Cal. Streets and Highways Code § 35402.3

If at any time, either before or after issuing bonds, the legislative body so determines, it may at one time or from time to time add to, eliminate, change or otherwise modify any of the proposed acquisitions and improvements after notice and hearing in the same manner as provided in Sections 35270 to 35272, inclusive, but no such addition, elimination, change or modification shall be made unless following such hearing the legislative body shall determine that all of the territory within the district as originally formed or as changed pursuant to Section 35402.4, as the case may be, will be benefited by the acquisitions and improvements remaining after such addition, elimination, change or modification. Any such addition, elimination, change or modification shall be effected by an ordinance amending the ordinance declaring the district formed and describing the acquisitions and improvements to be made. No such addition, elimination, change or modification shall be made in violation of the provisions of any ordinance, resolution or indenture providing for bonds already issued.