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Boston Harbor and Massachusetts Bay
Massachusetts Water Resources Authority

Contingency Plan Exceedances

MWRA's NPDES discharge permit requires MWRA to report Contingency Plan exceedances to regulatory agencies and the public. These notices are triggered by unusual results of effluent or ambient monitoring. Effluent monitoring takes place in the treatment plant, while ambient monitoring examines the environment surrounding the outfall in Massachusetts Bay.

Caution and Warning Level Exceedances

Year Exceedances (Links to PDF Documents)
2017 Nuisance algae (Alexandrium)
2016 Nuisance algae
2015 Nuisance algae
2014 Biodiversity Nuisance algae
2013 Biodiversity
2012 Biodiversity Nuisance algae Red tide
2011 Biodiversity Red tide
2010 Biodiversity
2009 Red tide
2008 Red tide
2007 Nuisance algae
2006 Nuisance algae Chlorophyll Effluent toxicity Red tide
2005 Nuisance algae Effluent toxicity Red tide Red tide
2004 Effluent bacteria Nuisance algae
2003 Nuisance algae Mussel bioaccumulation
2002 PAH and chlordane Nuisance algae Effluent solids Effluent solids Effluent solids
2001 Mussel bioaccumulation Effluent bacteria Effluent toxicity Effluent toxicity
2000 Effluent chlorine Effluent pH Ambient chlorophyll Ambient dissolved oxygen

Many of our reports are in PDF format, which requires Adobe Acrobat Reader®, a free program available from Adobe Systems. To request a paper copy of any report, please contact the MWRA Environmental Quality Department at 617-788-4941, or e-mail us at