2007-04-20_REPORT - M1977004 - Laserfiche WebLink

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Pitch Reclamation Project Colorado Mined • Land Reclamation Board 2006 Annual Reclamation Report 4.0 MONITORING AND ANNUAL REPORTING 4.1 Slope Movement Vector Analysis Survey monuments have been installed on the east and south walls of the North Pit to monitor surficial slope movement periodically since 1994. The area east of the North Pit Lake and south of Northing 113,500 is referred to as the south wall of the North Pit; and the area east of the North Pit Lake and north of Northing 113,500 is referred to as the east wall of the North Pit. This differentiation is for ease in discussing slope movement and does not imply that there is a kinematic distinguishing feature at this location. The original group of monitoring points was installed in 1994. Additional monitoring points were installed in 1996, 1997, 1998, 1999, and 2004. Since 2004, 36 new monuments have been installed. Monument locations are provided on the Slope Displacement Vectors drawing presented in . Appendix A. Surveys are usually conducted as close to one year apart as possible, allowing the magnitude of displacement to be reported as a velocity in terms of fUyear. Surveys of all accessible monuments were conducted on October 3, 2006 with the previous survey performed on October 15, 2005. The surveys are actually conducted over several consecutive days with the median date used to represent the data set. Of the 83 points surveyed in 2006, 32 had annual magnitudes that were greater than survey error during the 2005-2006 monitoring period, as shown on Table 1. By comparison, 15 points had annual magnitudes greater than survey error for the 2004 - 2005 monitoring period. Of the12 additional monuments that were added in 2004 to monitor the slide at the east wall of the south pit, 7 showed displacement greater than survey error. Velocity vectors were calculated for the 32 points and are depicted with green circular symbols and velocity vectors on the Slope Velocity Vectors Map (Appendix A). Points with a displacement less than the survey error are shown in gray on the map. Monitoring point MP-63 is located on the East Wall of the South Pit. The displacement indicated at MP-63 for the 2004 - 2005 yearly interval was 0.40 ft. The magnitude of displacement for MP-63 reduced to 0.16 ft for the 2005-2006 period, indicating that the velocity of the slide has decreased during this period. Based on performance of similar slopes at the site, it is reasonable to assume that displacement will be minimal (less than 0.5 ft per year) and should reach a quasi- 10