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1100318 R0T0 0811 JRW1 45 <br />rainfall and decay of variable rates of groundwater levels with time. This rapid response to <br />rainfall and decay of water levels indicates that groundwater levels resulting from older <br />antecedent rain events, such as from months prior, likely did not cause a significant rise in <br />groundwater levels and did not cause or contribute to the Pikeview Landslide. <br />6.4 Failure Along Bedding in the Manitou Formation <br />Prior investigators have expressed concern that failure of the west quarry slope could occur <br />along bedding planes in the Manitou Limestone.66, 67 Based on Exponent’s geologic mapping <br />and subsurface exploration, the December 2, 2008 failure was not along bedding within the <br />Manitou Formation. Therefore, failure along bedding on the west quarry slope is not considered <br />the cause of the December 2, 2008 landslide. <br />6.5 Over Excavation and Placement of Fill on the West Slope <br />As discussed in Section 5.3.2, the effect of the fill placement into an area of over excavation on <br />the west slope is considered to be insignificant on the slope stability particularly when compared <br />to the significant effect from the presence of the clay bed. Therefore, over excavation and <br />placement of fill on the west quarry slope is not considered the cause of the December 2, 2008 <br />landslide. <br />6.6 Fracturing of Bedrock from Blasting (a.k.a. “Overshoot”) <br />As discussed in Sections 5.2.3 and 5.3.1.3, the depth of rock fracturing below mined material is <br />approximately 4.5 feet. As discussed in Section 5.3.2, the effect of the blasting is minimal on <br />the calculated stability factors of safety and is insignificant on the slope stability especially <br />when compared to the substantially greater effects of the clay bed on the slope stability. <br />Therefore, the effects of blasting on un-mined rock did not cause or significantly contribute to <br />the Pikeview Landslide. <br /> <br />66 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 />67 State of Colorado, Colorado Geological Survey, Quarry Wall Rockslide at Pike View Mine – Summary Report, <br />January 7, 2009 (Appendix 48)