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Massachusetts Water Resources Authority
DATE: October 27, 2015
CONTACT: Ria Convery, MWRA

MWRA to Temporarily Lower Water Level at Foss Reservoir
for Invasive Plant Control

MWRA - "Drawdown/Freeze-Off" of Eurasian watermilfoil

The Foss Dam

Local residents and visitors near the Foss Reservoir will notice a bit more exposed shoreline in the coming months.

MWRA will perform a drawdown of the reservoir, lowering the water to 10 feet below normal elevation in order to control the growth of aquatic invasive plants.

A slow drawdown will begin on November 2, with the goal of reaching the target elevation by November 30. MWRA will monitor the response of the exposed areas to drawdown and, once it has been determined that a successful depth freeze has occurred, the water level will be restored.

The timing of water level restoration depends on temperatures and snowfall, but will likely occur in January. The MWRA drawdown plan allows for the pre-hibernation migration of amphibians.


The Foss Reservoir, located in Framingham, holds 500 million gallons of water and is an integral part of the MWRA’s emergency back-up water supply system. The Foss dam receives a detailed regulatory inspection every two years and, with MWRA’s Capital and routine maintenance, continues to be classified as Satisfactory by the MA Office of Dam Safety.

Eurasian Watermilfoil

"Drawdown/freeze-off" method of naturally curbing Eurasian milfoil
at Chestnut Hill Reservoir

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Posted November 6, 2015