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<br />will be conducted for about one year prior to the initial start- <br />up of the retorting and upgrading operations to develop a pre- <br />production stockpile of coarse ore on the plateau. During this <br />period, the room-and-pillar mining technique will be further <br />developed and refined. Other mining methods will be given further <br />evaluation. This period will be used to eliminate unexpected <br />problems involving the operation of the primary crusher. Fine <br />crushing and retorting operations will be commenced simultaneously. <br />Initial start-up of operations will require a shakedown period <br />of several months. <br />MINING <br />The method of extraction selected by Colony for initial recovery <br />of the oil shale reserve in place under the Dow West property <br />• is conventional underground room-and-pillar mining (Figure D- <br />4). The mine will produce approximately 66,000 tons of oil shale <br />per operating day. This production will equal the demand of <br />the processing plant, assuming that the plant would operate at <br />approximately 90 percent capacity on a yearly basis. With this <br />method, nearly 60 percent of the in-place shale can be extracted, <br />with the remainder being left in place as pillars to support <br />the overlying rock. A 60-foot thick section of oil shale, in <br />the upper part of the Mahogany zone, having an average grade <br />of about 35 gallons of shale oil per ton, will be extracted. <br />This proposed mining section contains the highest grade of oil <br />shale within the Mahogany zone on the Dow West property. The <br />mine would ultimately traverse essentially all of the Dow west <br />property, except those areas under the plant complex, and the <br />Middle Fork and Davis Gulch dams. Mine access will be from a <br />portal bench constructed in the canyon of the Middle Fork of <br />Parachute Creek at the level of the Mahogany zone outcrop as <br />illustrated in Figure D-5. The bench will be approximately 250 <br />feet x 750 feet of flat ground with additional sloping fill. <br />D-18 <br />