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1. Why is impervious area used to determine a property's stormwater utility fee?

The amount of impervious surface on a property is the single most important factor affecting the amount of water flowing off a property, how quickly that water flows off a property, and the amount of pollution picked up by the water from that property. Because of this, basing stormwater utility fees on the impervious area on a property is one of the most common methods used to determine stormwater utility fees in North Carolina. The City of Durham is one of more than 30 North Carolina municipalities that base their stormwater utility fees on the amount of impervious area on a property. For more information, please visit the North Carolina Stormwater Fees Page.

2. What is considered an impervious surface?

An impervious surface is a hard surface that does not let water soak into the ground or greatly reduces the amount of water that soaks into the ground. For more information, please visit our Impervious Surface Page.

3. What is not considered an impervious surface?

Areas covered with grass or that are planted (such as forests or gardens) are not counted as impervious surface. For billing purposes, wooden decks (without roofs) and the area of swimming pools that actually hold water are considered pervious. Please call 919-560-1258 for more information.

4. How is the amount of impervious area on my property calculated?

The amount of impervious area on your property is determined through the use of a geographic information system (GIS), aerial photos, and satellite imagery. Images are taken of Durham that show the impervious surfaces on each property. A computer program is then used to calculate the amount of impervious area on each parcel. To view impervious area on your property visit the Stormwater Utility Fee Map.

5. What if I disagree with the amount of impervious area listed on my bill?

You have the right to appeal your stormwater utility fee if you feel the calculation of impervious area for your property is incorrect. Learn more on the Appeals and Other Forms Page.

6. Why are there tiers for the residential stormwater utility fees?

Having several tiers allows the city to bill properties based on how much runoff they contribute to the storm drain system. This is fairer than charging all properties the same amount no matter how much (or how little) demand they place on the stormwater drainage system. Please call 919-560-1258 for more information.

7. What are the tiers?

There are 3 tiers for residential billing:
Tier 1
Residential properties with less than 2,000 square feet of impervious area are charged a yearly stormwater utility rate of $39.12.

Tier 2
Residential properties with impervious areas between 2,000 square feet and 4,000 square feet are charged a yearly stormwater utility rate of $81.

Tier 3
Residential properties with more than 4,000 square feet of impervious area are charged a yearly stormwater utility rate of $162.24. Please call 919-560-1258 for more information.

8. How are commercial or non-residential stormwater utility fees calculated?

A survey using statistical regression analysis determined that the average amount of impervious area on a residential lot within the City of Durham was 2,400 square feet. This value is used as an Equivalent Residential Unit (ERU) in determining the utility bill for non-residential properties. These properties are charged $6.75/month for each ERU. Properties that do not divide evenly into ERUs are rounded to the next lowest ERU if the remainder is less than 0.5 and rounded up if the remainder is 0.5 or greater. Please call 919-560-1258 for more information.