Mo. Rev. Stat. § 204.656
The portion of the cost of any improvement to be assessed or imposed against the real property in a sanitary sewer improvement area shall be apportioned against such property in accordance with the benefits accruing by reason of such improvement. Subject to the provisions of the farmland protection act, sections 262.800 to 262.810, the cost may be assessed equally by lot or tract against property within the area, or by any other reasonable assessment plan determined by the governing body of the district that results in imposing substantially equal burdens or share of the cost upon property similarly benefitted. The governing body of the district may from time to time determine and establish by resolution reasonable general classifications and formula for the methods of assessing or determining the benefits.
§ 204.656, RSMo