Michigan Compiled Laws, Chapter 280. Drain Code of 1956 § 280.561

Sec. 561. After adoption of the official plans, the commission shall proceed to tentatively establish the percentage of cost of the project to be assessed against public corporations within each county within the district, and against the state and counties on account of drainage and prevention of flooding of state and county highways. The percentage of cost so apportioned to public corporations in each county shall then be apportioned by the commission among public corporations to be assessed in such county, which determination shall be filed with the secretary of the board.