California Code, Health and Safety Code - HSC § 25299.31

(a) Every owner and operator shall establish and maintain evidence of financial responsibility, as provided in this article, for taking corrective action and compensating third parties for bodily injury and property damage arising from operating an underground storage tank.

(b) If the owner and the operator are separate persons, either the owner or the operator shall demonstrate compliance with subdivision (a).

(c) An owner may comply with this article by entering into an agreement with the operator of the tank requiring the operator to demonstrate compliance with subdivision (a). However, both the owner and the operator are in violation of subdivision (a) if evidence of financial responsibility is not established and maintained in accordance with this article.