11 Miss. Code. R. 3-2.2.5 - Tier 3 Evaluation

A. Tier 3 Evaluation Target Risk Level

(1) Human Health

(a) The remediation goal (RG) for each individual contaminant which is a carcinogen must be calculated to attain a Risk Level of 10^-6 (i.e., 1 in a million) or which is a systemic toxicant must be calculated to attain a total hazard quotient of not more than 1, except with regard to a background chemical concentration or a regionally prevalent chemical concentration. In cases where contaminants with corrective action concentrations established through federal and/or state programs (i.e., Safe Drinking Water Act maximum contaminant levels (MCLs)) are present, the MDEQ will determine the appropriate corrective action concentration on a contaminant by contaminant basis. In no event, except with regard to a background chemical concentration, may either:

(1) the cumulative (total) site carcinogenic risk exceed 1 x 10^-4 for carcinogenic CoCs or

(2) the site hazard index (summation of hazard quotients) exceed 3 for non-carcinogenic CoCs affecting the same organ or organ system.

(b) The MDEQ may consider an alternative quantitative or qualitative remediation goal (RG) for each individual contaminant, provided the Applicant can demonstrate to the satisfaction of MDEQ that the attainment of (1) a Risk Level of 10^-6 for each individual carcinogenic contaminant or a total hazard quotient of not more than 1 for each individual systemic toxicant is technically impracticable, except with regard to a background chemical concentration or a regionally prevalent chemical concentration.

(c) The Site risk levels shall be based on high-end exposure (use of high-end values for the exposure point concentration and exposure duration parameters) in the intake calculation of a deterministic risk assessment or 90th percentile of the risk presented in the probabilistic risk assessment. The Site hazard indices and/or quotients shall be based on high-end exposure in a deterministic risk assessment or 90th percentile of the exposure presented in the probabilistic risk assessment.

(2) Ecological

(a) For a Tier 3 Ecological Evaluation, one of the following must be satisfied:

(1) High-end CoC concentrations in the impacted media must be below their respective threshold concentrations or regulatory values that are protective of the ecological receptors of concern or the valued resources to be protected;

(2) Findings from a field survey indicate that there is no readily apparent harm at the site or notable difference (at 95% confidence level) between the site and the potentially impacted ecological receptors;

(3) Individual hazard quotients estimated for the ecological receptors of concern, valued natural resources, or their surrogate species are below unity (1) for each CoC; or

(4) Additional ecological risk evaluations performed under the MDEQ approved work plan conclude that the potential ecological risk is insignificant or readily recoverable.

B. Tier 3 Evaluation (Risk Assessment) Procedures

(1) The Applicant may choose to conduct a site-specific risk assessment (Tier 3), develop and meet site-specific RGs, and have the site-specific RGs approved by MDEQ. This Tier 3 option may entail additional costs to the applicant for MDEQ to subcontract the review of the toxicological and/or risk assessment evaluation. These additional costs shall be paid by the Applicant.

(2) For a human health evaluation of the site or areas within the site (if the site characterization data support such area delineations), the Applicant shall perform risk characterization and present information on risk assessment uncertainty in accordance with the following options:

(a) Deterministic risk assessment according to RAGS - Part A methodology (high-end risk and hazard).

(b) Deterministic risk assessment according to RAGS - Part A (high-end and average risk and hazard).

(c) Probabilistic risk assessment according to EPA's Guiding Principles for Monte Carlo Analysis (EPA/630/R-97/001) or RAGS - Part E methodology to provide probability density function [PDF] for identifying and 90th percentile risk and hazard.

(d) Population cancer risk characterization based on the product of average site carcinogenic risk for an individual and the projected number of exposed individuals. Population non-cancer hazard characterization will be based on the projected number of individuals who are likely to be exposed resulting in the hazard index for each specified systemic effect exceeding one (1).

(3) The human health evaluation report shall include, at a minimum, four components: hazard identification, toxicity assessment, exposure assessment, and characterization of risk and uncertainty.

(a) Hazard identification - This component presents the site history, area(s) where releases have occurred, and the identified site-related chemicals (i.e., CoCs). Site data shall be compiled at the 95% UCL of the mean and compared with the 95% UCL of the mean background data to establish whether the concentration for a detected chemical is above or below background level.

(b) Toxicity assessment - This component requires the identification of CoCs as carcinogenic, non-carcinogenic (causing systemic effects), or both. Toxicity values used in the risk assessment are slope factors and reference doses and must be obtained from:

(1) EPA's Integrated Risk Information System (IRIS),

(2) Health Effects and Assessment Summary Tables (HEAST),

(3) Toxicological Profiles prepared by the Agency for Toxic Substances and Disease Registry (ATSDR), and

(4) Other peer-reviewed reference sources or literature approved by MDEQ.

(c) Exposure Assessment - This component estimates the type and magnitude of exposures to the CoCs that are present at or migrating from the Site. The results of the exposure assessment are combined with chemical-specific toxicity information to characterize potential risks. The general procedure for conducting an exposure assessment is outlined in Chapter 6 of RAGS.

(d) Characterization of Risk and Uncertainty - This section describes the final step of the health risk assessment process. In this step, the toxicity and exposure assessments are summarized and integrated into quantitative and qualitative expressions of risk. Major assumptions, scientific judgments, and, to the extent possible, estimates of the uncertainties embodied in the assessment are also presented.

(4) Non-carcinogens that act on the same organ systems can be identified in Table 2, EPA's Soil Screening Guidance: Technical Background Document (EPA/540/R-95/128) or Appendix A, Tables E, Title 35 Illinois Administrative Code Part 742, as amended. The Applicant must identify the uncertainty associated with each toxicity value. Toxicity values with a high degree of uncertainty should not be used in the risk assessment.

(5) The Applicant shall provide information on the CoC exposure point concentrations (EPCs), activities, and exposure routes that lead to exposure. Site-specific information in combination with relevant information found in EPA's Exposure Factors Handbook (Volumes I, II, and III, EPA's National Center for Environmental Assessment, March 1998), AIHC's Exposure Factors Sourcebook, or other peer-reviewed literature approved by MDEQ may be used to assess exposure. At a minimum, the exposure assessment shall include:

(a) a SCEM to provide the basis for determining which exposure pathways are complete; and

(b) specific input values and their basis (references) for exposure parameters such as the exposure frequency (days per year), duration (number of years), and absorption factors.

(6) Carcinogenic risk and non-carcinogenic hazard posed by the CoCs shall be estimated for the Site or areas within the Site where past releases have occurred. Risks from all complete exposure pathways (i.e., incidental ingestion, dermal contact, inhalation of volatiles or particulates), and contaminated on-site food sources (indirect exposure) shall be characterized, as identified in the SCEM.

(a) Carcinogenic risks from individual CoCs for all complete exposure pathways shall be summed to provide the total site carcinogenic risk (cumulative excess lifetime cancer risk to an individual).

(b) Non-carcinogenic hazards (hazard quotients) from individual CoCs that act on the same organ or organ system for all complete exposure pathways shall be summed to provide the site hazard indices.

(7) The following risk assessment protocols shall be followed for assessing special chemicals or categories of chemicals, unless otherwise approved by MDEQ:

(a) Chlorinated dioxins and dibenzofurans - The evaluation of chlorinated dioxins and dibenzofurans must be consistent with EPA Region IV's Human Health Risk Assessment Bulletins: Supplement to RAGS (http://www.epa.gov/region04/waste/ots/healtbul.htm).

(b) Lead and lead-based compounds - For the assessment of risk to children (if such receptors are reasonably anticipated to be present under the current and future use scenarios), the EPA's Integrated Exposure Uptake Biokinetic Model (IEUBK) (EPA/540/R-93/081) shall be used. If adults are the receptors, the Adult Lead Model published in the "Recommendations of the Technical Review Workgroup for Lead for an Interim Approach to Assessing Risks Associated with Adult Exposures to Lead in Soil" (December 1996) by the EPA Technical Review Workgroup (TRW) shall be used to assess the hazard of lead exposure.

(c) Polycyclic aromatic hydrocarbons (PAHs) - The evaluation of PAHs must be consistent with EPA Region IV's Human Health Risk Assessment Bulletins: Supplement to RAGS (http://www.epa.gov/region04/waste/ots/healtbul.htm).

(d) Polychlorinated biphenyls (PCBs) - A slope factor of 7.7 (mg/kg/day)-1 shall be used for total PCBs. If congener-specific or group-specific (mono-through deca-chlorinated) biphenyls are analyzed and quantified using Modified EPA Method 1668, the slope factor to be used will be 2.0 (mg/kg/day)-1 for tri-, tetra-, penta-, hexa-, and hepta-chlorinated PCBs. Slope factors lower than 2.0 (mg/kg/day)-1may be used if there are low concentrations of 2,3,7,8-substituted PCBs). The lowestslope factor of 0.4 (mg/kg/day)-1 can be used if 2,3,7,8-substituted PCBs are not present. The Applicant shall bear the burden of providing documentation to MDEQ to justify using slope factors lower than 7.7 (mg/kg/day)^-1 in the risk assessment report.

(e) Radioactive materials or radionuclides - The risk assessment of radioactive materials shall be in accordance with Chapter 10 of RAGS -Part A. Other methodologies (e.g., dose reconstruction for exposure assessment) shall be approved by MDEQ on a case-by-case basis.

C. Tier 3 Ecological Risk Evaluation Procedures

(1) For the entire Site or areas within the Site (if the site physical characteristics support delineations of different ecosystems), the Applicant shall perform screening and/or more in-depth ecological risk evaluations and present uncertainty associated with the evaluations in accordance with the following options:

(a) Identify the ecological receptors of concern and compare CoC concentrations in the potentially impacted media with their respective benchmark or threshold values that are protective of the receptors of ecological concern. The initial screening levels and procedures are available in the EPA Region 4 Ecological Risk Assessment Bulletins- Supplement to RAGS (http://www.epa.gov/region04/waste/ots/ecolbul.htm).

(b) Additional ecological benchmark values are available from EPA (e.g., Office of Technical Services Supplemental Guidance to RAGs: Region IV), U.S. Fish and Wildlife Service, the National Atmospheric and Oceanic Administration, or other values in peer-reviewed literature, as appropriate.

(c) Conduct biological field surveys for species diversity and abundance in the potentially impacted area and a reference (background) area and compare both survey results to determine whether there are significant differences at 95% level of confidence.

(d) Identify assessment and measurement endpoints and perform a deterministic risk evaluation on the receptors of ecological concern or their indicator species by the hazard quotient method.

(e) Perform additional ecological risk evaluations based on an MDEQ-approved work plan submitted by the Applicant that is consistent with the EPA's Framework for Ecological Risk Assessment guidance and its subsequent update.

(2) A deterministic risk evaluation shall include a minimum of four components: problem formulation, ecological effects assessment, exposure assessment, and characterization of risk and uncertainty.

(a) Problem formulation - This component presents the site history (including documented incidents of readily apparent harm), physical characteristics, area(s) where releases have occurred, and identified site-related chemicals (i.e., CoCs).This component also proposes and provides the rationale for identifying any ecological receptors of concern and valued resources present on site that may be impacted by the CoCs. The basis for assessment and measurement endpoint(s) selection should be provided to MDEQ.

(b) Ecological effects assessment - This component requires the identification of potential or known acute and chronic toxic effects of the CoCs on the ecological receptors of concern, valued resources, and any surrogate species proposed as the measurement endpoints. Dose-response data shall be obtained from EPA data bases or other federal/state databases approved by MDEQ.

(c) Exposure assessment - This component presents the SCEM and explains how the CoCs are released, transported, bioconcentrated or biomagnified in organisms, and exposed to the ecological receptors of concern or valued resources to be protected. Where appropriate, behavior patterns or reasonable assumptions should be used to estimate daily intake of the CoCs.

(d) Characterization of risk and uncertainty - This component shall present the risk assessment results and the underlying uncertainty associated with the assessment method employed. If a quotient method is used, the hazard quotients shall be estimated for the ecological receptors of concern or their surrogates. Risk may be characterized qualitatively by the weight-of-evidence approach based on professional judgment. This component should identify types and magnitude of potential effects anticipated, the spatial and temporal extent of the effects, significance of the effects on the ecosystems, and recovery potential.

(3) A Tier 3 ecological risk evaluation shall be presented in the following report format: problem formulation, approach and rationale, and presentation of results, uncertainties, and recommendations. In interpreting these evaluation findings, the Applicant should consider the effects of natural succession, non-site related impacts (e.g., farm or urban runoff), and seasonal changes on the data or observations collected. The report format may vary based on MDEQ requirements of the ecological risk evaluation work plan.

D. Tier 3 Risk Assessment Data Requirements

(1) The basic procedure for the assessment of human health and ecological receptors of concern for a Tier 3 risk assessment shall be to obtain representative site characterization data in order to perform a screening or more in-depth risk assessment. Specific requirements for performing a Tier 3 risk assessment include, but are not limited to, the following:

(a) Site characterization data shall be obtained in accordance with the MDEQ-approved Quality Assurance Project Plan (QAPP). The Applicant must demonstrate that the Site has been adequately characterized to delineate the nature and extent of contamination. The scope of the site investigation shall be based on the considerations set forth below.

(1) Previous field investigations should be used to define the SCEM and identify data gaps or uncertainty for the nature and extent of the site characterization under this site investigation phase.

(2) Field analytical data may be used to identify areas of contamination and to supplement fixed-laboratory analyses if the Applicant can demonstrate that the field analytical data are comparable to fixed laboratory data by regression or co-relational analyses and meet DQO requirements for precision, accuracy, and reproducibility. A minimum of 10% of the collected samples shall be fixed-laboratory data to demonstrate correlation. Samples must be collected from the areas exhibiting the highest field concentrations and analyzed at a fixed laboratory.

(3) Areas with distinct high concentrations of site-related chemicals shall be segregated from other areas for data compilation purposes. Additional field characterization of high-concentration areas or areas with buried wastes is necessary to support remedial design.

(4) The RAGS procedure for the selection of CoCs shall be followed to properly characterize the Site. The Applicant should exclude background chemicals, laboratory and field contaminants or artifacts, and chemicals that are essential nutrients present at or below the recommended daily allowance intake levels.

(5) All reported data shall be in compliance with the DQOs established in the QAPP. In addition to data review, the data will be validated by a qualified technical individual, familiar with data validation, at the rate of at least 10% or as otherwise specified by MDEQ. The Applicant shall provide data review and validation summaries in the Site Characterization Report.

Notes

11 Miss. Code. R. 3-2.2.5

Miss. Code Ann. §§ 49-35-1, et seq., 49-2-9(1)(b), 49-17-17, 17-17-1, et seq., 49-2-1, et seq. and 49-17-1, et seq.

Amended 12/4/2023