Mich. Comp. Laws § 101.14

Sec. 14. The board of public works may charge and collect annually from persons whose premises are connected by private drains with the public sewers, such reasonable sum, not exceeding 2 dollars per year, as they may deem just, in proportion to the amount of drainage through such private drain; and such charge shall be a lien upon the premises, and may be collected by special assessment thereon, or otherwise.