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Boston Harbor and Massachusetts Bay
MWRA Environmental Quality


The Massachusetts Water Resources Authority has been granted a federal National Pollutant Discharge Elimination System (NPDES) permit to discharge effluent from the Deer Island Wastewater Treatment Plant into Massachusetts Bay. As required by its permit, MWRA must post many water quality reports online.

Monthly Compliance Reports

Discharge Monitoring

Monthly monitoring results from DITP and Combined Sewer Overflow facilities are summarized in these tables submitted to regulators. (PDF)

Plant Performance Report (PDF)
Most recent data on the DITP effluent discharges.

Bacteria Monitoring at the Mass. Bay Outfall
Measurements of fecal coliform and Enterococcus in Massachusetts Bay.

Quarterly Compliance Reports

Ambient Monitoring Quarterly
List of ambient monitoring reports published in the last quarter. Includes links to technical reports and other required documents.

Contingency Plan Report on Ambient Monitoring (PDF)
Monitoring data compared with threshold limits in MWRA's Contingency Plan.

Contingency Plan Report on Effluent Monitoring (PDF)
Summary of data on pH, fecal coliform, toxicity, oil and grease, and nitrogen in DITP effluent compared with limits in the Contingency Plan.

Annual Compliance Reports

Outfall Monitoring Overview (PDF)

Demand Management Report - Assurance of Compliance with 436 MGD Flow Limit (PDF)

Annual Report on Infiltration and Inflow (PDF)

Annual Status of Plant Maintenance (PDF)

Other compliance reports, including water column, benthic, and fish and shellfish reports, are available from the Technical Reports page.

Periodic Compliance Reports

Contingency Plan Exceedance: infaunal diversity (summer 2014)

Notices of treated discharges at the Cottage Farm CSO outfall to the Charles River:
Latest-December 10, 2014

All Web Water Quality Reports (archive)