In a natural landscape, the water from rainfall or snowmelt will soak into the soil, be absorbed by trees and other plants, evaporate into the air, or travel over land to receiving streams, lakes, rivers or wetlands. In developed areas where driveways, buildings and roads cover the soil, water cannot be absorbed and instead travels over these paved surfaces as runoff, reaching our waterways much more quickly. As it flows over these surfaces, the runoff also collects various pollutants (dirt, fertilizer containing phosphorus and nitrogen) and debris (grass-clippings, paper, cigarette butts).
Stormwater Management Ponds (SWMPs) are facilities designed to collect runoff from the local storm sewer system following either a rainfall or snowmelt event, or activities such as watering lawns and washing cars. SWMPs are built to temporarily hold this water, provide treatment to remove the pollutants, and then slowly release it back into our waterways.
SWMPs control the flow of water. Without these ponds, large amounts of water would enter a stream all at once, causing flooding and eroding soil from the stream banks. SWMPs have at least one inlet that allows water to flow from the storm sewer system into the pond. The pond's outlet conveys water from the pond into a nearby creek system at a controlled rate.
SWMPs also improve water quality. The permanent pool of water within the pond allows sediment to settle before water enters the stream. In addition, the buffer areas around the SWMP are usually landscaped with dense natural vegetation. This vegetation also improves the water quality by helping to filter the sediment.
The town carries out the maintenance once the pond has been assumed through the development process. Routine maintenance includes removal of debris in and around the pond; removal of invasive vegetation; maintenance of structures (eg. gates, locks, valves, etc.), and maintenance of surrounding vegetation and plants. The vegetation planted around the pond is dense and appropriate for the area. Aggressive weed control operations, including the use of pesticides, are not required. Grass cutting is not recommended for the ponds in order to maintain a natural environment. The town carries out maintenance of these ponds, including vegetation replacement.
Non-routine maintenance includes bank stabilization, structure repairs and removal of excess sediment. Once every five to 10 years the SWMP is cleaned to remove accumulated sediment to ensure the pond continues to function as intended. The SWMP is drained to facilitate the clean-out, and soil sampling and testing is carried out to ensure the sediment removed is disposed of safely.
SWMPs were not designed or intended for recreational use. For the health and safety of the public several activities are prohibited, including but not limited to: swimming or wading, skating, boating, and fishing. Safety/warning signs have been placed at each of our facilities to inform the public of prohibited activities. These signs also indicate the potential for rapid water level fluctuations in the pond. For the protection of the SWMP, several activities are prohibited to control the intrusion of wildlife and foreign matter, including fish stocking, unauthorized vegetation planting/removal, and material dumping. The signs include both printed words and international symbols for prohibited activities. Should you visit our ponds with younger family members or friends, please take a moment to review the warning signs and impress the importance of safety to our younger citizens and visitors.
SWMPs are not typically considered good mosquito breeding sites since the water level is continuously changing and exposure to wind is high. However, the presence of vegetation and debris can create standing pockets of water that may serve as mosquito breeding sites. Preventative measures include a maintenance program that involves debris removal and control of vegetation. Visit the West Nile Virus page for details
For more information, download our Stormwater Management Ponds flyer (pdf) and our Be Wise Around Water card (pdf).