In a natural, undeveloped environment, rainfall from storms falls on the ground and evaporates or is absorbed into the soil. The water that is absorbed is "cleaned" as it moves through plant material and the soil layers. This water replenishes the groundwater and provides baseflow for streams.
In an urban, developed environment, like Philadelphia, rainfall from storms falls on the ground and runs off from impervious surfaces (e.g., concrete, asphalt, buildings, etc.) and flows into the sewer system. This water is what is referred to as stormwater runoff or stormwater or runoff. Since this water can't be absorbed into the ground and take part of the natural water cycle, it needs to be managed. Stormdrains on the street and other surfaces allow the stormwater into the sewer system that PWD builds and maintains.
In an urban, developed environment, like Philadelphia, rainfall from storms falls on the ground and runs off from impervious surfaces (e.g., concrete, asphalt, buildings, etc.) and flows into the sewer system. This water is what is referred to as stormwater runoff or stormwater or runoff. Since this water can't be absorbed into the ground and take part of the natural water cycle, it needs to be managed. Stormdrains on the street and other surfaces allow the stormwater into the sewer system that PWD builds and maintains.
PWD will now relate a property's burden on the sewer system directly to its stormwater charge by using the property's individual characteristics as the basis for this fee. We do this by using Geographic Information Systems technology, or high-tech mapping software, to measure a property's gross area and impervious area. Impervious area is classified as any surface that prevents water from soaking into the ground. Once we know a property's gross and impervious area, we use this formula to calculate the stormwater charge:
Stormwater Charge = (Gross Area Rate * Gross Area of Property) +
(Impervious Area Rate * Impervious Area of Property)
Stormwater Charge = (Gross Area Rate * Gross Area of Property) +
(Impervious Area Rate * Impervious Area of Property)
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