California Code, Health and Safety Code - HSC § 79200

(a) A potentially responsible party may request the department or the regional board, when appropriate, to prepare or approve a remedial action plan for a site not listed pursuant to Article 5 (commencing with Section 78760) of Chapter 4, if the department or the regional board determines that a removal or remedial action is required to respond to a release of a hazardous substance. The department or the regional board shall respond to a request to prepare or approve a remedial action plan within 90 days of receipt.

(b) This section does not affect the authority of a regional board to issue and enforce a cleanup and abatement order pursuant to Section 13304 of the Water Code or a cease and desist order pursuant to Section 13301 of the Water Code.