| (A) The owner and operator shall consider potential exposure
to receptors through direct and indirect exposure pathways as required by
the agency and determine whether or not such pathways are complete or not.
A pathway determined to be incomplete in the Plan A evaluation does not need
to be reevaluated under this subsection.
(B) For complete pathways, target concentrations shall be calculated
using equations, target risk goals, and exposure factors as established by
the agency.
(C) Target concentrations shall be based upon chemical property
information defined by the agency when such information is provided by the
agency.
(D) Target concentrations for indirect or cross-media pathways
shall be based upon default media property assumptions and models defined
by the agency when site-specific media property information is not available.
Use of site-specific media property information is encouraged as part of this
evaluation. If the owner and operator wish to use alternative models, prior
concurrence from the agency shall be obtained.
(E) The agency may require owners and operators to collect
additional site information prior to or after the evaluation of the site under
this section to substantiate the conclusions of the evaluation.
(F) For known or suspected carcinogens, the individual and
cumulative carcinogenic risk of 1 X 10-6 to 1
X 10-4 as required by the agency.
(G) Target concentrations are to be established at concentrations
which do not exceed a hazard index of unity (one) for non-carcinogens.
(H) The owner and operator may apply target concentrations
for direct exposure pathways calculated under paragraph (1) of this section
at reasonable exposure points instead of the source area unless the source
area is a reasonable exposure point. All exposure points assumptions are subject
to approval by the agency.
(I) The agency may allow use of compliance points to serve
as the basis for meeting target concentrations for indirect exposure pathways
provided:
(i) the proposed compliance point locations are consistent
with the results of the exposure assessment;
(ii) the proposed compliance point locations are upgradient
of actual receptors;
(iii) the proposed compliance point locations will not allow
unaffected receptors to become affected;
(iv) the proposed compliance point locations are accessible
for monitoring/sampling;
(v) karst, fracture controlled, or otherwise highly complex
hydrogeologic system is not involved;
(vi) estimates or predictions of compliance point concentrations
and degree and rate of transport of regulated substances are verified with
site monitoring data. Where site monitoring data and contaminant fate and
transport modelling results yield conflicting information, the agency shall
place more value on the monitoring data;
(vii) the agency may require the use of specific contaminant
fate and transport models; and
(viii) target concentrations shall be met at all points beyond
(downgradient of) the compliance point(s).
(J) When the criteria for the use of compliance points as required
in subparagraph (I) of this paragraph cannot be met, then the target concentrations
for indirect exposure pathways shall be met throughout the plume.
(K) Target concentrations for soil, air, and water shall also
take into account other factors such as vegetation effects, sensitive environmental
receptors, and aesthetic considerations (e.g., stained surface soils) as appropriate
in the final analysis.
(L) The owner and operator, or the agency, may recommend the
use of specific institutional controls to control or eliminate potentially
viable exposure pathways, and to reinforce exposure assumptions and future
land use assumptions.
(M) The owner and operator shall submit reports in accordance
with a schedule and in a format established by the agency.
(N) The owner and operator shall meet all requirements imposed
by the agency.
(3) Health-based target concentration established pursuant
to paragraphs (1) or (2) of this section shall be based upon toxicological
information current at the time the report is submitted to the agency. Toxicological
information shall be from the following sources in order of listing:
(A) United States Environmental Protection Agency Integrated
Risk Information System (IRIS);
(B) Health Effects Assessment Summary Table (HEAST);
(C) United States Environmental Protection Agency Criteria
Documents;
(D) Agency for Toxic Substances and Disease Registry (ATSDR)
Toxicological Profiles; and
(E) other scientifically valid published sources that are widely
accepted.
(4) Target concentrations shall be based on the particular
land use (residential or commercial/industrial) as defined in §334.202
of this title (relating to Definitions) of each affected property.
(5) The exposure assessment and determination of target concentrations
conducted pursuant to paragraphs (1) or (2) of this section shall consider:
(A) the physical and chemical characteristics of the regulated
substance, including its toxicity, persistence, and potential for migration;
(B) the hydrogeologic characteristics of the facility and the
surrounding area;
(C) the proximity, quality, and current and future uses of
nearby surface water and groundwater;
(D) the potential effects of residual contamination on nearby
surface water and groundwater;
(E) an exposure assessment considering exposure pathways as
requested by the agency;
(F) any information assembled in compliance with this subchapter;
and
(G) any additional considerations as established by the agency.
(6) After receipt of a written statement by the agency that
all corrective action regulations have been met and that no further corrective
actions are warranted, then the case shall be considered closed unless a substantial
change in circumstances results in an unacceptable risk to human health or
the environment. A substantial change in circumstance shall include, but is
not limited to:
(A) a failure to maintain the obligations of an institutional
control as set out in §334.206 of this title (relating to Criteria for
Institutional Control Use);
(B) a change in land use from a less sensitive land use to
a more sensitive land use, such as commercial/ industrial to residential;
(C) an actual exposure condition is determined to be occurring
at levels not protective of human health and safety, or the environment. For
purposes of this subchapter, changes in toxicity values or general procedures
utilized to determine target concentrations shall not be considered a substantial
change in circumstances, unless these changes are of such magnitude to present
an unacceptable threat to human health and safety, or the environment when
evaluated for future exposure conditions based on site- specific considerations;
or
(D) new information indicates that the regulated substances
at the facility or affected area were not sufficiently characterized such
that an unacceptable threat to human health and safety, or the environment
continues to exist.
|
