Mississippi Administrative Code › Title 11 - Mississippi Department of Environmental Quality › Part 3 - Hazardous Waste Management Regulations › Chapter 2 - Mississippi Commission on Environmental Quality Final Regulations Governing Brownfield Voluntary Cleanup and Redevelopment in Mississippi › Subchapter 2 - RISK EVALUATION PROCEDURES › Rule 11-3-2.2.4 - Tier 2 Evaluation

Current through June 25, 2024
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.