No matter the size of the city, problems arise from uncontrolled storm water runoff. Development and inadequate drainage systems increasingly compound problems associated with moderate to significant rainfall. Storm water runoff from these rainfall events accumulate in many areas of our city, causing nuisance flooding and possible threats to public health and safety.

In addition to drainage issues, the rain that falls on our streets, houses, driveways, parking lots, buildings and other impervious surfaces run off and carry pollutants such as oil, gasoline, pet waste and heavy metals. Storm water runoff from lawns and other green spaces can carry pesticides, herbicides and fertilizers. Over time, these pollutants accumulate in the waterways causing significant damage to our creeks, streams and lakes.

The EPA now considers pollution from all different sources, including urban storm water pollution, to be the most important source of contamination in the nation’s waters. Uncontrolled urban runoff also contributes to hydrologic and habitat modification, two important sources of river impairment identified by the EPA.

 National Pollutant Discharge Elimination Systems Phase II

On October 29, 1999, the EPA issued new storm water regulations that require communities with populations under 100,000 to control water pollution caused by storm water runoff. Known as the EPA Phase II storm water rule, these regulations require cities such as McMinnville to implement a storm water management program that will reduce pollution associated with storm water runoff to the maximum extent practicable.

The City of McMinnville is required to meet and enforce the regulations of the NPDES Phase II permit program as authorized by the Clean Water Act. The NPDES permit program controls waste pollution by regulating point sources that discharge pollutants into waters of the United States. Water pollution degrades surface waters making them unsafe for drinking, fishing, swimming, and other activities.

Under the NPDES Phase II program, the Storm Water Management Department is responsible for overseeing the proper maintenance, construction and inspection of storm drainage systems within the city limits. Land development directly affects watershed functions. When development occurs in previously undeveloped areas, the resulting alterations to the land can dramatically change how water is transported and stored. Residential and commercial development create impervious surfaces and compact soils that filter less water, which increases surface runoff and decreases groundwater infiltration. These changes can increase the volume and velocity of runoff, the frequency and severity of flooding and peak storm flow.


What is stormwater runoff?

Stormwater runoff is the water that flows off roofs, driveways, parking lots, streets, and other hard surfaces during rainstorms. Rather than being absorbed into the ground, it pours into ditches, culverts, catch basins, and storm sewers. It does not receive any treatment before eventually entering the community’s streams and lakes.

What problems does it cause?

Stormwater can carry harmful nonpoint source pollutants, cause flooding, erode topsoil and stream banks, and destroy marine life habitats. In an area with natural ground cover, only 10% of rainwater becomes runoff. The rest is absorbed or evaporates. In urban areas, up to 55% of rainfall can become stormwater runoff.

Why are the stormwater and sewer systems separate?

Unlike wastewater, which is treated before it is released back into the environment, stormwater goes directly into a community’s ponds, streams, and lakes. Because stormwater comes in large amounts at unpredictable times, treating it as wastewater would be very expensive.

What is nonpoint source pollution?

Nonpoint source pollution is water pollution that is difficult to trace to a specific discharge point. Because it comes from many diverse sources, it is hard to control. Examples of common nonpoint source pollutants include fertilizers, pesticides, sediments, oils, salts, trace metals, and litter. They come from farms, yards, roofs, construction sites, automobiles, and streets.

What is impervious surface area?

Any surface that does not readily absorb water and impedes the natural infiltration of water into the soil. Common examples include roofs, driveways, parking areas, sidewalks, patios, decks, tennis courts, concrete or asphalt streets, crushed stone, and gravel surfaces.

How does the city determine impervious surface area?

For single-family homes, a statistical sampling is taken using Geographical Information System (GIS) including aerial survey data. Each is measured and an average impervious surface area is determined. For businesses and other institutions, the city measures the impervious area using aerial survey data.

What can I do to reduce pollution in stormwater runoff?

Creating natural areas on your property can help reduce the quantity of stormwater runoff. Disposing of wastes properly, using the minimum amount of chemicals on your yard, and keeping your car well-maintained can reduce the amount of pollution that you add to stormwater runoff.


  • Report any non-emergency type pollution problem to your local government offices. For emergency pollution problems, such as major spills, call 911.
  • Never dump anything down a storm drain inlet. They flow directly to our lakes and streams.
  • Keep your leaves and grass clippings out of the streets so that they do not end up washing into the storm drain inlets.
  • Wash your vehicles on your lawn or at a car wash facility instead of in your driveway.
  • Keep your automobiles and your gas-powered lawnmowers or blowers well-tuned so that they are not dripping toxic fluids or emitting toxic fumes.
  • Do not use chemicals on your lawn before it is expected to rain, and try using organic or slow-release products, which are better for your lawn and for the environment.
  • Be conservative with pesticides and herbicides (weed killers) and try natural alternatives. Call your local Extension Service to find out more about natural pesticides.
  • Make sure your air conditioners are in good working order and not leaking harmful chemicals.
  • Install early closing toilet flappers and water-conserving showerheads.
  • Lawns need less than an inch of water per week. If it rains an inch, do not water. Try using a rain gauge.


CALL: 931-473-1204

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·         City of McMinnville Storm Water Ordinance

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·         Oakland Branch VSA

·         Coming in March 2020

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·         Storm Water & Erosion Control Training & Manuals
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·         Landscaping Best Management Practices
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 City of McMinnville
Community Development Department
101 East Main St./P.O. Box 7088
McMinnville, TN 37111