Cal. Pub. Contract Code § 20394.5
Notwithstanding any other provision of this article, whenever the board of supervisors finds that the estimated expense of any work to be done upon any county highway is fifty thousand dollars ($50,000) or less, the board or the purchasing agent may have the work done by contract upon notice describing the work in general terms and stating a closing date for submission of bids.
Notice shall be published in a newspaper of general circulation printed and published within the jurisdiction of the county. Notice shall be published in accordance with Section 6066 of the Government Code and shall be completed at least 48 hours before the time scheduled for opening of the bids. Notice inviting bids may also be published in a trade publication.
The successful bidder shall give a bond in the amount the board requires, conditioned on the faithful performance of the contract, and on the payment of all labor employed and material used in the work.
The board may delegate its authority under this section to the county road commissioner.
Ca. Pub. Cont. Code § 20394.5