1. (a) For each gas storage well, the operator shall maintain a Gas Storage Well Chemical Inventory that lists all chemical constituents that may be emitted from a gas storage well in the event of a reportable leak as defined in Section 1726.9, subdivision (a). The Gas Storage Well Chemical Inventory shall identify on a well-by-well basis all chemical constituents found in materials of any phase that may be emitted from the well.

   1. (1) For purposes of this section, materials that may be emitted from the well include, but are not limited to:

      1. (A) The formation fluids;
      2. (B) Gas in the storage reservoir;
      3. (C) Wellbore-produced fluids;
      4. (D) Materials intentionally placed in the well for any purpose including well maintenance and control, such as, but not limited to, lubrication fluids, corrosion inhibitors, dissolved salts, biocides, well control fluid, radioactive tracers, paint pills, nitrogen gas, mud slurry, cement, lost circulation material, methanol, glycols, and water.
   2. (2) For purposes of this section, fluids include suspended or entrained solids.
2. (b) Gas Storage Well Chemical Inventories shall include the Chemical Abstract Service Number of each chemical constituent identified. If a chemical does not have a Chemical Abstract Service number, then the operator shall provide other available identification information.

3. (c) Operators shall perform baseline analytical tests to establish presence, and if possible, quantification of chemical constituents present in the reservoir, and when present, operator shall include those constituents in the Gas Storage Well Chemical Inventories.

   1. (1) At minimum, the operator shall test for hydrogen sulfide, benzene, toluene, ethylbenzene, xylenes, formaldehyde, radon-222 and metals including arsenic, silver, barium, beryllium, copper, cadmium, cobalt, chromium (total), chromium-6, mercury, molybdenum, nickel, lead, selenium, titanium, vanadium, and zinc.

      1. (A) Sampling and testing for radon-222 shall be conducted at the end of an injection season or when the reservoir is near its maximum inventory for the year to best estimate peak radon-222 concentration.
      2. (B) Testing for metals shall be done from a liquid sample if available.
   2. (2) The resulting analytical test laboratory reports and analysis shall be provided to the Division including chain of custody documentation.
   3. (3) The analytical baseline testing required by this section shall be completed and any chemical constituents detected shall be included in the Gas Storage Well Chemical Inventories as soon as practicable but no later than July 1, 2026.
   4. (4) The Division may require additional testing and analysis based on indication that other potentially harmful chemicals may be found in the reservoir.

4. (d) The operator shall develop and adhere to a protocol for maintaining and providing to the Division Gas Storage Well Chemical Inventories, submitted by January 1, 2026, to the Division for review. The protocol shall meet the following requirements:

   1. (1) The protocol shall include procedures to ensure that whenever material, except storage gas, is intentionally placed in the well, all the chemical constituents of the material are identified and promptly included in the Gas Storage Well Chemical Inventories. At a minimum, the protocol shall include procedures to track the following data in the inventories:

      1. (A) The date when a chemical constituent is placed in the well;
      2. (B) The volume, within a 10 percent margin of error, of each chemical constituent placed in the well on a given date; and
      3. (C) The cumulative volume, within a 10 percent margin of error, of each chemical constituent placed in the well.
   2. (2) Storage gas presence and composition must be included in the Gas Storage Well Chemical Inventories and submitted annually in compliance with Section 1726.4(a)(6)(E).
   3. (3) The protocol shall include procedures to be implemented in the event of a reportable well leak to ensure that the operator will confirm that the Gas Storage Well Chemical Inventory on file with the Division is current and complete, and if not, promptly provide the Division with an updated Gas Storage Well Chemical Inventory. In addition, if well control fluids are used to kill the well in response to a leak, then within five days of the use of these well kill fluids the operator shall provide an updated Gas Storage Well Chemical Inventory which also includes each chemical constituent of the kill fluid. These procedures shall be incorporated into the Emergency Response Plan required under Section 1726.3.1.
   4. (4) The protocol shall require that the chemical information for each gas storage well is specifically identified, recorded, maintained, and reported by well in the well's Gas Storage Well Chemical Inventory.
   5. (5) If the operator is unable to obtain information about chemical composition of a material for any reason, including, but not limited to, assertion by the supplier of trade secret protections, then the operator shall immediately notify the Division with the name and contact information of the supplier and available information about the well kill materials or chemicals therein.
   6. (6) The protocol shall require the operator to provide Gas Storage Well Chemical Inventories to the Division in a digital format by July 1, 2026, and provide updated Gas Storage Well Chemical Inventories to the Division every twelve months thereafter. The protocol shall also call for submittal of updated Gas Storage Well Chemical Inventories to the Division along with well summaries for permitted well work in accordance with Section 1724.1.
   7. (7) The protocol shall include a workplan for completing the baseline analytical testing and analysis requirements referenced in subdivision (c).
   8. (8) If the protocol is updated it shall be submitted to the Division for review along with the next Gas Storage Well Chemical Inventory submission.

Note: Authority cited: Sections 3013, 3106 and 3180, Public Resources Code. Reference: Sections 3011, 3106, 3180, 3181, 3181.5, 3183, 3220 and 3403.5, Public Resources Code.

History

1. New section filed 6-28-2018; operative 10-1-2018 (Register 2018, No. 26).

2. Renumbering of section 1726.4.3 to section 1726.4.4 and new section 1726.4.3 filed 5-1-2025; operative 7-1-2025 (Register 2025, No. 18).