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11. The Operator submitted Amendment # 1 to permit number M-1977-211 to the <br />Division in June, 1994. Amendment 41 was approved by the Division on August 31, 1994. <br />Amendment 41 increased the Area H excavation hole to 150 feet and limited the disturbance <br />of the existing affected area to no more than 25 percent. Generally, Area H delineates the <br />limits of the excavation hole created at the base of the east facing back wall (consisting of the <br />high walls and benches described in ¶ 2 above) of the quarry. <br />12. The site is located in a geologically structurally complex zone where five <br />faults are mapped near, and within, the mine boundary. The site geology consists primarily <br />of Manitou limestone, with Saguache sandstone underlying, and Pikes Peak granite forming <br />the base. Complex faulting resulted in the strata being uplifted and tilted at a. steep angle. At <br />the west boundary of the quarry the strata dips east at about 70 to 80 degrees,. Erosion over <br />many millennia has exposed the Manitou Limestone outcrop, which is the aggregate being <br />mined. The CGS issued a report ("CGS Report") by Jon White, and TC Wait, on January 7, <br />2009, drafted at the Division's request and after CGS engineering geologists visited the site <br />and reviewed the 1994 Mine Permit document, a 1986 slope stability evaluation by MSHA <br />("1986 Slope Stability Memo"), and a 2001 Decision Notice by the National Forest Service <br />that permitted the removal of granite on forest lands above the quarry wall. The CGS Report <br />states "[b]rittle deformation features are abundant within the Precambrian granite, sandstone, <br />and limestone outcrops in the vicinity of the fault zone (e.g. slickensides, altered zones, <br />fractures, and fault gouge), which indicate additional numerous, small unmapped fault and <br />shear zones within the mine area." The CGS Report on p. 10 concludes that the quarry <br />rockmass is inherently weak "caused by the abundant discontinuities related to the Rampart <br />range fault zone." <br />13. The Pike View Quarry has a history of slope failures and rockslides. Two <br />slides occurred in the 1970's where rock slabs 20-30 feet thick and hundreds of thousands of <br />tons in size slipped. MSHA concluded in the September 17, 1986 Slope Stability Memo that <br />'jiff the final west quarry wall is excavated in the steeply dipping limestone beds as currently <br />practiced, an eventual total failure of the entire west wall can be expected. The combination <br />of undercut, steeply dipping beds; bedding plane separations; and freeze-thaw cycles can be <br />expected to produce this eventual quarry wall failure." <br />14. The Pike View Quarry also had a slide in 1993 near the area of the 2008 rock <br />slide. In the 1993 slide, a 25-foot thick rock slab weighing about 500 thousand tons, slid <br />400-500.feet down the slope. The CGS Report quotes the 2001 decision notice from the <br />USFS authorizing the Operator to lay back the granite slope above the steep quarry walls on <br />forest lands. The notice states "The layback of the top cut is proposed as a possible solution <br />to stabilizing the high wall ... of the current steep slopes." CGS Report p. 6. <br />15. The CGS Report on p. 7 details the contributing factors for the west quarry <br />wall slope failure.. The third contributing factor is described as: <br />From examination of earlier aerial photography, the slope of the west wall of <br />[the quarry] was loaded with spoils from the active excavation of a large bench <br />in weathered granite that was part of the special use permit by USFS in 2001. <br />Continental Materials <br />Pike View Quarry, M-1977-211 <br />MV-2009-012