California Code, Public Contract Code - PCC § 20942

The board of supervisors shall determine the amount of work to be done in each year and the place where such work is to be done, and may let a contract for any portion of such work that they may think proper.  When the work is let by contract, either as a whole work or for a portion thereof, the board shall give notice, by publication thereof, not less than 10 days, in a newspaper published in such county, calling for bids for the construction of such work, or of any portion thereof;  if less than the whole work is advertised, then the portion so advertised must be particularly described in such notice.  Said notice shall set forth that plans and specifications can be seen at the office of the board, and that the board will receive sealed proposals therefor, and that the contract will be let to the lowest responsible bidder, stating the time and place for opening said proposal, and how such sealed proposals shall be addressed, which, at the time and place appointed, shall be opened, and, as soon thereafter as convenient, the board shall let said work, either in portions or as a whole, to the lowest responsible bidder;  or they may reject any and all bids and readvertise for proposals.  Any person or persons to whom a contract may be awarded shall enter into a bond, with good and sufficient sureties, to be approved by the board, payable to said county for the use of such protection district, for double the amount of the contract price, conditioned for the faithful performance of said contract.  The work shall be done under the direction and to the satisfaction of the board of supervisors.