What is impervious? How much in Superior is impervious?

About 21% of the City of Superior is impervious.  On these types of materials water does not infiltrate into the ground.  Instead, it runsoff.  Whenever there is runoff there is the possibility of pollutants traveling along with the water.  Pollutants ranging from natural things like soil, leaves, small branches to chemicals and materials like oil and spills. 

From the pie graph below you can see that of the impervious areas most of it is due to roads (21%).  Buildings comprise about 16% of the areas. 
Other categories with 5% or over are: unpaved driveways (16%), paved parking areas (9%), railroad yard (7%), unpaved roads (5%), paved driveways (5%), and parking unpaved (5%).  Unpaved areas are considered impervious because of compaction of the soil.  Other areas considered impervious are pools, tanks, trails, alleys, sidewalks, decks, concrete, and holding ponds.