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The AAPG/Datapages Combined Publications Database
Houston Geological Society Bulletin
Abstract
Abstract: Risk-Based Corrective Action for Leaking Storage Tank Sites
By
Petroleum Storage Tank Division, Texas Natural Resource Conservation Commission
For many years, assessment of environmental
contamination in leaking petroleum
storage tank (LPST) cases, as well as the
direction of corrective action at LPST sites
in Texas, was conducted using generic soil
contaminant Action Levels and predetermined
soil and groundwater contaminant
clean-up concentrations. These generic
contaminant concentrations were based on
the Maximum Contaminant Level (MCL)
promulgated by the U.S. Environmental
Protection Agency (USEPA) for each contaminant
of concern in groundwater, and
soil contaminant concentrations considered
to be protective of groundwater resources
(i.e., DRASTIC Index). Although widely
considered to be adequately protective of
human health and safety and the environment,
these predetermined contaminant
cleanup concentrations allowed only a limited
amount of flexibility in the use of site-specific
information. Consequently, until
1994, cleanup levels for all LPST sites in
Texas were derived using a narrow set of
criteria which often yielded cleanup levels
that fell within a predetermined range of
media
-specific contaminant concentrations.
Through the advent of Risk-Based Corrective
Action for Leaking Storage Tank Sites
(TNRCC Guidance Document RG-36),
media
-specific cleanup concentrations are
now determined using a much greater degree
of site-specific information. The result
has been a better allocation and distribution
of available resources and an increased
focus on those sites that pose the
highest potential threat to human health and
safety and the environment. Together with
release prevention requirements adopted
within the last five years (i.e., cathodic protection,
leak detection, fill and overspill
prevention, inventory control, and containment
measures), Risk-Based Corrective
Action has aided greatly in the resolution
of problems related to subsurface releases
of hazardous substances from underground
storage tanks.
Risk-Based Corrective Action is based on
the principle of acceptable Target Risk (for
carcinogenic chemicals) and Hazards Index
(for non-carcinogenic chemicals) for the
receptor populations identified. These values
are determined based on the current and
potential future land use of the subject site.
The Risk-Based Corrective Action procedure
incorporates the use of mathematical
simulation of contaminant fate and transport
processes, toxicology, and data about
receptors, affected media
, and the contaminants
of concern at the subject site. The
procedure is outlined and explained within
a regulatory context and the benefits and
shortfalls are addressed.
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