65 ILCS 5/11-140-4
When the corporate authorities of a municipality determine to construct improvements provided for in Section 11-140-1, they shall do so by an ordinance which shall prescribe whether the improvements shall be made by special assessment or by special taxation. The ordinance shall also prescribe the nature, character, locality, and description of the improvements, either by setting forth the same in the ordinance itself, or by reference to maps, plats, plans, profiles, or specifications thereof on file in the office of the municipal clerk, or by both methods.
The ordinance shall also describe by reasonably well understood boundaries, those portions of the municipality the sewerage of which is to be conducted by sewers already laid, or by those contemplated to be laid, into and through the outlet sewer provided for by Section 11-140-1. This property within those boundaries shall be assessable for the cost of this outlet sewer improvement. If property is to be taken or damaged for this improvement, the ordinance shall describe the property with reasonable certainty.
65 ILCS 5/11-140-4