Underground Storage Tank (UST) Facility File Selection Process

In preparation for a Certified Unified Program Agency (CUPA) Performance Evaluation, the State Water Resources Control Board (State Water Board) will identify and select UST facilities within a CUPA’s jurisdiction for review.   State Water Board staff (staff) use the following UST facility file selection criteria to select the appropriate number and type of facility files for the CUPA Performance Evaluation:

File Selection

The number of UST facilities within a CUPA’s jurisdiction is determined using the most recent Report 6 UST facility count.

The table below depicts the minimum and maximum number of facility files that typically will be requested per total number of CUPA UST facilities:


Number of Files Requested

Number of UST Facilities



1 to 10



11 to 100



101 to 250



251 to 750



751 to 1000+



Selection Criteria

Staff consider the following criteria when choosing the number of facility files for review, including but not limited to:

Single Walled USTs

Single-walled USTs that meet the conditions described in California Health and Safety Code, chapter 6.7, section 25292.05 must be permanently closed no later than December 31, 2025.  Since the deadline is rapidly approaching, staff may request a disproportionate number of single-walled UST facility files as compared to secondarily contained UST facility files.  To assist the CUPAs in closing single-walled UST facilities before the deadline, staff will review items specific to single-walled USTs, including but not limited to tank lining inspections, cathodic protection system records, one-time and/or periodic enhanced leak detection (ELD) testing requirements for systems within 1,000 feet of a public drinking water well, and release detection methods using automatic tank gauges or electronic line leak detectors.

Previous Evaluations

CUPAs that have been approved for paperless Report 6 and have historically provided complete and accurate facility files during previous evaluations may have a reduced number of facility files requested in future evaluations.  While previous evaluations are considered, the State Water Board has the discretion to select from the number of UST facility files requested as outlined in the table above.

UST Construction Configurations and Status

Staff also consider the following UST system information during facility file selection:

  • Tank Construction
  • Piping Construction
  • Line Leak Detectors and Monitoring Systems
  • Public or Private UST ownership
  • Closures, Temporary Closures and Abandoned USTs

The decision on the number and type of facility files requested during the CUPA Performance Evaluation is not negotiable and will be determined exclusively by the State Water Board.  Staff may request additional files during the evaluation, if necessary, and use information in the California Environmental Reporting System (CERS) prior to or during the evaluation period.  Information that is captured from CERS and used by staff during the evaluation may be shared with the CUPA upon request.