Sangamon County, IL Environmental Rules: Stormwater Management (2026)

All subdivisions shall be developed with adequate surface drainage. Existing drainage ways and watercourses may not be altered and should become a part of the drainage plan. Surface water drainage improvements shall consist of storm sewers and/or open channels, inlets, catch basins and manholes designed and constructed to conform with standards established by the county engineer and shall adequately drain the area being developed including drainage from other areas which naturally drain through the area being developed. Storm water quality will also be considered when reviewing drainage plans. Reasonable provision shall be made for the collection and diversion of such surface waters into public areas or drains which the subdivider has a right to use. Such provisions shall be planned for in accordance with generally accepted engineering practices to reduce the likelihood of damage to other properties because of the construction of the subdivision. If, as the result of subdivision development, surface water is deposited in existing roadside ditches in quantities exceeding their capacity, the developer shall improve the ditches and replace culverts as needed to handle the flow. (Specific information for required basin analysis is to be obtained from the county engineer). Unless engineering evidence is presented to the County Engineer warranting exceptions, storm sewers shall be designed and constructed to meet the following criteria: