The heavy rain over the last week has brought Monponsett Pond in Halifax and Hanson to record high levels – 15 inches above normal as of Wednesday – and likely to rise more. That’s not only caused problems for homeowners, it threatens to stymie attempts to control algae in the pond.
The water naturally flows from the east half of the pond, through a man-made causeway, to the west pond and past a dam into Stump Brook. The dam can allow a maximum of three million gallons a day through, not enough to keep the flood away.
A 1964 law gives Brockton control over the level of the pond, diverting up to 25 million gallons a day in reverse flow to Silver Lake in Kingston, the city’s water supply. The law stops that diversion every June first. Brockton could divert water after June first with permission from the state’s Department of Environmental Protection (DEP).
The Monponsett Watershed Association strongly opposes diversion. It worked to obtain a grant to place a chemical in the west pond to absorb phosphorous, the main nutrient for the algae blooms that have plagued Monponsett for several years. The group previously controlled algae in the east pond. Diversion would disrupt the west pond treatment and put phosphorous and algae into the east pond.
Halifax Town Administrator Charlie Selig polled selectmen and asked Brockton’s water commissioners to divert a third of the maximum daily. Brockton officials replied, saying they would ask DEP permission to divert only the maximum.
Halifax and Brockton continue negotiations.