HSC §25298: (a) No person shall abandon an underground tank system or close or temporarily cease operating an underground tank system, except as provided in this section.

(a) No person shall abandon an underground tank system or close or temporarily cease operating an underground tank system, except as provided in this section. (b) An underground tank system that is temporarily taken out of service, but which the owner or operator intends to return to use, shall continue to be subject to all the permit, inspection, and monitoring requirements of this chapter and all applicable regulations adopted by the board pursuant to Section 25299.3, unless the owner or operator complies with subdivision (c) for the period of time the underground tank system is not in use. (c) No person shall close an underground tank system unless the person undertakes all of the following actions: (1) Demonstrates to the local agency that all residual amounts of the hazardous substance or hazardous substances which were stored in the tank system prior to its closure have been removed, properly disposed of, and neutralized. (2) Adequately seals the tank system to minimize any threat to the public safety and the possibility of water intrusion into, or runoff from, the tank system. (3) Provides for, and carries out, the maintenance of the tank system as the local agency determines is necessary for the period of time the local agency requires. (4) Demonstrates to the appropriate agency, which has jurisdiction over the site, that the site has been investigated to determine if there are any present, or were past, releases, and if so, that appropriate corrective or remedial actions have been taken.