2004-10-07_REVISION - M1999002 (2)

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• 21-s (Ewn • 21-3U (NPL) • 20-s (EWI) • 21-3a (NPL) • 21-4a (EWI) • 21-3b (NPL) • 21-4b (EWI) Silica Concentration: • 21-2 (EWI) • 20-8 (EW)) • 21-3a (NPL) • 21-3b (NPL) Boron Concentration: • 21-3a (NPL) • 21-4a (EW>7 • 29-3 (EWI) Total Alkalinity Concentration: • 28-1 (EWI) • 21-3U (NPL) • 20-s (EW)) • 21-3a (NPL) • 29-3 (EWI) • 21-3b (NPL) Fluoride Concentration: • 21-3U (NPL) • 21-4a (EWI) • 29-3 (EWI) • 21-4b (EWI) • 20-9 (EWI) In establishing the original NPLs and EWIs through technical revision TR-002, American Soda used the Dixon method to identify outliers at the upper end of the data sets. If outliers were present, they were rejected and the NPL or EWI was established at the highest detected level that was not an outlier (unless that highest detected level was below a table value standard (TVS), in which case the TVS was selected as the NPL or EWI). This practice has not been regulatorily effective; review of appendix B to TR-004 shows that numerous NPLs and EWIs have been exceeded during the production period, even though there is little reason to think that process water has contributed contaminants to the water being sampled. In other words, the natural fluctuations in ground water chemistry result in concentrations of certain constituents that aze higher than the NPLs and EWIs for those constituents. American Soda will need to establish NPLs and EWis in a way that if exceeded, it will be a rather more cleaz indication of process water influence.