2014-04-14_PERMIT FILE - C1996083 (2)

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Huddleaoe•BeM Based upon the available data, the following parameters were utilized for the compacted gob. • y = 104.6 pcf • c' = 0 psf • 0' = 34° Native Foundation Soils In general, the soil parameters utilized for the native foundation soils have been fairly consistent within the reviewed documentation. As a result, based upon the available data, the following parameters were utilized for the native foundation soils. • y = 125 pcf • c' = 100 psf • 0' = 34° Uncompacted Gob Based upon information in the December 5, 2013 Buckhorn report, the following parameters were utilized for the uncompacted gob. • y = 96.2 pcf • c' =0psf • 0' = 34° 3.3 Piezometric Surface In general, based upon our review of the available data, HBET does not believe that there is a free water surface, such as a static groundwater table, within the gob pile. However, the pore pressures recorded by the vibrating wire piezometers are not zero. As a result, the pore pressure data from the piezometers was used to generate a piezometric surface consistent with that data in order to evaluate the impacts of the pore pressures on the stability of the gob. HBET utilized data from VWP -05, VWP -06, and VWP -08 to generate the piezometric surface. It is important to note that VWP -09 is at a similar elevation to VWP -05; however, the pore pressures in VWP -09 are lower than in VWP -05 making our use of the VWP -05 data conservative. Beyond the limits of the available piezometer data, HBET assumed a phreatic surface for the area of gob pile #2 below VWP -05. Beyond the toe, the phreatic surface was assumed to intersect and follow the ground surface. This is a conservative assumption. 3.4 Results Based upon DRMS Rule 4.10.4(2), a minimum Factor -of- Safety (FS) of 1.5 is required for the analyses to indicate a stable condition. X \2008 ALL PROJECTS,00489 - JE Stovet Associates Ine.00499-OW3 Bowie.Mine%200 - GWO0499 -0003 R032114RI doe 4