State Water Board staff detail Chapter 16 rewrite tightening UST construction, monitoring and closure rules

State Water Resources Control Board staff presented a comprehensive rewrite of Chapter 16 governing underground storage tanks, saying the regulations were adopted by the board on Sept. 3 and are currently under review by the Office of Administrative Law and expected to become effective Jan. 1.

Austin Lemire Batin, an engineer and project manager for the chapter 16 rewrite, said the rule package reorganizes UST requirements into 10 articles and appendices and ‘‘includes our definitions of terms, exclusions, and record keeping requirements’’ as well as the construction, monitoring and testing standards that are the ‘‘meat and potatoes’’ of the update.

The rewrite standardizes terminology and definitions. The regulations define an ‘‘abandoned’’ UST as a tank that has had no functional release detection for more than 365 days, lacks a current operating permit, is not permanently or temporarily closed under the new regulations and is not ‘‘decommissioned.’’ The rules replace vague phrases such as ‘‘above ground’’ or ‘‘below grade’’ with ‘‘buried’’ and ‘‘unburied,’’ and introduce ‘‘continuity’’ (an open, testable interstitial space) and ‘‘zone’’ (a monitored interstitial unit) as determinative concepts for secondary containment monitoring.

Staff also established three installation‑date tank categories to align with Health and Safety Code dates: Type 1 (installed before 07/01/2003), Type 2 (installed between 07/01/2003 and 07/01/2004) and Type 3 (installed on or after 07/01/2004). Austin said the definitions match the Health and Safety Code and that the categories are intended to clarify applicable testing and retrofit expectations.

Electronic submittals and recordkeeping receive clearer definitions. The rewrite defines ‘‘submit’’ to mean owner/operator filings to Unified Program Agencies (UPAs) via CERS or to cleanup oversight agencies via GeoTracker; other deliveries (hand, mail, email or fax) remain permitted where not explicitly required to be submitted. Records tied to a UST system (installation, test results, as‑built drawings, repair documentation and calibration charts) must be kept for the life of the system; approved off‑site records must be produced within 36 hours of request.

Monitoring, testing and certification requirements are tightened. Release detection equipment must be tested annually and some test reporting deadlines have been shortened: electronic leak detection (ELD) test results submittals are shortened from 60 days to 30 days. Staff said continuity of interstitial spaces must be demonstrated periodically as part of release detection equipment certification and that test equipment itself must be calibrated and maintained per manufacturer guidance or by NIST where no manufacturer resource exists.

For line testing, staff said annual line tightness testing performed with line leak detectors must simulate a 0.1 gallon‑per‑hour leak at 150% operating pressure; staff noted this is a stricter sensitivity than prior practice (3 GPH at 10 psi) and that the change does not apply to Type 3 (VPH) systems, licensed tank tester methods or piping with fail‑safe interstitial monitoring.

The rules require continuity verification and bring certain mechanical detectors up to an electronic standard. Mechanical under‑dispenser containment devices that fail on or after Jan. 1, 2026 must be replaced with continuous electronic release detection before dispensing resumes, and systems with pressurized buried piping at remotely monitored, routinely unstaffed facilities will need continuous interstitial detection that stops flow when a release or monitoring malfunction is detected (requirement phased in for systems installed on or after July 1, 2026).

Construction and component changes are specified. Tanks installed on or after July 1, 2026 must bear a label with manufacturer ID, production location, date of manufacture, maximum burial depth and test pressure; tanks installed on or after Jan. 1, 2027 must be anchored to prevent flotation per manufacturer, industry code or a California‑registered professional engineer. Steel piping installed on/after Jan. 1, 2026 must meet ASTM A53 factory coating and minimum wall thicknesses (primary piping schedule 40; secondary piping schedule 10). Single‑wall, direct‑buried spill buckets that require replacement must be replaced with secondarily contained spill containment.

Inspection and personnel qualifications are clarified. The draft adds a class of independent compliance inspectors who must be independent of the inspected facility and the UPA and hold ICC UST inspector certification; UPAs’ own UST inspectors must obtain ICC certification within 180 days of when they begin performing UST inspection duties. Designated UST operator (DO) identification moves into SIRS NextGen, and the DO name in SIRS must match exactly the name on the ICC UST system operator certificate. DO visual inspection reports must include a dated alarm history from the release detection system or the facility alarm log if the system cannot generate the report.

Closure, sampling and reuse rules were revised. Temporary closure requires UPA approval before initiation and inspections every 90 days; permanent closure must be completed within 365 days after the system stops storing hazardous substances. Soil sampling at permanent closure must occur immediately after tank/piping removal with samples taken a minimum of 2 feet into native material and additional samples for larger or compartmented tanks; piping sampling will be required every 20 linear feet (rigid piping at each change in direction) and beneath each dispenser. Tanks intended for reuse must be permanently closed prior to relocation unless the UPA approves otherwise; relocated tanks to store hazardous substances must be recertified by the manufacturer and an independent testing organization no more than 30 days before reinstallation and must meet Chapter 4–6 requirements and Health and Safety Code section 25290.1. Abandoned tanks may return to operation only if upgraded to VPH interstitial detection and they pass an enhanced leak detection test.

Enforcement and communications were clarified. The State Water Board and UPAs must implement inspection‑and‑enforcement (IME) plans that use the three‑tier violation classification (minor, class 2, class 1). The board can issue red tags, must notify the UPA within 24 hours, and may request the UPA perform related inspections or duties; red‑tagged tanks must not dispense through dispensers and UPAs or the board may direct emptying within a timeframe not to exceed 48 hours.

Forms (appendices) will be updated and moved into new SIRS NextGen data fields. Staff described multiple updated appendices (facility employee training, DO visual inspection, release detection testing, secondary containment testing, overfill prevention testing, and continuation pages for sites with many sensors or sumps). Several forms shift from recording the date of last test to recording the next test due date to reduce late testing cycles.

Next steps and contact information: Austin said guidance documents, updated UST forms and implementation instructions will be prepared and posted, and he provided a chapter 16 info page link and a listserv for updates.