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Massachusetts Water Resources Authority
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DATE: April, 2007
CONTACTS: Ria Convery, MWRA, (617) 788-1105 <>
Owen O’Riordan, Cambridge Department of Public Works (617) 349-4845
Stanley Koty, Somerville Public Works (617) 625-6600 ext. 5410


Alewife Brook Combined Sewer Overflows Progress Update

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MWRA 2006 CSO ANNUAL REPORT - PDF (Released 03/15/2007)

> MWRA Presentation: CSO Progress Update - PDF (March, 2007)

This notice, required by Massachusetts Department of Environmental Protection (DEP), is an annual update of the progress of Combined Sewer Overflow (CSO) control measures undertaken to improve the water quality of Alewife Brook.

You are also receiving this notice if your property lies 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 CSOs. 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 CSO 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.

As part of the Boston Harbor Case (D. Mass. C.A. No. 85-0489), the Massachusetts Water Resources Authority (MWRA) is required to undertake certain corrective actions to reduce or eliminate CSO discharges along Boston Harbor, the Mystic, Charles and Neponset Rivers and Alewife Brook. MWRA, in conjunction with the Cities of Cambridge and Somerville, is currently in the process of designing and constructing several CSO projects that, when completed, will significantly reduce CSO discharges to the Alewife Brook.

Work already completed by the MWRA, Cambridge and Somerville has noticeably reduced the number of CSO events and the total volume discharged to the brook. MWRA and Somerville closed four CSO outfalls several years ago as part of these CSO control efforts.

The next phase of CSO control work includes a stormwater outfall and treatment wetland associated with sewer separation work in the neighborhood east of Fresh Pond Reservation in Cambridge. Sewer separation in this area is expected to further reduce CSO discharges significantly by closing a major Cambridge CSO outfall and reducing stormwater flows to the MWRA sewer system. Construction of this project was delayed pending the outcome of an April 2005 appeal of a DEP issued Superseding Order of Conditions under the Wetlands Protection Act by a group of residents. The case was transferred to the Division of Administrative Law Appeals (DALA). On March 12, 2007, the DALA issued a Recommended Final Decision sustaining the March 31, 2005 permit issued by DEP. This decision is a recommendation of the DALA Administrative Magistrate to the Acting DEP Commissioner, who will make a final decision including the issuance of a final order of conditions for the project. The start of construction is dependent upon receiving the final wetlands permit approval from the Acting Commissioner.

For more information on CSOs and the CSO control program, contact MWRA at (617) 660-7971 or visit MWRA’s website at, or visit the Cities of 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 website, <>.

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. DEP has developed guidance for homeowners for responding to flooding or sewer backups, which can be found at

Available on-line at: and

Ria Convery, Massachusetts Water Resources Authority (617) 788-1105
Owen O’Riordan, Cambridge Department of Public Works (617) 349-4845
Stanley Koty, Somerville Public Works (617) 625-6600 ext. 5410

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