Cal. Health & Safety Code § 4614.4

If any part of the district includes any unincorporated territory of the county, the governing body of the initiating city shall file with the board of supervisors of the county in which such unincorporated territory is situated a certified copy of its resolution adopted pursuant to Section 4607, which resolution shall contain a request that the board of supervisors consent to the formation of such district. The governing body of the initiating city shall not form the district unless prior to the conclusion of the hearing which is provided for by Section 4611 the board of supervisors of the county in which such unincorporated territory is located, by resolution, consents to the formation of the district which will include such unincorporated territory within its boundaries.