Pub. Contract Code, § 21501

(a) All contracts for any improvement or unit of work, when the cost according to the estimate of the engineer will exceed fifteen thousand dollars ($15,000), shall be let to the lowest responsible bidder or bidders as provided in this article. The board shall first determine whether the contract shall be let as a single unit, or divided into severable parts. The board shall advertise for bids by three insertions in a daily newspaper of general circulation or by two insertions in a weekly newspaper of general circulation printed and published in the agency, inviting sealed proposals for the construction or performance of the improvement or work. The call for bids shall state whether the work shall be performed in one unit or divided into parts. The work may be let under a single contract or several contracts, as stated in such call. The board shall require the successful bidders to file with the board good and sufficient bonds to be approved by the board conditioned upon the faithful performance of the contract and upon the payment of their claims for labor and material. The bonds shall comply with Chapter 5 (commencing with Section 9550) of Title 3 of Part 6 of Division 4 of the Civil Code. The board may reject any and all bids.

(b) The board may have work done by force account without advertising for bids or by informal bidding procedures in any of the following situations:

(1) All proposals are rejected.

(2) No proposals are received.

(3) The estimated cost of the work does not exceed fifteen thousand dollars ($15,000) until January 1, 1989. After January 1, 1989, the estimated cost of the work shall not exceed ten thousand dollars ($10,000).

(4) The work consists of channel protection.

(5) The work consists of maintenance work, except that informal bidding procedures may be used only where the estimated cost does not exceed twenty-five thousand dollars ($25,000).

(6) The work consists of emergency work. In case of an emergency, if notice for bids to let contracts will not be given, the board shall comply with Chapter 2.5 (commencing with Section 22050).

(c) The agency may purchase in the open market without advertising for bids, materials and supplies for use in any work, either under contract or by force account, except that, materials and supplies for use in any new construction work or improvement, except work referred to in subdivision (b), may not be purchased, if the cost exceeds fifteen thousand dollars ($15,000), without advertising for bids and awarding the contract to the lowest responsible bidder.

(d) As used in this section, “informal bidding procedures” means that the board shall, at a minimum, award a contract to the lowest responsible bidder after publishing a notice which generally describes the work to be performed and invites written bids in a newspaper of general circulation in the agency once a week for two successive weeks. The board shall obtain a minimum of three written bids.