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Boston Harbor and Massachusetts Bay
Massachusetts Water Resources Authority


MWRA has closely monitored the Harbor and Bay
since the Bay outfall started up

Boston Harbor Results

On September 6, 2000 MWRA started up a 9.5-mile outfall which began discharging Greater Boston's treated wastewater (effluent) into Massachusetts Bay, instead of Boston Harbor. When the Deer Island Treatment Plant discharges to the harbor ended, dramatic changes occurred near the former harbor outfalls--reductions in bacteria and ammonium concentrations, and improvements in water clarity.

Data gathered by MWRA and contractors on the quality of sediments, water, and sea life in Boston Harbor and Massachusetts Bay show that the Bay outfall has been functioning as anticipated–-providing rapid dilution to the effluent–-with no significant adverse impacts.

Massachusetts Bay Results

MWRA's "nearfield" monitoirng stations are within about 3 miles of the outfall diffuser, to monitor any changes occurring near the discharge. The "farfield" stations are in Boston Harbor, Massachusetts Bay, Cape Cod Bay, and the Stellwagen Bank National Marine Sanctuary to assess any changes that may be occurring farther away.

MWRA's NPDES discharge permit for the Bay outfall has strict monitoring requirements designed to identify unexpected impacts fromthe discharge. At the beginning of the Boston Harbor Project, many citizens and environmental groups were concerned that moving the effluent outfall from the Harbor to Massachusetts Bay would degrade the receiving water quality. To address these concerns, Regulators required MWRA to implement an extensive monitoring program for as part of it's discharge permit. MWRA or its contractors study the Bay's water, plankton, sediment, and fish and shellfish to measure environmental effects of MWRA pollution reduction projects. To date, the water quality in the Bay has not been cause for concern.

MWRA's monitoring program is overseen by The Outfall Monitoring Science Advisory Panel (OMSAP), which provides advice on scientific issues.

MWRA's goals for Boston Harbor and Massachusetts Bay are based on concerns expressed by the public during the planning of the Boston Harbor Project. These goals include clean beaches, healthy marine resources, seafood safe for eating, and protection of the natural beauty of the Harbor and the Bay.

More about Massachusetts Bay