Comparison of Existing Contamination to Risk Reduction Standards 391-3-19-.07
** Note: The Rules for Hazardous Site Response (Rules) have been modified effective September 25, 2018, and include changes to the methods for calculating Risk Reduction Standards (RRS). In general, users may refer to EPA’s Regional Screening Level calculator using a target carcinogenic risk of 1E-5 and a hazard quotient of 1 for the direct contact values. EPD is developing the Georgia Risk Assessment Guidance with stakeholder input, which will provide additional details. This webpage has been updated in the interim, including tables of select Type 1 and 3 RRS.**
- Description/Risk Types
- RRS Process Chart
- Type 1 and Type 3 Default RRS
- Adult Lead Model
- Toxicity Factors and Physical Properties
- Common Mistakes
- Ecological Health
Risk Reduction Standard (RRS) values should be calculated for each regulated substance. The chosen RRS “Type” will depend on site use and the potential of exposure. There are 5 “Types” of RRS values:
- Type 1 RRS will pose no significant risk on the basis of standardized exposure assumptions and defined risk level for residential properties.
- Type 2 RRS will pose no significant risk on the basis of site-specific risk assessment for residential properties.
- Type 3 RRS will pose no significant risk on the basis of standardized exposure assumptions and defined risk level for non-residential properties.
- Type 4 RRS will pose no significant risk on the basis of site-specific risk assessment for non-residential properties.
- Type 5 RRS are allowed only in instances where Type 1-4 standards are not appropriate. This standard allows contamination to remain provided the principal threats at the site are controlled by engineering and institutional controls. Under the Rules, Type 5 is only appropriate for sites where it is determined to not be practical to remove source area (landfills, etc.). Institutional controls should not be substituted for active remedial measures. However, the Voluntary Remediation Program (VRP) Act provides an alternative to the Rules and does not include the impracticability requirement. ** NOTE: Please contact a compliance officer at our office (404-657-8600) for additional information regarding the minimum requirements relating to a Type 5 risk reduction standard and/or additional VRP guidance. **
The Compliance Status Report (CSR) should include a discussion on the calculation of RRS values that were selected for the site, a discussion of why that “Type(s)” was/were selected, and how the regulated substances compare to the RRS values. If non-default values are used in the calculation of a Type 2 or 4 RRS, then the discussion must include a description of why these values are appropriate for use at your site. Specific tables that should be included are:
- If RRS are not taken from EPD provided RRS tables, a table containing all exposure parameters and toxicity factors, with references, used in risk-based calculations, as well as, the equation and the results.
- A table comparing the Maximum Detected Concentrations (MDCs) in soil and groundwater to their respective RRS values.
A site where the concentration of regulated substances in soil or groundwater exceeds the RRS values does not meet state cleanup standards and a Corrective Action Plan is required.
** Note: Please be advised that calculating site-specific RRS (Type 2 and/or Type 4) may NOT always result in higher cleanup standards. **
HSRA RRS Process Chart
** Note: Descriptions relating to the calculations of the risk reduction standards have been simplified wherever possible to address common regulated substances; however, this guidance does not supersede the Rules for Hazardous Site Response. In the event of conflict, the Rules for Hazardous Site Response take precedence. **
Type 1 and 3 Default RRS
** Note: These tables are not an exhaustive list of Regulated Substance; see Appendix 1 of the Rules for the list. Furthermore, EPD has compiled this dataset using the information available to them. While quality assurance efforts have been undertaken, EPD does not guarantee the accuracy, reliability, or completeness of these RRS, which are subject to change without notice. EPD provides this data for convenience and without warranty, either express or implied. All submitted RRS must be approved by EPD, and these tables do not supersede the Rules for Hazardous Site Response. In the event of conflict, the Rules for Hazardous Site Response take precedence. Please contact the Risk Assessment Unit at 404.657.8600 if you believe that inaccurate or incomplete data is presented in these tables.**
Adult Lead Model
As part of the 2018 Rule change, Type 4 (non-residential) RRS for lead in soil are now calculated using EPA’s Adult Lead Model (ALM). The formulas and inputs are provided in Appendix IV of the Rules. Unfortunately, extraneous symbols and errors were introduced in the formula during the Rule change process, which will be corrected in the next revision. In the interim, the correct equations are provided below:
The Type 4 soil direct-contact RRS for lead using central tendency values for a commercial/industrial worker (surface soils) is 1050 mg/kg and for an excavation worker (subsurface soils) is 1278 mg/kg.. These values are calculated in accordance with Rule 391-3-19-.07(9)(d)2.(i) and 3.(i) , and site-specific exposure values may be proposed. A site-specific leaching value must be calculated in accordance with Rule 391-3-19-.07(9)(d)1. to determine the final RRS value.
For additional information, EPA’s ALM guidance and spreadsheet for calculating values may be found at www.epa.gov/superfund/lead-superfund-sites-software-and-users-manuals.
Toxicity Factors and Physical Properties
- Toxicity Factors:
For toxicity assessment, EPD adopts EPA’s Office of Solid Waste and Emergency Response (OSWER) recommended hierarchy of toxicity information (OSWER Directive 9285.7-53, 2003). Note that EPA uses this toxicity data hierarchy for the Regional Screening Level (RSL) tables. See http://www.epa.gov/risk/risk-based-screening-table-generic-tables. A benefit of these tables is that they act as single source of information concerning toxicity factors and chemical specific parameters used in the risk assessment process. Please note that the information in this table is periodically updated. If a value for only one of the two variables in a variable pair (RfDo/RfC or SFo/IUR) is not available for a substance, the term containing that variable in an equation can be omitted or equated to zero. If neither value is available for a variable pair, a concentration cannot be calculated with the RAGS equations unless an appropriate surrogate compound is available for use in assessing its risk.
- Inhalation Reference Concentrations and Inhalation Unit Risk Factors:
Consistent with U.S. EPA RAGS, Part F (2009), the inhalation exposure pathway has been updated to allow for direct use of inhalation toxicity values as concentrations in lieu of doses when assessing cancer and non-cancer inhalation risks. As a result, it is no longer necessary to apply a conversion method to convert from concentration to dose metric. Instead, the inhalation equation from RAGS, Part F when used allows for use of toxicity concentrations as they appear in EPA’s Regional Screening Levels table.
- Physical Properties:
Sources for Chemical Specific Properties for soil screening values
- Regional Chemical Specific Properties:
- Soil Screening Guidance:
Superfund Chemical Data Matrix:
- Failure to use the default groundwater standards for the Type 1 RRS for groundwater. For Type 1 groundwater RRS values, concentrations shall not exceed those listed in Table 1 of Appendix III of the rules. For regulated substances not listed in this table, concentrations shall not exceed the background or detection limit concentration.
- Failure to include concentrations listed in Table 2 of Appendix III (http://rules.sos.state.ga.us/GAC/Appendix%28391-3-19%29) when calculating the Type 1 RRS for metals in soil.
- Failure to address the protection of groundwater via migration from soil as it pertains to soil Risk Reduction Standard (RRS) values.
- Improperly calculating Soil Screening Level (SSL) values:
- Improperly calculating site-specific distribution coefficient (Kd).
- Using a referenced Kd value from an improper reference.
- Not properly determining the dilution attenuation factor when calculating soil concentrations protective of leaching for site-specific (Type 2 and 4) Risk Reduction Standards.
- Using an foc of 0.02 instead of 0.002
- Not utilizing the toxicity factor hierarchy and/or using incorrect input parameters for RAGS equations. For derivation of the default RRS, the values provided in Table 3 of Appendix III should be used.
- For Type 2 and 4 RRS values, failing to provide supporting documentation for site-specific exposure assumptions.
- Failure to eliminate the inhalation pathway for non-volatile regulated substances in groundwater. In groundwater, if the regulated substance is not volatile, then the inhalation pathway is incomplete and can be removed from the RAGS equation.
- Failure to eliminate the inhalation pathway for non-volatile regulated substances in soil. In soil, if the regulated substance is not volatile, then the inhalation pathway due to volatiles is incomplete and the (1/VF) term can be removed from the RAGS equation. However, the inhalation pathway due to particulates (1/PEF) must be addressed.
- For non-Carcinogenic risk, not setting the Averaging Time (AT) equal to the Exposure Duration (ED). For example, if the exposure duration for a construction worker is 6 months, then the averaging time for these workers would be 182 days/year (i.e., 0.5 years x 365 days/year).
- Failure to run the Integrated Exposure Uptake Biokinetic (IEUBK) Model for Lead in children in the determination of the overall Soil Type 2 RRS value for Lead. Please provide all model input and output parameters for review.
- Failure to run the Standard Adult Lead Model (ALM) in the determination of the overall Soil Type 4 RRS value for Lead. Please provide all model input and output parameters for review.
- Entering a groundwater concentration for lead in the IEUBK model that exceeds the federal action limit of 15 micrograms/liter.
- Using the notification concentrations as de facto soil risk reduction standards.
- Based on the 8 Step Ecological Risk Assessment Process for Superfund Sites:(http://www.epa.gov/risk/ecological-risk-assessment)
- Process is divided into two stages:
- Screening Level Ecological Risk Assessment (SLERA) – Steps 1 and 2
- Baseline Ecological Risk Assessment (BERA) – Steps 3 thru 8
- SLERA: involves the comparison of Regulated Substances’ Maximum Detected Concentrations (MDCs) with appropriate Ecological Screening Values (ESVs) and approved Background Values (Inorganics only). This comparison results in a Hazard Quotient (HQ) [HQ = MDC/ESV].
- Appropriate ESVs for use at this stage with respect to exposure media
- Surface Water, Soil, Sediment:
- Georgia In-Stream Water Quality Criteria (391-3-6-.03(5)): http://rules.sos.ga.gov/GAC/391-3-6-.03.
- US EPA Region 4 Freshwater, Soil, Sediment: http://www.epa.gov/sites/production/files/2015-09/documents/r4_era_guidance_document_draft_final_8-25-2015.pdf
- Surface Water, Soil, Sediment:
- Any regulated substance, which lacks a Water Quality Criteria (WQC) or a Region 4 ESV or has a Hazard Quotient (HQ) greater than 1.0, must be carried forward in the risk assessment process (Steps 3 thru 8).
- Appropriate ESVs for use at this stage with respect to exposure media
- BERA: includes Step 3A, the Refinement step, which allows for the use of:
- 95% Upper Confidence Limit (UCL) of the mean as the Exposure Point Concentration (EPC) rather than MDCs.
- Refinement or Alternate Screening Values (ASVs) for surface water, sediment and soil should be obtained from Tables 1a through 3 of Region 4 EPA's Ecological Risk Assessment Supplemental Guidance.
- Any regulated substance, which lacks an Alternate Screening Value (ASV) or has Hazard Quotient (HQ) greater than 1.0, must be carried forward in the risk assessment process (Steps 4 thru 8).