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Boston Harbor and Massachusetts Bay
Massachusetts Water Resources Authority

The Boston Harbor Project Timeline: 1986-2001

Aerial photo of discharge from Deer Island into Boston Harbor, circa 1989
Aerial photo of Deer Island without discharge, June 2002

Deer Island and the treatment plant discharge into President Roads, circa 1989.

Deer Island and President Roads
in June 2002.

Project Milestones
Effects on Plant Discharges
July 1985
Following the passage of its enabling act in 1984, MWRA assumed responsibility for MDC water and sewer systems.

Not applicable.
May 1986
Judge A. David Mazzone ordered 13-year schedule to construct new Deer Island Treatment Plant (DITP) and related facilities.

Not applicable.
December 1988
Interim repairs and upgrades to the old DITP included the provision of a more reliable disinfection system. Also, sewage scum was landfilled instead of being discharged into the harbor.
Scum removal left less oil, grease, and floating matter in effluent. Better disinfection resulted in fewer
Pumping capacity increased from about 700 million gallons per day (mgd) in 1989 to 900 mgd in 1998.
Increased volumes of wastewater treated and CSO discharges reduced.
December 1991
Sludge discharges into the harbor from the old Deer and Nut Island treatment plants ended. Sludge-to-fertilizer pelletizing began at the Fore River plant.
Solids discharged to the harbor decreased by 40 dry tons per day. Decreases in biochemical oxygen demand (BOD), nitrogen (N), phosphorous (P), and bacteria.
January 1995
First components of improved primary treatment put into service at the new DITP.
Drop in total solids discharged, as well as further decreases in bacteria, BOD, N, and P.
August 1997
Startup of Battery A, the first of three batteries of secondary treatment at DITP.
The beginning of secondary treatment marked dramatic decrease in BOD and continuing declines of bacteria, solids, N, and P.
March 1998
Battery B of secondary treatment started up at DITP.
End of effluent discharges from NITP to the South Harbor. Continued declines in total suspended solids (TSS), BOD, N, P, and bacteria.
July 1998
Inter-island tunnel completed. South System flows transferred to DITP from the Nut Island Treatment Plant (NITP), allowing most flow to receive secondary treatment. NITP was later demolished, and replaced by a headworks facility and a park.
September 2000
Start-up of new ocean outfall diffuser; effluent now discharged through a 9.5-mile outfall into Massachusetts Bay.
End of effluent discharges to Boston Harbor; effluent receives much better dilution in the bay.
March 2001
Last battery of secondary treatment placed in operation at DITP.
Treatment optimized at DITP. Discharge consistently meets effluent quality standards.

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