605 ILCS 5/9-101.1
Whenever the proper highway authority is about to construct or improve the drainage structures of a State highway, county highways, or county unit district road, the highway authority shall meet and consult with the authorities of any municipality adjacent to or through which such highway or road runs. The purpose of such meetings is to work out an agreement with such municipality and all other interested agencies and units of local government as to the extent of such drainage construction or improvement.
If a county or State highway, in a county of under 1,000,000 population, adjoins a parcel of land proposed to be subdivided, the subdivider of the parcel shall notify the proper highway authority in writing of the proposed subdivision and provide the proper local authority that would approve the subdivision a copy of the notice. The notice shall request of the proper highway authority its need to have provided, at the cost of the highway authority or as otherwise provided by law, additional capacity in any stormwater detention facility to be constructed in the subdivision for the future availability of the highway authority for meeting the stormwater detention requirements of any future public construction on the highway. The highway authority shall within 30 days of receipt of the written notice provide written information to the proper local authority relative to the request. The parties may then work out by agreement the extent of the inclusion of those stormwater detention needs, if any, in the subdivision. The proper highway authority may provide to the subdivider any funds generally available for highway construction to provide for the highway authority's proportionate share of the design of the stormwater detention and the proportionate share of the cost of the property required for the stormwater detention including the impact of density changes on said parcel as the parties may agree within 60 days of the reply to the notice issued by the highway authority. In the event that the parties are not able to reach agreement within the 60 days the parcel may be subdivided as may be approved by the proper local authority without the inclusion of said stormwater detention needs identified by the highway authority.
605 ILCS 5/9-101.1