Jun 7, 2025

As of July 6, 2022, the Massachusetts Department of Environmental Protection requires that residents be notified of combined sewer overflows (CSOs). A combined sewer overflow (CSO) occurs when a large rainstorm overwhelms the combined sewage system causing stormwater to mix with wastewater (or sewage) and discharge to a nearby river or lake. These events are usually due to extreme conditions such as heavy rainfall or an obstruction or break in sewer lines. 

Arlington received the following CSO Report from Cambridge

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

Public Health Advisory 

Arlington's Health Department strongly advises residents and their pets not to swim or stand in the water as there may be increased health risks due to bacteria or other pollutants associated with urban stormwater runoff and CSO discharges. 

View full Advisories from Cambridge, Somerville

For additional information on Cambridge CSO reporting and to subscribe to being alerted of CSOs directly from Cambridge, please visit cambridgema.gov/CSOreport 

For additional information on Somerville CSO reporting and to subscribe to being alerted of CSOs directly from Somerville, please visit somervillema.gov/cso 

For more information on area discharges, visit mwra.com/harbor/html/cso_reporting.htm.