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Boston Harbor and Massachusetts Bay
Massachusetts Water Resources Authority

What's New

What's New
in Environmental Quality

MWRA monitors Boston Harbor and Massachusetts Bay, measuring pathogens, metals, toxicity, and other water quality indicators. The latest web reports in compliance with MWRA's NPDES discharge permit are listed on this page. The Contingency Plan, which is part of the permit, sets out thresholds that when exceeded require reports that are listed here.


MWRA samples Boston Harbor and its tributary rivers to measure the impacts of combined sewer overflows and analyze data. Download monitoring data here.

Harbor beaches are tested daily in summer, and warnings are posted when high bacteria counts are found. Beach water quality data are available for download.

Download a printable PDF pamphlet on bacterial water quality in the Harbor, rivers, & beaches.

Press Release: How Clean Is Boston Harbor?


Massachusetts Bay and Cape Cod Bay are measured for Nutrients, organic material, toxic contaminants, pathogens, and solids.

Bacteria Monitoring in Massachusetts Bay

Ambient monitoring quarterly: reports published in the last quarter (PDF)

Contingency Plan thresholds compared with ambient monitoring data (PDF)

Proposed Contingency Plan modifications

The Outfall Monitoring Overview annually summarizes results of Mass. Bay monitoring.

Inspection video from the Bay outfall (YouTube)

Discharge Monitoring Reports for Treatment Plant and CSO facilities (PDF)

Contingency Plan thresholds compared with effluent monitoring data(PDF)

Infiltration and Inflow (PDF)

Demand Management, Flow Limitation (PDF)

Combined/Sanitary Sewer Overflows

Deer Island Treatment Plant performance (PDF)

Treatment Plant effluent monitoring data

Treatment Plant maintenance report