Wat. Code, § 1834

(a) In the event that a violation of a requirement described in subdivision (d) of Section 1831 is occurring or threatening to occur, the board shall give notice by personal notice, certified mail, in accordance with the manner of service of a summons under Article 3 (commencing with Section 415.10) of, and Article 4 (commencing with Section 416.10) of, Chapter 4 of Title 5 of Part 2 of the Code of Civil Procedure, or by any method of physical delivery that provides a receipt pursuant to which the party shall be informed that they may request a hearing not later than 20 days from the date on which the notice is received. The notice shall contain a statement of facts and information that would tend to show the proscribed action, and notification of the requirements of subdivision (b). For purposes of this subdivision, “physical delivery that provides a receipt” includes physical delivery methods that provide electronic confirmation of delivery to the intended address.

(b) Unless a written request for a hearing signed by or on behalf of the notified party is delivered to or received by mail by the board within 20 days after receipt of the notice, the board may adopt a cease and desist order, based on the statement of facts and information set forth in the notice, without a hearing.