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C~ <br />• <br />SCOPE <br />This report presents the results of our investigation and analysis <br />of the stability of pit wall slopes for the proposed expansion of the Y,err <br />Coal tgine located near Walden, Colorado. Based on the physical charac- <br />teristics determined by the field and laboratory investigation, an evalua- <br />tion of the proposed mine pit slopes was made to determine the stability <br />of the slopes during the mining sequence. The mine plans, general con- <br />figuration of the slopes, location and size of benches, and the mining <br />sequence were established by Kerr Coal company engineers. The field drill- <br />ing operation was supervised by Kerr Coal company geologists. Sampling <br />was performed to aid our analysis of the various soils and bedrock in <br />addition to developing information for evaluation of the overall coal re- <br />serves available. <br />SITE CONDITIONS <br />The Kerr Coal Mine is located about 9 miles east of Walden, Colorado. <br />The mine and expansion include portions of Sections 25, 26, 35, T. 9N, <br />R. 78W and portions of Sec. 3, T. 8N, R. 78W, Jackson County, Colorado. At <br />the time of our original consultation on this project the mine was in opera- <br />tion in the northern portions of Section 35. The existing mine procedure <br />is an open pit mining method with the. west wall of the pit established by <br />the dip of the sedimentary formations within the area. Coal is removed <br />parallel to the west wall. The west wall extended to heights as much as <br />200 feet with no benches. The angle of this slope ranged from 40 to 50 <br />• <br />