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.' <br />Selenium excursion <br />The possible excursion in selenium reported recently is possibly in error, not because of any <br />analytical problem but because of the analytical method. The lab report indicates selenium was <br />measured by the total selenium method. However, selenium is regulated based on dissolved <br />selenium. DMG would require that the selenium concentration meet the lowest state water <br />quality standard for selenium, which would be measured by the dissolved or potentially <br />dissolved method, depending on current CDPHE protocols. These regulations are available at <br />the CDPHE web site under Basic Standards and Methodologies for Groundwater. <br />If there is enough water from the sample in question to be filtered and retested by the dissolved <br />method, I recommend this be done. Otherwise, the C-Pit sample should be re-collected, filtered <br />in the lab, and tested via the dissolve selenium method. The lab should be encouraged to <br />report the analytical value plus the analytical error. <br />Cc: Bruce Humphries <br />Carl Mount <br />