California Code, Government Code - GOV § 25718

Upon the adoption of the plan by the board of supervisors, it shall be submitted to each affected city within the county for approval or disapproval. In reaching a determination each city shall consult with any public water supply agency or any agency owning or operating water pollution control facilities which serves any portion of the territory of the city. Within 90 days from the date of such submission each such city shall, by resolution, either approve or disapprove the plan. The failure of any city to act within 90 days shall be considered approval of the plan.