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' The south end of the Central Quarry floor remained at approximate elevation 6,490 ft, <br /> and was not extended farther to the south during 1997. The existing slope at the south <br /> end of the Central Quarry is temporary and the highwalls and benches will change as the <br /> ' quarry is further developed. <br /> ' 3.3 Central Quarry Floor <br /> An area within the floor of the Central Quarry that comprises approximately three acres <br /> was lowered one bench from approximately El. 6,490 ft at which elevation the floor had <br /> ' remained during the past several mining years. A slot approximately 800 to 900 ft long <br /> by approximately 150 ft wide and approximately 40 ft deep was removed during 1997 to <br /> approximately El. 6,450 ft. Relatively high specific gravity rock due to localized iron <br /> ' mineralization was encountered in this mined area. This "heavy" mineralization <br /> presented some operational complications relative to excavation, crushing and product <br /> specifications, but was not observed to affect stability. <br /> 3.4 North Quarry <br /> ' In general mining advanced from south and east to north and west, progressing up the <br /> ridge along the northeast and north boundaries of the North Quarry at a large,scale <br /> during 1996 when mining activities for that year were concentrated in the North Quarry. <br /> ' North Quarry mining began primarily as a south to north operation, but was changed to <br /> primarily an east to west operation during 1996. This change was made by CAMAS to <br /> create more favorable interim mining slope orientations with respect to a dominant <br /> ' southerly dipping foliation jointing that exists in the North Quarry. This general <br /> approach continued while mining deeper, but without creating additional disturbed <br /> acreage in the North Quarry during 1997. <br /> Mining has varied from the phasing suggested in Amendment No. 4 in that the large flat <br /> area shown developed at El. 6,455 ft down to the plant level has not yet been establish- <br /> ed. Instead, a large flat are was established higher up at approximately El. 6,580 ft and <br /> ' the mining effort to date has developed a regular progression of benches higher and <br /> farther west first, before lowering the areas north and west of the plant. This variation <br /> has no impacts to Limits of Mining or Limits of Disturbance and was made to preserve <br /> the circumferential haul road for use in development of the upper parts of the North <br /> Quarry and to delay work immediately above the plant. Work above the plant will <br /> require careful blasting and excavation to address potential personnel safety issues and to <br /> ' avoid damages or shutdown of the new crusher. <br /> In addition, mining has generally continued in a sequence of 40 ft to 80 ft vertical <br /> highwalls with benches equal to or greater than 40 to 80 ft.wide and, locally, as wide as <br /> 100 ft creating stable interim highwall slope angles. Mining interim 80 ft maximum <br /> vertical highwalls with benches equal to or greater than 80 ft wide was done in 1997 to <br /> ' develop the North Quarry and to tie-in to older benches established under the original <br /> mine plan. As mining progressed to tie-in with existing benches at the west end of the <br /> North Quarry benches and highwalls were tapered to smaller widths and heights as <br /> ' necessary. <br /> ' 4 G:\PROJECI'5\20200\002\97ANNRPT.WPF <br />