QUECHEE — The Quechee Lakes Landowners Association is hoping a new herbicide approved last year for use in Vermont will help control invasive plants plaguing Lake Pinneo.
The association, which owns and maintains the 42-acre lake near the banks of the Ottauquechee River, wants to use the chemical ProcellaCOR to halt the spread of Eurasian watermilfoil, an aquatic plant known to harm ecosystems and interfere with swimming and boating.
The QLLA filed an application this spring asking state regulators to sign off on the herbicide, which mimics a growth hormone that causes the overgrowth of cells and ultimately kills the plant.
Treating the lake would take a single day and pose no threat to other plants or swimmers, according to Ken Lallier, property manager of the Quechee Club, which is part of QLLA.
Without it, he worries that watermilfoil will continue to spread, eventually covering the lake entirely.
“If we do nothing to Lake Pinneo, the entire surface of the water will have weeds on it,” he said in a phone interview Tuesday.
Swimmers could get tangled up, while fishermen will have trouble casting lures past the weeds, he warned.
But Hartford officials have their own concerns and submitted a letter late last month taking issue with the proposed chemical treatment.
There’s no long-term plan for water testing and it’s unclear that Lake Pinneo’s liner — installed in 1974 and repaired in 2013 — is still fully intact, wrote Richard Kenney, the town’s chief water system operator.
Kenney worries that the chemicals could leach into the groundwater and possibly impact a town-owned well about 250 feet northwest from the lake.
“While we are sympathetic of the permittee’s frustration with trying to rectify the milfoil problem in Lake Pinneo, we must assure that the users and ratepayers of the Quechee Central Water System continue to receive safe quality drinking water and be protected from any costs from possible and preventable contamination,” he wrote.
The conflict is reminiscent of the QLLA’s attempts to use a different chemical called Sonar to manage Eurasian watermilfoil two years ago.
In that case, the Vermont Department of Environmental Conservation denied the association’s request after a public comment period where Kenney questioned whether the proposal did enough to protect the town’s well.
At issue was the three-month window needed to treat Lake Pinneo with Sonar, according to Lallier.
Using ProcellaCOR, which uses the herbicide florpyrauxifen-benzyl as its active ingredient, the lake would only have to be closed for one day to prevent swimmers from interfering with equipment, he said, adding the new chemical dissipates to undetectable levels in three days.
“It’s an even safer chemistry,” Lallier said of the new herbicide. “It has no drinking water standard, so you can essentially drink the treated water and the toxicology issues are less than Sonar.”
QLLA also hired a hydrologist who found that the aquifer under Lake Pinneo flows away from Hartford’s well, meaning any chemicals that may get into the groundwater could be carried away, he said.
Vermont issued four permits last year for ProcellaCOR “and it went very well,” according to Oliver Pierson, the lakes and ponds program manager at the Vermont Watershed Management Division.
“Our monitoring has shown high impact on the target species of Eurasian watermilfoil and negligible non-target impacts,” he said in an email Tuesday.
QLLA’s application calls for the treatment of 17 acres of water this year. That would be combined with suction harvesting, where divers remove watermilfoil from the roots using a vacuum-like device.
Together, the techniques are expected to cost $45,000 this year, the application says.
Herbicide treatments also are scheduled for 2021 and 2022.
Lallier said the association has tried other ways of controlling the plant since it was first discovered in Lake Pinneo in 2011 after Tropical Storm Irene.
Divers have attempted to hand-pull the weeds, but the two- to three-week efforts usually only clear a half-acre section of the lake near the beaches, he said.
“It’s beyond what you can hand-harvest, it’s way beyond that,” Lallier said.
The Vermont DEC plans to have a response to the town’s letter by late July, according to Pierson.
“What typically happens next is that we issue the permit along with the comments and our response,” he said. “It is possible that public comments will require us to do additional analysis, research or evidence-gathering and could even lead us to deny the permit application.”
Tim Camerato can be reached at tcamerato@vnews.com or 603-727-3223.