Unregulated Contaminant Monitoring Rule (UCMR3)

As part of the UCMR3 program, WSSC collected and analyzed four sets of quarterly samples between July 2013 and April 2014.  After fulfilling EPA’s requirements, bi-county legislation extended sampling until December 2017. Samples were collected from finished water from both of our water treatment plants as well as two distribution system sites representing the WSSC system locations furthest from the plants. Voluntary source water samples were also collected. The detected contaminants of the UCMR3 sampling are listed in this table.

Only 8 of the 28 tested contaminants were detected, and all detections were at low levels (parts per billion range).* Perfluorinated compounds and volatile organic compounds analyzed in the UCMR3 monitoring were not detected in our treated drinking water. The EPA has not established maximum contaminant levels (MCL) for these unregulated contaminants, and the human health effects of these contaminants at the levels they were found is unclear.  In the absence of MCLs and health standards, published guidance or health reference levels from the EPA are listed in the table (attached as pdf) as a point of comparison.

WSSC is now participating in the U.S. EPA’s fourth round of the Unregulated Contaminant Monitoring Rule (UCMR4).  

*Parts Per Billion (ppb) = Half of a teaspoon of water in an Olympic-sized swimming pool would be about one part per billion. Also, the equivalent of one minute in 2,000 years, or one penny in $10 million.


MCL – Maximum Contaminant Level –  “The maximum permissible level of a contaminant in water which is delivered to any user of a public water system."(EPA)
MCLG – Maximum Contaminant Level Goal – “The level of a contaminant in drinking water below which there is no known or expected risk to health.” (EPA)

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