Subscribe to MWRA CSO, SSO, and Blending discharge notifications
State regulations require MWRA to notify the public when certain events occur that result in untreated or partially treated wastewater being released into surface water--a river or stream, lake, or ocean. Notifications are posted online and also sent out via email and text. All Data are preliminary and subject to change.
MWRA Combined Sewer Overflow (CSO) Notifications
Some MWRA communities have combined sewer systems, where surface runoff enters the sewer and mixes with sewage during heavy rain, reducing system capacity. When the sewer system is overwhelmed, it can result in a combined sewer overflow (CSO).
MWRA has completed the final construction milestone of its Long Term Combined Sewer Overflow (CSO) Control Plan, a 25-year plan to reduce the impact of combined sewer overflows to surface waters in the metropolitan Boston area. The plan comprised 35 wastewater system improvement projects that bring CSO discharges at CSO outfalls in the Boston area into compliance with the Federal Clean Water Act.
MWRA Sanitary Sewer Overflow (SSO) Notifications
A Sanitary Sewer Overflow (SSO) is an unintentional discharge of wastewater to the environment prior to reaching a treatment facility. SSOs 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.
More about SSOs and how to help prevent them
Blending Notifications
Discharge of blended flows: In very wet weather, MWRA sometimes has to partially treat some flows in order not to overwhelm the treatment facility. These primary treated flows are blended with secondary treated flows and disinfected before discharging more than 5 miles from shore. All flows meet water quality limits.