1. (a) Owners or operators must implement a monitoring program capable of detecting an unauthorized release from any portion of the underground storage tank system at the earliest possible opportunity.

2. (b) Underground storage tank systems must be monitored once the system is operational until the system is permanently closed in accordance with article 8.

   1. (1) Except as provided in paragraph (2), release detection equipment must only be disabled during testing, replacement, or repair by a service technician with notification to the Unified Program Agency.
   2. (2) The Unified Program Agency must require the owner or operator to implement an alternative monitoring program if interstitial monitoring release detection equipment is or is expected to be non-functional for more than 24 hours. The alternative monitoring program must include physical monitoring of the secondary containment for releases of hazardous substances from the primary containment at a frequency determined by the Unified Program Agency, but no less than once every 24 hours. Each time alternative monitoring is performed, the results must be recorded in the facility's monitoring records.

   3. (3) If the release detection system is or is expected to be non-functional for more than 30 days, the owner or operator must meet the requirements for temporary closure as specified in article 8.

      (c)(1) Release detection equipment used to monitor underground storage tanks must meet the requirements of subdivision (d) and be installed, calibrated, operated, and maintained in accordance with manufacturer's specifications.

   4. (2) Release detection equipment must only be remanufactured or rebuilt by the original manufacturer of the device. Remanufactured equipment is subject to third party testing pursuant to subdivision (d).

3. (d) Release detection methods and equipment must be certified as in compliance with the performance standards specified in this section and will be subject to any limitations specified in the certification. This certification must be obtained by the equipment manufacturer following one of the following evaluation procedures:

   1. (1) An independent third party testing laboratory must evaluate and approve the method using the appropriate EPA method for release detection equipment;
   2. (2) An independent third party testing laboratory must evaluate and approve the method using a voluntary consensus standard that is intended for the method being evaluated. The evaluation results must contain the same information and must be reported following the same general format as the EPA standard results sheet for any corresponding EPA method; or

   3. (3) An independent third party testing laboratory must evaluate and approve the method using a procedure deemed equivalent to an EPA method. Any resultant certification must include a statement by the association or laboratory that the conditions under which the test was conducted were at least as rigorous as those used in the EPA method. This certification must contain the same information and must be reported following the same general format as the EPA standard results sheet for any corresponding EPA method, and must contain statements that:

      1. (A) The method was tested under various conditions that simulate interferences likely to be encountered in actual field conditions which are no less rigorous than the environmental conditions used in the corresponding EPA method;
      2. (B) Each condition under which the method was tested was varied over a range expected to be encountered in 75 percent of the normal test cases;
      3. (C) All portions of the equipment or method evaluated received the same evaluation;
      4. (D) The amount of data collected and the statistical analysis are at least as extensive and rigorous as the data collected and statistical analysis used in the corresponding EPA method and are sufficient to draw reasonable conclusions about the equipment or method being evaluated;
      5. (E) The full-size version of the release detection equipment was physically tested; and
      6. (F) The experimental conditions under which the evaluation was performed and the conditions under which the method was recommended for use have been fully disclosed and that the evaluation was not based solely on theory or calculation.
4. (e) Except as provided in subdivision (g), secondary containment of Type 1 and Type 2 underground storage tanks must be monitored using a continuous interstitial release detection system which meets the requirements of subdivision (d). The continuous release detection system must activate an audible and visual alarm when a release is detected and be approved by the Unified Program Agency.
5. (f) Interstitial spaces of Type 3 underground storage tanks must be monitored using a continuous vacuum, pressure, or hydrostatic interstitial release detection system which meets the requirements of subdivision (d). The continuous release detection system must activate an audible and visual alarm when a release is detected and be approved by the Unified Program Agency.

6. (g) Notwithstanding subdivision (e) and subparagraph 2652(a)(1)(A), monitoring of secondary containment for Type 1 underground storage tanks may be performed using visual monitoring if all the following conditions are met:

   1. (1) All exterior surfaces of the underground storage tank, and the surface of the secondary containment directly beneath the underground storage tank, must be able to be visually observed either directly or by using mirrors or cameras.
   2. (2) Visual inspections must be performed at least once each day, except on weekends and recognized state or federal holidays. Monitoring may be more frequent if required by the Unified Program Agency. The Unified Program Agency may reduce the frequency of visual monitoring to not less often than once every seven days in cases where facility employees are not normally present at the facility and when inputs to and withdrawals from the underground storage tank are infrequent. The inspection schedule must consider the minimum anticipated time during which the secondary containment is capable of containing any unauthorized release and the maximum length of time any hazardous substance released from the primary containment will remain observable on the surface of the secondary containment. The inspection schedule must be such that monitoring will occur on a routine basis when the liquid level in the tank is at its highest. The inspection frequency must be such that any unauthorized release will remain observable on the exterior of or the surface immediately beneath the underground storage tank between visual inspections. The evaluation of the length of time the hazardous substance remains observable must consider the volatility of the hazardous substance and the porosity and slope of the surface immediately beneath the underground storage tank.
   3. (3) If any liquid is observed around or beneath the primary containment, the owner or operator must have the liquid analyzed using a method approved by the Unified Program Agency to determine if an unauthorized release has occurred.
   4. (4) If necessary to determine whether the primary containment is no longer product tight, the owner or operator must have an integrity test conducted.
   5. (5) The inspection results and the liquid level in the tank at the time of each inspection must be recorded in the facility's monitoring records.
   6. (6) If an unauthorized release is confirmed, the owner or operator must comply with the applicable provisions of articles 4 and 7.
7. (h) Remote monitoring must provide an immediate notification of a facility employee or service technician.

Note: Authority cited: Sections 25299.3 and 25299.7, Health and Safety Code. Reference: Sections 25290.1, 25290.2, 25291, 25293 and 25404, Health and Safety Code; and 40 CFR Sections 280.40-280.45.

History

1. Amendment filed 8-9-91 as an emergency; operative 8-9-91. Text remains in effect uninterrupted pursuant to Health and Safety Code section 25299.7 (Register 92, No. 14).

2. Editorial correction of printing errors in History 1 (Register 92, No. 43).

3. Amendment filed 4-5-94; operative 5-5-94 (Register 94, No. 14).

4. Repealer and new section heading and section filed 10-28-2025; operative 1-1-2026 (Register 2025, No. 44).