For initial compliance determination with the Radionuclides Rule, can I composite the samples from all of my wells?
No. Systems are only allowed to composite samples temporally, not spatially. Compositing: to fulfill quarterly monitoring requirements for gross alpha particle activity, radium-226, radium-228, or uranium, a system may composite up to four consecutive quarterly samples from a single entry point if analysis is done within a year of the first sample. States will treat analytical results from the composite as the average analytical result to determine compliance with the MCLs and the future monitoring frequency (40 CFR 141.26(a)(4)).
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