Mich. Comp. Laws § 280.23
The commissioner shall have jurisdiction over all drains within his county, including those heretofore established and now in process of construction. Drains extending into more than 1 county, or affecting lands in more than 1 county, shall be established and constructed in accordance with the provisions of this act regulating the establishment and construction of drains traversing more than 1 county or affecting lands in more than 1 county. Nothing in this act shall be construed as depriving a drain commissioner of jurisdiction or as making any drain an intercounty drain, merely because a drain extends into another county for the purpose of securing a proper outlet and not for the purpose of draining any lands in the other county: Provided, such extension is approved by the drain commissioners and the board of supervisors of each affected county. The portion of any such drain extending into another county shall not be considered in determining the number of signers required to a petition to locate, establish and construct.
MCL 280.23