Skokie, IL Environmental Rules: Stormwater Management (2026)

Section 42-104, Other runoff control methods, applies where new construction, ground-level building additions, or other increases in impermeable surface exceed 400 square feet or 10 percent of the existing impermeable lot coverage in a zoning district, and where no open and improved public alley exists or the alley sits at an elevation that will not achieve positive drainage. In those situations the Village Manager or designee determines which of two systems the property must provide: a dry well system designed to collect and direct water to the front of the lot to drain to the street, engineered to work with the approved site plan under Sec.

42-102 and 42-103; or roof drainage discharged to the front of the lot to drain to the street. Subsection (b) offers a credit where an existing roof already discharges to the rear of a property without a drained alley: the new addition or impermeable-surface increase can get a 1-to-1 credit against the zoning district's impermeable coverage limit for each square foot of existing roof runoff redirected to the street. Subsection (c) extends the same gutter-to-street, dry-well, or drained-alley requirement to all new accessory structures with a floor area over 400 square feet.

Together with the engineering site plan requirements of Sec. 42-103, which require a Storm Water Pollution Prevention Plan for sites over one acre and drainage-course mapping to an approved discharge location, this article manages how runoff from new impervious surface reaches the public storm system rather than neighboring yards.