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Sent By: CEMEX; 3038232188; Nov-1 <br />Erica Crosby <br />Divialon of Minei•ats and Geology <br />04 10:03pM; Page 3/4 <br />Asge 2 of 3 <br />November 1; 2004 <br />(including measured strikes and dips by the USGS) along wkh borehole logs of nearby bedrock <br />water wells from the livision of Water Resources, State Engliteers Office. The attached base <br />map and cross section A-A' indicate that A-ph waterlIl~lC be >~ suitable monitoring/oompliance <br />polnt but this finding In not conclusive. <br />The water surlaoe elevation In A-pit fs 14 test bwer than the Uvater surface elevation in Gpft as <br />of Otrtober 18; 2004. A-pft water is topographk~liy downgradient of Gpit water. C-pk was <br />mined to recover the Fort. Hays Umestone while A-pit was mined to recover the Smokey Hiu <br />Shale (both.aee nlemt>grs ofthe Niobrara Formation). The Sitlokey Hill Shale overlies the Fort <br />Bays ltinestolte. 'if C-pit water was entering ttre Fort Hays limestone ft would be difficuR tv <br />iti'iagihe watet:movirtg up the stratigraphic column given the ininimeJ hydraulic head. Some <br />Smokey Hitl Shale is exposed in C-pit (removed as overburrfelt to get to the limestone) and <br />these beds of Smokay Hilt Shale may connect to the bottomof A-ptt however this fs not known <br />(the bedding (n the vidnlty of C-plt and A-pit dips approximatisly 6°-8° east-southeast). <br />[)ue to the unCeltainty about the degree of hydraulic oonnecion between Gpft and A-pit, <br />Centex is proposing to install two new ground water monitoring wells located as shown on the <br />base map. The walls will be screened in the FoR Hays Limestone and are proposed to be used <br />as monitoring and compliance points. <br />1'he off-site Vveli coinpieted in the Qakota Formation (which is not owned or oomrolled by <br />Comex) will cntttihue to be monitored by Cemez txrt will not be designated as either a <br />monitoring or coritpliance point. P-either Comex nor the Div~ion want a permit oontlfttotr that <br />cannot be asgessed without the permission of a third party riot bound by the DMG's regulations. <br />The toAowing summarizes proposed monitoring and compliance points: <br />Gpit water -Source (C-pit is neither a monitoring nor a compliance <br />point) <br />A-pit water -Surface water monitoring point <br />New monitoring well - Downgradient monitoring point <br />.New compliance wall - Downgradient compliance point <br />. Off-site Dakota Fonnatfon well -Regional groundwafler qualfty tndioator <br />In previous disiktssions with the DNision, Comex proposedmonftoring St. Vrain Creek and the <br />BoUlder.Feeiier Carta} water to establish some baseline water qualRy date. This is no longer <br />deemed necessary because of the plans proposed herein. <br />Cetngz will submit aground water mitlgatlon plan to the Oivision if an excaedanoe of any of the <br />five water qualky parameters are observed in three oerlsecjrtive monitoring events. The plan <br />wlli be subrrstted to the Division wfthir130 days of the trigger event. The plan w)tl kfentify the <br />source(s) ofthe ex~edanoe and the proposed remedy to compy with the applicable standards. <br />