1997-09-10_REVISION - M1977247 (6)

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Following the same strike and direction, the next highwall contact: SENATORE HILL/HANGINGWALL CONTACT HIGHWALL This is the exposed gypsum rock bedding at a nearly vertical attitude which has had the hangingwall limestone removed to app. 30 feet below the actual hangingwall contact. This mining development work had prepared the entire Senatore Hill mining level for gypsum extraction. Under closure criteria, the vertical face must be reduced to a minimum 1:1 rock talus slope via drilling and blasting. The following tonnages are those rock volumes that would be drilled and shot to attain this end result. Section 1300 4000 tons Section 1400 4000 tons Section 1500 3800 tons Section 1600 4000 tons Section 1700 4200 tons Section 1800 4000 tons Section 1900 4500 tons Section 2000 4000 tons Section 2100 4000 tons Total tonnage 36500 tons COPPER HILL HIGHWALL CONTACT Other than the Gold Hill highwall, this is the largest highwall contact in the mine site. This highwall was constructed with the intent to allow for gypsum ore removal directly north of the highwall followed by the drilling, blasting, and bulldozing the highwall directly into the pit left from gypsum removal. At the cessation of mining operations in 1990, app. 500,000 tons of gypsum reserve was still in place. Highwall removal operations would effectively cover the gypsum reserve in this area and render this area unmineable for gypsum in the future without a large waste removal effort. Due to the fact that a 200 foot highwall currently exists, large volumes of sandstone and limestone must be drilled and blasted to reduce the current .3 : 1 slope to an acceptable I:1 slope. Section 2200 29000 tons Section 2300 37000 tons Section 2400 35000 tons