Is stormwater runoff the #1 water polluter in the United States?

Synithia Williams

Synithia Williams

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Synithia R. Williams, Lexington County South Carolina


When most people think of water pollution, they immediately think of industries and sanitary sewer overflows. What they may not realize is that the Environmental Protection Agency (EPA) considers stormwater runoff pollution as the number one source of water pollution in the United States.

Forty percent of the waters in Lexington County are impaired due to runoff pollution. When stormwater hits rooftops, driveways, parking lots and roads, it picks up pollutants such as oils, bacteria, and sediment before entering the storm drainage system.  Storm drains don't end at a wastewater treatment plant, but dump directly into creeks, rivers and streams; taking any pollutants in runoff with it.

Runoff pollution is such a big problem, that EPA began regulating it in the 1990s through the National Pollutant Discharge Elimination System (NPDES) program. NPDES was originally developed in the 1970s to control pollution from wastewater treatment plants and industries, but later was tailored to cover discharges from storm drains and construction sites. Local governments in urbanized areas are required to obtain an NPDES Municipal Separate Storm Sewer Systems (MS4) Permit for storm drainage discharges. Lexington County received its MS4 Permit in the fall of 2007, and subsequently updated its stormwater management ordinance and land development manual to reflect permit requirements.  

There are six minimum control measures in the MS4 Permit: public education and involvement, illicit discharge elimination and detection, construction and post construction runoff control and good housekeeping. All of these areas were addressed in the stormwater management ordinance, but the land development manual, which is an extension of the ordinance, is focused on the construction and post construction elements. Erosion from construction sites occurs at a higher acceleration than erosion from agricultural lands and forests. Other pollutants can attach to sediment and be transported to waterways. As land is developed, there is an increase in hard surfaces, stormwater runoff and pollutants, thus increasing the need for post construction runoff control.

Lexington County staff worked with a stakeholders group made up of developers, engineers, contractors and environmental organizations, to ensure the concerns of those affected was taken into consideration as the County worked to meet the federal and state mandates. The major requirements in the ordinance are listed below:

•    Improved sediment and erosion control requirements on construction sites.
•    Controls to lessen the impact of increased runoff velocities to downstream property owners.
•    Best management practices (BMPs) are required to reduce pollutants in runoff both during and after construction on specific sites.
•    Areas draining to impaired waterways and Lake Murray were designated as Special Protection Areas.
•    Buffers are required along streams to help filter pollutants in runoff, stabilize stream banks and mitigate flood hazards.

The County's stormwater management regulations have been recognized by the South Carolina Wildlife Federation and the National Association of Counties, but the work to protect waterways in Lexington County isn't over. The South Carolina Department of Health and Environmental Control (SC DHEC) is currently revising NPDES permits for MS4s and construction sites. The new permits will include requirements that have never been regulated in South Carolina. Effluent standards, which set a numerical limit on the sediment in discharges from construction sites, are being modified by the EPA, and will eventually be included into the NPDES MS4 and construction permits. There will also be a greater emphasis on Total Maximum Daily Loads (TMDLs), which set the daily amount of a pollutant that a water body can receive and still meet water quality standards. Both changes will transform the way sites are developed in South Carolina, but the extent of those changes has yet to be seen. 

Become a solution to runoff pollution:

  1. Consider low impact development practices (LID) on new and redeveloped sites. LID mimics pre-development hydrology conditions through infiltration and minimization of impervious areas.
  2. Reduce runoff from your property by installing rain barrels and directing down spouts and sprinklers to landscaped areas, not hard surfaces.
  3. Landscape smart by performing a soils test to determine fertilizing needs for plants and following directions on pesticides and fertilizers to prevent over use.
  4. Install pet waste pick up stations, sweep up spills instead of hosing them down the storm drain and remove trash and debris from gutters.


Synithia R. Williams has been the Environmental Coordinator for Lexington County, SC since April 2006.  Synithia's responsibilities include developing policies and programs aimed towards compliance with national ambient air quality standards and the requirements of the County's Phase II NPDES MS4 Stormwater Permit.  Synithia received her Bachelor of Science in Biology from the University of South Carolina and a Masters in Public Administration from Strayer University both in Columbia, SC.  Synithia is a Certified Erosion Prevention and Sediment Control Inspector and Certified Stormwater Plan Reviewer and is the SCDHEC 2008 Spare the Air Outstanding Individual.  When she isn't working, Synithia enjoys writing, and spending time with her husband Eric and two young boys, Eric Jr. and Samuel.

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