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10 <br /> 3.2 MINE BENCH AND MINE ENTRIES <br />1 ~ <br />Apart from the access road, the proposed mine bench and <br />' mine entries comprise the single, most important structure <br /> located within the landslide area. It is also located within the <br />' upper slide portion, immediately below the steep slope where most <br /> instability features have been observed recently. <br />' The mine bench will require a sizable excavation to obtain <br /> the space for the operation; a long portal cut will have to be <br />' excavated for five tentatively proposed mine entries. The entries <br /> are spaced 100 feet center to. center, and the total length of the <br /> bench will exceed 400 feet if all entries are constructed. <br />1 The configuration of the mine bench and the location of the <br /> portal cut are not known at this time (October, 1980). The analy- <br />' ses and recommendations of this report are based on our own ten- <br /> tative design of the mine bench and the mine entries portals as <br />' it is shown on Plates 1 through 6. The design is based on the <br />h <br />h <br />i <br />i <br />h <br />l <br />i <br />i <br />l <br /> on t <br />assumpt <br />at t <br />e m <br />ne benc <br />e <br />evat <br />on coincides approx <br />mate <br />y <br /> with the bottom of the coal seam; portal cuts have been designed <br />' so that their height does not exceed 15 feet. <br />' Topographic, geologic, and hydrologic conditions are shown <br /> in profiles along individual entries, Plates 2 - 6. The profiles <br />' show the probable boundary between the soils of the slide deposit <br /> and intact bedrock; parts of the tunnels south of this boundary <br /> will be driven in soils while tunnel portions north of the bound- <br /> ary should reach coal. The profiles also show where the ground <br /> water level was measured on October 8, 1980 in individual piezo- <br />d bori <br />e to the <br />rofile <br />t <br />s l <br />t <br />d <br />l <br /> p <br />. <br />me <br />ers an <br />ng <br />oca <br />e <br />c <br />os <br />' The profiles show that both entries 1 and 5 are located in <br /> unfavorable topographic conditions as they approach the steep <br />' slope above the relatively flat natural bench. Entry 5 is lo- <br />' <br /> ow+~ro.o conwuw, ec <br />