Hexavalent Chromium

As part of required EPA testing for all water systems serving 10,000 or more people in the United States, the Shrewsbury Water Department conducted UCMR-2 (Unregulated Contaminants Monitoring Rule Round 2) testing in 2013-2014.

hex chrome

Hexavalent Chromium Molecule

Detecting Hexavalent Chromium

A wide range of substances were tested, hexavalent chromium also known as Chromium-6 was included on the list. Our system registered results between 3-4 parts per billion (ppb) well under the EPA and MassDEP Departments standard of 100 ppb for total chromium which adds together trivalent chromium (Chromium-3) and hexavalent chromium (Chromium-6). 

A report came out in 2015 by the Environmental Working Group (EWG) an environmental lobbying group out of Washington, DC headed by activist Ken Cook. This report using the EPA and State databases listed Danvers, Shrewsbury, and a third community on Cape Cod as the three highest in the State for hexavalent chromium.

The Town through the Board of Selectmen took a proactive approach, which continues today to track down the source, to see what wells were affected, identify the feasibility of treatment methods and other alternatives. Since no New England laboratories are able to test for hexavalent chromium to the low levels that were required, we contacted the laboratory used by the EPA for the UCMR-2 testing, Eurofins in California to run our samples. We identified three wells, Home Farm 6-1, 6-3 and 6-4 out of eight wells as having low levels in their supplies.


Treating Hexavalent Chromium

The Town developed at two prong strategy of minimizing usage of the two main wells with the highest levels affected and establish a new well away from the property on Sewall Street. This well would replace previous well source, Sewall #5, which was decommissioned for diminishing yield in a more favorable location. Concurrently, the biological treatment process was pilot tested onsite and showed favorable results but needed to be cut short due to monitoring well flow issues. For FY 2020, the Town will be installing test wells to the north of the existing Treatment Plant to begin the process of establishing a replacement well to take the place of the volume of Home Farm 6-1 and 6-3. With the new wells in place, we believe hexavalent chromium should be between 1-2 ppb and in all probability below 1 ppb. The latest reading for finished water for hex chrome was 3.5 ppb on July 22, 2019. The Town continues to monitor hex chrome levels and evaluate available options for treatment and mitigation.

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