Town issues required warnings following quick storm; Tuesday’s rain brought more trouble for area
UPDATED, July 23: Cambridge issued a notice on July 22 and again on July 23 about the discharge of untreated sewage into the Alewife Brook following rainstorms on July 21 and July 22.
The state Department of Environmental Protection requires that residents be notified of combined sewer overflows (CSOs) discharges. According to the announcements posted by the town of Arlington: “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.”
The area of discharge was identified in both notices as CAM401A, which discharges upstream of the confluence of the Little River and Alewife Brook and upstream of the Route 2 Bridge. It is the same overflow that spilled sewage into the brook earlier this month.
On July 8, the city of Cambridge issued a CSO discharge notification following a quick, intense rainstorm that blew through on July 4, causing minor street flooding and forcing some holiday plans to be delayed. The effects of that rain were being felt after the skies cleared with the announcements issued by the cities of Cambridge and Somerville that there was significant discharge from the Combined Sewer Overflows (CSOs). Arlington officials sent the required CSO notification on July 6 and an additional notice on July 8.
The sewage that spills into the Alewife Brook – and sometimes into yards and homes in Arlington – comes from properties in Cambridge and Somerville. There are no reports of sewage from Arlington properties leaking into the waterways. This has been a problem for decades and has gotten more attention recently through the work of the Save the Alewife Brook organization and the town of Arlington’s Select Board.
The first of the town’s warning notices came before the rain began on July 7, with forecasters predicting up to an inch of rain before it tapers off overnight. Both notices that Arlington received from Cambridge referenced the same location (CAM401A) that allowed discharges “upstream of the confluence of the Little River and Alewife Brook and upstream of the Route 2 Bridge,” which meant the town had to send out the notice.
July 7’s day-long rain storm, welcomed by many, caused the usual concern in East Arlington for residents near the Alewife Brook.
The first notice came on the same day that Dave McGlinchey, executive director of the Massachusetts Rivers Alliance, has an opinion column in the Boston Globe on CSOs, noting that the whole region was alarmed when beaches were closed because of sewage spilling into the Merrimack River, while other areas are regularly polluted and it is overlooked.
“This urgency makes sense, because no one will tolerate raw sewage in a river, right? That sounds good, but it’s not true,” McGlinchey wrote. “Last year, millions of gallons of sewage entered rivers in Massachusetts during heavy rainstorms. These discharges, known as combined sewage overflows or CSOs, occur when older systems that carry sewage and stormwater through the same pipes exceed capacity during heavy rains. To prevent sewage from backing up into streets and homes, the excess flow is discharged into rivers.”
The town’s announcements came with a health warning. “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,” the town’s notice said.
Draft proposal for CSO fixes available for review
This latest CSO discharges come just as the MWRA, the regulatory agency overseeing the CSO issue is seeking input on how this ongoing problem can be fixed. According to a post from the city of Cambridge: “A Draft Plan to control combined sewer overflows (CSOs) has been submitted to the Massachusetts Department of Environmental Protection and the U.S. Environmental Protection Agency. Public comments will be accepted from now until Sept. 30, 2026.”
The announcement from Somerville and Cambridge says: “Do you have questions about the Draft Updated Combined Sewer Overflow (CSO) Control Plan? There are opportunities for you to learn more. The project team will be hosting in person and virtual office hours to answer your questions about the Draft Plan. You can read the Draft Plan at: voice.somervillema.gov/joint-cso-planning” The meetings are:
- Thursday, July 30, 5 to 7 p.m,, in person | Fresh Pond Apartments, community room, 366 Rindge Ave., Cambridge
- Monday, Aug. 10, 12 to 2 p.m., virtual | https://bit.ly/4uFZqsu
- Monday, Aug. 10, 5:30 to 7:30 p.m., in person |Somerville Public Library, auditorium, 79 Highland Ave., Somerville
- Monday, Aug. 24, 5:30 to 7:30 p.m., in person | Boston Public Library, Copley Square, 700 Boylston St., Boston
- Thursday, Sept. 10, 5 to 7 p.m, in person | Citywide Senior Center – 806 Mass. Ave., Cambridge
Opportunities to submit feedback:
Attend the virtual public hearings:
Thursday, Sept. 17, 6 p.m.| https://bit.ly/3ScY4rW
Thursday, Sept. 24, 6 p.m.| https://bit.ly/4fQWF46
Submit comments through the online portal:
Comments can be submitted to the project team electronically using our online portal:
https://us.planengage.com/updatedcsocontrolplan/page/home
Submit comments by email: Comments can be emailed to the project team at UpdatedCSOControlPlan@aecom.com
Submit comments by mail: Electronic comments are preferred, according to the posting, however, written comments addressed to “Draft Updated CSO Control Plan Partners” can be mailed to: MWRA, Attn: Draft Updated CSO Control Plan, 2 Griffin Way, Chelsea, MA 02150
All comments must be submitted by Sept. 30.
This news story was published on July 7, 2026, and was updated.
