Laserfiche WebLink
This memorandum references mine areas as they are differentiated in the 1994 mine <br />permit. The outline of this report is as follows: <br />Site visit observations and literature review <br />Mine geology and structural conditions <br />History of rock failures at the mine <br />Possible Rockslide Failure Mechanisms and Contributing Factors <br />Risk of Future Rock Movement <br />Conclusions and Recommended Future Actions <br />Site Visit Observations (12/11108) and Literature Review <br />CGS engineering geologists visited the site on Thursday, December 11, 2008 with <br />representatives of the mine owner and DRMS. At the time of our inspection, active mining <br />operations were suspended, and drilling and hauling equipment were idle. The site visit started <br />at the toe of the slope, then worked its way up the southern access road to the top of the slope <br />and across to the area north of the slide. The debris material is largely broken blocks of <br />limestone. The toe of the slide is approximately 1,200 feet wide and extends roughly 600 <br />vertical feet up the slope. The Mine Operator indicated that the fines pile at the southern end of <br />the toe had moved approximately 80 feet laterally, cutting off the haulage road at the toe. A fan <br />of granitic spoils is shown on aerial photographs dating back to the early 2000s near the <br />headscarp of the slide. This material was apparently being scraped off the adjacent weathered <br />granite areas and pushed onto the Area MV slope. <br />The general impression of the rockslide is that the benched west wall of the quarry (Area <br />MV) failed and the now-rubblized rockmass slumped down the slope, partially obscuring the <br />corrugated bench geometry, and partially covered the floor of the active quarry area known as <br />Area H (the hole). The rockslide occurred within dipping sedimentary rock strata and is roughly <br />triangular in shape. The scarp is about 40 feet high at the apex of the slide. At this location, the <br />landslide scarp extended to and detached at the location of a fault where dipping Sawatch <br />Sandstone is offset against weathered and grussified Pikes Peak Granite (Figure 1). Additional <br />rock movements also occurred above the main landslide scarp, evidenced by large tension <br />cracks that extend into the granitic rock above <br />2