Water Code § 51346
ARTICLE 3. Operation and Maintenance Assessments
The operation and maintenance assessment roll shall be used for the purposes specified in Section 51326 until the board, or landowners representing at least 15 percent of the district lands, petition the board of supervisors for an order directing the valuation assessment commissioners who made the original operation and maintenance assessment roll or new valuation assessment commissioners, to be named in the order, to prepare a new operation and maintenance assessment roll.