MWRA monitors bacteria at locations surrounding the MWRA outfall and elsewhere in Massachusetts Bay (see station map below). Water samples are analyzed for sewage indicator bacteria: fecal coliform and Enterococcus. Fecal coliform is used by the Massachusetts Division of Marine Fisheries (MADMF) to monitor water quality in shellfish areas.
An "S" following the station ID means the sample was collected at the surface; a "P" means the sample was collected below the pycnocline (collected only if a pycnocline is present).
The MADMF fecal coliform standard for unrestricted shellfishing is <14 counts/100 ml.
While not used currently by MADMF, Enterococcus is now recognized by the U.S. Environmental Protection Agency as a better indicator of public health risk to swimmers than fecal coliform in seawater. The Massachusetts Department of Public Health adopted the Enterococcus standard for swimming areas: a geometric mean of 35 counts/100 ml and a single sample maximum count (shown) of 104/100 ml.