Voluntary Remediation Program - Risk Assessment Guidance

1.0 Introduction

The regulatory basis for performing risk assessments under the Virginia Voluntary Remediation Program (VRP) is found in the Voluntary Remediation Regulations section, 9 VAC 20-160-70(A)(1)(a) of the Virginia Administrative Code. The risk assessment should be included in the site characterization report and should include an evaluation of the risks to human health and the environment posed by the release or threatened release of a contaminant into the environment. If the risk assessment shows that a removal or other remedial action is necessary, a proposed set of remediation levels as described in section 9 VAC 20-160-90 should also be included. If the remedial action includes engineering and/or institutional controls, a thorough discussion of said controls and their expected efficacy should be provided.

Risk assessments under the VRP generally follow the methodology described in Risk Assessment Guidance for Superfund (RAGS)  and can be tailored to specific site conditions. The risk assessment process consists of four major steps. These steps are data collection and evaluation, exposure assessment, toxicity assessment, and risk characterization.  Once these four steps of risk assessment are completed risk management decisions regarding how risk will be mitigated to acceptable ranges are made.  These steps, as applied to the VRP, are described in the following sections. This guidance applies primarily to the human health risk assessment, although there may be some overlap with ecological risk assessment. VRP guidance for ecological risk assessment will be developed separately. The U.S. Environmental Protection Agency, however, has issued its own guidance in Ecological Risk Assessment Guidance for Superfund: Process for Designing and Conducting Ecological Risk Assessments.  Also see the EPA Region 3 Ecological Risk Assessment website for screening values and other guidance for ecological risk assessments. If an ecological risk assessment is required it is highly recommended to coordinate with the Virginia DEQ project manager and risk assessor before proceeding.

Tables 1.1a and 1.1b and all the Medium-Specific Exposure Point Concentration Summary Tables (Tables 1.2-1.6) may be used by the participant to present the data.The participant may choose to use a different format to present the risk assessment information, however screening level, quantitative risk assessment and site-specific background comparison (if applicable) VURAM outputs should be included in the submittals in entirety. These are the preferred method of data presentation and will greatly expedite reviews. Participants should provide an explanation of how the data were derived and rationales for all site specific model inputs along with the VURAM outputs. Incomplete submissions could result in delay of risk assessment based decision-making All screening and quantitative risk assessment tables provided in the previous VRP guidance has been replaced by VURAM. The latest version of VURAM supersedes all of previous versions therefore the participant must ensure that the most current version of VURAM is used for risk assessments. 

Two other types of links are also provided in this guidance. Links in bold type lead to the glossary, where the highlighted term is defined. Links in normal type lead to VURAM and its User's Guidance, either to other sections of the report or to risk assessment information sources located elsewhere on the World Wide Web. Links in italic type also lead to other sources of risk assessment information.

2.0 Data Collection and Evaluation

During the data collection and evaluation step of the risk assessmentsite data relevant to human health and ecological evaluation are gathered and analyzed. In addition, potential contaminants of concern are identified. Virginia DEQ suggests that VRP participants meet with VRP and Risk Assessment staff in the beginning stages of a project, and periodically throughout as is helpful, to better focus time and resources and help result in thorough submittals.

2.1 Sampling Methodology

The sampling performed during the site characterization should be planned such that the resulting data will support a risk assessment. In addition to source sampling, samples should be collected at potential exposure points and at relevant site boundaries. In some cases, off-site samples may be needed. The VRP regulations require that the site characterization contain a delineation of the nature and extent of releases to all media. All media (except biota) should be adequately sampled unless a sufficient rationale is presented that sampling is not required.

The Virginia Department of Environmental Quality (Virginia VDEQ) does not have detailed guidance on sampling methodology. The following documents, however, may be helpful in preparing sampling plans for VRP sites.

The following sections briefly describe some of the issues relating to sampling methodology that may be relevant to VRP sites. It may be helpful to prepare a work plan for VRP and Risk Assessment staff review in advance of sample collection and analysis.  This collaboration can be helpful in lessening overall project time by creating efficiency at the document review stage.

2.1.1 Soil

Both surface and subsurface soil should be sampled. Unless land use controls are put in place that prevent intrusive soil activities, VRP considers subsurface as well as surface soil to be potentially accessible for risk assessment purposes. During construction or excavation activities, subsurface soil could be brought to the surface and become available for exposure. If subsurface contaminants  are at greater depths than reasonably expected to be reached during a construction or utility project, those samples may be eliminated from the risk assessment. As a general default, VRP assumes that contamination down to 15 feet could be encountered and should be included in the risk assessment. In some cases, such as  sites  with anticipated high-rise construction or subsurface parking garages, contaminants at greater than 15 feet will need to be included. In addition, in some cases, samples deeper than 15 feet may be required in order to assess the potential for contaminant migration to groundwater. If excavation activities have occurred prior to risk assessment, Virginia DEQ recommends that a representative number of post-excavation confirmation soil samples be collected from the bottom and sidewalls and analyzed for relevant COC’s.  Please not that TPH, DRO, and GRO samples will not suffice given that no such values exist for risk assessment calculations.  Whereas these may suffice for other DEQ Programs, they won’t suffice for the VRP. Please not that TPH, DRO, and GRO samples will not suffice given that no such values exist for risk assessment calculations.  Whereas these may suffice for other Virginia DEQ Programs, they will not suffice for the VRP.

2.1.2 Groundwater

Groundwater samples should be collected at the majority of VRP sites. A sufficient number of monitoring wells should be installed in order to delineate groundwater flow direction and both the horizontal and vertical extent of the contaminant plume. Any existing production wells or drinking water wells should also be sampled. At most sites, multiple rounds of groundwater monitoring will be needed in order to characterize the dynamics of the plume over time. In addition to contaminant sampling, hydrogeologic properties that may be needed to model contaminant migration should also be determined.

2.1.2.1 Filtered versus Unfiltered Samples

Groundwater samples collected for use in VRP risk assessments should be unfiltered. VRP Tier II screening levels are based on maximum contaminant levels (MCLs), which are based on unfiltered concentrations. (Note: "Tiers" are explained in Section 2.4.) In addition, site-specific groundwater exposure scenarios such as construction work are also based on total concentrations.

2.1.2.2 Direct Push versus Monitoring Wells

Direct push sampling is often helpful for determining the extent of contamination at a site  or for locating monitoring wells. However, there are concerns regarding the reproducibility of this well construction method. DEQ recommends that monitoring wells should be installed to provide the data quality desirable for a sufficient quantitative risk assessment. DEQ prefers that direct push samples not be used in the quantitative risk assessment for groundwater. However, any direct push samples that were taken for site characterization purposes should be discussed qualitatively in the text of the risk assessment.

2.1.3 Surface Water

Water samples should be collected from any surface water body (including rivers, streams, lakes, ponds, impoundments and estuaries) potentially receiving surface or groundwater discharge from a site. Based on Site Conceptual Model, if collection and analysis of surface water samples was deemed unnecessary please provide rationale in the Risk Assessment Report.

2.1.3.1 Filtered versus Unfiltered Samples for Inorganics

Ideally, both filtered and unfiltered samples should be taken. The Virginia Water Quality Standards for Surface Water are based on dissolved (filtered) concentrations. However total concentrations (unfiltered) are more appropriate for assessing dermal exposure to surface water. If the participant proposes taking one or the other, then unfiltered samples are recommended. Note that this will result in a conservative comparison to standards.

2.1.4 Sediment

Sediment samples should be collected from any surface water body (including rivers, streams, lakes, ponds, impoundments and estuaries) potentially receiving surface or groundwater discharge from a site. Based on Site Conceptual Model, if collection and analysis of surface water samples was deemed unnecessary please provide rationale in the Risk Assessment Report.

2.1.5 Air

Air samples may be needed at some VRP sites. Sites that have volatile organic contamination in the soil or groundwater are of particular concern. However, there are many other potential sources of volatile organic contaminants in indoor air. Therefore, the VRP recommends that indoor air sampling be performed only if the subsurface characterization indicates the potential for migration to indoor air. In most cases, the subsurface investigation should include collection of subslab soil gas samples. If subslab concentrations indicate the potential for unacceptable risk, the participant may opt to do air sampling to confirm or refute the results.

There is considerable temporal and spatial variability in the results of both soil vapor and indoor air sampling.  Therefore the VRP recommends that several rounds of sampling at several locations be conducted for these media in order to capture the temporal and spatial variability. As always please contact VRP and Risk Assessment Staff to better help focus sampling and analysis Please see Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils, Appendices E and I, and Vapor Intrusion Pathway: A Practical Guidance for further information on sampling considerations for these media.

2.1.6 Biota

A limited number of VRP sites may require biota samples. If commercial or recreational fishing takes place on or adjacent to the site, sampling of edible aquatic organisms may be needed. However, the participant may prefer to model bioconcentration from surface water and/or sediment to estimate concentrations in aquatic organisms rather than sample initially. If modeling predicts an unacceptable risk, sampling may be needed. If the site is adjacent to an agricultural area or home gardens, sampling of produce may be needed.

2.2 Analytical Methods

The VRP regulations require the use of Test Methods for Evaluating Solid Waste, USEPA SW-846, revised December 1987. It is recommended that any applicable updates to SW-846 be used.  The TO-15 method is recommended for soil vapor and indoor air samples.

The analyses should be targeted to the types of contaminants that would be suspected at the site based on site history. Industrial and Analytical Profile Fact Sheets from Brownfields Technical Resources from the U.S. Environmental Protection Agency Region III office may be used to determine the types of analyses to select.

If the site contaminants are unknown, such as for some landfills, the analyses should include metals and cyanide, volatile organic compounds (VOCs), semivolatile organic compounds (SVOCs), and pesticides/PCBs. Methods providing only a total for a certain group of contaminant -- such as total petroleum hydrocarbons (TPH) -- cannot be used for risk assessment.

2.3 Quality Assurance/Quality Control

The participant is responsible for insuring that adequate field and laboratory quality assurance/quality control (QA/QC) procedures are followed. The quality assurance plan and QA/QC sample results must be made available upon request for review by the VRP staff. Participants should be aware that QA/QC could become a critical issue if the site were to become the subject of litigation. The EPA Region III Brownfields Quality Assurance Project Plan Template may be helpful for planning QA/QC for VRP projects.

2.3.1 Detection Limits

Detection limit is a generic term that refers to the lowest amount that can be distinguished from the normal "noise" of an instrument or method. Before choosing a laboratory, the participant should review laboratory performance data, such as method detection limits (MDLs) and instrument detection limits (IDLs), to insure that they can routinely detect most contaminants at the VRP Tier II screening levels. (See Section 2.4.2 for a discussion of Tier II screening levels.) For VRP risk assessments, the participant should request that the laboratory report the limit of quantitation (LOQ) or the sample quantitation limit (SQL) Since LOQs and SQLs take into account sample characteristics, sample preparation, and analytical adjustments, they are the most appropriate limits for Tier II screening and quantitative risk assessment. More information on detection and quantitation limits can be found in the USEPA document, Guidance for Data Usability in Risk Assessment (Part A).

2.4 Screening for Chemicals of Potential Concern

The maximum detected concentration should be compared to the VRP Tier I and/or Tier II screening levels as described below. If contaminant concentrations exceed the screening levels, the participant may proceed to the site-specific quantitative risk assessment (Tier III). In some cases it may be more beneficial to the participant, however, to remediate the site to Tier I or Tier II levels. For example, if the participant is seeking unrestricted closure, a site-specific risk assessment would not necessarily result in less stringent remediation levels. If all contaminant concentrations in all media are less than the Tier I background levels and/or Tier II screening levels no further risk assessment is required.

Tier I screening is not required. Participants may choose to begin with Tier II screening without consulting the VRP project manager. If, however, participants seek to go directly to Tier III screening, they must first obtain the project manager's consent.

2.4.1 Tier I

In Tier I screeningcontaminant concentrations from the site for all media of concern are compared to those from background samples collected from nearby areas that have not been affected by the substances of concern. If concentrations from the affected area exceed background levels, the participant may choose to employ Tier II or Tier III screening methods.

Tier I screening should be based on site-specific samples from an unimpacted area of the site or nearby property. An upgradient location may not always be an appropriate background location because VRP sites must also consider contamination that enters the site from an upgradient source. In general, background screening is applicable only to inorganic contaminants that are also naturally occurring.

 A description of the methodology and locations used in obtaining background samples must also be submitted. VURAM includes “site specific background comparison” module. If Tier I screening is conducted at a site, site specific background comparison VURAM module output must be included in the submittal. Refer VURAM User’s Guide on how to use the background comparison module. Please note maximum site concentration should be compared to the background concentration(s).

2.4.2 Tier II

In Tier II screeningcontaminant concentrations from the site for all media of concern are compared to medium-specific values obtained from published sources such as the USEPA Region III Risk-Based Screening Tables, the USEPA Soil Screening Guidancemaximum contaminant levels or other action levels established by the Safe Drinking Water Act and the National Primary Drinking Water Regulations.

Tier II screening should be reserved for unrestricted-use sites. Tier II levels for soil and groundwater are based on the assumption of residential exposure. However, sites such as schools, day care centers, hospitals, nursing homes, parks, and agricultural areas should be considered unrestricted for screening purposes.

2.4.2.1 Soil

Tier II levels for soil are based on the lower of the USEPA Region III Regional Screening Level Table or the values derived from the USEPA Soil Screening Level (SSL) guidance for transfer from soil to air or groundwater.The screening level is the lower of cancinogenic (risk of 10-5) and noncarcinogenic (HQ of 0.1) value. For non-carcinogens the target hazard quotient has been adjusted to 0.1 to allow for potential additive toxicity of multiple contaminants. This is equivalent to dividing the risk-based concentration (RBC) by 10. Assuming there are ten or fewer non-carcinogenic contaminants, this adjustment will result in a hazard index (sum of hazard quotients) less than or equal to one. (See Section 5.2 for a discussion of the hazard quotient and hazard index.)

If there are fewer than 10 non-carcinogenic contaminants that exceed the Tier II level, the participant may choose to recalculate the Tier II screening level. In such a case, the RBC or SSL should be divided by the number of contaminants exceeding the Tier II screening level. This is equivalent to adjusting the target hazard quotient so that the target hazard index does not exceed one. If the Tier II screening level is recalculated, the participant should insure that the non-carcinogenic screening level does not exceed a screening level based on carcinogenic effects.

VRP staff used the EPA's 2002 Supplemental Soil Screening Guidance  to calculate SSLs for Virginia. The SSL site provides climatic data for nearby cities in each of the three climate zones that cover Virginia -- Raleigh, N.C., in zone VI; Huntington,W.Va., in zone VII; and Philadelphia, Pa., in zone VIII. The climatic data resulting in the most conservative SSL were chosen. Climatic data from Huntington were used to calculate SSLs for inhalation of volatiles since these resulted in the most conservative (lowest) SSLs. Data from Philadelphia were used to calculate SSLs for inhalation of fugitive dust since these resulted in the most conservative SSL. SSLs were calculated for both carcinogenic and non-carcinogenic effects and the most conservative of the two values was chosen. Values based on non-carcinogenic effects were divided by 10. The lower of the SSL for volatiles or the SSL for fugitive dust was then chosen as the SSL for inhalation. For non-carcinogens, the SSL for migration to groundwater was divided by 10 only if the SSL was based on a health-based number and not on an MCL. The lower of the SSL for inhalation or the SSL for migration to groundwater was then chosen as the SSL value. The SSL was then compared to the Region III RBC value. The lower of the two values was then chosen as the Tier II screening level.

The SSL for migration to groundwater was divided by 10 to allow for potential additivity of multiple contaminants only if the SSL was based on a health based number and not on a maximum contaminant level. The lower of the SSL for inhalation or the SSL for migration to groundwater was then chosen as the SSL value. The SSL value was then compared to the Region III RBC table. The lower of the two values was then chosen as the Tier II screening value.

Note that a contaminant that exceeds only the SSL for transfer to groundwater may still be screened out under Tier II if groundwater results (based on adequate sampling) indicate that transfer is not occurring at levels of concern. Use VURAM to conduct Tier II soil screening. VURAM output will indicate whether a given contaminant is a COPC and should be retained for quantitative risk assessment . Refer VURAM User’s Guide on how to use the screening module.

2.4.2.2 Groundwater

The Tier II screening values for groundwater are based on federal (MCLs) established by the Safe Drinking Water Act and the National Primary Drinking Water Regulations. Lead and copper do not have an MCL but they have a treatment technology action level that should be used for screening. For contaminants that do not have an MCL the EPA Region III Regional Screening Levels for Tap Water should be used. For non-carcinogens the target hazard quotient has been adjusted to 0.1 to allow for potential additive toxicity of multiple contaminants; the hazard index for multiple contaminants should not exceed 1. The MCLs may be found in Drinking Water Regulations and Health Advisories. VURAM output will indicate whether a given contaminant is of potential concern and should be retained for quantitative risk assessment. Refer VURAM User’s Guide on how to use the groundwater screening module.

2.4.2.3 Surface Water

By regulation, the Tier II screening values for surface water are based on the Virginia Water Quality Standards (WQS). For contaminants that do not have a Virginia WQS, the Federal Water Quality Criteria (WQC) may be used if available. The Virginia WQS are designated for either protection of aquatic life or protection of human health. Although this guidance primarily addresses human health risk assessments, the aquatic life standards have been included in the screening tables since they would be applicable to any surface water body. The Federal water quality criteria for aquatic life included on these tables are based on the criterion continuous concentration (CCC). The lower of either the human health or the aquatic life WQS has been chosen as the Tier II screening level. Consult the River Basin Section Tables in the WQS 9 VAC 25-260-360 to determine whether a specific water body should be screened as a public water supply. See 9 VAC 25-260-140 to determine whether a specific surface water body should be screened as marine or fresh water. Surface Water screening can be conducted in VURAM. Select fresh and/or marine water, depending on the surface water designation. Public water supply screening is included in the fresh water screening output. Refer VURAM User’s Guide on how to use the surface water screening module.

If neither a Virginia WQS nor a Federal WQC are available for a particular contaminant detected in surface water, the participant should perform a literature search to determine if alternative screening values are available. If alternative values are not available, the detected contaminants should be carried through to a Tier III risk assessment.

2.4.2.4 Sediment

VRP Tier II screening values for sediment were obtained by multiplying USEPA Region III residential soil Regional Screening Level values by a factor of 10 to account for decreased exposure to sediments. For non-carcinogens, however, the target hazard quotient has been adjusted to 0.1 (the RBC has been divided by 10) so that additive toxicity will not result in a hazard index greater than one for multiple contaminants. Thus the Tier II screening concentration for sediments for non-carcinogens is equal to the unadjusted soil RSL, while the Tier II concentration for carcinogens is equal to the RBC times 10. Sediment screening can be conducted in VURAM. The VURAM output will indicate whether a given contaminant is of potential concern and should be retained for quantitative risk assessment. Refer VURAM User’s Guide on how to use the sediment  screening module.

2.4.3 Tier III

Tier III screening is based upon site-specific analysis that weighs current and potential exposure scenarios for the population(s) of concern and characteristics of the affected media.

Tier III screening should be used for sites that are or will be formally restricted to a specified use. Tier III cannot be used for unrestricted-use sites. The participant should consult with the VRP project manager to determine whether Tier III screening is appropriate for a particular site.

2.4.3.1 Soil

The Tier III screening values for commercial/industrial soils (Table 2.9) should be used when soil concentrations exceed Tier II levels and appropriate restrictions are in place or formally proposed. Residential use of the site must be prohibited. Since the SSLs for migration to groundwater are not included as Tier III screening levels, the site must either have a restriction prohibiting the use of groundwater or have sufficient groundwater samples to demonstrate that groundwater has not been impacted and will not be impacted in the future. This should include a demonstration that groundwater has not and will not migrate off-site above Tier II screening levels.

The Tier III screening levels for commercial/industrial soils are the lower of either the EPA Region III industrial soil RBC or the SSL for migration to air. The SSLs for migration to air have been adjusted to commercial/industrial exposure factors. VURAM output will indicate whether a given contaminant is of potential concern and should be retained for quantitative risk assessment. Refer VURAM User’s Guide on how to use the sediment  screening module.

2.4.3.2 Groundwater

For groundwater contaminants that exceed Tier II screening levels, the participant may choose to perform Tier III screening based on the receptors of concern and the proposed restrictions for the site. For sites where land use will not be restricted but the use of groundwater will be prohibited, the receptors of concern could be residents, commercial/industrial and construction/utility workers.

Residents would be a concern if the contaminants retained after Tier II screening could volatilize into enclosed spaces. However, groundwater concentrations should only be used for screening the vapor intrusion pathway for sites with no current buildings (and the potential for future development) or for assessing the potential for off-site impacts.  

Construction/utility workers would be receptors of concern at any site where intrusive activities are not expressly prohibited. Two scenarios are possible for evaluating construction worker exposure to groundwater. In the first scenario, the depth to groundwater is below the level of the construction trench. Therefore, the construction worker would not have direct contact with the groundwater by incidental ingestion or dermal exposure. However, the worker could inhale vapors that migrate from the groundwater through the soil and collect in the trench. In the second scenario, the construction trench reaches the groundwater, causing groundwater to pool at the bottom. The construction worker may then be exposed to groundwater by incidental ingestion, dermal contact and/or inhalation. In the VURAM screening module, groundwater tab, the participant should choose the appropriate scenario to compare the maximum groundwater concentration to the Tier III groundwater concentration. The participant should also provide documentation on the depth to groundwater at the site to verify that the appropriate scenario was used. These Tier III values were derived from an emissions equation and a box model combined with the Virginia DEQ default exposure factors for construction workers. See sections 3.2.2 and 6.1 for more detail.

For sites that have or will have a prohibition against residential development and a prohibition against groundwater use, both commercial/industrial workers and construction workers would be receptors of concern.  As noted above, groundwater concentrations should only be used for screening the vapor intrusion pathway for sites with no current buildings (and the potential for future development) or for assessing the potential for off-site impacts. VURAM groundwater screening module will indicate whether groundwater concentration(s) of a given contaminant is of potential concern for vapor intrusion purposes and should be retained for quantitative risk assessment. Refer VURAM User’s Guide on how to use the groundwater screening module.

2.4.3.3 Soil Gas

The following are the screening processes used to evaluate on- and off-site exposures:

On-Site Exposure

If a release of a volatile compound is suspected to have occurred within the boundaries of the VRP site, then subslab soil gas should be collected in any potentially affected buildings. If there are no buildings in the area of the release, follow the off-site exposure screening method below.

1. If the subslab soil gas data is above the VRP Tier III Vapor Intrusion  screening criteria then a site-specific vapor intrusion evaluation will be necessary (see ITRC 2007, Site Investigation Phase).

2. If the subslab soil gas is less than the Tier III Vapor Intrusion screening criteria, it can be assumed that unacceptable vapor risks are not present for on-site buildings.

Off-Site Exposure

The general method for screening off-site exposure risks, or on-site vapor intrusion risks where the use of subslab soil gas data is impracticable (e.g., no buildings are present in the area of the release), is:

1. If the appropriate groundwater concentration is below the Tier III groundwater screening criteria, then no further vapor intrusion evaluation is necessary.

2. If the groundwater concentration is above the screening criteria, deep soil gas results may be used as a screening tool. Deep soil gas is soil gas collected above the capillary fringe and not less than 5 feet below the surface. It is preferred that deep soil gas is collected at a depth of at least 10 feet unless the capillary fringe is shallower. If deep soil gas concentrations are less than the screening criteria then further vapor intrusion may not be necessary. VURAM Air screening module will indicate whether groundwater concentration(s) of a given contaminant is of potential concern for vapor intrusion purposes and should be retained for quantitative risk assessment. Refer VURAM User’s Guide on how to use the air screening module.

2.5 Chemical-Specific Issues

Virginia DEQ's approach to assessing chromium concentrations has been to conservatively assume that total chromium is all hexavalent chromium. If chromium concentrations drive a cleanup decision, Virginia DEQ recommends that chromium samples be analyzed for the specific valence states to verify or refute this assumption.

The current screening value for lead in soils is 400 mg/kg for unrestricted-use sites. This screening level is based on the Revised Interim Soil Lead Guidance for CERCLA Sites and RCRA Corrective Action Facilities (OSWER Directive 9355.4-12, July 14, 1994). Due to unique aspects of lead modeling, it is not included in quantitative risk assessment module of VURAM.

The current screening value for lead in soils is 800 mg/kg for restricted-use sites. Please see the Adult Lead Methodology (ALM) Frequently Asked Questions (FAQ) web site for further information on the basis for the commercial/industrial screening level. Also see Recommendations of the Technical Review Workgroup for Lead for an Approach to Assessing Risks Associated with Adult Exposures to Lead in Soil for more information on assessing risks from adult exposure to lead.Due to unique aspects of lead modeling, it is not included in quantitative risk assessment module of VURAM.

If TPH levels in soil samples are more than 100 ppm, then the samples must be analyzed for metals, VOC's and SVOC's.

There are no risk-based screening levels for some of the possible chemicals of concern. In these cases proxy screening levels based on substances with similar chemical structures are substituted. Please refer to VURAM User's Guide Appendix 5 for a complete list.

Currently, the VRP Tier II and Tier III screening tables contain chemicals on the Target Analyte List (TAL) and Target Compound List (TCL). The TAL and TCL were developed for chemicals that are routinely sampled at Superfund sites. Sampling for VRP sites may (and often should) include contaminants that are not included on these lists. For chemicals that are not included on the VRP screening tables, the participant should derive screening levels based on the methods and references described in the previous sections.

3.0 Exposure Assessment

The goals of the exposure assessment step are to analyze contaminant releases; to identify exposed populations; to identify potential exposure pathways; and to estimate exposure concentrations and contaminant intakes for each pathway.

3.1 Selection of Exposure Pathways

Table 3.1a presents the on-site exposure pathways that routinely should be considered under VRP risk assessments. The participant should provide a rationale for eliminating or selecting a pathway for evaluation. It is anticipated that some of the receptors listed on the table will be ruled out. Note that a commitment to place an institutional control on the property may be used to rule out specific pathways and/or receptors on site. Anticipated engineering controls, personal protective equipment or remedial actions should not be used to eliminate pathways or receptors. Note that restrictions may be medium specific. For example, a site may require a restriction on groundwater use but may be found to be otherwise acceptable for residential development.

Table 3.1b presents the off-site exposure pathways that should be routinely considered. The participant should provide a rationale for eliminating or selecting a pathway for evaluation. Unlike the on-site pathways, institutional controls may not be used to rule out off-site exposure pathways since a participant generally does not have control of off-site properties. The rationale for selecting or excluding an off-site pathway may be based on sampling, modeling, or knowledge of past site history.

Also note that additional pathways may need to be evaluated for some sites. For example, ingestion of contaminated fruits, vegetables, or meats may be a concern if the site is adjacent to an agricultural area.

Applicable spreadsheets:
Table 1.1a Selection of Exposure Pathways Onsite
Table 1.1b Selection of Exposure Pathways Offsite

 

3.1.1 Unrestricted Sites

3.1.1.1 Media

The exposure assessment should consider the potential for direct exposure to groundwater, soil, surface water and sediment for any contaminants that exceed Tier II screening values. It should also consider the potential for vapor intrusion, inter-media transfer and off-site migration.

3.1.1.2 Receptors

For unrestricted sites, exposures to an adult and child residential receptor must be evaluated. Exposure of a child and adult recreational receptor must also be evaluated if surface water and sediment are media of concern.

3.1.1.3 Routes of Exposure

For each receptor, exposure by ingestion (including inadvertent ingestion), dermal contact and inhalation must be evaluated. For sites that impact surface water that supports edible aquatic organisms, ingestion of aquatic organisms by both a child and adult must be evaluated.

3.1.2 Restricted Sites

3.1.2.1 Media

The exposure assessment should consider the potential for direct exposure to groundwater, surface and subsurface soil, surface water and sediment for any contaminants that exceed Tier III screening values. It should also consider the potential for vapor intrusion, inter-media transfer and off-site migration. If the participant proposes to limit intrusive activities at the site to utility work, contaminated soils below the depth at which the utility work would take place may be excluded from the subsurface soil exposure assessment. In order to eliminate this exposure pathway, the participant must provide a detailed description of the utility lines in the area and assurance that new utilities will not be added in the future in contaminated areas.

3.1.2.2 Receptors

For restricted sites, residential receptor exposure to soil may be ruled out if a land use control will be placed on the site prohibiting residential development and there is no indication of off-site migration.

For groundwater, residential exposure to drinking water may be ruled out if a use restriction will be placed on the site prohibiting potable use and there is no indication of off-site migration. Participants choosing to cite property-use restrictions as an exposure mitigation action must provide formal documentation in support. A site-specific use restriction restricting future uses of the groundwater will be required. This will ensure adequate notification to future property owners and allow for the immunity associated with successful program completion to run with the property and thereby facilitate future transfers of the property.

A well survey should be performed within at least a one-mile radius of the site. The survey should include contacting the local agency with authority for approving well installation to obtain records on existing wells in the area. The survey should also include a visual inspection of the surrounding properties to determine whether there are any undocumented wells. In addition, the potential for future use of the groundwater must be considered. Any restrictions on future groundwater use should be described.

If the participant desires to eliminate off-site use of groundwater from consideration in the risk assessment, documentation from the relevant locality must be provided to demonstrate prohibitions on the use of the impacted aquifer. This documentation must be provided in the form of formal correspondence from the appropriate local entity to Virginia DEQ, and would include, at a minimum, either a copy of a local ordinance prohibiting or restricting groundwater use in the areas affected by the contaminated groundwater, a domestic well surveillance plan, or other comparable mechanism approved by the appropriate local agency with jurisdiction over groundwater well installations in the affected area. It is the participant's responsibility to facilitate the submission of this correspondence to Virginia DEQ.

A construction/utility worker should be evaluated unless there will be a deed restriction prohibiting intrusive activities. A commercial/industrial worker should be evaluated unless the site is inactive and there will be a prohibition on future use of the site.

For sites that either are or may be zoned for recreational use (e.g. parks, playgrounds, etc.), exposures to adult and child recreational users should be evaluated. Exposures to adult and child trespassers should be evaluated on sites that are not or will not be specifically set aside for recreational use.

3.1.2.3 Routes of Exposure

For each receptor, exposure by ingestion (including inadvertent ingestion), dermal contact and inhalation must be evaluated. For sites that impact surface water that supports edible aquatic organisms, ingestion of aquatic organisms by both a child and adult must be evaluated.

3.2 Determining Exposure Point Concentrations

For VRP risk assessments either the maximum contaminant concentration or the 95% upper confidence limit (UCL) on the arithmetic mean should be used as the exposure point concentration (EPC) for each medium. If the UCL is used, the calculation must be based on the appropriate data distribution. The data distribution should be checked using the Shapiro-Wilk method [Shapiro, S.S., and M.B. Wilk, 1965. An analysis of variance test for normality (complete samples), Biometrika 52:591-611]. If the 95% UCL is greater than the maximum concentration, then the maximum concentration should be used as the EPC. Consult Calculating Upper Confidence Limits for Exposure Point Concentrations at Hazardous Waste Sites for details on calculating UCL's. Also see https://www.epa.gov/land-research/proucl-software to download EPA's ProUCL software to calculate UCLs.  For samples that are non-detect, substitute 1/2 of the SQL when calculating the UCL. For duplicate samples, the results should be averaged. Exposure point concentrations should be presented on Tables 3.2-3.5 for each medium along with a summary of the data on which the EPC's were based. The participant should record the results of exposure point concentration calculations in the appropriate table for the medium of concern.

Applicable spreadsheets:
Medium-Specific Exposure Point Concentration Summary:
Table 1.2 Groundwater Table 1.3 Soil
Table 1.4 Surface Water Table 1.5 Sediment

3.2.1 Exposure Modeling

When the EPC is based on inter-media transfer (e.g., the exposure medium is different from the original medium) or off-site migration, modeling -- from groundwater to indoor air, for example -- may be used. For most exposure media, established models are available for estimating EPC's. Some examples of models that may be used are:

Soil to air particulates: Soil Screening Guidance (USEPA 1999c)

Soil to air volatiles: Soil Screening Guidance (USEPA 1999c)

Groundwater to shower air:Forster and Chrostowsi Chrostowski (2003)

Groundwater to outdoor air: ASTM E2081 - 00(2015) Standard Guide for Risk-Based Corrective Action  (Previous standard ASTM PS104-98)

Vapor intrusion: VISL Calculator (EPA 2014)

Groundwater to surface water: AT123D (Yeh 1981)

Soil to groundwater: SESOIL

Surface Water Migration: EXAMSII (Burns, L.A., Cline, D.M., and Lassiter, R.P., 1982. Exposure Analysis Modeling System (EXAMS): User Manual and System Documentation.  EPA-600/3-82-023, U.S. EPA)

The EPC resulting from modeling should be provided in Table 3.6. Documentation of the model inputs should also be provided along with a rationale for any site-specific parameters used. The participant should record the results of exposure point concentration calculations in the appropriate table for the medium of concern.

Applicable spreadsheets:
Medium-Specific Exposure Point Concentration Summary:
Table 3.6 Modeling results

3.2.2 Exposure of Workers to Volatiles in a Construction/Utility Trench

There are no well-established models available for estimating migration of volatiles from groundwater into a construction/utility trench.Virginia DEQ recommends the following approach -- based upon a combination of a vadose zone model to estimate volatilization of gases from contaminated groundwater into a trench, and a box model to estimate dispersion of the contaminants from the air inside the trench into the above-ground atmosphere -- to estimate the EPC for air in a construction trench. Two different methods are used to estimate volatilization into the trench. The choice of method depends on the site-specific depth to groundwater, i.e. if the groundwater is less than or greater than 15 feet.  Equations that were part of previous Tables 3.7 and 3.8 from VRP website have been incorporated into VURAM as part of groundwater tab for construction worker therefore user does not need to calculate trench air concentrations. The equations and related information on how to calculate airborne concentration of a contaminant in a trench are included in VURAM User’s Guide.  If site specific default values are used, then the participant should obtain prior approval from DEQ for use of such values and then calculate exposure point concentrations for air in a construction trench according to the method described above. References should be provided for the site-specific values used.

3.3 Determining Chemical Intakes and Exposure Concentrations

In this step of the exposure assessment, chemical-specific intake levels are calculated for each receptor group for the dermal and ingestion exposure pathways and the exposure concentration is calculated for each receptor group for the inhalation exposure pathway. Intakes are expressed as a mass of chemical per unit body weight per unit time (e.g., mg/kg-day.)  Exposure concentrations are expressed as a mass of a chemical per unit volume (e.g., mg/m3). Exposure concentrations are considered time-weighted average concentrations derived from measured or modeled contaminant concentrations in air at a site, adjusted based on the characteristics of the exposure scenario being evaluated.

Equations and recommended exposure factors for determining chronic daily intake levels and exposure concentrations for each medium, receptor, and exposure route are presented Sections 3.3.1 through 3.3.4 of the VURAM User’s Guide as well as EPA RSL table User’s Guide.  Exposure scenarios or factors that may require further explanation are discussed briefly in the following sections and can also be found in VURAM User’s guide . Note that the pathways selected in Table 3.1a or 3.1b need to be included in VURAM Calculations. If the participant proposes to use an exposure factor other than the EPA RSL/VURAM default, a reference and rationale should be provided for DEQ’s approval and acceptance. Ensure to add the results of the manual calculations to the site-wide hazard/risk calculation in the risk assessment report. Screening tables 2.5 through 2.14 are included in VURAM screening module. VURAM screening output will include screening levels and results for all receptors. Tables 3.10- through 3.23 from previous VRP guidance are included in VURAM in a different format: VURAM ‘Study Area’ lets user to select from resident, commercial/industrial, construction, recreator, trespasser; ‘Receptor’ includes adult and child; routes of exposure (ingestion, inhalation, dermal) for applicable media; and six media tabs (Soil, groundwater, air, surface water, sediment, and food) lets user select appropriate media that matches table 3.1a or Table 3.1b. Please refer to ‘media calculations table’ and related text in VURAM User’s Guide to obtain more information on these options and use VURAM to perform calculations. EPA RSL defaults and chemical parameters (variables) are used in VURAM where available. DEQ will periodically update these values and equations to match latest EPA approaches. While VURAM does not provide date of EPA RSL update used, the version number of VURAM reflects the most recent update of RSL values (chemicals parameters as well as exposure defaults) incorporated in the VURAM. Latest version of VURAM supersedes all previous versions therefore the participant must ensure that the most current version of VURAM is used for risk assessment.

3.3.1. Aquatic Organisms/Food

The food tab in VURAM provides four food groups: Fish and Shellfish, Meat and Dairy, eggs, and Fruits and Vegetables. The users can input media concentration to any or all of these food groups. Note that the food calculations follow EPA RSL equation for fish ingestion and for noncarcinogens, calculates hazard for adult receptor. In order to ensure potential hazard for child receptor is not omitted from the calculations, in the risk assessment report the same hazard values for food are used for adult and child to calculate media-specific and child specific hazard. Refer to VURAM User’s Guide section titled ‘Understanding the Report’ for more details. 

3.3.2 Inhalation

VURAM incorporates inhalation exposure to soil, groundwater and sediment for applicable receptors in media specific calculation. The Air tab in VURAM can be used to perform quantitative risk assessment using measured of calculated air concentrations (e.g., deep soil gas, shallow soil gas, subslab soil gas, groundwater-to-indoor air). Because quantitative risk assessment for vapor intrusion relies on multiple lines of evidence approach and involves higher degree of professional judgment, VURAM currently does not preselect sampled/calculated air concentration option. DEQ highly recommends the use of the most conservative (i.e. health protective) value for quantitative risk assessment. Refer to VURAM Users Guide subsections titled ‘Calculation Media Specific Pages’ and ‘Media Concentrations’ for more details. Consult RP project manager and Risk Assessor for more discussion on including vapor intrusion in site-wide quantitative risk assessment.

3.4 Exposure Factors

Default values incorporated in VURAM are obtained from EPA RSL website where available and are provided in VURAM  User’s Guide. DEQ specific vales are marked as such.

3.4.1 Residents

The residential scenario is based on total exposure duration of 26 years. The default assumption is 6 years of childhood exposure and 20 years of adult exposure. If groundwater use is not restricted, exposure to drinking water must be assessed.  This includes inhalation of vapors during showering.  If groundwater use is restricted, the potential for vapor intrusion of volatile contaminants to indoor air must be assessed via air tab of VURAM.

For carcinogens that act via a mutagenic mode of action, special adjustments are needed to account for susceptibility during early life.  Therefore exposure to these chemicals is assessed separately for ages 0-2, 2-6, 6-16, and 16-26 years.  Exposure durations for these chemicals are adjusted accordingly.  The separate calculations have been incorporated into the VURAM algorithm using EPA RSL equations that are included in  VURAM User’s Guide for quick reference.

3.4.2. Construction/Utility Workers

The VRP default construction scenario is based on a worker working on a construction project for 125 days per year for 1 year. The worker is arbitrarily assumed to be exposed to groundwater for 4 hours a day. If the groundwater is 15 feet deep or less, the worker is assumed to be exposed by inadvertent ingestion, dermal contact, and inhalation. If the groundwater is greater than 15 feet deep, the worker is assumed to be exposed by inhalation only. The ingestion rate of water was arbitrarily set at 0.02 liters per day. This is two orders of magnitude lower than the daily drinking water ingestion rate and is intended to account for splashing and hand-to-mouth contact. The EPA default soil ingestion rate of 330 mg/day is used in this scenario. Refer to VURAM User’s Guide for more details. Risks to Construction/Utility workers are based on subchronic exposures and toxicity data to  account for the more short-term nature of the exposure scenario.

3.4.3 Commercial/Industrial Workers

VRP assumes that a commercial/industrial worker could come into contact with contaminated soil through outdoor activities. Since soil can be a primary source of indoor dust, the VRP also assumes that indoor workers could be exposed to soil contaminants. Therefore EPA RSL exposure defaults for composite workers are used. Refer to VURAM User’s Guide for more details. In VURAM quantitative risk assessment module, select appropriate groundwater use declaration: Beneficial or Restricted use. If an onsite groundwater use restriction has been agreed upon, restricted use can be selected and groundwater pathway need not be evaluated.

3.4.4 Recreational Visitors and Trespassers

The recreational scenario should be used for sites that are intended for recreational use or could be developed for recreational use in the future. The trespasser scenario should be used for sites that are not intended for recreational use but that may be accessible to trespassers either now or in the future. The only difference between recreational visitors and trespassers is in the exposure frequency and VURAM provides option to select either recreator or trespasser. The VRP assumes that exposures to contaminated surface water occur primarily by swimming. Refer to Appendix 2 and 4 of VURAM User’s Guide for more details. A site-specific exposure frequency should be chosen after consultation with the VRP project manager or risk assessor.

4.0 Toxicity Assessment

Qualitative and quantitative toxicity information is collected and appropriate toxicity values are determined during the toxicity assessment step. Toxicity factors for each contaminant of concern have been selected based on the hierarchy described in Human Health Toxicity Values in Superfund Risk Assessments and used for EPA RSL development. The toxicity values to be used in the risk assessment can be viewed by scrolling right on ‘chemical List’ box on ‘Setup’ screen of the VURAM. This screen replaces previous VRP tables 4., 4.1a, and 4.2. While the ‘Chemical List’ window displays toxicity values and some other chemical specific information, VURAM database includes all the chemicals parameters available in various spreadsheets in RSL Composite tables. VURAM contains subchronic toxicity values from EPA RSL online calculator. Since DEQ will be updating toxicity information in VURAM, the participant is not responsible for cross-referencing VURAM values against EPA RSL. The participant, however, is responsible for ensuring that the most recent version of VURAM that is available of DEQ website is used for risk assessment. The most recent version of VURAM available on DEQ website will supersede all previous versions.   For contaminants with both carcinogenic (oral slope factors (SFO) and inhalation unit risks (IUR)) and non-carcinogenic (oral reference doses (RfDs) and reference concentrations (RfCs)), toxicity factors, the toxicity assessment is conducted for both carcinogenic and non-carcinogenic effects.

5.0 Risk Characterization

Cancer risks and non-cancer hazard quotients are estimated during the risk characterization step. In addition, uncertainty analysis is conducted and risk information is summarized. After the data are entered in VURAM, the results of the calculations of non-cancer hazard indices and cancer risks are provided in the VURAM report. Please refer to VURAM User’s Guide section titled ‘Understanding the Report’ for more details. The VURAM report eliminates the need to use previous tables. VURAM report must be submitted in its entirety (including the last page(s) that show exposure defaults) as part of risk assessment report. An incomplete VURAM report is not acceptable and will result in delay of risk assessment related decision making.  

For contaminants with both carcinogenic and non-carcinogenic toxicity factors, the risk characterization is conducted for both carcinogenic and non-carcinogenic effects.

5.1 Carcinogens

Risks due to exposure to multiple chemicals are assumed to be additive. A lifetime risk value is provided in the VURAM report by combining the risks from childhood exposure to the risks from adult exposure. The National Contingency Plan (NCP) (U. S. EPA, 1990) cites an acceptable range of 10-6 to 10-4 for total carcinogenic risk with a point of departure of 10-6.

As noted above, for carcinogens that act via a mutagenic mode of action, special adjustments are needed to account for increased susceptibility during early life. Therefore exposure to these chemicals is assessed separately for ages 0-2, 2-6, 6-16, and 16-26 years. The age-dependent adjustment factors (ADAFs) are applied to the risk calculations for each age group to give additional weight to early life stages.  The ADAFs are as follows:

Age            ADAF

0-2              10

2-4                3

4-16              3

16 and up     1

These separate calculations have been incorporated into VURAM calculations. For additional information please see Guidelines for Carcinogen Risk Assessment and Supplemental Guidance for Assessing Susceptibility from Early-Life Exposure to Carcinogens.

5.2 Non-Carcinogens

As a conservative step, the hazard quotients for individual chemicals are assumed to be additive. The sum of the hazard quotients is called a hazard index. A hazard index above 1 indicates that the potential for adverse effects cannot be ruled out.  Segregating the HI based only on target organs or systems is a simplification of HI. Segregation of hazard indices by unique effect, mechanism of action and toxicity can be complex and time-consuming because it is necessary to identify all of the major effects and target organs for each chemical and then classify the chemicals according to target organ(s) or mechanism of action and thus is not recommended. Please contact DEQ project manager and/or risk assessor for more discussions.

5.3 Uncertainty Analysis

The risk assessment should include a section describing the uncertainties inherent in each of the steps of the assessment. A discussion of whether the uncertainty would tend to over-estimate or under-estimate risk should be included. The uncertainty section should discuss the likelihood of any future scenarios that were assessed. It should also include a discussion of the sensitivity and variability of model inputs and provide a rationale for the values that were used. Chemicals that do not have all parameters to calculate hazard/risk but are detected in any sampled media must be included in this section. VURAM does NOT conduct uncertainty analysis

6.0 Determining Remediation Levels

If the risk assessment indicates that there are unacceptable risks, VURAM calculates remediation levels to lower the risk to acceptable levels for the residential and industrial study areas. Refer to VURAM User’s Guide section titled ‘Understanding the Report’ for more details. Note that remediation goals provided in VURAM report are not binding and can be used for risk-based management decisions or may be used as is as remediation goals. Please consult with the DEQ project manager for more details.

VURAM sets a default individual goal of 10-6 but the user may select a different goal after consultation with DEQ. If a participant wishes to deviate from the default risk goal when setting remediation levels for a site, a detailed rationale should be provided for DEQ review and approval. Remediation levels should not result in a site-wide cumulative risk greater than 10-4. For non-carcinogens, an unacceptable risk is defined as a hazard index greater than 1 for contaminants.  If remediation level for both carcinogenic and non-carcinogenic effect is calculated, the final remediation goal will be lower of the two. For soil, and groundwater as applicable, recommended acceptable concentration data must be evaluated for fate and transport. VURAM does NOT include fate and transport evaluations. If contamination is expected to reach groundwater and/or surface water, then fate and transport based calculated groundwater /surface water contaminant concentration(s) can be entered into the risk assessment portion of VURAM to assess if the predicted concentration will be within acceptable hazard/risk level. If predicted concentrations fail acceptable hazard/risk levels, the soil/groundwater acceptable concentrations may need to be revised to meet fate and transport based requirements. If contamination will not reach groundwater and/or surface water within 30 years at unacceptable levels, then the concentrations of COPCs in soil are acceptable according to human health risk based criteria. Please contact project manager and/or risk assessor for more discussions.

7.0 References

ASTM-E2081-00. 2015. Standard Guide for Risk-Based Corrective Action. ASTM International.

40 C.F.R. 300 (1990). National Oil and Hazardous Substances Pollution Contingency Plan.

40 C.F.R.  141 (2000). National Primary Drinking Water Regulations.

US EPA and Cook, M.B. (2003) Human Health Toxicity Values in Superfund Risk Assessments. US EPA. OSWER Directive 9285.7-53.

Foster, Sarah A., and Paul C. Chrostowski. 1987. Inhalation Exposures to Volatile Organic Contaminants in the Shower. In The Proceedings of the 80th Annual Meeting of the Air Pollution Control Association (APCA), June 21-26, New York. Air Pollution Control Association.

BonazountasBonazountasand Wagner. 1981. Unsaturated Soil Zone Transport and Fate Model (SESOIL). US EPA. Modification by Hetrick et al. ORNL. 1993; Modification by Schneiker, R. ESCI. 1997.

ITRC, 2007. Vapor Intrusion Pathway: A Practical Guidance. Interstate Technology and Regulatory Council. January 2007.

42 U.S.C. 103. 1998. Comprehensive Environmental Response, Compensation and Liability Act.4

US EPA.1989. Risk Assessment Guidance for Superfund: Volume I -- Human Health Evaluation Manual (Part A). Interim Final. US Environmental Protection Agency. Office of Emergency and Remedial Response. EPA/540/1-89/002.

Burns, L.A., Cline, D.M and Lassiter, R.P. 192. Exposure Analysis Modeling System (EXAMS): User Manual and System Documentation. US EPA. EPA-600/3-82-023.

Hoang, K. T. 1992. Dermal Exposure Assessment: Principles and Applications. US EPA, Office of Health and Environmental Assessment. EPA/600/8-91/011B (archived).

Shapiro, S.S. and Wilk, M.B. 1965. ‘An Analysis of Variance Test for Normality (Complete Samples)’, Biometrika, 52, pp. 591–611. doi: 10.2307/2333709.

US EPA. 1992. Guidance for Performing Site Inspections under CERCLA. US EPA Office of Emergency and Remedial Response. EPA/540/R-92/021.

US EPA.1992. Supplemental Guidance to RAGS: Calculating the Concentration Term. US Environmental Protection Agency. US EPA Office of Solid Waste and Emergency Response. Publication 9285.7-081.

US EPA.1994. Revised Interim Soil Lead Guidance for CERCLA Sites and RCRA Corrective Action Facilities. US EPA Office of Solid Waste and Emergency Response. EPA/540/F-94/043; OSWER Directive #935514-12.

US EPA. 1996. Soil Screening Guidance: Technical Background Document Second Edition. US EPA Office of Solid Waste and Emergency Response. EPA/540/R95/128.

US EPA.1996. Soil Screening Guidance: User's Guide Second Edition. US EPA Office of Solid Waste and Emergency Response. OSWER Publication 9355.4-23.

US EPA. 2002. Supplemental Guidance for Developing Soil Screening Levels for Superfund Sites. US EPA Office of Solid Waste and Emergency Response. OSWER Publication 9322.4-24

US EPA.2012. Drinking Water Standards and Health Advisories Tables. US EPA Office of Science and Technology.

USEPA.1997. Ecological Risk Assessment Guidance for Superfund: Process for Designing and Conducting Ecological Risk Assessments Interim Final. US EPA Environmental Response Team. EPA 540-R-97-006; OSWER 9285; PB97-963211.

US EPA. 1998. Hazardous Waste Test Methods / SW-846. US EPA Office of Solid Waste. SW-846.

US EPA. Regional Screening Levels (RSLs). US EPA National Center for Environmental Assessment.

US EPA. Superfund Soil Screening Guidance. US EPA Office of Solid Waste and Emergency Management.

US EPA. 2011. Integrated Risk Information System (IRIS) Glossary. US EPA Office of Research and Development.

US EPA. 2004. Risk Assessment Guidance for Superfund: Volume I -- Human Health

Evaluation Manual (Part E, Supplemental Guidance for Dermal Risk Assessment) Final. US

EPA Office of Emergency and Remedial Response.

US EPA. 2002.Calculating Upper Confidence Limits for Exposure Point Concentrations at Hazardous Waste Sites. US EPA Office of Solid Waste and Emergency Response. OSWER 9285.6-10.

US EPA. Lead at Superfund Sites: Frequent Questions from Risk Assessors on the Adult Lead Methodology (ALM). US EPA Office of Solid Waste and Emergency Response.

US EPA. 2003. Recommendations of the Technical Review Workgroup for Lead for an Approach to Assessing Risks Associated with Adult Exposures to Lead in Soil Final. US EPA Technical Review Workgroup for Lead. EPA-540-R-03-001.)

US EPA. National Recommended Water Quality Criteria - Aquatic Life Criteria Table.

US EPA (2016b) ProUCL Software.

US EPA. Ground Water and Drinking Water: Table of Regulated Drinking Water Contaminants.

US EPA. Water Quality Criteria.

US EPA. Risk Assessment: Ecological Risk Assessment.

US EPA. Risk Assessment: Risk assessment guidance for Superfund (RAGS): Part A.

US EPA. About EPA:  EPA Region 3 (Mid-Atlantic).

US EPA. 1989. Risk Assessment Guidance for Superfund Volume I Human Health Evaluation Manual (Part A) Interim Final. US EPA Office of Emergency and Remedial Response. EPA/540/1-89/002.

US EPA. 1991. Guidance for Data Usability in Risk Assessment (Part A) Final. US EPA Office of Research and Development. EPA/540/R-92/003.

US EPA. Drinking Water Regulations and Contaminants.

US EPA. Safe Drinking Water Act (SDWA).

US EPA. Brownfields Technical Assistance and Research.

US EPA. Superfund.

US EPA. 2015. OSWER Technical Guide for Assessing and Mitigating the Vapor Intrusion Pathway from Subsurface Vapor Sources to Indoor Air. US EPA Office of Solid Waste and Emergency Response. OSWER Publication 9200.2-154.

US EPA. 1990. Brownfields Technical Resources: Industrial & Analytical Profiles. US EPA Region III.

US EPA. 2001. BROWNFIELDS Quality Assurance Project Plan Template Interim Final. US EPA Region III.

US EPA. 2005. Guidelines for Carcinogen Risk Assessment. US EPA Risk Assessment Forum. EPA/630/P-03/001F.

U. S. EPA. 2005b. Supplemental Guidance for Assessing Susceptibility from Early-Life Exposure to Carcinogens.

9 VAC 20-60 Virginia Hazardous Waste Management Regulations.

9 VAC 20-80 Solid Waste Management Regulations (Repealed).

9 VAC 20-160 Voluntary Remediation Regulations.

9 VAC 25-260 Virginia Water Quality Standards.

Virginia Department of Environmental Quality (DEQ). 2016. Virginia Unified Risk Assessment Model (VURAM) User’s Guide.

Yeh, G.T. 1981. Analytical Transient One-, Two-, and Three-Dimensional (AT123D) Simulation of Waste Transport in the Aquifer System. Oak Ridge National Laboratory (ORNL). Significant modifications by Seymor. 1982; Darryl Holman. 1984; Howard Trussell. 1986; Scheneiker ESCI. 1997.

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Environmental Quality
P.O. Box 1105
Richmond, VA 23218
(804) 698-4000


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