2008-04-30_REPORT - M1973021 (3)

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O TETRATECFI folding of the rock with an average dip to the west. The rock mass was defined as primarily competent with the following exceptions defined as poor: • A shear zone, 240 feet long, cross cutting highwall, striking 20 to 30 degrees • A clay filled seam, 3 to 9 inches thick, dipping out of the slope 2005 GEOTECHNICAL ADDENDUM The 2005 geotechnical addendum indicated mining in the North Quarry was completed on north, east, and west benches to approximately elevation 6,360. The mine slopes were recorded as 40 feet highwalls with 40 to 50 feet benches. The rock described in the report was granitic gneiss with mafic and felsic intrusions (felsic dikes and pegmatites). Joints in the rock mass were described as closed with slight to moderately weathered surfaces and spacing of approximately '/2 to 2 feet. Foliation orientations vary greatly due to the folding of the rock with an average dip to the west. The rock mass was defined as primarily competent with the following exceptions defined as poor: •. A shear zone, 280 feet long, cross cutting highwall, striking 20 to 30 degrees • A clay filled seam, 3 to 9 inches thick, dipping out of the slope • An area of adversely dipping foliation, potential for wedge failures 2006 GEOTECHNICAL ADDENDUM The 2006 geotechnical addendum indicated mining in the North Quarry was completed on south and east benches to approximately elevation 6,360. The mine slopes were recorded as 40 feet highwalls with 40 to 50 feet benches. The rock described in the report was granitic gneiss with mafic and felsic intrusions (felsic dikes and pegmatites). Joints in the rock mass were described as closed with slightly weathered surfaces and spacing of approximately 0.3 to 7 feet. Foliation orientations vary greatly due to the folding of the rock with an average dip to the west. The rock mass was defined as primarily competent with the following exceptions defined as poor: • An anticline/syncline pair dipping out of the rock face • A highly weathered rock dike, biotite gneiss, partially dips out of the rock face • A shear zone, 150 feet long, striking 80 to 90 degrees DISCUSSION The mine development plan for the North Quarry was included in the permit Amendments to mine permit M-1973-021, all of which were completed before mining began. The highwall plan assumed 80 feet highwalls with 80 feet benches to elevation 6455 followed by 80 feet highwalls with 40 feet benches, an overall slope of/z:l to a bottom elevation at 5,770. -4-