Cal. Water Code § 75358

If the proceeds of bonds voted for the acquisition of properties for, or the construction of, any works or projects of the district are insufficient to pay the cost of such properties, works, or projects, then, in addition to the assessments mentioned in Section 75357, an assessment may be levied not to exceed one mill ($0.001) on each one hundred cents ($1) of the assessed value of lands within the district for not to exceed five fiscal years, for the payment of the remaining cost of such properties, works, or projects; provided, however, that no district shall levy more than one such special one mill ($0.001) assessment at any one time.