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6.4.4. Exhibit D — Mining Plan <br /> (a) Description of Methods <br /> Mining will advance in the numeric sequence assigned to the mining cells. For a <br /> given cell, mining will generally start at the low point of groundwater elevation <br /> and advance toward higher groundwater elevations. In general, this results in the <br /> direction of mining occurring perpendicular to the flow of and away from the river. <br /> Mining will utilize conventional dry mining techniques whereby dewatering <br /> trenches are first constructed around the perimeter of the active excavation. <br /> Mining highwalls will vary from 0.5H:1V to 3HAV. Topsoil is then removed with <br /> an excavator and stockpiled separately from overburden. Overburden is then <br /> removed with an excavator, loaded into non-road haul trucks (rock trucks) and <br /> transported to an initial stockpile. The initial stockpile volume is expected to be <br /> between 20,000 — 30,000 yd3 corresponding to an initial cut of approximately 2-3 <br /> acres. Overburden from subsequent cuts in a given mining cell will be directly <br /> backfilled to the previously mined out excavation slated for backfilling (see <br /> Exhibit F-Reclamation Plan - Sheet 1). <br /> Extraction of pit run will occur by excavator, which sits on top of the unearthed <br /> gravel layer and loads rock trucks. The excavator generally advances 15ft strips <br /> back and forth along the active mining highwall. Material mined from Cell 1 and <br /> Cell 5 which occur east and north of the river will be transported via overland <br /> conveyors across the river to the processing area. The overland conveyors have <br /> been engineered to span the Big Thompson River above the 100 yr floodwater <br /> surface elevations. The 100 yr floodwater surface elevations used to specify <br /> conveyor elevations are based on the existing FEMA effective data. Plan and <br /> profile drawings for the conveyor river crossings are given in Exhibit C-2-Mining <br /> Plan Sheet-2 East Conveyor. (for Cell 1) and Exhibit C-2-Mining Plan Sheet-3 <br /> North Conveyor (for Cell 5). <br /> (b) Earthmoving <br /> The primary earthmoving activity will be: <br /> 1. Stripping of topsoil and stockpiling in areas shown in Exhibit C-2 Mining <br /> Plan Map <br /> 2. Excavation of overburden and hauling to the stockpile areas or to the <br /> backfill area. <br /> 3. Excavation of pit run and hauling to the conveyor feed. <br /> Amen Aggregate Resource <br /> Specific Exhibits <br /> Page 7 of 84 <br />