2008-04-30_REPORT - M1973021 (3)

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removal of three to four rock benches to provide room for haul road construction on the east side of the pit. The rock removed was replaced with compacted fill. 2.2 North Quarry Mining in the North Quarry continued in 2007 and consisted of completing the east half of Bench C (approximately elevation 6260) and mining Bench D (approximately elevation 6220). Material was mined utilizing the default slope configuration of 1:1 (H:V) and consisted of 40 to 50 foot highwalls and 40 to 50 foot benches. The North Quarry area mined in 2007 is approximately shown on Figure 2. Figures 3 and 4 are a photo documentary of the Bench D highwall surveyed for this report. • 2.3 South Quarry Mining began in the South Quarry in 2007 and consisted of clearing a large bench to elevation • 7000 feet above MSL. The highwall associated with the mining was approximately 60 feet; • however, the bench has not yet been completed. The South Quarry area mined in 2007 is approximately shown on Figure 5. Figure 6 is a photo documentary of the Bench 1 highwall surveyed for this report. • • 3.0 FIELD DATA At areas exposed by mining in 2007, rock mass data including joint orientation and dip, foliation orientation and dip, rock mass rating (RMR) classification, estimates and unusual rock features such as shear zones, persistent intrusions, or weak rock zones, were documented. Orientations were collected using a Brunton compass (10 degree east magnetic declination' ) and recorded using the right hand rule. All orientation measurements were estimated from a safe distance back from the highwalls due to active mining activity and as requested by AI. 3.1 Central Quarry No mining occurred in the Central Quarry in 2007 and thus no orientation data related to mining activity was collected. Observations of the existing highwalls and benches were conducted and compared with previous observations. Localized instabilities were observed and local raveling of the rock faces has continued. This raveling is likely due to adverse jointing, rock weakened by alteration, and/or weathering actions such as freeze thaw cycles. Blocks loosened in this fashion are generally small (less than approximately 1 '/z feet in diameter) and collect on the benches. Three to four rock benches were removed for haul road construction. The benches were removed with controlled blasts intended to minimize the rock disturbance in the remaining wall. The rock was replaced with compacted fill. Twenty feet of rockfall containment mesh clamped to rockbolts was installed on the wall above the haul road to minimize and contain local raveling. ~ Topozone, 2007, "Topographic Map of Morrison Quadrangle, Morrison, Colorado", http•//www topozone com/map asp~lat=39.65361&lon=-105.19056 -2- F:\3919_038W nnual_Rcport_2007\Gcotcch_Addcndum_2007W nnual_Rcport_2007_Geotcch.doc April 2008