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 11-3-2.2.6 - Risk-Based Remediation

Current through June 25, 2024
A. Risk-Based
				  Remediation Goals
(1) Risk-based remediation
				  goals (RGs) may be quantitative for chemical-specific RGs or qualitative for
				  remedial action-specific RGs. The methodology for quantifying the
				  chemical-specific RGs involves solving for the concentration term given a
				  defined risk level in a deterministic or probabilistic risk assessment and
				  shall be proposed for the principal threat chemicals or all CoCs if the
				  principal threat chemicals cannot be identified. The chemical-specific RG may
				  be modified upward or downward based on risk management considerations by MDEQ.
				  A qualitative RG is established by describing the objectives for engineering
				  controls that reduce site risk to an acceptable level. Risk-based remediation
				  goals shall accompany the proposed remedial action(s) in the Site
				  Characterization Report and/or the Corrective Action Plan (CAP).
(2) Quantitative RG - Site-specific
				  information that is relevant to the future use of the Site shall be used in the
				  risk methodology.
(a) The derived value shall
				  not be higher than the soil saturation limit (Csat) for the soil or sediment RG
				  for a CoC with a melting point less than 30 degrees Celsius. The derived value
				  shall not be higher than the solubility limit (Csol) for the groundwater RG for
				  groundwater. At sites where a mixture of contaminants is present (e.g.,
				  gasoline), the effective solubility limit may be used if required by MDEQ.
				  Values for Csat and Csol may be found or derived from equations in EPA's Soil
				  Screening Guidance: Technical Background Document (EPA/540/R-95/128), May 1996
				  or other reference approved by MDEQ.
(b) The derived chemical-specific RG for a
				  carcinogen for the protection of human health shall be:
(1) the MCL value,
(2) a value derived using the acceptable
				  carcinogenic risk level of 1x10-6, or
(3) a value defined in state/federal programs
				  and approved by MDEQ.
(c)
				  The derived chemical-specific RG for a non-carcinogen for the protection of
				  human health shall be:
(1) the MCL
				  value,
(2) a value derived using
				  the acceptable hazard quotient level of unity (1), or a value defined in
				  state/federal programs and approved by MDEQ.
(d) 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 (2) 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. In no event, except with regard to a background chemical
				  concentration, may either (1) the cumulative (total) site carcinogenic risk
				  exceed 1x10-4 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.
(e) Any of the following methods may be used
				  to derive chemical-specific quantitative RGs in soil or sediment to protect
				  human health:
(1) algorithms or methodology
				  employed by MDEQ in deriving the TRGs in appendix A of this Subpart
				  II;
(2) algorithms or methodology
				  employed by EPA Region III (Technical and Program Support Branch, 3HW70) to
				  derive the Risk-Based Concentrations (RBCs);
(3) algorithms or methodology employed by EPA
				  (Office of Solid Waste and Emergency Response) to derive the SSLs using EPA's
				  Soil Screening Guidance: Technical Background Document (EPA/540/R-95/128), May
				  1996;
(4) algorithms or methodology
				  employed by the American Society of Testing and Materials (ASTM) to derive the
				  Risk-Based Screening Levels (RBSLs) (Emergency Standard Guide ES 38-94);
				  or
(5) other EPA published or
				  peer-reviewed methodologies that have been reviewed and approved by MDEQ.
Note: All input/default values must be approved by MDEQ
					 prior to employing any of the above methodologies.
(f) Fate and transport modeling and/or the
				  use of a dilution-attenuation factor (DAF) to determine
				  migration-to-groundwater soil RGs approved by MDEQ may be used to demonstrate
				  that the concentrations of CoCs at the source area provide adequate protection
				  of human health and the environment at the Site boundary, except when it
				  appears that free product is present.
(g) The acceptable level of a CoC in
				  groundwater at the Site boundary is its groundwater RG or if the boundary is a
				  surface water body, the water quality criteria published by MDEQ, whichever is
				  lower.
(h) Any of the following
				  methods may be used to derive chemical-specific quantitative RGs in
				  groundwater:
(1) algorithms or methodology
				  employed by MDEQ in deriving the TRGs in Appendix A of this Subchapter
				  II;
(2) algorithms or methodology
				  employed by EPA Region IX (Technical Support Team, DFD-8-B) to derive the
				  Preliminary Remediation Goals (PRGs); or
(3) other EPA published or peer-reviewed
				  methodologies that have been reviewed and approved by MDEQ.
(i) The quotient method may be
				  used to derive quantitative RGs for the protection of an ecological receptor of
				  concern.
(j) The following methods
				  may be used to derive chemical-specific quantitative RGs in soil and sediment
				  for protection of an ecological receptor of concern:
(1) algorithms or methodology described in
				  the Risk Assessment Handbook, Volume 2 - Environmental Evaluation (EM 200-1-4)
				  developed by the U.S. Army Corps of Engineers; or
(2) other EPA published or peer-reviewed
				  methodologies that have been reviewed and approved by MDEQ.
(3) Qualitative RG - A qualitative RG shall
				  define objectives and describe how land-use restrictions and/or engineering
				  controls are expected to reduce site risk to an acceptable level. The following
				  information shall be presented:
(a) complete
				  exposure pathway that contribute to human health or environmental
				  risk;
(b) the CoC or principal
				  threat chemical and its background concentrations;
(c) physical, chemical, and fate and
				  transport properties of the CoC or principal threat chemical (including the
				  potential for adsorption and monitored natural attenuation);
(d) presence of any man-made or natural
				  conveyances, conduits, or transport routes from the source to the receptor
				  location;
(e) Potential engineering
				  controls that will exclude the exposure pathway based on treatability study
				  data and/or practical experience may also be considered. Engineering controls
				  may include physical or hydraulic control measures, but shall not include the
				  exclusive use of security fencing. Typical engineering controls are presented
				  below and the Applicant may propose alternative controls for MDEQ approval.
(1) groundwater recovery trenches and
				  leachate collection systems;
(2)
				  groundwater extraction (pumpage) and treatment systems;
(3) engineered caps with or without liner
				  systems;
(4) slurry walls,
				  funnel-and-gate barrier walls, bio-polymer walls, or any modifications thereof;
				  and
(5) permanent structures such
				  as building, driveways, and paved roads.
(4) No further action at the Site shall be
				  based on obtaining either the quantitative or qualitative RGs, or both, and/or
				  other terms and conditions stipulated by MDEQ (i.e., Brownfield Agreement,
				  Corrective Action Plan). The Applicant has the option to propose either type of
				  RGs or a combination of the two for delineated areas of the Site, depending on
				  the site-specific factors, chemical data, and risk management considerations
				  approved by the MDEQ. The following criteria shall be met for this
				  determination:
(a) The remedial action has
				  achieved the chemical-specific RGs based on verification sampling and analyses
				  at the point of exposure or at the contaminated source area. The 95% UCL of the
				  normalized verification sample data must be less that the chemical-specific
				  RG.
(b) The engineered control
				  measures proposed by the Applicant and approved by MDEQ completed.
(c) The groundwater quality at the Site
				  boundary shall not exceed MCLs or risk-based TRGs for groundwater identified in
				  Appendix A. The Point of Compliance is the Site Boundary.
(d) Free product must be removed from the
				  Site, unless it can be demonstrated to the satisfaction of MDEQ that removal of
				  the free product is technically impracticable and that the contamination is
				  confined and will remain confined within the Site boundaries. Free product is
				  considered to exist if:
(1) concentrations in
				  soil exceed Csat for CoCs with a melting point of less than 30 degrees
				  Celsius;
(2) concentrations in
				  groundwater exceed Csol for any CoC or the effective Csol or
(3) measurable using best available
				  technologies.