South Carolina Code of Regulations
Chapter 61 - DEPARTMENT OF HEALTH AND ENVIRONMENTAL CONTROL
Subchapter 61-98 - STATE UNDERGROUND PETROLEUM ENVIRONMENTAL RESPONSE BANK (SUPERB) SITE REHABILITATION AND FUND ACCESS REGULATION
Section 61-98.II - Site Rehabilitation Risk-Based Corrective Action Procedures
Universal Citation: SC Code Regs 61-98.II
Current through Register Vol. 48, No. 9, September 27, 2024
Risk-Based corrective action procedures outlined in this Section shall apply to all petroleum and petroleum product releases from underground storage tanks.
A. General Site Rehabilitation Requirements.
1. UST
owners or operators shall implement site rehabilitation activities based on
this regulation and on performance standards and criteria developed by the
Department. Alternate approaches that accomplish the same goals as the
performance standards will also be approvable. The UST owner or operator shall,
upon Department approval, begin site rehabilitation activity and monitor,
evaluate, and report the results of the activity in accordance with a schedule
and in a format approved by the Department.
2. The current use and reasonably anticipated
future use of sites shall be considered in making risk-based decisions
including, but not limited to, the development of site conceptual exposure
models, establishment of exposure points, and corrective actions. The
reasonably anticipated future use of sites shall be determined based on factors
such as: the current use of the site; zoning laws; comprehensive community
master plans; population growth patterns and projections; accessibility of the
site to existing infrastructure such as transportation and public utilities;
site location in relation to urban, residential, commercial, industrial,
agricultural, and recreational areas; Federal/State land use designation;
historical or recent development patterns; and location of Wellhead Protection
Areas.
3. UST owners or operators
must take actions to prevent further releases, control fire and explosion
hazards, and remove free product pursuant to the UST Control Regulations,
R.61-92, Section280.
B. Site Priority System, Risk Evaluation, and Corrective Action for Releases of Petroleum and Petroleum Products.
1. UST releases, regardless of its
time of occurrence, shall be classified using this priority system.
a. Releases are placed in Classification 1 if
any one of the following conditions exists:
(1) an emergency situation;
(2) a fire or explosion hazard;
(3) vapors or free product in a structure or
utility;
(4) concentrations of
chemicals of concern have been detected in a potable water supply or surface
water supply intake;
(5) free
product exists on surface water;
(6) chemicals of concern exist in surface
water.
b. Releases are
placed in Classification 2a if any one of the following conditions exists:
(1) a significant near term (zero to one
year) threat to human health, safety, or sensitive environmental
receptors;
(2) potable supply wells
or surface water supply intakes are located less than one year ground-water
travel distance downgradient of the source area.
c. Releases are placed in Classification 2b
if any one of the following conditions exists:
(1) free product in a monitoring well
measured at greater than one foot thickness;
(2) potable supply wells or surface water
supply intakes are located less than 1000 feet downgradient of the source area
(where ground-water velocity data is not available).
d. Releases are placed in Classification 3a
if any one of the following conditions exists:
(1) a short term (one to two years) threat to
human health, safety, or sensitive environmental receptors;
(2) potable supply wells or surface water
supply intakes are located greater than one year and less than two years
ground-water travel distance downgradient of the source area;
(3) sensitive habitats or surface water exist
less than one year ground-water travel distance downgradient of the source area
and the ground water discharges to the sensitive habitat or surface
water.
e. Releases are
placed in Classification 3b if any one of the following conditions exists:
(1) free product in a monitoring well
measured at greater than 0.01 foot thickness and less than one foot
thickness;
(2) concentrations of
chemicals of concern above the risk-based screening levels have been detected
in a non-potable water supply well;
(3) concentrations of chemicals of concern in
surface soil (less than three feet below grade) in areas that are not
paved;
(4) sensitive habitats or
surface water used for contact recreation are less than 500 feet downgradient
of the source area (where ground-water velocity and discharge location data are
not available);
(5) the site is
located in a sensitive hydrogeologic setting, determined based on the presence
of fractured or carbonate bedrock hydraulically connected to the impacted
aquifer;
(6) ground water is
encountered less than 15 feet below grade and the site geology is predominantly
sand or gravel.
f.
Releases are placed in Classification 4a if any one of the following conditions
exists:
(1) a long term (greater than two
years) threat to human health, safety, or sensitive environmental
receptors;
(2) potable supply wells
or surface water supply intakes are located greater than two years and less
than five years ground-water travel distance downgradient of the source
area;
(3) non-potable supply wells
are located less than one year ground water travel distance downgradient of the
source area.
g. Releases
are placed in Classification 4b if any one of the following conditions exists:
(1) free product exists as a sheen in any
monitoring wells;
(2) non-potable
supply wells are located less than 1000 feet downgradient of the source area
(where ground-water velocity data is not available);
(3) the ground water is encountered less than
15 feet and the site geology is predominantly silt or clay.
h. Releases are placed in
Classification 5 if any one of the following conditions exists:
(1) there is no demonstrable threat, but
additional data are needed to show that there are no unacceptable risks posed
by the site;
(2) assessment data
for the site indicate concentrations of chemicals of concern are above the
risk-based screening levels or site-specific target levels, as appropriate, and
further assessment is needed;
(3)
assessment data for the site indicate concentrations of chemicals of concern
are below the risk-based screening levels or site-specific target levels, as
appropriate, but the samples are determined to not be representative;
therefore, further assessment is needed.
i. The Department or owner or operator may
re-evaluate the priority of a release upon receipt of additional information.
However, the Department shall make the final decision as to priority
classification.
2. The
following risk-based corrective action procedures shall be used for releases
from USTs upon Department approval. Risk evaluations shall be performed in
accordance with this regulation and applicable Department performance standards
and criteria.
a. The information necessary
for a Tier 1 evaluation includes, but is not limited to, the following:
(1) A review of historical records of site
activities and past releases;
(2)
Quantification of the concentrations of the chemicals of concern;
(3) Parameters necessary to utilize soil
leachability models, if appropriate;
(4) Location of source(s) of chemicals of
concern;
(5) Location of maximum
concentrations of chemicals of concern in soil and ground water:
(6) Determination of regional or
site-specific hydrogeologic conditions such as depth to ground water,
ground-water flow direction, hydraulic gradient, ground-water flow
velocity;
(7) Determination if the
chemicals of concern in the soil will leach to ground water in excess of
risk-based screening levels;
(8)
Location of current and reasonable future receptors;
(9) Identification of potential significant
transport and exposure pathways.
(10) Determination of current and reasonably
anticipated future use of the property, ground water, surface water, and
sensitive habitats where the release has occurred and the surrounding
property.
(11) If an exposure is
identified, concentrations of chemicals of concern measured at point(s) of
exposure.
b. The UST
owner or operator shall use the data collected as described in
(a) to evaluate the risk presented by the
release using the following Tier 1 evaluation method:
(1) Develop a site conceptual exposure model
to identify all exposure pathways.
(a)
Information about the facilities operations, the source of chemicals of
concern, current and expected site conditions and/or land use, proximity to
receptors, current and expected use of ground water, and human receptors is
necessary to develop the model.
(b)
Potential exposure pathways to be considered for evaluation based on the site
conceptual model shall include: air inhalation, ground water ingestion,
surficial soil ingestion, dermal contact, and subsurface soil leaching to
ground water.
(c) A summary of all
complete exposure pathways at a site shall be completed for current conditions
and for reasonably anticipated future use if different from the current
use.
(2) Use the site
conceptual exposure model developed in (1) to identify the data required to
quantify the exposure by estimating the dose for all complete pathways. In Tier
1, risk-based screening levels for dermal contact, soil ingestion, and vapor
inhalation pathways are based on a Carcinogenic Risk Limit of
106 and a Hazard Index of >= 1 for
non-carcinogens unless a different risk level for a specific chemical of
concern has been established by the Department. Risk-based screening levels for
the soil leaching to ground water pathway shall be based on leaching models
approved by the Department. Risk-based screening levels for ground water
ingestion shall be based on maximum contaminant levels or other health based
criteria for chemicals of concern without established maximum contaminant
levels. For complete pathways other than the soil leaching to ground water and
ground-water ingestion, risk-based screening levels shall be calculated based
on the carcinogenic risk limit and the hazard quotient values stated in (2)
above, published toxicity data and published reasonable maximum exposure
values. The exposure factors used in the calculations shall be based on
reasonable maximum exposure.
(3)
Calculate the exposure for all identified complete pathways. The risk-based
screening levels established by the Department for the chemicals of concern
must be met at the exposure point(s). In Tier 1, the exposure point(s) and
point(s) of compliance shall be located within the source area of the release
or the area containing the highest concentrations of the chemicals of
concern.
c.
Representative concentrations of chemicals of concern in affected media are
determined by the following:
(1) For ground
water: the maximum concentrations of chemical of concerns obtained from last
sampling event.
(2) For soil: the
maximum concentrations of chemicals of concern obtained in the last sampling
event for the ingestion, inhalation, and dermal contact pathway; and the
average chemical of concern concentrations in the source area for the soil
leaching to ground water pathway. To determine representative chemical of
concern concentrations in the soil to be used in a leachability model, for each
chemical of concern, the three soil samples with the highest non-zero
concentration of chemicals of concern shall be averaged.
(3) For vapor: the maximum concentrations of
chemicals of concern obtained in last sampling event.
d. If the concentrations of the chemical of
concern at representative sample locations are below the Risk-Based Screening
Levels, further assessment or cleanup may not be necessary, upon Department
approval.
e. If the representative
concentrations of chemical(s) of concern in the affected media are above the
risk-based screening levels, the UST owner or operator shall conduct one or
more of the following: interim remedial action; remedial action using the
risk-based screening levels as target levels, as approved by the Department;
other Department approved actions necessary to reduce risk; or further Tier
evaluation. Further tier evaluation is warranted if: the site-specific target
levels developed under further tier evaluation will be significantly different
than the Tier 1 risk-based screening levels, the cost of remedial action to
risk-based screening levels will likely be greater than further tier evaluation
and subsequent remedial action, or the approach or assumptions, used to derive
the current tier's goals are not appropriate for conditions at the
site.
f. If a Tier 2 assessment is
warranted, the UST owner or operator shall perform a Tier 2 assessment in
accordance with this regulation and applicable Department criteria. Additional
site assessment for a Tier 2 evaluation may include, but is not limited to:
determination of site-specific hydrogeologic conditions; determination of
horizontal and vertical extent of chemicals of concern relative to the
Risk-Based Screening Levels, as appropriate; determination of changes in
concentrations of chemicals of concern over time; determination of
concentrations of chemicals of concern measured at exposure points; and, fate
and transport evaluation to predict the attenuation of the chemicals of concern
away from the source area.
g. The
UST owner or operator shall use the data collected as described in (f) to
evaluate the risk presented by the release using the following Tier 2
evaluation:
(1) Establish the exposure point.
The most likely point of exposure closest to the source area shall be
established as the exposure point for each complete pathway
identified.
(2) For the
ground-water ingestion pathway, the exposure point shall be established based
on the current and reasonably anticipated future use of the ground water.
(a) If the ground water at a site is a
current source of drinking water, or is reasonably anticipated to be utilized,
the exposure point shall be established in the source area of the release or
the area with the highest concentrations of chemicals of concern.
(b) If the ground water at a site is not
currently used as a source of drinking water, or is not reasonably anticipated
to be utilized, the exposure point shall be located hydraulically upgradient of
the nearest receptor or the first ground water hydraulically downgradient of
the site reasonably anticipated to be utilized.
(c) If the site is located within a
designated Wellhead Protection Area, the exposure point(s) shall be established
to prevent concentrations of chemical(s) of concern from exceeding maximum
contaminant levels in the drinking water well.
(3) Establish a site-specific target level
for each chemical of concern identified at the site which exceeds it's
risk-based screening level. A site-specific target level shall be established
for each complete pathway identified that calculates an acceptable source area
concentration so that risk-based screening levels are not exceeded at the
point(s) of exposure.
(a) For the
ground-water exposure pathway, the reduction of chemicals of concern in the
saturated zone shall be estimated using either empirical data or models
approved by the Department and implemented with site-specific data. Empirical
data can be used to estimate the overall concentration reduction factor of the
chemicals of concern in the relevant media from the source to the exposure
point. Models can also be used to estimate the fate and transport of the
chemicals of concern away from the source area.
(b) For the soil leaching to ground water
pathway, the site-specific target level for each chemical of concern in soil
shall be calculated using leachability models approved by the
Department.
(c) Site-specific
target levels for the dermal contact, soil ingestion, and vapor inhalation
pathways shall be based on a Carcinogenic Risk Limit of
106 and a Hazard Index of >= 1 for
non-carcinogens to be applied at the exposure point unless a different risk
level for a specific chemical of concern has been established by the
Department. Department approved less conservative exposure factors may be used
in the calculations for commercial and industrial scenarios. Site-specific
exposure factors or most likely or average exposure factors may be used, as
appropriate.
(4)
Establish the point(s) of compliance. The point(s) of compliance shall be
established hydraulically downgradient of the source area and hydraulically
upgradient of an exposure point. At least one point of compliance must be
located directly downgradient of the source area between the source area and
the exposure point for each complete pathway. A minimum of one year travel time
for the chemicals of concern from the point of compliance to the exposure point
shall be established where possible. Additional point(s) of compliance are
necessary where complex hydrogeologic conditions exist that may control
chemical of concern migration.
h. If the concentrations of the chemicals of
concern are below their site-specific target levels, the UST owner or operator
shall submit a corrective action plan proposing a monitoring program to verify
intrinsic remediation.
i. If
representative concentrations of chemical(s) of concern in the affected media
are above the site-specific target levels, the UST owner or operator shall
conduct one or more of the following: interim remedial action; remedial action
using the site-specific target levels, as approved by the Department; other
Department approved actions necessary to reduce risk; or further Tier
evaluation. Further tier evaluation is warranted if: the site-specific target
levels developed under further tier evaluation will be significantly different
than the Tier 2 site-specific target levels; the cost of remedial action to
site-specific target levels will likely be greater than further tier evaluation
and subsequent remedial action; or the approach or assumptions, used to derive
the current tier's goals are not appropriate for conditions at the
site.
j. If further Tier evaluation
is warranted, the UST owner or operator shall perform a Tier 3 assessment to
collect additional appropriate site-specific data to evaluate the risk
presented by the release for a Tier 3 evaluation.
k. Based on the results of the Tier 3
evaluation, the owner or operator shall perform the appropriate action as
approved by the Department based on the following:
(1) If the concentrations of the chemicals of
concern are below the site-specific target levels, the UST owner or operator
shall develop a corrective action plan proposing a monitoring program to verify
intrinsic remediation.
(2) If the
concentrations of the chemicals of concern are above the site-specific target
levels, the UST owner or operator shall develop a corrective action plan which
shall include active cleanup which may include intrinsic remediation as a
component.
3.
Corrective Action.
a. The UST owner or
operator shall develop and implement a Department approved corrective action
plan for each release to achieve risk-based screening levels or site-specific
target levels established under the risk-based corrective action procedures.
The corrective action plan shall include a schedule for implementation and for
achieving risk-based screening levels or site-specific target levels. The
corrective action plan must be developed and implemented in accordance with
R.61-92 including procedures for Department approval and public notice. Any
selected corrective action alternative funded by the SUPERB Account shall be a
reasonable, cost-effective response for soil and/or ground-water contamination.
In evaluating the cost effectiveness of proposed action, the UST owner or
operator shall take into account the total short and long-term costs of such
action, including the costs of operation and maintenance for the entire period
during which such activities will be required.
b. The UST owner or operator and the
Department shall encourage the use of innovative treatment technologies, where
appropriate.
c. The Department
shall require monitoring, evaluation, and reporting of corrective actions to
evaluate whether the corrective action is efficient and cost
effective.
d. UST owners or
operators shall implement modifications to the corrective action, as required
by the Department, to increase efficiency and cost effectiveness.
e. Once the Department agrees that monitoring
data supports the conclusion that: the risk-based screening levels or
site-specific target levels have been met; the chemicals of concern have
reached equilibrium or are not moving at a significant rate; concentrations of
chemicals of concern are not increasing, no unacceptable risk to human health,
safety, or the environment exists, and that concentrations of chemicals of
concern will not exceed risk-based screening levels at the exposure point or
receptor, the Department may issue a decision that further site rehabilitation
is not necessary. These shall be conditional no further action decisions based
on site-specific conditions and the current or reasonably anticipated future
use of the site. The assumptions and conditions shall be outlined in writing.
The Department shall maintain a registry of releases having conditional no
further action decisions.
f. The
Department approval of a corrective action plan or issuance of a conditional
decision that further site rehabilitation is not necessary shall be considered
an order of the Department enforceable pursuant to the 1976 Code Section
44-2-140.
The UST owner or operator shall not undertake any actions that result in an
increase in risk of exposure to the chemicals of concern including modification
of the current or reasonably anticipated future use of the site without
Department approval. The SUPERB Account shall not be responsible for funding
further site rehabilitation as a result of an increase in risk under these
conditions unless a variance to this provision is granted by the
Department.
g. The Underground
Storage Tank Program shall coordinate, on behalf of the owner or operator, all
Department permits associated with implementation of a corrective action
plan.
4. Variances. The
Department may issue a variance to this Section, when, in its opinion, the UST
owner or operator has demonstrated that an equivalent degree of protection will
be provided to human health and the environment. Any variance granted or denied
by the Department shall be in writing and shall contain a brief statement of
the reasons for the approval or denial.
Disclaimer: These regulations may not be the most recent version. South Carolina may have more current or accurate information. We make no warranties or guarantees about the accuracy, completeness, or adequacy of the information contained on this site or the information linked to on the state site. Please check official sources.
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