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<br /> <br />POND 5/6 <br /> <br />Pond 5/6, northeast of the reclaimed Pit 5 and adjacent to the Pit 5 main access <br />road, contained approximately 12 inches of water and was discharging through the <br />primary discharge riser and dewatering orifice. The primary spillway was <br />functioning properly. <br />The steep side slopes north and east of the pond has limited vegetation consisting <br />of native grasses and taller fortis. An erosional gully in the north corner of the <br />pond was observed in the embankment adjacent to the inlet culvert which drains <br />Pit 6. This gully was 1 ft. wide and approximately 1.5 ft. deep. <br />The north facing slope on the south side of the pond is more densely vegetated <br />with grasses due to moisture from a spring. The south sideslope also contains a <br />slump approximately 100 feet along the pond. The spring is located within the <br />slump itself. No recent slump movement was observed and it is expected that a <br />majority of the movement occurred immediately following pond construction. <br />As noted in previous sediment pond inspections, a 3 ft. diameter sinkhole exists <br />at the base of the east embankment, just east of the riser pipe. In June, water <br />was observed draining into this hole. There was no evidence of piping at either <br />the outlet culvert or on the embankment outslope. The drainage was either <br />reentering the outlet culvert or percolating downgradient beneath the embankment. <br />There were no additional gullies, cracks, slides, or seepages observed on the <br />embankment slopes. <br />The sediment level in the pond was observed to be approximately 1.2 ft. above the <br />dewatering orifice. The accumulated sediment present is above the designed <br />sediment level for the pond and should be removed to allow for water to discharge <br />through the outlet orifice. This would minimize drainage to the sinkhole previously <br />described. <br />SUMMARY <br />Certain concerns were identified during the semi-annual inspection of the four <br />sediment ponds at the Grassy Gap Mine. The most significant concern is the <br />sinkhole and sediment accumulation in Pond 5/6. Corrective measures as <br />outlined in the final closure plans should be implemented to provide for continued <br />stability and effective functioning of the pond. <br />The additional pond concerns are listed below in order of priority: <br />- Pond 4 embankment elevation discrepancy <br />- Erosional gully in Pond 5/6 embankment <br />- Slump on south side of Pond 5/6 <br />3 <br />