California Code, Water Code - WAT § 60231

(a) The powers and duties herein enumerated, except as otherwise expressly provided, shall be exercised and performed by the board of the district.  If an existing agency has facilities available and adequate to accomplish any part of the purposes of a district created under this act, the district shall investigate and determine the cost of contracting for the accomplishment of that purpose through that existing agency.  Thereupon, the board shall make a finding, by resolution and supported by evidence, whether or not the purpose proposed to be accomplished by the district can be achieved more economically and for the best interests of the area to be benefited by entering into such a contract with an existing agency.  If the board finds that such contract is more economical and for the best interests of the area to be benefited, it shall so contract for the accomplishment of said purpose, if such agency so agrees.  The purpose of this section is to avoid duplication of similar operations by existing agencies and replenishment districts.

(b) Prior to constructing, leasing, purchasing, or contracting for a capital improvement project, a district shall determine the feasibility of such a project by ordering or preparing and reviewing a cost-benefit analysis based upon reasonable assumptions.