2013-01-31_REPORT - M1973021 (2)

Home Browse Search

Rock observed in the highwalls was predominantly competent with the following exceptions: • Bench 6700 stations 0 +90 to 3 +00 (new area north of the realigned haul road) and Bench 6640 stations 15 +50 to 16 +50 consisted of altered sillimanitic gneiss that is very poor in quality and appears to be related to the fault zone. Local instability due to overtopping has occurred. The instability is roughly parallel to the zone of weak rock associated with the fault. Extra caution should be taken when developing highwalls in areas where this rock is present. If, during mining, this rock is encountered in areas not mentioned in this report, Tetra Tech should be contacted and the areas evaluated. • Throughout the South Quarry, there are localized zones of more highly fractured and weathered material that will tend to ravel. Raveling will tend to be caught on the underlying benches. Extra care should be taken in these areas. These areas are outlined in the field data section of this report. • Highwalls near the fault zone will be monitored and observed for movement. Care should be taken when removing the weak rock because the strong rock that remains will tend to overhang. Scaling or other methods will likely be necessary to limit overhanging rockfalls. Based on our observations the overall slope conditions are considered stable and warrant primarily operational considerations. 13 Morrison Quarry Annual Report 2012 P \23514\ 133 - 2351 4- 13002\Deliverables\Dehv -01 -2012 Annual Report \Annual_ Report_2012_Geotech doc January 2013