Impervious surface refers to all hard surfaces on your property that prevent rainwater from naturally soaking into the ground. Instead, rainwater accumulates in larger amounts and flows more rapidly into the storm sewer system and eventually into our streams and lakes. If left unchecked, the increase in impervious area can create water quality, flooding, or drainage issues. The runoff also picks up pollutants such as oil, pesticides, fertilizer, sediment, and nutrients along the way before entering the storm sewer system.

Examples of Impervious Surfaces:           

• Rooftops
• Patios
• Swimming pools
• Driveways
• Sidewalks and walkways
• Sport courts
• Concrete or asphalt

City Code Requirements

To protect our water bodies, City Code has regulations that limit the amount of impervious surface area on a lot to no more than 35% of the total area of a residential lot. If your property is within 1,000 feet of a lake or 300 feet of a river or creek, it is considered shoreland per the Minnesota DNR. For properties in shoreland areas, the impervious surface area cannot exceed 25% of the lot area.

How do I calculate the impervious surface on my lot?

To get an estimate of your impervious surface, you can do one of the following:

• Check if you have a certificate of survey of your property from when your home was constructed or if a survey was completed due to a recent project. Newer lot surveys typically include the original impervious surface calculations. 
• Hire a licensed land surveyor to complete an updated lot survey.
• Complete manual calculations using the Impervious Surface Worksheet.
• Measure and calculate approximate impervious areas using the measure tool on Scott County's interactive mapping application. Please refer to the Scott GIS3 Tutorial Manual for instructions on how to use the mapping application or watch the videos on how to Select A Parcel and How to Measure Distance and Area. 

How can I reduce my impervious surface area for my proposed project?

• Remove existing impervious surface area no longer needed (i.e. remove excess patio or pool deck area)
• Swap impervious surface on the property of the same size (i.e. remove old shed to add new patio)

In some circumstances, a homeowner can request a conditional use permit (CUP) to exceed the 35% maximum, which requires final approval from the City Council. The application requires a plan that addresses the increase in runoff resulting from the project. The process also requires a hearing to gain input from the public on the project. Please call the Planning Department at 952-882-2650 to find out if a conditional use permit is an option for your proposed project.