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<br />' <br /> A few large planar joint surfaces representing the primary joint set have been exposed as a <br /> result of wedges of overlying rock sliding on the joints. These surfaces have been as large as <br />' approximately 100 ft long by 60 ft high striking approximately parallel with the slope, and <br /> dipping approximately perpendicular to and out of (south) the north side. In response to such <br /> occurrences with a south to north mining operation (south-facing slopes with south dipping, <br />' daylighting joints), CAMAS modified mining in the North Quarry to an east to west operation <br /> to create interim active mining slopes that are more east-facing and, therefore, more stable <br /> with respec[ to the prevailing south dipping joints in this area. <br /> <br /> Based on the conditions observed in 1995 and 1996, the shallow rock mass in the northeast <br /> part of the North Quarry was [entatively classified as "poor" in terms of the previously <br />' established baseline conditions. This classifiea[ion was based prirarily on the adverse <br /> orientation of the primary joint set along foliation that dips out of the slope (.daylights). <br /> Additionally, the rock mass within the weathered zone was classified as "poor" based <br />i ' primarily on the low unconfined compressive strength of the shallow parent rock material. <br /> Further development of the North Quarry during 1998 was generally below the shallow <br />' weathered zone in better quality, "competent" rock mass. <br /> Despite these more favorable baseline conditions, slopes in the North Quarry are presently <br /> being excavated at an inclination of approximately 1H:1V or flatter, generally with only 40 ft <br />' highwalls. CAMAS is developing shorter highwalls than the default 80 ft highwall by 80 ft <br /> bench to provide improved safety conditions in the mine and allow observation of lower <br /> highwall exposures before deciding to excavate higher ones, although not reyuired to do so. <br /> At present, work in the Notch Quarry is not at the ultimate limit of the planned excavation, <br />' therefore, precision blasting techniques are not presently being used. When excavation <br />occurs at the proposed final quarry walls and if the slopes are to be excavated with an overall <br /> inclination exceeding 1H:1V, precision blasting techniques are planned. <br />1 <br /> <br />i <br /> <br /> <br /> <br /> <br />' G.~PROIECTS\(0.00 Mornson QuurylW2\Amual Report Geov~Nixal ApdeMUm~1998\98rp~ markup.dac Page 9 <br />