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

2 and related statutes, sets the county-wide floodplain and stormwater framework for unincorporated territory and any municipality that has not adopted its own equally strict ordinance. Sec. 16-79's general requirements apply to every development: a site must be kept reasonably safe from flooding, and a project cannot impose new flood-protection costs on anyone other than the developer, nor increase flood elevations or reduce flood-conveyance capacity upstream or downstream of land the developer controls, though removing obstructions like undersized culverts is allowed. For residential and nonresidential subdivisions, stormwater facilities have to be functional before the county issues a building permit; single-parcel developments must have them functional where practicable before construction even begins.

The section also sets an overland-flow-path standard: if the upstream drainage area is at least twenty acres, the site needs an overland path sized for the base flood, and buildings hydraulically connected to a stormwater basin or overland flow path must be elevated or floodproofed one to two feet above the design flood elevation depending on the tributary area. The County Zoning Administrator, named Administrator of this division under Sec. 16-22, reviews and enforces these standards alongside the more detailed site-runoff-storage and sediment-control requirements later in the same article.