When a district board, by resolution, has caused special assessments to be levied to cover the cost of constructing a project, the board shall determine the rate of interest unpaid special assessments are to bear, which rate may not exceed one and one-half percent above the bond rate. Interest on unpaid special assessments commences on the date the assessments are finally confirmed by the board. Special assessments may be certified and made payable in equal annual installments, the last of which must be due and payable not more than thirty years after date of the bonds to be paid. The secretary of the district shall certify to the county auditor of the county in which the district is situated, or if the district embraces more than one county, to the county auditor of each county in which district lands subject to such special assessments are situated, the total amount assessed against each piece, parcel, lot, or tract of land. The secretary of the district shall also file with the county auditor of each county in which district lands lie a statement showing the cost of the project and the part of the project to be financed by special assessments. Funds needed to pay the cost of maintaining a project may be raised in the same manner as funds were raised to meet construction costs. If the project was financed in whole or in part through the use of special assessments, the district board shall prorate the cost of construction or, if a reassessment of benefits has been adopted, the costs must be prorated in accordance with the reassessment of benefits as authorized by section 61-35-65. The district treasurer shall annually certify to the county auditor all uncertified installments of assessments which are to be extended upon the tax lists of the district for the current year, in the manner provided in this section. The annual certification must continue until the amount of moneys on deposit in the fund established under section 61-35-83 is sufficient to cover outstanding principal of and interest on any obligations issued to fund the projects, and in addition, to repay the district for any payments made by the district to fund deficiencies in the fund established under section 61-35-83.