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' VI. SUMi1tARY AND CONCLUSIONS ' Development of CAMAS Colorado Morrison Quarry is continuing in general accordance with the approved Mine Plan. Mining is continuing at the south end, the east side, and the floor of ' [he Central Quarry and in the North Quarry in accordance with the Observational Method presented and approved in the permit amendments. Mining in the North Quarry has varied slightly from the phasing presented in Amendments Nos. 4 and 5 to improve operational considerations and to provide for adequate mining safety for personnel, but has not varied from the planned ultimate buildout. Excavations performed during 1998 do not generally reflect the ultimate, final quarry walls, ' except at portions of Bench 2 and Bench 1 highwalls of the east side of the Central Quarry. Excavation of the east side for the Central Quarry is progressing as planned with ground conditions similar to those assumed for the baseline stability condition. A network of survey monuments for monitoring potential slope movement was installed for the slide area repaired during 1996. The repaired slope remained stable throughout 1998 based on continued op[ical survey monitoring of these points. ' D i ue to a relat vely weak unweathered rock tnaterial at the south end of the Central Quarry, new benches and highwalls are planned to be excavated no steeper than 1H:IV. Interim slopes are being developed at a configuration of 40 ft highwalls and 40 ft benches, with 80 ft ' by 80 ft interim highwalls and benches developed locally. in the North Quarry, benches and highwalls are presently being excavated no steeper than 1H:IV, with highwalls generally no higher than 40 ft. This slope configuration was implemented due to the weak rock mass within the shallow weathered zone near the ground surface and an adverse primary joint set orientation with respect to south to north mining ' direction. This conservative approach to interim slope development in the continues despite encountering more competent rock as excavation depth from original ground surfaces increases, and despite changing to an east to west approach to bench and highwall ' development that is more favorable with respect to the primary joint set. This provides for generally greater safety and an oppormniry to observe highwall conditions and performance at i lower heights. Apre-exiting 80 ft highwall was exposed on the western side. ' Reconfigurations to decrease the height of highwall are planned during 1999. 1 IJ 1 1 ' G:rPROIECfS~?0]fp Mornran Quartyr002UMUil Reyon Gm¢cMical AddeMum~1998~98rpr mukup.d« Page 10