Mich. Comp. Laws § 123.740
The establishment of a county water supply, sewage disposal or refuse system or the making of county lake improvements or erosion control systems shall be approved by a majority of the members elect of the county board of commissioners. Prior to approval of lake improvements the county board of commissioners shall submit to the department of natural resources preliminary plans which provide for making the lake improvements for the department of natural resources' review and approval. Before approval of erosion control systems the county board of commissioners shall submit to the department of natural resources preliminary plans for the department's review and approval. Before construction of erosion control systems final plans and specifications shall be approved by the department. After the county board of commissioners' approval, the board of public works shall have power to acquire the system or make improvements and to improve, enlarge, extend, operate, and maintain the same, subject to any restrictions placed thereon by the county board of commissioners in the resolution establishing the same or by this act. Any 2 or more systems established by a county and the areas served thereby may be merged or combined by resolution adopted by a majority of the members elect of its county board of commissioners after which the merged or combined systems may be improved, enlarged, extended, operated, and maintained under this act as a single system serving the total areas of the systems but a merger or combination shall not affect either the rights and obligations acquired by a municipality by any contract with respect to an established system or the security of any bonds or the prompt payment of principal or interest thereon. A resolution adopted by the governing body of any city, village, township, or charter township authorizing and approving a contract with a county acting through its board of public works with respect to the financing or location of or service from any sewage disposal or refuse system constitutes, notwithstanding any statutory or charter limitation to the contrary, a permit to acquire, improve, enlarge, extend, operate, and maintain the sewage disposal or refuse system within the corporate limits of the city, village, township, or charter township, but no treatment or disposal plants, incinerators, works, grounds, filter beds, or other similar sewage or refuse disposal facilities, sanitary landfills, or dumps shall actually be located in any municipality without a resolution and contract.
MCL 123.740