California Code, Public Contract Code - PCC § 20941

(a) All work done in any district shall be ordered by the board of supervisors of the county in which the district is located and shall be under the direction of the county surveyor or county engineer. All work which exceeds an estimated cost of one thousand dollars ($1,000) shall be advertised and let to the lowest bidder; provided, however, that at the time of an emergency the board of supervisors may order emergency work done without advertising for bids. If notice for bids to let contracts will not be given, the board of supervisors shall comply with Chapter 2.5 (commencing with Section 22050).

(b) As soon as the district is formed, the board shall cause a survey of the contemplated improvements to be made, or adopt a survey already made, and shall also cause a map of the survey, and plans and specifications showing the improvements in detail, to be prepared, and they shall adopt those surveys, maps, plans, and specifications, and thereafter all improvements shall be made in accordance with the surveys, maps, plans, and specifications so adopted; provided, that at any time after the adoption of said surveys, maps, plans, and specifications, and before the commissioner's report of assessment of benefits and award of damages has been finally adopted and confirmed by the board, the board may rescind their action in adopting those surveys, maps, plans, and specifications, and may modify the same or adopt others in their place, in which case a new assessment shall be made, or may, by a four-fifths vote of the members, abandon the contemplated improvement and dissolve the protection district, in which case the expenses already incurred on behalf of the district shall be a county charge.