Water Quality Challenges in Stormwater Ponds
Stormwater ponds are designed to receive runoff from the surrounding development in part to manage the pollutants that may be contained in that runoff. Fertilizing lawns, pet waste, washing cars, painting, pressure washing, construction, automotive maintenance, pesticides, feeding wildlife, and many other homeowner activities contribute to runoff pollution, so there is tremendous potential for pollutants to enter stormwater ponds. In commercial watersheds, other sources of pollution are present, such as unprotected grease bins at restaurants, leaking dumpsters that are not covered, automotive fluids at maintenance shops, and so forth. Considering all of these potential pollution sources, it is difficult to determine what is or is not in stormwater pond water or the sediments in the bottom of the pond, but it is very likely that all stormwater ponds contain at least some pollution.
Are there any signs that indicate that a pond is polluted?
Nutrients from fertilizers and animal wastes produce the visual cues that are easiest to recognize. They grow algae. This growth may be evident through changes in water color such as cloudy, pea soup water or as floating mats of filamentous algae. (See section on Aquatic Weed Control) Rainwater is naturally low in nutrients. It is only when rain water picks up nutrients from roads and lawns that it builds-up enough nutrients to grow large blooms or mats of algae; therefore, stormwater ponds develop algae growth mainly in response to the fertilizers and wastes that residents are depositing on lawns and paved surfaces. Considering that animal waste is not only a source of nutrients but also a source of pathogens and bacteria, it can be assumed that ponds that have significant algae growth are likely to have high levels of fecal bacteria and other disease causing organisms.
A fish kill also is a striking indicator of poor water quality, but the actual cause of a fish kill may be difficult to determine. Fish kills in stormwater ponds usually result from low oxygen events (largely associated with algae blooms or turnovers), but they also may be caused by pesticides, toxins, parasites, or natural causes. (See section on Fish Kill & Fish Health)
Another visual indicator of poor water quality is the formation of suds or films on the water surface or plumes of odd colored water. Oils and other insoluble compounds usually rise and form skims or sheens on the water surface. Plumes of colored water may be a result of painting or pressure washing activity. Suds or soapy water may indicate the discharge of detergents into the drainage system. Evidence of this sort indicates that an illicit material has been discharged into a storm drain or directly into the pond. (See section on Muddy Water, Surface Films, Foam, and Slime)
What can we do if we see an illicit discharge into our pond or storm drains?
Most of the municipalities and counties in South Carolina are required to respond to reports of illicit discharges. Many have established a hotline for such calls. If you see substances being dumped into your storm drains or ponds, you can report that activity to your local public works or stormwater department. Also, the SC Department of Health and Environmental Control will respond to such reports. This is usually handled through the SC DHEC Environmental Quality Control offices. Homeowners associations also can develop their own bylaws that penalize residents who discharge illicit materials into ponds or storm drains.
What can we do about non-point pollutants that are not discharged directly into drains or ponds?
Non-point pollution is the collection of pollutants that are deposited on the land in the community and are not the result of a direct discharge into a drain or pond. This includes fertilizers from lawns, pet waste, residual pesticides, yard debris, etc. These pollution sources are best minimized by educating the community about the effects of stormwater pollution. Teaching neighbors that washing the car in the driveway is the same as pouring soap suds in the pond, and failing to sweep fertilizer granules off the road after application is the same as throwing handfuls directly into the pond is the only way to prevent these pollutants from entering the storm drainage system. Signage around ponds, community websites and newsletters, assemblies and meetings, and other media outlets are good ways to inform residents about stormwater pollution. For articles and tools to help inform residents about non-point pollution, visit Clemson's Carolina Clear Program website.