2010-04-19_REPORT - M1977004 - Laserfiche WebLink

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Pitch Reclamation Project Colorado Mined Land Reclamation Board 2009 Annual Reclamation Report map. All monitoring points are shown on Table 1 and their locations on the Slope Vector Map. Displacement for monitoring points where displacement was not detected, or was less than calculated survey error is indicated as "ND" or non-detectable on the map (SRK Consultants Inc. 2010). Prior annual reports have noted that the possibility exists for an increase in slope displacement with increased precipitation. Slope displacements for the monitoring points within survey error during the 2008-2009 monitoring period were observed to have either decreased, or stay stable from the displacements observed during the 2007-2008 period. The current displacements for all the monitoring stations were, on average, approximately 40 percent less than the displacements during the previous monitoring period. From previous reports, the 2007-2008 period saw an increase in displacement which was possibly a result of a higher than average rainfall over that period. The increased displacement was observed primarily in the northeast corner of the North Pit and the small slump feature above the east wall of the South Pit. The current maximum displacement at the northeast corner of the North Pit is 0.43 ft/year at MP-66, which had a displacement of 0.62 ft/year during the previous monitoring period. Displacement at the slump above the east wall of the South Pit also appears to have slowed. At the slump, the current maximum displacement is 1.00 ft/year at monitoring point S-4, which had a displacement of 1.95 ft/year during the previous monitoring period. The decrease in displacement velocity for the 2008-2009 period is also an indication that the 2007-2008 period had a higher than normal rate of displacement. During 2008, repairs were made to improve drainage at the slump above the east wall of the South Pit, which has contributed to the improved stability of this small feature. The slump has no potential to impact the site, other than minor displacement, and is expected to gradually reach equilibrium. After the spring snowmelt, all areas that have shown displacement in the past will continue to be monitored closely in 2010. 4.2 Inclinometer Evaluation Three inclinometers were installed in October 1998 (198-1, 198-2, and 198-3) to monitor any subsurface movement within the south and east walls of the North Pit. The inclinometer locations are provided on the Slope Displacement Vectors drawing presented in Appendix A. Inclinometer 198-1 is located on the lowest bench on the south wall; 198-2 is located on the 10,600 ft. bench of the south wall and; 198-3 is located above the crest of the east wall and above the headscarp. Inclinometer readings were taken on August 4, 2009. Data collected in 1999 through 2009 from all three inclinometers indicates a relatively constant rate of subsurface displacement of 8