California Code, Public Contract Code - PCC § 21045

(a) The district shall require a person to whom the district awards a contract as a result of advertising for bids to enter into a bond, with good and sufficient sureties, to be approved by the board, payable to the district for its use, for at least 25 percent of the amount of the estimated contract price, conditioned for the faithful performance of the contract.

(b) The general manager of the district may require a person to whom the district awards a contract without advertising for bids to enter into a bond in accordance with subdivision (a).

(c) The work shall be done under the direction and to the satisfaction of the district engineer, and be subject to approval by the board.