Berwyn, IL Environmental Rules: Stormwater Management (2026)

Section 1250.03 of the Berwyn Code of Ordinances states its purpose as reducing the volume and rate of stormwater runoff entering the storm sewer system and helping prevent flood damages. It applies to development meeting the § 1250.01(B) criteria: new developments needing site plan approval, planned developments, and new or expanded parking lots reaching 15 spaces. It does not replace controls required by any other agency. If another agency's stormwater rules also apply, both sets must be met, and where they conflict the more restrictive provision governs.

The design storm is the 50-year, 24-hour return frequency event. Detention is to be achieved through green infrastructure, post-construction stormwater management measures and BMPs designed to increase permeable areas and reduce pollution. The maximum allowable discharge rate is 0.15 cubic feet per second per acre, multiplied by the disturbed land area, and runoff from impervious surface cannot sheet flow to the public right-of-way.

A stormwater management plan under § 1250.01(E) must be prepared by a professional engineer registered in Illinois and approved by the Zoning Administrator. It shows sub-catchment areas, retention and detention BMP capacities, itemized drainage costs, an implementation timeline and an operations and maintenance schedule for each BMP. Site BMPs consist primarily of green infrastructure.

A property that cannot fit the controls on the lot can seek a fee-in-lieu. The Zoning, Planning, and Development Commission weighs whether approval will facilitate new development or redevelopment and whether lot size and configuration constrain the controls. Public Works calculates the fee for construction and ongoing maintenance, payments go into a dedicated stormwater management fund, and the certificate of waiver is recorded with the Cook County Recorder of Deeds at the owner's expense, with full payment made before a certificate of occupancy issues. Private facilities stay the owner's responsibility under a signed, notarized O&M plan and a recorded maintenance easement that gives the city inspection access.