Cal. Wat. Code § 56061
Notwithstanding any other provision in this chapter to the contrary, in the event that prior to the formation of a district a report has been secured by the board of supervisors of the county in which the district is formed pursuant to the provisions of Section 4.2 of the Drainage District Improvement Act of 1919 concerning the protection of lands and other property within the district from storm or waste waters and containing substantially the same data and matter required by Section 56050 of this chapter, and if copies of said report are made available to the district board by the board of supervisors of such county, a new report need not be prepared by the district board under said Section 56050 and the hearing or hearings referred to in this chapter may be held on such report furnished by the board of supervisors of such county, and thereafter all of the provisions of this chapter shall be applicable to such report.
Ca. Water Code § 56061