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• <br />• <br />TABLE 1.0 ANALYTICAL SUMMARY TABLE BIG FIVE DISCHARGE SAMPLES <br />Metals coneenuvtioas expressed in mtcrogrannALiter <br />Sampling Event As Cd Ca Hg Ma Pb 7as <br />1985 Phase I RI 10 48 1710 NAP 19,700 91 9770 <br />1989 Phase H RI 10 27 690 NAF 18,800 S 9100 <br />2001 CDPHE NAF 24 1500 NAF 32,200 NAF 9160 <br />2005 UOSn) 2 20 2%0 11 19,.500 16 7610 <br />State Drhddn water MCL 10 S 2 - <br />State Drinkin Water MCLG 1300 - - i5 <br />State Secondstv MCL 100 NO <br />A lade Late NEC1W 5 0.413 517 0.01- 1 1000/1493 •412 471200 <br />NAF - Not Analyzed For <br />MCL - Maximum Contamaus it Level <br />MCLG - Maamum Contaminaut Level Goal <br />NBC - No Effect Concentradow an meld concentrations at whack squatk Uk does not suffer any tosk effects <br />(1) UOS -- START contractor for EPW9.Emergency-Response Team <br />(2) WQCD - sgnaUe standards for Clear Creek Seganeat 2 <br />In the event there is infiltration into the groundwater table, the net quality could only significantly improve. <br />A current sampling of the Big 5 Tunnel discharge also follows in this Exhibit C. <br />This sampling was done over a period of time from 1985 - 2009. It becomes apparent that the reported metals <br />concentration varies widely. Rationale for this can be explained by variation in rainfall amounts preceding the <br />sampling and the concentration of that rainfall in different areas of differing mineralization. This wide variability <br />can not be attributed to active mining operations because we are not aware of any within this drainage area over this <br />period of time. <br />Tailings Impoundment Construction: <br />The impoundment and composite liner system is to be constructed on crystalline metamorphic and igneous rocks <br />with minimal hydraulic conductivity. A concrete barrier will be installed upon the up gradient face of the first earth- <br />fill terrace to minimize leachate through the structure (see Exhibit E). The natural slope, upon which the fill will <br />reside, is slightly less then 3h: Iv (f 18°). <br />Generally speaking, the Tailings Impoundment will be built up in a series of five benches utilizing an upstream <br />hydraulic placement and hydraulic classification method. A maximum of 40 square feet of new embankment face of <br />minimal height (10-12 ft. per year), built with the coarse fraction, will be formed daily giving more than adequate <br />time for consolidation and draining. A maximum slope of 1.5h: 1 v (t 33.7°) will be maintained at the embankment <br />free face. <br />Design guidance was taken in part utilizing Steven G. Vick's Planning, Design, and Analysis of Tailings Dams, <br />1990 and the US Army Corps of Engineers (USACE) Slope Stability, EM 1110-2-1902. These authoritative works <br />• are cited in many EPA design and regulatory mandates. <br />Page 15 of 35