Cal. Health & Safety Code § 78435

The department, a representative of the department, or any person designated by the director may take the actions specified in this article only if there is a reasonable basis to believe that there has been or may be a release or threatened release of a hazardous substance, and only for the purpose of determining under this part the need for a response action, the choosing or taking of a response action, or otherwise for the purpose of enforcing this part.