The Massachusetts Bay Outfall
The outfall for the Deer Island Treatment Plant is an important part of greater Boston's wastewater management program. This outfall, which started up in September of 2000, discharges treated sewage, called effluent, into Massachusetts Bay instead of into the shallower waters of the Harbor, which has helped the Harbor's recovery.
The outfall begins with a deep rock
tunnel extending under Massachusetts Bay to a point about 9.5
miles east of Deer Island. Although there was much consensus on
the need for a deep-water discharge of Deer Island effluent, questions
remained about whether Massachusetts and Cape Cod Bays could,
like Boston Harbor, become degraded by sewage effluent. The outfall
site was chosen only after considerable scientific and technical
study and extensive public participation.
To ensure that MWRA's effluent discharge does not have major effects on Massachusetts Bay, MWRA's discharge permit requires detailed reporting to both regulators and the public. In addition, the National Marine Fisheries Service issued a biological opinion that the outfall, more than 16 miles away from identified North Atlantic right whale habitat, was not likely to jeopardize the right whale or other endangered species.