The Weaponization of Alewife Brook Water Quality

he State of Massachusetts, through its agency the Massachusetts Water Resources Authority, unfairly uses Alewife Brook poor water quality to justify not spending money to end sewage pollution. 

How does this make any sense? Well, it doesn’t. So here’s an analogy which might help the reader to better understand the MWRA’s poor thinking on the matter:

Imagine that it’s a rainy day and the city of Cambridge is driving a car on Route 16. Cambridge comes to the stop light at Mass Ave, rolls down the window, and throws a bag of stinky diapers onto the side of the parkway. MWRA is driving in a car behind them, sees Cambridge’s pollution and thinks, “Hey, why should I pay to properly dispose of my stinky adult diapers when I can just toss them out the window? There’s already some pollution here!” 

This is how the Alewife Brook’s poor water quality has been weaponized by the Massachusetts Water Resources Authority. The MWRA’s spurious argument against investment in improving public health conditions in the Alewife has been that the Brook is polluted and eliminating untreated sewage pollution will not yield a great enough improvement in water quality.

The Alewife Brook Concrete Open Overflow Sewer. Photo courtesy of MWRA.

The Causes of Poor Water Quality


Combined Sewer Overflows contain untreated sewage.

Accumulating Sediments

Contaminated Sediments accumulate and compound the problem over time.

Stormwater Runoff

Stormwater Runoff includes fertilizer, oil, pesticides, bacteria and other pollutants.

The major causes of poor water quality in Alewife Brook are combined sewer discharges (which contain untreated sewage), stormwater runoff, stormwater outfalls (which may also contain sewage), and accumulating contaminated sediments. The sediment contamination comes from sewage, stormwater, and discharges from local industry. It accumulates in the Alewife Brook’s concrete channel, and compounds the problem over time. Further upstream, pollution from Belmont flows from Winn Brook to Little River to Alewife Brook.  

These factors all contribute to poor water quality, but their relative importance is not clearly understood. Some observations can be found in the MWRA water quality report of 2014.1  Figure 4-9 of that report shows that the CSO and stormwater control work performed from 1989-1991 and from 2000-2014 has significantly reduced E. coli counts in all conditions, especially in heavy rain.2  But on average, wet weather level counts are about ten times those of drier conditions. Dry weather counts are down some but are still above the violation threshold. It does not appear that stormwater is the only problem, rather that it is more complicated, and improvements are needed in many areas.   


Solutions to Improve Alewife Brook Water Quality

Sewer Separation

The cities of Cambridge and especially Somerville need an aggressive plan to separate stormwater from sewage.

Virtual Elimination of CSOs (25-year Level of Control) or a CSO Treatment Facility

The MWRA needs to come up with a plan to achieve what they call “Virtual Elimination of CSOs”, using alternatives including underground stormwater storage tanks on State land. Alternatively, the MWRA could build a CSO treatment facility for the Alewife CSOs to treat the sewage before it is discharged into the brook.

Green Stormwater Infrastructure

The cities of Cambridge and Somerville, the Department of Conservation and Recreation, and the Department of Transportation, need to use GSI to biologically improve stormwater water quality before it enters the brook.

Dredging, Dechannelization, Bank Restoration

In 2022, the EPA wrote to MWRA, asking the agency to work with the Department of Conservation and Recreation to remove sediment from the brook. Currently, water quality remains poor even on dry weather days when a lack of CSO and stormwater discharges should mean better water quality. Dredging sediment would improve water quality by removing contaminants and reducing bacterial counts in the water on dry weather days. 

Because the Alewife is such a small and slow-moving river, nothing more than a narrow concrete channel in some places, it has accumulated several feet of CSO-contaminated sediment. During most conditions, the sediment lies beneath a foot of water. During last summer’s drought, however, there were only a couple of inches of water above the sediment in places, and the stench was unbearable. High bacterial counts likely exist because the sediment contributes to the poor water quality.4

Alewife Brook dechannelization and restoration sketch from the Department of Conservation and Recreation’s  2003 Alewife Master Plan.


1 “Summary of CSO Receiving Water Quality Monitoring in Upper Mystic River/Alewife Brook and Charles River, 2014”, MWRA Report 2015-06.
2 Note that the vertical graph scale is logarithmic with each marker being ten times greater than the one below it.
3 The dotted line shows the state geometrical mean standard for recreation of 33 counts/100 ml.The state single sample limit is 235 counts/100ml. It is that later standard that is used in determining the water quality grades.  
4 Ibid.

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