Harb. & Nav. Code, § 7243

In any ordinance or resolution calling an election to authorize the issuance of revenue bonds of the district, the board may insert a provision that it intends to provide, as further security for the bonds, for a limited tax levy (stating the limit as to rate) which shall be levied from time to time to the extent to which revenues pledged to the payment of the principal of and interest on the bonds have been or are expected to be insufficient in any year to pay said principal and interest or to the extent to which any reserve fund established for said bonds has been or will be used to pay, or to provide for the payment of, such principal or interest. If such provision is so inserted and if the bonds are authorized by a fifty-one percent (51%) favorable vote, the board may insert in the ordinance or resolution providing for the issuance of such bonds a provision for such limited tax levy and such terms, conditions and covenants as may be necessary or convenient for the carrying out of such provision. The limited tax levies authorized by this section shall not in the aggregate exceed in any one year seventy-five cents ($0.75) on each one hundred dollars ($100) of assessed valuation.