Frequent Questions

Public water systems (PWSs) are required to report the highest contaminant level used to determine compliance with a National Primary Drinking Water Regulation (NPDWR) and also the range of the detected levels in their annual Consumer Confidence Report (C

When the PWS determines compliance with the NPDWR by calculating a running annual average of all samples taken at a sampling point, the PWS must include the highest average of the sampling point (as reported to the state for compliance purposes) and the range of levels detected. If compliance is determined by a running annual average of all samples at all sampling points, the PWS must include the highest average of the contaminant levels detected and the range of detected levels (40 CFR 141.153(d)(4)(iv)(B) and (C)).
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