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Pacific Southwest, Region 9

Serving: Arizona, California, Hawaii, Nevada, Pacific Islands, Tribal Nations

Unregulated Contaminant Monitoring Rule

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EPA published the revised Unregulated Contaminant Monitoring Rule (UCMR 2) on January 4, 2007. The rule is designed to help EPA determine which new contaminants should be considered for future regulation under the Safe Drinking Water Act. Community water systems serving more than 10,000 persons and a select group of smaller community water systems are required to take water samples and have them analyzed to see if specific chemical contaminants are present.

Approximately 360 California, 55 Arizona, 15 Hawaii, 10 Nevada, and a small number of water systems in Guam, Saipan, American Samoa and the Navajo Nation are required to perform UCMR 2 sampling. Water systems required to sample under the UCMR 2 are assigned a 12-month period between January, 2008 and December, 2010 to complete their monitoring. Surface water systems are required to take four quarters of samples and ground water systems are required to take two rounds of samples within the twelve month period. All data from water systems serving more than 10,000 persons must be reported electronically into EPA's electronic reporting system (SDWARS).

EPA will use the data generated by the UCMR 2 to evaluate and prioritize contaminants on the Drinking Water Contaminant Candidate List, a list of contaminants EPA is considering for possible new drinking water standards. These data help to ensure that EPA has the high quality scientific data it needs to make decisions about future drinking water standards.

Please visit EPA's national UCMR web page for additional information.

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