Cleaner water, a healthy new pond habitat, and a natural-looking amenity are among the benefits of UBC’s ongoing commitment to progressive storm water handling on the Okanagan campus.
Since 1991, campus storm water has been directed to a small, artificial retention pond with a sealed liner bed on the east side of campus, near the new Engineering-Management-Education Complex. Rather than putting the water into the City of Kelowna’s storm water system, the human-made pond was designed to look and function like a natural pond, and effectively treat storm water pollutants through evaporation and natural biological processes.
The results can be readily seen by anyone walking the Old Pond Trail, which skirts the pond. Dense cattails are thriving around the pond, sheltering a variety of waterfowl and other bird species.
Over the past 20 years, sediment carried to the pond by the storm water has accumulated to the point where it was affecting pond water quality and system function.
An engineering study commissioned by the office of the AVP Administration and Finance in May 2010 determined that pond water quality and the ability to treat incoming water would be improved by the expansion of a forebay — a space around the inlet pipe that acts as a sediment-settling area and allows future silt removal and servicing without encroaching on the larger retention pond area and its growing new wildlife habitat.
Maintaining the retention pond’s functional integrity also meant removing accumulated sediment, adding aeration and planting vegetation native to natural wetland areas.
Wildlife and habitat biologists reviewed and advised on the plan.
Sediment removal and forebay construction then proceeded carefully in March 2011 under the care of an environmental monitor to advise on environmental issues and best management practices. Construction was timed to ensure minimal disturbance to aquatic life cycles.
Before the upgrade project, dissolved oxygen concentrations in the top layer of the pond were sufficient for aquatic life. Deeper in the water the concentrations were sufficient but limiting to aquatic life. Testing will be done soon (2011) to determine if the oxygen concentrations have improved.
Because storm water flows over roads and parking areas, pollutants are often carried into any storm water system. But UBC Health, Safety and Environment staff recently measured gasoline and oil hydrocarbons in the pond, and noted that concentrations were well below provincial contaminated sites guidelines and met the Canadian Council of Ministers for the Environment (CCME) guidelines for oil and grease.
During construction of the new forebay area adjacent to the retention pond, care was taken to support the newly created environment. Silt curtains were used to prevent new sediments from affecting the adjacent pond. Noxious weed species in the retention pond were removed by hand pulling — no chemicals were used. Control of noxious weeds is required under the BC Weed Control Act, and hand-weeding allows an environmentally friendly method of control.
A variety of native non-horticultural seeds and shrubs were planted, creating vegetated banks around the retention pond’s north shore to both reduce erosion and closely mimic a natural habitat. Where vegetation isn’t quite enough to control erosion, coconut matting has also been used on the ground.
The forebay settling area and the additional vegetation planted as part of the project will combine to remove much of the future sediment before water ever reaches the pond.
The retention pond’s performance in managing storm water and the state of the new ecosystems is it supporting, will continue to be monitored. Sediment samples will be sent to a commercial lab each year to ensure that metals are not accumulating in the pond, and during spring run-off season field testing will monitor pH, turbidity and check for the presence of floating hydrocarbon contaminates — gasoline and oil — in the pond water.
Any one interested in more information on this interesting engineering feature on our campus should call the Department of Health, Safety and Environment at 250-807-8624.
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