By Paul Tennant
---- — NORTH ANDOVER – For years, Stevens Pond has been North Andover’s most popular outdoor swimming place.
This past summer, however, local residents who were looking forward to cooling off by plunging into the pond or just lying on the adjoining beach lost most of the season due to a serious outbreak of blue/green algae, the common name for cyanobacteria.
The Board of Health closed the pond to swimming in July and the readings of cyanobacteria never dropped to the point where it could be reopened. Residents who had paid for season passes to the pond or signed their children up for swimming lessons were reimbursed by the town in August.
Town Manager Andrew Maylor told the selectmen Monday night Public Works Director Bruce Thibodeau has been looking into measures that might keep the cyanobacteria at bay and prevent a repeat of last summer’s closing.
Maylor pointed out blue/green algae cannot be eliminated from the pond entirely. They exist there naturally, he said.
Thibodeau told The Eagle-Tribune that Aquatic Control Technology of Sutton, is assessing the pond’s water to determine whether a chemical or mechanical treatment could reduce the cyanobacteria. The firm has helped the town solve water quality problems, such as weed and algae control, on previous occasions, he said.
“We don’t know what the best solution is at this point,” Thibodeau said. “We won’t know until later in the year.”
The town will not be able to apply a chemical to Stevens Pond without the approval of the Conservation Commission, he noted.
Cyanobacteria produce a toxin that is harmful to humans and pets, according to town Health Director Susan Sawyer. The toxin can be fatal to dogs — which are more apt to drink pond water than humans, she pointed out — and cause a skin rash on humans.