Cal. Wat. Code § 75012
At the hearing the board may make such changes in the boundaries of the proposed improvement district as it deems advisable and shall define and establish the boundaries, but the board shall not modify the boundaries so as to exclude from the proposed improvement district any territory which may be benefited by the improvement district, or include within the proposed improvement district any land which will not in its judgment be benefited by the formation thereof.
If any additional lands are included in the proposed improvement district, the hearing of the petition shall be continued and the owners of the added lands shall be given not less than 20 days' personal notice of the addition of such lands to the improvement district.
Ca. Water Code § 75012