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- 10 - :3.2 MINE BENCH AND MINE ENTRIES Apart from the access road, the proposed mine bench and mine entries comprise the single, most impoz•tant structure located within the landslide area. It is also located within the upper slide portion, immediately below the steep slope where most instability features have been observed recently. The mine bench will require a sizable excavation to obtain the space for the operation; a long portal cut will have to be excavated for five tentatively proposed mine entries. The entrie5j are spaced 100 feet center to center, and the total length of the bench will exceed 400 feet if all entries are constructed. The configuration of the mine bench and the location of the ', i portal cut are not known at this time (October, 1980). The analy-~ ses and recommendations of this report are based on our own ten- ~ tative design of the mine bench and the mine entries portals as it is shown on Plates 1 through 6. The design is based on the j assumption that the mine bench elevation coincides approximately I i with the bottom of the coal seam; portal cuts have been designed .I so that their height does not exceed 15 feet. Topographic, geologic, and hydrologic conditions are shows in profiles along individual entries, Plates 2 - 6. The profiles show the probable boundary between the soils of the slide deposit: and intact bedrock; parts of the tunnels south of this boundary will be driven in soils while tunnel portions north of the bound- ary should reach coal. The profiles also show where the ground water level was measured on October 8, 1980 in individual piezo- meters and borings located close to the profile. - The profiles show that both entries 1 and 5 are located in unfavorable topographic conditions as they approach the steep slope above. the relativelq flat natural bench. Entry 5 is lo- I it • I I i I I .,w,ro~,omw,urc..c