Mich. Comp. Laws § 235.4
The county drain commissioner shall apportion the per centum of the cost of construction of such drain which any township traversed or benefited thereby shall be liable to pay by reason of the benefit to the public health, convenience or welfare, or as the means of improving any highway, and he shall also apportion the per centum of benefits to accrue to any piece or parcel of land by reason of the construction of such drain, over and above the per centum assessed against such township as aforesaid, which per centum of benefits shall be apportioned upon and assessed against the lands benefited according to such assessment of benefits and which apportionments he shall announce at the time and place of letting, as provided in chapter 4. Such assessment of per centum for benefits shall thereupon be subject to review and correction, and may be appealed from in the manner hereinafter provided.
MCL 235.4