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Gold veins in igneous rock on the south side of Hoosier Pass and in the upper basin of the South <br /> Platte drainage are the origin of the Park County placers through thousands of years of glacial <br /> activity during the last ice age and subsequent erosion. Due to the fineness of gold at the site <br /> (0.833 fine),the gold placer has been traced to gold from North Star Mountain in the <br /> Montgomery Deadwood area in the upper reach of the basin. <br /> Past mining history shows significant gold placer deposits are found in dips or depressions in the <br /> bedrock within the permit area. Good concentrations can also be found in previous locations of <br /> the South Platte River channel. Seismic testing(2002) of the exact bedrock location shows <br /> sporadic dips and an older channel location near the west edge of the permit area. Based on <br /> seismic test results and past operations, this horizon will be targeted for placer mining. Seismic <br /> cross section locations are shown on Map C-3. Cross sections showing the bedrock to gravel <br /> contact as well as the current surface are given on Map C-3. <br /> Topsoil, overburden, and separated waste fines will be stockpiled and used to backfill the slopes <br /> of mined out areas to a 3H:1V slope during Reclamation as shown on Map F-1. It is expected <br /> that 15 to 25 feet of overburden gravel will be excavated and placed in previous pit excavations <br /> to access the lower 5-15 feet of gravel above bedrock that is known to contain high gold <br /> concentrations. In unmined areas, topsoil from 3"to 6" is salvageable and will be stockpiled as <br /> shown on Map C-2. The expected average depth of topsoil is 4.5"based on existing cuts in the <br /> permit area. To prevent erosion of topsoil and overburden stockpiles, piles will be seeded within <br /> 180 days of establishment with the rangeland seed mix or quick oats. Stockpiles will be <br /> constructed to 2.51-1:1V slopes for topsoil and overburden. <br /> Gold placer mining will occur in cuts of approximately 300 feet long by 150 feet wide with <br /> 2H:1 V side slopes to access bedrock at an average maximum depth of 30 feet. Cuts will be <br /> completed within lettered mining areas shown on Map C-2 with a general mining direction from <br /> the northwest to the southeast. Mining in each area includes: topsoil and overburden stripping, <br /> placer gold mining, and backfilling. <br /> Prior to any mining for this amendment, a berm with a minimum 8 foot height, 2H:1 V side <br /> slopes will be created along the Highway 9 ROW (right of way) for at least 600 feet around the <br /> active mining area. This will visually shield the operation from the Highway/Main Street, as well <br /> Alma Placer Mine <br /> December 2017 D-2 <br />