Boston Harbor and Massachusetts Bay
MWRA Environmental Quality
Now that the Boston Harbor Project has ended, there is little doubt that the upgraded sewage treatment system
has benefited the marine environment.
part of the project: to stop discharging treated wastewater (effluent) into Boston
Harbor. Instead, an underground outfall
tunnel carries effluent from MWRA communities
out into Massachusetts Bay.
|The annual Outfall
Monitoring Overview contains monitoring data from Massachusetts Bay.
Over the years, monitoring has revealed that:
The quality of the effluent (treated wastewater)
has improved, due to better control of pollution sources.
|| Chlorophyll, plankton,
and dissolved oxygen levels are normal.
of contaminants in sediment samples near the outfall are low and do
not vary much. Pictures of sediments near the outfall show healthy,
When MWRA began discharging into the Bay,
a water quality monitoring program was implemented to assess any effects
of treated sewage on the Bay. The Ambient
Monitoring Program has enabled MWRA to better understand the natural
variability in the Bay's water quality. Monitoring has shown that the water near the outfall and throughout the bays is heavily influence by river inflows, weather, and other factors.
Data continue to confirm that there are some detectable effects of the discharge near the outfall, such as increased ammonium. However, there are no detectable adverse effects at stations away from the outfall. Dissolved oxygen levels in bottom waters near the outfall have not changed and remain within state water quality guidelines.
MWRA's goals for Boston Harbor and Massachusetts Bay are based
on concerns expressed by the public during the planning of the Boston
Harbor Project. These goals include clean beaches, healthy marine resources,
seafood safe for eating, and protection of the natural beauty of the harbor
and the bay.