If the board determines that the estimated cost of a proposed project is greater than should be levied in a single year upon the lands benefited, it may fix the amount to be levied and collected each year and by resolution provide for issuance of bonds in an amount not to exceed the amount of unpaid assessment. The bonds shall bear interest payable annually or semiannually and shall mature in proportions and at times as assessments have been collected, not exceeding twenty years from issue.

Source: SDC 1939, § 61.1024; SDCL, § 46-21-23; SL 1983, ch 28, § 60; SL 1985, ch 362, § 120.