The Mystery of Mirror Lake: How a Peruvian crew is helping the lake live up to its name

Innovative method removes underwater carpeting of invasive plants and years of duck droppings.

A team of experts, including a crew from Peru, has been working for almost a week to help the University of Connecticut’s Mirror Lake live up to its name… because until now, the campus landmark looked more like The Black Lagoon Lake.

Over the last couple of decades, the university has tried many methods to keep Mirror Lake clean, from installing air circulators to trying to ban the late, legendary “Duck Lady” from feeding the ducks, in an effort to cut down on their contribution to the nutrients in the lake, not to mention, underfoot. (And to get them to leave for the winter, rather than freeze to death.)

Good for the aquarium, bad for the lake

The lake’s main problem, however, is an invasive plant that many of you may have in your home. It is a plant sold to add greenery to aquariums. The characteristic that makes it an ideal plant for this use is the same one that makes it a nightmare when let loose in the natural world.

It’s called Elodea canadensis. And it’s something fish won’t eat. Good for aquariums. Bad for lakes, ponds and other bodies of water.

Put Elodea canadensis in a shallow body of water like Mirror Lake, which is about 5- to 6-feet deep, add lots of bright sun, and you’ve got great growing conditions. Nutrients washed into the lake by rain runoff and the fertilizer contributed by ducks give it a real boost.

Besides clogging up the lake and making it stink, these weeds eventually suffocate the beneficial organisms that live the bottom of the lake.

“The entire bottom of the lake was like a shag carpet,” said Richard Windels, owner of Northeast Pond Restoration Services, who also serves on the board of the Rivers Alliance of Connecticut

He and Dave Roach, owner of All Habitat have been hired by the university to get rid of the stuff - without the use of herbicides.

He calls it ‘Inca-nuity’

The team is using a method inspired by one used in Peru. Their crew includes about a half dozen men from that country. Giving a nod to their expertise, Windels said, “I call it ‘Inca-nuity.’”

The Peruvian crew can be seen out on the water, dragging up mats of Elodea and feeding them into what looks like a floating lawnmower, in a process called “suction harvesting.”

The weeds are ground up and liquefied by the cutter head on the boat and sucked through 6-inch pipes to a holding area on the shore.

“The boat has a powerful hydraulic pump that can pull up to half a mile away,” Windels explained.

The really cool part is what happens in the holding area.

The disgusting, thick black sludge sucked into the holding area is mixed with a special flocculant (think of the word “flakes”) that’s used in waste-water treatment plants. This material causes the solids in the sludge to separate from the liquid and sink to the bottom. The material is similar to what’s used in swimming pools.

What comes out of the filtering bed is clear water.

“All of the water from the lake is pumped through twice,” Windels said. “It’s kind of like dialysis.”

Roach added, “What we’re dealing with then, is three things: invasive plants that are suffocating the lake; duck poop that’s contaminating the lake; and metals from runoff.

An unexpected research project

The cleansed water is released slowly across the grass on the shore - which has turned out to be a delight to the ducks. “Because the ground is saturated, the worms are coming up,” Roach said.

Nearby, a mother duck and her babies were feasting on the wrigglers.

“They know where to find a good meal,” Windels said.

“Hundreds” of people have stopped to talk to Windels and Roach since the project began, but the most enthusiastic have been researchers and students from the environmental sciences department who have been sampling the lake water at intervals since the project began, Roach said.

“They will do a post-treatment analysis to measure the impact on the pond. This is interesting for us because we have some theories, which now may be scientifically supported,” he said.

This is the first time his company has cleaned a lake by removing only the weeds, he said. Normally the lake sediment would have been dredged up with the weeds.

These volunteer researchers also will analyze the sludge leftover after all the water has been filtered, to see if it can be recycled by combining it with leaf compost or wood chips and used as soil. “So, they’re looking for an end use,” Roach said.

Fruit-of-the-Loom grows here, too?

Besides the Elodea, the crew also is scooping out another overgrown plant called Wolffia that covered the surface of the 5-acre lake.

Occasionally they come across other debris that cannot be fed into the cutter head, such as plastic fraternity banners that once hung in the trees on the little island in the center of Mirror Lake.

“We’ve also come across a lot of underwear,” Windels said.

In a separate project, the university has thinned some of the trees on the island, and will be planting an “understory” of Mountain Laurel and rhododendron.

The goal is to complete the cleanup by Thursday, the day before UConn students and their families arrive for move-in day.

“The lake will look a little bit murky for a few days, but then it will be clearer than it’s been in 30 years,” Windels said.

Two local guys apparently like the way it looks now. When they appeared in the lake with inner tubes, they had to be shoo’ed by Tom Callahn, UConn’s Associate VP for Operation and Administration.For more information about the history of Mirror Lake try this link.

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For more information: http://mansfield.htnp.com/news/uconn_mirror_lake_cleanup_august_2008.html