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Boston Harbor and Massachusetts Bay
Massachusetts Water Resources Authority

What's New

What's New

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.


The Massachusetts Water Resources Authority samples Boston Harbor and its tributary rivers to collect harbor and river data and measure the impacts of combined sewer overflows. Boston Harbor's water quality was greatly improved by the Boston Harbor Project.

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.

Deer Island Treatment Plant sewage digesters

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

Deer Island Treatment Plant performance(PDF)

Contingency Plan thresholds compared with effluent monitoring data(PDF)

Infiltration and Inflow, Plant Maintenance

Demand Management, Flow Limitation

Combined/Sanitary Sewer Overflows

Sediment sampling in Massachusetts Bay

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