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Sannple alluvial weU CEM-004 semi-annually and analyze for selenium, sulfate, total dissolved <br />solids, and pH. <br />For the reasons stated above, well CEM-004 should be sampled quarterly, for at least five quarters from <br />the date sampling started, and thallium should be added to the suite of analytes. <br />ADDITIONAL COMMENTS <br />Geochemical evaluation <br />On page 3-4, the statement is made that "The geochemical signature of water from monitoring well CEM- <br />001 did not change significantly following the placement of the fill in C-Pit. Furthermore, these samples <br />notable lack Ca, Mg, and K, all of which are constituents of C-Pit water." <br />Response: Ca, Mg, and K can be attenuated in the aquifer by geochemical process such as ion exchange, <br />mineral precipitation, or sorption. Their absence in well CEM-001 does not indicate unequivocally that C- <br />Pit water has not migrated to that locale, although the absence of selenium in the ground water is a <br />positive sign that supports limited hydraulic connectivity. <br />Conclusions <br />On page 4-1, reference is made that a hydraulic "connection is not evident at compliance well CEM-005." <br />Response: An insufficient number of samples been collected from CEM-005 to confidently draw that <br />conclusion. However, DRMS acknowledges that the presence of only 4 feet of water in the 400-ft deep <br />CEM-005 well is a strong indication of low hydraulic connection. <br />