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• The volcanic diatreme that was emplaced into the Pikes Peak granite formed an <br />inverted cone of highly fractured volcanic rocks. The surrounding granite and <br />gneiss is relatively impervious, except in the immediate vicinity of the diatreme, <br />where it was fractured during the volcanic episodes. As a result, the brecciated <br />rock within the diatreme filled with water, receiving recharge from precipitation <br />at the surface and storing it as ground water in the faults, fractures, veins, joint <br />structures, and underground workings. The relatively impermeable Pikes Peak <br />granite acted to hold this water in place within the diatreme, although locally it <br />may have flowed via springs at the boundary. A series of drainage tunnels were <br />created in the early 1900s as underground mining progressed in the area. These <br />tunnels drained the diatreme and lowered the regional ground water system from <br />the original elevation of approximately 9,500 feet amsl to a level of <br />approximately 7,000 feet amsl. The regional ground water system is intersected <br />by the Carlton Tunnel. <br />Recharge to the ground water system occurs by infiltration of precipitation in the <br />spring, summer, and fall months. Infiltrating water moves vertically downward <br />through the unsaturated portion of the system either through the brecciated <br />• diatreme country rock, through subvertical fractures, through mined voids created <br />during historic underground mining, or a combination of these pathways. <br />Surface manifestation of the historical dewatering effects is apparent throughout <br />the District. Streams in the central and southern portions of the diatreme tend to <br />be ephemeral in nature, as most of the precipitation and snowmelt infiltrates into <br />the porous rock and migrates downward. Exploration drill holes and development <br />wells drilled within the diatreme tend to be dry or have low yields. Present mining <br />by CC&V has not encountered significant ground water flow other than local <br />perched aquifers that tend to contain limited amounts of water. Ground water <br />monitoring shows that the depth to ground water beneath mine facilities is <br />generally more than several hundred feet. <br />As shown on Drawing G-1, no significant ground water production occurs in the <br />area of the diatreme (i.e., ground water is not developed for use). The ground <br />water system within the diatreme is distinct from that in areas surrounding the <br />diatreme. <br /> <br />Cripple Creek & Victor Gold Mining Company <br />Cresson Project Mine Life Extension <br />4-12