Single-Walled Underground Storage Tanks Closure Initiative
The California Health and Safety Code (H&SC) 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 must permanently close USTs that are noncompliant with the H&SC. Specifically, UST 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. 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 thematic visualizations below map the densities, by county, of single-walled USTs that must be permanently closed on or before December 31, 2025. The figure on top, representing the 2022 census, shows the distribution of the 733 facilities containing 1,927 single-walled USTs statewide. The bottom figure, representing the 2024 census, shows that the number of facilities has increased to 770, but that the number of single-walled USTs has decreased to 1,886. The increase in the number of facilities is partially attributable to the inclusion of abandoned facilities in the count. The number of single-walled USTs remaining in the ground on December 31, 2025, is consistently projected to be about 1,600. The law requires that number to be zero.
To navigate both visualizations, hover your cursor to display the selected county name and number of single-wall USTs. The 2024 distributions are further defined in the bar graphs accompanying the visualization. The center bar graph shows that the sites include 34 abandoned and 736 active USTs The USTs represented in horizontal bar graph are grouped by Program Agency (PA). The data in each graph can be filtered by County by clicking the county of interest on the visualization.
The goal of the Office of Enforcement’s Single-Walled Underground Storage Tank Initiative is to supplement the local Certified Unified Program Agency’s efforts to close all single-walled UST by the December 31, 2025, deadline Our Single-Walled Underground Storage Tank Initiative currently consists of conducting compliance inspections, and enforcement where applicable, at three different sub-sets of single-walled USTs facilities including: federal, emergency-generator, and abandoned . After the deadline, enforcement will proceed in accordance with the State Water Board’s December 19, 2023 Preparation for Enforcement of Single-Walled Underground Storage Tanks Closure Deadline” memo.
