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Review Draft—Do Not Cite or Quote—December 1994 United States Environmental Protection Agency Office of Solid Waste and Emergency Response 9355.-4-14PS EPA/540/R-94/101 PB95-963529 December 1994 &ERr\ Soil Screening Guidance Office of Emergency and Remedial Response Hazardous Site Control Division Quick Reference Fact Sheet NOTICE: This document is draft for review only and should not be used until the guidance is finalzed following pubic comment and peer review BACKGROUND On June 19,1991, the U.S. Environmental Protection Agency's (EPA's) Administrator charged the Office of Solid Waste and Emergency Response (OSWER) with conducting a 30-day study to outline options for accelerating the rate of cleanups at National Priorities List (NPL) sites. One of the specific proposals of the study was for OSWER to "examine the means to develop standards or guidelines for contaminated soils." On June 23,1993, EPA announced the development of "Soil Trigger Levels" as one of the Administrative Improvements to the Superfund program. On September 30,1993, a draft fact sheet was released that presented generic Soil Screening Levels (SSLs) for 30 chemicals. The fact sheet presented standard- ized equations to model exposures to soil contaminants via ingestion, inhalation, and migration to ground water. The fact sheet provided generic defaults for each parameter in me equa- tions and a sampling inethodology to measure soil contaminant levels. The SSL initiative underwent widespread review both within and outside the Agency. Suggestions were made on bow to improve the methodology and increase the usefulness of screening levels by finding simple ways to modify them using site-specific data. Based on mat review, EPA modified the SSLs into a Soil Screening framework that emphasizes the application of standardized equations for the site-specific evaluation of soil contaminants. This framework provides an overall approach for developing SSLs for specific contaminants and exposure pathways at a site under a residential land use scenario. Areas with soil contaminant concentrations below SSLs generally would not warrant former Andy or action under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). The Soil Screening framework's point of departure is a simple methodology for calculating site-specific SSLs using easily obtained site data with standardized equations. An option for conducting a more detailed she-specific analysis is also included in the framework. In addition, default parameters are used in the standardized equations to produce a table of generic Soil Screening Levels for 107 chemicals that update those presented in the September 30, 1993, draft SSL fact sheet These generic SSLs are included in the framework as a default option for use when site-specific values are not available. PURPOSE OF SOIL SCREENING FRAMEWORK The Soil Screening framework represents the first of several tools EPA plans to develop to standardize the evaluation and cleanup of contaminated soils. SSLs streamline the remedial investigation/feasibility study (RI/FS) process by accelerating and increasing consistency in decisions concerning soil contamination. As a future companion to the Soil Screening framework, EPA also intends to develop a methodology to identify levels of contamination mat clearly warrant a response action or, possibly, concentrations for which treatment would be required. The screening levels at the low end and the higher concentration values that warrant response can be used to identify the bounds of a risk management continuum (Figure 1). Generally, within mis continuum lies a range of possible cleanup levels that will continue to be determined on a she- specific basis. EPA anticipates the use of the Soil Screening framework as a tool to facilitate prompt identification of the contaminants and exposure areas of concern during both remedial actions and some removal actions under CERCLA. SSLs do not nigger Nofurtheratudy Site specific warranted under cleanup CERCLA goaMevel action dearly -t- •Zero' eonoentation Screening Reeponse Very high sneentration Figure 1. Risk management spectrum for contaminated soil. TUT OO8 1O11 *65065* 65065 Review Draft—Do Not Cite or Quote—December 1994 die need for response actions or define "unacceptable" levels of contaminants in soil. SSLs may serve as Preliminary Remediation Goals (PRGs) under certain conditions (see section on Use of SSLs as Preliminary Remediation Goals/Cfeannp Levels). In die future, EPA win consider expanding the guidance to address the Resource Conservation and Recovery Act (RCRA) Corrective Action program. The SSLs are, as noted above, intended for use as a tool; men- use is not mandatory at sites being addressed under CERCLA. Toe framework leaves a broad range of discretion to the site manager, both on whether the SSL approach is appropriate for a site and, if it is used, on the appropriate method. This guidance anticipates three optional approaches—simple site- specific, detailed site-specific, and generic. In the first two, some or all default values would be replaced as appropriate with site-specific data. Furthermore, the models themselves are not codified as rules and can be modified if appropriate, although some explanation should be provided if such modification is made. SOIL SCREENING FRAMEWORK A Soil Screening Level is a chemical concentration in soil mat represents a level of contamination below which there is no concern under CERCLA, provided conditions associated with the SSLs are met Generally, if contaminant concentrations in soil fall below the SSL, and there are no significant ecological receptors of concern, then no further study or action is warranted for residential use of that area. (Some States have developed screening numbers mat are more stringent than die generic SSLs presented in mis fact sheet; therefore further study may be warranted under State programs.) Concentra- tions in sofl above either die generic or site-specific screening level would not automatically designate a site as "dirty" or trigger a response action. However, exceeding a screening level suggests that a further evaluation of die potential risks dial may be posed by she contaminants is appropriate to determine die need for a response action. The Soil Screening framework presents dtree approaches for establishing screening levels. The option emphasized in this Fact Sheet is a simple method that incorporates readily obtain- able, site-specific data into standardized equations to derive site-specific screening levels for selected contaminants. When questions still exist at a sue regarding whether or not contam- inant levels are of concern, as a second approach, more tailored screening levels can be derived for most contaminants by incorporating additional site data into more complex fate and transport models. The mird approach is to apply die generic SSLs presented in Appendix A. Although die default parameters used to derive die generic SSLs are not necessarily "worst case," tiiey are conservative. The progression from generic to simple site-specific and detailed (full-scale) site-specific SSLs usually will involve an increase in investigation costs and a decrease in conservatism (Figure 2). Generally, die decision of which method to use More Conservatism Less Generic SSL Less Simple Site-Specific Method <« Investigation Costs Detailed Site- Specific Method More Figured Components of the Soil Screening framework. involves balancing die increased investigation costs with die potential savings associated with higher (but protective) SSLs. Therefore, die framework promotes the option of using site- specific data to derive screening levels. More guidance regarding which option to use is presented later in this fact sheet Site-Specific SSLs: Simple Method The simple method for developing site-specific SSLs requires die collection of a small number of easily obtained site parameters (e.g., fraction organic carbon, percent.soil moisture, and dry bulk density) for use in die standardized equations so diat die calculated screening levels can be appropriately con- servative for die site but not as conservative as the generic values. Once derived, die user then compares measured site or area contaminant concentrations to die she-specific screening levels. If concentrations do not exceed die SSLs for each pathway of concern, it would generally be appropriate to exclude die area from further investigation. If die levels are exceeded, die site manager may decide tiiat a more comprehensive evaluation is needed to determine die risk posed via a particular exposure pathway (see Technical Background section). Site-Specific SSLs: Detailed Approach A more detailed method for developing she-specific SSLs is a full-scale model evaluation requiring die collection of addi- tional site data. Full-scale modeling allows die application of complex transport and fate models and allows for consideration of a finite contaminant source. Applying these models wfll further define die risk associated with exposure via die inhalation or migration to ground water pathway. The model application may snow that tiiere is no concern over exposure from die pathway, thereby eliminating it from further concern. This potential outcome provides die incentive for incurring the cost and time to conduct a comprehensive she evaluation. TUT 008 1012 Review Draft—Do Not Cite or Quote—December 1994 Generic SSLs Generic SSLs can be used in place of site-specific screening levels. The decision to use generic SSLs will likely be driven by time and cost The site manager most weigh die cost of conducting a more site-specific investigation with the potential for deriving a higher SSL that provides for an appropriate level of protection. The Technical Background section of this guidance presents a more detailed discussion of the level of effort required to conduct further study of site conditions and risks. Appendix A provides generic SSLs for 107 chemicals. SCOPE OF SOIL SCREENING FRAMEWORK The Soil Screening framework has been developed for 107 chemicals using assumptions for residential land use activities for three pathways of exposure (see Figure 3): • Ingestion of soil • Inhalation of volatites and fugitive dusts • Ingestion of contaminated ground water caused by migra- tion of chemicals through soil to an underlying potable aquifer. Reviews of risk assessments at hazardous waste sites indicate that these pathways are the most common routes of human exposure to contaminants in the residential setting. These are also the pathways for which generally accepted methods, models, and assumptions have been developed that lend themselves to a standardized approach. Data on dermal exposures have also been considered, and the generic SSL for Direct Ingestion of Ground Water and Soil Inhalation Blowing Dust and Volatilization Highlight 1: Kty Attribute of (n* SSL Frmvwork • Standardized equations are presented to address three individual human exposure pathways. • Parameters are identified for which site-specific information is needed to develop site-specific SSLs. • Default values are provided and used to calculate generic SSLs that are consistent with Superfund's concept of •Reasonable Maximum Exposure' (RME). • SSLs are generally based on a 10* risk for carcinogens, or a hazard quotient of 1 for noncar- dnogens. SSLs for migration to ground water are based on nonzero maximum contaminant level goals (MCLGs), or, when not avaflable, maximum contami- nant levels (MCLs). Where neither of these are avaBabte, the aforementioned risk-based targets are used. pentachlorophenol has been modified accordingly. The scope of the SSL framework is limited to human exposure via the pathways listed above; therefore, sites with other significant exposure pathways, nonraidential land uses, possible ecological concerns, or unusual site conditions should consider their associated risks on a site-specific basis apart from the SSL framework. Key attributes of the Soil Screening framework are given in Highlight 1. Soil Ingestion Pathway For the direct soil ingestion pathway, only generic SSLs were developed. Simple and full-scale site-specific methods were not developed because cost and complexity make developing site-specific data for this pathway, such as soil ingestion rates or chemical-specific bioavailability, generally impracticable. However, EPA is evaluating the data available to support adjustment of the exposure frequency term based on regional climatic conditions. Inhalation Pathway For inhalation of volatiles and fugitive dust, both generic values and a method for incorporating site-specific data into the standardized equations have been developed. To estimate the site-specific potential for volatilization of contaminants, soil conditions such as fraction organic carbon, soil moisture content, and dry bulk density must be evaluated. To estimate the site-specific potential for generation of fugitive dusts, other meters must be evaluated, such as mean annual windspeed. Figures. Exposure pathways addressed by the Soil Screening framework. threshold friction velocity, and the mode soil aggregate size to further tailor die SSLs to the site. For both the inhalation of volatiles and fugitive dust pathways, a site-specific determination of the area of contamination and meteorologic inputs ny be incorporated into dispersion calculations. TUT oo Review Draft—Do Not Cite or Quote—December 1994 Migration to Ground Water The simple site-specific method for addressing potential contaminant migration to groomd water uses the same soil parameters required to address •volatilisation, along wim easily obtainable hydrogeologic parameters. The simple site-specific method for this exposure pathway also requires a determination of the area of contamination. Other Pathways Additional exposure pathways to contaminants in soil—dermal absorption, plant uptake, and migration of volatiles into basements—may contribute significantly to the risk to human health in a residential setting. The Superfund program has evaluated the data and methods available to address these potential exposures and has incorporated as much information as possible into the SSL framework. Based on limited empirical data, me ingestion SSL for r^ntachlorophenol has been adjusted to account for potential dermal exposure. Additionally, empirical data indicate mat plant uptake may be important for some chemicals (ie., As, Cd, Hg, Ni, Se, Zn). The fact that these chemicals1 potential for plant uptake and dermal absorption has been noted in Appendix A should not be misinterpreted to mean that other chemicals are not of potential concern for dermal exposure or plant uptake. As additional information becomes available, other chemicals may be addressed as well At this time, Superfund does not believe that die potential for migration of contaminants into basements can be reasonably incorporated into the SSL framework. The parameters required for the models (e.g., the number and size of cracks in basement walls) do not lend themselves to standardization or to evaluation of potential future exposure, and the models have not been adequately validated. The Technical Background Document (ILS. EPA, 1994e) provides a detailed analysis of available modeling of this pathway. Other Land Uses Longer-term efforts will be required to develop standardized tools to address exposures relevant to other land uses such as industrial land use. The results of these efforts may be included in future revisions of mis guidance. Ecological Receptors As part of the baseline risk; art, an ecological assess- ment should be conducted at every Superfund site. The SSL framework does not attempt to define significant ecological receptors or quantify ecological risks. However, a comparable list of screening level benchmarks, called Ecotox Thresholds, is being developed by Office of Emergency and Remedial Response (OERR) for application daring the ecological risk assessment addressed in OSWER Directive No. 9285.7-17 (U.S. EPA, 1994d). These values are defined as media- specifk chemical concentrations above which mere is sufficient concern regarding adverse effects to ecological receptors to warrant farther site investigation. OERR is developing fHkSance t» designing and conducting ecological risk assessments mat will describe the use of such screening values in the Superfund Remedial Investigation process. HOW TO USE THE SOIL SCREENING FRAMEWORK The decision to use the Soil Screening framework at a site will be driven by the potential benefits of eliminating areas, exposure pathways, or contaminants from further investigation. By identifying areas where concentrations of contaminated soil are below levels of concern under CERCLA, the framework provides a means to focus resources on exposure areas, contaminants, and exposure pathways of concern. Highlight 2 outlines the process of applying the Soil Screening framework at a site. To enable early comparison with site background concentrations and to provide information necessary for determining an adequate sample size, site- specific SSLs should be developed as early in the process as possible. They can be adjusted during the process to accommodate additional site information and the resulting changes to the conceptual site model Developing a Conceptual Site Model The primary condition for use of SSLs is mat exposure path- ways of concern and conditions at the site match those taken into account by the Soil Screening framework. Thus, at all sites it will be necessary to develop a conceptual site model to identify likely contaminant source areas, exposure pathways, and potential receptors. This information can be used to Highlight 2: Using the Soil Senaning FramewonV • Develop site conceptual model and compare with SSL conceptual model to determine applicability of framework. • Determine ff background contaminant concentrations are above generic SSLs. • Select approach (simple or detailed site-specific, generic) and develop SSLs. • Measure average soil contaminant concentrations in exposure areas (EAs) of concern. • Compare average soil concentrations with SSLs and eliminate site or area of site where EA mean concentration is less than SSL • Consider further study or use of SSLs as PRGs for sites or site areas with contaminant concentrations greater man SSLs. TUT 008 io14 Review Draft—Do Not Cite or Quote December 1994 determine die applicability of die framework at die site and die need for additional information. A conceptual site model is developed from available site sampling data, historical records, aerial photographs, and hydrogeologic information. The model establishes a hypothesis about possible contaminant sources, contaminant fate and transport, exposure pathways, and potential receptors. The DQO Guidance for Snperfund (U.S. EPA, 1993a) provides an excellent discussion on dte development of a conceptual site model The rationale for including die contaminant migration to ground water exposure pathway should be consistent with EPA ground water policy (U.S. EPA, 1988, 1990b, 1992a, 1992b, 1993b). The conceptual model upon which die generic SSLs are based is a 30-acre property that has been divided up for residential use. Thus, die generic SSLs have been developed to be protective for source areas up to 30 acres. The contamination is assumed to be evenly distributed across die area of concern and extends from die ground surface to die top of dte aquifer. The soil type is assumed to be loam mat has SO percent vegetative cover. Loam is soil widi approximately equal proportions of sand and silt Exposure to contaminants can occur via ingestion of soils, inhalation of volatile* and fugitive dusts, or migration to ground water. For the migration to ground water pathway, die point of compliance is assumed to be at die edge of die she, which is assumed to be homogeneously contaminated. No attenuation is considered in die unsaturated zone; however, dilution is assumed within dw aquifer to the point of compliance. Forme generic conceptual site model, die source is assumed to extend across die entire site. See Figures 3 and 4 for a graphic representation of aspects of the conceptual model applicable to die Soil Screening framework. Partitioning of contaminant mass between media is not addressed in die SSL framework because die fate and transport models used to derive die generic SSLs are based on die assumption of an infinite source. Although die assumption is highly conservative, a finite source model cannot be applied unless diere are accurate data regarding source size and volume. Obviously, in die case of toe generic SSLs, such data are not available. It is also unlikely diat such data will be available from die limited subsurface sampling tiiat is done to apply die simple site-specific method. Thus, it is most likely tiiat a finite source model would be applied as part of a detailed site-specific investigation. EPA will continue to seek consensus on die appropriate methods to incorporate contaminant partitioning and a finite source into die simple site-specific method. The results of these tidocu nay be included in future updates to tins guidance. The Technical Background Document (U.S. EPA, 1994e) presents information on equations and models tiiat can accommodate finite sources and predict die subsequent impact on either ambient air or ground water. However, when using PLAN VIEW SECTION VIEW Raowtor Land Surface Saturated Zoo* Default assumptions: • Infinite source • Source extends to water table » Well at downgradient edge of source • 30-acre source size Figure 4. Migration to ground water pathway— SSL conceptual model. a finite source model, the site manager should recognize the uncertainties inherent in site-specific estimates of subsurface contaminant distributions and use conservative estimates of source size and concentrations to allow for such uncertainties. The following questions should always be considered in die development of die conceptual site model before applying die Soil Screening framework: • Is die site adjacent to surface waterbodies where die potential for contamination of surface water by overland flow or release of contaminated ground water sVmV* be considered? Are thae potential or aqwatfr ecological Is fljere potential for land nse other than residential? Are there other likely human exposure pathways diat were not considered in development of die SSLs (e.g., local fish consumption; raising of beef, dairy, or other livestock)? Are there unusual site conditions (e.g., area of contamina- tion greater dan 30 acres, unusually high fugitive dust levels due to soil being tilled for agricultural use, or heavy traffic on unpaved roads)? TUT 008 1O1.5 Review Draft—Do Not Cite or Quote—December 1994 If the conceptual site model indicates thai residential assump- tions are appropriate for your site and no pathways of concern other than those covered by the Soil Screening framework are present, then the framework may be applied directly to the site. If the conceptual site model indicates that the site is more complex than the scenario outlined in this guidance, toe frame- work above will not be sufficient Additional pathways, recep- tors, or chemicals must be evaluated on a site-specific basis. Considering Background Contamination A necessary step in detaining the usefulness of the SSL framework is the consideration of background contaminant concentrations, since die framework wfll have little utility where background concentrations exceed the SSLs. EPA may be concerned with two types of background at sites: naturally occurring and anthropogenic. Natural background is usually limited to metals whereas anthropogenic (Le., human- mad^) background iricliKks both organk and irtorgank contam- inants. Generally, EPA does not clean up below natural background; however, where anthropogenic background levels exceed SSLs and EPA has determined that a response action is necessary and feasible, EPA's goal will be to develop a comprehensive response to die widespread contamination. This will often require coordination with different authorities that have jurisdiction over other sources of contamination in die area (such as a regional air board or RCRA program). This will help avoid response actions mat create "clean islands" amid widespread contamination. The background information and understanding of the site developed as part of die conceptual model can help determine background concentration. When considering background, one should also consider die bioavailabiliry and mobility of compounds. Some compounds may form complexes mat are immobile and unlikely to cause significant risk. This situation is more likely to occur with naturally occurring compounds. Therefore, background con- centrations of compounds exceeding die SSLs do not neces- sarily pose a threat Alternately, activities at a site can adversely affect the natural soil geochemistry, resulting in die mobilization of compounds. Consequently, background con- tamination should be considered carefully. Regardless, where background concentrations are higher than die SSLs, the SSLs generally will not be die best tool for site decisionmaking. Sampling Exposure Area After die conceptual site model has been developed, and die applicability of the Soil Screening framework is determined, die next step is to collect a representative sample set for each exposure area. An exposure area is defined as that geographic area in which an individual may be exposed to contamination over time. Because SSLs are developed for a residential scenario, EPA assumes die exposure area is a 03-acre residential lot In those situations where little or no sampling has been done, it will be beneficial to collect die site data required for die simple site-specific methodology in tandem with the collection of samples to identify contaminant concentrations. The site manager should work to Emit die total number of trips to die site by maximizing die usefulness of die samples collected. (See section on Measuring Contaminant Concentrations in Soil for additional guidance.) Comparing Exposure Area Concentration to SSLs The fourth step is to compare onsite soil contaminant concen- trations wim site-specific SSLs or die generic SSLs listed in Appendix A. At this point it is reasonable to review die conceptual site model with die actual site data in hand to reconfirm die accuracy of die conceptual site model and die applicability of die Soil Screening framework. Once this is confirmed, site contaminant levels may be compared with die SSLs. In Appendix A, die first column to die right of die chemical name presents levels based on direct ingesu'on of soil. The second column presents die levels based on inhalation of vola- tilesorsoilparticulates. The drird column presents SSL values for die migration to ground water pathway multiplied by a dilution and attenuation factor (DAF) of 10 to account for natural processes diat reduce contaminant concentrations in die subsurface. The fourth column contains die SSL multiplied by a DAF of 1, which may be appropriate to use in instances where there are high water tables, karst topography, fractured bedrock, or source size greater than 30 acres. The lowest SSL of die three pathways (ingestion, inhalation, and ground water with DAF of 10) is highlighted in bold for each contaminant Generally, die comparison of SSLs to site contaminant levels will result in one of three outcomes: 1. Site-measured values indicate diat an area falls below all of die SSLs. Soils from mese areas of die site generally can be eliminated from further evaluation under CERCLA. 2. Site-measured data indicate diat one or more SSLs have clearly been exceeded. In mis case, die SSLs have helped to identify site areas, contaminants, and exposure pathways of potential concern on which to focus further analysis or data-gathering efforts. 3. A site-measured value exceeds one pathway-specific value but not others. In tins case, it is reasonable to focus additional site-specific data collection efforts only on data diat win help determine whether diere is truly a risk posed via diat pathway or by a limited set of chemicals'at die site. When an exceedance is marginally significant a closer look at site-specific conditions and exposures may result in die area being eliminated from further study. TUT 1016 Review Draft—Do Not Cite or Quote—December 1994 Use of SSLs as Preliminary Remediation Goals/Cleanup Levels SSLs are not nationwide cleanup levels or standards. Where the basis for response action exists and aO exposure pathways of concern are addressed by the SSLs, the SSLs nay serve as FRGs as defined in HHEM, Part B (US. ERA, 19914). A PRO is a strictly risk-based value that serves as die point of departure for the establishment of site-specific cleanup levels. PRGs are modified to become final cleanup levels based on a consideration of the nine-criteria analysis described in the National Contingency Plan (NCP; Section 300.430 (3)(2) (iXA)), including cost, long-term effectiveness, and iraple- mentability. See Role of the Baseline Risk Assessment in Superfund Remedy Selection Decisions (US. EPA, I991e) for guidance on how to modify PRGs to generate cleanup levels. The SSLs should only be used as site-specific cleanup levels when a nine-criteria evaluation using the SSLs as PRGs for soils indicates mat a selected remedy achieving the SSLs is protective, ARAR-compliant, and appropriately balances the other criteria, including cost An example is a small site or exposure area where the cost of additional study would exceed the cost of remediating to the generic SSLs. Addressing Exposure to Multiple Chemicals The SSLs generally correspond to a 10"6 risk level for carcino- gens and a hazard quotient (HQ) of 1 for noncarcinogens. This "target" hazard quotient is used to calculate a soil concentration below which it is unlikely for even sensitive populations to experience adverse health effects. The potential for additive effects has not been "built in" to the SSLs through apportionment For carcinogens, EPA believes mat setting a MX* risk level for individual chemicals and pathways generally will lead to cumulative risks within the 1(P to 10* risk range for the combinations of chemicals typically found at Superfund sites. For noncarcinogens, mere is no widely accepted risk range. Thus, for developing national screening levels, options are either (1) to set the risk level far individual contaminants at the RfD or RfC 0.e., a hazard quotient of 1), or (2) to set chemical-specific concentrations by apportioning risk based on some arbitrarily chosen fraction of the acceptable risk level (e.g., one-fifth or one-tenth the RfD or RfC). The Agency believes, and EPA's Science Advisory Board agrees (US. EPA, 1993d), mat noncancer risks should be added only for those chemicals with the same toxic endpoint or mechanism of action. Highlight 3 lists the chemicals from Appendix A mat have SSLs based on noncarcinogenic toxkaty and affect the same target organ. If more man one chemical detected at a site affects the same target organ (Le., has the same critical effect as defined by the RfD methodology), site-specific SSLs for each chemical in the group should be divided by the number of chemicals present The concentration of contaniinants at the Highlights: SSL Chunk** with Noncarrtnogmic Toxic Effect* on Specific Target Organs Kidney Acetone 1,1-Dchbroethane Dimethyl phthaiate 2,6-Dtnftiotoluene Dwxwtyl phthaiate Nitrobenzene 2,4,5-Triditorophenol Vinyl acetate Liver Acetone Chbrobenzene Di-n-octyl phthaiate Nitrobenzene 2,4,5-Tfichtorophenol Central Nervous System Butanol 2,4-Dehtarophenol 2,4-Dinitrotoluene 2,6-Dhitrotoluene 2-Methyktnenol Circulatory System Antimony Barium p-Chbroaniline cls-1,2-Dichbroethyiene Nitrobenzene Zinc Reproductive System Carbon disutTide 2-Chtorophenol 1 &4-Tnchiorobenzene Gross Pathology Diethy! phthaiate 2-Metnyiphenot Naphthalene Nickel Vinyl acetate site should men be compared to the SSLs mat have been modified to account for this potential additivity. Because the combination of contaminants will vary from site to site, apportioning risk to account for potential additive effects could not be considered in the development of generic SSLs. Furthermore, for certain noncarcinogenic organics (e.g^ ethylbenzene, toluene), the generic SSLs are not based on toxkity but are determined instead by a "ceiling timit" concentration (C,*) at which these chemicals may occur as nonaqueous phase liquids (NAPLs) in soil (see Technical Background section). For these reasons, the potential for additive effects and the need to apportion risk must be a site- specific determination. TECHNICAL BACKGROUND The models and assumptions supporting the Soil Screening framework were developed to be consistent with Superfund's concept of "reasonable maximum exposure" (RME) in the residential setting. The Risk Assessment Guidance for Superfund, Volume 1 (OS. EPA, 1989b) and the Standard Default Exposure Factors guidance (US. EPA, 1991b) outlined the Superfund program's approach to calculating an RME. Since mat time, the Agency (U.S. EPA, 1991a) has coined a new term mat the Superfund program believes corresponds to the definition of RME: "high-end individual exposure." The Superfund program's method to estimate the RME for chronic exposures on a site-specific basis is to combine an average exposure point concentration with reasonably TUT OO8 1O17 Rtvww Draft—Do Not CH» or Quote—December 1994 conservative values for intake and duration in the exposure calculations. The default intake and dotation assumptions are presented in the Standard Default Exposure Factors guidance (U.S. EPA, 1991b). The duration assumptions were chosen to represent individuals living in a small town or other nontransient community. (Exposure to members of a more transient community is assumed to be shorter and thus associated with lower risk.) Exposure point concentrations are either measured at the site (e.g., ground water concentrations at a receptor well) or estimated using exposure models with site-specific model inputs. An average concentration term is used in most assessments where the focus is on estimating long-term, chrome exposures. Where the potential for acute tenacity is of concern, exposure estimates based on maximum concentrations may be more appropriate. The resulting site-specific estimate of RME is then compared with chemical-specific toxicity criteria such as RfDs or RfCs. EPA recommends using criteria from the Integrated Risk Information System (IRIS) (US. EPA, 1994c) and Health Effects Assessment Summary Tables (HEAST) (U.S. EPA, 1993c), although values from other sources may be used in appropriate cases. •^ The Soil Screening framework differs from a site-specific estimate of risk in that the exposure equations and models are run in reverse to backcakulate to an "acceptable level" of contaminant in soil Toxicity criteria are used to define the acceptable level: a level corresponding to a 10"* risk for carcinogens and a hazard quotient of 1 for noncarcinogens. The concept of backcalculating to an acceptable level in soil was presented in RAGS Pan B (U.S. EPA, 1991d), and the Soil Screening framework serves to update Part B for addressing residential soils. Site-specific SSLs are consistent with the Superfund approach to estimating RME on a site- specific basis. Standard default factors are used for the intake and duration assumptions, site-specific inputs are used in the exposure models, and chemical-specific concentrations averaged over die exposure area are used for comparison to the SSLs. Consistent with the site-specific SSLs, the generic SSLs use the same intake and dotation assumptions and are compared to area average concentrations. However, me generic SSLs are based on a hypothetical site model In developing the parameters for the hypothetical site, the Superfund program considered the conservatism inherent in the exposure models (e.g., assumption of an infinite source) and men combined high-end and central tendency parameters for size, location, and soil characteristics. The resulting generic SSLs should be protective for most site conditions across the Nation. OERR performed a sensitivity analysis to determine which parameters most influenced the output of the volatilization and fugitive dust models used to c^cu^tr- SSLs for the inhalation pathway. For fugitive dusts, the particulate emission factor (PEF) was most sensitive to threshold friction velocity, which was set at a "high-end" value. For calculation of the volatilization factor (VF)» soil moisture content was set at a conservative value because it drives the air-filled soil porosity mat in turn provides the pathway for chemicals to volatilize from soils. Gdmatic conditions have a significant impact on dispersion of both volatile and particulate emissions and were set at high-end values to be protective for conditions at most sites. Different high-end meteorological data sets were selected to calculate 90th percentile dispersion coefficients for the VF and for the PEF. For the migration of contaminants from soils to ground water, only average soil conditions are used to calculate generic SSLs because of the conservatism inherent in the partition equation. The generic DAF for this pathway was developed using a weight of evidence approach to be protective under most hydrogeologic conditions across the country as described in the following section on the migration to ground water. Characteristics of the generic, hypothetical site used to develop generic SSLs were described previously in the section discussing the conceptual site model. The Technical Background Document (ILS. EPA, 1994e) accompanying this guidance describes the pathway-specific equations, assumptions, and methodology mat form the basis for both the simple site-specific approach and the generic SSLs. The Technical Background Document also describes development of the specific default input values used to calculate generic SSLs for the inhalation and migration to ground water pathways. The generic SSLs are based on default assumptions. EPA recognizes mat site-specific conditions may differ significantly from these default assumptions. The Soil Screening framework emphasizes the substitution of some of the generic fate and transport assumptions with site-specific data to derive site-specific SSLs. However, one purpose of the SSLs is to define a level in soil below which no farmer study or action would be required. Therefore, alternative levels that are set using site-specific data should generally be calculated assuming the RMEThigh-end" individual exposure. The following sections present the standardized equations and default assumptions mat form the basis for the simple site- specific methodology and the generic SSLs. The soil ingestion discussion is limited to default assumptions because only generic SSLs have been developed for mis pathway. Direct Ingestion Agency toxicity criteria for noncarcinogens establish a level of daily exposure that is not expected to cause deleterious effects over a lifetime (Le., 70 years). Depending on the contaminant, however, exceeding the RfD (Le^ the "acceptable" daily level) for a short period of time may be cause for concern. For example, if mere is reason to believe that exposure to soil may be higher at a particular stage of an individual's lifetime, one would need to protect for that shorter period of high exposure Because a number of studies have shown mat inadverten. TUT 008 1018 Review Draft-Do Not Cite or Quote—December 1994 ingestion of soil is common among children age 6 and younger (Calabrese et ah, 1989; Davis et al, 1990; Van Wijnen et al., 1990), the SSLs in the default option are set at concentrations that are protective of mis increased exposure during childhood by ensuring that the chronic reference dose (or RfD) is not exceeded during this shorter (6-year) time period (Equation 1). If mere is reason to believe that exposures at a site may be significant over a short period of time (e.g^ extensive soil excavation work in a dry region), depending on the contami- nant, the site manager should consider the potential tor acute health effects as well. Equation 1: Screening Level Equation for Ingestlon of Noncarcinogenic Contaminants In Residential Soil s^r^jlf^f-fl^fl}- ,„, ,!**? ,* BW x AT x 36S d/yr 1/WDC x 10-6 kg/ing x EF x ED x IR Parameter/Definition (unite) THQ/target hazard quotient (urutiess) BW/body weight (kg) AT/averaging time (yr) Rf D0 /oral reference dose (mg/kg-d) EF/exposure frequency (dtyr) ED/exposure duration (yr) IR/soU ingestion rate (mg/d) Default 1 15 e» chemical-specffic 350 6 200 * For noncereinogens, avenging time i* equal to exposure duration. In some cases, children may ingest large amounts of soil (Le., 3 to 5 grams) in a single event This behavior, known as pica, may result in relatively high short-term exposures to contaminants in soils. Such exposures may be of concern for contaminants that primarily exhibit acute health effects. Review of clinical reports on contaminants addressed in tins guidance suggests that acute effects of cyanide and phenol may be of concern in children exhibiting pica behavior. If soils containing cyanide and phenol are of concern and pica behavior is expected at a site, the protectiveness of the ingestkm SSLs for these chemicals should be reconsidered. For carcinogens, both the magnitude and duration of exposure are important Duration is critical because the toxicity criteria are based on "lifetime average daily dose." Therefore, me total dose received, whether it be over 5 years or 50 years, is averaged over a lifetime of 70 years. To be protective of exposures to carcinogens in the residential setting, OERR focuses on exposures to individuals who may live in the same residence for a "high-end" period of time (Le., 30 years). As mentioned previously, exposure to soil is higher during childhood and decreases with age. Thus, Equation 2 uses a time-weighted average soil ingestion rate for children and adults. The derivation of mis time-weighted average is presented in U.S. EPA (1991d). Equation 2: Screening Level Equation for Ingestlon of Carcinogenic Contaminants In Residential Soli Screening Level _ TR x AT x 366 oVyr (ing/Kg) SF0 x 10"* kg/mg x EF x IF^^ Parameter/Definition (unite) TR/target cancer risk (unitless) AT/averaging time (yr) SF0 /oral slope factor (mg/kg-d)"1 EF/exposure frequency (d/yr) IFi0l^ /age-adjusted soil ingestion factor (mg-yr/kg-d) Default 10-6 70 chemical-specific 350 114 Inhalation of Volatiles and Fugitive Dusts Agency toxicity data indicate that risks from exposure to some chemicals via inhalation far outweigh the risks via ingestion. The models and assumptions «sed to calculate SSLs for inhalation of volatiks and fugitive dusts are updates of the equations presented in U.S. EPA's HHEM Part B guidance (U.S. EPA, 1991d). The volatilization factor (VF), soil saturation limit (C^, particulate emission factor (PEF% and dispersion model have all been revised. Another change from me Part B methodology is the separation of the ingestion and inhalation pathways. Toxicity criteria for oral exposures are presented as administered doses in units of milligrams per kilograms per day (mg/kg-d); whereas, the inhalation criteria are presented as concentrations in air (ug/m3 or mg/m3) that require conversion to an estimate of internal dose to be comparable to the oral route. EPA's Office of Research and Development (ORD) now believes mat the conversion from concentration in air to internal dose is not always appropriate and suggests evaluating these exposure routes separately. As explained in HHEM Part B, the basic principle of the volatilization model is applicable only if the soil concentration is at or below soil saturation (C.J. Above mis level the model cannot predict an accurate VF. C— is me concentration at which soil air, pore water, and sorption sites are saturated and above which free-phase contaminants may be present For compounds mat are liquid at ambient soil temperatures, C^ indicates a concentration above which NAPLs may be suspected in site soils and further investigation may be necessary. Thus, for liquid compounds for which the SSL exceeds C^,, the SSL is set at CM. For compounds that are solid at soil temperatures for which the SSL exceeds C^, volatile emissions can be assumed to be of no concern and the SSL is calculated considering particulate emissions only the 1/VF term in Equation 3 or 4 is set to zero). TUT 008 1019 Review Draft—Do Not Cite or Quote-December 1994 Equation 3: Screening Level Equation for Inhalation of Carcinogenic Contaminants In Residential Soil Screening Level TR x AT x i URFxIOOO x EF x ED x • Parameter/Definition (units) TR/target cancer risk (unfttess) AT/averaging time (yr) URF/inhaiation unit risk factor (ug/m3)-1 EF/exposure frequency (d/yr) ED/exposure duration (yr) VF/soiMo-air volatilization factor (ms/kg) PEF/particulate emission factor (m3/kg) Defautt 10* 70 chemical-specific 350 30 chemical-specific 6.79 x 10* Equation 4: Screening Level Equation for Inhalation of Noncardnogenic Contaminants In Residential Soli Screening Level (mgJkg) THQ x AT x 365 d/yr EF xED x P»rt /Definition (unit*) THQ/target hazard quotient (unittess) AT/averaging time (yr) EF/exposure frequency (d/yr) ED/exposure duration (yr) RfC/inhalat'on reference concentration (mg/m3) VF/soiMo-air volatifization factor (m'/kg) PEF/particulate emission factor (m3/kg) Default 1 30 350 30 chemical-specific chemical-specific 6.79 x 10* Equations 3 through 7 form (be basis for deriving both simple site-specific and generic SSLs for the inhalation pathway. The following parameters in the standardized equations can be replaced with specific site data to develop amore site-specific SSL: — Average soil moisture content — Average fraction organic carbon content — Dry soil bulk density Equation 5: Derivation of the Volatilization Factor VF (m3/kg) • <VC x (3-14 x a x T)1* x 10-»m2/fcn,2 (2 x D.J x 6. x KJ where 0,1X8. ° " «. * (p J (1 - Parameter/Definition (units) VF/volatilization factor (ms/kg) Ore/Inverse of the mean cone, at the center of a 30-acre-square source (g/m2-s per kg/m3) T/exposure interval (s) Drt /effective diffusivity (crr^/s) 8, /air-fifed soil porosity (1^,/L^g) 0,/dtffusivity in air (cms/s) n/total soil porosity VL^aJL^) w/average soil moisture content soil buk density (g/cm3) pt/soil particle density (g/cm3) K^, /soil-air partition coefficient (g-«oil/cm3-air) H/Henry's law constant (atm-mP/mol) K,, /soil-water partition coefficient (cm3/g) Koe/brganic carbon partition coefficient (orftg) f^/organic carbon content of sofl (g/g) Defautt 35.10 9.5 x 108 s 0.28 or n-wpb chemical-specific 0.43 (loam) 0.1 (10%) 1.5or(1-n)p, 2.65 (HVKd)x41 (41 is a conversion factor) chemical-specific chemical-speciric 0.006 (0.6%) Equation 6: Derivation of the Soil Saturation Umtt Parameter/Definition (units) CM^sofl saturation concentration (mg*g) S/sdubiftty in water (mg/L-water) Pi/dry soil buk density (kpA) nrtotal soil porosity (L-erX,,,) p./soil particle density (kg/L) KysoiNvater partition coemcwnt (Ukg) K^/soil organic carbon/water partition coefficient (Ukg) fa/fraction organic carbon of sol soil porosity 6, /air-fiHed sofl porosity (L»A»o«) w/average soil moisture content He/Henry's law constant (unitless) H/Henry's law constant (atm-m3/mol) Defautt chemical-specific 1.5or(1-n)p. 0.43 (toam) 2.65 ihemical-epecblc 0.006 (0.6%) wpbor0.15 n - wpb or 0^8 0.1 (10%) Hx 41, where 41 is a conversion factor chemical-specific 10 TUT .102O Review Draft—Do Net Cite or Quote—December 1994 Equation 7: Derivation of the Paniculate Emission Factor PPP^s/kjrt . cue v 3600s/r> 0.036 x (1-V) x (UJU,)3 x F(x) Parameter/Definition (unite) PEF/partieulate emission factor (m8/kg) CVC/lnverse of the mean cone, at the center of a 30-acre-square source (g/m2-s per kg/m3) V/fractton of vegetative cover (unrdess) Um /mean annual windspeed (m/s) U, /equivalent threshold value of wind- speed at 7 m (m/s) F(x)/functbn dependent on Um/Ut derived using Cowherd (1985) (unrttess) Default 6.79 x 108 46.84 0.5 (50%) 4.69 11.32 0.194 . PEF — Mean annual windspeed — Threshold friction velocity (as determined by): - mode of the surface soil aggregate size - toughness height - correction for nonerodible particles - f(x) — Equivalent threshold windspeed at a 7-m anemometer height. Site location (to some extent) and site size (Le., "area of contamination") can be factored into die simple site-specific methodology for the inhalation pathways. The dispersion factor (Q/O for bom volatiles and fugitive dusts was calculated using a 90th percentile meteorological data set selected from 29 data sets across the United States (see Technical Background Document [U.S. EPA, 1994e]). Los Angeles was selected as die 90th percentile data set for volatiles and Minneapolis was selected as the 90th percentile data set for fugitive dusts. Replacing the default city and site size of 30 acres will affect the Q/C values in both the VF and PEF equations (Equations 5 and 7). The Technical Background Document supporting this guidance (U.S. EPA, 1994e) provides a table of Q/C values for 29 cities across the country over a range of contaminant source areas for use in the simple site-specific method. The paniculate emission factor derived by using the default values in Equation 7 results in an ambient air concentration of approximately 1.5 ng/m3. This represents an annual average emission rate mat is based on wind erosion and is not appropriate for evaluating the potential for more acute Migration to Ground Water The methodology for addressing migration of contaminants from soil to ground water reflects the complex nature of contaminant fate and transport in the subsurface. In this methodology, a concentration in soil is backcalculated from an acceptable ground water concentration. The generic SSLs presented in Appendix A for this pathway represent a conservative estimation of the concentration of a contaminant in soil mat would not result in exceedances of the acceptable concentration of a contaminant in ground water. Flexibility to consider site-specific conditions is addressed in the simple and detailed site-specific methodologies. The first step in applying the SSL framework is a comparison of the SSL conceptual model presented earlier in mis document with the conceptual model developed for the she. This forms the basis for determining die appropriateness of conducting a more detailed investigation and the applicability of the SSL guidance for the migration to ground water pathway. Some of the assumptions used to develop the SSL conceptual model have implications for the ground water pathway. Highlight 4 lists assumptions implicit in the conceptual model that should be understood before applying the SSL ground water frame- work. Bom the simple site-specific and generic methods are based on the commonly used equilibrium soil/water partition equation (Equation 8) that describes the ability of contaminants to sorb Equation 8: Soil Screening Level Partitioning Equation for Migration to Ground Water Screening Level in Sol (mg/kg) Parameter/Definition (unite) Cw/target soH leachate concentration (mg/L) Kj/sofl-water partition coefficient r^c /soil organic carbon/water partition coefficient (Lfcg) fee/fraction organic carbon in soil (9/9) abater-fitted soi porosity w/average soil moisture content or Pb/dry soi bulc density (kg/L) it/soil porosity p,/soil particle density 9,/aJr-fiHed soil porosity HVHenry's law constant (uniUsss) H/Henry's law constant (atm-ms/mol) Default nonzero MCLG, MCL, or HBL x 10 DAF chemical-specific, K^. xf^forganics) hemJcaJ-specific 0.002 (02%) 0.3 or wpb 0.2 1.5or(1-n)p. 0.43 (loam) 2.65 0.13 or (n - 8J Hx41 chemical-specific (assume to be zero for inorganic con- taminants except mercury) 11 TUT COS 1021 Review Draft—Do Not Cite or Quote—December 1994 Highlight 4: SimpSfying Assumption* of thf Default Conceptual Mode/ for Ground Water 1. The source of contamination is defined as an evenly contaminated 30-acro site. Source size has signifi- cant implications for the development of the dilution/ attenuation factor. Large sources generally tend to result in low DAFs, while smaller sources generally justify higher DAFs. Where actual source size differs significantly from the default 30-acro assumption, the user should consider a site-specific evaluation to develop a more site-specific DAF. 2. The soil contamination extends from the surface to the top of the aquifer. This is a reasonable assump- tion for sites where the water table is fairly shallow (e.g., 5 to 10 feet below surface). However, in areas where the water table is very deep, this assumption may not be valid and should be considered in the decision to apply a detailed site-specific evaluation. 3. No attenuation is considered in the unsaturated zone. This assumption also has implications for the DAF. As discussed above, a detailed site-specific evaluation should be considered at sites that have a very thick uncontaminated unsaturated zone because a higher DAF may be justified. 4. The point of compliance is at the edge of the site, which is assumed to be uniformly contaminated. This conservative assumption also has implications for the calculation of the DAF. The user should consider whether this assumption is valid for the site in question and whether further evaluation would be appropriate. 5. The simple site-specific or generic DAF assumes that an unconfined, unconsoiidated aquifer with homogeneous and isotropic hydrologic properties underlies the site. A DAF greater than 1 may not be appropriate for soils underlain by karst or fractured reck aquifers. 6. NAPLs are not present. If NAPLs are present in soils, the SSLs do not apply (i.e., further investiga- tion is necessary). to organic carbon in soil (Dragon, 1988). An adjustment to relate sorbed concentration in soil to die analytically measured total soil concentration has been added to the equation. The partition equation contains parameters for chemical- specific (Henry's law constant; K,, or K^ and subsurface characteristic variables (dry bulk density, porosity, air-filled and water-filled pore space). In the default method, national default values for the parameters in the partition equation were used to calculate the generic SSLs in Appendix A. Nonzero ground water maximum contaminant level goals (MCLGs) were used as the acceptable ground water limits for each contaminant in the partitioning equation. If nonzero MCLGs were not available, maximum contaminant kvels (MGLs) were used. If MCLs were not- available, concentrations associated with a target cancer risk "of 1CT 6 and/or a noncancer HQ of 1 were derived usiag Agency toxicity criteria. The acceptable ground water limit is multiplied by the DAF of 10 to obtain a target soil leachate concentration for calculating generic SSLs. In the simple site-specific method, site-measured data would replace the default values for the subsurface characteristic and soil variables (Le., fraction organic carbon, dry bulk density, average soil moisture content). These variables would then be used to calculate a more site-specific screening value. Even this screening number is fairly conservative because of the underlying assumptions regarding the absence of attenuation and placement of the well adjacent to the source. As described above, the C,* ceiling limit defines (for organic chemicals mat are liquid at soil temperatures) a concentration above which chemicals may occur as NAPLs in soil. For liquid chemicals present at concentrations greater man C—, NAPL presence may be suspected and the Soil Screening framework would not be applicable (Le., further investigation is necessary). See US. EPA (1992b) for guidance on deter- mining the likelihood of NAPL occurrence in the subsurface and on conducting the additional investigations necessary if NAPL occurrence is suspected at a site. Partitioning of inorganic constituents in the subsurface is more complex than for organics. A variety of soil conditions affect the derivation of die partitioning coefficient for inorganics, white organic carbon is die parameter that most affects organic partitioning. For mis reason, the EPA MENTEQ2 equilibrium geochemical speciation model was used to calculate K^ values fro the metals, which were then used in Equation 8. Kj values for metals are most significantly affected by pH; therefore, metal K^ values were calculated over a range of subsurface pH conditions (4.9 to 8.0). K,, values corresponding to mis pH range are presented in the revised Technical Background Document (U.S. EPA, 1994e) for use in the simple site- specific method. Based on the pH at the site, die appropriate KJ should be selected and used in die calculation. Also note that all metals except mercury are essentially nonvolatile and dieir Henry's law constant (HO in Equation 8 should be set at zero. Generic SSLs for inorganics corresponding to a pH of 6.8 are presented in Appendix A far die default method. Table 1 lists inorganic SSLs corresponding to pH values of 43 and 8.0 and a DAF of 10. If pH conditions at a site are not known, die generic SSL corresponding to a pH of 6.8 should be used in die default method. Table 1 also includes SSLs for ionizing organics, whose partitioning behavior is also pH dependent Readers are referred to the Technical Background Document (U.S. EPA, 1994e) for a more detailed discussion of die derivation of K* values for inorganics and K^ values for ionizing and nonionizing organics. The framework also includes die option of using a teach te instead of die partitioning equation. In some instances a teach TUT oos Review Draft—Do Not Cite or Quote—December 1994 Table 1. pH-Speeific SSLs tor Metals and Ionizing Organlcs (mg/kg) (DAF = 10) Chemical Arsenic Barium Beryllium Cadmium Chromium (+6) Mercury Nickel Selenium Thallium Zinc Benzole acid 2,4-Dchlorophenol Pentachbrophenol 2,4,5-Tricrdorophenol 2,4,6-Tnchiorophenol PH4.9 13 16 0.1 0.06 31 0.006 1 9 0.2 180 300 0.5 0.2 200 0.07 pH8 16 340 . 19,000 230 14 4 140 1 0.5 1.6E+6 280 0.3 0.01 26 0.01 test may be more useful man the partitioning method, depend- ing on the constituents of concern and the possible presence of RCRA wastes. This guidance suggests using the EPA Synthetic Precipitation Leaching Procedure (SPLP, EPA SW- 846 Method 1312, see the Technical Background Dcoument [U.S. EPA, 1994e]). The SPLP was developed to model an acid rain leaching environment and is generally appropriate for a contaminated soil scenario. Like most leach tests, the SPLP may not be appropriate for an situations (e.g., soils contaminated with oily constituents may not yield suitable results). Therefore, discretion is advised when applying the SPLP. The Agency is aware mat there are many leach tests available for application at hazardous waste sites, some of which may be appropriate in specific situations (e.g^ the Toxiciry Charac- teristic Leaching Procedure, known as the TCLP, models leaching in a municipal landfill environment). It is beyond the scope of mis document to discuss in detail other leaching procedures and the appropriateness of their use. Stabilization/ Solidification of CERCLA and RCRA Wastes (UJS. EPA, 1989c) and the SAB's review of leaching tests (UJS. EPA. 1991c) contain information on the application of various teach tests to various waste disposal scenarios. The user is encouraged to consult these doucments for tether information. DETERMINING THE DILUTION/ ATTENUATION FACTOR As contaminants move through soil and ground water, they are subjected to a number of physical, chemical, and biological processes that generally reduce the eventual contaminant concentration level at receptor points. The reduction in concentration can be expressed succinctly by the DAF, defined as the ratio of the soil leachate concentration to the receptor point concentration. The lowest possible value of DAF is 1, corresponding to the situation where there is no dilution or attenuation of a contaminant; Le- the concentration at the receptor point is the same as mat in the soil leachate. High DAF values, on the other hand, correspond to a high degree of dilution and attenuation of the contaminant from the leachate to the receptor point The soil/water partition equation relates concentrations of contaminants adsorbed to soil organic carbon to soil leachate concentrations in the unsaturated zone. Contaminant migration through the unsahirated zone to the water table generally reduces the soil leachate concentration by attenuation processes such as adsorption and degradation. Ground water transport in the saturated zone further reduces concentrations through adsorption, degradation, and dilution. Generally, to account for this reduction in concentration, acceptable ground water limits are multiplied by a DAF to obtain a target soil leachate concentration for me partition equation. A default DAF of 10 is applied to calculate the generic SSLs. A weight of evidence method was used to determine mis default DAF. In the weight-of-evidence approach, OERR evaluated a number of methods for calculating DAFs. Included in mis approach was an evaluation of DAFs calculated by the EPACMTP model, using a range of assumptions including those associated with the conceptual site model for the generic SSLs. The comparison also included DAFs calculated from a more simplified mixing-zone equation, as well as acceptable DAFs used in existing State programs. The comparison indicated that, for the default scenario, a DAF of 10 is conservatively protective of the majority of site conditions, including the site scenario developed for the generic SSLs. The Technical Background Document (UJS. EPA, 1994e) supporting this guidance contains additional detail on the development of the generic DAF. The simple site-specific method relies on a fairly simple mixing zone equation (Equation 9) to calculate a site-specific dilution factor to be used instead of the default DAF. In mis method, site-measured values for hydraulic gradient, hydraulic Equation 9: Derivation of Dilution Factor dkJtion factor- 1 •»Md IT Parameter/Definition (units) dilution factor (unitless) K/aquifer hydraulic conductivity (m/yr) i/hydraufc gradient (m/m) d/mixing zone depth (m) I/infiltration rate (m/yr) L/source length parallel to ground water flow (m) 13 TUT OO8 1023 Review Draft—Do Not Cite or Quote—December 1994 conductivity, and estimates of infiltration, contaminant source length, and mixing-zone depth are used to calculate the dilution factor. The mixing-zone depth is estimated from an equation relating it to aquifer thickness, infiltration rate, ground water velocity, and source length parallel to flow (Equation 10). Equation 10: Estimation of Mixing Zone Depth d . (0.0112 L2)" + d. {1 - exp[(-Liy(Kida)]} Parameter/Definition (units) d/mixing zone depth (m) L/souree length parallel to ground water flow (m) I/infiltration rate (m/yr) K/aquifer hydraulic conductivity (m/yr) dg/aquifer thickness (m) Detailed Site-Specific Method In mis investigation, site-specific data are collected and used in a fate and transport model to determine whether a mreat to ground water exists and, if so, to further determine site-specific cleanup goals as would typically be done for the remedial investigation/feasibility study (RI/FS). Consequently it represents the highest level of site-specificity in evaluating the migration to ground water pathway. A DAF is not used in this method because the model would account for fate and transport mechanisms in the subsurface. The advantage of this approach is mat it accounts for site hydrogeologic, cibnatologic, and contaminant source characteristics and may result in fully protective but less stringent remediation goals. However, the additional cost of collecting the data required to apply the model should be factored into the decision to conduct a detailed site-specific investigation. Choosing a model for site-specific application is integral to an accurate evaluation of potential concern. However, the data used in the application and interpretion of the results are equally important In an effort to provide useful information for a model application, EPA's ORD Laboratories in Ada, Oklahoma, and Athens, Georgia, conducted an evaluation of nine unsatnrated zone fate and transport models. The infor- mation in this report is summarized in the Technical Background Document (U.S. EPA, 1994e) supporting this guidance. These nine models are only a subset of the poten- tially appropriate models available to the public and are not meant to be comtrued as having received EPA approval EPA also has developed guidance for the selection and application of ground water transport and fate models and for interpreta- tion of model applications. The user is referred to Ground Water Modeling Compendium (U.S. EPA, 1994b) and Frame- work for Assessing Ground Water Model Applications (U.S. EPA, 1994a) for further information. MEASURING CONTAMINANT CONCENTRATIONS IN SOIL In order to compare site soil concentrations with the SSLs, it is important to develop a sampling strategy that will result in an accurate representation of site contamination. This Soil Screening Guidance recommends mat site managers use the Data Quality Objectives (DQO) process (Figure 5) to develop a sampling strategy mat will satisfy Superfund program objectives. The site manager can use the DQO process to conveniently organize and document many site-specific features and assumptions underlying the sampling plan. In the last step of the DQO process, "Optimize the Design for Obtaining Data," the site manager can choose between two alternative approaches to measuring surface soil contaminant concentrations. The first is a site-specific strategy that uses site-specific estimates of contaminant variability to determine how many samples are needed to support the screening decision. The second is a fairly prescriptive approach that can be used in lieu of the site-specific strategy. Recommendations for subsurface sampling that can be modified to accommodate she-specific conditions are also included in the guidance. Exposure to site contaminants over a long (chronic) period of time is best represented by an arithmetic average concentration for an exposure area (U.S. EPA, 1992d). Therefore, measure- ment of site concentrations for comparison to the SSLs should State the Problem Identify the Decision Identify Inputs to the Dedeton Define the Study Boundaries Develop a Decision Rule SpeotyUmtts on Decision Errors Optimize the Design for Obtaining Data Figure 5. The Data Quality Objectives process. 14 TUT O08 Ftovtow Draft—Do Not CH» or Quote Daoamber 1994 be based on the arithmetic mean concentration as weD. Forthe purposes of this guidance, the Agency has assumed that the size of a typical residential lot (0.5 acre) is an appropriate averaging area for residential land use. For large sites that could be divided into multiple residential lots, the site should be sectioned into appropriate 0.5-acre parcels. For measurement of surface soil samples for the inhalation and ingestion pathways, samples should be collected over a depth of 6 inches because it is the top 6 inches of soil that is most likely to be ingested or inhaled as fugitive dusts. Additional sampling beyond 6 inches may be appropriate, depending on the contaminant's mobility. If soils at the site are of concern for the migration to ground water pathway as well as the Digestion and/or inhalation pathways, men surface soils should be sampled first since the results of the composite samples may indicate source areas to target for subsurface sampling. As discussed previously, the initial steps for implementing the Soil Screening framework are to (1) develop the conceptual site model and determine the applicability of the framework; (2) determine if background concentrations exceed the (generic) SSLs; and (3) select the method (simple site-specific, detailed site-specific, or generic) to determine the SSLs. Once these steps have been completed, it will then be necessary to choose either a site-specific or a generic, prescriptive sampling strategy for surface soils. Surface Soils—Site-Specific Strategy The site-specific sampling strategy utilizes a sampling design approach mat allows statistically valid conclusions to be drawn about contaminant concentrations at a site based on relatively limited sampling. EPA recommends that site managers use mis strategy to determine the number of samples needed to compare average contaminant concentrations within each exposure area against the SSLs. The site-specific strategy provides procedures for ensuring that screening decisions can be made with acceptable levels of confidence despite variability in soil contaminant concentrations that can sometimes mask true conditions at the site. This approach provides flexibility to incorporate site-specific information about likely contamination patterns so mat sampling can be concentrated in areas where uncertainty about the risk posed by soil contaminants is greatest The sampling design developed for the site should be based on the conceptual site model and should reflect conditions at the site. It is flexible in that the information used to develop the conceptual site model (historical records, aerial photographs, existing sampling data, etc.) can also be used to develop an appropriate sampling strategy. Such a strategy may include stratification of the site, if appropriate, into areas where soil contaminant concentrations are expected to clearly exceed the SSLs, areas where soil contaminant concentrations are expected to fall well below the SSLs, and areas of the site where mere is greater uncertainty as to whether soil contaminant concentrations exceed the SSLs. this classification of areas of the site can help in designing an efficient sampling plan, since the number of samples required to support good decision making depends on the contaminant variability likely to be encountered and how greatly contaminant concentrations differ from the SSLs. By grouping similar areas together, each area can be sampled in accordance with the level of uncertainty or variability associated with that area. For example, EPA expects that a relatively small number of samples will be needed to make the screening decision where average contaminant concentrations clearly exceed or are well below the SSLs. More intensive sampling is expected for those areas where relatively high contaminant variability or concentrations close to the SSLs make it more difficult to determine with confidence whether the average contaminant concentration exceeds the screening level Inherent in the statistically based site-specific sampling strategy is me specification of limits on decision errors, which is performed in the sixth step of the DQO process. Limits on decision errors are Quantitative performance requirements for the quality and quantity of data mat will support the screening decision. These performance requirements are specified in terms of Ihe probability of making a decision error, which can occur in two ways: • Type I: The data mislead the site manager into deciding that the exposure area concentration is below the SSLs when the true average contaminant concentration exceeds the screening level; or • Type It The data mislead the site manager into deciding that the exposure area concentration is above the SSL and further investigation is required when in fact the true average contaminant concentration is less than the SSL. To ensure consistency in applying the framework, EPA has specified tolerable limits on decision errors at the program level The Technical Background Document (U.S. EPA, 1994e) provides a fuD discussion of the Soil Screening framework's limits on decision errors and of the site-specific strategy in general EPA encourages the project manager to seek the assistance of a statistician or the Regional quality assurance staff for the development of the sampling strategy. For more detailed guidance on the DQO process the user should refer to the Technical Background Document and Data Quality Objectives far Superfiind (Interim Final) (U.S. EPA, 1993a). Surface Soils—Prescriptive Approach The guidance provides a second sampling methodology—a "prescriptive approach"—that can be used as an alternative to die site-specific approach. A sampling design effort is required for the site-specific strategy, whereas me prescriptive approach provides a simple, standard sampling approach mat win be most useful for small sites that do not warrant an extensive design effort It emphasizes composite sampling for IS TUT OOS 1O25 ftovfew Draft—Oo Not Cite or Quote—D*oMnbw 1994 nonvolatile contaminants and specifies the number of samples to be collected for analysis of volatile contaminants. It differs from the site-specific approach in that the same sampling strategy most be applied to each 0.5-acre exposure area. Although it does not explicitly control decision errors, preliminary simulations suggest that it does not underestimate mean concentrations for commonly occurring patterns of soil contamination. Additional simulations comparing the. performance of the prescriptive approach to the site-specific strategy will be a subject of peer review. Studies by OKD indicate that at least 20 samples per exposure area are needed to closely estimate the true mean. To balance the need for statistical confidence in determining a meaningful arithmetic mean contaminant concentration with the costs of analyzing multiple samples for each exposure area, EPA recognizes the benefits of composite samples and advocates compositing, where appropriate. Compositing may mask contaminant levels mat are slightly higher nan the SSL, but areas of high contamination will soil be detected. Compositing is a reasonable approach and an efficient use of resources since the Superfund program is interested in the average exposure over time. (See the Technical Background Document [U.S. EPA, 1994e] for a more detailed discussion of compositing and its limitations.) Using the prescriptive approach, 20 discrete samples can be reduced to four composite samples. Cine exposure area can be divided into quadrants and five random samples can be collected and composited within each quadrant) The contam- inant concentrations from the four composite samples should be compared directly with their respective SSLs. If any one of the composites equals or exceeds the SSL, then that portion of the exposure area should be studied further. Compositing is not appropriate for volatile organic compounds (VOCs) since much of the contaminant will be lost during homogenization of the soil (U.S. EPA, 1989a, 1992c). For VOCs, 10 discrete samples can be taken per exposure area and any sample above die SSL would trigger the need for additional study in that exposure area. Additionally, it is not appropriate to average the contaminant levels in each exposure area and evaluate the mean concentration against the SSLs because 10 discrete samples may underestimate the true mean. Subsurface Sampling For the migration to ground water pathway, subsurface soils mat have constituents that might contribute to ground water contamination are of primary concern. Therefore, it is the source areas that are of interest and not necessarily a 0.5-acre exposure area as specified for the ingestion and inhalation pathways. To determine whether contaminants in the subsur- face soils (defined as below 6 inches for me purposes of implementing SSLs) potentially pose a risk to ground water, (he guidance suggests sampling at teast two boreholes using split spoon or Shelby tube samples in each source area. Samples should begin at 6 inches below ground surface and continue at 2-foot intervals until no contamination is encountered. If the average concentration in any borehole exceeds the SSL, men further site-specific study is warranted. Subsurface sampling depths and intervals can be adjusted at a site to accommodate site-specific information on subsurface contaminant distributions and geological conditions. In addition, soil investigation for the migration to ground water pathway should not be conducted independent of ground water investigation. Ground water should be sampled to determine whether mere is concern for existing ground water contam- ination, and the results should be considered in the holistic application of the Soil Screening framework. Geostatistics If the SSLs are to be compared with the data resulting from the initial sample collection efforts of the remedial investigation, the site manager may want to consider using geostatistics to estimate contaminant concentrations across the site. Geostatistics is probably most appropriate to use in the detailed site-specific approach. Geostatistics is a field of study in which statistical analyses of geologic or environmental data are conducted. It differs from single-sample classical statistics in mat it assumes mat variability and independence between samples is not random, but mat mere is some spatial continuity between samples. Geostatistics can be used to estimate contaminant concentrations at unsampled points and estimate average contaminant concentrations across the site. Software packages have been developed to fatititatr geostatistical analyses. One package is GEO-EAS, developer by EPA's Environmental Monitoring Systems Laboratory in Las Vegas, Nevada. Assistance and consultation with skilled geostatisticians is recommended prior to initiating any sampling plan to ensure that the sampling strategy will capture the critical data necessary for the geostatistical analyses. WHERE TO GO FOR FURTHER INFORMATION More detailed discussions of the technical background and assumptions supporting the development of the Soil Screening framework are presented in the Technical Background Document for Soil Screening Guidance (U.S. EPA, 1994e). For additional copies of this Fact Sheet and/or the Technical Background Document, call the National Technical Information Service (NTIS) at (703) 487-4650. 16 TUT 008 1026 Review Draft—Do Not Cfta or Quote December 1994 NOTICE: This guidance is based on policies in the Final Rule of the National Oil and Hazardous Substances Pollution Contingency Plan (NCP), which was published on March 8, 1990 (55 Moral Register 8666). The NCP should be considered the authoritative source. The pofioies set out in this document are intended solely as guidance to the U.S. Environmental Protection Agency (ERA) personnel; they are not final EPA actions and do not constitute rutemaking. These policies are not intended, nor can they be relied upon, to create any rights enforceable by any party in litigation with the United States. EPA officials may decide to follow the guidance provided in this document, or to act at variance with the guidance, based on an analysis of specific site circumstances. EPA also reserves the right to change the guidance at any time without public notice. REFERENCES Cabbrcse, EJ., H. Pastides, R. Bames, et aL 1989. How Much Soil Do Young Children Ingest An Epidemiologic Study. In: Petroleum Contaminated Soils, VoL 2. EJ. Calabrese and P.T. Kostedti, eds. pp. 363-417. Chelsea, MI, Lewis Publishers. Cowherd, C, G. Mutesld, P. Engelhart, and D. Gillette. 1985. Rapid Assessment of Exposure to Paniculate Emission from Surface Contamination. EPA/600/8-85/002. Prepared for Office of Health and Environmental Assessment, U.S. Environmental Protection Agency, Washington, DC. NTTS PB85-192219 7AS. Davis, S., P. Waller, R. Buschom, J. Ballou, and P. White. 1990. Quantitative estimates of soil ingestion in normal children between the ages of 2 and 7 years: population- based estimates using Al, Si, and Ti as soil tracer elements. Archives of Environmental Health, 45:112-122. Dragon, J. 1988. The Soil Chemistry of Hazardous Materials. Hazardous Materials Control Research Institute, Silver Spring, MD. U.S. EPA. 1988. Guidance on Remedial Actions far Contaminated Ground Water at Superfund Sites. Directive 9283.1-2. EPA/540/G-88/003. Office of Emergency and Remedial Response, Washington, DC. NTIS PB89- 184618/CCE. U.S. EPA. 1989a. Methods for Evaluating the Attainment of Soil Cleanup Standards. Volume 1: Soils and Solid Media. EPA 230/02-89-042. Statistical Policy Branch, Office of Policy, Planning, and Evaluation, Washington, DC U.S. EPA. 1989b. Risk Assessment Guidance for Superfund: Volume 1: Human Health Evaluation Manual, Part A, Interim Final. EPA/540A-89/002. Office of Emergency and Remedial Response, Washington, DC NTIS PB90- 155581/CCE. U.S. EPA. 1989c. Stabilization/Solidification ofCERCLA and RCRA Wastes. EPA/625/S-89/D22. U.S. EPA. 1990a. Guidance on Remedial Actions for Superfund Sites with PCB Contamination. EPA 540G- 90/007. Office of Emergency and Remedial Response, Washington, DC NTIS PB91-921206/CCE. U.S. EPA. 1990b. Suggested ROD Language for Various Ground Water Remediation Options. Directive 9283.1-03. Office of Emergency and Remedial Response, Washington, DC. NTIS PB91-921325/CCE. U.S. EPA. 1991a. Guidance for Risk Assessment. Risk Assessment Council, Office of the Administrator, Washington, DC. U.S. EPA. 1991b. Human Health Evaluation Manual, Supplemental Guidance: Standard Default Exposure Factors. Publication 9285.6-03. Office of Emergency and Remedial Response, Washing ton, DC. NTIS PB91-921314. U.S. EPA. 199 Ic. LeachabiUty Phenomena. Recommenda- tions and Rationale for Analysis of Contaminant Release by the Environmental Engineering Committee. EPA-SAB- EEC-92-003. Science Advisory Board, Washington, DC. U.S. EPA. 1991d. Risk Assessment Guidance for Superfund. Volume 1: Human Health Evaluation Manual (Part B, Development of Risk-Based Preliminary Remediation Goals). Publication 9285.7-01B. Office of Emergency and Remedial Response, Washington, DC NTIS PB92-963333. U.S. EPA. 1991e. Role of the Baseline Risk Assessment in Superfund Remedy Selection Decisions. Publication 9355.0-30. Office of Emergency and Remedial Response, Washington, DC. NTIS PB91-921359/CCE. U.S. EPA. 1992a. Considerations in Ground-Water Remediation at Superfund Sites and RCRA Facilities— Update. Directive 9283.1-06. Office of Emergency and Remedial Response, Washington, DC. NTIS PB91- 238584/CCE. US. EPA. 1992b. Estimating Potential for Occurrence of DNAPL at Superfund Sites. Publication 9355.4-07FS. Office of Emergency and Remedial Response, Washington, DC. NTJS PB92-963338. 17 TUT OO8 1027 Review Draft—Do Not Cite or Quote—December 1994 U.S. EPA. 1992c. Guidance for Data Usability in Risk Assessment (Part A). Office of Emergency and Remedial Response, Washington, DC. NTIS PB92-963356. U.S. EPA. 1992d. Supplemental Guidance to RAGS: Calculating the Concentration Term, Volume 1, Number 1. Publication 9285.7-011. Office of Emergency and Remedial Response, Washington, DC. NTTSPB92-963373. U.S. EPA. 1993a. Data Quality Objectives for Superfund: Interim Final Guidance. EPA 540-R-93-071. Publication 92555-01. Office of Emergency and Remedial Response, Washington, DC. NTIS PB94-963203. U.S. EPA. 1993b. Guidance for Evaluating Technical Impracticability of Ground-Water Restoration. Directive 92342-25. EPA/540-R-93-080. Office of Emergency and Remedial Response, Washington, DC. U.S. EPA. 1993c. Health Effects Assessment Summary Tables (HEAST): Annual Update, FY1993. Environmen- tal Criteria and Assessment Office, Office of Health and Environmental Assessment, Office of Research and Development, Cincinnati, OR U.S. EPA. 1993d. Science Advisory Board Review of die Office of Solid Waste and Emergency Response draft Risk Assessment Guidance for Superfund (RAGS), Human Health Evaluation Manual (HHEM). EPA-S AB-EHC-93- 007. Science Advisory Board, Washington, DC. U.S. EPA. 1994a. Framework for Assessing Ground Water Modeling Applications. EPA-500-B-94-004. Resource Management and Information Staff. Office of Solid Waste and Emergency Response, Washington, DC. U.S. EPA. 1994b. Ground Water Modeling Compendium, Second Edition. EPA-500-B-94-003. Resource Management and Information Staff. Office of Solid Waste and Emergency Response, Washington, DC. U.S.EPA. 1994c. Integrated Risk Information System (IRIS). Duluth, MM. UJS.EPA. 19944 Role of the Ecological Risk Assessment in the Baseline Risk Assessment. OSWER Directive No. 9285.7-17. Office of Solid Waste and Emergency Response, Washington, DC. August 12. U.S. EPA. 1994e. Technical Background Document for Soil Screening Guidance. EPA/540/R-94/102. Office of Emergency and Remedial Response, Washington, DC. PB9S-963530. Van Wijnen, JJL, P. Clausing, and B. Bnmekreef. 1990. Estimated Soil Ingestion by Children. Environmental Research, 51:147-162. 18 TUT COS 1028 Review Draft—Do Not Cite or Quote December 1994 Appendix A. Generic Soil Screening Levels for Superfund* NOTICE: These values were developed for use in application of the So9 Screening Guidance only. They were developed for specific exposure pathways constituting a residential scenario and should only be used in that context GAS No. 83-32-9 67-64-1 309-00-2 120-12-7 71-43-2 56-55-3 205-99-2 207-08-9 50-32-8 111-44-4 117-81-7 75-27-4 75-25-2 71-36-3 85-68-7 86-74-8 75-15-0 56-23-5 57-74-9 108-90-7 124-48-1 67-66-3 218-01-9 72-54-8 72-55-9 50-29-3 53-70-3 84-74-2 95-50-1 106-46-7 91-94-1 75-34-3 107-06-2 75-35-4 156-59-2 156-60-5 78-87-5 542-75-6 60-57-1 84-66-2 131-11-3 121-14-2 606-20-2 / ——— \ JB|O[ Chemical Acenapnthene Acetone AWrin Anthracene Benzene Benzo<a)anthracene Benzo(b)fluoranthene Benzo(A)fluoranthene Benzo(a)pyrene Bis(2-chlorethyl)ether Bis(2-ethyihexyl)phthalate Bromodichloromethane Bromoform Butanol Butyl benzyl phthalate Carbazote Carbon disulfide Carbon tetrachloride Chbrdane Chtorobenzene Chtorodtoromomethane Chloroform Chrysene DDD DDE DOT Dibenzo(a,ft)anthracene Di-n-butyl phthalate 1,2-Dfchforobenzene (o) 1,4-Dichlorobenzene (p) 3,3-Dichlorobenzidine 1 ,1-Dichbroethane 1^-Dchtoroethane 1,1-Dichtofoetnylene efe-1 ,2-Dichtaroethylene fnns-1,2-Did*>roethylene 1,2-Dtehbropropane 1 ,3-Dichtoropropene Dieklrin Diethyl phthalate Dimethyl phthalate 2,4-Dinhrotoluene 2,6-DinJtrotoluene Pathway-specific values for surface soils (mgVkg) Ingest ion 4,700 b 7,800 b 0.04* 23,000 b 22* 0.9 • 0.9* 9* 0.09 *>f 0.6* 46* 5* 81 « 7,800 b 16,000" 32* 7,800 b 5* 0.5* 1,600 b 8* 110* 88* 3* 2* 2* 0.09 *-f 7,800 b 7,000 b 27* 1* 7,800 b 7* 1 • 780 b 1,600 b 9* 4* 0.04* 63,000 b 7.8E+5 b 160 b 78 b Inhalation _ e 62,000 d 0.5* _ e 0.5* — c __ e _ e _ e 0.3 *>f 210 d 1,800 d 46* 9,700 d 530d __ e 11 b 0.2* 10* 94b 1,900 d OJ>* _ c , c c 80* __ e 100 d 300d 7,700 b _ c 980 b 0.3* 0.04* 1,SOOd 3,600 d 11 b 0.1* 2* 520d 1,600 d — e _ e Migration to ground water pathway levels (mg/kg) WHhlO DAF 200b 8b 0.005* 4,300 b 0.02 0.7 4 4 4 3E-4*1' 11 0.3 0^ 8 b 68 0.2 *•' 14 b 0.03 2 0.6 0.2 0.3 1 0.7* 0.5* 1* 11 120 b 6 1 0.01 *•' 11 b 0.01 f 0.03 OJ2 03 0.02 O.001*-' 0.001 *•' 110 b 1^00 b 0.2 w 0.1 w Withl DAF 20" 0.8 b SE-4*'1 430b 0.002' 0.07 ' 0.4 0.4 0.4 3E-5*^ 1 0.03 0.05 0.8" 7 0.02 '•' 1" 0.003 ' 0.2 0.06 0.02 0.03 0.1 f 0.07* 0.05* 0.1* 1 12" 0.6 0.1' 0.001 *•' 1 b 0.001 f 0.003 f 0.02 0.03 0.002 f IE-4*-' 1E-4*1' 11 " 120 b 0.02 btf 0.01 ^ 19 TUT 00B 1029 (continued) nvvww UFBifr— t/« noi ^iw or vwowr— WWW«II«BI i»w» Appendix A (continued) GAS No. 117-84-0 115-29-7 72-20-8 100-41-4 206-44-0 86-73-7 76-44-8 1024-57-3 118-74-1 87-68-3 319-84-6 319-85-7 58-89-9 77-47-4 67-72-1 193-39-5 78-59-1 72-43-5 74-83-9 75-09-2 91-20-3 98-95-3 1336-36-3 129-00-0 100-42-5 79-34-5 127-18-4 108-88-3 8001-35-2 120-82-1 71-55-6 79-00-5 79-01-6 108-05-4 75-01-4 1330-20-7 65-85-0 10&47-8 95-57-8 120-83-2 105-67-9 51-28-5 95-48-7 / ——— \ jB|e, Chemical Di-n-octyl phthalate Endosulfan Endrin Ethyfcenzene Fkioranthene Fluorene Heptachbr Heptachbr epoxide Hexachtorobenzene H«xach)oro-1 ,3-butadiene o-HCH (a-BHC) B-HCH (6-BHC) •y-HCH (Undane) Hexachlorocyclopentadiene Hexachtoroethane lndeno(1 ,2,3-c,d)pyrene Isophorone Methoxychlor Methyl bromide Methylene chloride Naphthalene Nitrobenzene Polychbrinated biphenyts (PCBs) Pyrene Stryene 1 ,1 ,2,2-Tetrachbroethane Tetrachloroethyiene Toluene Toxaphene 1 ,2,4-TrichlofODenzene 1,1,1-Trichloroethane 1,1,2-Trichloroethane Trichbroethytene Vinyl acetate Vinyl chloride Xytenes (total) lonizable Organic* Benzoicacid p-Chbroaniline 2-Chbrophenol 2,4-Dfchbrophenol 2,4-Dimethyiphenol 2,4-Dinttrophenol 2-Methybhenol Pathway-specific values for surface soils (mg/kg) ktgestfen Inhalation 1,600b 470 b 23b 7,800 b 3,100 b 3,100 b <M* 0.07" 0.4* 8" 0.1" 0.4- 0.5 • 550 b 46* 0.9* 670* 390 b 110b 85* 3,100 b 39 b 1h 2,300 b 16,000 b 3« 12" 16,000 b 0.6* 780 b _ e 11 • 58* 78,000 b 0.3 • 1.6E+5b 3.1E+5" 310 b 390 b 240 b 1,600 b 160 b 3,900 b _ e _ e _ e 260 d _ e _ c 0.3* 1« 1« 1« 0.9 • 16* _e 2b 49" _ e 3,400 d _ e 2b 7* _ c 110b ^.e-11 _ e 1,400 d 0.4« 11 • 520 d 5d 240 b 980 d 0.8- 3« 370 b 0.002 "•' 320 d c c 53,000 d c __e c _ c Migration to ground water pathway levels (mg/kg) With 10 DAF _ g 4b 0^ 5 980 b 160 b 0.06 0.03 0.8 0.1 f 4E-4"-' 0.002* 0.006 10 0.2 "•' 35 0.2* 62 0.1 b 0.01 ' 30b 0.09 w _h 1,400 b 2 0.001 *-f 0.04 5 0.04 f 2 0.9 0.01 f 0.02 84 b 0.01 f 74 280 W OjMi 2w 0^w 3b.i 0.1 "" 6W With! DAF _ g 0.4 b 0.04 0.5 98 b 16 b 0.006 0.003 0.08 f 0.01 f 4E-5* 2E-4* 6E-4* 1 0.02 ••' 3 0.02 "•' 6 0.01 W 0.001 f 3b 0.009 w _ h 140 b 0^ 1E-4'-' 0.004 f 0.5 0.004 f 0.2 f 0.09 0.001 f 0.002 f 8b 0.001 f 7 22 b.i 0.03 W 0.2 •* 0.05"* 0.3^ 0.01 Mi 0.6 w 20 (continued) TUT COS 1O30 Review Draft—Do Not Cite or Quote—December 1994 Appendix A (continued) Pathway-specific values for surface soils (mg/kg) Ifigratton to ground water pathway levels (mg/kg) CASNo. Chemical Ingestion Inhalation With 10 DAF Withl DAF 86-30-6 621-64-7 87-86-5 108-95-2 95-95-4 88-06-2 rV^itnosorfphenyiarnine A^Nitrosodi-n-propylamine Pentachbrophenol Phenol 2.4.5-Trichlorophenol 2.4.6-Trichlorophenol 130* 0.09 ••' 3«J 47,000 b 7,800 b 0.2 210" 0.01 49 120 0.06 *• 0.02 »* 2E-6 •* 0.001 y 5b-j 12 W 0.006 e-li 7440-36-0 7440-38-2 7440-39-3 744041-7 7440-43-9 7440-47-3 7439-92-1 7439-97-6 7440-02-0 7782-49-2 7440-22-4 7440-28-0 7440-62-2 7440-66-6 57-12-5 Antimony Arsenic ^ Barium Beryllium Cadmium & Chromium (6+) Lead Mercury £ Nickel ^ Selenium & Silver Thalium Vanadium Zinc ^ Cyanide 31 b 0.4* 5,500 b 0.1 • 39 b 390 b 400* 23b 1,600 b 390 b 390 b _ c 550 b 23,000 b 1,600 b _c 380" 3.5E+5 b 690 • 920* 140" _ 7 W 6,900 • _ c __ e _- e _ e _ e _ e — k 15' 32' 180* 6' 19' _ 3' 21' 3' _k 0.4' . — * 42,000 b,i _ k _k 1' 3' 18' 0.6' 2 j _ 0.3' 2' 0.3' _k 0.04' _k 4,200 b,i _ k DAF * Dilution and attenuation factor. Screening levels based on human health criteria only. Calculated values correspond to a noncancer hazard quotient of 1. No toxicity criteria available for that route of exposure. Soil saturation concentration (C—t). Calculated values correspond to a cancer risk level of 1 in 1,000,000. Level is at or below Contract Laboratory Program required quantitation limit for Regular Analytical Services (RAS). Chemical-spectre properties are such that this pathway is not of concern at any soil contaminant concentration. A preliminary remediation goal of 1 ppm has been set for PCBs based on Guidance on Remedial Actions for Superfund Sites with PCB Contamination, EPA/540G-90/007, Office of Emergency and Remedial Response, U.S. Environmental Protection Agency, Washington, DC, 1990, and on Agency-wide efforts to manage PCS contamination. 1 SSL for pH of 6.8. ' Ingestion SSL adjusted by a factor of 0.5 to account for dermal exposure. k Soil/water partition coefficients not available at this time. 1 A preliminary remediation goal of 400 mg/kg has been set for lead based on Revised Interim Soil Lead Guidance for CERCLA Sites and RCRA Corrective Action Facilities, OSWER Directive §9355.4-12, Office of SoBd Waste and Emergency Response, U.S. Environmental Protection Agency, Washington, DC, July 14,1994. <fe Indicates potential for soil-plant-human exposure. Levels developed for residential use only: Residential Industrial TUT 008 1031