Mich. Comp. Laws § 324.34122
Within 10 days after the letting of contracts, or, in case of an appeal, then immediately after the appeal has been decided, the chairperson of the irrigation board shall make a computation of cost of a project under this part, which shall include all preliminary costs, the cost of construction of the improvement, establishment of the special assessment district, the preparation of the tax roll, notices, advertising, printing, financing, legal, professional, engineering, inspection, condemnation expenses, interest on the bonds for the first year if bonds are to be issued and an amount not to exceed 10% of the gross sum to cover contingent expenses, and all other administrative costs incidental to making of the improvement or establishment of the irrigation special assessment district. The chairperson shall submit the computation of cost to the irrigation board for its approval, and, when the computation of cost is approved by the board or amended and approved by the board, it shall become the final computation of cost for the irrigation district.
MCL 324.34122