California Code, Health and Safety Code - HSC § 79030

(a) A person issued an order pursuant to Section 78870 or 79055 may identify additional potentially responsible parties for the site to which the order is applicable and may request the department to issue an order to those parties. The request shall include, with appropriate documentation, the factual and legal basis for identifying those parties as potentially responsible parties for the site.

(b) The department shall review the request and accompanying information and, within a reasonable period of time, determine if there is a factual and legal basis for identifying other persons as potentially responsible parties, and notify the person that made the request of the action the department will take in response to the request.