Cal. WAT § 31609

If a petition protesting against the adoption of the resolution declaring the improvement district to be formed is presented to the board prior to its effective date, the resolution shall be suspended and the board shall reconsider it. The petition shall be signed by not less than 10 percent of the registered voters within the proposed improvement district on the date of adoption of said resolution. If the board does not repeal the resolution against which a petition is filed, the board shall submit the resolution to the voters within such improvement district at a regular election or a special election for the purpose. The resolution shall not become effective unless and until a majority of the voters vote in favor thereof. Such election shall be conducted in the manner provided in Article 3 (commencing at Section 31405) of Chapter 2 of Part 6 of this division insofar as applicable, except that if a majority of the votes cast at said election are in favor of the resolution then the cost of such election shall be borne by the improvement district. This section shall not apply to any improvement district containing less than 100 registered voters as of the date of adoption of the resolution referred to in Section 31596.