11 Miss. Code. R. 3-2.2.4 - Tier 2 Evaluation

A. Tier 2 Evaluation Target Risk Level

For human health, the remediation goal (RG) for each individual contaminant which is (1) a carcinogen must be calculated to attain a Risk Level of 10-6 (i.e.,1 in a million) and (2) 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 without the use of both an engineering control and an institutional control.

B. Tier 2 Evaluation Options

(1) Tier 2 Evaluation is a more in-depth evaluation of site-specific conditions beyond the Tier 1 Evaluation methodology. The Tier 2 Evaluation may include, but is not limited to, an evaluation of site-specific conditions by:

(a) determining the Upper Confidence Limit (UCL) of the Mean for a CoC utilizing statistical methods and comparing the UCL to the Tier 1 TRGs,

(b) comparing EPCs to calculated background chemical concentrations,

(c) comparing EPCs to calculated regionally prevalent chemical concentrations,

(d) utilizing site-specific variables (i.e., exposure frequency, exposure duration, etc.) to calculate site-specific RGs,

(e) eliminating or minimizing exposure to contaminants,

(e) conducting an analysis of Petroleum Hydrocarbons using TPH Fractioning, or

(f) utilizing other methods approved by MDEQ.

(1) Statistical Methods - If the Applicant can demonstrate to the satisfaction of MDEQ that the UCL of the Mean for a CoC utilizing statistical methods is less than the Tier 1 TRG for that CoC, this calculated value may be used instead of the highest CoC concentration. The UCL of the Mean is then compared to the Tier 1 TRG to evaluate remedial options. The Applicant must demonstrate to the satisfaction of MDEQ that the data are statistically normal or can be statistically normalized

(i) The methodology used to determine the UCL of the Mean should be conducted in accordance with the EPA's Supplemental Guidance to RAGS: Calculating the Concentration Term (EPA, 992a), or another method approved by MDEQ.

(2) Site Background - CoC concentrations may be compared to site background chemical concentrations to evaluate appropriate remedial actions at the Site.

(i) To establish background chemical concentrations, the Brownfield Applicant may collect samples from locations outside of the influence of known contaminated areas and regionally prevalent chemicals (both vertically and horizontally), as approved by MDEQ and must analyze these samples using the same analytical methods as the CoC analyses.

(ii) If the Applicant can establish that the background chemical concentration of a CoC is higher than the Tier 1 TRG concentration for that CoC listed in Appendix A, the Applicant shall have the option of using the background chemical concentration as the Remedial Goal (RG).

(iii) Remediation of a CoC above its established background chemical concentration will not be necessary.

(iv) The methodology used to determine background chemical concentrations in soil shall be conducted in accordance with EPA's Engineering Forum Issue: Determination of Background Concentrations of Inorganics in Soils and Sediments at Hazardous Waste Sites (EPA/540/S-96/500), December 1995, or another method approved by MDEQ.

(v) The methodology used to determine background chemical concentrations in groundwater shall be conducted in accordance with EPA's Guidance Document on the Statistical Analysis of Ground-Water Monitoring Data at RCRA Facilities (EPA/530/SW-89/026), April 1989, or another method approved by MDEQ.

(3) Regionally Prevalent Chemicals - CoC concentrations may be compared to regionally prevalent chemical concentrations to evaluate appropriate remedial actions at the Site.

(i) To establish regionally prevalent chemical concentrations, the Brownfield Applicant may collect samples from locations throughout a substantial geographic region and outside the influence of known contaminated areas, as approved by MDEQ, and must analyze these samples using the same analytical methods as the CoC analyses.

(ii) If the Applicant can establish that the concentration of a CoC is higher than the concentration of a regionally prevalent chemical, the Applicant shall have the option of using the concentration of the regionally prevalent chemical as the Remedial Goal (RG) provided

(a) the cumulative (total) site carcinogenic risk does not exceed 1 x 10-4 for all on-site carcinogenic CoCs and

(b) the site hazard index (summation of hazard quotients) does not exceed 3 for all on-site non-carcinogenic CoCs that affect the same organ or organ system.

(iii) The methodology used to determine regionally prevalent chemical concentrations in soil shall be conducted in accordance with EPA's Engineering Forum Issue: Determination of Background Concentrations of Inorganics in Soils and Sediments at Hazardous Waste Sites (EPA/540/S-96/500), December 1995, or another method approved by MDEQ.

(iv) The methodology used to determine regionally prevalent chemical concentrations in groundwater shall be conducted in accordance with EPA's Guidance Document on the Statistical Analysis of Ground-Water Monitoring Data at RCRA Facilities (EPA/530/SW-89/026), April 1989, or another method approved by MDEQ.

(4) Site-Specific Variables - If the Applicant can demonstrate to the satisfaction of MDEQ that site-specific variables (i.e., exposure duration, exposure frequency, moisture content, etc.) are more representative of site conditions than the default variables utilized in the development of the Tier 1 TRGs, the Applicant may modify site-specific variables in the risk calculation to develop RGs for the CoCs. Chemical-specific values (i.e., Henry's law constant, diffusivity in water, etc.) must be taken from EPA's Soil Screening Guidance: Technical Background Document (EPA/540/R-95/128), May 1996, unless otherwise approved by MDEQ. The Applicant shall not adjust the following variables in the development of site-specific RGs in Tier 2:

(i) Oral cancer slope factor;

(ii) Inhalation cancer slope factor;

(iii) Oral chronic reference dose;

(iv) Inhalation chronic reference dose;

(v) Target excess individual lifetime cancer risk;

(vi) Target hazard index;

(vii) Body weight, adult; or

(viii) Body weight, child.

(5) Eliminate/Minimize Exposure Routes - If the Applicant can demonstrate to the satisfaction of MDEQ that land-use restrictions and engineering controls at the site will eliminate all complete exposure pathways or will minimize contamination exposure to levels that will be protective of human health and the environment, MDEQ may determine that further remediation is not required. The Commission considers the presence of free product to be an unacceptable potential risk to public health and the environment because it is considered to be a continuing source of contamination that may increase the level of risk that is the basis for the remediation requirements, may reduce the margin of safety provided by the remediation design, or may jeopardize the permanence of the Brownfield Agreement. Therefore, free product must be removed unless it can be demonstrated to the satisfaction of MDEQ that removal of the free product is technically impracticable. The Applicant must also demonstrate to the satisfaction of MDEQ that the contamination is confined and will remain confined within the site boundaries. Any monitoring plan must be approved by MDEQ.

(6) TPH Fractioning - In areas where concentrations of Tier 1 petroleum hydrocarbon indicator compounds are not quantifiable to the Tier 1 TRGs and where the concentrations of TPH exceed the Tier 1 TRG for TPH-GRO/DRO, the Brownfield Applicant may either (1) conduct a more detailed evaluation of petroleum Hydrocarbons using the methodology outlined in Rule 2.2.7 of this Subchapter or (2) conduct an evaluation of TPH utilizing another methodology approved by MDEQ.

(7) Other Approved Methods - MDEQ may approve other risk evaluation methodologies or combinations thereof under Tier 2.

(2) MDEQ may consider utilizing the Method Detection Limit (MDL) as the site-specific Remediation Goal (RG) on a case by case basis.

(3) References for any fate and transport models used for the exposure point calculations (EPA-approved model or models that have been peer reviewed by experts in the modeling field) and all input values and assumptions for the models must be provided to and approved by MDEQ.

Notes

11 Miss. Code. R. 3-2.2.4

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