Single-Walled Underground Storage Tanks Closure Initiative

California Health and Safety Code (H&SC) section 25292.05 mandates that on or before December 31, 2025, underground storage tank (UST) owners or operators shall permanently close USTs that are not compliant with the H&SC. Specifically, USTs that do not have secondary containment and a continuous leak detection system do not meet the applicable code requirements. These USTs are generally categorized as single-walled. In short, the H&SC requires the permanent closure of single-walled USTs by December 31, 2025. Penalties for owners or operators who are out of compliance with this requirement range from a minimum of $500 up to $5,000 per day per UST.

The goal of the Office of Enforcement’s Single-Walled Underground Storage Tanks Closure Initiative is to supplement the local Certified Unified Program Agencies’ and Participating Agencies’ efforts to close all single-walled USTs by the December 31, 2025 deadline. The initiative currently consists of conducting compliance inspections, and enforcement where applicable, at three different subsets of single-walled UST facilities: federal, emergency generator, and abandoned. For more information, please visit Permanent Closure Requirements for Underground Storage Tank with Single-Walled Components. After the December 31, 2025 deadline, enforcement will proceed in accordance with the State Water Board’s memos located under the section, “Available Guidance for the Closure of Single-Walled UST Systems.”