SHOW DECREASE IN PUBLIC HEALTH RISK
Untreated or poorly treated sewage can carry disease-causing
microorganisms--bacteria, viruses, and parasites. These pathogens
can threaten public health if sewage contaminates swimming areas
or shellfish. Indicator bacteria like Enterococcus and
fecal coliform are found in sewage. If high numbers of these indicator
bacteria are present in the water, there is a risk of disease.
Historically, poorly treated wastewater and discharges of sewage
solids, or sludge, were significant sources of bacteria to the
harbor, documented as
far back as the 1930s.
Enterococcus is the measure of recreational
marine water quality recommended by the U.S. Environmental Protection
Agency (EPA). From July 1998 to August 2000, when all wastewater
was receiving secondary treatment and updated disinfection at
Deer Island and being discharged to the harbor, bacterial water
quality improved so much that most of the harbor met EPAs
most stringent swimming criteria.
Sources of bacterial pollution to the harbor are
now local: stormwater, CSOs, boats, animals, and birds all potentially
contribute to the problem. These local sources of pollution primarily
affect the harbors shoreline and beaches, the least well-flushed
areas of the harbor. Hot spots of bacteria persist
at the mouth of the Neponset River and southern Dorchester Bay;
in the Inner Harbor, especially Fort Point Channel; the mouth
of the Mystic River, and along Wollaston Beach.
More on the State of Boston Harbor