Impervious cover is any type of man-made or stone surface that doesn’t absorb rainfall.
Surfaces such as stone, rooftops, patios, driveways, sidewalks, roadways, parking lots, and some decks are considered impervious cover. Uncovered wooden decks and unpaved sections of driveways count as 50% impervious cover.
Impervious cover does not include sidewalks or easements in the public right-of-way, water features such as ponds, fountains, and water detention basins, porous pavement, or access ramps.
Dependent on zoning designation, a certain percentage of impervious cover is permitted on a property. A reviewer can help you calculate your impervious cover, but if you would like to do it yourself, download this spreadsheet.
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