Cal. Public Contract Code § 20761

Contracts for the doing of new construction work, the cost of which exceeds ten thousand dollars ($10,000), or the purchasing of supplies, the cost of which exceeds twenty-five thousand dollars ($25,000), or projects involving maintenance of buildings and improvements, the cost of which exceeds ten thousand dollars ($10,000), shall be let by the board upon competitive bidding. Notice of the proposed letting of a contract shall be given by publication pursuant to Section 6061 of the Government Code in the county in which the district is located, at least five days before the time fixed for opening bids. Bidding shall be by sealed proposals filed with the district upon forms furnished by it, and under such rules and regulations as the board may prescribe. All bids shall be publicly opened and declared under procedures established by the board, and the award of the contracts shall be made in open session of the board to the lowest and best responsible bidder. The board may reject any and all bids and readvertise in its discretion.