Mich. Comp. Laws § 45.586
For a public corporation that is a county, the establishment of a solid waste system, the method of financing the system, and all contracts relating to the financing, acquisition, operation, maintenance, and administration of the system, including all contracts between the county and a public corporation, including itself, relating to the system, shall be approved by a resolution adopted by a majority of the members elect of the county board of commissioners. The department of solid waste management may, as provided in the resolution of the county board of commissioners, acquire the system or make improvements and improve, enlarge, extend, operate, and maintain the system, subject to any restrictions placed on the department by the county board of commissioners in a resolution or by this act. A county may merge 2 or more systems established by that county by resolution adopted by a majority of the members elect of its county board of commissioners. After such a resolution is adopted, the merged system may be improved, enlarged, extended, operated, and maintained under this section as a single system serving the total areas of the separate systems. However, a merger under this subsection does not affect either the rights or obligations acquired by a public corporation under contract with respect to an established system or the security of bonds or the prompt payment of the principal of or the interest on the bonds.
MCL 45.586