2007-04-20_REVISION - M2005021 (5)

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• • with the final mining slope of 2H:1 V, which will maximize gravel recovery and additionally will reduce the required backfill material to bring the slopes to a 3H:1 V slope. Secondly, this offset provides additional slope stability. This is demonstrated through no evidence of slope failure during the life of pits which have used similaz techniques in the same general azea. However, a failure would be governed by the internal angle of friction of the material. This would limit the failed slope to an angle of 34 degrees or ~1.SH:1 V. This failure would not only stay within the permit area, it would stay within the final slope envelope. The maximum total tonnage sold from the site in any one calendaz yeaz is 378,750 tons, though the expected annual average is 252,500 tons. The raw material will be sold in three products: road base, concrete, and asphalt. A break down of the product tonnages and mined tonnages can be seen in Table D-1. A breakdown of the estimated azeas is included in Table D-2 Table D-1 Average Annual Product Distribution roduct Tons Sold % Reject Rate (Naturals) Tons Mined oad Base 200,000 0% 200,000 Concrete 37,500 10% 41,667 sphalt 15,000 40% 25,000 otal 252,500 5% 266,667 As previously mentioned, dewatering of the pit is currently and will continue to be accomplished by the use of perimeter trenches which drain to a sump that has been excavated into the pit floor in the northwest comer of Phase 1. Water from the sump is then pumped to a settling pond located to the northwest of the sump where the fines aze allowed to settle out. From the settling pond, the water flows into a 20" diameter discharge PVC pipe which goes under the Hutchins access road and dischazges into a ditch owned by Will Hutchins, as seen on Map C-2, Mine Plan Map. The design for this ditch is based on 1800 gallons per minute, which can be seen on Map C-4 Sheets 1 and 2. As of Mazch 2007, the flow in the pipe is less than 500 gpm. At some point many years later when a lazge area is being dewatered, the existing 20"pipe may have to be improved to a 36" culvert in order to have the capacity to handle the flow from the pump. This culvert may end at the north edge of the Hutchins Road, where the flow will enter a ditch. Map Anderson Pit, April 07 D-3