Upon completion of all applicable requirements of OAR
340-122-0205 through
340-122-0240, a responsible
person may propose closure of a facility as a low-impact site if information
gathered during site investigations clearly demonstrates that site conditions
have stabilized (i.e., significant future migration of contamination is
unlikely) and that the site is likely to have low current and potential future
impact on the basis of risk or impairment of beneficial land and water uses.
The purpose of the low-impact site designation is to provide a streamlined
process for operating gas stations or other industrial or commercial properties
that allows these facilities to remain in operation while the responsible
person manages any potential risk from contamination remaining at the site. If
the Department develops a generic remedy for low-impact sites in accordance
with OAR 340-122-0252, then the
low-impact site requirements specified in this rule (OAR
340-122-0243) will no longer be
in effect. Until such time as a low-impact site generic remedy is in effect,
the steps for low-impact closure are described below.
(1) The site must meet each of the following
conditions:
(a) The source of the release has
been repaired or removed, and all tanks, lines, and associated equipment at the
site have been upgraded to meet applicable technical and regulatory
standards.
(b) The facility must
continue to be used as a gas station or other industrial or commercial use
precluding potential routine exposure to children.
(c) Other than minimal amounts of petroleum
product in the tank pit at the time of tank removal, no measurable free product
was found on the groundwater.
(d)
Concentrations of gasoline in the contaminated soil should not exceed 1000 ppm
TPH, and concentrations of diesel and other non-gasoline fraction hydrocarbon
in the contaminated soil should not exceed 10,000 ppm TPH.
(e) Contaminated soil remaining at the site
should not be located within 3 feet of the land surface, unless:
(A) Contaminant concentrations do not exceed
generic risk-based concentrations for direct contact developed in accordance
with OAR
340-122-0252; or
(B) Department-approved institutional or
engineering controls have been implemented and will be maintained to prevent
direct contact with soils.
(f) Contamination is not located in utility
corridors, unless:
(A) The contamination is
shown to have been stabilized and is unlikely to result in vapor or groundwater
problems;
(B) Contaminant
concentrations do not exceed generic risk-based concentrations for a trench
worker scenario developed in accordance with OAR
340-122-0252; and
(C) The corresponding utility has been
notified of the contamination.
(g) Service station and other nonresidential
buildings must not be located over or within 10 lateral feet and residences
must not be located over or within 50 lateral feet of contaminated soil,
unless:
(A) Contaminant concentrations do not
exceed generic risk-based concentrations for volatilization from soils into
buildings developed in accordance with OAR
340-122-0252; or
(B) It is demonstrated that potential
exposure from volatilization into buildings from this contamination does not
exceed acceptable risk levels; or
(C) Department-approved actions have been
taken to mitigate potential vapor problems.
(h) If groundwater contamination is found at
the site:
(A) There are no water supply wells
located within one-quarter mile of the source of contamination;
(B) The groundwater plume is less than 250
feet in length as measured from the center of the source;
(C) Monitoring data are available to
demonstrate that the groundwater plume has stabilized, or is diminishing in
size;
(D) The groundwater plume
does not leave the source property at concentrations exceeding generic
risk-based concentrations developed in accordance with OAR
340-122-0252, unless owners of
other affected properties consent to institutional or engineering controls
necessary to prevent exposure due to the contaminated groundwater;
and
(E) Service station and other
nonresidential buildings must not be located over or within 10 lateral feet and
residences must not be located over or within 50 lateral feet of contaminated
groundwater, unless:
(i) Contaminant
concentrations within the plume do not exceed generic risk-based concentrations
for volatilization from groundwater into buildings developed in accordance with
OAR
340-122-0252; or
(ii) It is demonstrated that potential
exposure from volatilization into buildings from this contamination does not
exceed acceptable risk levels; or
(iii) Department-approved actions have been
taken to mitigate potential vapor problems.
(2) The responsible person must
implement institutional or engineering controls, in a form acceptable to the
Department, necessary to ensure that a site's designation as a low-impact site
remains unchanged.
(3) The
responsible person must submit a low-impact-site-closure report to the
Department that includes the following:
(a) A
site summary with appropriate scaled maps, a discussion of current and
reasonably likely future land uses for the site and adjacent properties,
including information from local government comprehensive planning plans and
zoning ordinances, and information on geology, hydrogeology, topography, and
other relevant factors on which the low-impact closure is based.
(b) Information about the release, including
a history of all actions taken, data from all samples collected at the site,
and a description of all contamination, including scaled maps showing the
locations of contamination that was treated or removed from the site and
contamination remaining at the site at the time of the report.
(c) Sufficient discussion and supporting data
to address each of the specific low-impact site requirements listed in section
(1) of this rule.
(d) If
groundwater contamination is present at concentrations exceeding generic
risk-based concentrations, a discussion of current and reasonably likely future
water uses.
(e) If groundwater
contamination is present at concentrations exceeding generic risk-based
concentrations and the site is located within a certified drinking water
protection area (DWPA), a description of the DWPA and what additional
information has been gathered and measures taken to ensure that there are no
current or potential future adverse impacts to the groundwater in the aquifer
within the DWPA.
(f) A proposal,
subject to Department approval, for any institutional or engineering controls
necessary to maintain low-impact site conditions.
(4) Upon review of the low-impact site
closure report, the Department may:
(a)
Approve the report and, upon receipt of adequate documentation showing that any
necessary institutional or engineering controls have been implemented and will
be maintained, issue a low-impact site closure letter stipulating the site
conditions that must be maintained;
(b) Request that additional information be
submitted or work be performed in support of the proposed low-impact closure;
or
(c) Determine that the site does
not meet the conditions for low-impact closure and require that additional
actions be taken under other relevant sections of OAR
340-122-0205 through
340-122-0360.
(5) The Department shall require
public notice consistent with applicable requirements of OAR
340-122-0260 for sites proposed
for low-impact closure.
(6) The
owner of any property requiring controls under this rule must notify the
Department of any future changes that might affect the facility's designation
as a low-impact site.
