2012-02-28_REVISION - M1980244 (90)

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Cresson Project Hvdroaeochemistry AdrianBrown 1. INTRODUCTION The Cripple Creek Mining District ( "District ") is located in a seven square mile volcanic structure known as the Cripple Creek diatreme ( "Diatreme ") in the central Colorado Rocky Mountains near the Cripple Creek and Victor (Plate 1). Gold has been produced from this District for more than a century, primarily from underground mines operated between 1890 and 1940. To facilitate underground mining, the entire District was dewatered by a series of historic tunnels constructed between the late 1800s and 1942. In 1993 large -scale mining was restarted in the District using surface mining methods, with overburden storage near the mines, and ore processing in a valley leach facility ( "VLF ") at the south end of the District (the "Cresson Project "). Cripple Creek & Victor Gold Mining Company ( "CC &V ") is proposing a second mine life extension ( "MLE2 "), comprising the following: • Mining of approximately 530 million additional total tons of run -of -mine ( "ROM ") rock from the Main Cresson and South Cresson portions of the Main Cresson Mine area , Globe Hill and Schist Island portions of the North Cresson Mine area, and WHEX (Wildhorse Extension) portion of the East Cresson Mine area. • Placement of approximately 940 million tons of overburden in the Squaw Gulch Overburden Storage Area ( "SGOSA "), the East Cresson Overburden Storage Area ( "ECOSA "), and use as backfill in the Main Cresson, East Cresson, and North Cresson Mine areas. • Placement of approximately 220 million tons of ore on the Squaw Gulch Valley Leach Facility ( "SGVLF ") for cyanide leaching to recover gold and silver from the ore. • Milling of 11 million tons of higher grade ore and placement of product from the mill that has been agglomerated with Portland cement on the Arequa Gulch Valley Leach Facility ( "AGVLF ") and SGVLF for final leaching. The locations of the proposed MLE2 operations are presented in Plate 2. The proposed MLE2 activities will expand the amount of material that will be mined in the Cresson Project. At the completion of MLE2, the following will have been mined and processed (Table 1): • Higher Grade Ore • Ore • Overburden • Total Material approximately 11 million tons approximately 619 million tons approximately 975 million tons approximately 1,605 million tons The proposed extension will take place within the District. The geohydrology and geochemistry of the District have previously been evaluated in detail in submissions to the State of Colorado, Division of Reclamation, Mining and Safety, most recently in support of Amendment No. 9 of CC &V's Mine Permit (CC &V, 2008). This report presents a detailed update of the system -wide understanding of the regional hydrologic and geochemical processes that control the quantity and quality of water that infiltrates through the elements 1385L.20120125 1