Cal. Public Contract Code § 20783

When work is done by the district itself by force account, the amount shall not exceed five thousand dollars ($5,000). When the expenditure required for the work exceeds thirty-five thousand dollars ($35,000), it shall be contracted for and let to the lowest responsible bidder after notice. The notice inviting bids shall set a date for the opening of bids. The first publication or posting of the notice shall be at least 10 days before the date of opening the bids. Notice shall be published at least twice, not less than five days apart, in a newspaper of general circulation, printed and published in the district, or if there is none, it shall be posted in at least three public places in the district that have been designated by the district board as the places for posting this notice. The notice shall distinctly state the work to be done. In its discretion, the district board may reject any bids presented and readvertise. If two or more bids are the same and the lowest, the district board may accept the one it chooses. If no bids are received, the district board may have the work done without further bid. If all bids are rejected, the district board, on a resolution adopted by a four-fifths vote, may declare that the work can be performed more economically by day labor, or the materials or supplies furnished at a lower price in the open market and may have the work done in a manner stated in the resolution in order to take advantage of this lower cost. If there is a present or anticipated great public calamity, including an extraordinary fire, flood, storm, or other disaster the district board may, by resolution adopted by a four-fifths vote declaring that the public interest and necessity demand immediate expenditure of public money to safeguard life, health, or property, expend any sum required in the emergency without submitting the expenditure to bid. Cost records of the work shall be kept in the manner provided in Sections 4000 to 4007, inclusive, of the Government Code. This section shall not apply to sewerage maintenance, repair work, or to any uncompleted works under construction by district forces prior to the enactment of this section, and shall not be construed to exempt any work from Part 7 (commencing with Section 1720) of Division 2 of the Labor Code.