Combined Sewer Overflow Reporting

A combined sewer overflow (CSO) occurs when a large storm overwhelms the combined sewerage system causing rainwater to mix with wastewater and discharge to a nearby water body.  This relief measure prevents sewage backups into homes and businesses.  Cambridge owns combined sewer outfalls that discharge to the Charles River and Alewife Brook.  When a CSO occurs at a Cambridge-owned outfall, there will be a notification displayed in the table below.

Subscribe to Cambridge CSO discharge notification alerts.

The Massachusetts Water Resource Authority (MWRA) and the cities of Boston, Chelsea and Somerville manage their own combined sewer outfalls, including CSO reporting.  These communities must be contacted directly for information regarding their CSO discharges. To see where all CSO outfalls are located, download this MWRA map of MWRA and community CSO sites.

PUBLIC HEALTH NOTIFICATIONS

State regulations require local public health departments to provide notice to the public when these discharges may create a risk to public health, including when a discharge lasts for two or more  hours.  Public health warnings related to sewage discharges will be posted on this page. Currently there are no active public health warnings related to sewage discharges.

To view a full-size version of this map, click here. 

Description of CSO Locations and Potentially Affected Areas

CAM001: Alewife Brook, discharges downstream of Massachusetts Ave Bridge across from Murry Hill Road.

CAM002: Alewife Brook, discharges downstream of Massachusetts Ave Bridge

CAM401A: Alewife Brook, discharges upstream of the confluence with the Little River and upstream of the Route 2 Bridge.

CAM401B: Alewife Brook, discharges upstream of the Massachusetts Ave Bridge.

CAM005: Charles River, discharges downstream of the Eliot Bridge across from Mount Auburn Hospital.

CAM007: Charles River, discharges downstream of the Eliot Bridge across from Hawthorne Street.

CAM009: Charles River, discharges upstream of the Anderson Bridge (temporarily closed).

CAM011: Charles River, discharges upstream of the Weeks Footbridge (temporarily closed).

CAM017: Charles River, discharges downstream of the Longfellow Bridge across from Front Park.

Note: The CSO discharge table below provides details of recent discharges.  Data for CSOs is preliminary and subject to change.  Discharge duration and volume are estimates and are subject to calculation limitations, including meter data reliability, unmonitored downstream conditions such as river level, and MWRA system operations.  See the following links for information on past CSO annual reporting and yearly CSO discharge summaries.  Annual reporting data for each calendar year will be published by April 30 of the following year. Updated/revised data is indicated by ( ).