Mich. Comp. Laws § 69.5

Sec. 5. The council may raise by special assessment upon the lands in sewer districts and special assessment districts, for the purpose of defraying the cost and expense of grading, paving, and graveling streets, and for constructing drains and sewers, and for making other local improvements, charged upon the lands in the district in proportion to frontage or benefits, such sums as they shall consider necessary to defray the costs of the improvements.