on their relative threat to
human health and the environment.  Highly ranked sites are placed on
the National Priorities List for further investigation and possible
remedial action.  The options focus on the incorporation of a
"potential-to-release" option within the HRS air pathway.   Inclusion
of such an option would make the air pathway consistent with the
other HRS migration pathways.  The options also include recommended
changes to other components of the air pathway to increase the
ability of the HRS to discriminate the threat between sites.   These
changes arise from an analysis of weaknesses in the HRS and advances
in the science of air emissions from hazardous wastes sites.

Suggested Keywords:  Superfund, Hazard ranking, Hazardous  waste,  Air
emissions.
                                 iii

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                          TABLE  OF  CONTENTS
                                                                 Page

LIST OF ILLUSTRATIONS                                            vii
LIST OF TABLES                                                  viil

1.0  INTRODUCTION                                                  1

I.I  Background                                                    1
1.2  Issue Description                                             3
1.3  Organization of Report                                        5

2.0  OVERVIEW OF AIR POLLUTION FROM HAZARDOUS WASTES SITES          7

2.1  Emission Processes                                            7
2.2  Factors Determining Emission Rates and Duration               9
2.3  Contaminant Transport and Transformation                     13

3.0  ISSUES IN THE HRS AIR PATHWAY                                19

3.1  Background on the Hazard Ranking System                      19
3.2  Issues in the Current HRS Air Pathway                        22
3.3  Options for Revising the HRS Air Pathway                     30

4.0  MULTIPLE SOURCE, PROBABILISTIC APPROACHES                    31
     (OPTIONS 1 AND 1A)

4.1  Release Category                                             33

     4.1.1  Observed Release                                      34
     4.1.2  Potential to Release                                  41

4.2  Waste Characteristics Category                               78
4.3  Targets Category                                             81
4.4  The Overall Pathway Score                                    86

5.0  SINGLE, "WORST" SOURCE APPROACH (OPTION 2)                   89

5.1  The Option 2 Potential to Release Evaluation Mechanism       90

     5.1.1  Emission Source Descriptors                           93
     5.1.2  Contaminant Mobility                                  97
     5.1.3  Containment                                           99

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                    TABLE OF  CONTENTS  (Concluded)


                                                                 Page

6.0  IMPLICATIONS                                                105

6.1  Improvements in the HRS and the NPL                         105
6.2  Cost Implications                                           107
6.3  Potential Implications for Other HRS Pathways               109

7.0  SUMMARY AND CONCLUSIONS                                     111

8.0  REFERENCES AND BIBLIOGRAPHY                                 113

8.1  Selected References on Emission Processes                   113
8.2  Selected References Addressing Air Monitoring Guidance      114
8.3  Principal References Used in Developing Containment         115
     Factors
8.4  General Bibliography                                        116

APPENDIX A - SUMMARY OF AIR MONITORING DATA AT SELECTED          141
             WASTES SITES

APPENDIX B - DISCUSSION OF REJECTED OPTIONS                      147

APPENDIX C - STEP-BY-STEP INSTRUCTIONS AND EXAMPLES              181

APPENDIX D - ADDITIONAL TABLES                                   229
                                 vi

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                       LIST OF ILLUSTRATIONS






Figure Number                                                   Page




     1          Basic HRS Structure                              23




     2          Map of PE Index for State Climatic  Divisions      70
                                vii

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                           LIST OF TABLES


Table Number

     1         Ambient Air Monitoring Results for Selected        10
               Wastes Sites

     2         Atmospheric Residence Times for Selected           16
               Contaminants Detected at Hazardous Wastes
               Sites

     3         Ranges of Estimated Levels of Organic Vapors       17
               in Ambient Air of Household Basements in
               Niagara Falls, NY

     4         HRS Scoring Factors                                21

     5         Overview of Important Features of Air              32
               Pathway Options 1 and LA

     6         Site Conditions That Make It Difficult to          40
               Demonstrate an Observed Release

     7         Time Needed for 75 Percent of Selected Compounds   44
               to Volatilize for Various Disposal Methods

     8         Data on Mobility of Phenol and Dichloroethylene    46

     9         Option 1 Emission Source Descriptors               50

     10         Option 1A Emission Source Descriptors              52

     11         Option 1 Size Ranges                               55

     12         Option LA Size Ranges                              57

     13         Option 1 Emission Source Descriptors and Values    60

     14         Option 1A Emission Source Descriptors and Values   62

     15         Gas Mobility Values                                64

     16         Method for Evaluating Gas Mobility                 66

     17         Alternate Metnod for Assigning Particulate         71
               Mobility Factor Values
                                viii

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                     LIST OF TABLES (Concluded)


Table Number                                                     Page

    18         Combined Mobility Factor Matrix                    73

    19         Examples of Containment Factors and Values          75

    20         Combined Containment Factor Matrix                 76

    21         Method of Calculating Overall Site Release          79
               Value

    22         Combined Toxicity-Mobility Factor Matrix           82

    23         Current HRS Target Population Factor Matrix        84

    24         Method of Calculating Air Pathway Score            87

    25         Illustration of Option 2 Potential to Release       92
               Evaluation Procedure

    26         Option 2 Emission Source Descriptors and           94
               Definitions

    27         Option 2 Minimum Size Requirements                 95

    28         Option 2 Emission Source Descriptor Values          96

    29         Option 2 Particulate Mobility Factor               98

    30         Option 2 Particulate Containment  Factors          100

    31         Option 2 Gas Containment Factors                   102

    32         HRS Scoring Distribution for "Marginal" Sites      108
               Lacking Observed Air Releases
                                 ix

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1.0  INTRODUCTION




1.1  Background




     The Comprehensive Environmental Response, Compensation,  and




Liability Act of 1980 (CERCLA) (PL 96-510) requires the President to




identify national priorities for remedial action among releases or




threatened releases of hazardous substances.   These releases  are to




be identified based on criteria promulgated in the National




Contingency Plan (NCP).  On July 16, 1982, EPA promulgated the




Hazard Ranking System (HRS) as Appendix A to the NCP (40 CFR  300;




47 FR 31180).  The HRS comprises the criteria required under  CERCLA




and is used by EPA to estimate the relative potential hazard  posed




by releases or threatened releases of hazardous substances.




     The HRS is a means for applying uniform technical judgment




regarding the potential hazards presented by a release relative to




other releases.  The HRS is used in identifying releases as national




priorities for further investigation and possible remedial action by




assigning numerical values (according to prescribed guidelines) to




factors that characterize the potential of any given release  to




cause harm.  The values are manipulated mathematically to yield a




single score that is designed to indicate the potential hazard posed




by each release relative to other releases.  This score is one of




the criteria used by EPA in determining whether the release should




be placed on the National Priorities List (NPL).

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     During the original NCP rulemaking process  and the  subsequent

application of the HRS to specific releases,  a number  of technical

issues have been raised regarding the HRS.  These issues concern the

desire for modifications to the HRS to further improve its

capability to estimate the relative potential hazard of  releases.

The issues include:

     •  Review of other existing ranking systems suitable for
        ranking hazardous waste sites for the NPL.

     •  Feasibility of considering ground water  flow direction and
        distance, as well as defining "aquifer of concern,"  in
        determining potentially affected targets.

     •  Development of a human food chain exposure evaluation
        methodology.

     •  Development of a potential for air release factor category
        in the HRS air pathway.

     •  Review of the adequacy of the target  distance  specified in
        the air pathway.

     •  Feasibility of considering the accumulation of hazardous
        substances in indoor environments.

     •  Feasibility of developing factors to  account for
        environmental attenuation of hazardous substances in ground
        and surface water.

     •  Feasibility of developing a more discriminating  toxicity
        factor.

     •  Refinement of the definition of "significance" as it relates
        to observed releases.

     •  Suitability of the current HRS default value for an unknown
        waste quantity.

     •  Feasibility of determining and using  hazardous substance
        concentration data.

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     •  Feasibility of evaluating waste quantity on a hazardous
        constituent basis.

     •  Review of the adequacy of the target distance specified in
        the surface water pathway.

     •  Development of a sensitive environment evaluation
        methodology.

     •  Feasibility of revising the containment factors to increase
        discrimination among facilities.

     •  Review of the potential for future changes in laboratory
        detection limits to affect the types of sites considered for
        the NPL.

     Each technical issue is the subject of one or more separate but

related reports.  These reports, although providing background,

analysis, conclusions and recommendations regarding the technical

issue, will not directly affect the HRS.  Rather,  these reports will

be used by an EPA working group that will assess and integrate  the

results and prepare recommendations to EPA management regarding

future changes to the HRS.  Any changes will then be proposed in

Federal notice and comment rulemaking as formal changes to the  NCP.

The following section describes the specific issue that is the

subject of this report.

1.2  Issue Description

     Several issues relevant to the HRS air pathway have been raised

by Congress and by public comments on the NPL and  NPL rulemaking

actions.  Some of these issues have been the subject of discussions

in Congress as it debates extending and revising CERCLA.   Because of

these comments and discussions, EPA has decided to re-examine the

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desirability and feasibility of including an option within the air




pathway release category that would allow sites lacking data




documenting a release of contaminants into the air, to be scored




based on their "potential to release".  Currently, the air pathway




is  scored only when a release of air contaminants into the atmosphere




can be documented.  The inclusion of such an option would make the




structure of the air pathway consistent with both the ground water




and surface water pathways.




     The principal purpose of this report is to define alternate




mechanisms for scoring sites for the air pathway.  The principal




emphasis is on modifications to allow sites to be scored based on




their potential to release CERCLA contaminants into the air, in the



absence of observed releases.  The approach embodied in the options




is  different from that used in the other HRS migration pathways.




The approach is based on the use of subjective probability to assess




the potential of a site to release a significant quantity of




contaminant as indicated by selected physical characteristics of the




site.  Additional modifications were investigated that arose either



as  logical extensions of the potential to release modifications or




from perceived weak points in the HRS as discussed by commenters.




Overall, the intent is to provide options that would generally




improve the degree to which the HRS reflects the potential threat




from uncontrolled waste sites.   This report also addresses the




additional  costs that would be associated with the incorporation of

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such a mechanism in the HRS.  Additionally, the report addresses




limited testing of the options for validity, feasibility and




completeness.




     The report presents the options and supporting documentation to




EPA to assist the Agency in determining if and how it would modify




the air route of the HRS.




1.3  Organization of Report




     The body of the report is organized in six main sections with




accompanying appendices.  Section 2 presents an overview of the




phenomena of air pollution from waste sites.  Section 3 presents an




overview of the HRS and discusses the principal air pathway issues




addressed by the options.  Section 4 discusses two multiple source,




probabilistic approaches to evaluating potential to release, as well




as other proposed revisions to the air pathway.  The options




discussed in this chapter constitute alternate air pathways.  A




simple, single-source potential to release option is discussed in




Section 5.  Section 6 discusses the implications for the HRS and NPL




as well as program costs that might arise if the revision options




are adopted.  Section 7 presents a summary of the options and




recommendations on revising the HRS air pathway.




     Appendix A presents summaries of the limited data available




on air contaminant emissions from waste sites.  A discussion of




revision options that were rejected during the study is presented




in Appendix B.  Appendix C presents step-by-step instructions for

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employing the most complex option (Option 1),  as well as  an example




of its application to a hypothetical site.   This appendix also




contains an example of the application of the  simpler option




(Option 2) to the same site.   Appendix D contains definitions of the




basic emission source descriptors used in the  options, as well as




detailed containment factor descriptors for Options 1 and 1A.

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2.0  OVERVIEW OF AIR POLLUTION FROM HAZARDOUS WASTES SITES




     A review of the processes that could result in the release of




air contaminants from waste disposal sites leads to the conclusion




that nearly all disposal facilities either currently emit, have




emitted, or will emit air pollutants.  The exceptions are those




sites whose containment is such that it forms (and will continue to




form) an impermeable barrier between the contaminants and the




atmosphere.  Whether the pollutants are emitted in sufficient



concentration to merit concern, or even be detected, depends on




numerous site-specific factors.




     The following discussion presents an overview of current




knowledge about emissions from uncontrolled hazardous wastes sites.




The discussion is intended to provide background information




pertaining to the options presented in Sections 4 and 5.   A list of




the principal references supporting this discussion is presented in




Section 8.1.




2.1  Emission Processes




     Once wastes are deposited in a site, they become subject to




numerous physiochemical processes.  Some of these processes result




in the creation of new contaminants.  Other processes, arising from




the pressure within the waste system to achieve equilibrium with the




environment, can cause contaminants to migrate through pores in




the soil, or diffuse through liquids, resulting in a release of




contaminants from the site.  The contaminants may then escape into

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the atmosphere, if conditions are suitable, through processes such as




volatilization or particle suspension.  Emissions can occur directly




from the site itself or after transport off-site in ground water or




surface water.




     Two general types of air contaminants are emitted from waste




disposal sites:  gases and participate matter.  Gases may be organic,




such as methane or chloroform, or inorganic, such as hydrogen




sulfide.  Gaseous emissions may arise as a result of volatilization




of liquids such as benzene or toluene, or from reactions involving




chemicals disposed of on the site (e.g., the formation of hydrogen




sulfide).  A less common source of gaseous emissions is gas




containers disposed of on the site.  In general, the volatilization




of organic liquids is the most common source of gaseous emissions




from disposal sites, although at least one death has occurred from




exposure to gases generated as a result of the interaction of




improperly co-disposed chemicals.




     Like gases, particulate contaminants may be either organic or




inorganic.  The particulate matter itself may pose a hazard, as in




the case of asbestos particles.  Alternately, a hazardous compound




can be absorbed or adsorbed onto the particle.  The principal




factors responsible for particulate emissions from wastes sites are




wind and atmospheric turbulence.  They can result in resuspension of




surface soil and particulate wastes, and the release of liquid




aerosols.  Escaping gases may also carry contaminated particles




with them.




                                  8

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     Table 1 summarizes the result of ambient air monitoring studies

conducted around several wastes disposal sites.   Additional

monitoring data are summarized in Appendix A.  As can be seen from

Table 1, ambient concentrations of many hazardous substances are

elevated in the areas surrounding major wastes sites.  These elevated

hydrocarbon concentrations indicate that uncontrolled wastes sites

may have an adverse impact on the surrounding atmospheric

environment.  Further, they indicate, as well, the potential hazard

associated with air emissions from wastes sites.  As an example, the

benzene concentrations listed for Love Canal are equivalent to a
                                _3
lifetime probability of about 10   that a continuously exposed

individual will develop cancer due to the exposure.*

2.2  Factors Determining Emission Rates and Duration

     The rate and duration of particulate and gaseous emissions are

influenced by many factors.  The importance of each factor differs

from site to site.  Two general categories of factors can be

identified:  the physical characteristics of the site and the nature

of the wastes in the site.  Within the first category, the most

important and easily assessed factors that distinguish the relative
*The benzene risk values are based on a benzene potency factor of
 7.4 x 10   per (ug/m ).  This value assumes that the exposed
 individual weighs 70 kilograms, breathes 20 cubic meters of
 contaminated air per day continuously for 70 years.   These
 assumptions are derived taken from the approach suggested for use
 in CERCLA public health evaluations (U.S. Environmental Protection
 Agency, 1986).  The risk value is intended solely to illustrate
 the degree of risk that may be associated with exposure to the
 concentrations of certain waste site contaminants.

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                                              TABLE  1

                      AMBIENT AIR MONITORING RESULTS FOR  SELECTED WASTES SITES
Site
Type of Kin Buc
Contaminant (ng/m3)
Benzene

Carbon 111-13687
Tetrachloride
Chlorobenzene T-1127

Chloroform T-6389

Chi oro toluene
Dichloro- T-33783
benzene
(o,m,p)
Love Canal Sylvester Midco I BKK
(ug/m3) (ppb) (ppb) (ppb)
522.7 0.03-3.56 10-2000*
270.0 3.0-4.8
5.0

0.1-172 ND-500*
240.0
0.5-24.0 10.0 5100
0.2-1.0
0.008-7650
0.3-100.5


Chem Dyne
(ppb)
19.2











*ppm
**ug/m3
 T:  Trace.
ND:  Not detected.

Source:  Adapted from James, Kinman, and Nutini, 1985,

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                                       TABLE 1  (Continued)
   Type of
 Contaminant
 Kin Buc
 (ng/m3)
                                                     Site
Love Canal
 (ug/m3)
Sylvester
  (ppb)
 Midco I
  (ppb)
 BKK
(ppb)
Chem Dyne
 (ppb)
 1,1-Dichloro-
   ethane

 1,2-Dichloro-
   ethane

 1,2-Dichloro-
   ethylene

 Ethlybenzene

 Methylene
   Chloride

 Tetrachloro-
   ethane

 Tetrachloro-
   ethylene
364-470
T-2173
T-5263
T-1000


 32-54


T-2896
  334
0.7-11.6
 1140
0.2-52
  95.0
0.03-0.43

0.03-4.89
              0.04-0.24
              1.4-3.7
                                          ND-5000*
                                          0.4-3.0
              ND-1500*
              0.62
 *ppm
**ug/m3

 T:  Trace.
ND:  Not detected.
Source:  Adapted from James, Kinman, and Nutini, 1985.

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                                       TABLE  1  (Concluded)
Type of
Contaminant
Toluene

Kin Buc
(ng/m3)


Love Canal
(ug/m3)
0.1-6.2
570
Site
Sylvester
(ppb)


Midco I
(ppb)


BKK
(ppb)


Chem Dyne
(ppb)

Trichloro-
   ethanes
Trichloro-
   ethylene

Vinyl
   Chloride

Vinylidene
   Chloride

Xylenes
T (1,1,1)
294-357
(1,1,2)

T-10052
15-48.75**
454-555
 73
73
1.54
0.05-0.58
ND-1000
0.2-1.8

83-12800*
2-7.3

RD-1200*
0.3-1.3
              140
               73
1.8
 *ppm
**ug/m3

 T:  Trace.
ND:  Not detected.
Source:  Adapted from James, Kinman, and Nutini, 1985,

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propensity of sites to emit contaminants are:  the type of site




(e.g., landfill, surface impoundment), the size of the site




(including both the quantity of waste deposited and the surface area




of the site), the characteristics of the soil on the site, and the




containment provided by natural and manmade barriers to emissions.




The age of the site is also very important but cannot usually be




readily assessed.  Older sites with poor containment have probably




released nearly all of their contaminants while newer sites with




poor containment are probably currently emitting.  Additional site




characteristics of lesser importance include:  wind speed,




surrounding topography, precipitation, temperature, humidity,




and atmospheric pressure.




     The most important factors relating to the nature of the waste




are the contaminant concentrations in the waste and the inherent




physiochemical characteristics of the contaminant that influence its




propensity to migrate through and out of the site to the




atmosphere.




2.3  Contaminant Transport and Transformation




     The most common air contaminant release situation is the




emission of contaminants directly into the atmosphere.   Once in the




air, the contaminants become subject to atmospheric transport and




transformation processes which dilute the contaminant concentration




as the emissions are "spread out" over an increasing area.  The size




of this area effected by an emission is determined by many factors,
                                 13

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some which simply reduce the contaminant concentration (dilution




and removal) and others that transform the contaminant into other




chemicals (transformation).  Together, dilution, removal, and




transformation play a major role in determining the distance from




the site at which the concentration of a contaminant released from




the site into the atmosphere becomes insignificant.




     The mechanics of dilution in the atmosphere are generally well




known.  There are two principal dilution processes; advection and




diffusion.  Advection refers to the transport of contaminants




arising from wind.  Diffusion arises as a result of turbulence in




the atmosphere, either thermal or mechanical.  These processes are




generally rapid phenomena and are usually modeled in terms of an




exponential function of distance or time (Hanna, Briggs, and Hosker,




1982).  The processes that give rise to dilution are also largely




independent of the particular chemicals of concern.  The remaining




processes of contaminant removal and transformation in the atmosphere




are more complex and less well known.




     One measure of the speed of contaminant removal and




transformation (which in turn would indicate the limit of the




potential exposure area) is the "atmospheric residence time" of the




contaminant of concern.  This contaminant-specific parameter is




defined as the amount of time it takes 1-1/e (about 63 percent)




of an initial quantity of a contaminant to be removed from the




atmosphere by physiochemical processes such as photochemical
                                 14

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oxidation and deposition.  Atmospheric residence times for toxic and




hazardous contaminants generally range between 3 and 70 days but may




reach as high as 11,000 days (Cupitt, 1980).  Table 2 lists the




atmospheric residence times for typical waste site contaminants.




Many of the common waste constituents, therefore, remain in the




atmosphere for a long period of time and, considering common wind




speeds in the United States, may be transported over long distances.




Because of this, the geographic extent of potential exposure to air




releases from a particular waste site is much greater than that of




any other transport route.  However, the magnitude of this exposure




decreases rapidly as the concentration declines due to dilution.




Therefore, although the number of exposed individuals may be large,




the degree of exposure will be low over most of the geographic area




concerned.




     A. less common phenomena is the transport of gases through the




soil (sometimes dissolved in ground water) resulting in eventual




emission into the interior of buildings.  Once inside the buildings,




these contaminants may become trapped, resulting in the buildup of




contaminant concentrations.  Contaminant concentrations in such




instances may reach relatively high levels, as shown in Table 3.




The contaminant concentrations illustrated in this table probably




arose from wastes sites in the Niagara Falls area, such as the Love




Canal disposal site.  Thus, situations of low population, high




dosage exposure may occur due to the emissions of air contaminants
                                 15

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                               TABLE  2

       ATMOSPHERIC RESIDENCE TIMES* FOR SELECTED CONTAMINANTS
                 DETECTED AT HAZARDOUS WASTES SITES
	Compound	Residence Time (days)

Carbon Tetrachloride                           Greater than 11,000
Chlorobenzene                                          28
Chloroform                                             120
Dichlorobenzene                                        39
Dioxane                                                3.9
Methyl Chloroform                                      970
Methylene Chloride                                     83
Nitrobenzene                                           190
PCB                                              Greater than 11
Toluene                                                1.9
Trichloroethylene                                      5.2
Xylenes                                                0.7
*Time required for a quantity of the individual compound to be
 reduced to 1/e of its original value by deposition, chemical
 transformation, or similar processes.

Source:  Adapted from Cupitt, Larry T., Fate of Toxic and Hazardous
         Materials in the Air Environment, (EPA-600/3-80-084), U.S.
         Environmental Protection Agency, Research Triangle Park,  NC,
         August 1980.
                                 16

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                               TABLE  3

            RANGES OF ESTIMATED LEVELS OF ORGANIC VAPORS
                IN AMBIENT AIR OF HOUSEHOLD  BASEMENTS
                        IN NIAGARA FALLS, NY
                               (ug/m3)
        Chemical                                  Concentration Range
Chlorobenzene
Dichlorobenzene Isomers (3)*
Trichlorobenzene Isomers (3)
Tetrachlorobenzene Isomers (2)
Pentachlorobenzene
Chloro toluene Isomers (2)
Dichlorotoluene Isomers (3)
Trichloro toluene Isomers (4)
Tetrachlorotoluene Isomer
Bromotoluene Isomer
Chloronaphthalene Isomer
1,2 - Dichloropropane
Pentachlorobutadlene Isomer
1,3 - Hexachlorobutadiene
Benzene
ND -
0.65 -
0.07 -
0.03 -
T -
1.7 -
0.13 -
0.06 -
0.03 -
T -
0.08 -
1.4
T
0.03 -
T -
4.2
190
33
20
0.49
490
370
0.157
4.1
4.4
3.4


0.41
520
*Values are the sum of the individual isomers detected.

ND:  Not detected.
 T:  Trace.

Source:  Pellizzari, Edo D., "Analysis of Organic Vapor  Emissions
         Near Industrial and Chemical Waste Disposal Sites,"
         Environmental Science and Technology, Vol.  16,  No.  11,
         1982, pp. 781-785.
                                 17

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 from wastes sites.   This type  of  situation  is  in contrast  to  the

 high population,  low dosage  exposure  situations found as a result of

 emissions directly  into  the  atmosphere.  This  difference in exposure

 situation requires  differences in scoring mechanisms to account for

 the different threats.   This phenomenon is  not reflected in the

 current  HRS air pathway,  nor in the options discussed in Section 3.

 A separate report addresses  the situation where building interior

 air contamination exists  (Wolfinger,  I987b).*
*Currently, situations of indoor air contamination are considered
 for NPL listing when the contaminated buildings themselves are
 considered "sites," (see, for example, Monticello Radiation
 Contaminated Properties, NPL Ranking 502, 51 FR 20153).
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3.0  ISSUES IN THE HRS AIR PATHWAY

     This chapter presents a discussion of the issues that have been

identified concerning the HRS air pathway.  A description of the overall

structure of the HRS and the current air pathway is also provided.

3.1  Background on the Hazard Ranking System

     The HRS is designed to assess a site based on the information

compiled in a site inspection.  The system is intended to "estimate

the potential hazard presented by releases or threatened releases of

hazardous substances, pollutants and contaminants," and to score the

site based on the risk posed by releases from the site (47 FR 31187).

The HRS addresses three hazard modes:  migration, fire and explosion,

and direct contact.  The latter two are not used in computing the site

score but are included in the HRS as indicators of the need for

emergency response.  The migration mode consists of three potential

migration pathways representing the major routes of environmental

transport common to hazardous wastes sites:  ground water, surface

water, and air.  Each pathway is structured similarly using three

factor categories:  release, waste characteristics, and targets.

     The release category reflects the likelihood that the site has,

is, or will release contaminants to the environment.  If available

monitoring data indicate that the site is releasing contaminants, then

an "observed release" has been demonstrated.*  If no such observed
Information other than ambient monitoring data can be used to
 establish an "observed release" in certain situations.  These
 situations are addressed on a case-by-case basis.
                                 19

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release can be demonstrated, then the release category is evaluated




using route characteristics and containment factors.   These factors




are largely physical characteristics of the sites and their




surrounding environments.  It is important to note that the ground




water and surface water routes contain factors for route




characteristics while the air route does not.   This permits sites to




be evaluated for their potential to release contaminants to these



two pathways in cases where documentation of a release is lacking.




The current HRS requires that ambient air monitoring data support



the conclusions that the site is, or has been, emitting contaminants




before the site can receive a nonzero air route score.




     The waste characteristics category reflects the implicit hazard




of the contaminants that have been or might be released.  The




factors included in the waste characteristics categories address




qualitative and quantitative characteristics of the wastes and waste




contaminants found on the sites.  The targets category constitutes a




measure of the population and resources that might be adversely




affected by a release.   The factor categories and the factors




contained in them are illustrated in Table 4.




     Within each pathway, the site is assigned a value for each




applicable factor.  The factor values are then multiplied by




weighting factors and summed within factor categories.  The resulting



factor category values are then multiplied and normalized to form a




migration route score.   Thus, for each site, three migration route
                                 20

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                                             TABLE 4

                                       HRS SCORING FACTORS
Factor Category
                                                        Pathway
    Ground Water
       Surface
Release Category
Waste
  Characteristics
Targets
Monitoring data
     or
Depth to aquifer
  of concern
Net precipitation
Permeability

Physical state
Containment

Toxicity/persistence

Quantity
Ground water use
Distance/population
Monitoring data
     or
Facility slope and
  terrain
Rainfall
Distance to receiving
  water
Physical state
Containment

Toxicity/persistence

Quantity
Surface water use
Distance/population
Distance to sensitive
  environment
Monitoring data
Reactivity/
  incompatibility
Toxicity
Quantity

Land use
Distance/population
Distance to sensitive
  environment

-------
 scores  are  produced, each on a scale of 0 to 100.  These route



 scores  are  referred to as follows:



      •  Ground water (S  )
                       gw


      •  Surface water (S  )
                        sw


      •  Air (S)
              a


 The  overall site migration score (S ) is then calculated as the
                                   m


 root mean square (RMS) of the pathway scores:

                                  7        7       9 1/2
               s  - (i/i.73)[(s  r + (s  r + (s r]
                m              gw       sw       a


 The  RMS procedure was chosen to emphasize the highest scoring route



 while giving some consideration to secondary and tertiary routes.



 This procedure is illustrated in Figure 1.



 3.2   Issues in the Current HRS Air Pathway



      The principal air pathway issue concerns an apparent



 Inconsistency in the release category among the three migration



 pathways.   Currently, air pathway release category is evaluated



 solely  on the basis of sampling data, or occasionally other types of



 information  that indicate contaminants have escaped from the site



 into  the air (e.g., photographs coupled with soil contamination



samples).    If the data indicate that an "observed release" has



occurred,  then a release category value of 45 is assigned.



Otherwise,  the site is assigned an air pathway release category value



of 0.  This latter assignment, combined with the multiplicative



structure of the air pathway, results in the site being assigned an



air route score of 0.   In contrast, within the ground water and
                                 22

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Observed Release
   0 or 45 pts
      or
     Route
Characteristics &
 Containment*
     0-45 pts


GW
SW
A
Waste
Characteristics
— 0-26 pts
— 0-26 pts
— 0-20 pts
*Not Included in Air Pathway
GW = Ground Water Pathway
SW = Surface Water Pathway
A   = Air Pathway
Targets
GW —
SW —
A —
0-49 pts
0-55 pts
0-39 pts
                                                                                                Pathway Score
                                                                                                  0-100 pts
                                                                                                 Normalized
                                                 FIGURE 1
                                         BASIC MRS STRUCTURE

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surface water pathways, an option Is provided for evaluating the




release category based either on sampling data,  ££ on the physical




characteristics of the site and its surrounding environment.  These




latter characteristics reflect the potential of the site to release




deposited contaminants.




     The inclusion of a potential to release option within the




migration pathways improves the degree to which the HRS score




reflects the relative risk posed by a site.  This conclusion is based




on several reasons.  First, it is not always possible to determine




that a site is releasing contaminants based on monitoring data.  The




contribution of the site to ambient contaminant concentrations may




be masked by the contributions of other sources.  Alternately,




adverse environmental conditions (e.g., high wind in the air pathway)




may make the detection of contaminants in the surrounding media




infeasible.  Thus, relying solely on monitoring data may result in




sites being assigned scores of zero, even though they pose a threat




(albeit an undetected threat).  Second, even if the site is not




currently releasing contaminants, it may begin to release material




in the near future.  Relying solely on past information may result




in a site being assigned a zero score, even though that site may




pose a significant threat in the near future.  Drum sites are an




example of this possibility.  Drums provide adequate, temporary




containment for many wastes but can not generally be relied upon to




contain the wastes over time.  Finally, the site may have released
                                 24

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contaminants in the past that were undetected in the site




investigation, that still pose a threat to the surrounding population




and environment.  Examples of this possibility are large air emitting




facilities that are currently inactive or abandoned but that caused




area wide soil contamination from contaminant deposition.




     As a result of the review of current knowledge on air releases




from hazardous wastes sites, known criticisms of the HRS and the




collective years of experience with the implementation of the HRS,




five additional issues were identified within the context of the air




pathway during development of these options.   These issues were




deemed to be sufficiently important to be addressed in the




development of the proposed modifications.




     First, the air pathway toxicity value for a site is based on the




toxicity characteristics of the single, most toxic contaminant known




to be present on the site and available for migration.  In this




context, contaminants are "available for migration" if they are not




contained on the site by some physical barrier (e.g., the containment




factor value for the portion of the site in which the contaminants  is




found is nonzero).  This approach is employed regardless of whether




the physiochemical characteristics of the contaminant would prevent




it from escaping in a quantity sufficient to pose a significant




threat to the surrounding area.




     Second, concern has been raised about the adequacy of the




current approach to assessing the potential of waste materials to
                                 25

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Interact on a site, either Increasing the rate (or probability) of air




releases or causing the formation of more toxic contaminants than were




originally deposited on the site.  The air pathway currently employs a




waste reactivity and incompatibility factor to reflect this potential.




This issue is addressed in a separate report (DeSesso et al., 1986).




     The third issue arises from the way in which population is




estimated in the air pathway targets category.  These population




estimates are developed in two ways.  In the first, population data is




acquired from the local governments in the areas surrounding the




site.  This method is most commonly employed when the target radii




encompass entire jurisdictions.  In the second method, population is




estimated using estimates of the number of houses in the applicable



areas.  These house counts may be provided by local governments or may




be made using maps of the area such as USGS topographic maps.  The




number of houses is converted to equivalent population using an




estimate of 3.8 persons per house.




     This estimation procedure suffers from several weaknesses.




First, the accuracy of the information is degraded in cases where the




target radii do not encompass entire jurisdictions.  The problem of




determining the fraction of the population that resides within the




area defined by the target radii is a serious problem.  In these




circumstances, emphasis is often placed on the house counts.




     The second weakness lies in the way the house counts are




developed.  These counts are often provided by local jurisdictions or
                                 26

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developed from recent local planning maps.  In such cases, the house




counts themselves may be very accurate.  However, in other instances,




they may be based on outdated maps, such as USGS topographic maps,




and hence may be very inaccurate.




     The third weakness arises whenever house counts (accurate or




not) are converted into equivalent population.   The use of a uniform




value of 3.8 persons per house ignores spatial and other variations




in household demographics.  The availability of 1980 Census data as




an alternative to these data source highlights these weaknesses.




     The fourth issue concerns the geographic extent of potential




exposure to air contaminants from a site.  The current HRS employs



a radial distance limit of four miles in evaluating the population




exposure factor and distance limit of two miles in evaluating the




land use and sensitive environment factors.  Given the potential




geographic extent of exposure indicated by the available information




on atmospheric residence times and long-range transport phenomena




(see, for example, National Research Council, 1983), a re-evaluation




of these "target distance" limits is indicated.  A separate report




addressing the question of target distance limits is being prepared




(Wolfinger, 1986a).




     The final issue arises from the underlying assumptions embedded




in the current air pathway about the nature of air contaminant




migration.  The pathway is designed to rank sites based on the




potential hazard they pose through direct emission of contaminants
                                 27

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to the ambient air, subsequent transport, and eventual inhalation.  As




stated previously, situations of indoor air contamination are generally




scored using the air pathway only when the buildings in question are




considered the "wastes site".  Due to its underlying assumptions, the




HRS air pathway does not address the potential hazard posed by




migration of air contaminants from a wastes site, through the soil,




and into buildings.  This is evident in the definition of observed




release used in evaluating monitoring data.  The data used to




establish an observed release must be based on outdoor, ambient air




monitoring.  Data from monitoring performed indoors can not be used to




establish an "observed release" unless the contaminated building




itself is the site.  Situations may arise in which a significant threat




is posed by a site due to the migration and potential inhalation of




air contaminants that, nonetheless, will not receive a nonzero air




pathway score unless those emissions are sufficient to induce an




elevation in outdoor contaminant concentrations above background.  Due




to differences in dispersion characteristics between indoor and




outdoor air, it is possible that indoor air concentrations may reach




significant levels while outdoor air concentration remains relatively




unaffected.  Thus, the air pathway observed release assumptions




effectively preclude assigning a positive score to many sites




experiencing indoor air contamination problems.




     Further, the current HRS air pathway is somewhat biased against




such sites in the approach taken to evaluate the size of the exposed
                                 28

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population.  The target population factor approach requires that a




fairly large population reside near the site to achieve a high value.




A population of at least 1,001 persons residing within 1/4 mile of the




site (3,001 within 1/2 mile or 10,001 within 1 mile) is required to




assign 24 out of a possible 30 points for the population target factor.




This is moderated by the medium values assigned to low populations




near the site (e.g., one person residing within 1/4 mile of the site




permits a site to receive at least 18 out of a possible 30 points).




The approach currently employed reflects the perception that the




average dose to the population, will be small, while the exposed




population will be relatively large.  This approach is not consistent




with the high dose, low population exposure situation that would be




characteristic of indoor air contamination sites.   Because of this




inconsistency, the HRS air pathway score assigned to a site associated




with indoor air contamination may understate the relative risk posed




by the site by underemphasizing the importance of exposures to small




populations.  Thus, the current HRS air pathway may not be adequate




for assessing the relative threat of these sites.   A scoring mechanism




for indoor contamination sites is presented in Wolfinger, 1987b.




     The air pathway options, discussed in Sections 4 and 5, address




the potential to release issue and the first three of the additional




issues discussed above:  evaluation mobility as part of the toxicity




factor, use of waste reactivity and incompatibility data, and




population evaluation.
                                 29

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3-3  Options for Revising the HRS Air Pathway




     The following two chapters describe three options for revising




the HRS air pathway, in response to the issues discussed above.   The




principal focus of the options  is on methods for evaluating the




potential of a site  to release  contaminants.  The first two Options




(1 and 1A) are very  similar,  they differ only in the  particular




descriptors used in  evaluating  sites.  Both  of these  options employ a




multiple emission source descriptor approach, using probabilistic




combinatorics  to combine the  values associated with each  descriptor




into  an overall value  for the site.  The third option (Option 2) is a




simpler approach, again employing a choice among several  emission




source descriptors,  although  only the highest scoring applicable




descriptor  is  used  to  evaluate  the site.  This latter approach is




 similar  to  that used in the ground water and surface  water pathway.




      Numerous  additional options were developed, discussed with EPA,




 and rejected.  These options  are summarized  in Appendix B.
                                  30

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4.0  MULTIPLE SOURCE, PROBABILISTIC APPROACHES (OPTIONS 1 AND 1A)




     Two similar options for revising the HRS air pathway are




presented in this chapter.  The options are consistent in structure




with the ground water and surface water migration pathways of the



current HRS.  However, these options use a very different approach




to evaluating the overall potential of a site to release contaminants




than is used in the other pathways.  The other pathways evaluate the




overall site release potential based on the potential of that portion




of the site that is most likely to release contaminants (i.e., a




single, "worst" source approach).  The options described in this




chapter employ probabilistic combinatorics to assess the site




potential as the aggregate potential of up to three source areas on




the site.  The important features of the options are summarized in



Table 5.  An alternate, single, "worst" source approach, for the air




pathway is presented in Section 5.




     In each option, the analyst evaluates available ambient air




monitoring data to determine if an observed release has occurred.




If the data do not demonstrate an observed release, the analyst may




then evaluate the site based on its potential to release.  In either




case, the waste characteristics and targets factors are then




evaluated as indicated.  The release, waste characteristics and




targets factor evaluations are next multiplied together and




normalized on a scale of 0 to 100 to form the air pathway score.
                                 31

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                               TABLE 5

                 OVERVIEW OF IMPORTANT FEATURES OF
                    AIR PATHWAY OPTIONS 1 AND 1A
                   	Option 1	  	Option 1A	

RELEASE CATEGORY   Observed release          Observed release
                     based on monitoring       based on monitoring
                     data                      data
                   Potential to release      Potential to release
                     based on:                 based on:
                      - 30 size-dependent       - 12 size-dependent
                        emission source           emission source
                        descriptors               descriptors
                        (3 size classes)          (3 size classes)
                      - gas and particulate     - gas and particulate
                        mobility factors          mobility factors
                      - detailed gas            - less detailed gas
                        and particulate           and particulate
                        containment factors       containment factors

WASTE              Combined toxicity-        Combined toxicity-
CHARACTERISTICS      mobility factor           mobility factor
                   Waste quantity            Waste quantity

TARGETS            Population                Population
                   Sensitive environment     Sensitive environment
                   Land use                  Land use
                                 32

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     The following sections discuss the three factor categories




(release, waste characteristics, and targets) and the rating factors




contained in them, for the two air pathway options.  The relationship




between the categories and the factors is illustrated in Table 5.




Tables for all of the factors, except containment, are provided in




the text.  Tables of containment factors are provided in Appendix  D.




Step-by-step instructions for employing Option 1, with an example  of




its application, can be found in Appendix C.




4.1  Release Category




     The release category reflects the likelihood that the waste




site was, is now, or will be, emitting a significant quantity of any




air contaminant or combination of contaminants.  If the available




monitoring data indicate that the site has released hazardous




substances to the air (i.e., an observed release has occurred),  then




the likelihood that the site is emitting a significant quantity of




an air contaminant is deemed to be 100 percent (47 FR 31188).  In




these cases, a maximum release value would be assigned to the site.




The maximum value possible has been set at 45, maintaining




consistency among the pathways in the current HRS.




     If no observed release can be documented, then the site is




evaluated based on its "potential to release".  The maximum possible




potential to release value is also 45.  The potential to release




factor value reflects the likelihood that the site has released




contaminants in the past or will release contaminants sometime in
                                 33

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the future, as well as the likelihood that the site is currently

emitting undetected contaminants.   This likelihood is formally a

subjective probability.*  It is "subjective"  in that it is based on

information about the site rather  than a frequency of occurrence of

releases at other sites with similar characteristics.  It represents,

therefore, the judgment of a group of experts rather than the results

of a statistical sampling program.  The options for evaluating

potential to release, discussed below, establish a procedure for

translating information about the  physical characteristics of a

wastes site into a subjective probability that the site has, is, or

will emit a significant quantity of contaminant.

     4.1.1  Observed Release

     Several factors contribute to the determination that an

"observed release" has occurred at a site. Given the wide variety

of emission sources contributing to air pollution, it is nearly

always possible to detect air contaminants near a wastes disposal

site.  However, the detected contaminants may not have been released

from the site, but may have originated from numerous sources nearby

or even a long distance away.  For example, sulfate originating in

the Ohio River Basin has been detected in Upstate New York, while

indium from Ontario has been detected in Rhode Island (National

Research Council, 1983; Rahn, Lowenthal, and  Lewis, 1982).
*For detailed discussions on subjective probability, the reader is
 directed to Jaynes, 1958; Kyberg and Smokier, 1964; Raiffa,  1970,
 and Stael von Holstein and Matheson, 1978.

                                 34

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     It is essential, therefore, to determine that a significant




portion of the detected contamination arose from the site.   A sample




of the "background" air is required to make this determination.   The




background sample should be taken close enough to the site  to




include the contributions of all other major sources of potential




contaminants but far enough away from the site to exclude




contributions from the site itself.  This generally implies that the




background sample be taken upwind from the site and that the "site




sample" be taken downwind of the site.




     The difference or ratio of the site and background samples  can




be used to determine if an observed release has occurred.  If the




ratio or difference is "significant," then the site is considered to




be emitting and an observed release value of 45 is assigned.




Otherwise, an observed release value of 0 is assigned and the




potential to release rating factors are evaluated.




     4.1.1.1  Definition of Significant Difference.   The question of



"significance" in the context of the HRS air pathway is complex.  It




is complicated by the highly variable nature of the atmospheric




environment and the effects of such variations on site emission




characteristics.   A release is considered significant if it results




in an elevation in the ambient concentration of any contaminant




above that which would occur if the site were not present.




Furthermore, there must be a reasonable certainty that any  elevation




in concentration indicated by the data arose from the site  and is
                                 35

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not simply the result of factors Independent of the site, e.g.,




meteorological conditions and nearby sources.  Significance is thus




defined in terms of demonstrating that a release has occurred, not




in terms of the degree of hazard posed by the release.  A complete




discussion of the question of significance in the context of the HRS




can be found in Brown, 1986.




     4.1.1.2  Implications for Sampling.  These considerations place




requirements on the procedures used in sampling.  It is imperative




that the site samples not be taken in such a fashion as to




artificially elevate the measured concentrations.  This imperative




precludes, for example, the use of samples taken inside of drums or




vents, or samples taken immediately above pools of liquid wastes, as




site samples.  The overriding principle concerning a site sample is




that it represent the concentration that an individual might




reasonably be exposed to from the site.  In practice, this principle



leads  to an operational "rule of thumb" that the site sample should




be taken at least 20 feet away from the emission sources on the site




and that the sample be taken "in the breathing zone".




     The background and site samples can then be compared and the




release category evaluated.  An obvious problem arises in practice,




however, with this approach.  Financial constraints usually restrict




the number of air samples taken.  In most cases, the emphasis in air




sampling has been placed on investigator safety rather than site




characterization.  Typically, only a few ambient samples are
                                 36

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available for any particular site for use in assessing observed




releases.




     An additional problem arises regardless of the thoroughness of




the sampling plan, the sophistication of the sampling equipment




employed and the care taken during actual sampling.  Because the




emissions characteristics of many sites generally depend on highly




variable atmospheric conditions (including temperature, pressure,




wind speed, and stability), it is possible that many sites may not be




releasing a sufficient quantity of contaminants to affect an observed




release during the sampling period.  Alternately, the sampling




stations may not be in the "emissions plume" due to unforeseeable




meteorological conditions.  Thus, it is all too likely that air




sampling will miss an observed release unless the site emissions




rate is high and sustained, or unless the sampling was performed at




an advantageous time and place.




     4.1.1.3  Improvements in the Current Approach.  The options




presented here envision a somewhat different approach than is




currently used to evaluate whether an observed release has occurred.




The practice in the current MRS is that a statistically significant




difference between contaminant concentrations in background and site




samples, or an order of magnitude difference between background and




site samples, is sufficient, but not necessary, to achieve an




"observed release".  There are numerous problems with the statistical




approach.  It is problematic whether the samples taken during a site
                                 37

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investigation meet the requirements for statistical hypothesis




testing of significant difference, e.g., representativeness and




independence.  The "order of magnitude" approach, as it is currently




employed, is also weak.   There is little scientific basis for




requiring a 10-fold difference to demonstrate an observed release




(as opposed to, for example, a 5-fold or 20-fold difference).  This




aspect of determining observed releases is discussed in Brown,  1986.




     Currently, there are few restrictions on the samples; the  only




uniformly binding requirements being that the samples be taken  "in




the breathing zone," i.e., at a height of about five feet and that




they be taken with an instrument that will screen out methane.   No




other restrictions apply uniformly and no consideration is given to




the conditions under which the samples are taken.




     Because of the problems routinely encountered by investigators




in establishing an observed air release based on current sampling




practices, stricter requirements on monitoring data would be imposed




in these options making it more difficult for a site to achieve an




"observed release".  However, the atmospheric conditions under  which




the monitoring occurred would be considered,  potentially reducing




the level at which a difference between the the background and  site




samples would be considered significant.  This approach is described




below.   The approach employs the ratio of the background and site




samples as the measure of interest.  A similar approach can be




developed using the difference between the samples.  The thresholds
                                 38

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for significance employed below are provided for illustrative




purposes only and will be further evaluated.




     Under "normal" atmospheric conditions, the ratio of the




concentration of any CERCLA contaminant in the site and background




samples would be required to exceed a uniform threshold (e.g., 10)




to achieve an observed release.  "Normal" atmospheric conditions are




considered to be those that do not suppress emission from the site.




If atmospheric conditions are such that detected concentrations would




be lowered relative to the site's potential to emit, or if emissions




levels would be suppressed relative to average conditions, then




conditions would be considered "abnormal".  Under these conditions




a lower significance threshold would be used, for example, a ratio




of 1.5.  If either threshold is achieved, as applicable, then a




release value of 45 would be assigned.  Information describing the




sampling conditions, including average wind speed and direction




during sampling, must be provided in support of the sampling data.




Identification of other potential, nearby sources of the detected




contaminants is also desirable.  Atmospheric conditions deemed to




meet the criteria for a lower threshold value are listed in Table 6.




This list is intended to be fairly exhaustive, although other




circumstances should be treated on a case-by-case basis.




     If implemented, this list of conditions would require further




refinement.  Consideration must be given to the trade-off between




the increased flexibility in determining an observed release
                                 39

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                 TABLE  b

  SITE CONDITIONS THAT MAKE IT DIFFICULT
    TO DEMONSTRATE AN OBSERVED RELEASE
High wind speeds

Low temperature

High relative humidity, including precipitation

Flat and open surrounding terrain

Unstable atmosphere
                    40

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envisioned here, and the increase in difficulty in assuring the




quality of the data that such a subjective approach entails.




     Further guidance on site sampling can be found in the reports




listed in Section 8.2.




     4.1.2  Potential to Release




     As implied in the above discussions, there are numerous reasons




why an observed release from a site may be difficult to demonstrate



even though a release has occurred.  The potential to release portion




of the air pathway is intended to provide for the scoring of sites




when no observed release can be demonstrated.




     The approach reflected in the options discussed below uses




information on the physical and chemical characteristics of the




site and the wastes in the site to assess the subjective probability




that the site has, is, or will emit a significant quantity of




contaminants.  This subjective probability is implicitly translated




into a scale of 0 to 45 in the tables and worksheets.  The




characteristics of a site that indicate its potential to release are




evaluated and the resulting values combined in an algorithm that




reflects the probabilistic aspects of the release category.  This




algorithm is discussed in detail below.




     This approach differs from the approach currently embodied




in the ground water and surface water pathways, although the




potential to release values in these pathways can be interpreted




probabilistically.  Currently, in the other pathways, the evaluation
                                 41

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of the release potential of a site employs a single, "worst" source




approach.   In these pathways, different areas of the site are




evaluated according to particular criteria (e.g., physical state and




containment) and the value for the highest scoring area (i.e., the




single, "worst" source) is used as the release value.  Interpreted




probabilistically, the release category in the ground water and




surface water pathways reflect the maximum probability that some




portion of the site will release contaminants.  This "maximum" value




is actually less than the combined probability that some portion of




the site will release contaminants.  The combined probability is




employed in Options 1 and 1A discussed below.  The option discussed




in Section 4 (Option 2) employs the approach embodied in the current




ground water and surface water pathways.




      The overall approach discussed below was chosen for two




fundamental reasons.  First, the principal alternate approaches




(those based on emission estimation equations) were deemed to be too




complex and required data that would be impossible to gather in a




site  investigation (e.g., mass transfer coefficients for contaminants




in site-specific waste mixtures).  Second, this approach is




consistent with the probabilistic nature of the potential to




release component of the pathway and employs most of the principal




factors that determine site emission characteristics.  This approach




better reflects the probability that the overall site will emit




contaminants, in comparison to the single maximum approach currently
                                 42

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employed in the other pathways, and hence, results in a site score




that better reflects the risk posed by the site.   The principal




negative aspect of the approach taken is its computational




complexity.




This complexity is mitigated, however, by the development and use of




descriptive tables and easily used references (e.g.,  Versar, 1984).




     As indicated in Table 5, four site characteristics are employed




in assessing the potential of a site to emit air  contaminants:




     •  Emission source descriptor




     •  Size




     •  Overall contaminant mobility




     •  Containment




The first two characteristics are combined into a single factor.



     The size-dependent emission source descriptors constitute a




simple classification of sites according to type  of "disposal"




employed on the site (e.g., landfill or surface impoundment).   The




use of these descriptors reflects the belief of the author that the




type of site is important in determining the rate and duration of




emissions.  The importance of the type of disposal practice employed




on the site in determining organic compound emissions is indicated




in Table 7.  This table indicates that the disposal practice is one




of the principal determinants of the rate of volatilization of




organic compounds from a site.  For example, the  data indicate that




emission rates from landspreading will be greater for a shorter
                                 43

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                              TABLE 7

         TIME NEEDED FOR  75 PERCENT OF SELECTED COMPOUNDS
            TO VOLATILIZE FOR VARIOUS DISPOSAL METHODS
Contaminant
Phenol
Tetrachloroethylene
Benzene
Ethanol
Methyl Ethyl Ketone
Ethylactetate
Tricolor oethylene
Chloroform
Carbon tetrachloride
Dichloroethane
Dimethylamine
Ethylene
Pentane
Dichloroethylene
Landspreadlng
39 days
*
5 days
16 hours
7 hours
*
7 hours
*
*
3 hours
0.7 hours
*
*
*
Disposal
Method
Surface
Impoundment
*
12.4 days
11.6 days
*
*
*
11.4 days
11.3 days
10.3 days
9.1 days
*
7.4 days
*
*
Covered
Landfill
333 years
*
41 years
*
*
2.6 years
2 years
11 months
*
11.7 months
*
*
7.8 months
4.2 months
*Data not available to  calculate rate for this substance.

Source:  Scheible et al.,  1982.
                                44

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period than those of covered landfills, all other characteristics




being the same.




     Contaminant mobility refers to the overall propensity of the




contaminants on the site to migrate to the surface and escape into




the atmosphere, based on their physiochemical characteristics.




Contaminant mobility is reflected with separate factors for gaseous




and particulate contaminants.  Table 7 also illustrates the




importance of the characteristics of the contaminants in the site.




As indicated in Table 8, phenol is generally less mobile than




dichloroethane.  This relative mobility is evident as well in the




longer retention time indicated for phenol in a landfill (333 years)




as compared with dichloroethylene (4.2 months).




     Containment refers to the physical characteristics of the site,




either manmade or natural, that act to restrict emissions and




contain the contaminants on the site.  Containment is also reflected




with separate gaseous and particulate factors.   Containment is the




single most important factor determining potential to release, hence




its employment as a multiplicative rather than an additive factor.




     The overall approach to evaluating the potential of a site to




release contaminants is as follows.  The emission sources on the




site are identified and classified using the emission source




descriptors.   The size of each emission source is assessed and a




size class assigned to each emission source descriptor.  From this
                                 45

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                              TABLE 8

          DATA ON MOBILITY OF PHENOL AND DICHLOROETHYLENE
Contaminant
Phenol
Dichlorethylene (1,1)
VP*
0.62
630.1
AQ*
1.3 E-6
1.5 E-2
RS*
2.0 E-l
202
*VP:  Vapor pressure In units  of mmHg at 25° C.
 AQ:  Henry's constant in units of atm-m^/mol.
 RS:  Relative soil volatility as defined  in Versar,
                                46

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information, a size-dependent emission source descriptor value is




assigned to up to three of the selected descriptors.




     The contaminants present in the areas represented by the




descriptors are identified and used to calculate a gaseous




contaminant mobility value for each descriptor.   The particulate




mobility value for each selected descriptor is calculated based on




characteristics of the climate surrounding the site (primarily wind




speeds, precipitation, and temperature).   The two mobility values




are combined and added to the emissions source descriptor value, for




each descriptor selected.



     The gas and particulate containment aspects of the areas




represented by each of the three selected descriptors are evaluated




and their values combined into a single containment value for each




selected descriptor.




     The sum of the descriptor and mobility values are then




multiplied by the containment value to form an overall value for




each of the three selected descriptors.  This value represents the




probability that the sources represented by the selected descriptor




has, is, or will emit a significant amount of contaminant.  The




three descriptor-specific values are then combined into an overall




potential to release value for the site using the appropriate




probability formula (see Section 4.1.2.4).




     The relationship of the potential to release value to the




probability that a site will emit a significant quantity of air
                                 47

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contaminants (i.e., the emissions probability) is as follows.   The

size-dependent site descriptor value reflects the subjective

probability that an uncontained site (containment value equivalent

to 3) with relatively immobile contaminants (mobility value equivalent

to 0) could release a significant quantity of air contaminants.  The

emission probability is equal to the value divided by 15.  For

example, the emission source descriptor value assigned to a small

landfarm is 6.*  Thus, the probability that such a source, poorly

containing relatively immobile contaminants, would emit a significant

quantity of air contaminants is estimated at 6/15 (or, equivalently,

18/45).

     The mobility  factor serves to increase the emission probability

based on the overall mobility of the contaminants associated with the

emission source descriptor in question.  Continuing the example, the

emission probability for a similar landfarm with very mobile

contaminants (mobility value of 5) would be 11/15 (or [6 + 5]/15).

     The containment value serves to decrease the probability based

on the degree to which physical barriers present on the site would

reduce emissions.   Thus, the emission probability for a small,

relatively uncontained (containment value of 2) landfarm with very

mobile contaminants would be 22/45 (or 11/15 x 2/3).  This corresponds

to an overall value for the landfarm of 22 on a scale of 0 to 45.
*This example employs the value given in Table 13 for a small
 landfarm.
                                 48

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     Values based on any other scale can be readily developed by

multiplying the probabilities by the desired scale.

     The following discussion describes the factors and this approach

in greater detail.

     4.1.2.1  Size-Dependent Emission Source Descriptors.  A list of

emission source descriptors and associated definitions was developed

based on the results of the literature review, an examination of the

descriptors used by investigators in describing candidate NPL sites

and a review of the definitions promulgated under RCRA.  Lists of

the descriptors for Option 1 and 1A are provided in Table 9 and

Table 10, respectively.  Complete definitions are provided in

Appendix D.  The differences in the number and definitions of the

emission source descriptors listed in Tables 9 and 10 constitute the

principal differences between the options.*

     The selection of emission source descriptor is generally left

up to the investigator evaluating the site.  However, there are

necessary restrictions in the selection process.  First, the

descriptors selected should be the ones that best describe the site.

It contravenes the system to call a puddle of water a "surface

impoundment," for example, simply to achieve a higher site score.

Second, in order to use a descriptor, information indicating that

hazardous contaminants have been located or deposited in the area
*The only remaining differences between the options lie in the
 containment factor definitions.  These differences arise largely
 from the differences in emission source descriptors, as well.


                                 49

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                              TABLE 9

               OPTION 1 EMISSION SOURCE DESCRIPTORS


Code       Descriptor

           Aboveground or Iaground Tanks:

 01          •  Tanks intact
 02          •  Tanks broken

 03        Active Fire Site

 04        Belowground Injection

 05        Belowground Tanks

           Contaminated Surface Soil:

             •  Background at or above analytical detection limit;
 06             - Contamination level at or below background
 07             - Contamination level above background but not
                  significantly above background
 08             - Contamination level significantly above background
             •  Background below analytical detection limit;
 09             - Contamination level below analytical detection limit
 10             - Contamination level above analytical detection limit

           Exposed Drum Site:

 11          •  Drums broken
 12          •  Drums intact

           Inactive Aboveground Fire  Site:

 13          •  Re-ignition expected
 14          •  Re-ignition not expected

           Inactive Belowground Fire  Site:

 15          •  Re-ignition expected
 16          • Re-ignition not expected

 17        Landfarm/Landtreatment
                                 50

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                        TABLE 9 (Concluded)


Code       Descriptor

           Landfill:

 13          •  With both biodegradable material and exposed drums
 19          •  With biodegradable material but without exposed drums
 20          •  All other situations

 21        Open Pit

           Spill Site:

 .22          •  Spill dry
 23          •  Spill wet

           Surface Impoundment:

 24          •  Dry; evidence of waste contamination near surface
 25          •  Dry; all other situations
 26          •  Wet; evidence of waste contamination near surface
 27          •  Wet; all other situations

 28        Surface Water Body or Outfall

 29        Waste Pile

 30        Emission Sources Not Elsewhere Specified
                                 51

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                            TABLE 10




              OPTION 1A EMISSION SOURCE DESCRIPTORS






Code      Descriptors




 01       Active Fire Site




 02       Belowground/Buried Containers




 03       Contaminated Soil




 04       Dry Surface Impoundment




 05       Inactive Fire Site




 06       Intact Exposed/Aboveground Containers




 07       Landfarm




 08       Landfill




 09       Nonintact Exposed/Aboveground Containers




 10       Waste Pile




 11       Wet Surface Impoundment




 12       Emission Sources Not Elsewhere Specified
                             52

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covered by that descriptor is required before that descriptor can




be used.  Third, generally a descriptor can be used only once in




describing a site.  This principle applies unless it can be




established that two different areas described by the same descriptor




received different wastes or are otherwise dissimilar.  Further, the




area described by a selected descriptor should be as homogenous as




possible.  For example, if a site contains two different landfills




with similar waste and containment characteristics, then the




landfill descriptor may be used once, referring to both landfills




simultaneously.  However, if two dissimilar landfills are present on




the site, the "landfill" descriptor should be employed twice.  A




fourth restriction associated with the size of the source described




by the selected descriptor is discussed below.




     Three size categories are defined for emission source




descriptors using data developed in 0'Sullivan, 1982 and Vogel and




0*Sullivan, 1983.  Size category definitions were developed, for




convenience, both in units of surface area and equivalent volume, as




applicable.  Different values of depth were employed following the




assumptions in the aforementioned references.  The size categories




were developed using the percentiles of the distribution of RCRA




Part A volume and surface area data as presented in the references.




The RCRA Part A data was the only information source that could be




identified for size-related data.  The applicability of the data to




CERCLA sites is problematic.
                                 53

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     For the purposes of evaluating the size of the area covered by




a particular emission source descriptor, only the total area




containing waste materials should be included.  When two areas are




covered by the same descriptor, then the sum of their respective




areas is used in evaluating the overall area.  For example, if a site




contains two similar landfills (similar in waste and containment




characteristics), the size associated with the "landfill" descriptor




is the sum of the sizes of the landfills.   If the "landfill"




descriptor is used twice to reflect the presence of two dissimilar




landfills, then the size associated with each use of the descriptor




is the size of the applicable landfill.  Size categories for the




Option 1 and 1A emission source descriptors are presented in




Tables 11 and 12, respectively.




     The use of these size categories places an additional




restriction on the investigator's selection of emission source




descriptors.  In general, the areas covered by the descriptors




selected must be larger than the minimum size in the "Small" size




category.  If this constraint cannot be met, then the investigator




must use only the descriptor whose size is greatest relative to the




minimum size in its "Small" category.




     A set of values were developed for the various size-dependent




emission source descriptors based on the judgment of the author




concerning the subjective probability that a generic emissions




source of specified description and size would emit a significant
                                 54

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                              TABLE 11

                        OPTION 1 SIZE RANGES
           Descriptor

Belowground Tanks (cubic feet)
         Small
         Medium
         Large

Contaminated Surface Soil (square feet)
         Small
         Medium
         Large

Exposed Drum Site (number of drums)
         Small
         Medium
         Large

Inground or Aboveground Tanks (cubic feet)
         Small
         Medium
         Large

Inactive Aboveground Fire Site (square feet)
         Small
         Medium
         Large

Inactive Belowground Fire Site (square feet)
         Small
         Medium
         Large

Landfarm/Landtreatment (square feet)
         Small
         Medium
         Large

Landfill (cubic feet)
         Small
         Medium
         Large
    Size Range
1,000 - 8,900
8,900+ - 470,000
greater than 470,000
11,000 - 200,000
200,000+ - 2,600,000
greater than 2,600,000
1 - 250
251 - 10,000
greater than 10,000
1,000 - 8,900
8,900+ - 470,000
greater than 470,000
11,000 - 200,000
200,000+ - 2,600,000
greater than 2,600,000
74,000 - 190,000
190,000+ - 21,000,000
greater than 21,000,000
11,000 - 200,000
200,000+ - 2,600,000
greater than 2,600,000
74,000 - 190,000
190,000+ - 21,000,000
greater than 21,000,000
                                 55

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                        TABLE  11  (Concluded)
           Descriptor

Landfill (square feet)
         Small
         Medium
         Large

Open Pit (cubic feet)
         Small
         Medium
         Large

Open Pit (square feet)
         Small
         Medium
         Large

Spill  Site (square feet)
         Small
         Medium
         Large

Surface Impoundment  (cubic feet)
         Small
         Medium
         Large

Surface Impoundment  (square feet)
         Small
         Medium
         Large

Surface Water Body or Outfall (square feet)
         Small
         Medium
         Large

Waste Pile (cubic feet)
         Small
         Medium
         Large

Waste Pile (square feet)
         Small
         Medium
         Large
    Size Range
11,000 - 28,300
28,300+ - 790,000
greater than 790,000
74,000 - 190,000
190,000+ - 21,000,000
greater than 21,000,000
11,000 - 28,300
28,300+ - 790,000
greater than 790,000
11,000 - 200,000
200,000+ - 2,600,000
greater than 2,600,000
1,000 - 8,900
8,900+ - 470,000
greater than 470,000
300 - 2,700
2,700+ - 71,000
greater than 71,000
300 - 2,700
2,700+ - 71,000
greater than 71,000
130 - 1,300
1,300+ - 88,000
greater than 88,000
36 - 360
360 - 10,600
greater than 10,600
                                 56

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                               TABLE  12

                        OPTION 1A SIZE RANGES
           Descriptor

Belowground/Buried Containers (cubic feet)
         Small
         Medium
         Large

Exposed/Aboveground Containers (cubic feet)
         Small
         Medium
         Large

Contaminated Soil (square feet)
         Small
         Medium
         Large

Inactive Fire Site (square feet)
         Small
         Medium
         Large

Landfarm/Landtreatment (square feet)
         Small
         Medium
         Large

Landfill (cubic feet)
         Small
         Medium
         Large

Landfill (square feet)
         Small
         Medium
         Large

Open Pit (cubic feet)
         Small
         Medium
         Large
    Size Range
1,000 - 8,900
8,900+ - 470,000
greater than 470,000


6 - 1,400
1,401 - 56,000
greater than 56,000
11,000 - 200,000
200,000+ - 2,600,000
greater than 2,600,000
74,000 - 190,000
190,000+ - 21,000,000
greater than 21,000,000
11,000 - 200,000
200,000+ - 2,600,000
greater than 2,600,000
74,000 - 190,000
190,000+ - 21,000,000
greater than 21,000,000
11,000 - 28,300
28,300+ - 790,000
greater than 790,000
74,000 - 190,000
190,000+ - 21,000,000
greater than 21,000,000
                                 57

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                        TABLE 12 (Concluded)
           Descriptor

Open Pit (square feet)
         Small
         Medium
         Large

Spill Site (square feet)
         Small
         Medium
         Large

Surface Impoundment (cubic feet)
         Small
         Medium
         Large

Surface Impoundment (square feet)
         Small
         Medium
         Large

Surface Water Body or Outfall (square feet)
         Small
         Medium
         Large

Waste Pile (cubic feet)
         Small
         Medium
         Large

Waste Pile (square feet)
         Small
         Medium
         Large
    Size Range
11,000 - 28,300
28,300+ - 790,000
greater than 790,000


11,000 - 200,000
200,000+ - 2,600,000
greater than 2,600,000
1,000 - 8,900
8,900+ - 470,000
greater than 470,000
300 - 2,700
2,700+ - 71,000
greater than 71,000
300 - 2,700
2,700+ - 71,000
greater than 71,000
130 - 1,300
1,300+ - 88,000
greater than 88,000
36 - 360
360 - 10,600
greater than 10,600
                                 58

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amount of air contaminants.  The author's opinion is based on the

literature review and a review of the limited air monitoring data

available in the NPL site files and remedial investigation reports.

The quality and coverage of the available monitoring data preclude

the calculation of "objective," frequency-based probabilities.

     The initial values were modified, as necessary, after

consultation with personnel from the EPA Environmental Response

Team, Hazardous Waste Engineering Research Laboratory, and Office

of Air Quality Planning and Standards.  Values for Option 1 and 1A

emission source descriptors are presented in Tables 13 and 14,

respectively.  Values on any other desired scale can be developed by

dividing the listed value by 15 and multiplying by the maximum of

the desired scale.  For example, the value for a small landfarm,

evaluated on a scale of 0 to 20, would be 6/15 x 20 or 8.*

     4.1.2.2  Contaminant Mobility.  Contaminant mobility is

evaluated using the combination of two mobility factors, one

addressing gaseous contaminants, the other addressing particulate

matter.  The gas mobility factor reflects the potential of the

contaminants in a site to migrate through the site to the surface/

air interface and escape as a gas.  The factor is based on three

physiochemical characteristics of the contaminants:  vapor pressure,

Henry's constant, and dry relative soil volatility.  Vapor pressure
*Such changes of scale would require adjustments in the mobility
 factor value scales and in the conversion factors used on the
 worksheets (i.e., 45 and 2,025).
                                 59

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                               TABLE 13

            OPTION 1 EMISSION SOURCE DESCRIPTORS AND VALUES
                                                          Values
ode     Descriptors

01      Aboveground or Iaground Tanks:
          Tanks intact
02      Aboveground or Inground Tanks:
          Tanks broken
03      Active Fire Site
04      Belowground Injection
05      Belowground Tanks
06      Contaminated Surface Soil:
          Background at or above
          analytical detection limit;
          contamination level at or
          below background
07      Contaminated Surface Soil:
          Background at or above
          analytical detection limit;
          contamination level above
          background but not significantly
          above background
08      Contaminated Surface Soil:
          Background at or above
          analytical detection limit;
          contamination level significantly
          above background
09      Contaminated Surface Soil:
          Background below analytical
          detection limit; contamination
          level below analytical
          detection limit
10      Contaminated Surface Soil:
          Background below analytical
          detection limit; contamination
          level above analytical
          detection limit
11      Exposed Drum Site:  Drums broken
12      Exposed Drum Site:  Drums intact
13      Inactive Aboveground Fire Site:
          Re-ignition Expected
14      Inactive Aboveground Fire Site:
          Re-ignition Not Expected
                                                          Medium
8
         10
         10
10
                                   60

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                          TABLE 13  (Concluded)
                                                 	Values
Code     Descriptors                             Small     Medium

 15      Inactive Belowground Fire Site:            4         6
           Re-ignition Expected
 16      Inactive Belowground Fire Site:            2         4
           Re-ignition Not Expected
 17      Landfarm/Landtreatment                     6         8
 18      Landfill:                               	6_     	8_
           With both biodegradable material
           and exposed drums
 19      Landfill:                               	4_     	6_
           With biodegradable material but
           without exposed drums
 20      Landfill:  All other situations         	1_     	3_
 21      Open Pit                                	5      	7_
 22      Spill Site:                                4      	6_
           Spill dry
 23      Spill Site:                             	6_     	8_
           Spill wet
 24      Surface Impoundment:                       6         8
           Dry; evidence of waste
           contamination near surface
 25      Surface Impoundment:                       2         4      	6
           Dry; all other situations
 26      Surface Impoundment:                       5         7      	9
           Wet; evidence of waste
           contamination near surface
 27      Surface Impoundment:                       1         3      	5_
           Wet; all other situations
 28      Surface Water Body or Outfall           	3_     	5_     	7_
 29      Waste Pile                              	5_     	7_     	9_
 30      Emission Sources Not Elsewhere:            3         3      	3_
           Specified
                                    61

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                                TABLE 14

            OPTION 1A EMISSION SOURCE DESCRIPTORS AND VALUES
Code     Descriptors

 01      Active Fire Site

 02      Belowground/Buried Containers

 03      Contaminated Soil

 04      Dry Surface Impoundment

 05      Inactive Fire Site

 06      Intact Exposed/Aboveground
           Containers

 07      Landfarm

 08      Landfill

 10      Nonintact Exposed/Aboveground
           Containers

 10      Waste Pile

 11      Wet Surface Impoundment

 12      Emission Sources Not Elsewhere
           Specified
Values
Small
10
1
6
5
5
1
	 6_
5
8
5
5
3
Medium
10
3
8
7
7
1
	 8_
7
9
7
7
3
Large
10
5
10
9
9
1
10
9
10
10
9
3
                                    62

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provides a measure of the propensity of a contaminant to escape from




a pure liquid or solid.  Henry's constant (defined as the ratio of




the partial pressure of a gas in solution to the mole fraction of




the gas in solution) provides a measure of the propensity of a




contaminant to escape from a solution.  Relative soil volatility is




a measure of the tendency of a gas to move through and escape from




soil.  The derivation of this complex factor is described in Versar,




1984.




     A vector of values for each of these characteristics can be




assigned to a contaminant using the evaluation techniques developed




by Versar and summarized in Table 15.  Versar ranked wastes and




contaminants based on their vapor pressures, Henry's constant and




relative soil volatility in order to identify, for example, highly




volatile wastes.  The associated values were assigned by the author.




Referring to the data presented in Table 8, the vector of mobility




values for phenol would be (2,1,2), while that of dichloroethylene




would be (3,3,3).




     An average of the three values for five contaminants present on




the site is used in evaluating the gas mobility value.  An average




is used as an attempt to address the effects of co-disposal and




resulting mixing of wastes and waste contaminants.  In theory, the




average of several contaminants characteristics would be a better




estimator of the mobility of contaminants mixed in a matrix than the




characteristics of any single contaminant.  The value of five was
                                 63

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                             TABLE  15

                        GAS MOBILITY VALUES
      Level

     High
     Medium
     Low
     Very Low
Vapor Pressure Mobility (VP)

              Definition

          Above 10 torr*
          Above 10" 3 - 10 torr
          10"5 - 10~3 torr
          Less than 10"^ torr
Value

  3
  2
  1
  0
      Level

     High
     Medium
     Low
     Very Low
   Aqueous Volatility (AQ)

              Definition**

          Above 10~3
          Above ID"5 - 10"3
          10~7 - 10~5
          Less than 10~7
Value

  3
  2
  1
  0
      Level

     High
     Medium
     Low
     Very Low
Relative Soil Volatility (RS)

            Definition***

          Above 1
          Above 10~3 - 1
          10-6 _ 10-3
          Less than 10~"6
Value

  3
  2
  1
  0
  *Torr is a unit of pressure equal to  1/760  of  an atmosphere.
 **Based on Henry's constant.
***flased on dry relative soil volatility as defined in Versar,  Inc.,
   Physical-Chemical Properties  and Categorization of  RCRA Wastes
   According to Volatility,  Final  Draft Report,  Versar,  Inc.,
   Springfield,  VA,  September 28,  1984.
                                 64

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chosen as being large enough to meet the objective of better




estimating overall mobility and as being small enough to be useable




at most sites.




     Since different contaminants are found in different areas of a




site, the choice of contaminants to be used in evaluating gas




mobility should be consistent with the choice of emission source




descriptor for the portion of the site in question to the extent




possible given information about the site.  For example, when




evaluating the landfill portion of a site, only those contaminants




found in the landfill portion should be used in evaluating the gas




mobility value.  As many contaminants as possible (up to five) should




be used in this calculation.  The methodology will accommodate less




than five contaminants without penalizing the site, since the average




of the nonzero values is used.  The approach for evaluating gas




mobility is summarized in Table 16.  An example calculation of the




gas mobility factors value for a hypothetical site is given in




Appendix C (Table C-12).




     Particulate mobility reflects the potential for particles on




the surface of a site to be formed and entrained in the atmosphere,




escaping from the site.  These particles may be contaminated soil,




dry hazardous substances (such as asbestos), or liquid aerosols.




The approach taken in the particulate mobility factor is based on




the equation for fugitive dust emissions from a limited particle




reservoir developed by Cowherd et al. (1985).  The limited reservoir
                                 65

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(1)

(2)

(3)

(4)

(5)
                              TABLE 16

                 METHOD FOR EVALUATING  GAS MOBILITY


                Emission Source Descriptor Code 	

      Contaminant        VP          AQ            RS
          Code          Value        Value         Value          Sum
(6)   Average of  nonzero  values  in  last column of
      lines 1 through 5
                        GAS MOBILITY TABLE
         	Range of Average  Value	
         Greater than
         or  equal  to             Less  than             Value

              0                        30
              3                        5                  1
              5                        7                  2
              7                      10                  3
                                66

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equation was chosen after consultation with Gregory Muleski (a




co-author of the above report) as being most applicable to CERCLA




sites.  In simplifying this equation for use in these HRS options,




the assumption is made that the three controlling factors in fugitive




emissions (erosion force, threshold wind speed, and Thornthwaite




PE Index) are equally applicable to both "solid" waste materials




and liquid aerosols.




     The approach taken is a simplification of the Cowherd et al.




equations.  Other factors included in the equations but excluded here




are frequency of disturbance and vegetative cover.  The frequency of




disturbance is not included as (1) not generally differentiating




among CERCLA sites and (2) too difficult to estimate.  Vegetative




cover is addressed in the containment factor.




     Using the reduced form of the Cowherd et al. equation, the




following particulate mobility index (I) is defined:



                         I =  (u+ - ut)/(PE)2




where:  u    = Fastest mile at nearest airport (meters per second)




        u    = Threshold wind speed at 7 meters (meters per second)




        PE   = Thornthwaite PE Index




     The fastest mile (u ) is defined as the velocity of the




fastest wind the duration of which was equivalent to a travel




distance of one mile.  For example, in order for a wind speed of




120 miles per hour to be a fastest mile, the duration of the




associated wind would have to exceed 30 seconds.  In this equation,
                                 67

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it is a measure of the force that the wind applies In eroding soil.




For the purpose of determining site particulate mobility, the average




of the monthly, historical fastest miles is used as u .   This




average is used rather the historical maximum, since the average is




a better measure of the wind erosion force that would be routinely




applied to the site.  The historical fastest mile is simply the




maximum of the monthly fastest miles and is potentially very



sensitive to very rare events, e.g., tornados.  As such, it is not




as good a measure of routine wind erosion force as the average of




the monthly fastest miles.




     Data on the fastest mile can be obtained from the Local




Climatological Data Annual Summaries (LCD) for the latest available




year, listed under the Normals, Means, and Extremes.  Data for the




weather station that is closest to the site and listed in the LCD




should be used.




     The threshold wind speed (u ) is the minimum speed required




to entrain particles.   It can be estimated using the procedure in




Cowherd et al. or it may be assumed to be 12.5 meters per second.




This latter, worst-case value is based on a threshold friction




velocity of 75 centimeters per second (the lowest for which the




limited reservoir equation is applicable) and a roughness height




of 1 centimeter (corresponding to a plowed field).  Cowherd et al.




describes the procedure for deriving the default threshold wind




speed.
                                 68

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     The Thornthwaite PE Index is a surrogate measure of the relative




moisture content of the soil.  It can be read from Figure 2, or




calculated as follows (Thornthwaite, 1931):




                 12
          PE =         115 x [P/d  - 10)]10/9
where:  PE   =  Thornthwaite PE Index




        P.   =  Mean precipitation for month i in inches




        T.   =  Mean temperature for month i in degrees F




     Data on the mean precipitation and temperatures for each month




can also be found in the LCD.  Again, data for the weather station




nearest to the site and listed in the LCD should be used.




     Once the particulate mobility index I has been calculated,  the




particulate mobility factor value is calculated as follows:




          Particulate Mobility Value = 4 + log1Q I




rounded-off to the nearest whole number.  If log,Q I exceeds 4,




the factor is assigned a value of 0.  If log-,Q I is less than 0.5




(i.e., the calculated value would exceed 3) then the factor is



assigned a value of 3.  The value of 4 in the formula is a scaling




factor needed to adjust the value to a scale of 0 to 3.  Table 17




provides an equivalent way to determine the particulate mobility




value from the index without requiring the calculation o'f log,Q I.




The alternate is derived directly from the above equation.  An




example of the calculation of the particulate mobility index,
                                 69

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Source: Cowherd et al., 1985
                                         FIGURE 2
                      MAP OF PE INDEX FOR STATE CLIMATIC DIVISIONS

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                        TABLE 17

             ALTERNATE METHOD FOR ASSIGNING
           PARTICULATE MOBILITY FACTOR VALUES
      Particulate                             Particulate
   Mobility Index (I)                        Mobility Value

Less than 3.16 x 10~4                               0

3.17 x 10~4 - 3.16 x 10~3                           1

3.17 x 10~3 - 3.16 x 10~2                           2

Greater than 3.17 x 10~2                            3
                           71

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employing the equation for the Thornthwaite PE Index,  is  presented

in Appendix C (Table C-13).

     The expected distribution of locations in the United States

according to particulate mobility value is indicated below:

              Value                   Percent of Sites

                0                             6
                1                            47
                2                            31
                3                            16

This distribution was developed using data from a random selection

of 30 airports across the country.  To the extent that the geographic

distribution of airports is indicative of the distribution of sites,

this distribution of particulate mobility values reflects the

distribution of hazardous wastes sites particulate mobility values,

as well.

     The combined mobility value is calculated from the gas and

particulate mobility values using Table 18.  If a scale other than 0

to 5 is desired, it can be calculated by multiplying the values by

the ratio of the maximum of the desired scale and 5.*

     4.1.2.3  Containment.  Containment refers to the physical

characteristics of a site that inhibit or reduce emissions.   It is

generally the most important determinant of the emission rate at a

site.  Containment-related characteristics range from natural factors
*In such cases, adjustments would also have to be made to the
 emission source descriptor and containment values as well as to the
 conversion factors employed on the worksheets.
                                 72

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                TABLE 18




     COMBINED MOBILITY FACTOR MATRIX
                    Gas Mobility Value




                    0     1     2    3




Particulate    0:   0     1     23




Mobility       1:1     2     34




Value          2:   2     3     45




               3:   3     4     55
                   73

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such as vegetative cover to artificial, synthetic covers.  Separate




containment factors were developed for gas and particulate containment.




There are also sufficient differences among the containment factors




that might be associated with different types of sites to require that




different containment descriptors be developed for each emission




source descriptor.  Many emission source descriptors share the same or




similar containment descriptors.  Numerous sources were examined to




develop containment factors.  The most important sources are listed in




Section 8.3.




     Once the containment descriptors were developed, a subjective




assessment of their efficiency in reducing potential emissions was made




and values assigned.  The descriptors and values were then reviewed in




conjunction with the emission source descriptors and values and changes




made as necessary.  Table 19 lists examples of the gas and particulate




containment factors and values.  The combined containment value is




calculated from the gas and particulate containment values using




Table 20.  Complete lists of containment factors for both options can




be found in Appendix D.




     The choice of an applicable containment descriptor depends on the




judgment of the analyst evaluating the site.  Containment should be




evaluated, however, in the area of the hazardous contaminants.  It




should reflect the barriers to contaminant migration present on the




site.   For example, assume a site contains two tanks; one containing




hazardous waste,  the other containing liquids of unknown composition.
                                 74

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                              TABLE 19

             EXAMPLES OF CONTAINMENT FACTORS AND VALUES


Particulate C oatainment—Landfill                               Value

•  Site covered with an essentially impermeable and               0
   maintained cover or heavily vegetated with no exposed
   soil or waste-bearing liquids (e.g., paved-over).
•  Site substantially vegetated or totally covered                1
   with a maintained nonwater-based dust suppressing
   fluid.  Little exposed soil or waste-bearing liquids.
•  Site lightly vegetated or partially covered with a             2
   maintained nonwater-based dust suppressing fluid.
   Much exposed soil or waste-bearing liquids.
•  Site substantially devoid of vegetation with a large           2
   percentage of exposed soil or waste-bearing liquids.
   No other cover.  Facility slope less than 10 degrees
   or unknown.
•  Site substantially devoid of vegetation with a large           3
   percentage of exposed soil or waste-bearing liquids.
   No other cover.  Facility slope greater than 10 degrees.


Gas Containment—Landfill                                       Value

•  Uncontaminated soil cover in excess of six inches.             0
•  Uncontaminated soil cover greater than one inch and            1
   less than six inches; cover soil resistant to gas
   migration.
•  Uncontaminated soil cover less than six inches; cover          1
   soil type unknown.
•  Uncontaminated soil cover greater than one inch and            2
   less than six inches; cover soil not resistant to gas
   migration.
•  Uncontaminated soil cover less than one inch; cover soil       2
   resistant to gas migration.
•  Uncontaminated soil cover less than one inch; cover soil       3
   not resistant to gas migration.
•  Covering soil contaminated with waste contaminants at          3
   surface and no synthetic cover between surface and bulk
   of waste materials.
                                 75

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                TABLE  20




   COMBINED CONTAINMENT FACTOR MATRIX
                    Gas Containment Value




                    0      1      2     3




Particulate    0:    0      1      2     3




Containment    1:1      1      2     3




Value          2:    2      2      2     3




               3:    3      3      33
                  76

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Assume also that the tank with known contents is structurally intact




while the other tank is not.  The containment for the tanks should be




evaluated based on the intact, known-waste tank, not the nonintact




tank.




     4.1.2.4  Potential to Release Scoring Algorithm.  The algorithm




used to combine the size-dependent emission source descriptor,




mobility, and containment values is complex.  In general, several




emission source descriptors will apply to a given site.   Given this




consideration and the differences between emission source descriptor




values, several descriptors are needed to adequately evaluate the




potential of a site to release contaminants.  Both Option 1 and 1A




provide for the use of up to three descriptors for a site.  The use




of more than three descriptors would introduce a level of complexity




into the resulting calculations that is not commensurate with




possible gains in the site assessment results.  The descriptors




selected by the person evaluating the site, therefore, should be




the three that best describe the emission potential of the site.




Mobility and containment values are evaluated for each descriptor




selected based on the characteristics of the site and its




contaminants to which the descriptor applies.  A total value for




each descriptor is calculated as the sum of the size-dependent




emission source descriptor value and the combined mobility value




multiplied by the combined containment value.  The three resulting




values are then combined, using the equation for the probability of
                                 77

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the union of three independent events,* to form a site potential to

release value.   This method of calculating site potential to release

values is illustrated in Table 21.  This approach is recommended

since it is the only approach consistent with the underlying

assumption that the release category reflects the probability that

some portion of the site has, is, or will release a significant

quantity of air contaminants.

4.2  Waste Characteristics Category

     The waste characteristics category reflects the degree of hazard

posed by the contaminants that are, or might be, released from the

site.  In both Option 1 and 2, three waste characteristics are

included in this category:  contaminant toxicity, contaminant

mobility, and waste quantity.  The reactivity/incompatibility factor

currently in the HRS is not included in these options.  This factor

was not included in the options pending the results of a separate

analysis (DeSesso et al., 1986).

     It would be desirable to include a fourth characteristic,

contaminant concentration.  The incorporation of this factor is not

feasible at this time and awaits completion of an independent review

of the overall waste concentration issue.


*The probability (Pr) of the union of three independent events (A, B,
 and C) is given by the following equation:

     Pr(A U B U C)  -  Pr(A) + Pr(B) + Pr(C) - Pr(A)Pr(B) -
                      Pr(A)Pr(C) - Pr(fl)Pr(C) + Pr(A)Pr(B)Pr(C)
                                 78

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                               TABLE 21

           METHOD OF CALCULATING OVERALL SITE RELEASE VALUE
Descriptor
Code

(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)




(D+
(1) x
(1) x
(2) x
(1) x
(4) -
Des. Mobility Containment
Size Value Value Sum Value Product
(A) (B) (A+B) (C) ([A+B]xC)



(2)+ (3) 	
(2) / 45 	
(3) / 45 	
(3) / 45 	
(2) x (3) /2025 	
(5) - (6) - (7) + (8) 	
Site Release Value


Note:  The values of 45 and 2025 used in this method arise from the
       conversion of the combined probability to a value on a scale of
       0 to 45.  If another scale is used, alternate values must be
       developed and employed.
                                 79

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     The current HRS uses the single most toxic contaminant on the




site, available for migration, in assessing toxicity.  Availability




is based primarily on containment considerations.  If the contaminant




is not contained by a physical barrier, it is considered available.




Both options presented here envision using the single most mobile




and toxic contaminant on the site.  To achieve this, a combined




toxicity-mobility evaluation approach is used.  This approach weighs




toxicity and mobility nearly equally, although a slightly greater




emphasis is placed on toxicity in the evaluation.  The contaminant




mobility evaluation approach used in this factor is similar to that




used in the potential-to-release mobility factor.  In the release




category, however, mobilities of several contaminants were combined




to form an overall site mobility value.  Here, the Individual




contaminant mobilities are used to identify and evaluate the most




toxic, most mobile contaminant.




     In these options, contaminant toxicity is assessed using the




same methods as the current HRS (47 FR 31219-31243).  The proposed




method can be readily modified to accommodate other methods of




assessing toxicity, such as are proposed in OeSesso et al., 1986.




     Contaminant mobility is assessed as follows.  If the contaminant




has been identified as being emitted from the site in an observed




release,  it is assigned a mobility value of 3.  If the contaminant




has not been identified as part of an observed release, its mobility




factor value is assigned differently.  Mobility values for
                                 80

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particulate contaminants that have not been identified as being




emitted from the site are evaluated using the particulate mobility




factor discussed previously.  The assumption is made, therefore,




that the particulate mobility factor value for the overall site




applies to all particulate contaminants.  The mobility value for a




nonemitted gaseous contaminant is calculated as the average of its




vapor pressure, Henry's constant and dry relative soil volatility




values according to Table 15.  The mobility value for a contaminant




present as both a gas and a particle is the greater of the applicable




gas and particle mobility values.  The combined toxicity-mobility




value for a particular contaminant is calculated using Table 22.




The combined toxicity-mobility value for the site is the maximum of




the combined toxicity-mobility values for the contaminants identified




on the site.



     The waste quantity factor is identical to the factor in the




current HRS (47 FR 31219-31243).



     The overall waste characteristics value is the sum of the




toxicity-mobility value and the waste quantity value.




4.3  Targets Category



     The targets category reflects the extent of the population and




resources potentially at risk from contaminants that might be




released from the site.  Three factors are included:  population,




land use, and sensitive environment.  The tables used to assign




values for each factor, in each option, are the same as are






                                 81

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                TABLE 22




COMBINED TOXICITY-MOBILITY FACTOR MATRIX
                      Mobility Value




                    0    1    _2    _3




               0:    0    0     0     0




Toxicity       1:    0    2     4     6




Value          2:    2    4     8    12




               3:    4    6    12    18
                  82

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currently used in the HRS (47 FR 31219-31243).  The changes




envisioned in these options address the selection of location for




the center of the circles used in evaluating population, the size of




the radii of these circles, and the use of 1980 (or later, as




available) Census data to determine population.  The current HRS




employs a simplistic approach to population estimation.   As




discussed previously, it relies routinely on house counts in the




area surrounding the site and coverts these data into equivalent




population assuming persons per household.  The number of households




is frequently derived from outdated maps of the area.  The current




HRS also calculates the target distance from the location of the




wastes, or if that information is not available, from the site




boundary, using fixed target distances.  This approach is illustrated




in Table 23, the current HRS air pathway population factor matrix.




If, for example, 50 people live within 1/4 mile of a site (value = 18),




while 2,000 people live within 1/2 mile of the site (value = 21), the




site would be assigned a population factor value of 21.




     Improvements of this overall approach is embedded in both




options.  The improvements do not address the way the population




factor is evaluated, rather they address the way the size of the




target population is determined.  The options envision that the




following approach would be employed unless the local governmental




authority can provide better data.  The approach is based on the




Bureau of the Census computer program, called RADII5.  This publicly
                                 83

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                 TABLE 23

CURRENT HRS TARGET POPULATION FACTOR MATRIX
               Distance to Population From
               Hazardous Substance (mile)
Population

1
101
1,001
3,001
10,
0
- 100
- 1,000
- 3,000
- 10,000
000+
0-4
0
9
12
15
18
21
0-1
0
12
15
18
21
24
0-1/2
0
15
18
21
24
27
0-1/4
0
18
21
24
27
30
                    84

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available computer program calculates the population reported in the

1980 Census in circles of user specified radii around any location

in the United States.  Both Options 1 and 1A envision that EPA. would

acquire these programs, modify them as necessary, and provide results

to persons evaluating sites as needed.

     The use of this data source would require a change in the way

target distance is calculated in the air pathway.  The easiest

approach consistent with the requirements of the RADII5 program is

to employ circles of varying radii, defined in terms of an effective

source radius plus a target distance, centered at the "center of

gravity" of the site.  The effective source radius is defined as

1/2 of the greatest distance between any two identifiable emissions

sources on the site.*  Thus if the site contains only two

identifiable sources, the effective source radius equals 1/2 of the

distance between them.  If the site contains more than two sources,

then the radius equals 1/2 of the distance between the two that are

furthest apart.

     Neither of these two modifications would affect the way targets

are evaluated in the air pathway.  The overall targets category

value would remain the sum of the population, land use, and

sensitive environment values in both Option 1 and 2.
*ln evaluating the distance between identifiable emission sources,
 the distance should be calculated from the respective centers of
 the sources.
                                 85

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4.4  The Overall Pathway Score




     As discussed previously,  the overall pathway score is the




product of the release category,  waste characteristics category




and targets category scores, normalized to a scale of 0 to 100.




The calculation of the release category score is discussed la




Section 4.1.  The waste characteristics category score is the sum of




the toxicity-mobility value and the waste quantity value.  Similarly,




the targets category score is  the sum of the population,  land use




and sensitive environment values.   This approach is Illustrated in



Table 24.
                                86

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                              TABLE 24

              METHOD OF CALCULATING AIR PATHWAY SCORE
 1.  OBSERVED RELEASE VALUE3

 2.  POTENTIAL TO RELEASE VALUEb
 3.   TOXICITY-MOBILITYC

 4.   HAZARDOUS WASTE QUANTITYd
 5.  WASTE CHARACTERISTICS VALUE (Lines 3+4)

 6.  TARGETS

 7.      Population                    	

 8.      Land Used
 9.      Sensitive Environment         	

10.  TARGETS VALUE (Lines 7+8+9)

11.  If line 1 is not equal to 0.0,
     multiply lines 1 x 5 x 10
     If line 2 is not equal to 0.0,
     multiply lines 2 x 5 x 10

12.  Divide line 11 by 351                      S
aFrom Worksheet 1.
^From Worksheet 2.
cFrom Worksheet 7.
dFrom HRS User's Manual.
                                                  a
                                 87

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5.0  SINGLE, "WORST" SOURCE APPROACH (OPTION 2)




     The principal purpose of this section is to describe a simple




mechanism for evaluating hazardous wastes sites based on their




potential to release CERCLA contaminants into the air, in the absence




of an observed release.  The mechanism is closely related to the




approach described in Section 4.  This simple approach is designed




to be consistent with the assumptions and approaches embodied in the




current HRS.  It is designed to be implemented with a minimum of




change to the other components of the air pathway, as they currently




exist.  As such, it does not address any issues in the HRS other




than the absence of a potential to release option in the current air




pathway.  Alternately, this mechanism can be integrated with the




suggested revisions to the waste characteristics and targets




categories discussed in Section 4 to form another overall revision




option.




     The approach described in this section follows the same general




approach as is used in the ground water and surface water pathways.




If an observed release can not be demonstrated, then the site release




category is evaluated based on the characteristics of that portion




of the site that is most likely to release contaminants to the




applicable medium.   Thus, the Option 1 multiple source approach




employing probabilistic combinatorics is replaced in Option 2 by a




simpler, "worst" source approach.   Additionally, in Option 2 the




list of emission source descriptors is simplified with resulting
                                 89

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simplifications in the containment descriptors.  Further, size is




reflected as a constraint on the selection of descriptors and does




not affect the emissions source descriptor values.




     The following sections described this alternate approach to




assessing potential to release in more detail.  An example of the




application of this approach to a hypothetical site is presented in




Appendix C.




5.1  The Option 2 Potential to Release Evaluation Mechanism




     The approach reflected in the simplified mechanism discussed




below uses information on the physical characteristics of the site




and the waste in the site.  Four site characteristics are employed




in assessing the potential of a site to emit air contaminants:




     •  Emission source descriptor




     •  Size




     •  Overall contaminant mobility




     •  Containment




The first two characteristics are reflected into a single factor,




although in a somewhat different fashion than is used in Options 1




and 1A.   These characteristics are discussed in detail in




Section 4.1.2.




     The overall approach to evaluating the potential of a site to




release  contaminants using Option 2 is similar to that of Options 1




and 1A discussed previously.  The emission sources on the site  are




classified using emission source descriptors.  The size of each
                                 90

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emission source is also assessed.  From this information, a emission

source descriptor factor value is calculated for each descriptor

meeting the applicable minimum size requirement.

     Up to five contaminants present in the site are used to calculate

a gaseous contaminant mobility value for each applicable emission

source descriptor.  This value is based on the average physiochemical

characteristics of the contaminants associated with each descriptor.

A particulate mobility value for the site is then calculated based on

the Thornthwaite PS Index (Thornthwaite, 1931) for the area surrounding

the site.  The combined mobility value is the sum of the gaseous and

particulate mobility values.  This causes the mobility factor to play

a slightly greater role, relative to the emission source descriptors,

in determining the potential to release value in Option 2 than in

Option 1.

     The gas and particulate containment aspects of the area

represented by the selected descriptors are then assessed and evaluated

separately.  A combined containment value is then evaluated from the

gas and particulate containment values.

     The sum of the descriptor and mobility values is then multiplied

by the containment value to form the potential to release value for

the selected descriptor.  This procedure is illustrated in Table 25.

The highest of the calculated descriptor factor values is taken as the

potential to release value in the air pathway for the site.  Thus,

this approach employs the "worst" source in evaluating potential to

release.
                                 91

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                              TABLE 25

               ILLUSTRATION OF OPTION 2 POTENTIAL TO
                    RELEASE EVALUATION PROCEDURE
A)  Emission Source Descriptor Value

B)  Gas Mobility Value

C)  Particulate Mobility Value

D)  Subtotal (A + B + C)

E)  Particulate Containment Value

F)  Gas Containment Value

G)  Combined Containment Value Maximum of
      E and F

H)  Emission Source Potential to Release
      Value (D x G)
                                 92

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     5.1.1  Emission Source Descriptors




     A basic list of emission source descriptors is presented in




Table C-l.  The relationship between the reduced list used in this




simpler option and the original list is presented in Table 26.




     The choice of emission source descriptor is left up to the




investigator evaluating the site.  The restrictions to descriptor




selection are generally the same as those discussed for Options 1




and 1A (see Section 4.1.2.1).  However, since the emission source




descriptor values do not vary according to size in Option 2,  size is




employed as a constraint on the selection of descriptors.




     Minimum size requirements were adapted from the three size




categories defined in Section 4.1.2.1.  These requirements are listed




in Table 27.  The size constraint imposed on the selection of




emission source descriptors in Option 2 is similar to that used in




the other options.  Generally, the size of the source described by




a selected descriptor must equal or exceed the minimum listed in




Table 27, if that descriptor is to be used in evaluating the  site.




The sole exception to this rule applies when this constraint  can not




be met by any descriptor.   In this case, the "largest" descriptor




(relative to the size requirement) is used to evaluate the site, as




in done in Options 1 and 1A.




     The emission source descriptors values presented in Table 28




are adapted from the larger list of size-dependent emission source




descriptor values listed in Table 13.






                                 93

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                              TABLE 26

        OPTION 2 EMISSION SOURCE DESCRIPTORS AND DEFINITIONS
Option 2 Emission                      Option 1 Emission
Source Descriptor                      Source Descriptor	

Containers                         Aboveground or Inground:
                                      Tanks (All variations)
                                   Belowground Tanks
                                   Exposed Drum Site:
                                      (All variations)

Contaminated Soil                  Contaminated Surface  Soil:
                                      (All variations)
                                   Spill Site

Fire Site                          Active Fire Site
                                   Inactive Aboveground  Fire  Site:
                                      (All variations)
                                   Inactive Belowground  Fire  Site:
                                      (All variations)

Landfill                           Belowground Injection
                                   Landfarm/Landtreatment
                                   Landfill:   (All variations)
                                   Open Pit

Surface Impoundment                Surface Impoundment:
                                      (All variations)
                                   Surface Water Body or Outfall

Waste Pile                         Waste Pile
                                 94

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                              TABLE 27

                 OPTION 2 MINIMUM SIZE REQUIREMENTS
           Descriptor

Containers

    Belowground Tanks
    Drum Site
    Inground or Aboveground Tanks

Contaminated Soil

Fire Site

    Aboveground Fire Site
    Belowground Fire Site

Landfill


Surface Impoundment


Waste Pile
  Minimum Size
1,000 cubic feet
1 drum
1,000 cubic feet

11,000 square feet
11,000 square feet
74,000 square feet

11,000 square feet
74,000 cubic feet

1,000 cubic feet
300 square feet

130 cubic feet
36 square feet
                                 95

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                    TABLE 28




   OPTION 2 EMISSION SOURCE DESCRIPTOR VALUES






Code            Descriptors                 Value




 01           Containers                       4




 02           Contaminated Soil                7




 03           Fire Site                        5
 04           Landfill                      	6_




 05           Surface Impoundment              8




 06           Waste  Pile                       3
                      96

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     5.1.2  Contaminant Mobility




     As in Options 1 and 1A (see Section 4.1.2.2), contaminant mobility




is reflected using the combination of two mobility factors, one




addressing gaseous contaminants, the other addressing particulate




matter.  The value for the gas mobility factor is determined in the




same manner as in Option 1.




     The particulate mobility factor in Option 1 is based on the




equation for fugitive dust emissions from a limited particle reservoir.




Three factors were retained for tne Option 1 mechanism:   erosion force,




threshold wind speed, and Thornthwaite PE Index.   An analysis of the



values for the particulate mobility factor in Option 1,  based on data




from randomly selected airports, indicated that the Thornthwaite PE




Index dominates the particulate mobility evaluation.  Thus, a




simplified, single variable factor employing the PE index alone can be




used, sacrificing only some of the resolution provided by the more




complex approach.  This simpler approach is summarized in Table 29.




The PE index for a site can be determined from Figure 2,  or from the




complex equation described in Section 4.1.2.2.   This simpler approach




yields nearly the same result as the more complex approach in




Option 1.  The values for only 7 of the over 30 sites examined were




significantly affected by the erosion force and wind speed values.




The approach presented in Table 29 results in the same particulate




mobility factor value for all but these 7 sites,  and higher values for




5 of these 7.






                                 97

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                      TABLE 29

        OPTION 2 PARTICULATE MOBILITY FACTOR



                                      Paniculate
Thornthwaite PE Index                Mobility Value

   Greater than 100                        0

      70 to 100                            1

      34 to 69                             2

    Less than 34                           3
                        98

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     5.1.3  Containment




     The factor value for containment is determined in Option 2  the




same way as in Option 1 (see Section 4.1.2.3).   The list of  Option 2




containment descriptors is also adapted from the more extensive  list




prepared for Option 1.  These descriptors are listed in Tables 30




and 31.  The combined containment value is determined from the gas




and particulate containment values using the Option 1 approach




(Table 20).
                                 99

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                              TABLE 30

              OPTION 2 PARTICULATE CONTAINMENT FACTORS
CONTAINERS

   C001P    Belowground/buried containers:   (see Landfill,
              etc.)
   C002P    Intact, sealed aboveground containers;
              containers protected from the weather by
              a maintained cover
   C003P    Intact, sealed aboveground containers;
              containers not protected from the weather by
              a maintained cover
   C004P    Open, unsealed, or nonintact aboveground
              container; waste totally covered with an
              essentially impermeable, maintained cover
   C005P    Open, unsealed, or nonintact aboveground
              container; waste partially covered with an
              essentially impermeable, maintained cover
   C006P    Open, unsealed, or nonintact aboveground
              container; waste totally covered with an
              essentially impermeable, unmaintained cover
   C007P    Open, unsealed, or nonintact aboveground
              container; waste otherwise covered or uncovered
   C008P    Aboveground containers;  other

LANDFILL, CONTAMINATED SOIL, FIRE SITE, AND WASTE PILES

   LD01P    Site covered with an essentially Impermeable
              and maintained cover or heavily vegetated
              with no exposed soil or waste-bearing liquids
              (e.g., paved-over)
   LD02P    Site substantially vegetated or totally covered
              with a maintained nonwater-based dust
              suppressing fluid.  Little exposed soil or
              waste-bearing liquids
   LD03P    Site lightly vegetated or partially covered
              with a maintained nonwater-based dust
              suppressing fluid.  Much exposed soil or
              waste-bearing liquids
   LD04P    Site substantially devoid of vegetation with
              a large percentage of  exposed soil or
              waste-bearing liquids.  No other cover
   LD05P    Totally enclosed in a structurally intact
              building
                                 100

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                        TABLE 30 (Concluded)
LANDFILL, CONTAMINATED SOIL, FIRE SITE, AND WASTE PILES (Concluded)

   LD06P    Partially enclosed in a structurally intact         	2_
              building
   LD07P    Totally enclosed in an nonintact building           	2_
   LD08P    Partially enclosed in an nonintact building         	3_
   LD09P    Substantially surrounded with windbreak             	2_
              (e.g., mesh or other fence, trees, etc.)
   LD10P    Active fire site                                    	3_
   LD11P    Other                                                 1
SURFACE IMPOUNDMENT

   SI01P    Enclosed* impoundment; impoundment totally
              covered with a maintained cover
   SI02P    Enclosed impoundment; impoundment totally
              covered with an unmaintained cover
   SI03P    Enclosed impoundment; impoundment partially
              covered with a maintained cover
   SI04P    Enclosed impoundment; impoundment partially
              covered with an unmaintained cover
   SI05P    Enclosed impoundment; uncovered, surface
              completely open to atmosphere
   SI06P    Nonenclosed impoundment; impoundment totally
              covered with a maintained cover
   SI07P    Nonenclosed impoundment; impoundment totally
              covered with an unmaintained cover
   SI08P    Nonenclosed impoundment; impoundment partially
              covered with a maintained cover
   SI09P    Nonenclosed impoundment; impoundment partially
              covered with an unmaintained cover
   SHOP    Nonenclosed impoundment; uncovered, surface
              completely open to atmosphere
   SHIP    Other
*An enclosed impoundment is one with a freeboard exceeding two feet
 in height or one that is substantially surrounded by a wall, fence,
 trees, or other adequate windbreak.
                                 101

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                              TABLE 31

                  OPTION 2 GAS CONTAINMENT FACTORS
CONTAINERS

  C001G

  C002G


  C003G


  C004G


  C005G


  C006G


  C007G

  C008G

FIRE SITE

  FS01G
  FS02G
  FS03G

  FS04G
Belowground/burled containers:  (see
  Landfill, etc.)
Intact, sealed aboveground containers;
  containers protected from the weather by
  a maintained cover
Intact, sealed aboveground containers;
  containers not protected from the weather by
  a maintained cover
Open, unsealed, or nonintact aboveground
  container; waste totally covered with an
  essentially impermeable, maintained cover
Open, unsealed, or nonintact aboveground
  container; waste partially covered with an
  essentially Impermeable, maintained cover
Open, unsealed, or nonintact aboveground
  container; waste totally covered with an
  essentially impermeable, unmaintalned cover
Open, unsealed, or nonintact aboveground
  container; waste otherwise covered or uncovered
Aboveground containers; other
Inactive fire site:  (see Landfill, etc.)
Active aboveground fire site
Active belowground fire site:  Uncontamlnated*
  soil cover in excess of two feet
Active belowground fire site:  Uncontamlnated*
  soil cover less than two feet, soil resistant
  to gas migration**
 ^Lacking contrary evidence, covering soils are assumed to be
  uncontamlnated.  Soil cover contaminants must be attributable to
  the underlying waste materials and gaseous in origin.
**USGS soil types GC, ML, CL, and CH.  Source:  Adapted from
  Lutton, R. J., Evaluating Cover Systems for Solid and Hazardous
  Wastes, (EPA-530/SW-867c),  U.S. Environmental Protection Agency,
  Washington, DC, September 1980.
                                 102

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                        TABLE 31 (Continued)
FIRE SITE (Concluded)

  FS05G     Active belowground fire site:  Uncontaminated*
              soil cover less than two feet, soil not
              resistant to gas migration**

LANDFILL. CONTAMINATED SOIL, AND WASTE PILES

  LD01G     Functioning gas collection system
  LD02G     Existing, malfunctioning gas collection system
  LD03G     Intact synthetic cover plus uncontaminated soil
              cover over 0.5 inches in depth*
  LD04G     Totally covered with an intact synthetic
              cover; surface soil contaminated*
  LD05G     Totally covered with a nonintact synthetic
              cover; surface soil contaminated*
  LD06G     Uncontaminated soil cover* in excess of six
              inches
  LD07G     Uncontaminated soil cover* greater than one
              inch and less than six inches; cover soil
              resistant to gas migration**
  LD08G     Uncontaminated soil cover* less than six inches;
              cover soil type unknown
  LD09G     Uncontaminated soil cover* greater than one
              inch and less than six inches; cover soil not
              resistant to gas migration**
  LD10G     Uncontaminated soil cover* less than one inch;
              cover soil resistant to gas migration**
  LD11G     Uncontaminated soil cover* less than one inch;
              cover soil not resistant to gas migration**
  LD12G     Covering soil contaminated* with waste
              contaminants at surface and no synthetic
              cover between surface and bulk of waste
              materials
 *Lacking contrary evidence, covering soils are assumed to be
  uncontaminated.  Soil cover contaminants must be attributable to
  the underlying waste materials and gaseous in origin.
**USGS soil types GC, ML, CL, and CH.  Source:   Adapted from
  Lutton, R. J., Evaluating Cover Systems for Solid and Hazardous
  Wastes, (EPA-530/SW-867c), U.S. Environmental Protection Agency,
  Washington, DC, September 1980.
                                 103

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                        TABLE 31 (Concluded)


LANDFILL, CONTAMINATED SOIL,  AND WASTE PILES (Concluded)

  LD13G     Totally enclosed in a structurally Intact
              building
  LD14G     Totally enclosed in an nonintact building
  LD15G     Waste uncovered or exposed
  LD16G     Other

SURFACE IMPOUNDMENTS

  SI01G     Dry surface impoundment (see Landfill, etc.)
  SI02G     Wet enclosed* impoundment; impoundment totally
              covered with a maintained, essentially
              impermeable cover
  SI03G     Wet enclosed impoundment;  impoundment totally
              covered with an unmaintained, essentially
              impermeable cover
  SI04G     Wet enclosed impoundment;  impoundment partially
              covered with a maintained, essentially
              impermeable cover
  SI05G     Wet enclosed impoundment;  impoundment partially
              covered with an unmaintained, essentially
              impermeable cover
  SI06G     Wet enclosed impoundment;  uncovered, surface
              completely open to atmosphere
  SI07G     Wet nonenclosed impoundment; impoundment
              totally covered with a maintained, essentially
              impermeable cover
  SI08G     Wet nonenclosed impoundment; impoundment
              totally covered with an unmaintained,
              essentially Impermeable cover
  SI09G     Wet nonenclosed impoundment; impoundment
              partially covered with a maintained,
              essentially impermeable cover
  SI10G     Wet nonenclosed impoundment; impoundment
              partially covered with an unmaintained,
              essentially impermeable cover
  SI11G     Wet nonenclosed impoundment; uncovered,
              surface completely open to atmosphere
  SI12G   ,  Other
0
*An enclosed Impoundment is one with a freeboard exceeding two feet
 in height or one that is substantially surrounded by a wall, fence,
 trees, or other adequate windbreak.

                                 104

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6.0  IMPLICATIONS




     This section discusses the potential implications of adopting




the proposed revisions to the HRS air pathway.  Implications for the




cost of using the HRS and the listing of sites on the National




Priorities List (NPL) are discussed.  The testing and refinement of



these options is expected to reveal further issues and may resolve




some identified below.




6.1  Improvements in the HRS and the NPL




     The basic purpose in revising the HRS is to improve the




capability of the HRS in identifying sites suitable for inclusion on




the National Priorities List.  This purpose is achieved whenever the




scores for sites calculated using the HRS better reflect the risk




posed by the sites.  Such improvements in the quality of HRS scores




serves to improve the NPL, ensuring that the sites identified as




National Priorities are the sites that should be further




investigated and, if necessary, cleaned up.




     The proposed revisions to the HRS air pathway improves the HRS




in three ways.  First, the revisions address the potential of a site




to release air contaminants, a characteristic currently lacking in




the HRS.   The options account for many of the important factors that




determine the potential to release, although some important




characteristics of a site (e.g., age) are not included.   The




important factors included in the options are the type of emission




source,  size, overall contaminant mobility,  and containment.   As a






                                 105

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result, the risks from potentially important sites at which air




monitoring was not conducted, or proved equivocal, can now be




reflected in a reasonable fashion by the HRS air route score.




     Second, these options resolve a criticism of the waste




characteristics category of the current HRS.  In the current system,




a very toxic contaminant can be used to assign a toxicity value,




whenever there are no physical barriers to contain it on the site,




regardless of whether that contaminant is unable to migrate due to




its chemical properties.  The current approach does not address the




physiochemical characteristics of the contaminant that determine




whether it can migrate, irrespective of containment.  The options




presented propose a method of assigning a value for toxicity that




includes an evaluation of the migration potential of the contaminant.




     Finally, the proposed revision in the approach used in




estimating population should result in the use of more current and




accurate population estimates, improving the quality of the target



factor values.




     The adoption of any of the air pathway options would also




affect the number of sites listed on the NPL.   The inclusion of a




potential to release option is expected to raise the average air




pathway score since many sites that otherwise would receive a zero




air pathway score under the current riRS (those lacking an observed




release) would receive a positive score for potential to release




under the options discussed previously.  Thus, if the requirement






                                 106

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that the site score equal or exceed 28.50 is maintained, then a




greater number of sites would meet this requirement using the options




than would under the current HRS.  This would increase the size of




the NPL.




     It is not possible to determine the fraction of sites that would




be affected.  However, it is possible that most if not all of the




sites that received HRS scores marginally below the cut-off (e.g.,




those scoring between 25.0 and 28.49) may qualify for listing using




the revised HRS.  Table 32 provides the distribution of these



marginal sites and the air pathway scores needed to achieve the 28.50




cut-off.  This table illustrates that at least 58 sites currently not




listed are potential candidates for listing using a revised HRS, if




the cut-off is not changed.




6.2  Cost Implications




     The air pathway revision options were generally developed with




the intent that their adoption would not add significantly to the




costs of using the HRS.  The inclusion of a potential to release




option in the air pathway requires no additional monitoring data.   A




detailed site and containment description, supplemented by site




photographs, should be sufficient to evaluate the site's potential




to release.  Whether this would result in an increase in site




investigation costs is problematic.  However, such a cost increase




would likely be small.
                                 107

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                              TABLE 32

           HRS SCORING DISTRIBUTION FOR  "MARGINAL" SITES
                   LACKING OBSERVED AIR  RELEASES
        Range of          Maximum Points Needed       Number of Sites
     Current Scores      To Equal or Exceed 28.5      in Given Range

     25.00 - 25.49                23.67                      9

     25.49 - 25.00                22.05                      6

     26.00 - 26.49                20.19                     14

     26.49 - 27.00                18.19                      6

     27.00 - 27.49                15.79                      7

     27.49 - 28.00                13.01                      9

     28.00 - 28.49                 9.20                      7

                                                 Total      58
Source:  Based on scores for final and proposed NPL sites that lack
         observed air releases,  proposed through Update 5.
                                108

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     Further, the addition of the mobility factor in the waste




characteristics category should have a negligible cost impact as




it also requires no new data development.  The recommended changes




to the targets category may result in an increase in scoring costs




as they require new data.  If the RADI15 program is adopted,




appropriately modified and made available to the analysts, the cost




for providing population estimates should be no more than $100 per




site.  The costs of modifying the RAD1I5 program will also be small




as the EPA Office of Air Quality Planning and Standards has already




implemented a version of the program on EPA's computer.  Thus,  the




only potentially significant program cost increase that might arise




from incorporating the air revision is the additional analyst costs.




This cost should not exceed the equivalent of 8 person-hours per




site.  These costs may be minimized by developing tables that would




facilitate scoring, eliminating some of the worksheets described in




the appendices.




6.3  Potential Implications for Other HRS Pathways




     Some of the changes to the air pathway envisioned in these




options raise issues for the ground water and surface water pathways,




In general, if the HRS is to remain internally consistent,  should




the other pathways be revised in the same fashion as suggested for




the air pathway?  For example, should the potential to release




options currently employed in the other pathways be revised to




reflect the presence of multiple potential sources using an approach






                                109

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based on probabilistic combinatorics?  The following aspects of the




revisions are of particular importance in this context:




     •  Criteria for observed release




     •  Use of multiple descriptors




     •  Probabilistic scoring algorithm




     •  Use of Census data in targets category




     •  Combined toxicity-mobility factor




     •  Multi-contaminant mobility factor in potential to release




The nature and extent of changes in the other pathways that might




arise from adoption of the air pathway options are unknown.
                                110

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7.0  SUMMARY AND CONCLUSIONS




     This paper has presented three options for revising the HRS air




pathway.  The suggested revisions include a potential to release




option in the release category, a combined toxicity-mobility factor




in the waste characteristics category, and revisions in the target




distance and population estimation procedures in the targets




category.  Adoption of the suggested revisions would improve the HRS




and the NPL by increasing the degree to which HRS scores reflect the




potential risks from hazardous wastes sites and, as a result, by




providing better discrimination among potential NPL sites.




     Since these options would constitute an improvement in the HRS,




one of the options should be proposed, as modified after testing, as




a formal revision to the HRS in the National Contingency Plan.   Of




the options, Option 1 is preferred.  This option employs more




descriptors and should, therefore, provide greater discrimination




among sites.  Option 2 is simpler, consistent with the approach used




in the other pathways, and would be an adequate procedure for




evaluating potential to release.  However, the use of Option 2  would




discriminate against sites with multiple sources.  Hence, it would




understate the potential for such sites to release contaminants and




would thus understate their relative risks.  Regardless, if Option 2




were adopted, the adoption of the recommended changes to the waste




characteristic category and targets estimation procedures would be




indicated.
                                 Ill

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8.0  REFERENCES AND BIBLIOGRAPHY

8.1  Selected References on Emission Processes

Anderson, David C. and Stephen G. Jones, "Fate of Organic Liquids on
Soil," Proceedings of the National Conference and Exhibition on
Hazardous Waste and Environmental Emergencies, Held on March 12-14,
1984 in Houston, TX, Hazardous Materials Control Research Institute,
Silver Spring, MD, 1984, pp. 384-388.

Bennett, Gary F. "Fate of Solvents in a Landfill," Proceedings of
the National Conference on Hazardous Wastes and Environmental
Emergencies, Held on May 14-16, 1985 in Cincinnati, OH, Hazardous
Materials Control Research Institute, Silver Spring, MD, 1985,
pp. 199-210.

Brown, Kirk W., Gordon B. Evans, Jr., and Beth D. Frentrup,  eds.,
Hazardous Waste Land Treatment, Butterworth Publishers, Woburn, MA,
1983.

Cowherd, Chatten Jr. et al., Rapid Assessment of Exposure to
Particulate Emissions from Surface Contamination Sites, Midwest
Research Institute, Kansas City, MO, September 1984.

Hwang, Seong T., "Toxic Emissions from Land Disposal Facilities,"
Environmental Progress, Vol. 1, No. 1, February 1982, pp.  46-52.

James, S. C., R. N. Kinman, and D. L. Nutini, "Toxic and Flammable
Gases," Contaminated Land;  Reclamation and Treatment, Michael A.
Smith, ed., Plenum Press, New York, NY, 1985.

Kinman, Riley N. and David L. Nutini, "Production, Migration, and
Hazards Associated with Toxic and Flammable Gases at Uncontrolled
Hazardous Waste Sites," Land Disposal of Hazardous Waste:
Proceedings of the Tenth Annual Research Symposium, (EPA-600/
9-84-007), U.S. Environmental Protection Agency, Cincinnati,  OH,
August 1984, pp. 52-60.

Shen, Thomas T., "Air Quality Assessment for Land Disposal of
Industrial Wastes," Environmental Management, Vol. 6, No.  4,  1982,
pp. 297-305.

Shen, Thomas T., "Estimating Hazardous Air Emissions from Disposal
Sites," Pollution Engineering, Vol. 13, No. 8, August 1981,
pp. 31-371

Shen, Thomas T., "Estimation of Organic Compound Emissions from
Waste Lagoons," Journal of the Air Pollution Control Association,
Vol. 32, No. 1, January 1982, pp. 79-82.

                                 113

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Shen, Thomas T. and Granvllle H. Sewell, "Air Pollution Problema of
Uncontrolled Hazardous Waste Sites," Proceedings of the National
Conference on Management of Uncontrolled Hazardous Waste Sites, Held
on November 29-December 1, 1982 In Washington, DC, Hazardous
Materials Control Research Institute, Silver Spring, MD, 1982,
pp. 76-80.
Shen, Thomas T. and James Tofflemire, "Air Pollution Aspects of Land
Disposal of Toxic Waste," Journal of the Environmental Engineering
Division of ASCE, Vol. 106, No. EE1, February 1980, pp. 211-226.
Thibodeaux, Louis J., "Estimating The Air Emissions of Chemicals
from Hazardous Waste Landfills," Journal of Hazardous Materials,
Vol. 4, 1981, pp. 235-244.

8.2  Selected References Addressing Air Monitoring Guidance

Ford, P. J., P. J. Turlna, and D. E. Seeley, Characterization of
Hazardous Sites, A Methods Manual.   Volume 2.   Available Sampling
Methods, (EPA-600/4-83-040), U.S. Environmental Protection Agency.
Las Vegas, NV, September 1983.

Hanlsch, Robert C. and Maureen A. McDevitt, Protocols for Sampling
and Analysis of Surface Impoundments and Land  Treatment/Disposal
Sites for VOCs:  Technical Note, (DCN 84-222-078-11-12), Radian
Corporation, Austin, TX, September 28, 1984.

Plumb, R. H., Jr., Characterization of Hazardous Sites,  A Methods
Manual.  Volume 3.  Available Laboratory Analytical Methods,
(EPA-600/4-84-038), U.S. Environmental Protection Agency,  Las Vegas,
NV, May 1984.

Rlggin, R. M., Compendium of Methods for the Determination of Toxic
Organic Compounds in Ambient Air, (EPA-600/4-84-041), U.S.
Environmental Protection Agency, Research Triangle Park, NC,
April 1984.

U.S. Environmental Protection Agency, Field Standard Operating
Procedures for Air Surveillance F.S.O.F. 8, (Draft), U.S.
Environmental Protection Agency, Environmental Response  Team,
Washington, DC, 1985.

U.S. Environmental Protection Agency, Standard Operating Safety
Guides, U.S. Environmental Protection Agency,  Washington,  DC,
November 1984.
                                114

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U.S. Environmental Protection Agency, Technical Assistance for
Sampling and Analysis of Toxic Organic Compounds in Ambient Air,
CEPA-600/ 4-83-027), U.S. Environmental Protection Agency,  Research
Triangle Park, NC, 1983.

8.3  Principal References Used in Developing Containment Factors

Brown, D. et al., Techniques for Handling Landborne Spills of
Volatile Hazardous' Substances, (EPA-600/ 2-81-207), U.S.
Environmental Protection Agency, Cincinnati, OH, September 1981.

Brown, Kirk W. , Gordon B. Evans, Jr., and Beth D. Frentrup, eds.,
Hazardous Waste Land Treatment, Butterworth Publishers,  Woburn, MA,
Ehrenfeld, John R. and Joo Hooi Ong, Evaluation of Emission Controls
for Hazardous Waste Treatment,  Storage, and Disposal Facilities,
(EPA-450/ 3-84-017), U.S. Environmental Protection Agency,  Research
Triangle Park, NC, November 1984.

Ehrenfeld, John R. and Joo Hooi Ong, "Control of Emissions from
Hazardous Waste Treatment Facilities," (85-70.1),  Presented at the
78th Annual Meeting of the Air Pollution Control Association,  Held
on June 16-21, 1985 in Detroit, MI,  Air Pollution Control
Association, Pittsburgh, PA, 1985.

Farmer, Walter J. et al., Land Disposal of Hexachlorobenzene Waste -
Controlling Vapor Movement in Soil,  (EPA-600/2-80-119) ,  U.S.
Environmental Protection Agency, Cincinnati, OH, August  1980.

Genetelli, Emil J. and John Cirello, eds., Gas and Leachate from
Landfills;  Formation, Collection and Treatment, (EPA-600/ 9-76-004)
U.S. Environmental Protection Agency, Cincinnati,  OH, 1976.

James, S. C. , R. N. Kinman, and D.  L. Nutini, "Toxic and Flammable
Gases," Contaminated Land;  Reclamation and Treatment, Michael A.
Smith, ed., Plenum Press, New York,  NY, 1985.

Lutton, R. J., Evaluating Cover Systems for Solid and Hazardous
Wastes, (EPA-530/SW-867c), U.S. Environmental Protection Agency,
Washington, DC, September 1980.

Lutton, R. J., G. L. Regan, and L.  W. Jones, Design and  Construction
of Covers for Solid Waste Landfills, (EPA-600/ 2- 79-165), U.S.
Environmental Protection Agency, Cincinnati, OH, 1979.

Moore, Charles A., "Landfill Gas Generation, Migration and Controls,"
CRC Critical Reviews in Environmental Control, Vol. 9, No. 2,
November 1979, pp. 157-184.

                                 115

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Patry, G. D. R. and R. M. Bell, "Covering Systems," Contaminated
^aud;  Reclamation and Treatment, Michael A.  Smith, ed.,
Plenum Press, New York, NY, 1985.

Roabury, Keith D. and Stephen C.  James, "The Control of Fugitive
Dust Emissions at Hazardous Waste Cleanup Sites," Proceedings of the
Fifth National Conference on Management of Uncontrolled Hazardous
Waste Sites, Held on November 7-9, 1984 in Washington, DC, Hazardous
Materials Control Research Institute, Silver Spring, MD,  198A,
pp. 265-267.

Ihibodeaux, Louis J., Charles Springer, and Rebecca S. Parker,
"Design  for Control of Volatile Chemical Emissions from Surface
Impoundments," Hazardous Waste and Hazardous Materials, Vol.  2,
No. 1, 1985, pp. 99-106.

Vogel, Gregory A. and Denis F. 0'Sullivan, Air Emission Control
Practices at Hazardous Waste Management Facilities, (MTR-83W89),
The MITRE Corporation, McLean, VA7 June 1983.

Walsh, Gary, "Control of Volatile Air Emissions from Hazardous Waste
Land Disposal Facilities," Proceedings of the National Conference on
Hazardous Wastes and Environmental Emergencies, Held on May 12-14,
1984 in  Houston, TX, Hazardous Materials Control Research Institute,
Silver Spring, MD, 1984, pp. 146-153.

8.4  General Bibliography

Amoore,  John E. and Earl Hautala, "Odor as an Aid to Chemical Safety:
Odor Thresholds Compared with Threshold Limit Values and  Volatilities
for 214  Industrial Chemicals in Air and Water Dilution,"  Journal of
Applied  Toxicology, Vol. 3, No. 6, 1983, pp.  272-290.

Amster,  Michael B., Nasrat Hijazi, and Rosalind Chan, "Real Time
Monitoring of Low Level Air Contaminants from Hazardous Waste Sites,"
Proceedings of the National Conference on Management of Uncontrolled
Hazardous Waste Sites, Held on October 31-November 2, 1983 in
Washington, DC, Hazardous Materials Control Research Institute,
Silver Spring, MD, 1983, pp. 98-99.

Anderson, David C. and Stephen G. Jones, "Fate of Organic Liquids on
Soil," Proceedings of the National Conference and Exhibition  on
Hazardous Waste and Environmental Emergencies, Held on March  12-14,
1984 in Houston, TX, Hazardous Materials Control Research Institute,
Silver Spring, MD, 1984, pp. 384-388.

Arthur D. Little, Inc., Proposed Revisions to MITRE Model,
Arthur D. Little, Inc., Cambridge, MA, September 23, 1981.
                                 116

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Arthur D. Little, Inc., An Analysis of the Hazard Ranking System and
the National Priority List. (Reference No. 88922), Arthur D. Little,
Inc., Cambridge, MA, February 1983.

Astle, Alice D., Richard A. Duffee, and Alexander R. Stankuas,
Ph.D., "Estimating Vapor and Emission Rates from Hazardous Waste
Sites," Proceedings of the National Conference on Management of
Uncontrolled Hazardous Waste Sites, Held on November 29-December 1,
1982 in Washington, DC, Hazardous Materials Control Research
Institute, Silver Spring, MD, 1982, pp. 326-330.

Baker, Lynton W., An Evaluation of Screening Models for Assessing
Toxic Air Pollution Downwind of Hazardous Waste Landfills, Masters
Thesis, Office  of Graduate Studies and Research, San Jose State
University, San Jose, CA, May 1985.

Baker/TSA, Tyson's Dump Site, Montgomery County, PA, Draft Remedial
Investigation Report, Baker/ISA, Beaver, PA, August 1984.

Balfour, W. David and Charles E. Schmidt, Sampling Approaches for
Measuring Emission Rates from Hazardous Waste Disposal Facilities,
(EPA-600/D-84-140), U.S. Environmental Protection Agency, Cincinnati,
OH, May 1984.

Balfour, W. D., R. G. Wetherold, and D. L. Lewis, Evaluation of Air
Emissions from  Hazardous Waste Treatment, Storage, and Disposal
Facilities, (EPA-600/2-85-057), U.S. Environmental Protection
Agency, Cincinnati, OH, May 1985.

Balfour, W. D.  et al., "Field Verification of Air Emission Models
for Hazardous Waste Disposal Facilities," Land Disposal of Hazardous
Waste;  Proceedings of the Tenth Annual Research Symposium, (EPA-600/
9-84-007), U.S. Environmental Protection Agency, Cincinnati, OH,
August 1984, p. 197.

Battye, William et al., Preliminary Source Assessment for Hazardous
Waste Air Emissions from Treatment, Storage and Disposal Facilities
(TSDFs), (Draft Final Report), GCA Corporation, Bedford, MA,
February 1985.

Bell, R. M. and G. D. R. Parry, "The Upward Migration of Contaminants
Through Covering Systems," Proceedings of the Fifth National
Conference on Management oflJncontrolled Hazardous Waste Sites, Held
on November 7-9, 1984 in Washington, DC, Hazardous Materials Control
Research Institute, Silver Spring, MD, 1984, pp. 588-591.
                                 117

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Bennett, Gary F., "Fate of Solvents in a Landfill," Proceedings of
the National Conference on Hazardous Wastes and Environmental
Emergencies, Held on May 14-16, 1985 in Cincinnati, OH, Hazardous
Materials Control Research Institute, Silver Spring, MD, 1985,
pp. 199-210.

Bilsky, I. L., "Air Pollution Aspects of Hazardous Waste Disposal in
Texas," (85-79.3), Presented at the 78th Annual Meeting of the Air
Pollution Control Association, Held on June 16-21, 1985 in Detroit,
MI, Air Pollution Control Association, Pittsburgh, PA, 1985.

Bradstreet, Jeffrey W., Richard A. Duffee, and James J. Zoldak,
"Quantification of Odors from Waste Sites," (85-79.4), Presented at
the 78th Annual Meeting of the Air Pollution Control Association,
Held on June 16-21, 1985 in Detroit, MI, Air Pollution Control
Association, Pittsburgh, PA, 1985.

Breton, Marc et al., Assessment of Air Emissions from Hazardous
Waste Treatment, Storage, and Disposal Facilities (TSDFs) -
Preliminary National Emissions Estimates, (Draft Final Report),
(GCA-TR-83-70-G), GCA Corporation, Bedford, MA, August 1983.

Breton, Marc et al., Evaluation and Selection of Models for
Estimating Air Emissions from Hazardous Waste Treatment, Storage,
and Disposal Facilities, (FJPA-450/3-84-020), U.S. Environmental
Protection Agency, Research Triangle Park, NC, December 1984.

Brodzinsky, Richard and Hanwant B. Singh, Volatile Organic Chemicals
in the Atmosphere;  An Assessment of Available Data, (EPA-600/
3-83-027a), U.S. Environmental Protection Agency, Research Triangle
Park, April 1983.

Brown, D. et al., Techniques for Handling Landborne Spills of
Volatile Hazardous Substances, (EPA-bOO/2-81-207), U.S. Environmental
Protection Agency, Cincinnati, OH, September 1981.

Brown, Kirk W., Gordon B. Evans, Jr., and Beth D. Frentrup, eds.,
Hazardous Waste Land Treatment, Butterworth Publishers, Woburn, MA,
TSBT:

Brown, Richard D., Hazard Ranking System Issue Analysis;  Use of
Significance in Determining Observed Release, (MTR-86W101), The
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                                 130

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                                139

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                             APPENDIX A




       SUMMARY OF AIR MONITORING DATA AT SELECTED WASTES SITES






     This appendix presents a compilation  of available  data on the



ambient air contaminant concentrations arising from selected wastes




sites.  The data are limited in scope and  are presented to  indicate




the magnitude of the air contamination problems that might  arise




from wastes sites.
                                 141

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                             TABLE A-i

                PCB  CONCENTRATIONS AT SELECTED SITES


       Site                              Concentration  (ug/mr)

    Caputo                               0.05 - 3  (winter)
                                         246 - 300 (summer)

    Lehigh Elect                         0.0075

    New Bedford                          0.021 (winter)
                                         0.41 - 1.5 (summer)
Source:   Adapted from  Smith, Michael A., ed., Contaminated Land:
         Reclamation and Treatment, Plenum Press, New York, NY,
         1985,  pp.  407-417.
                                142

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                              TABLE A-2

        AMBIENT AIR CONCENTRATIONS OF SELECTED COMPOUNDS AT
        THREE  CALIFORNIA HAZARDOUS WASTES DISPOSAL FACILITIES
                            (ppb Carbon)
                      BKK
                    Kettleman Hills
IT-Martinez
Compound
Upwind  Downwind   Upwind  Downwind   Upwind  Downwind
n-Hexane
Benzene
n-Heptane
Toluene
n-Octane
Ethyl Benzene
Xylenes
Dichloro-
benzene
Total
12
10
8
52
5
10
46

0
143
139
115
86
952
158
37
157

0
1644
11
13
6
25
3
3
15

0
76
75
106
185
123
84
64
239

0
876
10
8
7
22
2
3
11

3
66
12
16
15
30
3
9
19

2
106
Note:  Monitoring conducted by Illinois Institute of Technology for
       EPA during November and December 1979.

Source:  Scheible et al., 1982.
                                 143

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                              TABLE  A-3

        AMBIENT AIR  CONCENTRATIONS  OF SELECTED COMPOUNDS  AT
       THREE  CALIFORNIA  HAZARDOUS WASTES  DISPOSAL FACILITIES
                            (ppb Carbon)
                      BKK
                    Kettleman Hills
                               IT-Martinez
Compound

Ethane
Ethene
Propane
Acetylene
1-Butane
n-Butane
Propene
Propadiene
i-Pentane
n-Pentane
1-Butene
i-Butene

Total
Upwind  Downwind   Upwind  Downwind   Upwind  Downwind
  15
  29
  19
  35
  23
  50
  10

  53
  31
   4
  11

 280
  76
 100
 370
  48
 730
 440
  49
   4
 800
 650
  35
  48

3350
 28
 18
 29
 18
 11
 26
  5

 30
 19
  8
192
 27
 15
 27
 14
 11
 67
  4

170
140
  2
 11

488
 28
 23
 88
 20
 80
 93
 11

110
 56
  7
 16

532
 15
 18
 13
 14
 86
 21
  5

 23
 14
209
Note:  Monitoring conducted by State of California Air Resources
       Board during November and December 1979.

Source:  Scheible et al., 1982.
                                144

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                              TABLE A-4

           POTENTIALLY CARCINOGENIC,  TOXIC,  MUTAGENIC,  OR
           TERATOGENIC COMPOUNDS MEASURED AT THE BKK SITE
                  (Maximum Detected Concentrations)
                Compound
          Benzene
          Vinyl Chloride
          Chloroform
          Carbon Tetrachloride
          Dioxane
          Tetrachlorethane
          Tetrachloroethylene
          Methyl Chloroform
          Trichloroethylene                       36.0
Note:  Monitoring conducted by University of Southern California
       during November 1979-June 1980; January 1981;  and February
       1981.  Facility was in operation at this time.

Source:  State of California Air Resources Board, An Assessment of
         the Volatile and Toxic Organic Emissions from Hazardous
         Waste Disposal in California, Background Material for a
         Public Meeting, February 24, 1982,  State of  California Air
         Resources Board, Sacramento, CA, February 1982, p. 31.
                                 145

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                                TABLE A-5

           AVERAGE CONCENTRATIONS  OF CONTAMINANTS DETECTED AT
                   SELECTED  NEW JERSEY DISPOSAL SITES
                               (ppb volume)
Compound
Vinylidene Chloride
Methylene Chloride
Chloropyrene
Chloroform
1-2 Dichloroethane
1-1-1 Trichl or oe thane
Benzene
Carbon Tetrachloride
I richlor oe thylene
Dioxane
1-1-2 Trichloroe thane
Toluene
1-2 Dibromoethane
Tetrachloroe thylene
Chlorobenzene
Ethylbenzene
m&p Xylene
Styrene
o-Xyiene
1-1-2-2 Tetra-
chloroe thane
o-Chlorotoluene
p-Chlorotoluene
p-Dichlorobenzene
o-Di chlorobenzene
Nitrobenzene
Naphthalene
Site A
0
0.09
0
0.33
0.01
0.38
4.98
0.06
0.39
0
0.02
42.09
0.25
0.92
0.53
3.56
9.95
0.62
3.09
0.24

0.4
0.71
0.24
0.35
1.38
0.88
Site B
0.39
0.49
0
0.64
0
0.51
2.55
0.12
0.36
0
0.02
11.52
0.25
1.03
0.09
0.78
2.18
0.27
0.93
0.05

0.06
0.06
0.1
0.11
0.23
0.2
Site C
36.44
11.34
0.01
0.91
0.28
3.04
7.66
0.1
2.86
0.01
1.26
51.91
0.36
2.03
0.78
3.91
7.72
1.3
2.27
0.59

0.43
0.39
0.51
0.77
0.48
0.27
Site D
3.46
0.9
0
0.21
0.03
0.84
1.33
0.04
0.21
0
0.32
15.16
0.06
0.38
0.32
0.61
1.52
0.11
0.42
0.02

0.05
0.07
0.08
0.11
0.12
0.11
Site E
1.6
1.14
0
0.08
0
0.57
0.6
0.03
0.08
0
0.29
3.28
0.05
0.12
0.09
0.13
0.37
0.13
0.15
0.01

0.02
0.04
0.04
0.06
0.01
0.1
Landfill
2.61
1.58
0
0.12
0
1.29
3.33
0.02
0.34
0
0.11
27.79
0.02
1.53
0.15
1.53
3.35
0.41
0.9
0.01

0.01
0.03
0.06
0.06
0
0.08
Note:  Detection limit of 0.01 substituted  for values below detection limit.

Source: Adapted from LaRegina,  J.  E.  et al., 1984.
                                    146

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                             APPENDIX B




                   DISCUSSION OF REJECTED OPTIONS






     This appendix presents discussions of the scoring options that




were developed and rejected.  A short description of each option is




presented, followed by the reasons for its rejection.




B.I  Evaluating Ambient Monitoring Data for Observed Releases




     Two basic options for evaluating ambient monitoring data for




observed release were developed.  These options would employ ambient




measurements that might not "significantly" exceed background or may




be surrogates for ambient air measurements in assigning an observed




release value.  This option would maintain the current approach:




existence of data showing concentrations significantly above




background results in a maximum value, 45.  Other monitoring results




would be evaluated as in Table B-l.  The following relationship




would hold between the values




                         0 < A < B < C < 45




Thus, a zero value would be assigned if and only if a comprehensive




monitoring program showed no detectable levels of contamination.




     An alternate, similar option developed would allow data other




than ambient air data to be used.  For example, evidence of surface




soil contamination, relative to background levels, could be utilized




in a process similar to that for ambient air data suggested above.




A minimum acceptable area of contamination would have to be set as




well.




                                 147

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                              TABLE fl-1

                    EVALUATING MONITORING RESULTS


Monitoring Result                                               Value

No Contaminants Detected

  •  Comprehensive monitoring program*                            0

  •  Limited monitoring program*                                  A

Contaminants Detected

  •  Background above analytical** detection limit                B
     - Contamination level below analytical detection limit
     - Contamination level above analytical detection limit       C
       but not significantly above background
     - Contamination level significantly above background        45

  •  Background below analytical detection limit                  C
     - Contamination level below analytical detection limit
     - Contamination level above analytical detection limit      45
 *Guidance would be provided as to the definition of comprehensive
   and limited monitoring programs.
 **The analytical detection limit reflects the combination of
   instrument and laboratory detection limits.  These differ for
   different instruments and laboratory methods.
                                 148

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     Further minor variations might be developed using alternate




values and data categories such as vegetation injury.




     The above options were rejected since in the interest of




maintaining simplicity in the observed release category and as




placing too much emphasis on data of questionable quality and




meaning.  The basic concept led to the development of the also



rejected "inconclusive monitoring" emission source descriptors (see




Section B.2.2) and the adopted exceptions in the mobility factor




(see Section 3.3.2).




B.2  Potential to Release Options




     B.2.1  Emissions Estimation Approach




     The principal alternative to the engineering factors approach




adopted in the two options discussed previously is the emissions




estimation approach.  In this approach, emissions equations would be




used to estimate the emissions from a site and a value assigned




based on the magnitude of the emissions estimate.  Several emissions




equations are available for generic waste disposal and treatment




processes.  Breton, et al. (1984) and Balfour, Wetherold and Lewis




(1985) present fairly comprehensive discussions and evaluations of




the emissions models currently available.  Durham (1985) presents a




discussion of ongoing EPA efforts to improve these models.  Some of




the models have been verified in field studies with good success




(Balfour, W. D., et al., 1984, Caravanos, Sewell, and Shen, 1985).




Many of these models have also been employed by EPA in policy






                                 149

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studies (Breton, et al.,  1983;  Battye, et al., 1985).   A review of




this and related literature indicates that an emissions estimation




approach would probably be feasible.  The approach, however, was




rejected for several reasons.




     First, many of tne equations are complex and require a fairly




high level of sophistication to employ them properly.   It was




believed that the requisite high level of expertise would not be




readily available in the field.  Further; the equations require data




that are not generally available.  Some of the data are available in




standard references, for standard conditions. The principal data of




this type are the mass transfer coefficients, which are available




for only a limited number of chemicals in idealized environments.




It  is  possible to incorporate methods to calculate tnese factors




from readily available data (e.g., vapor pressure) in many cases.




However, these methods further complicate the calculations, do not




always account for important, difficult to evaluate site



characteristics, and generally lower the confidence in the final




result.  Of particular importance in this context is the effect of




waste mingling on equation parameter values.  Additional data that




are necessary in many of the equations include site-specific data on




detailed soil characteristics and meteorological factors.




     Second, the equations are not available addressing many of the




situations encountered in CERCLA sites.  Of particular importance




are sites containing broken drums or tanks, either exposed or






                                 150

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buried.  Equations applicable to this common circumstance are not




currently available.  Further, the equations are idealized and do




not reflect the deviations from design that are encountered in




uncontrolled sites.




     Finally, many of the emissions estimation approaches require




air monitoring data to back-calculate emissions rates.   If such data




were available, then the potential to release option would not have




to be employed at all.




     In summary, the emissions estimation approach is probably




technically feasible, but would be very difficult to implement.




     B.2.2  Inconclusive Monitoring Descriptors




     During the course of refining Options 1 and 2, five emission




source descriptors were developed for monitoring results that did




not indicate an observed release.  The idea behind these




"inconclusive monitoring" descriptors was to make use of monitoring




results that, even though they did not indicate an observed release,




would affect a subjective judgment of the probability that the site




was or would soon release a significant amount of contaminants.




These descriptors are listed in Table B-2.




     After much discussion, these five descriptors were deleted for




two reasons.  First, it was believed that if the air data collected




at the site do not indicate an observed release, then they are also




not of sufficient quality to use as emission source descriptors.




Second, the information contained in these data would be better used






                                 151

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                                TABLE B-2

         "INCONCLUSIVE MONITORING" EMISSION SOURCE DESCRIPTORS


Code                           Descriptor

         Ambient air monitoring results:

         Background at or above analytical detection limit:
30       - Contamination level below analytical detection limit
31       - Contamination level at or above analytical detection limit but
           not significantly above background
32       - Contamination level significantly above background but of
           insufficient quality to constitute an observed release

         Background below analytical detection limit:
33       - Contamination level below analytical detection limit
34       - Contamination level significantly above background but of
           Insufficient quality to constitute an observed release
                                152

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in assessing contaminant mobility and, hence, the exceptions to the




contaminant mobility factor discussed in Section 3.3.




     B.2.3  Site Age




     A review of the processes that lead to air releases indicates




that the dominant factors in determining release potential are the




nature (e.g., mobility) and quantity of the waste in the site and




the site containment.  Since the processes that determine emission



levels are continuous, the duration of time these processes have




been in operation determines the quantity of waste remaining on the




site and to a lesser extent, the nature of the waste.  Thus, the




time between disposal and site investigation, or the site age, is a




crucial factor in determining emission potential that is not




addressed in Options 1 and 2.  There are two reasons for this




apparent omission.  First, no viable measure of the time between




investigation and disposal could be defined.  It is generally not




possible to determine the date at which wastes were deposited at a




site.  Further, wastes were often deposited at different times and




in different amounts and mixtures over a long period of time.




Surrogate measures, such as years since site opening and years since




site closing, suffer from similar information collection problems




and may differ significantly from the actual years since disposal.




Second, the interaction between site age and contaminant mobility is




very complex and could not be simplified enough to allow both to be




incorporated in the options.






                                 153

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     B.2.4  Mobility Factors




     Two alternate approaches to the Versar approach for  evaluating




contaminant mobility were investigated:   partition coefficients and




fugacity.  Partition coefficients (Leo,  Hansch and Elkins,  1971;




Chiou, Schmedding, and Manes, 1982;  Mingelgrin and Gerstl,  1983;




Miller, et al., 1985) reflect the propensity of a compound  to




distribute between two other compounds or solution phases.   For



example, the octanol-water partition coefficient of a compound




reflects the propensity of that compound to distribute between




octanol and water within a combined solution.   The octanol-water




partition coefficient has been suggested as a  measure of




bioaccumulation (Saari and Goldfarb, 1986).  They are also




potentially useful in managing waste disposal, as an indication of




the mobility of contaminants in various  solutions (Prasad and Whang,




1985).




     The fugacity of a compound is somewhat similar to a  partition




coefficient (Mackay, 1979; Mackay and Paterson, 1981, 1982, and




1984).  However, fugacity reflects the long-term propensity of a




compound to distribute among environmental media rather than between




two solutes such as octanol and water, for example.  The  media of




concern, for example, can include air, water,  sediment, aquatic




biota, and soil.  Fugacity can be used to calculate the long-term




equilibrium distribution of a chemical in the environment.
                                 154

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     The use of partition coefficients were rejected for several




reasons.  In both Options 1 and 2, contaminant mobility reflects the




ability of a contaminant to move offsite due to the contaminant




physiochemical characteristics.  Partition coefficients measure the




propensity of the contaminant to distribute among solutions.  They




do not reflect the propensity of a contaminant to volatilize, only




the possibility to migrate to the air-surface interface.  These




coefficients are applicable to mobility only to the extent that the




distribution between solutions indicate ability to migrate.  This,




in turn, depends on the migration potential of the solute, which is




generally unknown.  Further, the partition coefficient depends on




the contaminant in question and the two solutes.  The same compound




may have very different octanol-water and organic carbon partition




coefficients.  The choice of the best applicable coefficient at a




site depends on the actual site waste composition, information that




is generally unavailable.  Finally, only octanol-water partition




coefficients are available for the contaminants generally




encountered at wastes sites.




     The use of fugacity was rejected primarily because of a lack of




available fugacity data for the contaminants of interest and the




complexity of the fugacity calculation approaches.  It was felt that




these calculations were too complex to be employed in the field.




Less important reasons include the concern that fugacity reflects




long-term equilibrium behavior rather that short-term transport






                                 155

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phenomena.  Fugacity would be a misleading measure of mobility

whenever the long-term distribution of a chemical differed

significantly from its short-term local distribution.

     B.2.5  Alternate Methods for Combining Containment Values

     Several alternate methods for combining containment values were

considered.  The first option developed employs a single containment

factor approach, combining the particulate matter and gas containment

aspects of a site.  The containment descriptors and values are

listed in Table B-3.  This approach was rejected as being inferior

to the two-factor approach presented in Options 1 and 2, while not

really representing a significant simplification (see the matrix

approaches in Table B-3).

     Additional options for combining the two containment values are

as follows:

     •  Three-level containment scale (0-2) for gases and particulate
        matter, combined value is the sum of the two values with a
        maximum value of 3.

     •  Four-level containment scale (0-3) for gases and particulate
        matter, combined value is the maximum of the two values.

     •  Four-level containment scale (0-3) for gases and particulate
        matter, combined value is the sum of the two values with a
        maximum value of 3.

     •  Three-level containment scale (0-2), the combined value is
        the maximum of the two values unless both are equal to two,
        in which case the combined value is J.

The adopted approach, which reflects the viewpoint that emissions

are determined by the least restrictive containment, was deemed

superior  to these alternatives.

                                 156

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                              TABLE B-3

                 SINGLE CONTAINMENT FACTOR APPROACH
ACTIVE FIRE SITE                                               	3_

BURIED TANKS

  •  Depth to tanks at least six inches; soil resistant        	1_
     to gas migration

  •  Depth to tanks at least six inches; soil not                2_
     resistant to gas migration

  •  Other                                                     	0_

CONTAMINATED SURFACE SOIL

                       See Matrix Procedure 1

EXPOSED DRUMS

  Drums intact                                                 	1
  Drums broken                                                   3

EXPOSED TANKS

  •  Open Roof Tanks
     - Dome intact; seals intact                               	0_
     - Dome intact; seals broken; waste covered with           	1_
       a stable immiscible fluid
     - Dome intact; seals broken; waste covered with           	1_
       floating spheres
     - Undomed or dome not intact; waste covered with          	2_
       a stable immiscible fluid
     - Undomed or dome not intact; waste covered with          	2_
       floating spheres
     - Other                                                   	0_

  •  Fixed and Floating Roofs
     - Structurally intact; seals intact
       — Conservation vents intact and functioning            	0_
          — Conservation vents intact but not functioning       1
                                 157

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                       TABLE B-3  (Continued)


EXPOSED TANKS (Concluded)

     - Structurally intact; seals intact (Concluded)
       — Waste covered with a stable inert gas
       — Waste covered with floating spheres
       — Insulated
       — Waste covered with a stable immiscible fluid
       — Other
     - Structurally intact; seals broken
       — Conservation vents intact and functioning
       — Conservation vents intact but not functioning
       — Waste covered with a stable inert gas
       — Waste covered with floating spheres
       — Insulated
       — Waste covered with a stable immiscible fluid         	2
       — Other                                                  ?
     - Structurally not intact
       — Conservation vents intact and functioning            	0
       — Conservation vents intact but not functioning        	1
       — Waste covered with a stable inert gas                	1
       — Waste covered with floating spheres                  	1
       — Insulated                                            	2
       — Waste covered with a stable immiscible fluid
       — Other
     - Other

 INACTIVE ABOVEGROUND FI&E SITE

                       See Matrix Procedure 2

 LANDFARM/LANPTREATMENT

                       See Matrix Procedure 3

 LANDFILL

                       See Matrix Procedure 4

 OPEN PIT

 SPILL SITE

                       See Matrix Procedure 5
                                 158

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                        TABLE B-3  (Continued)


SURFACE IMPOUNDMENTS

  •  Enclosed Impoundment*
     - Synthetic cover intact
     - Impoundment covered with floating spheres
     - Stable surfactant layer covering impoundment
       Synthetic cover torn                                   	2_
       Unstable or incomplete surfactant layer                	2
       Other                                                     D~
  •  Open impoundment (not enclosed)
     - Impoundment covered with floating spheres
     - Stable surfactant layer covering impoundment
     - Synthetic cover intact
     - Synthetic cover torn
     - Other

SURFACE WATER BODY OR OUTFALL

UNDERGROUND INJECTION

  •  Depth of injection at least x inches

  •  Depth of injection less than x inches

WASTE PILE

                       See Matrix Procedure b
*An enclosed impoundment is one with a freeboard exceeding two feet
 in height or one that is substantially surrounded by a wall,  fence,
 trees or other adequate windbreak.
                                 159

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                        TABLE  B-3  (Continued)

                         MATRIX PROCEDURE 1
                     CONTAMINATED SURFACE  SOIL
Evaluate the site separately for the following containment factors:

  Particulate Containment (choose applicable characteristic with
  lowest value):

  •  Site covered with an essentially impermeable cover        	0_
     or heavily vegetated.   No exposed soil or liquids
     (e.g., paved-over)

  •  Enclosed in an intact building                            	1_

  •  Site substantially vegetated or covered with a            	1_
     nonwater based dust suppressing fluid.  Little
     exposed soil or liquids

  •  Enclosed in an nonintact building                         	2_

  •  Site lightly vegetated or lightly covered with a          	2_
     nonwater dust suppressing fluid.  Much exposed soil
     or liquids

  •  Slope average less than 10 degrees                          2_

  •  Substantially surrounded with mesh fence                    2
  •  Site substantially devoid of vegetation.   Large             3
     percentage of exposed soil or liquids

  •  Other                                                       0

  Gas Containment:

  •  Enclosed in an intact building                              1

  •  Covered with an intact synthetic cover                      1

  •  Covered with a nonintact synthetic cover                     2

  •  Enclosed in a nonintact building                            2

  •  Other                                                       0


                                 160

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                       TABLE B-3 (Continued)






Combine the two containment values  as follows:




                                    Level of Gas  Containment

Level of
Particulate
Containment


0:
1:
2:
3:
0
0
1
2
3
1
1
1
2
3
2
2
2
2
3
,3
3
3
3
3
                                161

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                        TABLE B-3  (Continued)

                         MATRIX PROCEDURE 2
                   INACTIVE ABOVEGROUND FIRE SITE
Evaluate the site separately for the following containment factors:

  Particulate Containment (choose applicable characteristic with
  lowest value):

  •  Site covered with an essentially impermeable cover        	0_
     or heavily vegetated.  No exposed soil or liquids
     (e.g., paved-over)

  •  Enclosed in an intact building                              1
  •  Site substantially vegetated or covered with a            	1_
     nonwater-based dust suppressing fluid.  Little
     exposed soil or liquids

  •  Enclosed in a nonintact building                          	2_

  •  Site lightly vegetated or lightly covered with a          	2_
     a nonwater dust-suppressing fluid.  Much exposed
     soil or liquids

  •  Slope average less than 10 degrees                          2

  •  Substantially surrounded with mesh fence                    2
  •  Site substantially devoid of vegetation.   Large             3
     percentage of exposed soil or liquids

  •  Other                                                       0

  Gas Containment:

  •  Enclosed in an intact building                              1

  •  Enclosed in a nonintact building                            2

  •  Other                                                       0
                                162

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                       TABLE B-3 (Continued)






Combine the two containment values  as follows:




                                    Level of Gas Containment




                                    0       1       2      3




              Level of       0:      0       1       23




              Particulate    1:1       1       2      3




              Containment    2:      2       2       2      3




                             3:      3       3       33
                                163

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                        TABLE  B-3 (Continued)

                         MATRIX PROCEDURE 3
                       LANDFARM/LANDTREATMENT
Evaluate the site separately for the following containment factors:

  Particulate Containment (choose applicable characteristic with
  lowest value):

  •  Site covered with an essentially impermeable cover        	0_
     or heavily vegetated.  No exposed soU or liquids
     (e.g., paved-over)

  •  Site substantially vegetated or covered with a            	1_
     nonwater—based dust-suppressing fluid.   Little
     exposed soil or liquids

  •  Site lightly vegetated or lightly covered with a          	2_
     nonwater dust-suppressing fluid.   Much exposed soil
     or liquids

  •  Slope average less than 10 degrees                        	2_

  •  Substantially surrounded with mesh fence                    2

  •  Site substantially devoid of vegetation.  Large
     percentage of exposed soil or liquids                       3
  •  Other                                                       0

  Gas Containment:

  •  Synthetic cover with soil cover over 0.4 inches             0

  •  Soil  cover in  excess of  one  inch;  soil  resistant            1
     to gas migration

  •  Soil  cover in  excess of  one  inch;  soil  not resistant        2
     to gas migration

  •  Other                                                       0
                                164

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                       TABLE B-3 (Continued)
Combine the two containment values as follows:
                                     9
                                    Level of Gas Containment

Level of
Particulate
Containment


0:
1:
2:
3:
0
0
1
2
3
1
1
1
2
3
2
2
2
2
3
3
3
3
3
3
                                165

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                        TABLE B-3  (Continued)

                         MATRIX PROCEDURE 4
                              LANDFILL
Evaluate the site separately for the following containment factors:

  Particulate Containment (choose applicable characteristic with
  lowest value):

  •  Site covered with an essentially impermeable cover          0
     or heavily vegetated.   No exposed soil or liquids
     (e.g., paved-over)

  •  Site substantially vegetated or covered with a
     nonwater based-dust-suppressing fluid.   Little
     exposed soil or liquids                                     1

  •  Site lightly vegetated or lightly covered with a            2
     nonwater dust-suppressing fluid.  Much exposed soil
     or liquids

  •  Slope average less than 10 degrees                          2

  •  Substantially surrounded with mesh fence                    2

  •  Site substantially devoid of vegetation.  Large             3
     percentage of exposed soil or liquids

  •  Other                                                       0

  Gas Containment:

  •  Functioning gas collection system                           0

  •  Depth to waste at least six inches;  soil cover              1
     resistant to gas migration

  •  Depth to waste at least six inches;  soil cover not          1
     resistant to gas migration                                ——

  •  Nonfunctioning gas collection system                        3

  •  Other                                                       0
                                166

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                       TABLE B-3 (Continued)






Combine the two containment values  as follows:




                                    Level of Gas Containment



                                    0123



              Level of       0:      0       1       23



              Particulate    1:1       1       2      3



              Containment    2:      2       2       2      3



                             3:      3       3       33
                                167

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                        TABLE B-3  (Continued)

                         MATRIX PROCEDURE 5
                             SPILL SITE
Evaluate the site separately for the following containment factors:

  Particulate Containment (choose applicable characteristic with
  lowest value):

  •  Site covered with an essentially impermeable cover        	0_
     or heavily vegetated.   No exposed soil or liquids
     (e.g., paved-over)

  •  Enclosed in an intact building                            	1_
  •  Site substantially vegetated or covered with a            	1_
     nonwater-based-dust suppressing fluid.   Little
     exposed soil or liquids

  •  Enclosed in an nonlntact building                         	2_

  •  Site lightly vegetated or lightly covered with a          	2_
     nonwater-dust-suppressing fluid.   Much  exposed soil
     or liquids

  •  Slope average less than 10 degrees                          2

  •  Substantially surrounded with mesh fence                    2
  •  Site substantially devoid of vegetation.   Large           	3_
     percentage of exposed soil or liquids

  •  Other                                                     	0_

  Gas Containment:

  •  Synthetic cover with soil cover over 0.4  inches             0

  •  Covered with  an intact synthetic cover; surface             1
     contamination

  •  Soil cover in excess of one inch                            1

  •  Covered with  a nonlntact synthetic  cover;  surface            2
     contamination

  •  Other                                                       0
                                168

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                       TABLE B-3 (Continued)


Combine the two containment values  as follows:

                                    Level of Gas Containment

                                    0123
              Level of       0:      0       1      23

              Particulate    1:1       1      2      3

              Containment    2:      2       2      2      3

                             3:      3       3      33
                                169

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                        TABLE  B-3  (Continued)

                         MATRIX PROCEDURE 6
                             WASTE PILE
Evaluate the site separately for the following containment factors:

  Particulate Containment (choose applicable characteristic with
  lowest value):

  •  Site covered with an essentially impermeable cover        	0_
     or heavily vegetated.   No exposed soil or liquids
     (e.g., paved-over)

  •  Enclosed in an intact building                            	1_

  •  Site substantially vegetated or covered with a            	1_
     nonwater-based-dust-suppressing fluid.  Little
     exposed soil or liquids

  •  Enclosed in an nonlntact building                         	2_

  •  Slope average less than 10 degrees                        	2_

  •  Substantially surrounded with mesh fence                  	2_

  •  Site lightly vegetated or lightly covered with a          	3
     nonwater-dust-suppressing fluid.  Much exposed soil
     or liquids

  •  Site substantially devoid of vegetation.  Large           	3_
     percentage of exposed soil or liquids

  •  Other                                                     	0_

  Gas Containment:           ,

  •  Covered with an intact synthetic cover                      1

  •  Covered with a nonintact synthetic cover                    2

  •  Enclosed in an intact building                              2

  •  Other                                                       0
                                 170

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                       TABLE B-3 (Concluded)






Combine the two containment values  as follows:




                                    Level of Gas Containment

Level of
Particulate
Containment


0:
1:
2:
3:
0
0
1
2
3
1
1
1
2
3
2
2
2
2
3
3
3
3
3
3
                                 171

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     B.2.6  Alternate Release Potential Algorithms

     Options 1 and 1A use an algorithm to evaluate a site's release

potential that combines values based on three emission source

descriptors using probabilistic combinatorics.  In Option 2, the

single emission source descriptor that best describes the entire

site is chosen and the site evaluated accordingly, considering size,

mobility, and containment.   Numerous alternate algorithms were

considered as follows:

     •  Assign a minimum nonzero value (e.g., 5)  to each site
        lacking an observed release.

     •  Choose the emission source descriptor with the highest
        overall value considering descriptor values, size, mobility
        and containment.

     •  Choose all the applicable emission source descriptors and
        sum the resulting values, considering size, mobility and
        containment, using the minimum of this sum and 45 as the
        site value.

     •  Choose all the applicable emission source descriptors and
        sum the resulting values, considering size, mobility and
        containment, truncating the sum of the size dependent
        emission source descriptor and mobility values to 15 before
        multiplying by the containment value.  The minimum of this
        sum and 45 would be the site value.

These options were rejected in favor of the probabilistic

combinatorics since the latter approach better reflects the

probabilistic nature of the potential-to-release  option.  A

potentially viable alternative, however, may be to use two rather

than three emission source descriptors.
                                172

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B.3  Targets Category Options




     These options envision alterations in the target distance limit




used in the HRS, currently four miles.   As stated previously, the




actual target distance limit is yet to be chosen for Options 1 and 2,




pending completion of a special analysis.  The options are listed in




Tables B-4 through B-ll.  Further options can be defined employing a




minimum value of 3 (for example).




B.4  Alternate Air Pathways




     A total of six complete air pathway options were developed and




presented to EPA for consideration.  Four of these options were



rejected in favor of the two options presented in Section 3.  The




remaining options are simplifications of the first two.   Successive




simplifications were made in the release category addressing




emission source descriptors, containment factors, and mobility




factors.  The waste characteristics and targets categories were




unchanged from Option 1.  These four options are summarized in




Table B-12.
                                 173

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                 TABLE  fl-4

ALTERNATE POPULATION-AT-RISK FACTOR MATRIX
               (Variation 1)
                        Distance (miles)
Population 0-50 0-15 0-4 0-1



1,

1
101
001
3,001







1,
3,

10


Popi

1
101
001
001
10,
0 6666
- 100 6 9 12 15
- 1,000 9 12 15 18
- 3,000 12 15 18 21
- 10,000 15 18 21 24
,000+ 18 21 24 27
TABLE B-5
ALTERNATE POPULATION-AT-RISK FACTOR MATRIX
(Variation 2)
Distance (miles)
ilation 0-15 0-4 0-1 0-1/2
0 6666
- 100 9 12 15 18
- 1,000 12 15 18 21
- 3,000 15 18 21 24
- 10,000 18 21 24 27
000+ 21 24 27 30
0-1/2
6
18
21
24
27
30








                   174

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                 TABLE B-6

ALTERNATE POPULATION-AT-RISK FACTOR MATRIX
               (Variation 3)
                       Distance (miles)
Population

1
101
1,001
3,001
10
0
- 100
- 1,000
- 3,000
- 10,000
,000+
0-15
6
6
9
12
15
18
0-4
6
9
12
15
18
21
0-1
6
12
15
18
21
24
0-1/2
6
15
18
21
24
27
0-1/4
6
18
21
24
27
30
                    175

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                                TABLE 3-7

                      ALTERNATE VALUES FOR LAND USE
                              (Variation 1)
ASSIGNED VALUE -

Distance (miles) to
  Commercial/Industrial

Distance (miles) to Nat./
  State Parks, Forests
  Wildlife Preserves
  and Residential Areas

Distance (miles) to
  Agricultural Lands:
    Ag Land
    Prime Ag Land

Distance to Historic/
  Landmark Sites
 0

5+


10+
5+
10+
1-5     1/2-1
5-10    2-5
1-5
5-10
1/2 - 1
2-5
               0 - 1/2
               0-2
0 - 1/2
0-2
3, if within view of site or if site is
  subject to significant impacts.
                                176

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                                TABLE B-8

                      ALTERNATE VALUES FOR LAND USE
                              (Variation 2)
ASSIGNED VALUE -

Distance (miles) to
  Commercial/Industrial

Distance (miles) to Nat./
  State Parks, Forests
  Wildlife Preserves
.  and Residential Areas

Distance (miles) to
  Agricultural Lands:
    Ag Land
    Prime Ag Land

Distance to Historic/
  Landmark Sites
 0

5+


15+
5+
15+
1-5     1/2-1
10-15   5-10
               0 - 1/2
               0-5
1-5
10 - 15
1/2 - 1
5-10
0 - 1/2
0-5
3, if within view of site or if site is
  subject to significant impacts.
                                 177

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                                TABLE B-9

               ALTERNATE VALUES FOR SENSITIVE ENVIRONMENT
                              (Variation 1)
ASSIGNED VALUE -
STANCE (MILES) TO
TLANDS
Coastal
Fresh Water
STANCE (MILES) TO

5+
2+
2+

2 -
1/2 -
1 -

5
2
2

1 -
1/4 -
1/2 -

2
1/2
1

0 -
0 -
0 -

1
1/4
1/2
CRITICAL HABITAT
                               TABLE B-10

               ALTERNATE VALUES FOR SENSITIVE ENVIRONMENT
                              (Variation 2)
ASSIGNED VALUE -
STANCE (MILES) TO
TLANDS
Coastal
Fresh Water
STANCE (MILES) TO

1+
1/4+
1/2+

1/2 - 1
100 ft - 1/4
1/4 - 1/2

0 -
0 -
0 -

1/2
100 ft
1/4
CRITICAL HABITAT
                                178

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                               TABLE B-ll

               ALTERNATE VALUES FOR SENSITIVE ENVIRONMENT
                              (Variation 3)
ASSIGNED VALUE -         1                2                    3

DISTANCE (MILES) TO
WETLANDS

  Coastal                2+            1-2               0-1

  Fresh Water           1/2+           1/4 - 1/2           0 - 1/4

DISTANCE (MILES) TO      1+            1/2-1             0 - 1/2
CRITICAL HABITAT
                                 179

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                                                    TABLE B-12

                        OVERVIEW OF IMPORTANT FEATURES OF REJECTED AIR PATHWAY OPTIONS
    Release
    Category
00
o
    Waste
    Characteristics
    Targets
      Option 3

Seven-level observed
  release
5 descriptors
Size not included
Mobility* factor
  (3 measures)
  (5 contaminants)
Simplified gas
  containment
Probabilistic
  combinatorics

Combined toxicity-
  mobility factor
Waste quantity

Population
Sensitive environment
Land use
Based on a to-be-
  determined distance
  limit
     Option A

Five-level observed
  release
5 descriptors
Size not included
Mobility* factor
  (3 measures)
  (5 contaminants)
Simplified gas
  containment
Probabilistic
  combinatorics

Combined tozicity-
  mobility factor
Waste quantity

Population
Sensitive environment
Land use
Based on a to-be-
  determined distance
  limit
     Option 5

Five-level observed
  release
5 descriptors
Size not included
Mobility factor not
  included
Simplified gas
  containment
Probabilistic
  combinatorics
Combined toxicity-
  mobility factor
Waste quantity

Population
Sensitive environment
Land use
Based on a to-be-
  determined distance
  limit
     Option 6

Five-level observed
  release with a
  nonzero minimum
  value for potential
  to release
Combined toxicity-
  mobllity factor
Waste quantity

Population
Sensitive environment
Land use
Based on a to-be-
  determined distance
  limit
    •Applicable to gases only.
     under investigation.
           Particulates are assumed to be mobile.   Particulate mobility is currently

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                             APPENDIX C

               STEP-BY-STEP INSTRUCTIONS AND EXAMPLES


     This appendix provides step-by-step instructions for using

Option 1, including worksheets to facilitate calculations.

Substantially the same instructions are used for all of the options.

The differences lie primarily in the tables and worksheets used.

Many of the required tables can be found in Sections 4 and 5,  as

applicable.  Additional tables can be found in Appendix D.

     This appendix also included two examples illustrating  the

application of Options 1 and 2 to a hypothetical wastes site.

C.I  Step-By-Step Instructions

     This section provides step-by-step instructions for evaluating

a site using Option 1.

     Step 1;  For each CERCLA contaminant detected in the ambient

atmosphere, calculate the ratio between the concentration detected

in the site samples and the concentration detected in the background

samples.*  If the background samples are below the detection limit,

then the detection limit should be substituted for the background

concentration.  Select the CERCLA contaminant with the greatest
*These instructions are based on the use of the ratio of background
 to site sample concentrations.  As stated in Section 4, a similar
 approach can be developed using the difference between the
 concentrations.  A discussion of the use of differences in
 determining an observed release can be found in Brown, 1986.
                                181

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ratio ^s the reference conta-nlaan'- and record its Chemical Abstracts

Service (CAS) code, the concentrations detected, and the detection

limit on Worksheet 1:  Observed Release Worksheet (Table C-l).  If

the ratio of the site sample concentration to the background sample

concentration is above 10.J, assign an observed release value of 45.*

If the ratio is above 1.5 and suppressive conditions prevailed during

sampling, assign an observed release value of 45.  Assign a potential

to release value of 0.  Record the release values on Worksheet 1 and

go to Step 9.  Otherwise, record an observed release value of 0 on

Worksheet 1 and go to Step 2.

     Step 2;  Select up to three emission source descriptors from

the list of emission source descriptors (Table 9) that apply to

the site and record the codes for the descriptors selected on

Worksheet 2:  Potential to Release Worksheet (Table C-2).  If more

than three apply, select the three that best describe the site.

Calculate the size of the areas described by the selected

descriptors, including only those applicable areas which contain

waste materials.  In general, the areas covered by the descriptors

selected must be larger than the minimum size in the "Small" size

category.  If this constraint cannot be met, then select only the

descriptor whose size is greatest relative to the minimum size in

its "Small" category.  Emission source descriptor definitions are
*The reader is reminded that tne values of 10 and 1.5 used in Step 1
 are provided for illustrative purposes only.
                                 132

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                             TABLE  C-l

                            WORKSHEET 1:
                     OBSERVED RELEASE WORKSHEET
                                                        Units

REFERENCE CONTAMINANT CAS NUMBER       	

MLMIMUM DETECTION LEVEL                	      	

BACKGROUND CONCENTRATION               	      	

SITE SAMPLE CONCENTRATION              	      	

RATIO                                  	

VALUE (0 or 45)
                                 183

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                               TABLE C-2

                             WORKSHEET 2:
                    POTENTIAL TO RELEASE WORKSHEET
                             Mobility
    Descriptor       Value    Value     Sum    Containment     Product
      Code      Size  (A)      (B)     (A+B)   Value (C)      t(A+B)zC]
(1)

(2)

(3)
(4)      (1)+ (2)+ (3)

(5)      (1) x (2) / 45

(6)      (1) x (3) / 45

(7)      (2) x (3) / 45

(8)      (1) x (2) x (3) /2025

(9)      (4) - (5) - (6) - (7) + (a)

(10)     Potential to Release Value*
*Round-off to nearest whole number.
 Descriptor Code:   From Table 9.
 Size:  From Table 11.
 Des.  Value:  From Table 13.
 Mooility Value:   From Worksheet  5.
 Containment Value:   From Worksheet  6.
                                164

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provided in Appendix D (Table D-l).  Using the table of size ranges




(Table 11), record the sizes selected on Worksheet 2.  Determine the




emission source descriptor values from the emission source descriptor




table (Table 13) and record the values on Worksheet 2.




     Step 3;  Calculate the gas mobility as follows.  For each




emission source descriptor, determine up to five contaminants




identified at the applicable portion of the site from the list of




CERCLA contaminants.  Contaminants whose locations on the site were




not determined cannot be used to evaluate mobility for any descriptor.




Record the CAS codes for the identified contaminants on Worksheet 3:




Gas Mobility Worksheet (Table C-3).  Using the information provided




in the gas mobility tables (Table 15), assess the mobility of each




contaminant and record the results on Worksheet 3.  For R.CRA wastes




and contaminants, the information required can be found in Versar,




1984.  Standard references such as Weast, 1977 contain information on




vapor pressure and Henry's constants for other contaminants.   Versar,




1984 describes the derivation of the dry relative soil volatility




index.  Supplemental information on PCBs can be found in Burkhard,




Andren and Armstrong; 1985a, 1985b.




     Step 4;  Calculate the particulate mobility value as follows.




Estimate the threshold wind speed for the site as indicated in




Cowherd et al., 1985, or use the default value of 12.5 meters per




second.  Record the appropriate value as indicated on Worksheet 4:




Particulate Mobility Worksheet (Table C-4).  Identify the airport
                                 185

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                          TABLE C-3

                        WORKSHEET 3:
                   GAS MOBILITY WORKSHEET
         First Emission Source Descriptor Code 	

     CAS Number     VP Value    AQ Value    RS Value      Sum

(1)     	        	    	    	    	

(2)     	        	    	    	    	

(3)     	        	    	    	    	

(4)     	        	    	    	    	

(5)     	        	    	    	    	

(6)  Average of positive values in lines 1 through 5    	

(7)  Gas Mobility Value for First Emission Source
     Descriptor (see table below)                       	


        Second Emission Source Descriptor Code
     CAS Number     VP Value    AQ Value    RS Value      Sum

(1)     	        	    	    	    	

(2)     	        	    	    	    	

(3)     	        	    	    	    	

(4)     	        	    	    	    	

(5)     	        	    	    	    	

(6)  Average of positive values in lines 1 through 5    	

('/)  Gas Mobility Value for Second Emission Source
     Descriptor (see table below)
VP Value:From Table 15.
AQ Value:  From Table 15.
RS Value:  From Table i5.
                             186

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(1)

(2)

(3)

(4)

(5)
                    TABLE C-3 (Concluded)


         Third Emission Source Descriptor  Code 	

     CAS Number     VP Value    AQ Value    RS Value
(6)  Average of positive values in lines 1 through 5

(7)  Gas Mobility Value for Third Emission Source
     Descriptor (see table below)
                              Sum
                  GAS MOBILITY FACTOR TABLE

         Range of Average Value
       Greater than
       or equal to       Less than
            0
            3
            5
            7
 3
 5
 7
10
Value

  0
  1
  2
  3
VP Value:  From Table 15.
AQ Value:  From Table 15.
RS Value:  From Table 15.
                             187

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                                TABLE C-4

                               WORKSHEET  4:
                      PARTICULATE MOBILITY WORKSHEET
     Weather Station:
     Threshold wind speed8:            	 meters per second (ut)

          Fastest    Precip.    Temp.b
Month     Mile (F)    (P)        (T)       (T-10)    P/(T-lO)   [P/(T-lO)]10/9
Jan.

Feb.

Mar.

Apr.

May

June

July

Aug.

Sept.

Oct.

Nov.

Dec.
Sum =     	                                    Sum
     divide by 12                                               x 115
u  D      	                                    PE Index -
                                 188

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                        TABLE C-4  (Concluded)
Mobility Index (I) = (u+ - ut)/PE2

Particulate Mobility Value (4 - log-,0I)c
aDefault value of 12.5 may be used.
^Methodology is valid in the temperature range 28.5 to 90.0 degrees
 Fahrenheit.  If average monthly temperature is below 28.5 degrees,
 set T-10 equal to 18.5.  If average monthly temperature is above
 90.0 degrees, set T-10 equal to 80.0.
cRound off to nearest whole number.  If logio1 exceeds 4, value = 0.
 If log10I is less than 0.5, value = 3.  The following table provides
 alternate, equivalent way to determine the particulate mobility value.
               ALTERNATE PARTICULATE MOBILITY VALUE TABLE

          Range of Values for I                         Value

         Less than 3.16 x 10~4                            0

       3.17 x 10~4 - 3.16 x 10~3                          1

       3.17 x 10~3 - 3.16 x 10~2                          2
                             _2
       Greater than 3.16 x 10                             3
                                 189

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closest to the site and listed in the Local Climatological Data




Summary.   Calculate the average of the monthly fastest miles recorded




at that airport as indicated on the worksheet.  Calculate the PE Index




as indicated on the worksheet or as estimated from Figure 2.  Record




the PE Index as indicated.  Combine these three estimates as indicated




and record the particulate mobility value.




     Step 5;  Record the gas mobility values for each emission source




descriptor as indicated on Worksheet 5:  Combined Mobility Worksheet




(Table C-5).  Record the particulate mobility value (assumed to be




the same for each descriptor) as indicated on the worksheet.




Calculate the combined mobility values for each descriptor using the




table on the worksheet and record the values as indicated and on




Worksheet 2.




     Step 6:  Evaluate the gas and particulate containment aspects of




the site corresponding to the selected emission source descriptors




using the lists of gas and particulate containment factors (Tables D-3




and D-4).  If more than one containment descriptor corresponds to the




selected emission source descriptor, select the one that best applies.




Record the containment values for each descriptor on Worksheet 6:




Containment Worksheet (Table C-6).




     Step 7;  Combine the site containment values using the combined




containment factor matrix (Table 20) and record the results on




Worksheet 6 and Worksheet 2.
                                 190

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                             TABLE C-5

                           WORKSHEET  5:
                    COMBINED MOBILITY WORKSHEET
    Descriptor
       Code
     Gas Mobility
        Value*
Particulate Mobility     Combined
      Value**             Value
(1)

(2)

(3)
                  COMBINED MOBILITY FACTOR MATRIX

                                  Gas  Mobility Value

                                  0123

                             0:    0     1     23

                             1:    1     2     34

                             2:    2     3     45
Particulate

Mobility

Value
                             3:
 *From Worksheet 3.
**From Worksheet 4.
                                191

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                             TABLE C-6

                            WORKSHEET  6:
                       CONTAINMENT WORKSHEET
    First  Descriptor Code

        Particulate Containment Code

        Gas  Containment Code



    Second Descriptor Code

        Particulate Containment Code

        Gas  Containment Code



    Third  Descriptor Code

        Particulate Containment Code

        Gas  Containment Code
    Descriptor    Particulate  Containment   Gas Containment   Combined
       Code                Value                 Value          Value
(1)

(2)

(3)
Descriptor Code:   From Table 9.
Particulate Containment Code: From Table  D-3.
Gas Containment Code:   From Table D-4.
Combined Value:  From  Table 20.
                                192

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     Step 8;  Combine the values calculated previously as indicated




on Worksheet 2.  This step concludes the calculation of the potential




to release value.




     Step 9;  Select up to five contaminants identified at the site




and calculate the toxicity value as indicated in the Tables 4, 6,




and 7 of the HRS User's Manual (47 FR 31219-31243).  Record these




values on Worksheet 7:  Toxicity-Mobility Worksheet (Table C-7).




Evaluate the mobility of the contaminants as follows.   If the




contaminant has been identified as being emitted from the site in an




observed release, its mobility value is set equal to 3.  If the




contaminant has not been identified as part of an observed release,




then its mobility value is assessed differently.  Mobility values




for particulate contaminants that have not been identified as being




emitted from the site are evaluated using the particulate mobility




factor discussed previously.  The mobility value for a nonemitted




gaseous contaminant is calculated as the average of its vapor




pressure, Henry's constant and dry relative soil volatility values




according to Table 15.  The mobility value for a contaminant present




as both a gas and a particle is the greater of the applicable gas




and particle mobility values.  Combine the toxicity and mobility




values as indicated on the combined toxicity-mobility factor matrix




(Table 22).  Record the highest contaminant toxicity-mobility value




as indicated.
                                 193

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                             TABLE C-7

                            WORKSHEET  7:
                    TOXICITY-MOBILITY WORKSHEET
Toxicity Mobility
CAS Number Value Value
Combined
Value
(1)
(2)
(3)
(4)
(5)
    (6)  Maximum Combined Value
              Level of

              Toxicity
COMBINED FACTOR MATRIX

           Level of Mobility

           0    1    _2   _3

      0:   0    0     00

      1:   0    2     46

                4     8   12
2:
                             3:
                     12   18
VP Value:  From Table 15.
AQ Value:  From Table 15.
RS Value:  From Table 15.
Toxicity Value:  From MRS  User's Manual.
                                 194

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     Step 10;  Record the Observed Release Value (Worksheet 1),




Potential to Release Value (Worksheet 2) and Toxicity-Mobility Value




(Worksheet 7) as indicated on Worksheet 8:  Summary Air Route Score




(Table C-8).




     Step 11;  Evaluate the hazardous waste quantity as indicated in




the HRS User's Manual (47 FR 31219-31243) and record the result  on




Worksheet 8.




     Step 12;  Add lines 3 and 4 on Worksheet 8 as indicated to




determine the waste characteristics value.




     Step 13;  Evaluate the targets, as indicated in the HRS User's




Manual (47 FR 31219-31243) employing the effective source radius,  as




applicable.  Add lines 7, 8, and 9 as indicated.




     Step 14;  Calculate the air migration route score as indicated




on Worksheet 8, lines 11 and 12.




C.2  Hypothetical Examples;  The Clean River Site




     This section presents a hypothetical example of the application




of Options 1 and 2.  It is adapted from the Clean River problem




currently used in HRS training.  It is intended to be realistic  but




the data do not represent a known hazardous wastes site.




     C.2.1  Description of the Site




     The site is a closed chemical manufacturing facility that




was in operation between 1945 and 1968.  It was engaged in the




manufacture of a wide variety of organic and inorganic chemicals.




The facility is located on 20 acres of mostly low-lying land with a






                                 195

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                              TABLE C-8

                            WORKSHEET 8:
                       SUMMARY AIR ROUTE SCORE
 1.  OBSERVED RELEASE VALUE8

 2.  POTENTIAL TO RELEASE VALUEb

 3.  TOXICITY-MOBILITYC

 4.  HAZARDOUS WASTE QUANTITY*1

 5.  WASTE CHARACTERISTICS VALUE (Lines 3 + 4)

 6.  TARGETS

 7.      Population

 8.      Land Used

 9.      Sensitive Environment

10.  TARGETS VALUE (Lines 7+8+9)

11.  If line 1 is not equal to 0.0,
     multiply lines 1 x 5 x 10
     If line 2 is not equal to 0.0,
     multiply lines 2 x 5 x 10

12.  Divide line 11 by 351                       S
aFrom Worksheet 1.
bFrom Worksheet 2.
cFrom Worksheet 7.
dFrom HRS User's Manual.
                                                  a
                                 196

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few hills of low elevation along the Clean River, as depicted in




Figure C-l.  The Clean River flows through the southwest section of




Charles County, and into Union Lake, before reaching the Major River.




Charles County is approximately 50 square miles in area and includes




the incorporated cities of Catsville and Maryville.




     A large portion of the area in Charles County is undeveloped




land.  This undeveloped land consists mainly of agricultural and




marsh land (more than 5 acres) along the Clean River, and also




includes some wooded areas.  The agricultural land and marsh land




are within 1,000 feet of the site fence, but the wooded areas are at




least 5 miles away from the site.




     The developed land is divided among residential and industrial




use.  Both residential and industrial areas are concentrated in



Catsville (population 2,957) and Maryville (population 5,258).  Near




the site there are many privately owned farms which cultivate




vegetable crops with the nearest farm house located approximately




1,000 feet from the site fence (Figure C-2).  A new subdivision of




50 houses, called River View Estates,  was built in 1980 approximately




one mile from the site fence along Suburban Road (Figure C-2).




Construction of 100 additional houses is planned over the next




three years.  The chemical manufacturing facility has recently been




purchased by a housing developer and the old plant is slated for




demolition.
                                 197

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 Key:

 D  Sediment Sampling Location

 •  Surface Water Intake
                                     Catsvllle
                                                                       n
                                                                       t
                            \
                                                      r
Scale
                       2  Miles
                        Irrigation
                          Pond
                                                                       Charles County
                                   FIGURE C-1
                        CLEAN RIVER SITE  LOCATION
                                        198

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 Key:

A Monitoring Well
                           IN

                           t
Scale
           1/8
                         1/4 Miles
    Farm
    House
Farm
House
                                         River View Estimates
                                             <50 Houses)
                                FIGURE C-2
                        CLEAN RIVER SITE PLAN
                                     199

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     The site investigation team found several disposal areas on the




site.  A discussion with the previous owners of the facility revealed




that processing wastes were disposed of on the site.  In particular,




the off-specification products and undesirable by-products of the




processes were disposed of in an abovegrade landfill (30 percent




slope) along the Clean River (Figure C-2).  The landfill has not




been maintained and signs of erosion are everywhere.  When a storm




came through the area in late 1979, the Clean River flooded and a




section of the landfill was eroded away, leaving a portion of the




waste in the landfill exposed.  The land was purchased by the housing




developer in 1980, but the present owner did not take any measures




to secure the landfill from further erosion.  An examination of the




site map reveals that the landfill measures about 245 x 245 feet or




about 60,000 square feet.




     In addition,  wastes of an unspecified origin were disposed of




In two settling ponds.  The ponds are approximately 125 feet in




diameter and 2-1/2 feet deep.  The site investigation team also




located an underground tank (between Buildings B & C), and a drum




storage area located near the landfill.   The underground tank has a




capacity of 50,000 gallons and was half full at the time of the




investigation.   The drums were allegedly removed in 1975 by the




former owners.




     The site Investigation team also found 67 drums in various




degrees of decay inside Building B, with liquid oozing from some of






                                 200

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the drums and contaminating the grassy area behind the building, but




the team did not locate any liner or containment structure in the




grassy area upon searching.




     A summary of the sampling results from the site investigation




is provided in Table C-9.  Samples taken around the top perimeter of




the landfill showed concentrations of arsenic and cadmium, while




leachate from the south toe showed high concentrations of arsenic,




phenol, toluene and benzene.  Wet sludge samples (50 percent water)




from the ponds showed concentrations of heavy metals including




arsenic and cadmium as well as benzene.  A sampling of the contents




of the tank revealed toluene and phenol as its contents.   A sample




of the liquid found leaking from the drums inside Building B




indicated the presence of phenol and toluene.   The various detection




limits were all less than one part per million.




     C.2.2  Step-by-Step Application of the Option 1 Methodology




     This section illustrates the step-by-step application of the




Option 1 air pathway evaluation method to the hypothetical Clean




River site.  The step numbers corresponds directly to the steps  in




Section C.I.




     Step 1 (Observed Release Value);  No air monitoring was




conducted on the site, hence an observed release value of 0 is




assigned (see Table C-10).




     Step 2 (Emission Source Descriptor Values);  The following




Option 1 emission source descriptors can potentially be used in




scoring this site:




                                 201

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                             TA3LE  C-9

           SUMMARY OF SAMPLING RESULTS. CLEAN RIVER SITE
                               (ppm)
Location
Landfill
Cover Soil
Background
Soil
Leachate
Sludge
Drum Liquid
Arsenic

41

15
120
200
ND
Cadmium

19

ND
ND
150
ND
Phenol

ND

NA
250
ND
750
Toluene

ND

NA
350
ND
1550
Benzene

ND

NA
990
0.1
ND
NA:  Not available.
ND:  Not detected.
                                202

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                             TABLE C-10

                         CLEAN RIVER EXAMPLE
              WORKSHEET 1:  OBSERVED RELEASE WORKSHEET
                                                            Units

REFERENCE CONTAMINANT CAS NUMBER          	

MINIMUM DETECTION LEVEL                   	       	

BACKGROUND CONCENTRATION                  	       	

SITE SAMPLE CONCENTRATION                 	       	

RATIO                                     	

VALUE (0 or 45)                               0
                                 203

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     •  flelowground Tanks—5

     •  Contaminated Surface Soil:  Background below analytical
        detection limit; contamination level above analytical
        detection limit—10

     •  Exposed Drums:   Drums broken—11

     •  Landfill:  All other situations—20

     •  Surface Impoundment:  Wet; evidence of waste contamination
        near surface—26

     The principal consideration in selecting a descriptor is whether

there is evidence that hazardous materials have been placed in the

area covered by the selected descriptor.   The sampling data and site

investigation Indicated that hazardous materials have been found,  or

were known to be disposed of, in the tanks, drums,  landfill and

ponds.  The materials have either been disposed of on the surface or

have migrated to the surface.

     The acceptability of the belowground tanks and exposed broken

drums is straightforward.  The contaminated surface soil is

acceptable given the increased cadmium soil level in the cover soil

of the landfill.  The fact that cadmium was found in the soil on the

landfill and not in the landfill would indicate that the cover soil

is contaminated with a material other than that disposed of in the

landfill.   Hence, it can be considered a separate source, distinct

from the landfill.

     No information is provided on the presence of biodegradable

material in the landfill, hence the selection of that descriptor.
                                204

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The wet surface impoundment descriptor was selected for the ponds

reflecting the water content of the sludge samples and the presence

of contaminants in the sludge.

     The sizes of the areas covered by each descriptor also meet the

minimum size requirements:

     •  Belowground Tanks:  50,000 gallons or about 7,000 cubic feet

     •  Contaminated Surface Soil:  About 245 x 245 feet or about
        60,000 square feet

     •  Exposed Drums:  67 drums

     •  Landfill:  About 245 x 245 feet or about 60,000 square feet

     •  Surface Impoundment:  125 in diameter x 2.5 feet in-depth
        each or about 61,000 cubic feet in total

     Of the applicable descriptors, the following three descriptors

best describe the site:

     •  Contaminated Surface Soil:  Background below analytical
        detection limit; contamination level above analytical
        detection limit—10

     •  Landfill:  All other situations—20

     •  Surface Impoundment:  Wet; all other situations—26

     The use of the exposed, broken drum descriptor in place of any

of these three would be acceptable.  The use of the underground tank

descriptor, while acceptable, would not be indicated since its

containment value would be 0.

     The size data indicated that the landfill and ponds would be

considered "medium" while the contaminated surface soil would be

considered "small".  The resulting values are listed on Table C-ll.
                                 205

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                              TABLE C-ll

                          CLEAN RIVER EXAMPLE
             WORKSHEET 2:  POTENTIAL TO RELEASE WORKSHEET
                     Des.    Mobility
Descriptor Value Value Sum Containment
Code Size (A) (B) (A+B) Value (C)
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
20
26
10
(1)H
(1)
(1)
(2)
(1)
(4)
M 3 4 7 3
M 7 4 11 3
S 6 1 7 3
H (2H (3)
x (2) / 45
x (3) / 45
x (3) / 45
x (2) x (3) /2025
- (5) - (6) - (7) + (8)
Potential to Release Value*
Product
[(A+B)rC]
21
33
21
75
15.4
9.8
15.4
7.19
41.59
42
*Round-off to nearest whole number.
 Descriptor Code:   From Table 9.
 Size:  From Table 11.
 Des.  Value:  From Table 13.
 Mobility Value:  From Worksheet  5 (Table C-14).
 Containment Value:   From Worksheet  6 (Table C-15).
                                206

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     Step 3 (Gas Mobility Value);  An examination of the site

information shows that the landfill contains three potentially

gaseous contaminants; phenol, toluene and benzene, while the surface

impoundment contains only one; benzene.  The area covered by the

contaminated surface soil descriptor shows no gaseous contaminants.

The gas mobility value for the contaminated surface soil, therefore,

is 0.  The following values for the three identified gaseous

contaminants were calculated using Table 15 and Versar, 1984:

     •  Phenol (CAS Number 00108-95-2);
        - VP value:  2
        - AQ value:  1
        - RS value:  2

     •  Toluene (CAS Number 00108-88-3);
        - VP value:  3
        - AQ value:  3
        - RS value:  3

     •  Benzene (CAS Number 00071-43-2);
        - VP value:  3
        - AQ value:  3
        - RS value:  3

Phenol, toluene and benzene can be used to evaluate the gas mobility

factor for the landfill, while benzene can also be used in the

evaluation for the surface impoundments.  The gaseous mobility values

for each descriptor are, therefore, as follows (see Table C-12):

Landfill~3, Surface Impoundment—3, Contaminated Surface Soil—0.
                                 207

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                             TABLE C-12

                         CLEAN RIVER EXAMPLE
                WORKSHEET 3:   GAS MOBILITY WORKSHEET

             First Emission Source Descriptor Code    20
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(1)
(2)
(3)
(4)
(5)
(6)
(7)
CAS Number VP Value AQ Value
00108952 2 1
00071432 3 3
00108883 3 3


Average of positive values in lines 1
Gas Mobility Value for First Emission
Descriptor (see table below)
Second Emission Source Descriptor
CAS Number VP Value AQ Value
00071432 3 3




RS Value
2
3
3


through 5
Source
Code 26
RS Value
3




Average of positive values in lines 1 through 5
Gas Mobility Value for Second Emission Source
Descriptor (see table below)
VP Value:From Table 15.
AQ Value:  From Table 15.
RS Value:  From Table 15.
                                                                Sum

                                                                 5
                                                                7.7
                                                               •(•BM^MMH

                                                                 3
                                                                Sum

                                                                 9
                                 208

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                       TABLE C-12 (Concluded)

             Third Emission Source Descriptor Code   08


         CAS Number     VP Value      AQ Value     RS Value     Sum

(1)      	       	      	     	    	

(2)      	       	      	     	    	

(3)      	       	      	     	    	

(4)      	       	      	     	    	

(5)	       	      	     	    	

(6)      Average of positive values in lines 1 through 5       	

(7)      Gas Mobility Value for Third Emission Source            0
         Descriptor (see table below)
                         GAS MOBILITY TABLE

             Range of Average Value
           Greater than
           or equal to       Less than           Value

                030
                351
                5                7                 2
                7               10                 3
VP Value:  From Table 15.
AQ Value:  From Table 15.
RS Value:  From Table 15.
                                 209

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     Step 4 (Particulate Mobility Value);   The Charles County Airport



is the closest weather station to the site that is listed in the



Local Climatological Data Annual Summaries (LCD).   The applicable



data for this airport taken from the LCD are given in Table C-13.



The default threshold friction velocity of 12.5 was employed since



the site investigation does not provide the data needed to calculate



a site-specific value.  The average of the monthly fastest miles is



40.25 miles per hour or 17.99 meters per second.  The PE index for



the site is 90.  This results in a Particulate Mobility Index of


         -4
6.78 x 10  .  Using the equation for the partlculate mobility



value results in a value of 1 for the site (see Table C-13).  This



value also applies to any particulate contaminant in calculating the



toxicity-mobility value for that contaminant.



     Step 5 (Combined Mobility Value):  The gas and particulate



mobility values are recorded on Worksheet 5 (Table C-14) and the



combined mobility values for each descriptor calculated as



indicated.



     Step 6 and Step 7 (Containment Values);  The site description



indicates that the landfill cover has been eroded and that waste



material is exposed to the atmosphere.  Also, the slope of the



landfill is estimated to be 30 percent.  Thus, the particulate



containment descriptor LF05P:  "Site substantially devoid of



vegetation with a large percentage of exposed soil or waste-bearing



liquids.  No other cover.  Facility slope greater than 10 degrees





                                 210

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                             TABLE C-13

                         CLEAN RIVER EXAMPLE
            WORKSHEET 4:  PARTICULATE MOBILITY WORKSHEET
     Weather Station:
Charles County Airport
Threshold wind speeda:
Fastest Precip.
Month Mile (F) (P)
Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
40
30
47
46
41
41
43
45
46
40
31
33
2.83
2.64
3.43
3.14
3.62
4.23
3.75
4.16
3.26
3.01
2.99
3.29
12
Temp.b
(T)
31.4
33.6
42.4
43.3
62.4
70.7
75.5
74.3
67.4
55.3
44.8
35.1
.5 meters per secc
(T-10)
21.4
23.6
32.4
33.3
52.4
60.7
65.5
64.3
57.4
45.3
34.8
25.1
P/CT-10)
0.1322
0.1119
0.1059
0.0725
0.0691
0.0697
0.0573
0.0647
0.0568
0.0664
0.0859
0.1311
jnd (ut)
[P/(T-10)]10/9
0.1056
0.0877
0.0825
0.0542
0.0513
0.0518
0.0417
0.0477
0.0413
0.0491
0.0654
0.1046
Sum =     483

    divide by 12

u+ -      40.25
          17.99 meters per second
                  Sum
0.7829
                       x  115

             PE Index  =    90
                                 211

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                       TABLE C-13 (Concluded)
Mobility Index (I) - (u+ - ut)/PE2                   6.78 x 10

Particulate Mobility Value (4 - log10Dc                 1
aDefault value of 12.5 may be used.
Methodology is valid in the temperature range 28.5 to 90.0 degrees
 Fahrenheit.  If average monthly temperature is below 28.5 degrees,
 set T-10 equal to 18.5.  If average monthly temperature is above
 90.0 degrees, set T-10 equal to 80.0.
cRound off to nearest whole number.  If logiQl exceeds 4, value " 0.
 If log^o1 is less than 0.5, value " 3.  The following table provides
 alternate, equivalent way to determine the particulate mobility value.
               ALTERNATE PARTICULATE MOBILITY VALUE TABLE

         Range of Values for I                          Value
                            -4
         Less than 3.16 x 10                              0

       3.17 x 10~4 - 3.16 x 10~3                          1

       3.17 x 10~3 - 3.16 x 10"2                          2

       Greater than 3.16 x 10                             3
                                 212

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                             TABLE C-14

                         CLEAN RIVER  EXAMPLE
              WORKSHEET 5:   COMBINED  MOBILITY WORKSHEET
(1)

(2)

(3)
Descriptor
   Code

    20

    26

    08
Gas Mobility
   Value*

     3

     3
                                   Particulate Mobility
                                         Value**
Combined
 Value

   4

   4

   1
                   COMBINED MOBILITY FACTOR MATRIX
              Particulate

              Mobility

              Value
                               Gas Mobility Value

                               0     ill

                         0:     0     123

                         1:1     234

                         2:     2     345

                         3:     3     455
 *From Worksheet 3.
**From Worksheet 4.
                                213

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was selected as the best containment descriptor.  The value for this




descriptor is 3.  Similarly, since the waste material is exposed,




tne gas containment descriptor LF15G:   "Waste uncovered or exposed"




was selected as the best gas containment descriptor.  The value for




this descriptor is 3.  Therefore, the combined containment descriptor




value for the landfill is 3 (see Table C-15).




     There is little information provided on the state of the ponds.




Since the impoundments do not contain liquids (only a wet sludge




resting at the bottom), the depth of the impoundment can be taken




as the freeboard.  Therefore, the impoundment can be considered



"enclosed".  The information provided on the impoundment indicates




that the descriptor WSI05P:  "Enclosed impoundment; uncovered,




surface completely open to atmosphere" is the best applicable




descriptor.  Its value is 3.  The best gas containment descriptor




for tne impoundment is WSI05G:  "Wet enclosed impoundment; uncovered,




surface completely open to atmosphere" with an associated value of 3.




Therefore, the combined value for the surface impoundment is 3 (see




Table C-15).




     The containment descriptors in Option 1 are the same for the



contaminated surface soil descriptors as they are for the landfill




descriptors.  There is also little information provided for the




surface of the landfill, the area of known soil contamination.




Given the information provided, except that signs of erosion are




everywhere, the best particulate containment descriptor is LF05P:






                                 214

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                              TABLE C-15

                         CLEAN RIVER EXAMPLE
                 WORKSHEET 6:  CONTAINMENT WORKSHEET
         First Descriptor Code

              Particulate Containment Code

              Gas Containment Code
  20
 LF05P
 LF15G
         Second Descriptor Code

              Particulate Containment Code

              Gas Containment Code
  26
WSI05P

WSI05G
         Third Descriptor Code

              Particulate Containment Code

              Gas Containment Code
  10

 LF05P

 LF08G
Descriptor Particulate Containment Gas Containment Combined
(1)
(2)
(3)
Code
20
26
08
Value
3
3
3
Value
1
3
_1 	
Value
3
3
3
Descriptor Code:  From Table 9.
Particulate Containment Code:  From Table D-3.
Gas Containment Code:  From Table D-4.
Combined Value:  From Table 20.
                                 215

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"Site substantially devoid of vegetation with a large percentage of




exposed soil or waste-bearing liquids.   No other cover.   Facility




slope greater than 10 degrees" with an  associated value of 3.




Similarly, since the soil type is unknown, the best gas containment




descriptor is LF08G:  "Uncontaminated soil cover less than six




inches; cover soil type unknown" with an associated value of 1.




Therefore, the combined containment value for the contaminated




surface soil is 3 (see Table C-15)-




     Step 8 (Potential To Release Value);  The preceding data are




recorded on Table Oil.  This table also illustrates the calculation




of the potential to release value for the site.   Thus,  the overall




site potential to release value is 42,  based on  the Option 1




methodology.




     Step 9 (Toxicity-Mobility Value):   Since none of the




contaminants have been detected in an observed release,  the mobility




value for each is calculated using the  gas or particulate mobility




value as applicable.  Therefore, the mobility values for the gaseous




contaminants are as follows:




     •  Phenol (CAS Number 00108-95-2):  2




     •  Benzene (CAS Number 00071-43-2):  3




     •  Toluene (CAS Number 00108-88-3):  3




Arsenic (CAS Number 07440-37-1) and cadmium (CAS Number 07440-43-9)




would appear as particulates and, therefore, their mobility values




are set equal to the site particulate mobility value of 1.
                                216

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     The HRS (47 FR 31219-31243) indicated the following air

toxicity values for the contaminants:

     •  Phenol:  3

     •  Toluene:  2

     •  Benzene:  3

     •  Cadmium:  3

     •  Arsenic:  3

     These values and the combined toxicity-mobility values for each

contaminant are indicated in Table C-16.  These values indicate that

benzene has the largest combined toxicity-mobility value and thus the

site toxicity-mobility value is 18.

     Step 10;  The Observed Release Value (Worksheet 1), Potential

to Release Value (Worksheet 2), and Toxicity-Mobility Value

(Worksheet 7) are recorded on Worksheet 8:  Summary Air Route Score

(Table C-17).

     Step 11 (Waste Quantity Value);  The site description provides

the following data pertinent to the calculation of hazardous waste

quantity:

     •  67 drums in Building B

     •  Volume of ponds is about 61,000 cubic feet

     •  Belowground tank contains about 25,000 gallons of phenol and
        toluene

     •  Contaminated surface area of the landfill is about 60,000
        square feet

     •  All of the above contained hazardous materials


                                 217

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                             TABLE  C-16

                        CLEAN RIVER EXAMPLE
             WORKSHEET 7:  TOXICIIY-MOBILITY WORKSHEET
(1)
(2)
(3)
(4)
(5)
CAS Number
00108952
00108883
00071432
07440371
07440439
Toxicity
Value
3
2
3
3
3
Mobility
Value
2
3
3
1
1
Combined
Value
12
12
18
6
6
(6)   Maximum Combined Value
                                        18
              Level of

              Toxicity
COMBINED FACTOR MATRIX

            Level of Mobility

            0    1    _2  _3

      0:    0    0     00

      1:0     246

      2:    2    4     8   12

      3:    4    6    12   18
VP Value:  From Table 15.
AQ Value:  From Table 15.
RS Value:  From Table 15.
Toxicity Value:  From HRS  User's Manual.
                                218

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                             TABLE C-17

                         CLEAN RIVER EXAMPLE
                WORKSHEET 8:   SUMMARY AIR ROUTE SCORE
 1.  OBSERVED RELEASE VALUE3                                    	0_

 2.  POTENTIAL TO RELEASE VALUEb                                  42

 3.  TOXICITY-MOBILITYC                            18

 4.  HAZARDOUS WASTE QUANTITY*1                   	7
 5.  WASTE CHARACTERISTICS VALUE (Lines 3+4)                    25

 6.  TARGETS

 7.      Population                                18

 8.      Land Used                               	3_

 9.      Sensitive Environment                      3

10.  TARGETS VALUE (Lines 7+8+9)                              24

11.  If line 1 is not equal to 0.0,
     multiply lines 1 x 5 x 10                                 	
     If line 2 is not equal to 0.0,
     multiply lines 2 x 5 x 10                                 25200

12.  Divide line 11 by 351                       Sa =          71.79
aFrom Worksheet 1.
bFrom Worksheet 2.
cFrom Worksheet 7.
      HRS User's Manual.
                                 219

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Current practice in the HRS allows the inclusion of the 67 drums and




the once-filled volume of the ponds in computing hazardous waste




quantity.




     No information is given in the site description that would allow




the analyst to determine if the material in the tank is available for




migration.  Thus, current HRS practice would not allow the inclusion




of the 25,000 gallons in the tank.




     Additionally, no information is provided about the volume of the




landfill or the fraction of the volume that is hazardous.  Similarly,




data are lacking on the depth (and hence, volume) of the contaminated




soil on the surface of the landfill (although concentration data are




available in this case).  Therefore, no hazardous waste quantity can




be associated with either the landfill or the contaminated surface




soil.




     Based on these considerations, the total hazardous waste




quantity is 67 drums plus 9,090 drums (the equivalent volume of the




ponds) for a total of 9,157 drums.  This yields a waste quantity




value of 7.




     Step 12 (Waste Characteristics Value):  Add lines 3 and 4 on




Worksheet 8 as indicated to form the waste characteristics value.




     Step 13 (Targets Value);  Building il and the landfill are the




two identifiable potential sources of air releases that are the




furthest apart (see Figure C-2).  The distance between then is
                                 220

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1/4 mile, according to the site map.  Thus, the effective source




radius is 1/8 mile or 660 feet.




     The map of the site (Figure C-2) indicates that one farmhouse




is located within 3/8 (1/4 + 1/8) miles of the site.  No additional




houses lie within 5/8 (1/2 + 1/8) miles of the site.  All of




Riverview Estates (50 houses) lies within 1-1/8 (1 + 1/8) miles of




the site, as do the three identified farm houses.  The town of




Catsville lies within 4-1/8 miles of the site as does a small portion




of the town of Maryville.




     The value for the population residing within 3/8 miles of the




site is 18.  The number of people residing within 1-1/8 miles of the




site cannot be determined from the data presented but can be seen to




be undoubtedly less than the 3,001 persons needed to achieve a value




greater than 18.  The population of Catsville and the small portion




of Maryville located within 4-1/8 miles of the site is less than the




10,000 persons required to achieve a value greater than 18, as well.




Therefore, the population targets value for this site is 18.




     The distance to the nearest wetland is less than 1,000 feet but




may be more than 100 feet (the information provided is not specific).




The wetland lies along the Glean River and is a fresh water wetland.




No critical habitats of Federal endangered species have been




identified near the site.  Therefore, the sensitive environment




value is 2.
                                 221

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     No national or state parks, forests, or wildlife preserves have

been identified within two miles of the site.  No historic or

landmark sites have been identified as being within view of the

site, either.

The nearest residential area is the River View estates, one mile

from the site.  Agricultural land has been found within 1,000 feet

of the site but it is unknown whether this land is prime or not.

The distance to the nearest industrial/commercial area is also

unknown.  Based on the distance to the nearest agricultural land,

the land use value is 3.

     These values are recorded on Table C-17-

     Step 14 (Overall Air Pathway Value);  Table C-17 illustrates

the calculation of the overall air pathway score of 71.19 for the

Clean River site.

     C.2.3  Application of the Option 2 Methodology

     The steps taken in evaluating the site using the Option 2

methodology are very similar to those taken in the Option 1

methodology.  The principal differences are in the tables of factors

used and the worksheets.

     Step 1 (Observed Release Value);  No air monitoring was

conducted on the site, hence an observed release value of 0 is

assigned (see Table C-10).

     Step 2 (Emission Source Descriptor Values);  The following

Option 2 emission source descriptors can potentially be used in

scoring this site:
                                 222

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     •  Containers—1

     •  Contaminated Soil—2

     •  Landfill—4

     •  Surface Impoundment—5

     The justifications for employing these descriptors has been

discussed previously (see Section C.2.2).  Note, the descriptor

"containers" can refer to either the underground tanks and the

exposed drums.  However, the sources are not similar in containment.

Hence, they must be evaluated separately.

     The sizes of the areas covered by each descriptor are as

follows:

     •  Containers (underground tanks):  50,000 gallons or about
        7,000 cubic feet.

     •  Contaminated Soil:  About 245 x 245 feet or about 60,000
        square feet.

     •  Containers (drums):  67 drums.

     •  Landfill:  About 245 x 245 feet or about 60,000 square feet.

     •  Surface Impoundment:  125 in diameter x 2.5 feet in depth
        each or about 61,000 cubic feet in total.

All of the area meet the minimum size requirement and thus can be

used in evaluating the site's potential to release.  The values

for the remaining emission source descriptors are indicated on

Worksheet 1:  Potential to Release Worksheet (Table C-18).

     Step 3 (Gas Mobility Value);  The gas mobility values for each

descriptor have been discussed previously and are as follows:
                                 223

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                             TABLE C-18

                            WORKSHEET 1:
                   POTENTIAL TO RELEASE WORKSHEET
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
Descriptor
Code
01*
02
04
05
01**



Potential
Des.
Value
(A)
4
7
6
8
4



Mobility
Value
(B)
4
1
4
4
4



Sum
(A+B)
8
8
10
12
8



Containment
Value
(C)
3
3
3
3
1



to Release Value
Product
[(A+B)xC]
24
24
30
36
8



36

 *Drums.
**Underground tanks.
                                224

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     •  Containers—3




     •  Contaminated Soil—0




     •  Landfill—3




     •  Surface Impoundment—3




     Step 4 (Particulate Mobility Value);  The evaluation discussed




previously indicated that the PE index for the site is 90.   Thus,




the particulate mobility value for all descriptors is 1.




     Step 5 (Combined Mobility Value);  The gas and particulate




mobility values are summed from the applicable mobility factors for




each descriptor, yielding the following results:




     •  Containers (both types)—4




     •  Contaminated Soil—1




     •  Land fin—4




     •  Surface Impoundment—4




These values are recorded on Worksheet 1 (Table C-18).




     Step 6 and Step 7 (Containment Values);  Based on the site




investigation and the previous discussion, the containment descriptors




indicated on Worksheet 2;  Containment Worksheet (Table C-19)  were




selected.   The combined containment values were determined using




Table 20 and the results recorded on Worksheet 1 (Table C-18).




     Step 8 (Potential To Release Value);  The preceding information




is used to determine the potential to release values for each



descriptor.  The potential to release value for the site, as a whole,
                                 225

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                    TABLE C-19

                   WORKSHEET  2:
               CONTAINMENT WORKSHEET
First Descriptor Code
     Participate Containment Code
     Gas Containment Code

Second Descriptor Code
     Particulate Containment Code
     Gas Containment Code

Third Descriptor Code
     Particulate Containment Code
     Gas Containment Code

Fourth Descriptor Code
     Particulate Containment Code
     Gas Containment Code

Fifth Descriptor Code
     Particulate Containment Code
     Gas Containment Code

Sixth Descriptor Code
     Particulate Containment Code
     Gas Containment Code

Seventh Descriptor Code
     Particulate Containment Code
     Gas Containment Code

Eighth Descriptor Code
     Particulate Containment Code
     Gas Containment Code
C007P
COTF7G
LD04P
LD15G
LD04P
LD15G
SI05P
SI06G
LD11P
LD08G
              01
              02
              04
              05
              01
                        226

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                       TABLE C-19  (Concluded)


                          Particulate            Gas
      Descriptor          Containment        Containment    Combined
         Code                Value              Value        Value

(1)        01                   3                  3            3

(2)        02                   3                  1            3

(3)        04                   3                  3            3

(4)        05                   3                  3            3

(5)        01                   1                  1            1

(6)       	                	              	        	

(7)       	                	              	        	

(8)                                                           	
                                 227

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is the largest of the calculated values.   Thus, using the Option 2



methodology, the site potential  to  release value  is 36.
                                228

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                             APPENDIX D




                         ADDITIONAL TABLES






     This appendix presents the additional tables needed to implement




the proposed revision options.  The tables include the fundamental




definitions of the emission source descriptors (Table D-l), as well




as the particulate and gas containment factor definitions and values




for both Options 1 and 1A.
                                 229

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                              TABLE D-l

               EMISSION SOURCE DESCRIPTOR DEFINITIONS
Active Fire;  A wastes site that is presently burning or smoldering
and, without remedial action, will continue to do so for an extended
period of time.

Belowground Injection;  Belowground injection is a liquid waste
disposal method in which the wastes are emplaced belowground using a
bored, drilled, driven, or dug well to a depth significantly below
the surface.  The well rigs may or may not be present on the site.
If they are missing evidence of the injection, holes should still be
present.  If the disposal method is a dug well, then its depth must
exceed its width, otherwise it is considered to be a surface
impoundment.

Belowground Tank;  A tank is any stationary device, designed to
contain an accumulation of waste, which is constructed primarily of
nonearthen materials (such as wood, concrete, steel, or plastic)
which provide structural support.  A belowground tank is a tank the
entire surface area of which is situated completely below the plane
of ground level.  Belowground tanks are not externally viewable.
The descriptors "Inground or Aboveground Tanks" should be used
whenever the tanks are at least partially exposed.

Contaminated Surface Soil;  Contaminated surface soil is soil taken
from the surface of a site that contains detectable concentrations
of a hazardous substance.  Evidence that the substance detected is
related to the site must be provided to substantiate use of this
descriptor.

Emission Sources Not Elsewhere Specified;  This descriptor refers
to situations not adequately handled by the other descriptors.  A
complete, written description of the site must be provided as support
for the decision to use this descriptor.

Exposed Drum Site;  A drum is any portable device in which waste is
stored or otherwise handled.  An exposed drum site is a site in
which drums are placed or stacked on the surface of the land without
a soil cover.  It also covers the situation in which drums are
buried but partially exposed.  The individual drums may be broken or
intact.  Sites with completely buried drums are considered landfills.
                                 230

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                        TABLE D-l (Continued)
Inactive Aboveground Fire;  A wastes site that is located aboveground
and was at one time significantly inflamed but is not presently
burning.

Inground or Aboveground Tanks;  A tank is any stationary device,
designed to contain an accumulation of waste, which is constructed
primarily of nonearthen materials (such as wood, concrete, steel, or
plastic) which provide structural support.  Any tank situated in
such a manner that the bottom of the tank is at or above the plane
of ground level is considered to be aboveground.  A tank is
considered to be inground if its base is to any degree situated
below the plane of ground level and is in direct contact with the
ground (ignoring liners) such that a portion of the tank wall of
tank top is above the ground and a portion of the tank wall is
belowground (not externally viewable).

Landfarm/Landtreatment;   Landfarming or landtreatment is a method of
waste disposal in which liquid wastes or sludges are spread over
land and tilled, generally to a depth of about six inches.  It also
applies to the shallow (i.e., of insufficient depth) injection of
liquids if the depth of injection exceeded six inches but did not
qualify as belowground injection.  The wastes are reduced or
detoxified through a combination of evaporation, volatilization and
microbiological activity.  Landfarm/landtreatment areas are
frequently revegetated after the wastes have decomposed.  The
distinguishing characteristic of landfarms and landtreatment
facilities is the shallow injection or tilling of the soil.  In
those cases where tilling was not performed or when the depth of
injection was less than six inches, the site should be considered a
spill site.

Landfill;  A landfill is a manmade or natural hole in the ground,
containing wastes, that has been backfilled with soil either after
or contemporary with the waste disposal, covering the wastes from
view.  The landfill may have been formed either by excavating the
hole or by forming earthen walls around a cleared area.  The
characteristics of a landfill that distinguish it from an open pit
or a pile are that the wastes must be co-mingled with soil and that
the wastes must be, or have been, covered with soil.  Due to
weathering, erosion and similar  phenomena, however, once-buried
wastes  in a landfill may become  exposed, e.g., partially buried
drums.  The contents of a landfill may include nearly any or all
types of wastes including buried drums.
                                 231

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                        TABLE  D-l  (Continued)
Open Pit;  An open pit has many of the characteristics of a landfill,
the critical differences being that the wastes are not necessarily
belowground level, soil is not intentionally co-mingled with the
wastes and the wastes are not intentionally covered with soil.   As
a result, the wastes are exposed to the elements,  vectors and
scavengers.  As in the case of landfills,  the contents of an open
pit may include nearly any or all types of wastes.  However, for
purposes of scoring, disposed or stored drums are  considered
separately (see exposed drum site definition).

Spill Site;  A spill site is a site at which a significant amount
(i.e., at least a "reportable quantity") of liquid wastes or sludges
has been intentionally or unintentionally deposited over the ground
and left otherwise untouched.  This descriptor also applies to
landfarms/landtreatment facilities where either tilling was not
performed or the wastes were tilled to a depth less than six Inches.
Similarly, this descriptor applies to sites where  shallow injection
of wastes to a depth less than six Inches was performed.

Surface Impoundment;  A natural topographic depression,  manmade
excavation or diked area, primarily formed from earthen materials
(lined or unlined) which was designed to hold an accumulation of
liquid wastes, wastes containing free liquids, or  sludges that were
not backfilled or otherwise covered.  If the impoundment has been
backfilled, it is considered a landfill.  The intention of a surface
impoundment is to provide temporary storage or to  allow the deposited
liquid to be treated and rendered harmless in the  future or
volatilize and/or evaporate eventually leaving a "dry" residue to be
covered as in a landfill.  The distinguishing characteristics of a
surface impoundment are the emphasis on liquid waste and the general
lack of a cover.  Two types of surface impoundments are distinguished
in the air pathway:  those with exposed liquid (wet) or those at
which the deposited liquid has evaporated, volatilized or leached
(dry).  Synonymous terms include lagoon, pond, aeration pit,
settling pond, and tailings pond.

Surface Water Body or Outfall;  A surface water body is an open
expanse of water restricted only by natural topography, e.g.,
rivers, lakes, streams, etc.  A surface water outfall is the area of
interface between a waste discharge stream and a surface water body.
This descriptor is for use in those situations where water sampling
indicates the presence of volatile compounds in the water.

Waste Pile;  Any noncontalnerlzed accumulation of  solid, nonflowing
wastes.  Waste piles include tailings piles but exclude tailings
ponds.
                                 232

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                                TABLE D-2

                  RELATIONSHIP BETWEEN OPTION 1 AND 1A
                       EMISSION SOURCE DESCRIPTORS
Option 2 Emission
Source Descriptor

Active Fire Site

Belowground/Buried
  Containers

Contaminated Soil
        Option 1 Emission
        Source Descriptor
Dry Surface Impoundment
Inactive Fire Site
Intact Exposed/Aboveground
  Containers
Active Fire Site

Belowground Tanks
Contaminated Surface Soil:
•  Background at or above
   analytical detection limit
   - Contamination level at or
     below background
   - Contamination level above
     background but not
     significantly above background
   - Contamination level
     significantly above background
•  Background below analytical
   detection limit
   - Contamination level below
     analytical detection limit
   - Contamination level above
     analytical detection limit

Surface Impoundment:
•  Dry; evidence of waste
   contamination near surface
•  Dry; all other situations
•  Spill Site:  spill dry

Inactive Aboveground Fire Site:
•  Re-ignition expected
•  Re-ignition not expected
Inactive Below Ground Fire Site
•  Re-ignition expected
•  Re-ignition not expected

Exposed Drums:  Drums intact
Aboveground or Inground Tanks:
Tanks intact
                                 233

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                          TABLE D-2 (Continued)
Option 2 Emission                             Option 1 Emission
Source Descriptor                             Source Descriptor

Landfarm                              Landfarm/Landtreatment
                                      Belowground Injection

Landfill                              Landfill:
                                      •  With both biodegradable material
                                         and exposed drums
                                      •  With biodegradable material but
                                         without  exposed drums
                                      •  All other situations
                                      Open  Pit
                                      Belowground Tanks

Nonintact Exposed/                    Exposed Drums:   Drums broken
Aboveground Containers:                Aboveground or Inground Tanks:
                                      Tanks broken

Wet Surface Impoundment                Surface Impoundment:
                                      •  Wet;  evidence of waste
                                         contamination near surface
                                      •  Wet;  all other situations
                                      Spill Site:   spill wet

Emission Sources Not                  Surface Water Body or Outfall
Elsewhere Specified                   Emission Sources Not  Elsewhere
                                      Specified
                                234

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                              TABLE D-3

              OPTION 1 PARTICULATE CONTAINMENT FACTORS
              (CHOOSE CHARACTERISTIC THAT BEST APPLIES)
ACTIVE FIRE SITE (AFS01)                                        	3_

BELOWGROUND INJECTION (BGI01)                                   	0_

BELOWGROUND TANKS (see Landfill)

CONTAINERS (Aboveground or Inground Tanks and Exposed Drums)

  C001P     Intact, sealed containers protected from the        	0_
              weather by a maintained cover
  C002P     Intact, sealed containers not protected from        	1_
              the weather by a maintained cover
  C003P     Open, unsealed, or nonintact containers; waste      	0_
              totally covered with an essentially impermeable,
              maintained cover
  C004P     Open, unsealed, or nonintact containers; waste        1_
              partially covered with an essentially
              impermeable, maintained cover
  C005P     Open, unsealed, or nonintact containers;            	2_
              wastetotally covered with an essentially
              impermeable, unmaintained cover
  C006P     Open, unsealed, or nonintact containers; waste      	3_
              waste otherwise covered or uncovered
  C007P     Other                                               	1_

CONTAMINATED SURFACE SOIL (see Landfill)

DRY SURFACE IMPOUNDMENT (see Landfill)

EMISSION SOURCES NOT ELSEWHERE SPECIFIED

  NES01P    Totally covered with a maintained covered
  NES02P    Partially covered with a maintained covered
  NES03P    Totally covered with an unmaintained covered
  NES04P    Partially covered with an unmaintained covered
  NES05P    Uncovered
  NES06P    Other

INACTIVE ABOVEGROUND FIRE SITE (see Landfill)
                                 235

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                        TABLE D-3 (Continued)
INACTIVE BELOW GROUND FIRE SITE (see Landfill)

LANDFARM/LANUTREAIMENT (see Landfill)

LANDFILL

  LF01P     Site covered with an essentially impermeable
              and maintained cover or heavily vegetated
              with no exposed soil or waste-bearing liquids
              (e.g., paved-over)
  LF02P     Site substantially vegetated or totally covered
              with a maintained nonwater-based dust-
              suppressing fluid.  Little exposed soil or
              waste-bearing liquids
  LF03P     Site lightly vegetated or partially covered
              with a maintained nonwater-based dust-
              suppressing fluid.  Much exposed soil or
              waste-bearing liquids
  LF04P     Site substantially devoid of vegetation with
              a large percentage of exposed soil or
              waste-bearing liquids.   No other cover.
              Facility slope less than 10 degrees or unknown
  LF05P     Site substantially devoid of vegetation with
              a large percentage of exposed soil or
              waste-bearing liquids.   No other cover.
              Facility slope greater than 10 degrees
  LF06P     Totally enclosed in a structurally intact
              building
  LF07P     Partially enclosed in a structurally intact
              building
  LF08P     Totally enclosed in an nonintact building
  LF09P     Partially enclosed in an nonintact building
  LF10P     Substantially surrounded with windbreak
              (e.g., mesh or other fence, trees, etc.)
  LF11P     Active fire site
  LF12P     Other

OPEN PIT (see Landfill)

SPILL SITE

            Spill dry (see Landfill)
            Spill wet (see Wet Surface Impoundment)
                                 236

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                        TABLE D-3  (Concluded)
SURFACE WATER BODY OR OUTFALL (see Wet Surface Impoundments)

WASTE PILE (see Landfill)

WET SURFACE IMPOUNDMENTS

  WSI01P    Enclosed* impoundment; impoundment totally
              covered with a maintained cover
  WSI02P    Enclosed impoundment; impoundment totally
              covered with an unmaintained cover
  WSI03P    Enclosed impoundment; impoundment partially
              covered with a maintained cover
  WSI04P    Enclosed impoundment; impoundment partially
              covered with an unmaintained cover
  WSI05P    Enclosed impoundment; uncovered,  surface
              completely open to atmosphere
  WSI06P    Nonenclosed impoundment;  impoundment totally
              covered with a maintained cover
  WSI07P    Nonenclosed impoundment;  impoundment totally
              covered with an unmaintained cover
  WSI08P    Nonenclosed impoundment;  impoundment partially
              covered with a maintained cover
  WSI09P    Nonenclosed impoundment;  impoundment partially
              covered with an unmaintained cover
  WSI10P    Nonenclosed impoundment;  uncovered,  surface
              completely open to atmosphere
  WSI11P    Other
*An enclosed impoundment is one with a freeboard exceeding two feet
 in height or one that is substantially surrounded by a wall,  fence,
 trees, or other adequate windbreak.
                                 237

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                              TABLE D-4

                  OPTION 1 GAS CONTAINMENT FACTORS
              (CHOOSE  CHARACTERISTIC THAT BEST APPLIES)
ACTIVE FIRE SITE

  AFS01G    Active aboveground fire site                        	3_

  AFS02G    Active belowground fire site:  Uncontaminated*      	1_
              soil cover in excess of two feet
  AFS03G    Active belowground fire site:  Uncontaminated*      	2_
              soil cover less than two feet, soil resistant
              to gas migration**
  AFS04G    Active belowground fire site:  Uncontaminated*      	3_
              soil cover less than two feet, soil not
              resistant to gas migration**

BELQWGROUND INJECTION (see Landfill)

BELOWGROUND TANKS (see Landfill)

CONTAINERS (Aboveground or Inground Tanks and Exposed Drums)

  C001G     Intact, sealed containers protected from the        	0_
              weather by a maintained cover
  C002G     Intact, sealed containers not protected from        	1_
              the weather by a maintained cover

  C003G     Open, unsealed, or nonintact container; waste       	0_
              totally covered with an essentially impermeable,
              maintained cover
  C004G     Open, unsealed, or nonintact container;             	1_
              waste partially covered with an essentially
              Impermeable, maintained cover
  C005G     Open, unsealed, or nonintact container;             	2_
              waste totally covered with an essentially
              impermeable, unmaintained cover
 *Lacking contrary evidence, covering soils are assumed to be
  Uncontaminated.  Soil cover contaminants must be attributable to
  the underlying waste materials and gaseous in origin.
**USGS soil types GC, ML, CL and CH.  Source:  Adapted from
  Lutton, R. J., Evaluating Cover Systems for Solid and Hazardous
  Wastes, (EPA-530/SW-867c), U.S. Environmental Protection Agency,
  Washington, DC, September 1980.
                                 238

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                        TABLE D-4 (Continued)
CONTAINERS (Concluded)

  C006G     Open, unsealed, or nonintact container; waste
              otherwise covered or uncovered

  C007G     Aboveground containers; other

CONTAMINATED SURFACE SOIL (see Landfill)

DRY SURFACE IMPOUNDMENTS (see Landfill)

EMISSION SOURCES NOT ELSEWHERE SPECIFIED

  NES01G    Totally covered with a maintained covered
  NES02G    Partially covered with a maintained covered
  NES03G    Totally covered with an unmaintained covered
  NES04G    Partially covered with an unmaintained covered
  NES05G    Uncovered
  NES06G    Other

INACTIVE ABOVEGROUND FIRE SITE (see Landfill)

INACTIVE BELOWGROUND FIRE SITE (see Landfill)

LANDFARM/LANDTREATMENT (see Landfill)
LANDFILL

  LF01G
  LF02G
  LF03G

  LF04G

  LF05G
Functioning gas collection system
Existing, nohfunctioning gas collection system
Intact synthetic cover plus uncontaminated soil
  cover over 0.5 inches in depth*
Totally covered with an intact synthetic cover;
  surface soil contaminated*
Totally covered with a nonintact synthetic
  cover; surface soil contaminated*
JL_

 2
 *Lacking contrary evidence, covering soils are assumed to be
  uncontaminated.  Soil cover contaminants must be attributable to
  the underlying waste materials and gaseous in origin.
**USGS soil types GC, ML, CL and CH.  Source:  Adapted from
  Lutton, R. J., Evaluating Cover Systems for Solid and Hazardous
  Wastes, (EPA-530/SW-867c), U.S. Environmental Protection Agency,
  Washington, DC, September, 1980.
                                 239

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                        TABLE  D-4  (Continued)
LANDFILL (Concluded)

  LF06G     Uncontaminated soil cover* in excess of six
              inches
  LF07G     Uncontaminated soil cover* greater than one
              inch and less than six inches; cover soil
              resistant to gas migration**
  LF08G     Uncontaminated soil cover* less than six inches;
              cover soil type unknown
  LF09G     Uncontaminated soil cover* greater than one
              inch and less than six inches; cover soil not
              resistant to gas migration**
  LF10G     Uncontaminated soil cover* less than one inch;
              cover soil resistant to gas migration**
  LF11G     Uncontaminated soil cover* less than one inch;
              cover soil not resistant to gas migration**
  LF12G     Covering soil contaminated* with waste
              contaminants at surface and no synthetic
              cover between surface and bulk of waste
              materials
  LF13G     Totally enclosed in a structurally intact
              building
  LF14G     Totally enclosed in an nonintact building
  LF15G     Waste uncovered or exposed
  LF16G     Other

OPEN PIT (OP01)

SPILL SITE

            Spill Dry (see Landfill)
            Spill Wet (see Wet Surface Impoundment)

SURFACE WATER BODY OR OUTFALL (see Wet Surface Impoundment)

WASTE PILE (see Landfill)
_1_

 3
 *Lacking contrary evidence, covering soils are assumed to be
  Uncontaminated.  Soil cover contaminants must be attributable to
  the underlying waste materials and gaseous in origin.
**USGS soil types GC, ML, CL, and CH.  Source:  Adapted from
  Lutton, R. J., Evaluating Cover Systems for Solid and Hazardous
  Wastes, (EPA-530/SW-867c), U.S. Environmental Protection Agency,
  Washington, DC, September 1980.

                                 240

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                        TABLE D-4  (Concluded)
WET SURFACE IMPOUNDMENTS

  WSI01G    Wet enclosed* impoundment; Impoundment totally      	0_
              covered with a maintained, essentially
              impermeable cover
  WSI02G    Wet enclosed impoundment; impoundment totally       	1_
              covered with an unmaintained, essentially
              impermeable cover
  WSI03G    Wet enclosed impoundment; impoundment partially     	1_
              covered with a maintained, essentially
              impermeable cover
  WSI04G    Wet enclosed impoundment; impoundment partially     	2_
              covered with an unmaintained, essentially
              impermeable cover
  WSI05G    Wet enclosed impoundment; uncovered, surface        	3_
              completely open to atmosphere
  WSI06G    Wet nonenclosed impoundment; impoundment            	0_
              totally covered with a maintained, essentially
              impermeable cover
  WSI07G    Wet nonenclosed impoundment; impoundment            	1_
              totally covered with an unmaintained, essentially
              impermeable cover
  WSI08G    Wet nonenclosed impoundment; impoundment            	2_
              partially covered with a maintained, essentially
              impermeable cover
  WSI09G    Wet nonenclosed impoundment; impoundment            	3_
              partially covered with an unmaintained,
              essentially impermeable cover
  WSI10G    Wet nonenclosed impoundment; uncovered, surface     	3_
              completely open to atmosphere
  WSI11G    Other                                                 1
*An enclosed impoundment is one with a freeboard exceeding two feet
 in height or one that is substantially surrounded by a wall, fence,
 trees, or other adequate windbreak.
                                 241

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                              TABLE D-5

              OPTION 1A PARTICULATE CONTAINMENT FACTORS
              (CHOOSE CHARACTERISTIC THAT BEST  APPLIES)
ACTIVE FIRE SITE (AFSOl)

BELOWGROUND/BURIED CONTAINERS (see Landfill)

CONTAINERS (Intact Exposed/Aboveground Containers and
              Nonlntact Exposed/Aboveground Containers)

  C001P     Intact, sealed containers protected from the
              weather by a maintained cover
  C002P     Intact, sealed containers not protected from
              the weather by a maintained cover
  C003P     Open, unsealed, or nonlntact containers; waste
              totally covered with an essentially Impermeable,
              maintained cover
  C004P     Open, unsealed, or nonlntact containers; waste
              partially covered with an essentially
              impermeable, maintained cover
  C005P     Open, unsealed, or nonintact containers; waste
              totally covered with an essentially
              impermeable, unmalntained cover
  C006P     Open, unsealed, or nonintact containers;
              waste otherwise covered or uncovered
  C007P     Other

CONTAMINATED SOIL (see Landfill)

DRY SURFACE IMPOUNDMENT (see Landfill)

EMISSION SOURCES NOT ELSEWHERE SPECIFIED

  NES01P    Totally covered with a maintained covered
  NES02P    Partially covered with a maintained covered
  NES03P    Totally covered with an unmaintalned covered
  NES04P    Partially covered with an unmaintained covered
  NES05P    Uncovered
  NES06P    Other

INACTIVE FIRE SITE (see Landfill)

LANDFARM (see Landfill)
                                 242

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                        TABLE D-5 (Continued)
 LANDFILL

  LF01P      Site covered with an essentially impermeable
               and maintained cover or heavily vegetated
               with no  exposed soil or waste-bearing liquids
               (e.g., paved-over)
  LF02P      Site substantially vegetated or totally covered
               with a maintained nonwater-based dust
               suppressing fluid.  Little exposed soil or
               waste-bearing liquids.
  LF03P      Site lightly vegetated or partially covered
               with a maintained nonwater-based dust
               suppressing fluid.  Much exposed soil or
               waste-bearing liquids.
  LP04P      Site substantially devoid of vegetation with
               a large  percentage of exposed soil or
               waste-bearing liquids.  No other cover.
               Facility slope less than 10 degrees or unknown
  LF05P      Site substantially devoid of vegetation with
               a large  percentage of exposed soil or
               waste-bearing liquids.  No other cover.
               Facility slope greater than 10 degrees
  LF06P      Totally enclosed in a structurally intact
               building
  LF07P      Partially  enclosed in a structurally intact
               building
  LF08P      Totally enclosed in an nonintact building
  LF09P      Partially  enclosed in an nonintact building
  LF10P      Substantially surrounded with windbreak
               (e.g., mesh or other fence, trees,  etc.)
  LF11P     Active fire site
  LF12P     Other

WASTE PILE (see Landfill)

WET SURFACE IMPOUNDMENTS

  WSI01P    Enclosed* impoundment;  impoundment totally
               covered with a maintained cover
  WSI02P    Enclosed impoundment;  impoundment totally
               covered with an unmaintained cover
JL_

 2
 3
 1
 0
-^—-,

 1
*An enclosed impoundment is one with a freeboard exceeding two feet
 in height or one that is substantially surrounded by a wall  fence
 trees, or other adequate windbreak.                               '
                                 243

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                        TABLE D-5  (Concluded)
WET SURFACE IMPOUNDMENTS (Concluded)

  WSI03P    Enclosed Impoundment; Impoundment partially
              covered with a maintained cover
  WSI04P    Enclosed Impoundment; Impoundment partially
              covered with an unmalntalned cover
  WSI05P    Enclosed Impoundment; uncovered, surface
              completely open to atmosphere
  WSI06P    Nonenclosed Impoundment; Impoundment totally
              covered with a maintained cover
  WSI07P    Nonenclosed impoundment; Impoundment totally
              covered with an unmaintained cover
  WSI08P    Nonenclosed impoundment; Impoundment partially
              covered with a maintained cover
  WSI09P    Nonenclosed impoundment; impoundment partially
              covered with an unmaintained cover
  WSI10P    Nonenclosed impoundment; uncovered,  surface
              completely open to atmosphere
  WSI11P    Other
J

 3
                                244

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                              TABLE D-6

                  OPTION 1A GAS  CONTAINMENT  FACTORS
              (CHOOSE CHARACTERISTIC THAT BEST APPLIES)
ACTIVE FIRE SITE

  AFS01G    Active aboveground fire site                        	;

  AFS02G    Active belowground fire site: uncontaminated*       	J
              soil cover in excess of two feet
  AFS03G    Active belowground fire site: uncontaminated*       	\
              soil cover less than two feet, soil resistant
              to gas migration**
  AFS04G    Active belowground fire site: uncontaminated*       	'.
              soil cover less than two feet, soil not
              resistant to gas migration**

BELOWGROUND/BURIED CONTAINERS (see Landfill)

CONTAINERS  (Intact Exposed/Aboveground Containers and
            Nonintact Exposed/Aboveground Containers)

  C001G     Intact, sealed containers protected from            	C
              the weather by a maintained cover
  C002G     Intact, sealed containers not protected             	J
              from the weather by a maintained cover
  C003G     Open, unsealed, or nonintact container;             	(
              waste totally covered with an essentially
              impermeable, maintained cover
  C004G     Open, unsealed, or nonintact container;             	J
              waste partially covered with an essentially
              impermeable, maintained cover
  C005G     Open, unsealed, or nonintact container;             	/
              waste totally covered with an essentially
              impermeable, unmaintained covet
  C006G     Open, unsealed, or nonintact container;               ',
              waste otherwise covered or uncovered
  C007G     Aboveground containers; other                         ;


 *Lacking contrary evidence, covering soils are assumed to be
  uncontaminated.  Soil cover contaminants must be attributable to
  the underlying waste materials and gaseous in origin.
**USGS soil types GC, ML, CL, and CH.  Source:  Adapted from
  Lutton, R. J., Evaluating Cover Systems for Solid and Hazardous
  Wastes, (EPA-530/SW-867c), U.S. Environmental Protection Agency,
  Washington, DC, September 1980.
                                 245

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                        TABLE D-6  (Continued)

CONTAMINATED SOIL (see Landfill)

DRY SURFACE IMPOUNDMENTS (see Landfill)

EMISSION SOURCES NOT ELSEWHERE SPECIFIED

  NES01G    Totally covered with a maintained covered
  NES02G    Partially covered with a maintained covered
  NES03G    Totally covered with an unmaintained covered
  NES04G    Partially covered with an unmaintained covered
  NES05G    Uncovered
  NES06G    Other

INACTIVE FIRE SITE (see Landfill)

LANDFARM (see Landfill)

LANDFILL

  LF01G     Functioning gas collection system
  LF02G     Existing, nonfunctioning gas collection system
  LF03G     Intact synthetic cover plus uncontaminated soil
              cover over 0.5 inches in depth*
  LF04G     Totally covered with an intact synthetic
              cover; surface soil contaminated*
  LFO.DG     Totally covered with a nonintact synthetic
              cover; surface soil contaminated*
  LF06G     Uncontaminated soil cover* in excess of six
              inches
  LF07G     Uncontaminated soil cover* greater than one
              inch and less than six inches; cover soil
              resistant to gas migration**
  LF08G     Uncontaminated soil cover* less than six inches;
              cover soil type unknown
  LF09G     Uncontaminated soil cover* greater than one
              inch and less than six inches; cover soil not
              resistant to gas migration**
  *Lack.ing contrary evidence, covering soils are assumed to be
  uncontaminated.  Soil cover contaminants must be attributable to
  the underlying waste materials and gaseous in origin.
**USGS soil types GC, ML, CL, and CH.  Source:  Adapted from
  Lutton, R. J., Evaluating Cover Systems for Solid and Hazardous
  Wastes, (EPA-530/SW-867c), U.S. Environmental Protection Agency,
  Washington, DC, September 1980.

                                 246

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                        TABLE D-6  (Continued)
LANDFILL (Concluded)

  LF10G     Uncontaminated soil cover* less than one inch;
              cover soil resistant to gas migration**
  LF11G     Uncontaminated soil cover* less than one inch;
              cover soil not resistant to gas migration**
  LF12G     Covering soil contaminated* with waste
              contaminants at surface and no synthetic cover
              between surface and bulk of waste materials
  LF13G     Totally enclosed in a structurally intact
              building
  LF14G     Totally enclosed in an nonintact building
  LF15G     Waste uncovered or exposed
  LF16G     Other

WASTE PILE (see Landfill)

WET SURFACE IMPOUNDMENTS

  WSI01G    Wet enclosed*** impoundment; impoundment
              totally covered with a maintained, essentially
              impermeable cover
  WSI02G    Wet enclosed impoundment; impoundment totally
              covered with an unmaintained, essentially
              impermeable cover
  WSI03G    Wet enclosed impoundment; impoundment partially
              covered with a maintained, essentially
              impermeable cover
  WSI04G    Wet enclosed impoundment; impoundment partially
              covered with an unmaintained, essentially
              impermeable cover
  *Lacking contrary evidence, covering soils are assumed to be
   Uncontaminated.  Soil cover contaminants must be attributable to
   the underlying waste materials and gaseous in origin.
 **USGS soil types GC, ML, CL, and CH.  Source:  Adapted from
   Lutton, R. J., Evaluating Cover Systems for Solid and Hazardous
   Wastes, (EPA-530/SW-S67c), U.S. Environmental Protection Agency,
   Washington, DC, September 1980.
***An enclosed impoundment is one with a freeboard exceeding two feet
   in height or one that is substantially surrounded by a wall,
   fence, trees, or o trier adequate windbreak.
                                 247

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                        TABLE D-6  (Concluded)
WET SURFACE IMPOUNDMENTS (Concluded)

  WSI05G    Wet enclosed impoundment; uncovered, surface        	3_
              completely open to atmosphere
  WSI06G    Wet nonenclosed impoundment;  impoundment            	0_
              totally covered with a maintained, essentially
              impermeable cover
  WSI07G    Wet nonenclosed impoundment;  Impoundment            	1_
              totally covered with an unmalntained,
              essentially impermeable cover
  WSI08G    Wet nonenclosed impoundment;  impoundment            	2_
              partially covered with a maintained,
              essentially impermeable cover
  WSI09G    Wet nonenclosed impoundment;  impoundment              3
              partially covered with an unmaintained,
              essentially impermeable cover
  WS110G    Wet nonenclosed Impoundment;  uncovered,             	3_
              surface completely open to  atmosphere
  WSI11G    Other                                                 1
                                248

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