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1100318 R0T0 0811 JRW1 30 <br />Mining Plan. This buttress was comprised of two bedrock materials. First, <br />the upper material was the Manitou Formation (Om) and was mined and <br />removed as part of the approved Mining Plan. The lower material was <br />comprised of the basal Manitou Formation (Omb) overlying the Sawatch <br />Formation. The basal Manitou Formation (Omb) reflects a transition from <br />clastic (sand, silt and clay) sedimentation to carbonate-dominated <br />sedimentation (the transition to relatively pure limestone is coincident with <br />the basal Manitou/Manitou Formation contact). The basal Manitou <br />Formation (Omb) is therefore heterogeneous and discontinuous in character <br />and overall represents a relatively weak stratigraphic interval within the <br />bedrock. The lowermost 10 feet of the unit in particular is of poor quality, <br />and contains intervals of fractured and brecciated rock. This relative <br />weakness is quantified by laboratory testing presented and discussed in <br />Section 5.2.4. During the excavation of Area H, basal Manitou Formation <br />(Omb) formed the remaining buttress between the underlying and previously <br />unknown clay beds and the ground surface. As mining progressed <br />substantively according to the approved Mining Plan, a critical portion of this <br />buttress was removed and the Pikeview Landslide occurred. <br /> Detailed logging of the core borings indicates that the geologic units <br />overlying the Sawatch Formation do not contain any other laterally extensive <br />planes of weakness that could have caused the movement of the landslide <br />over such a large slope area. <br /> Exposures of bedrock conditions on the floor of Area H in Trenches TR-2 <br />and TR-3 indicate that the quarrying blasting operations resulted in pervasive <br />fracturing of the substrate to a depth of at least 4 to 5 feet below the base of <br />Area H (a.k.a. “overshoot” described in Section 5.2.2.2). This fracturing is <br />standard for this mining technique and rock type. This condition did not <br />cause or significantly contribute to the Pikeview Landslide. <br /> Hollow stem auger borings EXB-1 through EXB-3 indicate that quarry <br />personnel placed as much as 50 feet of fill in the southern end of Area H <br />prior to extending the excavation to the north. The geometry of the fill