NORTH ANDOVER — The selectmen last night unanimously approved putting aluminum sulfate into Stevens Pond in an effort to prevent another outbreak of blue-green algae.
The board accepted the recommendation of Public Works Director Bruce Thibodeau, who said he believes an early treatment of the chemical will get rid of the blue-green algae, which are actually cyanobacteria. Stevens Pond, a popular swimming place, was closed for most of last summer due to the onslaught of the cyanobacteria.
Biologists from Aquatic Control Technology, a firm that advises the town on water quality, said at a Jan. 30 meeting about Stevens Pond that the use of aluminum sulfate could prevent cyanobacteria. They also said aeration is among the methods of fighting blue-green algae, but Thibodeau noted Stevens Pond is not deep enough for that option to be effective.
Thibodeau said the aluminum sulfate that will be put into Stevens Pond will be in the form of a powder. He said last night he is not sure exactly when the treatment will take place. He agreed with Selectman Donald Stewart, who suggested the tiny quantity of snow the area received last winter, resulting in less water flowing into the pond from melting snow, may have contributed to the cyanobacteria outbreak.
The biologists from Aquatic Control Technology said flushing a pond can help to prevent the growth of the algae. Thibodeau pointed out that “not an awful lot of water goes into and out of Stevens Pond.”