Boston Harbor and Massachusetts Bay
MWRA Environmental Quality Department

CSO Variances

MWRA has been granted variances by the state Department of Environmental Protection from having to meet water quality standards in the Lower Charles River Basin and in the Alewife Brook/Upper Mystic River; The variances are expected to be extended until MWRA fully implement its plan to reduce the impacts of combined sewer overflows (CSOs) in the harbor and rivers.

In accordance with the conditions of the Lower Charles River Basin Variance for Combined Sewer Overflows (CSO) issued by the Department of Environmental Protection (DEP) to the MWRA on October 1, 2010, MWRA provides notification on this page of any CSO discharges of treated combined sewage at the Cottage Farm CSO Treatment Facility in the Charles River.

Notice of Treated CSO Discharge October 4, 2011 (PDF)

Notice of Treated CSO Discharge September 8, 2011 (PDF)

Notice of Treated CSO Discharge August 28, 2011 (PDF)

Notice of Treated CSO Discharge August 27, 2011 (PDF)

Notice of Treated CSO Discharge August 10, 2011 (PDF)

Notice of Treated CSO Discharge August 7, 2011 (PDF)

Alewife Brook CSO Progress Update(April 15, 2011)

For older CSO postings, see the Archive Page.

More about CSOs and the CSO variances