Laserfiche WebLink
1100318 R0T0 0811 JRW1 44 <br />Therefore, backfilling Area H was occurring according to the requirements established in the <br />1994 Amendment and was not the cause or a contributing factor to Pikeview Landslide. <br />6.2 Over Steepening & Poor Rock Quality of the Highwall <br />Slope <br />Over steeping of the highwall slope and poor rock quality of the highwall slope are present in <br />large areas of the Pikeview Quarry and have been identified as a potential destabilizing factor at <br />the Pikeview Quarry.62 The most conspicuous example is the north end of the west wall. This <br />slope (“Kiewit Cliffs”) has been stable for decades and not experienced a mass failure, such as <br />the Pikeview Landslide. The north end of the west wall contains Manitou Formation limestone <br />similar to that in the area of the slope that failed in the Pikeview Landslide. The conclusion <br />from this performance is that over steepening and poor rock quality of the highwall slope have <br />not resulted in slope failures at the Pikeview Quarry similar to the Pikeview Landslide. Rather, <br />the otherwise good slope stability experienced at Pikeview Quarry indicates that in the absence <br />of a clay bed, the slopes are stable. Therefore, over steepening and poor rock quality are not <br />considered the cause or a contributing factor to the Pikeview Landslide. <br />6.3 Rainfall/High Groundwater <br />Rainfall and potentially high groundwater are common causes of landslides, and these factors <br />have been postulated as a potential cause of the Pikeview Landslide.63, 64, 65 At the time of <br />initiation of the Pikeview Landslide, the daily antecedent rainfall had been minimal as seen in <br />Appendix 45. Based on the running total data for 7, 28, 60, 90, and 120 days, no significant <br />rainfall maxima were present as of December 2, 2008. The combined groundwater and rain data <br />contained in Appendix 44 indicates a rapid response of the Area H piezometers, P-2, and P-1 to <br /> <br />62 J. Davidson, United States Department of Labor, Mine Safety and Health Administration, Technical Support, <br />Slope Stability Evaluation, Pikeview Quarry – (ID No 05-1443), September 17, 1986 (Appendix 49) <br />63 CTL Thompson, Slope Stability Evaluation, Pikeview Quarry, Castle Concrete, Colorado Springs, Colorado <br />Springs, May 19, 2009 (Appendix 50) <br />64 CTL Thompson, DRAFT 2010 Mined Land Reclamation Plan Amendment No. 4, Pikeview Quarry (A.K.A. <br />Castle Pit), Permit No. M-1977-211, June 30, 2010 (Appendix 51) <br />65 State of Colorado, Colorado Geological Survey, Review of Slope Stability Evaluation Pike View Quarry, <br />September 10, 2009 (Appendix 52)