11 Miss. Code. R. 3-2.2.3 - Tier 1 Evaluation
A. Tier 1
Evaluation Target Risk Level
The TRGs presented in the Tier 1 TRG table, Appendix A, are based on either:
(1) a 1x10-6 target
risk level for each carcinogenic chemical,
(2) a hazard index not to exceed 1 for each
systemic toxicant, or
(3)
constituent TRG concentrations established through federal/state programs
(i.e., Safe Drinking Water Act). The values presented in the Tier 1 TRG table
will be modified periodically based on EPA updates of toxicity values obtained
from the sources presented in Rule
2.2.5(B)(3)(b) of
this Subchapter 2.
B.
Tier 1 Evaluation Procedures
(1) The basic
methodology for a Tier 1 Evaluation shall be the comparison of the highest
concentration of each contaminant in each media to the TRGs provided in the
Tier 1 TRG table. Results of the comparison will be used to determine if the
site specific data are:
(a) at or below the
unrestricted risk value;
(b) above
the unrestricted risk value, but at or below the restricted risk value;
or
(c) above the restricted risk
value.
(2) Sites that do
not require an ecological evaluation beyond the Site Ecological Checklist and
that exhibit chemical concentrations that are at or below the unrestricted TRGs
do not require further evaluation or action. Such sites are not eligible for
the Brownfields Program since remediation is not necessary as required in
Section 49-5-5(b) of
Mississippi Code Annotated, as amended.
(3) Sites with chemical concentrations in
soils that are greater than the unrestricted TRGs but below the restricted TRGs
may:
(a) clean-up and/or remove the affected
media to a value at or below the unrestricted TRG values resulting in an
unrestricted land-use site;
(b)
implement appropriate institutional controls (i.e., land use restriction and
agreed order with MDEQ) resulting in a restricted land use site; or
(c) perform a Tier 2 Evaluation.
(4) Sites with chemical
concentrations in soils that exceed the restricted TRGs may:
(a) clean-up and/or remove the affected media
to a value at or below the unrestricted TRG values resulting in an unrestricted
land use site;
(b) clean-up and/or
remove the affected media to a value at or below the restricted TRG values but
above the unrestricted TRG values resulting in a restricted land use site and
implement appropriate institutional controls (i.e., land use restriction and
agreed order with MDEQ); or
(c)
perform a Tier 2 Evaluation.
(5) Sites with chemical concentrations in
groundwater that are greater than the unrestricted TRGs may:
(a) clean-up the affected media to a value at
or below the unrestricted TRG values resulting in an unrestricted land-use
site;
(b) implement appropriate
institutional controls (i.e., land use restriction and agreed order with MDEQ)
resulting in a restricted land use site; or
(c) perform a Tier 2 Evaluation.
(6) MDEQ may consider utilizing
the Method Detection Limit (MDL) in place of the Target Remediation Goal (TRG)
on a case by case basis.
(7) In
areas of a site where chemical concentrations of petroleum hydrocarbon
indicator compounds (e.g., BTEX, PAHs, MTBE) are not quantifiable to the Tier 1
TRGs (e.g., dilution and/or matrix interference) may:
(a) use the Tier 1 TRGs for TPH-GRO/DRO for
performing a Tier 1 Evaluation; or
(b) perform a Tier 2 TPH Fractioning
Evaluation.
Notes
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