Evanston, IL Environmental Rules: Stormwater Management (2026)
Key Facts
- Mandatory trigger
- 5,000+ sq ft footprint & full value
- Residential exemption
- 1-3 family homes on ≤1 acre
- Fine
- $250 after 30 days, then per day
- Fee in lieu
- $12/cubic ft, capped at 5%
Summary
Evanston requires on-site storm water detention and release-rate control for all new developments, mandatory once a project's footprint tops 5,000 square feet and construction costs exceed the parcel's full assessed value.
All new developments shall provide storm water control for the entire property. Additionally, any development: a) where the final building footprint is greater than five thousand (5,000) square feet, and b) having construction costs greater than one hundred percent (100%) of the latest property value as published by the Cook County assessor's office for the existing tax parcel(s) affected by the development... shall provide storm water control for the entire property.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 21).
Full Breakdown
Every new development in Evanston must provide storm water control for its entire property. Control becomes mandatory once the finished building footprint exceeds 5,000 square feet and construction costs exceed 100% of the Cook County Assessor's valuation for the parcel: a threshold that also applies cumulatively across staged or phased developments (§ 4-20-4-1). Control means both detaining a set storm water volume and limiting the rate storm water discharges into the City sewer system. One-, two-, or three-family homes on parcels no larger than one acre are exempt, as are resurfaced parking lots that don't change drainage (§ 4-20-4-2).
Violations & Fines
Noncompliant storm water systems draw a written notice; failure to fix it within 30 days brings a $250 fine, then $250 for each additional day of noncompliance (§ 4-20-10).
Frequently Asked Questions
Does every new building in Evanston need storm water detention?
Are single-family homes exempt from Evanston's storm water rules?
Sources & Official References
Other rules in Evanston
Compare Evanston to another location·View the Illinois environmental rules overview
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Stormwater Management in Nearby Cities
How other cities in Cook County handle stormwater management.