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Oct 30 2007 7:49RM Cemex Inc. 303 823 2199 p.3 <br />Ms. Erica Crosby <br />Octob« 29, 2007 <br />Page 2 <br />CEMEX Response: CEIv1EX agrees to reaain dissolved thallzxtn and chloride on the analyte last, and <br />will continue za monitorfar fave guarterr. Tbe,Srrt guarterly rampk v~aU be taken an Oc7aber7007, <br />After five quarters, the data will be assessed, and tf appraprfate (:EMEX unll Consider proposing a <br />daffereat aaaFyte llrt and rchedula ao DRMS. <br />c. Continue to monitor the wacec level in C-Pit. <br />Agreed. <br />CEMEX Response: Lx7-TEX a~ees. <br />d. Reduce the sampling frequency for monitor well CEM-001. <br />Because of the existence of multiple parameters lvstorically exceeding regulatory <br />limits in pit water, DRMS should recommend that quarterly sampling continue <br />for at least five quartets from the date sampling started. <br />CEMEX Response: CF.tViEX agrees to rarrrpk CEM-00/ for free addationa! gumterr The ~Frrt <br />quarterly rampk will be taken in October 200.'. After fine gxaner., the data mall be assessed and of <br />appropriate CEt1~X will canraderpraparing a di~rent ramplauB rer5edxk to DR~1S. <br />e. Monitor the waters level at compliance well CEM-005 semi-abnually. <br />Agree, but if sufficient water is present in CEM-005, an attempt should be made <br />to collect a sample. <br />CEMEX Response: CEA~fEX agrees. <br />E Sample alluvial well CEM-004 semi-aaaually and analyze for selenium, <br />sulfate, total dissolved solids, and pH. <br />For the reasons stated above, well CEM-004 should be sampled quazterly, for at <br />least five quarters from the date samplittg started, and thallium should be added <br />to the suite of analytes. <br />CEMEX Response: CER~fEX agrees to rampk CF.M-004 far five addataana! guarterr and rva!l add <br />thallium to the list. The fart guasterEy sample will be taken in October 2007. After five quarters, the <br />data wall be assessed and if abprvpriate C"F.it'fBX tvi!! conraderproporang adifferent rornplrng rcheduk to <br />DRMS. <br />ADDITIONAL DRMS COMMENTS <br />g. Geochemical evaluation <br />On page 3-4, the statement is made that "The geochetnical signature of water from <br />monitoring well CEM-001 did not change significantly following the placement of <br />the fill in C-Pit. Furthermore, these samples notably lack Ca, Mg, and K, all of which <br />aze constituents of C-Pit water." <br />Response: Ca, Mg, and K can be attenuated in the aquifer by geoehemical pmcess <br />such as ion exchange, mineral precipitation, or sorption. Their absence in well CEM- <br />001 does not indicate unequivocally that C-Pit water has not migrated to that locale, <br />Draft Response to 10-5-07 Adequacy Aevitw_TR-9_RE,V2 <br />