Oak Park, IL Environmental Rules: Grading & Drainage (2026)

The Village of Oak Park regulates grading and drainage to prevent water damage to neighboring properties and to manage stormwater within the combined sewer system. Any construction project that alters the grade or drainage pattern of a property must include a grading and drainage plan as part of the building permit application. The plan must show existing and proposed grades, drainage flow directions, and methods for managing runoff. The fundamental requirement is that property owners may not alter drainage patterns in a way that increases stormwater flow onto adjacent properties. This is consistent with Illinois common law regarding surface water drainage. New impervious surfaces (driveways, patios, additions) must account for increased runoff through on-site detention, infiltration, or other approved methods. The MWRD Watershed Management Ordinance sets regional standards for detention requirements based on the amount of new impervious surface created. Downspouts should discharge onto the owner's property and not be directly connected to the sanitary sewer. The village may require a grading permit for significant earthwork even when no building permit is needed. Retaining walls over 4 feet in height require engineering design and a building permit.