The Winnebago County stormwater management ordinance applies to unincorporated areas of Winnebago County, Illinois.

Stormwater runoff occurs when precipitation from rain or snowmelt flows over the land surface. Stormwater can soak into the soil (infiltrate), be held on the surface and evaporate, or runoff and end up in nearby streams, rivers, or other water bodies (surface water). The addition of roads, driveways, parking lots, rooftops and other surfaces that prevent water from soaking into the ground to our landscape greatly increases the runoff volume created during storms. In natural landscapes such as forests, the soil absorbs much of the stormwater and plants help hold stormwater close to where it falls. In developed environments, unmanaged stormwater can create two major issues: one related to the volume and timing of runoff water (flooding) and the other related to potential contaminants that the water is carrying (water pollution).

Municipalities located in urban areas as defined by the Census Bureau are required to obtain NPDES permit coverage for discharges from their municipal separate storm sewer systems (MS4s). Municipalities located outside of urbanized areas may need to comply within 180 days notice or as determined by the NPDES Permitting Authority.

• Gereral NPDES Permit No. ILR40
• Winnebago County Notice of Intent
• 2021 Winnebago County Annual Facility Inspection Report
• 2020 Winnebago County Annual Facility Inspection Report
• 2019 Winnebago County Annual Facility Inspection Report
• 2018 Winnebago County Annual Facility Inspection Report
• 2017 Winnebago County Annual Facility Inspection Report

Beginning on March 10, 2003, construction sites that disturb one acre or more are required to have coverage under the NPDES general permit for stormwater discharges from construction site activities.

Municipalities under 100,000 population will no longer be exempt from the construction site stormwater requirements and the industrial stormwater requirements effective March 10, 2003. (WWTPs 1.0 mgd or more will need a General Stormwater Permit for Industrial Activities) Definition of industrial stormwater has been revised to expand the "no-exposure" exemption to all industrial categories except construction. NEW Electronic Submission of Notice of Intent is now available for Construction Sites and Industrial Activities.

Winnebago County encourages environmentally responsible practices.

Below are a few suggestions for help minimize the negative impacts of stormwater runoff. 

• Bioinfiltration Cells
• Bioswale
• Permeable Pavement
• Rain Barrels
• Rain Gardens
• Storm Sewers
• Stormwater Trees
• Vegetative Swales

For more information about stormwater and what you can do to reduce pollution, we invite you to learn more from the expertise of our partners at Winnebago County Soil & Water Conservation District.

Download our information guide, After the Storm - A Citizen's Guide to Understanding Stormwater.

For questions regarding the Winnebago County Stormwater Management Ordinance, please contact the Highway Department at (815) 319-4000 or This email address is being protected from spambots. You need JavaScript enabled to view it..