Where it is proposed that a division assume only the operation and maintenance of the existing works, the contract for the operation and maintenance of the existing works must be submitted to the electors of the division for approval at a special election or the next district election or primary or general state election. The local board of directors, after the contract is made in pursuance of the authority granted in the election, may levy assessments or impose tolls and charges annually or otherwise to raise the amounts necessary to carry out the contract and to operate and maintain the works, including amounts to be paid to the United States pursuant to the contract, in the same manner and to the same effect as may be done by the board of directors of the district under the provisions of this chapter.