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INSPECTION REPORT Site: National King Coal Mine, Hesperus, Colorado ~ ~ 5/ Inspected By: Don R. May, P.E., Project Engineer of ~J~~ Inspection Date: Quarterly Inspection June, 2006 ~F~;~.,,,,,,,,.••; Ponds: Photograph 1 shows the west pond with some standing water. The inlets, outlets and embankments of both ponds were inspected and appear in good condition.. Both ponds are relatively Gean of sediment and appear to have more than adequate storage volume. As mentioned in previous reports the staff gage marked relative to the required bottom elevation is missing from the west pond and a replacement would help the operator determine when and how much sediment removal is needed. Drainage Ditches: The drainage channels, on the north and south sides of the waste pile, appear in good general condition. Photo 2 shows the ditch that collects runoff from the top of the pile and photo 3 shows the ditch along the access road near the top of the pile. All other drainage channels on the site were inspected and are in good condition. Ditches and overland flow through and around the upper and lower yards are working well and both areas are in good shape. Care should be taken to keep all of the pipe inlets Gear of sediment and debris. Except where noted, all drainage features have been constructed and are operating as stated in the drainage plan submitted to the Division of Minerals and Geology. Coat Waste Pile: The waste pile face appears stable and in good condition. The middle portion of the face of the waste pile is shown in photo 4. The section below the access road appears steeper than the portion above the access road. As stated in the approved design the waste pile face should be maintained at a slope of no greater than 3:1. As discussed in previous reports the lower portion of the pile face near the toe of the slope has been over-steepened due to widening of the road area around the coal storage pile (photo 5). The mine has.purchased large concrete blocks that can be used to create a low retaining wall at the toe and return the slope to the design value. The following schematic diagram shows an appropriate configuration for the retaining wall. The bottom tier of blocks should be buried '/. fo % of the block height in a compacted key trench. Successive tiers should be offset %, of the blocs width. '/." gravel should be used to backfill the space immediately behind each tier of blocks. Joint spaces between adjacent blocks will allow water to drain out from the gravel alleviating hydrostatic pore pressure that builds up behind the wall. The schematic diagram show two tiers. The actual number of tiers (and resulting total height) will depend on the dimensions of the blocks and the amount of slope adjustment needed to return the face to the design slope. If the height of the retaining wall, above the driving surface, .exceeds six feet a more detailed stability analysis will be required.