2012-04-19_REPORT - M1977004 (2)

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Pitch Reclamation Project Colorado Mined Land Reclamation Board — 2011 Annual Reclamation Report 4. MONITORING AND ANNUAL REPORTING 4.1 Slope Movement Vector Analysis Survey monuments have been installed at the Pitch Reclamation Project to monitor surficial slope displacement. 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 pit lake and north of Northing 113,500 is referred to as the East Wall of the North Pit. These walls are identified separately for ease in discussing slope movement and do not imply the presence of a kinematic distinguishing feature at this location. The first monitoring points were installed at the east and south walls of the North Pit in 1994. Some of the monuments have been destroyed due to re- grading, and critical ones were replaced with new monuments having different identification numbers. In 1996, six monitoring points were installed to replace points in the north pit. In 1997, 14 monitoring points were installed to monitor shallow slope movement that was observed on the south wall of the North Pit. In 1998 and 1999, five monitoring points were installed at existing locations including inclinometer collars. In 2000, 11 monitoring points were installed in the North and South pits. A monitoring point was placed at the collar of piezometer P -09 at the east wall of the South Pit in 2001. In 2005, 13 monitoring points were installed to monitoring shallow slope displacement observed on the east wall of the South Pit. On October 8, 2010, six of the monitoring points on the East Wall of the South Pit that were installed in 2005 were abandoned, because they had been compromised by slope displacement and tension crack formation. Also at that time, eight new monitoring points were installed to replace the abandoned installations and positioned to provide a profile of the slope. Monument locations are provided on the Slope Displacement Vectors drawing presented as Appendix A. Surveys are usually conducted as close to one -year intervals as possible, allowing the magnitude of displacement to be reported as a velocity in terms of ft/year. In 2011, names of monitoring points were modified to show the year the monument was set. This change was made to differentiate when a new baseline was established for a particular monitoring point. For example, MP99 -85 is monitoring point MP- 85, which was established in 1999. Three monitoring points were added and P95 -4 was replaced by P11 -4. There are currently 74 monitoring points in the North and South pits to monitor surficial slope movement. Monument locations are provided on the Slope Displacement Vectors drawing presented as Figure 1. Surveys are usually conducted as close to one year intervals as possible, allowing the magnitude of displacement to be reported as a velocity in terms of ft/year. Surveys of all accessible monuments were conducted on November 15, 2011 with the previous survey performed on August 27, 2011. The surveys are actually conducted over several consecutive days with the median date used to represent the data set. Of the 74 points surveyed in 2011, 27 had annual displacement magnitudes that were greater than survey error during the 2010 -2011 monitoring period, as shown on the summary table presented on Appendix A. By comparison, 31 points had annual displacement magnitudes greater than survey error for the 2009 -2010 monitoring period. Points with a displacement less than the survey error are shown in grey on the map. All monitoring points are shown on the summary table located in Appendix A and Table 1. Displacement for monitoring points where displacement was not detected, or was less than calculated survey error is indicated as "ND" or non - detectable. The current maximum displacement at the East Wall of the North Pit is 0.35 ft/year at both MP96 -66 and MP96 -69. During the previous monitoring period, there was 0.21ft/yr displacement at MP96 -66, and Pitch 2011 Reclamation Finalreport 19Apr12.Doc 11