Permanent Closure Requirements for Single-Walled USTs
Background
Effective September 25, 2014, Senate Bill (SB) 445 (Stats. 2014, Ch. 547) changed the underground storage tank (UST) regulatory program regarding design and construction of USTs in Health and Safety Code, chapter 6.7 (H&SC), section 25292.05. Specifically, this change required that on or before December 31, 2025, the owner or operator must permanently close a UST if it was designed and constructed before January 1, 1984 and does not meet the requirements of H&SC, section 25291(a)(1)-(6), or if it was designed and constructed before January 1, 1997 in accordance with H&SC, section 25291(a)(7).
All regulated USTs that did not meet the requirements of H&SC, section 25291(a)(1)-(6) were required to be permanently closed by December 31, 2025 in accordance with H&SC, section 25298, and the California Code of Regulations, title 23, division 3, chapter 16 (UST Regulations), section 2681. A single-walled UST is either the tank and/or the connected piping that does not have secondary containment and a continuous release detection system meeting the requirements of H&SC, section 25291(a)(1)-(6).
Single-walled UST systems that did not permanently close by December 31, 2025 are out of compliance, cannot be operated, and are subject to enforcement action — including red tagging (preventing fuel deliveries and dispensing) and civil penalties — by the Unified Program Agency (UPA) or the State Water Resources Control Board (State Water Board). Penalties for UST systems that are out of compliance are $500 to $5,000 per day per UST.
UST Statutes and Regulations are available here:
1984
Installing new single-walled tanks is prohibited under CA HSC chapter 6.7.
1989
California established the Replacement of Underground Storage Tanks (RUST) Program.
1998
California requires UST owners/operators upgrade UST systems.
2014
Senate Bill 445 passes,requiring the closure of single-walled USTs by December 31, 2025.
2015
Installation of single-walled USTs is prohibited nationwide.
June 30, 2025
Deadline for owners/operators to apply for reimbursement of costs for removal of single-walled USTs by December 31, 2025.
Dec. 31, 2025
Deadline for all single-walled USTs to be permanently closed.
Resources
Questions or Comments
For more information regarding the enforcement of single-walled USTs, please contact ooe-ustunit@waterboards.ca.gov.
Map and List of Facilities with a Single-Walled Tank and/or Piping
The State Water Board has provided an interactive map of single-walled USTs and/or piping that were required to be permanently closed by the December 31, 2025 deadline. The map utilizes live data from GeoTracker, the California Environmental Reporting System (CERS), and surveys from UPAs to display the most current single-walled UST information statewide. The map includes the following filters: facility owner type, tank use, UPA, Regional Water Board boundaries, CalEnviroScreen 4.0 scores, Replacing, Removing, or Upgrading Underground Storage Tanks (RUST) application status, and the distance to public drinking water wells and nearest gas station.
Single-walled Facility List
Guidance for the Closure of Single-Walled UST Systems
The State Water Board prepared the following guidance documents – for owners, operators, and UPAs to navigate the single-walled closure requirements and enforcement actions for single-walled USTs that did not permanently close by December 31, 2025. LG 171 summarizes the main provisions of SB 445 as they apply to UST design and construction and addresses common questions from owners, operators, and UPA staff regarding permanent closure of USTs that do not meet all the requirements of H&SC, section 25291(a)(1)-(6).
- NEW – Notice of Single-Walled UST Enforcement (2026)
- Single-Walled UST Enforcement for Unified Program Agencies (2025)
- Single-Walled UST Enforcement Guidance for Unified Program Agencies (2023)
- UST Closure Deadline Reminder for Single-Walled UST Owners and Operators (2023)
- LG 171 – Permanent Closure of Underground Storage Tanks
Available Funding
Closure of Single-Walled UST Systems
Loans and grants made available through the RUST Program can assist eligible small businesses with the costs necessary to remove, replace, or upgrade single-walled USTs. As RUST grants are limited year-to-year; it is best to utilize these resources as soon as possible.
Cleanup of Single-Walled UST Systems
If a release is discovered upon permanent closure, the owner or operator may need to undertake corrective action (i.e., investigate and clean up the release). Filing a claim application with the UST Cleanup Fund, completing corrective action, and receiving reimbursement for eligible corrective action costs is a lengthy process. The deadline for submittal of a claim application to the UST Cleanup Fund for reimbursement of eligible costs for corrective action is December 31, 2034. The UST Cleanup Fund sunsets on January 1, 2036. Therefore, it is best for owners and operators to utilize these resources as early as possible.
