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On December 11, 2015, EPA issued in the Federal Register the proposed Unregulated Contaminant Monitoring Rule (UCMR) 4. UCMR 4 requires scheduled monitoring for 30 chemical contaminants during 2018-2020 of all source water, and entry and distribution points within each Public Water System (PWS). All PWSs that serve >10,000 consumers must perform this testing, as well as 1600 smaller systems that will be selected by EPA (see Federal Register Journal).

See the EPA UCMR 4 website for additional information.