MWRA online - home
Water System
Sewer System
Harbor and Bay
School Program
About MWRA
Doing Business with MWRA
Contact MWRA


Boston Harbor and Massachusetts Bay

Massachusetts Water Resources Authority


Massachusetts Bay

The Massachusetts Water Resources Authority (MWRA) officially opened the Massachusetts Bay effluent outfall in September 2000, and stopped discharging treated wastewater (effluent) to Boston Harbor. The results shown by years of monitoring are a cleaner Harbor and a healthy Bay. Printable pamphlet on MWRA monitoring.

Instruments on the NERACOOS buoy off Cape Ann measure temperature, salinity, chlorophyll, and oxygen.  The Overview of Environmental Monitoring pamphlet summarizes MWRA's monitoring program. For the full report on results see the Outfall Monitoring Overview report.

MWRA has monitored the bay's water quality since 1992, as part of a carefully designed Ambient Monitoring Program.  We have found that while effluent quality has improved, animal communities in the bay continue to thrive. Images from the outfall reflect a healthy, vibrant ecosystem.

MWRA monitors bacteria around the MWRA outfall and elsewhere in Massachusetts Bay.
See the results of MWRA's bacteria monitoring near the Mass. Bay outfall.

Also receiving a clean bill of health are Cape Cod Bay and Stellwagen Bank National Marine Sanctuary, a feeding ground for the right whale. Detailed results are available in the annual Outfall Monitoring Overview.

Go to The Harbor & Bay


Updated February 17, 2023