What's New with Stormwater Ponds?

The Minnesota Stormwater Research Council held its inaugural symposium, attended by government entities, engineering firms, and research institutions. The event offered valuable updates and discussions on the current science and management strategies for stormwater ponds.

Stormwater ponds are ubiquitous in the landscape, given their use as a go-to management practice since the 1980s. Some are entirely manmade, while others were retrofitted from natural wetlands. Initially, their primary purpose was to mitigate flooding. However, their water quality benefits were quickly realized – particularly their ability to capture solids (such as trash and sediment) and the pollutants that often accompany them. Today, significant effort is devoted to strategies that further enhance stormwater ponds' water quality benefits, most notably by reducing phosphorus levels. 

Photo: A stormwater pond dominated by duckweed. This can be an indicator of high nutrient levels.

Research shows that some stormwater ponds provide minimal nutrient-reduction benefits or can even act as a source of phosphorus. A pond's performance in this realm is difficult to predict, monitor, and correct. While extensive monitoring of a pond's chemistry, biology, and hydrology will paint the clearest picture, sometimes simpler metrics such as duckweed abundance, wind shelter, volume, age, and soil composition can provide valuable insight. Where problems exist, best management practices, such as dredging or vegetation management, can help.

Pond maintenance is often logistically challenging and requires a coordinated effort. Partnerships among pond owners (typically cities or HOAs), adjacent landowners, private firms, and local government entities with expertise is often essential to improve pond function. Learn more about stormwater ponds HERE or by watching the "Our Stormwater Pond Connection" video. For more information, contact Breanna Keith, Water Resource Specialist, at This email address is being protected from spambots. You need JavaScript enabled to view it.. 

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Stormwater Treatment Projects Being Constructed at Coon and Martin Lakes

By the end of September 2020, both Coon and Martin Lakes will have new treatment of stormwater before that water reaches the lake. Two stormwater ponds at Martin Lake are being renovated. One new rain garden at Coon Lake is being constructed.

The two stormwater ponds already exist on the shores of Martin Lake at 228th Place and 230th Avenue (see map). Like a full vacuum cleaner bag, they have captured as much sediment and nutrients as is possible. To call them "ponds" today seems generous. Each will be made deeper than the original design, like replacing an old, full vacuum cleaner bag with an empty, bigger bag. Pollutant removal will be more than 50% greater than when the ponds were originally designed and new. Water reaches the ponds by pipes that capture water from several acres of surrounding neighborhood, including roads.

The rain garden at Coon Lake will capture curbside water that today is piped to Coon Lake without treatment. The curb will be cut creating entrances to the approximately 1 ft deep basin. Sandy soils allow quick infiltration of the water. A special underdrain ensures no standing water. Native plants create a garden appearance. The owner of the property on Channel Lake has agreed to maintain the garden.

Images show project locations and condition of the stormwater ponds before renovation.

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