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; andg. 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.
Cal. Code Regs. Tit. 23, § 2923
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). 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).