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6,4.4 Exhibit D -Mining Plan <br />Mining Description <br />The Mining Plan is described in this section and correlated with Exhibit C-2, Mine <br />Plan Map. Mining is sequenced with designated mining Phase I -Cells 1 <br />through 4 (West Pit) and Phase II -Cells 1 through 3 (East Pit) as shown in <br />Exhibit C-2. <br />Stripping and mining will incorporate conventional aggregate mining methods, <br />including use of scrapers and dozers to strip overburden, hydraulic excavators <br />and scrapers to mine sand and gravel, and haul trucks to move material onsite. <br />To facilitate "dry" mining below the groundwater table and the creation of <br />developed water resources (reservoirs) at reclamation, a slurry wall will be <br />constructed surrounding Phase I -Cells 1, 2, and 3. First, a perimeter drain will <br />be constructed around the area to mitigate predicted groundwater mounding due <br />to slurry wall placement. The perimeter Drain design is given in Attachment G-1, <br />Groundwater Modeling Report and Perimeter Drain Design. A perimeter slurry <br />wall will then be constructed surrounding Phase I -Cells 1,2 and 3. The slurry <br />wall will be three feet wide, and keyed into the bedrock, to prevent groundwater <br />migration into or out of the mining excavation and proposed reservoirs. To <br />protect the slurry wall, all areas adjacent to the slurry wall will be mined at 2H:1V <br />slopes with a 10 ft offset. For Phase I -Cell 4, dewatering trenches will be dug <br />around the bottom perimeter of the mining cell and any accumulated water will be <br />pumped to a sediment pond shown on Exhibit C-2. <br />Phase II will undergo the same pattern as Phase I -construction of a perimeter <br />drain, then slurry wall, followed by mining. Additionally, Phase II mining will be <br />dependent on the seasonal mining of Cell 3. Because Cell 3 lies within the <br />floodway, it will be mined only during the non-flood season -September 15 <br />through April 15 -and backfilled prior to the end of each season. Cells 1 and 2 <br />will be mined year-round. Stockpiling will occur outside the floodplain as shown <br />on Exhibit C-2. <br />~~~~p0~ <br />~~o~~ z o zoos <br />Division of R~~c~smation, <br />tYlining and Safety <br />November 16, 2006 Bokelman/Walters Pit <br />Page 2 of 36 Regular 112 Permit Application <br />