2010-05-03_REVISION - M1979205 (6)

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Mining is planned in two distinct areas, as shown on Map C-2. These are Mining Areas 1 and 2. Each area is further divided into phases of 3.5 to 5.5 acres each. Prior to mining, each area will need to be dewatered. This will be accomplished by installing a perimeter dewatering trench. The trenches will lead to a sump as shown in the maps. Water will be allowed to pass through a gravel berm prior to entering the sump. This will act to filter out sediment. The dewatering pump in Mining Area 1 will discharge to the Colorado River, the pump in Mining Area 2 will discharge to the wetland oxbow. This is necessary due to the water table draw-down associated with pit dewatering. All water discharged will meet CDPHE requirements and will likely contain much less sediment than that which exists in the river naturally. As mining progresses through the areas, the pumping arrangement will continually change. The locations of the pumps and ditches are approximate as shown on the mine plan maps. The overall design is to dewater one pit at a time. However some overlap of two mining areas being dewatered at the same time is possible at the end of a mining area's life. Wetlands surrounding the dewatered area will be supplied with water from the pits to prevent dry-up. It is expected that dewatering of a pit will require approximately 1000 gallons per minute pumping capacity. During initial dewatering, the pumping demand may be up to three times the stable pumping rate or 3000 gallons per minute. Once the pit has been dewatered, mining will begin. Primarily, front-end loaders will be used to mine the raw gravel. The slopes of the pit will be mined to 2H:1 V slopes at the outer edges of the pit except in two minor areas where well pads are constructed, where the mining slope will be 0.5H:1 V to LOH:1 V, but will be backfilled to 3H:1 V prior to use of the pad for well drilling. While mining in the center of the pits, a steep highwall will be also be used (0.5H: IV). This highwall will be laid back as it approaches the mining limit edge. Some dozer pushing or ripping may also be used. The loader will directly load to a crusher or into trucks which will deliver the material to a crusher. Equipment will utilize the existing roads where appropriate and additional roads will be added as shown in the mine plan map. The road alignments shown on Map C-2 are the approximate final locations. Current roads as seen in Map C-1 will be utilized until realignment is necessary. For the initial Phase of Mining Area 1, all mined material will be stockpiled adjacent Scott Pit March 10 D-6