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1. Many smaller fresh cracks on the quarry wall and upper quarry road cut slopes are not <br />traced in the figure). We consider the major tension crack that formed as much as 100 feet <br />above the rim of the quarry, on the south side above Area MV, to be an incipient scarp above <br />the current rockslide. Pikes Peak Granite has fissured and down-dropped up to 4 vertical feet, <br />making the quarry road along the rim of the quarry impassable. With the steepness of slope, <br />the poor rock quality, some limited rock movement, and the undermining loss of support at the <br />major scarp below, it is likely that this upper rock block in Area MV, above the south side of the <br />main slide, is experiencing dilation and slow creep that will likely accelerate in the foreseeable <br />future. It is not so much a matter of 'if, but rather `when' this unstable block will fall. Tension <br />cracks and other indicators of movement were also observed above the north side of the slide. <br />In addition to the rockslide, there is a secondary risk of rockfall from the scarp areas and <br />also from the steeper areas within the slide mass. Several large blocks fell subsequent to the <br />slide from the northern end of the headscarp. Fortunately these blocks did not bounce or roll <br />very far down the slope; however, there were large blocks (roughly 8 feet in diameter or more) <br />that were observed near the toe of the slope during the site visit. <br />Mine -geology and structural conditions <br />The mine is located within the north-striking trend of the of the Rampart Range fault <br />zone that marks the tectonic boundary of the Front Range mountain uplift with erosional <br />landforms in the sedimentary strata of the Colorado Piedmont to the east. Geologically, this is a <br />structurally complex zone, where five faults are mapped by Morgan and others (2003) near, and <br />within, the mine boundary location. Movements of normal, high-angle reverse, and strike-slip <br />faults have caused a 0.8 mile-long sliver of lower Paleozoic rocks to be folded upwards and <br />structurally isolated (See Figure 2 geologic map). Subsequent Tertiary and Quaternary erosion <br />and topographic lowering of the Piedmont along and east of the fault trend has exposed this <br />Manitou Limestone (Om) outcrop, which is the aggregate resource being mined. The west <br />boundary of the quarry has steep east-dipping (mine permit mentioned dips up to 70-80 <br />degrees) Cambrian Sawatch Sandstone (Es) faulted against Precambrian Pikes Peak Granite <br />(Ypp). On the east boundary of the mine, over 6,000 feet of vertical offset has occurred where a <br />high-angle reverse fault has juxtaposed steep east-dipping lower Ordovician Manitou Limestone <br />(west) against structurally overturned Upper Cretaceous Pierre Shale (Kp) strata of the <br />downthrown block (east). <br />4