A winter drawdown is part of an effort to restore the appeal of the wide spot on Elm Creek that is surrounded by a family-friendly park.
The Champlin Mill Pond is in for a dramatic makeover this autumn and next as state and local officials plan to drain it to help manage a weed explosion.
The pond, actually a wide spot behind a dam on Elm Creek that is surrounded by a family-friendly park, has been choked in recent years with two types of plants -- coontail and curly leaf pondweed -- whose growth was encouraged by phosphorous-laden soil that has eroded into the creek upstream.
While some of the weed growth has tended to break free and clog up the dam, some has also matted and floated the 500 feet downstream to the Mississippi River, where it has clung to docks and boats. Last year the city had to truck masses of weeds away after they clogged the flow of the creek through the narrow channel under the Hwy. 169 bridge, said Todd Tuominen, Champlin's assistant city engineer.
The weeds also tend to smell as they decay in late summer. All in all, the growth has spoiled a popular recreational and gathering place that also offers a bit of visual relief to rush-hour drivers on Hwy. 169 just south of the Ferry Street bridge into Anoka.
Bill Walraven, an Elm Creek Watershed Commissioner board member who has lived on the pond's shore for 39 years, recalls that the pond was once a popular place for boating, swimming and fishing. His own kids used to sell lemonade to boaters. But that began to change about 20 years ago when weeds began to spread. The weeds, in turn, acted to trap silt flowing from rapidly developing areas upstream, Walraven said; once 6 feet deep, the pond's muddy bottom is now only 2 feet below the surface.
"It's a shame," Walraven said.
Draining the pond
The drawdown plan calls for fully opening the dam and draining the water from the pond no later than Oct. 15, leaving only a trickle through the winter. That will expose the roots of most of the weeds, as well as seeds that have fallen into the mucky bottom, to subfreezing temperatures, killing them, officials expect. The pond would then be allowed to refill in the spring, and the state Department of Natural Resources (DNR) would then assess whether the drawdown has reduced the nuisance weed growth. The process would be repeated during the winter of 2012-13.
The drawdown would, ideally, knock out invasive pondweed and let native plants establish themselves without clogging the pond.
Champlin is also looking at a $3 million replacement of the dam, originally built to power a flour mill. But the city doesn't have the money to dredge it to restore its previous depth.
"We're trying to get a better recreational use not only of the Mill Pond, but of the Mississippi River," Tuominen said. "It's exciting. Things are on the upswing for the mill pond and Elm Creek."
The city needs a permit for the drawdown from the DNR. Kate Drewry, north metro area hydrologist for the DNR, said she has received no criticism of the proposal during an ongoing public comment period, so a permit is likely to be approved soon.
A similar drawdown was carried out on the Anderson Lakes chain on the Bloomington-Eden Prairie border in the winter of 2008-09. It succeeded in knocking back some significant growth of invasive pondweed, said Kevin Bigalke, administrator of the Nine Mile Creek Watershed District.
Champlin has drawn down the Mill Pond in the past, but not for at least a decade. It's possible the city might have to repeat the procedure, but Tuominen said that recent improvements upstream on the creek, and agreements from upstream communities to control the nutrients flowing into the creek, should help control the weeds' return more effectively.
Bill McAuliffe • 612-673-7646