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Boston Harbor and Massachusetts Bay
Massachusetts Water Resources Authority

CSO Variance

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), 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.

Notices of treated discharges at Cottage Farm CSO in Cambridge

2010 Feb 25 Mar 16 Mar 23 Mar 31 Jun 6 Jul 10 Aug 5 Aug 25
2011 Aug 7 Aug 10 Aug 27 Aug 28 Sep 8 Oct 4    
2012 Jul 18 Sep 19 Oct 29 Dec 27        
2013 Jun 8 Jul 23 Dec 29          
2014 Oct 23 Dec 10            
2015 Jul 10 Sep 30            
2016 Oct 22              
2017 Jun 17 Oct 17            
2018 Jul 17              

MWRA website notifications of treated discharges (in the past 2 days)

City of Cambridge website notifications of discharges to Alewife Brook

CSO Annual Discharge Estimates and Rainfall Analyses Reports (2014-present)

More about CSOs

Many of our reports are in PDF format, which requires Adobe Acrobat Reader®, a free program available from Adobe Systems.