Cambridge to Temporarily Switch to MWRA Water for Remainder of 2022

8/26/20221 year ago

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The City of Cambridge will temporarily begin sourcing its water from the Massachusetts Water Resource Authority (MWRA) starting Tuesday, August 30, 2022. The Cambridge Water Department anticipates that the MWRA will exclusively supply all of Cambridge’s public water through the end of the year. Even though Cambridge owns and maintains its watershed, it is also a member of the MWRA. 

The two contributing factors to Cambridge’s decision to temporarily switch to MWRA water are increasing Per- and Polyfluoroalkyl Substances (PFAS) levels in our finished water and supply chain delays for the upcoming replacement of the filter media used to treat the drinking water at the Walter J. Sullivan Water Treatment Facility, located at 250 Fresh Pond Parkway in Cambridge, with new Granular Activated Carbon filter media. The filter media replacement, expected to be completed in November 2022, will strengthen the Cambridge Water Department’s ability to remove PFAS from the water supply.  

“Initial results for August showed PFAS levels trending upwards and September results are generally highest and so out of an abundance of caution, the Cambridge Water Department will be temporarily switching to MWRA water to eliminate  potential health effects from PFAS levels above the Massachusetts Department of Environmental Protection (MassDEP) regulatory standard,” said Sam Corda, Managing Director of the Cambridge Water Department. “Cambridge’s temporary use of MWRA water will continue until we replace filters with new Granular Activated Carbon filter media in our treatment plant. Replacing the filter media will ensure that our PFAS levels will be reliably and consistently below the MassDEP regulatory standard in the short and long term.” 

Cambridge water comes from the Stony Brook Watershed, nested in the Charles River Basin, in the towns of Lincoln, Lexington, Weston, and the City of Waltham. The water makes its way by gravity through tributaries, reservoirs, and pipes to Fresh Pond in Cambridge, where it is pumped into the Walter J. Sullivan Purification Facility for treatment. Finally, the finished water is pumped to and stored in the underground Payson Park Reservoir in Belmont, where it is fed by gravity to the residents and businesses of Cambridge. 

“Massachusetts has some of the strictest PFAS standards in the country, and the Cambridge Water Department is committed to maintaining and supplying high-quality water to our community,” said Owen O’Riordan, Acting City Manager. “We have decided to temporarily switch to MWRA water until the Cambridge Water Department replaces the existing filter media with new Granulated Activated Carbon filter media in our Water Treatment Plant. Unfortunately, the replacement process is taking longer due to supply chain issues, and our temporary switch to MWRA water reflects our commitment to providing all residents with a safe drinking water supply, especially those sensitive subgroups such as pregnant or nursing women, infants, and people with a compromised immune system who are most impacted by increased PFAS levels.” 

The temporary switch to MWRA water is expected to cost approximately $2 million per month. 

Like many public water supply operators, the City has been aware of the emergence of PFAS as contaminants of concern in recent years. The MassDEP standard for the level of PFAS in public drinking water is 20 nanograms per liter (ng/l), or 20 parts per trillion (ppt) for six specific compounds called “PFAS6”. The Water Department has complied with the MassDEP regulations at all times since it started monitoring for PFAS in August 2019 and has also been proactively monitoring for PFAS in its water supply reservoirs since that time (Hobbs Brook, Stony Brook, and Fresh Pond) to stay on top of this emerging issue.  

The MassDEP promulgated a new regulation on October 2, 2020, for the six PFAS compounds designated as PFAS6. Within about a year from when this new regulation was adopted, the City tested and obtained approval from the MassDEP to replace the Granular Activated Carbon filter media in its Walter J. Sullivan Water Treatment Facility to strengthen our ability to remove PFAS from the water supply. The purchase and replacement of the Granular Activated Carbon filter media was bid out and subsequently awarded in May. The Cambridge Water Department is awaiting the formal implementation schedule from the vendor, with the anticipated start date of this work being Fall 2022. When the filter media are replaced, it is anticipated that our PFAS levels will be lower and reliably and consistently below state regulations. 

For additional information about PFAS and the Cambridge Water Department, visit