Sec. 11. (a) The works board shall levy special assessments for the amount determined under section 10 of this chapter if:
(1) the contract for the improvement is executed; and
(2) the improvement is made.
(b) The special assessments levied under this section may not exceed the cost of the improvement.
(c) If the amount determined under section 10 of this chapter is less than the contract price, the remainder of the cost of the improvement is payable by the unit.