REP17188

• Permit No: M1973021
• IBM Index Class Name: Report
• Doc Date: 1/16/1996
• Doc Name: NOTICE OF INTENT TO CONTINUE MINING OPERATIONS 112 ANNUAL REPORT
• Permit Index Doc Type: ANNUAL FEE / REPORT
• Media Type: D
• Archive: No

AREAS MINED IN 1995
During 1995, active mining occurred at the east side and south end of the Central Quarry and
a[ the eastern end of the North Quarry.
South End of Central Ouarrv. The south end of the Central Quarry was mined by
extending the end of the quarry to the south and by lowering the benches in that area. The
quarry floor remains at approximate elevation 6,490 ft, but was extended farther to the
south. In general, 40-ft highwalls are present and were used during development in
combination with benches equal to or greater than 40-ft wide. The existing slope
configuration is temporary and the highwalls and benches will change as the quarry is
further developed.
East Highwall of Central Quarry. The upper approximately 160 ft (vertical) of [he East
Highwall of the Central Quarry was reconfigured into four 40-ft highwalls and 50 to 60-ft
wide benches. This slope configuration is consistent with the upper portion of the Interim
Slope Configuration proposed for reestablishing stability of the East Highwall. This
Interim Slope Configuration was defined and shown in Mine Plan Amendments Nos. 3 and
4, and represents the first phase of stabilizing the slope after which the entire slope will be
reevaluated and, if desirable, reconfigured. All blasting of the highwalls in this area
employed precision (perimeter control) blasting methods. The upper two highwalls were
drilled and blasted vertically. !n response to unacceptable block and wedge instabilities on
these highwalls, the second and third highwalls (from the top of the slope) were drilled and
blasted at an angle of approximately 20 degrees from vertical (70 degree dip), resulting in
significantly improved behavior. The overall inclination of the slope across Benches 3 and
4 is the same as across Benches 1 and 2 and is also [he same as the proposed Interim Slope
Configuration.
East End of North Ottarry. Development and reconfiguration of the North Quarry was
initiated during 1995. In genera! mining advanced from south to north and west,
progressing up the ridge at the northeast corner of the North Quarry. Advance occurred
in a sequence of 40-ft vertical highwalls with benches equal to or greater than 40-ft wide.
Due [o the geometry of the ridge and the mining sequence, none of the present highwalls
are expected to be quarry highwalls at ultimate mined build-out. '
GEOTECHNICAL DATA COLLECTION AND SUMMARY
During 1995, additional geotechnical data was collected in the active areas of the Central and
North Quarries. The additional data consisted of geologic mapping along the East Highwall of
the Central Quarry and the east end of [he North Quarry.
During 1995, excavations in the Central and [he North Quarries did no[ exceed any conditions
which would require reevaluation of stability of the cut slopes. Work in the Central Quarry
was limited to excavation of benches at least 40-ft wide and highwalls 40-ft high at the south
end, and to the planned bench configuration (50 to 60-fr wide benches and 40-ft high highwalls)
on the east side. Note that the bench at approximate elevation 6,560 ft on the West Highwall
for the Central Quarry was reduced to a 40-ft width in 1994 and relevant information for that
work was included in last years' Annual Report.
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