Stormwater Management Ponds

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.

Current projects

Bayshire Pond cleanout and retrofit

The town has recently completed maintanance works at  Bayshire stormwater management pond (town pond number 15) located at 1511 Bayshire Drive. This works included the removal of accumulated dirt, sand and debris (sediment), remomal of failing stone walls, and improvements to the pond's inlet and outlet structure.

While the majority of the restoration work from the construction activities is finished, including trail reconstruction and tree and shrub planting, additional work will be required in spring 2020 to further restore the site with seed to establish native grasses and wildflowers to all disturbed areas.

In the meantime, it is anticipated that minor erosion from rain and snow melt may occur along the side slopes of the pond during the winter.  Minor touch-up of the pond slopes will occur prior to seeding in spring 2020, as required.

For more information contact:

Project Manager
Diana Friesen, Town of Oakville
905-845-6601, ext. 3904

Why do we need Stormwater Management Ponds?

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).

How do SWMPs help?

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.

Who maintains SWMPs?

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.

Safety issues

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.

What about the presence of West Nile Virus at SWMPs?

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

What can you do to help the function of a SWMP?

  • Dispose of trash properly to avoid accumulation in and around the pond
  • Dispose of grass clippings or leaves properly to avoid accumulation in and around the pond
  • Minimize the use of fertilizer
  • Avoid disturbing vegetated areas around the pond to minimize sediment-laden runoff from entering the pond
  • Avoid introducing swimming pool discharges or allowing toxic substances (oil, anti freeze) to run off into the pond or into storm sewers that lead to the pond
  • Report evidence of beaver activity (damming) or other animal activity to the town so that proper maintenance activities can be carried out
  • Do not plant any trees within the park area that contains the SWMP without prior approval from the town
  • Obey all signs posted around the ponds and use the amenity areas surrounding the pond appropriately
  • Dispose of trash properly to avoid accumulation of trash in and around the pond

The benefits of a regular litter clean-up program include:

  • Reducing the potential for clogging outlet structures, trash racks, and other facility components
  • Preventing possible damage to vegetation areas
  • Reducing potential mosquito breeding habitats
  • Maintaining facility appearance
  • Reducing conditions for excessive surface algae
  • Reducing the potential for clogging outlet structures, trash racks, and other facility components

For more information, download our Stormwater Management Ponds flyer (pdf) and our Be Wise Around Water card (pdf).