Middle Pond of Southwick’s Congamond Lake. (THE WESTFIELD NEWS PHOTO)
SOUTHWICK – The annual treatment of Middle and South Ponds for Eurasian water milfoil and curly leaf pondweed is slated for June 1.
Lake Management Committee Chair Richard Grannells said North Pond, the third pond that comprises Congamond Lake, does not have the invasive aquatics. The treatment will be performed by Solitude Lake Management of Shrewsbury.
Grannells said there are no restrictions for fishing and boating, however using the water for cooking and drinking is restricted until June 5, watering of livestock is restricted until June 7 and swimming is restricted until June 2.
Grannells said fish typically do not swim in the shallow waters where the herbicide is used so it’s not a concern. He added that the herbicide dissipates in a matter of days.
The treatment process is very hands-on. The team from the company has a GPS map of the ponds and goes out in a flat-bottom boat. When they come across an area with the invasive species, they pull up a sample and if it is Eurasian water milfoil or curly leaf pond weed, they treat the area.
Grannells said in the past that the invasives on Congamond Lake have drastically decreased.
“About 20 years ago they did a whole lake treatment using sonar,” Grannells said, adding all three ponds were infested with the invasive milfoil. “All 420 acres of water were treated and now we are down to about 15-20 acres that we treat every year.”
Grannells said the annual treatment is maintenance to prevent the situation from two decades ago from happening again.
“The Eurasian water milfoil expands quickly,” he said. “This contributes to algae blooms and it’s a vicious cycle.”
The danger, he said, is that the invasives bring phosphorus to the water.
“Phosphorus is the bad stuff,” Grannells said. “In Massachusetts and Connecticut it’s banned in fertilizers, unless it’s to start a lawn.
Last month, Congamond Lake received an aluminum sulfate treatment to reduce the nutrient phosphorus in the water.
“The alum treatment went very well,” Grannells said.
The treatment, which costs up to $800,000, was approved by Town Meeting in March. Eric Mueller of the Southwick Lake Management Committee told Town Meeting members that the lakes have 14,000 years of muck and while they are treated annually for certain algae blooms, the alum treatment is necessary to remove the muck before other algae take over. He said without it, Congamond Lake would be shut down.
