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Boston Harbor and Massachusetts Bay
Massachusetts Water Resources Authority

Archive

After the Outfall:
Harbor and Bay Monitoring Overview

On September 6, 2000, as part of the Boston Harbor Project, MWRA started up a 9.5-mile outfall which began discharging effluent--treated wastewaterfrom Greater Boston communities-- into Massachusetts Bay, instead of Boston Harbor. Data gathered on the quality of sediments, water, and sea life in the harbor and bay show that the Bay outfall has been functioning as anticipated–-providing rapid dilution to the effluent–-with no significant adverse impacts to the bay ecosystem.

The annual Outfall Monitoring Overview summarizes the previous year's monitoring data from the Harbor and Bay. It shows that while the harbor continues to recover from years of sewage discharges, the deeper waters of the bay show few effects from the secondary-treated effluent.

When the Deer Island Treatment Plant discharges to the harbor ended in September 2000, dramatic changes occurred near the former harbor outfalls--reductions in bacteria and ammonium concentrations, and improvements in water clarity. MWRA currently collects sampling data from Boston Harbor and it's tributary rivers and also monitors some Boston Harbor beaches.

SAMPLING SITES THROUGHOUT MASSACHUSETTS BAY
MWRA's "nearfield" monitoring stations are within about 3 miles of the outfall diffuser, to monitor any changes near the effluent discharge. The "farfield" stations are in Boston Harbor, Massachusetts Bay, Cape Cod Bay, and the Stellwagen Bank National Marine Sanctuary to assess any possible changes farther away (we have found none).

At the beginning of the Boston Harbor Project, many citizens and environmental groups were concerned that moving the effluent outfall from the Harbor to the Bay would degrade the receiving water quality. Therefore, MWRA's NPDES discharge permit requires MWRA to implement an extensive monitoring and reporting program.

Staff scientists and contractors study the water, plankton, sediment, and fish & shellfish to measure environmental effects of pollution reduction projects.

The Outfall Monitoring Science Advisory Panel (OMSAP) oversees MWRA's monitoring program, providing advice on scientific issues.

More about Massachusetts Bay

Technical Reports:

Outfall Monitoring Overview

Boston Harbor Water Quality Update

Reversal of Eutrophication in Boston Harbor