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Table 1 - Soil Properties <br />Description <br />Max dry <br />Saturated <br />Cohesion <br />Internal <br />density <br />Density <br />(psf) <br />Friction <br />(pcf) <br />(pcf) <br />Angle <br />Overburden <br />110 <br />131 <br />150 <br />22 <br />Sand and Gravel <br />110 <br />131 <br />0 <br />35 <br />Weathered <br />125 <br />141 <br />100 <br />18 <br />Bedrock <br />Stable Bedrock <br />125 <br />141 <br />2000 <br />20 <br />Bentonite Slurry <br />NA <br />100 <br />0 <br />0 <br />Wall <br />DESIGN ANALYSIS AND CRITERIA <br />The proposed mining slopes were analyzed using the XSTABL v5.105a computer <br />program. XSTABL was designed to analyze the slope stability of earth embankments <br />subjected to several critical situations that may occur during the life of the embankment. <br />For this project, four cases were identified as critical during the mining operation. Static <br />and pseudo- static conditions were analyzed in each case. <br />Pseudo - static peak acceleration factors were taken from USGS information for the <br />western United States. The 2% probability of exceedance in 50 years (the most <br />conservative) was used. <br />Surface loading equivalent to an HS 20 highway load was applied adjacent to each area <br />to simulate heavy equipment loading that could be present at that location for <br />maintenance or construction activities. <br />All mining side slopes will be 3H:1V. <br />Case North — Weld County Road 6 (NORTH). The mining operation is adjacent <br />to County Road 6 on the north property line of the site. The proposed setback for <br />mining is approximately 40 feet from the ROW /Property Line. The mining depth <br />was assumed to be 32 feet in this area based on bore log information in the <br />geotechnical data. <br />Case South — South Property Line (SOUTH). The mining operation is adjacent <br />to private property with an irrigation ditch that has been rerouted around the <br />property to the west. The mining depth was assumed to be 29 feet in this area <br />based on bore log information in the geotechnical data. The proposed mining <br />setback from the ditch bank is approximately 40 feet. <br />Case East — Overhead Power Line (EAST). The mining operation is bounded <br />by overhead power lines on the east. The mining depth was assumed to be 32 <br />feet in this area based on bore log information in the geotechnical data. The <br />- Northern Colorado Constructors, Inc. — Perry Pit <br />Slope Stability A <br />Jx I' Consulting, Inc. Page /2 <br />9 <br />