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Boston Harbor and Massachusetts Bay
Massachusetts Water Resources Authority


Sanitary Sewer Overflow Reporting

A Sanitary Sewer Overflows (SSO) is an unintentional discharge of wastewater to the environment prior to reaching a treatment facility. SSOs can occur on infrequent occasions when the capacity of the sewer system is exceeded, usually due to extreme conditions such as heavy rainfall, or an obstruction or break in sewer lines. During such events, flow may be discharged to local receiving waters, without treatment, as a last resort to reduce the risk of sewage backing up into homes and businesses. For more information see What is an SSO?

Note: Public health officials recommend avoiding contact with receiving waters for up to two days after SSO discharges have ended.

On the following map of MWRA SSO sites, select a time period to view where any SSOs may have occurred. Hover over individual red or yellow markers to view SSO times and links to detailed reports. If there are no SSO events during the selected period, the map will display no markers. Additional information will appear in the popup window if multiple events occurred during the selected period.

Select time period to display where SSO events occurred:
* *
SSOs active within the past two days appear as red markers     and older events are yellow    .

*Information is preliminary and is subject to change.

SSOs displayed on this map have been reported to the Department of Environmental Protection by MWRA. The map above displays SSOs occurring only within the MWRA system and does not include SSOs for community systems.  For additional SSO information, see:

DEP background on SSO regulations
DEP searchable reportable release site list
Boston Water and Sewer (BWSC) SSO notifications