70 ILCS 2305/28
The board of trustees of any sanitary district may annex any territory which is not within the corporate limits of the sanitary district, provided:
The annexation shall be accomplished only by ordinance and the ordinance shall include a description of the annexed territory. The ordinance annexing non-contiguous territory shall designate the ward to which the land shall be assigned. A copy of the ordinance and a map of the annexed territory certified as true and accurate by the clerk of the annexing sanitary district shall be filed with the county clerk of the county in which the annexed territory is located. The new boundary shall extend to the far side of any adjacent highway and shall include all of every highway within the area annexed. These highways shall be considered to be annexed even though not included in the legal description set forth in the annexation ordinance.
The territory to be annexed to the sanitary district shall be considered to be contiguous to the sanitary district notwithstanding that the territory to be annexed is divided by, or that the territory to be annexed is separated from the sanitary district by, one or more railroad rights-of-way , public easements, or properties owned by a public utility, a forest preserve district, a public agency, or a not-for-profit corporation.
70 ILCS 2305/28