2011-04-19_REPORT - M1977004 - Laserfiche WebLink

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There does not appear to be any concern, at this time, for the vent raise on the east wall of the North Pit that was backfilled and capped as part of the adit closure work that took place in 1995. The vent raise lies south of current slope displacement. An additional 13 monuments were added in 2005 to monitor the slide at the east wall of the South Pit. Monitoring points were replaced and added in 2010, resulting in a net gain of two monitoring points. Some of the monuments that had been compromised were no longer located in key positions, and were abandoned without replacement. Monuments that were abandoned include; S-2, S-4, F-1, F-2, HS-2, and HS-3. Monument H-4 is located near a tension crack and may soon be compromised. H-4 should be checked prior to by next year's survey. A total of 10 monuments indicated displacement greater than survey error during the 2009 - 2010 monitoring period. The tension cracks and scarps were graded closed during October 2010. Also, the bench that transects the displacement was graded with a central crown to promote drainage in both directions of the bench. Displacement appears to have slowed. The current maximum displacement is 0.72 ft/year at monitoring point S-4, which had a displacement of 1.0 ft/year during the previous monitoring period, and nearly 2 ft in 2008. Grading may have contributed to the slower rate of displacement, but it is likely that other factors prevail. This feature will be monitored closely in 2011 and repairs will be made as necessary. Photograph 3 is a photograph of the slope displacement on the east wall of the South Pit. Linear features contrasted with the light snowfall are traces of Chester Fault structures. The slump is above the upper bench to the right side of the photograph. Pitch Reclamation Project Colorado Mined Land Reclamation Board 2010 Annual Reclamation Report 9