Wis. Stat. § 87.13
All sums which shall be deposited with the secretary of administration under s. 87.07(4) for the construction of the improvement shall be paid by the secretary of administration to the flood control board upon requisitions from said board. If any moneys, other than those for operation and maintenance during the first 18 months, remain unexpended in the hands of the flood control board or subject to their requisition after the completion of the construction of the improvement, and if the funds for construction of the improvement shall have been in part raised through voluntary contributions under s. 87.07(4) or 87.11(2), the amounts thus contributed, or such proportion thereof as the funds remaining in the hands of the board or subject to its requisition will pay, shall be returned to the persons or corporations who made such voluntary contributions, in proportion to the amounts contributed by them.
Wis. Stat. § 87.13