California Code, Public Utilities Code - PUC § 29157

If a majority of any board of supervisors does not approve the reports, the district may make additional studies and changes and may refer the amended reports to the board of supervisors of the counties comprising the district in order to obtain unanimous approval from the counties comprising the district.  If no agreement is reached within a period of six months following the date the original reports were received from the board, any county not approving the reports may withdraw from the district under Chapter 10 (commencing with Section 29650), notwithstanding that, after that county's disapproval, the reports are withdrawn by the district.  Failure of a county to withdraw from the district, within 30 days following the six-month period, has the same effect as approval by the board of supervisors of the county of the reports as last amended, unless the reports have been previously withdrawn by the district.