Ensuring Water Quality Through Pond Maintenance
To advance our mission of protecting and improving the watershed’s resources, the Minnehaha Creek Watershed District (MCWD) develops projects that enhance water quality and manage water quantity. Stormwater ponds are a key strategy for improving water quality and water quantity, and must be maintained to ensure their continued function. MCWD, in partnership with the Minneapolis Park and Recreation Board, the City of Minneapolis, and the City of St. Louis Park, has scheduled dredging of the Amelia and Twin Lakes Park stormwater ponds this winter, so they can continue providing valuable water quality benefits to the surrounding communities.
Located in Minneapolis and St. Louis Park, the Amelia and Twin Lakes Park ponds are two of 26 stormwater ponds MCWD maintains. The Amelia Pond treats runoff from the surrounding 307 acres before it flows into Lake Nokomis. Twin Lakes Park Pond treats runoff from the surrounding 1,390 acres before it flows into Twin Lakes, which connects to Cedar Lake.
Filtering Pollutants Leads to Cleaner Water
Stormwater ponds (or retention basins) serve a clear purpose: improving water quality in their receiving water bodies. This infrastructure captures runoff that contains sediment, phosphorus, diesel, arsenic, and other pollutants. The ponds hold the water, allowing pollutants to settle out before they can contaminate a connected water body.
Stormwater ponds require occasional dredging to remain functional; this is typically done before half of the pond’s wet volume has been filled. MCWD recently performed an analysis that determined both the Amelia and Twin Lakes Park ponds are approaching half full and therefore due for dredging.
To remain functional, sediment accumulation in both ponds should remain below 50% of the pond’s wet volume. The decrease in sediment accumulation in Amelia Pond from 2019 to 2023 is within the +/- 3% range of error.
What to Expect
While pond dredging can cause temporary impacts like increased noise and disturbed vegetation, it's critical for the long-term health of a community's water resources. Recognizing our goal of maintaining ecological integrity, MCWD is committed to minimizing impacts on the pond's ecosystem and aquatic life. Since dredging occurs infrequently and is a relatively swift process, the ecosystem and vegetation recover quickly, just in time for Spring. Once started, dredging typically takes about 4-6 weeks to complete, depending on the size and depth of the pond.
winter pond dredging
Pond dredging occurs in the winter when the ground is frozen to reduce disturbance of aquatic life and provide a more stable foundation for crews to work on.
dewatering & removal
The pond is dewatered before trucks and heavy machinery remove the accumulated sediment and pollutants and dispose of the material at an appropriate landfill.
A recovered ecosystem
After dredging, the ponds refill themselves. Any disturbed vegetation is restored in the Spring, so the ecosystem will make a full recovery.
Investing in the Minneapolis Chain of Lakes
Both the Amelia and Twin Lakes Park ponds were constructed as part of the award-winning Chain of Lakes Improvement Projects. The Twin Lakes Park pond, built in 1996, was constructed to improve water quality in Twin Lakes and Cedar Lake. The Amelia Pond was built in 2001 to address water quality issues in Lake Nokomis. These projects were completed with the expectation that MCWD and its partners would continue to manage and improve water resources in Minneapolis for current and future generations.
Today, this legacy continues, as MCWD partners with the City of Minneapolis and the Minneapolis Park & Recreation Board to develop projects in the Minnehaha Creek Corridor.
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