California Code, Health and Safety Code - HSC § 79670

(a) A person who has incurred response or corrective action costs in accordance with this part, Chapter 6.5 (commencing with Section 25100) of Division 20, or the federal act may seek contribution or indemnity from any person who is liable pursuant to this part.

(b) An action to enforce a claim may be brought as a cross-complaint by any defendant in an action brought pursuant to Section 79650 or this section, or in a separate action after the person seeking contribution or indemnity has paid response or corrective action costs in accordance with this part, Chapter 6.5 (commencing with Section 25100) of Division 20, or the federal act.

(c) A plaintiff or cross-complainant seeking contribution or indemnity shall give written notice to the director upon filing an action or cross-complaint under this section.

(d) In resolving claims for contribution or indemnity, the court may allocate costs among liable parties using appropriate equitable factors.