Oak Park, IL Environmental Rules: Stormwater Management (2026)

Oak Park's stormwater management requirements apply to new construction, additions, and significant site improvements that increase impervious surface area. The village is within the Des Plaines River watershed and is served by a combined sewer system that handles both stormwater and sanitary sewage. During heavy rain events, the system can be overwhelmed, contributing to basement flooding. The Metropolitan Water Reclamation District of Greater Chicago (MWRD) Watershed Management Ordinance establishes regional stormwater standards that Oak Park enforces locally. Development projects that disturb more than 0.5 acres or increase impervious surface area significantly must submit a stormwater management plan demonstrating adequate detention or retention. Best management practices (BMPs) including rain gardens, permeable pavement, green roofs, and rain barrels are encouraged. The village has invested in sewer separation projects and green infrastructure to reduce flooding. Homeowners may be eligible for grants or rebates for installing rain barrels, downspout disconnection, and other residential BMPs through the MWRD's Green Infrastructure Program. Sump pump discharge must be directed to appropriate locations and not onto neighboring properties.