Hope lies in freezing weeds

Wednesday, December 06
PITTSFIELD — Robert W. Race and James McGrath have a plot to rid Onota Lake of a pervasive enemy: They are going to freeze it.

But to do so, Race, who is president of the Lake Onota Preservation Association, and McGrath, director of parks and recreation for Pittsfield, must lower the water level by almost 6 feet.

The enemy is a foreign invasive species of water weed — Eurasian milfoil, a notorious culprit that has been choking lakes and rivers throughout the United States since the 1940s.

"You can't swim, paddle, water-ski, sail or row through it," Race said. "It creates a mat that is almost impenetrable. It's even hard to drive a motor boat through it."

It also has a dramatic effect on the lake's ecosystem, affecting all forms of aquatic species, both plant and animal.

According to information posted on the University of Maine's Web site, milfoil is considered to be perhaps the most problematic water plant that can drastically alter a body of water's ecology. It forms dense mats of vegetation that interfere with recreational activities, power generation and even irrigation by clogging water intakes.

The sheer mass of plants can cause flooding, and the stagnant mats can create good habitat for mosquitoes. Milfoil mats can rob oxygen from the water, increase the sedimentation rate and shade out other more beneficial plants. Milfoil reproduces rapidly and can infest an entire lake within two years.

"It's choking out all the good weeds, it's a hazard to boaters, and it's not fun to swim in," McGrath said. "It also takes oxygen from other species and throws off the balance of the lake."

So the city is spending about $24,500 to install some 12-inch pipes from the lake bottom leading over the dam in addition to the 24-inch pipe in the base of the dam. With both of them in operation, it should take a couple of weeks to draw down the water level enough to expose roughly 250 acres of shoreline, or nearly a third of the lake's surface, which is where most of the milfoil thrives.

Once exposed, the theory goes, the shoreline will freeze throughout the winter months, killing the weed in those areas of the lake and drastically reducing its foothold on the ecosystem.

But if it snows too much before the ground freezes, the snow acts as an insulator and could hamper the freeze on some of the shoreline.

"So, we're hoping for freezing weather without snow," Race said.

The process won't completely eradicate the weed, but because it doesn't grow well in deeper water, and much of the shallows will be exposed to the frosty weather, lake lovers are hopeful.

Race noted that this has been an ongoing battle. In 1999, the Lake Onota Preservation Association tried using chemical warfare against the weeds. And it worked — for a while. But the milfoil returned with a vengeance. Association volunteers have even been known to pull out the weeds by hand.

But lake management consultants have highly recommended drawing down the water level to freeze the weed.

The challenge has been the limited capacity of the drainage pipe in the dam. At 24 inches, it can't draw down the lake fast enough before a moderate rainfall brings it back up again. They are trying to find grant money to install more drainage capacity.


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