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Cresson Project Hvdrogeochemistry AdrianBrown <br />portions of the surrounding lower - permeability Precambrian rockmass, and then is drained from the <br />regional ground water system via the Carlton Tunnel <br />A quantitative model of the District hydrology has been created for the purpose of allowing analysis of <br />potential hydrologic impacts due to mining within the District (Attachment 3). <br />The quantitative model was created as follows: <br />• Surface topography derived from recent contouring on a 500 foot grid spacing. <br />• Twenty -two vertical layers created, each up to 250 feet thick, extending to 5,500 feet below the <br />topographic surface. <br />• Hydraulic conductivity applied to all 60,000 model cells based on geology and measured values <br />where available. <br />• Surface infiltration applied to the entire model at a rate of 6 inches per year. <br />• Carlton Tunnel installed as a drain at approximately 3,500 feet below the topographic surface (at <br />elevation approximately 7,000 feet msl). <br />The model was calibrated against the observed piezometric head information presented in Attachment 1, <br />the flow from the Carlton Tunnel, and the (lack of) ground water -fed flow in the streams overlying the <br />Diatreme. Results of the model are presented in Plate 13 for MLE2, post - closure. <br />2.6 Potential Hydrologic Impact <br />2.6.1 MLE2 Mining Activities <br />MLE2 comprises the following activities (facility locations shown on Plate 2): <br />• Mining of approximately 530 million additional total tons of ROM rock from the Main Cresson <br />and South Cresson portions of the Main Cresson Mine area, Globe Hill and Schist Island <br />portions of the North Cresson Mine area, and WHEX portion of the East Cresson Mine area. <br />• Placement of approximately 940 million tons of overburden in the SGOSA, the ECOSA, and use <br />as backfill in the Main Cresson, East Cresson, and North Cresson Mine areas. <br />• Placement of approximately 220 million tons of ore on the SGVLF for cyanide leaching to <br />remove gold and silver from the ore. <br />• Milling of 11 million tons of higher grade ore and placement of ground product from the mill <br />that has been agglomerated with Portland cement on the AGVLF and SGVLF for final leaching. <br />2.6.2 Surface Water Flow Potential Impact <br />Surface water flow potential impact due to MLE2 activities will be as follows: <br />1. During MLE2 Operations. Mine facilities will encroach on parts of the catchments of Grassy <br />Valley, Cripple Creek, Squaw Gulch, and Arequa Gulch. Little or no surface water is expected to <br />flow from the facilities to the drainages during operation, resulting in a reduction of spring <br />1385L.20120125 11 <br />