Cal. Water Code § 13160

(b) (1) The state board is authorized to give any certificate or statement required by any federal agency pursuant to the Federal Water Pollution Control Act or any other federal water quality control law that there is reasonable assurance that an activity of any person subject to the jurisdiction of the state board will comply with applicable requirements of that federal law or any other appropriate requirements of state law.

(2) The state board may issue the certificate or statement under paragraph (1) before completion of the environmental review required under Division 13 (commencing with Section 21000) of the Public Resources Code if the state board determines that waiting until completion of that environmental review to issue the certificate or statement poses a substantial risk of waiver of the state board’s certification authority under the Federal Water Pollution Control Act or any other federal water quality control law. To the extent authorized by federal law, the state board shall reserve authority to reopen and, after public notice, an opportunity for comment, and, when appropriate, an opportunity for a hearing, revise the certificate or statement as appropriate to incorporate feasible measures to avoid or reduce significant environmental impacts or to make any necessary findings based on the information provided in the environmental document prepared for the project.

(c) The state board is authorized to exercise any powers delegated to the state and carry out any program a state is authorized to administer under the Federal Water Pollution Control Act (33 U.S.C. Sec. 1251 et seq.) and any amendments to that act.