Mich. Comp. Laws § 280.261

Sec. 261. Within 10 days after the letting of contracts, or in case of an appeal, then forthwith after such appeal shall have been decided, the commissioner shall make a computation of the entire cost of such drain, which shall include (1) all the expense of laying out and designating the drainage district, which item of expense shall include the entire cost of the survey; (2) the expense of locating, establishing and constructing the drain; (3) the fees and expenses of special commissioners; (4) the compensation to be paid the board of review; (5) the cost of construction of bridges and culverts; (6) the contracts for the construction of the drain, or other work to be done on said drain; (7) the estimated cost of an appeal in case the apportionment made by the commissioner shall not be sustained; (8) the estimated cost of inspection; (9) the cost of publishing all notices required; (10) all fees of the probate judge; (11) attorney fees for legal services in connection with the drain; and (12) interest on bonds for the first year, if bonds are to be issued, and he shall add the whole into a gross sum and add thereto not less than 10% nor more than 15%, at the discretion of the drain commissioner, of said gross sum to cover contingent expenses, and the entire sum so ascertained shall be deemed to be the cost of construction of such drain.