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Massachusetts Water Resources Authority
March 15, 2013

Ria Convery, MWRA
(617) 788-1105,

MWRA Releases Annual Combined Sewer Overflow Progress Report
More Information
CSO Annual Report for 2012 - Cover

CSO Annual Progress Report for 2012 (PDF)

Community Planting Day Alewife Brook
Community Planting Day in Main Wetland Basin, Alwewife Brook - July 2012

CSO volume reduction by receiving water
CSO Volume Reduction by Receiving Water

MWRA submitted its Annual Progress Report on Combined Sewer Overflows (PDF) to federal district court Judge Richard G. Stearns on March 13, 2012, as part of the Boston Harbor cleanup case. The report describes the progress made by MWRA in cooperation with the Boston Water and Sewer Commission (BWSC), the cities of Cambridge, Chelsea, and Somerville, and the Town of Brookline.

Overall CSO Control Program Progress:
To date, MWRA has completed 29 of the 35 projects in the $860 million long-term control plan. CSO volume has been reduced by over 2.5 billion gallons a year. Four projects are underway, and the remaining two projects are scheduled to be awarded later this year.

When the program is completed in 2015, system-wide CSO discharge volume will be reduced from 3.3 billion gallons in 1988 to 0.4 billion gallons, with 93% of the remaining discharge volume receiving treatment at MWRA’s four CSO facilities.  

Progress highlights for 2012:
Construction began on Contract 8A of City of Cambridge’s CAM004 Sewer Separation Project to remove large volumes of stormwater from Cambridge and MWRA sewer systems, reduce CSO discharges to Alewife Brook and allow the closure of Outfall CAM004.

The City of Cambridge’s project to treat separated stormwater using green, innovative technology continued. A new, 4-foot by 8-foot box culvert storm drain to convey separated stormwater to a new, 3.4-acre wetland in the Alewife Brook Reservation will be substantially complete in April, 2013.

Progress on BWSC’s Reserved Channel Sewer Separation Project continued. Contract 3A, the separation of combined sewers in a 33-acre, primarily residential area of South Boston, reached substantial completion in 2012. Construction began on Contract 4, which will separate sewers in a 182-acre, primarily commercial and industrial area.

Design commenced for the last two CSO Control Plan projects, which are intended to lower CSO discharges into Alewife Brook, provide sewer system relief in extreme storms and control the discharge of floatable materials at outfalls MWR003 and SOM01A.



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Posted January 24, 2013