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Site Hvdrozeology <br />Ground water flow through the Arkansas Valley is envisioned to primarily occur through the <br />glacial and alluvial deposits which overlay the bedrock formations. East -west ground water <br />flow through the Precambrian bedrock formations and across the Mosquito Fault is not <br />considered a primary pathway because: <br />The Mosquito Fault has been documented to be a significant barrier to ground water <br />flow; and <br />The Precambrian Idaho Springs Formation and Silver Plume Granite are considered to <br />be of low permeability. ' <br />Mosquito Fault <br />Empirical data from the historic mine records, corroborated by site knowledge, indicate that <br />the Mosquito Fault in the Arkansas Valley is somewhat permeable in the direction along its <br />strike (north - south), but relatively impermeable perpendicular to its strike (east - west). The <br />accepted morphology of the fault (clay and gouge filled) gives credence to this assertion. <br />Data which support the impermeable nature of the Mosquito Fault include: 1) historical mine <br />records from the construction of the Phillipson Level portal tunnel which was driven eastward <br />across the fault zone in the late 1920's and early 1930's, and 2) recent data on the ground <br />water conditions encountered in an exploratory water supply well drilled on the west side of <br />the fault. <br />Phillipson Level Tunnel <br />The Phillipson Tunnel was an underground access tunnel driven in the late 1920's and early <br />1930's. The tunnel, located to the west of the Climax open pit, was driven through <br />approximately 2,000 feet of Paleozoic sedimentary rocks before intersecting the Mosquito <br />Fault and Precambrian rocks to the east. <br />Documentation of ground conditions and ground water inflow into the tunnel provide a record <br />of the hydrogeologic conditions as the tunnel crossed the Mosquito Fault. A summary of the <br />