Low-Threat Closure Policy
On May 1, 2012, the State Water Resources Control Board (State Water Board) adopted a
statewide policy (Policy) on the closure of leaking petroleum underground storage tank (UST)
sites in California. The Policy applies to petroleum UST sites subject to Chapter 6.7 of the
Health and Safety Code and establishes both general and media-specific criteria. If both the
general and applicable media-specific criteria are satisfied, then the leaking UST case is
generally considered to present a low threat to human health, safety and the environment. The
Policy recognizes, however, that even if all of the specified criteria in the Policy are met, there
may be unique attributes of the case or site-specific conditions that increase the risk associated
with the residual petroleum constituents.
In order for the site to be accurately and completely evaluated for the above conditions, we
request that you review each of the general and specific criteria established in the Policy and
provide at a minimum, the information requested in the table below. The information must be
provided within the format of a technical report that is prepared, signed, and stamped by a
California Professional Geologist or Engineer. The thoroughness of the technical report will
facilitate timely review and ultimately case closure.
Required Information to Review Case for Low-Threat Closure Per Resolution 2012-0016 (43kb)*
Criteria for Low-Threat Case Closure
In the absence of unique attributes of a case or site-specific conditions that demonstrably increase the risk associated with residual petroleum constituents, cases that meet the general and media-specific criteria described in this policy pose a low threat to human health, safety or the environment and are appropriate for closure pursuant to Health and Safety Code section 25296.10. Cases that meet the criteria in this policy do not require further corrective action and shall be issued a uniform closure letter consistent with Health and Safety Code section 25296.10. Annually, or at the request of the responsible party or party conducting the corrective action, the regulatory agency shall conduct a review to determine whether the site meets the criteria contained in this policy.
General criteria that must be satisfied by all candidate sites are listed as follows:
a. The unauthorized release is located within the service area of a public water system;
b. The unauthorized release consists only of petroleum;
c. The unauthorized ("primary") release from the UST system has been stopped;
d. Free product has been removed to the maximum extent practicable;
e. A conceptual site model that assesses the nature, extent, and mobility of the release has been developed;
f. Secondary source has been removed to the extent practicable;
g. Soil or groundwater has been tested for methyl tert-butyl ether (MTBE) and results reported in accordance with Health and Safety Code section 25296.15; and
h. Nuisance as defined by Water Code section 13050 does not exist at the site.
Low Threat Policy (578kb)*
This 15-page document contains the full text of the policy.
Further information on the Policy can be found on the State Water Resources Control Board website: http://www.waterboards.ca.gov/ust/lt_cls_plcy.shtml