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Contact Information
3505 N. Dries Lane   •   309.494.8800

Impervious Area Map

Why is impervious area important?

Impervious surface areas like rooftops, sidewalks, walkways, patio areas, driveways, parking lots, sheds and more that don’t allow stormwater to do what it normally does — soak into the ground. To view the impervious surface area on your property, please click the button below.

Important: How to Read the Map

Search: Please use the upper left-hand box to type in your address.
Zoom: Use the zoom features on the side to zoom in or out of your property
Property boundaries: Property boundaries are shown with black lines. You are only responsible for the surfaces within your property boundaries (not the street or right-of-way).
Map legend: Click this icon to see a legend of the map Print: Click this icon to print a copy of your map Information: Click this icon to learn more about the map

Understanding Map Elements

The map is based on 2015 GIS (Geographic Information Systems) data collected by the County and verified in 2018 with our own fly overs.

click button for info
Click these buttons for more information about each area.
impervious area in red
Impervious areas: Impervious areas are shown in red.
parcel information
Parcel Information: Click within your “black-line” property boundaries and an info box will appear..

Ready to see your impervious area?

Understanding the Red Areas on Your Property

When we capture property information from aerial photography, we can’t always shoot pictures of buildings from directly overhead. Please note: the impervious area calculations for buildings are based on the roof area centered over the building foundation. Because the angle of the image varies for every property, this method is the industry standard and ensures the most accurate measurement of building areas.

  • Side of a building: The image may show a side of a building in red. Don’t worry — no one is charged for the side of the structure.
  • Part of roof is not in red: Since the calculations are based on the roof area centered over the building foundation, part of a roof may not be colored, but the measurement is still accurate.

Impervious surface area in the right-of-way: You may notice your driveway or sidewalk is outside of your property line. You are not charged for any surface outside of your property.

See something that shouldn’t be considered impervious? Please read about appeals below and contact us.

Surfaces considered to be impervious: roofs (of buildings including houses, sheds, garages and more), sidewalks, driveways, parking lots, paved areas, gravel, bricks, patios

Surfaces not considered to be impervious: yards, flower beds, gardens, lawn furniture.

Calculate Your Bill

The stormwater utility fee is based on the amount of impervious surface area on a property. Each billing unit will be set at $5 per 1,000 square feet of impervious area.

Read about credits and grants.


Notice an error? Get information about the appeals process.