The Alewife Brook After CSO Discharges

After receiving notification of multiple Combined Sewer Overflow (CSO) activations in the Alewife Brook, filmmaker Clare Nosowitz grabbed her video camera and her rain coat and headed out the door. The date was October 26, 2021 and the Alewife was experiencing rain at the start of a gusty autumn Nor’easter.

On this day, less than an inch of rain fell before activating Somerville’s lone Alewife Brook CSO, known as SOM001A. According to Somerville’s DWP website, just .92″ of rain caused SOM001A to discharge for 45 minutes. This resulted in an estimated 1.42 million gallons of untreated sewage contaminated water, all from Somerville, discharging into the Alewife Brook.

SOM001A on 10/26/2021, 7 hours after Somerville’s 1.42 million gallon sewage water discharge. Film credit: Clare Nosowitz.

Currently, there are six CSOs in the Alewife Brook, which discharge sewage contaminated stormwater during some rain events. The worst CSO is SOM001A, Somerville’s only active CSO in the Alewife Brook.

The six existing CSOs in the Alewife Brook. Map taken from the MWRA website.

But Somerville was not the only neighbor discharging untreated sewage water into Arlington’s Alewife Brook on that morning. Further upstream, the MWRA and Cambridge were also discharging sewage water into the Alewife Brook. In fact, five of the six Alewife CSOs, SOM001A, CAM001, CAM401B, CAM401A, & MWR003, were activated, discharging an estimated 2.5 million gallons of sewage water into the Alewife Brook between 6 and 8 am.

Here is video of the filthy water moving quickly in the Alewife Brook, towards the Mystic River. The film maker caught this shot while heading upstream from SOM001A, towards Massachusetts Avenue.

Polluted water flows downstream in the Alewife Brook hours after Cambridge CSOs and the MWRA CSO were activated. Film credit: Clare Nosowitz.

Further west, at the mouth of the Alewife Brook, Cambridge’s CAM401A is physically the first CSO in the brook. It defines the start of the brook and it is hidden (out of sight, out of mind?) behind the cylindrical parking ramp at the Alewife T. CAM401A discharged .7 million gallons of sewage water for 90 minutes on that morning.

Cambridge’s CSO CAM001A, filmed six hours after discharging sewage water at the mouth of the Alewife Brook. Film credit: Clare Nosowitz.

Fortunately, the Alewife did not experience any flooding on this day. New England’s favorite meteorologist, Dave Epstein said of this storm, “If this storm had occurred at the time of astronomical high tide, we might be looking at record-breaking flooding in Boston.”

View recent CSO activations in the Alewife Brook:
Alewife Brook Combined Sewer Overflow (CSO) Control | City of Somerville ( *
Combined Sewer Overflow Reporting – City of Cambridge, MA (
MWRA’s CSO Reporting Page

* Note: SOM001A was activated again just four days later, on October 30th, 2021. However, Somerville does not update their CSO notification page within 48 hours of their CSO activations. This is why, at the time of this publishing, that on 11/2/2021, there is still no mention of this most recent CSO activation.

One thought on “The Alewife Brook After CSO Discharges

  1. Deeply appreciate your efforts here. testing of the water at this time might be especially significant in efforts to close these outfalls. thanks again!

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