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VI. SUMMARY AND CONCLUSIONS <br /> 1 Development of Cooley's Morrison Quarry is continuing in general accordance with the <br /> approved Mine Plan. Mining is continuing at the south end and east side of the Central Quarry <br /> and in the North Quarry in accordance with the Observational Method presented and approved in <br /> i the permit amendments. Mining in the North Quarry has varied slightly from the phasing <br /> suggested in Amendment No. 4 to improve operational considerations, but has not varied from <br /> the planned ultimate buildout. <br /> ' Excavations performed during 1997 do not generally reflect the ultimate, final quarry walls, <br /> except at portions of the fifth and sixth highwalls (from the top of the slope) of the east side of <br /> the Central Quarry. Excavation of the East Highwall for the Central Quarry is progressing as <br /> planned with ground conditions similar to those assumed for the baseline stability condition. A <br /> network of survey monuments for monitoring potential slope movement was installed for the <br /> slide area repaired during 1996. The repaired slope remained stable throughout i997 based on <br /> continued optical survey monitoring. <br /> Due to a relatively weak unweathered rock material at the south end of the Central Quarry, new <br /> benches and highwalls are planned to be excavated no steeper than 1 H:IV. Interim slopes are <br /> being developed at a configuration of 40 ft highwalls and 40 ft benches, with 80 ft by 80 ft <br /> interim highwalls and benches developed locally. <br /> In the North Quarry. benches and highwalls are presently being excavated no steeper than <br /> 1H:1V, and with highwalls generally no higher than 40 ft.. This slope configuration was <br /> implemented due to the weak rock within the shallow weathered zone near the ground surface <br /> and an adverse primary joint set orientation with respect to south to north mining used to start the <br /> redevelopment of the North Quarry. This conservative approach to interim slope development in <br /> ' the North Quarry continues despite encountering more competent rock as excavation depth from <br /> original ground surfaces increases, and despite changing to an east to west approach to bench and <br /> highwall development that is more favorable with respect to the primary joint set. This provides <br /> for generally greater safety and an.opportunity to observe highwall conditions and performance <br /> at lower heights before implementing higher highwalls up to 80 ft high already approved for <br /> "competent" rock tnass conditions. <br /> ' 13 G:\PROJ ECiS\20200\002\97ANN RPT.W PF <br />