California Code, Health and Safety Code - HSC § 79400

(a) In any judicial action under this part, judicial review of any issues concerning the adequacy of any response action taken or ordered by the department shall be limited to the administrative record. Otherwise applicable principles of administrative law shall govern whether any supplemental materials may be considered by the court.

(b) If the court finds that the selection of the response action was not in accordance with law, the court shall award only the response costs or damages that are not inconsistent with the national contingency plan, as specified in Part 300 (commencing with Section 300.1) of Subchapter J of Chapter I of Title 40 of the Code of Federal Regulations, and any other relief that is consistent with the national contingency plan.

(c) In reviewing an action brought by the department under this part, in which alleged procedural errors by the department are raised as a defense, the court may impose costs or damages only if the errors were serious and related to matters of central relevance to the action, so that the action would have been significantly changed had the errors not been made.