CA Water Code Section 31637.5

If the district has probable cause to believe that the production by any producer is unreported or, if reported, is substantially in excess of that disclosed by the statement filed by such producer, the district shall cause an investigation and report to be made concerning such production, which shall include the right to inspect the water-producing facility and any water-measuring device used therewith. The board shall thereupon determine and fix the correct amount of production for any such producer, and give written notice thereof. Any such determination made by the board shall be binding upon the producer, and the replenishment assessments based thereon together with interest and penalties shall be payable immediately, unless the producer shall file with the board within 10 days after the mailing of such notice a written protest setting forth the grounds of protest. Upon the filing of such protest the board shall hold a hearing at which time the total amount of production and the replenishment assessment shall be determined, and the interest and penalties fixed, which action shall be conclusive if based upon substantial evidence. A notice of such hearing shall be mailed to the protestant at least 10 days before the date fixed for the hearing. Notice of the determination by the board shall be mailed to the protestant. The producer shall have 20 days from the date of mailing of such notice to pay the replenishment assessment, interest, and penalties so fixed by the board.