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FAQs: Stormwater Runoff

What is stormwater runoff?

Why is stormwater runoff a problem?

What is impervious surface?

What are the effects of nonpoint source pollution?

What are the problems with stormwater runoff in Fairfax County?

What are the state and federal regulations Fairfax County must follow with regard to stormwater?

What can you do to reduce pollution that is getting into our waterways?

How can you help improve water quality?

Where can you find more information about stormwater management in Fairfax County?


What is stormwater runoff?
Stormwater runoff is the water from rain or snow melt that travels over roadways, driveways, roofs, parking lots and other impervious surfaces. Instead of being absorbed into the ground, stormwater runoff in Northern Virginia travels over these surfaces to storm drains, open channels, and ditches until it reaches streams, the Potomac River and ultimately water bodies such as the Chesapeake Bay or Atlantic Ocean.
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Why is stormwater runoff a problem?
Too much stormwater runoff can cause flooding and erosion and can carry harmful pollutants such as pesticides, fertilizer, litter, car oil, and pet waste to storm drains or directly to more than 980 miles of streams in Fairfax County. Streams in the county drain to the Occoquan Reservoir and Potomac River, which are the sources of drinking water for over a million Northern Virginia residents. Anything that enters a storm drain is discharged untreated into water bodies we use for swimming, fishing, and providing drinking water.
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What is impervious surface?
Impervious surface is any surface that does not allow water to be absorbed into the ground. In Fairfax County, there are many examples of impervious surfaces such as roofs of buildings, homes and sheds, roadways, parking lots, sidewalks, and driveways. The county is made up of approximately 17 percent impervious surface.
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What are the effects of nonpoint source pollution?
Nonpoint source pollution is water pollution that is difficult to trace to a specific discharge point. Such pollution comes from many sources such as yards, roofs, construction sites, automobiles, streets, homes and businesses, so it is very hard to control. Stormwater runoff often contains nonpoint source pollutants that flow to our streams, rivers and bays, adversely affecting water quality, plants, fish, animals, and people. Here are a few examples of nonpoint source pollutants and their effects:

  • Sediment is soil particles from stream banks and construction sites that are dislodged by stormwater runoff and deposited into streams, lakes, and rivers. Sediment accumulates in water bodies and destroys feeding grounds for aquatic life, clogs fish gills, blocks light, and increases water temperature.
  • Nutrients and Organic Debris include phosphorous, nitrogen, and potassium and are found in fertilizer, leaves, grass clippings, sewage, detergents, and animal wastes. These elements are not harmful to the environment in low doses, but excess nutrients in an already healthy environment can be dangerous. Decaying organic matter depletes oxygen needed by aquatic life, leaving fish and shellfish to suffocate. Excess nutrients have been the focus of degradation in the Chesapeake Bay for decades.
  • Trash is considered garbage, construction debris, and animal waste. It becomes part of stormwater runoff, entering storm drains and local waterways and clogging the system.
  • Toxins are chemicals that can cause human and wildlife health problems. They include organic chemicals and metals, pesticides, herbicides, household chemicals, paint, paint cleaners, gasoline, motor oil, battery acid, antifreeze, and roadway salt.
  • Pathogens are a specific causative agent of disease. The presence of bacteria in water, which normally are found in the intestinal tracts of humans and animals, signals that pathogens may be present. This is indicated or measured by fecal coliform or E. coli.

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What are the problems with stormwater runoff in Fairfax County?
As the amount of impervious surface increases, the volume of stormwater runoff increases, resulting in erosion, flooding, and a swell in the flow of harmful pollutants through storm drains and to streams. Fairfax County is made up of approximately 17 percent impervious surface. According to the recent Fairfax County Stream Protection Strategy Baseline Study, 70 percent of the streams in the county are in fair to very poor condition.

There are more than 1,400 miles of storm drainage pipes in the county that convey stormwater runoff from roofs, roadways, parking lots, sidewalks, driveways, and lawns, to our network of more than 980 miles streams. More than 3,000 stormwater facilities provide water quality and/or quantity control for stormwater runoff in the county. All facilities require periodic maintenance and need to be replaced when they fail. Fairfax County's pipes and facilities are aging, and limited resources are available to fix and/or replace them.
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What are the state and federal regulations Fairfax County must follow with regard to stormwater?
Fairfax County is responsible for compliance with new federal and state regulations regarding water quality and providing stormwater management facilities, pipes and other structures and services within its jurisdiction. Permits require maintenance of storm drains, inlets, ditches, and streams, and ensure that erosion and sediment controls are provided on construction sites. All of these requirements are rooted in the Clean Water Act, which sometimes mandates actions to protect personal and public property as well as provide for a healthy environment. Neither the federal nor the state government provides funding for these services.
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What can you do to reduce pollution that is getting into our waterways?
Adapted from the Northern Virginia Soil and Water Conservation District:

  • Limit use of pesticides and fertilizer, and when you do use them be sure it is at appropriate times of the year and in recommended amounts. Introduce natural predators to your garden, and use pest resistant plants. Remove eggs, larvae, cocoons, and adults from plants by hand.
  • Prevent property erosion by covering bare soil with vegetation and mulch.
  • Remove obstructions from stream channels and replant stream banks.
  • Don't mow all the way to the edge of a lake or pond. Leave a buffer of tall grasses or shrubs to filter pollutants.
  • Landscape yards to minimize stormwater runoff.
  • Preserve neighborhood trees that help minimize the damage caused by surface runoff.
  • Place retaining walls or diversions on steeply sloping ground to reduce the rate of water flow and erosion.
  • Make sure septic tanks work properly.
  • Dispose of litter in garbage cans or in recycling bins. Recycle glass, aluminum, plastic, paper, motor oil, and newspapers.
  • Compost yard and garden waste.
  • Pick up pet waste and bag it with regular household trash or flush it in the toilet.
  • Never intentionally dump anything into a storm drain.

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How can you help improve water quality?
The success of any stormwater management program greatly depends on the involvement of residents.

Learn more about stormwater runoff, nonpoint source pollution, and the things you can do in your home, neighborhood, and community that will improve the water quality of streams.

Get involved in your local watershed planning effort.

Volunteer for stream monitoring, storm drain stenciling, stream cleanups, and join or form a "Friends of" watershed group.
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Where can you find more information about stormwater management in Fairfax County?
To find out more about stormwater management in Fairfax County, visit the stormwater web page , call the Stormwater Planning Division at 703-324-5500, TTY 711, or send us an e-mail.
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