California Code, Health and Safety Code - HSC § 78080

“Operation and maintenance” means those activities initiated or continued at a hazardous substance release site following completion of a response action that are deemed necessary by the department or regional board in order to protect public health or safety or the environment, to maintain the effectiveness of the response action at the site, or to achieve or maintain the response action standards and objectives established by the final remedial action plan or final removal action work plan applicable to the site.