California Code, Public Utilities Code - PUC § 40335

The board is authorized to impose a maximum tax rate of 1 percent under this article and the board may state the maximum tax rate in terms of not to exceed 1 percent, or any lesser percentage thereof.  The district shall not levy the tax at a rate other than 1, 3/4, 1/2, or 1/4 percent, unless specifically authorized by the Legislature.  The board, in the ordinance, may provide for limitations upon the time when the tax shall be in effect, or the board may provide that the tax shall be in effect until repealed.  Any tax rate or maximum tax rate adopted pursuant to this article, unless otherwise prohibited, may be increased when authorized by the board by ordinance adopted in the manner and by the vote stated in Section 40333 and approved by a majority of the votes cast by the qualified electors of the district voting at an election called for that purpose.