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Massachusetts Water Resources Authority
April 15, 2008
mwra original logo cambridge seal somerville logo

Ria Convery, Communications Director
Massachusetts Water Resources Authority
(617) 788-1105 or

Owen O’Riordan, Assistant Commissioner of Engineering
City of Cambridge
(617) 349-4845 or

Charles E. O’Brien, P.E., Director of Engineering
City of Somerville
(617) 625-6600 ext. 5410 or


Alewife Brook Combined Sewer Overflows Progress Update


map of area

MAP - CSO Outfalls along the Little River/Alewife Brook (larger image)

cover of cso annual report - mwra


MWRA 2007 CSO ANNUAL REPORT - PDF (Released March, 2008)

This notice, required by the Massachusetts Department of Environmental Protection, is an annual update on the progress of Combined Sewer Overflow control measures to improve the water quality of Alewife Brook.  Discharges to Alewife Brook originate in the watershed communities of Belmont, Arlington, Cambridge and Somerville, all of which are undertaking programs to identify and control sources of pollution. 

You are also receiving this notice if your property appears to lie in the extended floodplain of Alewife Brook. 

The water quality of Alewife Brook is often impaired due to bacteria and other pollutants from a number of sources, including cross connections between sanitary sewers and storm drains, urban stormwater runoff and Combined Sewer Overflows.  During both wet and dry weather, Alewife Brook generally fails to meet state bacteria standards for fishing and swimming. 

Portions of Cambridge and Somerville are served by combined stormwater and sanitary sewer systems common in older cities.  There are now eight Combined Sewer Overflow outfalls along Alewife Brook that release untreated discharges during moderate and heavy rainfall.  These discharges relieve the sewer system, preventing sewage backups into homes, businesses and streets. 

The Massachusetts Water Resources Authority (MWRA) in conjunction with the Cities of Cambridge and Somerville is implementing several projects that when completed will significantly reduce Combined Sewer Overflows into the Alewife Brook.  These efforts are required by a federal court order issued to the MWRA for the Boston Harbor Clean-Up.  MWRA, along with the affected Combined Sewer Overflow communities, is implementing 35 Combined Sewer Overflow control projects along Boston Harbor, the Mystic, Charles and Neponset Rivers, and Alewife Brook.

Work already completed by the MWRA, Cambridge and Somerville has noticeably reduced the number of Combined Sewer Overflow events and the total volume discharged to Alewife Brook.  MWRA and Somerville also closed four Combined Sewer Overflow outfalls through these control efforts.

The next phase of Combined Sewer Overflow control work includes a stormwater outfall and treatment wetland associated with sewer separation work that is planned in the neighborhood east of Fresh Pond Reservation in Cambridge.  Sewer separation in this area is expected to further reduce Combined Sewer Overflow discharges significantly and result in the closing of a major Cambridge Combined Sewer Overflow outfall.  Design and construction of this project and the other Alewife Brook Combined Sewer Overflow projects have been delayed due to the filing of a citizens’ appeal of MassDEP’s Superseding Order of Conditions issued for the project pursuant to the Wetlands Protection Act.  While MassDEP has upheld its wetlands approval, the citizen petitioners have filed an appeal in Massachusetts Superior Court.  Notwithstanding the delay due to the continuing appeals, MWRA and the City of Cambridge are developing a final work plan and schedule with the goal of resuming design and construction of the Alewife Brook Combined Sewer Overflow projects beginning in 2008.

For more information on Combined Sewer Overflows and the Combined Sewer Overflow abatement program, visit its website at or visit the Cambridge and Somerville websites at <> and <>.

Updated information on water quality in the Alewife Brook watershed can be found at the Mystic River Watershed Association (MyRWA) website, < > and at a “real time” site co-sponsored by the City of Somerville and MyRWA at <>.

It is important to understand that floodwaters in all cases can present health risks, and proper precautions are necessary to minimize these risks during flooding events.  Public health officials recommend avoiding contact with the Brook during rainstorms and for 48 hours afterwards, as there may be increased health risks due to bacteria or other pollutants. The Massachusetts Department of Environmental Protection has developed guidance for responding to flooding or sewer backups for homeowners, which can be found at <>.


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