Bare Hill Pond underwent spring cleaning last week when Pristine Waters, a waterfront restoration company, performed suction harvesting in the swimming area at the town beach to remove non-native, invasive weeds. The project began Monday, June 10, and ran through Friday, June 14, during which time the beach was closed to swimmers.
Diver Greg Metrey speaks with a coworker after collecting milfoil with a vacuum hose that feeds into a collection dumpster where the weeds are retained and dried out. (Photos by Lisa Aciukewicz)
The project began Monday with eager spectators watching from the beach as divers disappeared from sight to begin manually pulling Eurasian milfoil and fanwort from the bottom of the pond and feeding them into a large suction tube that evacuated into a specialized dumpster in the boat launch parking area. Within 15 minutes, it became abundantly clear the weed removal was going to need a trip back to the drawing board.
Pristine Waters President Marc Amler watched as the dumpster began filling with water and shut the suction down before it could overflow. “One of the things I couldn’t tell from being remote [during the planning phase],” said Amler, “was the kind of grade this [dumpster] would be sitting on.” The container sat on an 8- to 10-degree angle, meaning there was a lot less space for water collection.
Chaz Tuz dumps a pile of milfoil onto the dock. Part of the extraction process includes hand collecting the weeds
In addition to the grade on which the dumpster sat, another complicating factor was the pond itself. According to Amler, the bottom of the pond has a layer of rich organic sediment. As the divers pulled the weeds, much of this sediment entered the closed loop suction harvesting system and clogged the 130-micron filter lining the dumpster. The filter is part of the weed remediation technique, ensuring that no return fragments of the plant enter the water.
“Every piece of plant has the potential to be an entirely new plant,” Amler told the Press in an interview at the pond. He added, “98 to 99% of the sediment pulled with plant matter gets collected. The roots pulled up a lot of organic material, [we had the] wrong liner, so it was getting clogged and wouldn’t drain. Whenever you do a new project, you don’t know what you’re getting into. There is a day or two of tweaking the system; they don’t come manufactured for you. Once you find that, rinse and repeat.”
Finding a groove
By Wednesday afternoon, the team had installed a new 250-micron filter, which was better at letting water pass through while still ensuring plant fragments did not reenter the pond. The harvesting reached stasis, meaning the water entering the dumpster was draining at an equal rate while the weeds were left behind.
By Friday, the swimming area, up to the second dock, was cleared of invasive weeds. The project was always intended to be completed in two phases. Pristine Waters will come back at the end of the beach season to finish suction harvesting the rest of the swimming area and possibly the area around the boat launch and docks.
Milfoil in Bare Hill Pond: A brief history
Bruce Leicher, chair of the Bare Hill Pond Watershed Committee, was on-site and excited with Pristine Waters’ progress. “Every pond is different,” he said. “The conditions here required some tweaking. People wanted to know what would happen if we didn’t do a drawdown? We now know.”
Leicher was referring to the past two years when the pump installed to draw down the pond to control overgrowth of non-native, invasive weeds malfunctioned. In a brief history lesson, Leicher explained how milfoil and fanwort entered the pond in the first place: “Milfoil was a primary plant people would put in fish tanks,” he said. “When people would empty [the] tanks, it’s hard to believe, but [Eurasian milfoil] populated the entire United States that way.”
The U.S. Fish and Wildlife Service backed Leicher’s claim in its 2015 ecological risk screening summary stating, “Long distance dispersal has been linked to the aquarium and aquatic nursery trade. Spread occurred as the species was planted into lakes and streams across the country. Transport on boating equipment plays the largest role in introducing fragments to new waterbodies.”
According to Leicher, Harvard bought a harvester in 1984, the year after the town voted to ban the use of herbicides in the pond, to cut the weeds down. “By the end of the ‘90s, the state declared the pond endangered because the invasives took over the entire bottom,” recalled Leicher. “The drawdowns controlled it. We are now seeing what happens when you don’t do it for two years.”
Drawdowns to resume
Drawdowns allow the water to freeze, which kills the non-native plants. The pump malfunctioned in 2021 so there was no drawdown. In 2022, the repaired pump, which was installed 17 years prior and had an average life expectancy of 10 years, finally reached the end of its operability. A new pump was purchased with funds from the American Rescue Plan Act of 2021 and will be installed in July, according to Leicher. Drawdowns will resume in fall 2024.
Mark Amler of Pristine Waters holds a tarp away from a metal grate to allow water to flow out of a filtered hose and back into Bare Hill Pond during milfoil extraction to clear the beach area of the invasive weed. The beach was closed for the project but is now reopened.
