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A $520,000 fix of this giant ravine in Baker Park has transformed a sediment laden channel into a haven for spring wildflowers. The project is intended to keep 1,081 pounds of phosphorus a year out of Lake Independence and reduce pea-green algae blooms. (Photo courtesy of Minnesota Board of Water and Soil Resources)

A newly-finished project in Three Rivers Park District’s Baker Park Reserve is designed to improve the water quality of Lake Independence. One of Hennepin County’s most heavily used lakes, it is impaired by excessive nutrients.

A 2014 sub-watershed analysis identified channel erosion in a ravine leading to the lake as a top sediment and phosphorus contributor. It carried an estimated 277 pounds of phosphorus and 300 tons of sediment — the equivalent of 23 dump truck loads — to Lake Independence annually.

Phosphorus feeds the algae that can turn lakes green.

“The lake has always had severe algal blooms,” said Brian Vlach, senior water resources manager for Three Rivers Park District. “The lake is pea-green through portions of the summer due to algal blooms.”

The $520,000 project will accomplish an estimated 15% of the phosphorus reduction needed to meet Minnesota Pollution Control Agency water-quality standards. The project came in $34,000 under budget,

Despite the algae, 832-acre Lake Independence remains a primary attraction in the metro park that saw well over a half-million visitors in 2018. The WMC deemed Lake Independence a high-priority sentinel lake, based partly on its high visibility and recreational use.

“The reduction of phosphorus in Lake Independence will clearly lead towards improved water quality and most notably water clarity,” said Joe Baker, chair of the Pioneer-Sarah Creek Watershed Management Commission.

The stabilization is a first step to reduce external phosphorus loading. To accomplish its long-term goal of increasing the lake’s clarity to 8 to 12 feet, the WMC is considering a future alum treatment to address internal phosphorus loading.

Lake Independence attracted more than 27,100 swimmers to the park’s two beaches, launched nearly 15,600 boaters from its public access and drew more than 3,400 anglers to its shore in 2018, the most recent year for which Metropolitan Council data are available.

“It has been a very good fishing lake,” Vlach said. A community of fish houses pops up during the winter. Anglers target crappies in early spring, walleye in the summer, and muskies well into the fall.

A technical advisor to the WMC, Three Rivers coordinated the project. Minnesota Native Landscapes of Otsego was the contractor. Wenck Associates of Maple Plain handled project design and construction administration.

Work was made possible by a $416,000 Clean Water Fund grant from the Minnesota Board of Water and Soil Resources. A $59,500 Hennepin County Opportunity Grant from the county’s Environment and Energy Department, plus $44,500 cost-share among the WMC, park district, Lake Independence Citizens Association and the cities of Independence and Medina covered the balance.

“Clean Water Funds by all means enable a project like this,” Baker said “The cities of Independence, Medina and a small part of Maple Plain as the cities of benefit just really would not have the funds for that. We’ve had great support from BWSR as well as Hennepin County and Three Rivers Park District to ultimately pull the funding together.”

Construction finished in mid-February.

Touch-up seeding is planned in a few spots, and the park district will plant shrubs to discourage people from entering the ravine. But little evidence of construction remained this spring, as native wildflowers and grasses emerged from erosion control blankets covering the dirt-topped structures and re-sloped banks.

“The site looks very good,” Seth Bossert, a landscape architect and project inspector with Wenck, said after a late-May visit. “We had good germination rates of the seed. It was probably 4 to 6 inches tall, so it’s starting to look more emerald-colored.”

Native plants — seven species of wildflower and nine grasses — were planted in the dirt covering rock rip-rap and topped by an erosion control blanket. In mid-December, the Minnesota Native Landscapes crew was installing rip-rap and re-sloping the ravine’s banks, moving downstream toward the lake. Newly constructed rock cross-vanes, which serve as grade-control structures, stood out against the snow.

The project was designed so park visitors won’t see a trace of construction.

Originally slated for the previous winter, the 2,200-foot channel stabilization was delayed in order to obtain a U.S. Army Corps of Engineers permit, required because of the project’s scope. Vlach said the delay resulted in more lead time and therefore lower bids.

Pending BWSR approval, the projected surplus could be used to fund smaller projects within the 7,632-acre watershed. Those might include native plantings in Baker Park rain gardens, Lake Independence shoreline restorations, a carp barrier on the Ardmore Channel or erosion control projects elsewhere in the watershed.

The grant expires in December 2020.

Estimated reductions

The Baker Park Reserve gully stabilization will reduce phosphorus-loading to Lake Independence by about 134 pounds a year, at a cost of $130 per pound. The gully stabilization is estimated to last for 30 years. The Total Maximum Daily Load Plan calls for an annual phosphorus reduction of 1,081 pounds a year.

Ann Wessel is spokesperson for Minnesota Board of Water and Soil Resources

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