California Code of Regulations › Title 23 - Waters › Division 3 - State Water Resources Control Board and Regional Water Quality Control Boards › Chapter 22 - State Policy for Water Quality Control › Section 2923 - Low-Threat Underground Storage Tank Case Closure Policy

Current through Register 2024 Notice Reg. No. 28, July 12, 2024
On May 1, 2012, the State Water Resources Control Board
				  (State Water Board) adopted the Low-Threat Underground Storage Tank Case
				  Closure Policy (Policy), which is a statewide policy on the closure of leaking
				  petroleum underground storage tank (UST) sites in California. See State Water
				  Board Resolution No. 2012-0016. The Policy applies to petroleum UST sites
				  subject to Chapter 6.7 of the Health and Safety Code. The Policy 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 these cases, the regulatory agency overseeing corrective
				  action at the site must identify the conditions that make case closure under
				  the Policy inappropriate.
Under existing policy, regulatory agencies consider
				  site-specific conditions when determining if the level of corrective action
				  ensures the protection of human health, safety and the environment pursuant to
				  Health and Safety Code section
				  25296.10,
				  subdivision (g). With the knowledge and experience gained over the last 25
				  years of investigating and remediating petroleum UST releases, site conditions
				  and characteristics have been identified that, if met, will generally ensure
				  the protection of human health, safety and the environment. This Policy
				  identifies those standardized criteria. The Policy is necessary to establish
				  consistent, statewide case closure criteria for low-threat petroleum UST sites
				  in California.
General Criteria
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; and
g. Soil or
				groundwater has been tested for MTBE and results reported in accordance with
				Health and Safety Code section
				25296.15.
If all the general criteria are satisfied, the site must meet
				  applicable, media-specific criteria in order to be closed under the policy. The
				  exposure scenarios related to petroleum releases have been combined into three
				  media-specific criteria: Groundwater, vapor intrusion to indoor air, and direct
				  contact and outdoor air exposure.
Media Specific Criteria:
a. Groundwater: To satisfy the groundwater
				criteria, the contaminant plume that exceeds water quality objectives must be
				stable or decreasing in areal extent, which means a plume where a contaminant
				mass has expanded to its maximum extent: the distance from the release where
				attenuation exceeds migration. In addition, the site must meet all of the
				specified criteria of at least one of the five classes of sites listed on page
				6 of the Policy. The Policy also addresses sites where petroleum-contaminated
				soil threatens to impact groundwater. Sites with soil that does not contain
				sufficient mobile constituents to cause groundwater to exceed the groundwater
				criteria in the Policy shall also be considered low threat for the groundwater
				medium.
b. Vapor Intrusion to
				Indoor Air: The vapor-intrusion criterion applies to petroleum release sites
				when existing buildings are occupied or are reasonably expected to be occupied
				or where buildings for human occupancy are reasonably expected to be
				constructed in the near future. If one of the three specified tests under
				Section 2"Petroleum Vapor Intrusion to
				Indoor Air" is satisfied, then the site satisfies the media-specific criteria.
				Appendices 1 through 4 illustrate four potential exposure scenarios and
				describe characteristics associated with each scenario. For sites using test
				2a, conditions at the release site conditions must satisfy all of the
				characteristics and criteria of scenarios/Appendices 1 through 3, or all of the
				characteristics of scenario/Appendix 4.
The Policy contains an exception to the media-specific
				  criteria for vapor intrusion to indoor air for active commercial petroleum
				  fueling facilities.
c.
				Direct Contact and Outdoor Air Exposure: The Policy describes conditions where
				direct contact with petroleum-contaminated soil or inhalation of petroleum
				volatized to outdoor air poses an insignificant threat to human health. If one
				of the three tests identified under Section
				3 is satisfied, the media-specific
				criterion for direct contact is satisfied. For test 3a, the requirements in
				Table 1 must be satisfied.
The Policy requires regulatory agencies, annually or at the
				  request of a responsible party, to conduct a review to determine if site meets
				  the criteria in the Policy. The Policy also contains notification requirements,
				  as well as requirements to destroy monitoring wells and remove waste debris,
				  before the regulatory agency issues the uniform closure letter described in
				  section
				  25296.10
				  of the Health and Safety Code.
1. New section
				  filed 7-30-2012 summarizing State Water Resources Control Board Resolution No.
				  2012-0016, adopted 5-1-2012; approved by OAL on 7-30-2012 pursuant to
				  Government Code section
				  11353;
				  operative 7-30-2012 (Register 2012, No. 31).