A band of “patchy vegetation” on the surface of Fawn Lake will be attacked by an herbicide sometime this fall, according to the Department of Public Works.
The application, approved by the Conservation Commission last month, was recommended by the town’s environmental consultant to the $1.8 million Fawn Lake reclamation project, which was undertaken in 2020.
Bob Hartzel, a principal scientist with the project’s consulting firm, Comprehensive Environmental, Inc. (CEI), said the vegetation was noted by town staff during the height of summer, eight months after the dredging was completed.
“It appears that dredging operations may have been sub-optimal in that area, leaving some portions of water lily rhizomes intact in the pond sediments and allowing for the observed patchy re-growth,” he said in a memorandum.
Hartzel stressed, “Despite the moderate re-growth, conditions in the dredged area are generally as expected – open water in areas that had been almost entirely covered in very dense growth of water lilies and other aquatic plants prior to dredging.”
The herbicide applied will be glyphosate, described by the consultant as “one of the most commonly used and effective herbicides for control of floating leaf species.” As recommended to maximize effectiveness, there will be a follow-up treatment next spring.
The goal of the reclamation was “to restore pond depth and provide control of aquatic vegetation in approximately 60 percent of the pond.”
Hartzel, in an email Monday, pointed out, “The remaining 40 percent along the southern shoreline was left undisturbed to provide a balance between open water and habitat provided by a natural vegetated littoral zone – an area of rooted aquatic plant growth.”
“This is important, as there may be a misperception that the dredging operation was intended to remove all vegetation from the pond,” he wrote.
CEI estimated that the cost for treatment of a one-acre area of “water lilies and other floating-leaf species” with glyphosate would range from $1,400 to $1,700, plus permitting under state law. “A more precise treatment area estimate could be provided either by GPS mapping from a boat or from drone imagery,” he told the DPW.
Mike Rosenberg can be reached at [email protected], or 781-983-1763