California Code, Public Contract Code - PCC § 20695

Each contract shall be let to the lowest responsible bidder, who shall give such security as the commission requires for the full and faithful performance of the contract.  The amount and kind of security required shall be stated in the advertisement for bids.

The board may authorize the commission to make contracts without advertising for bids for any part of the work, the cost of which does not exceed five hundred dollars ($500).

The commission may reject any and all bids, and readvertise for bids for doing the whole or any part of the work, or the commission may, with the approval of the board, purchase material, hire or purchase machinery, apparatus or appliances and employ labor and do the work or any part thereof without readvertising for bids.