2015-04-17_REPORT - M1977004 (2)

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Pitch Reclamation Project Colorado Mined Land Reclamation Board — 2014 Annual Reclamation Report abandoned for the 2012 report because it was found to be cumbersome and confusing. This report uses ' the former naming scheme,'which omits the "year" from the monitoring point identification. Therefore, MP -99 -85 reverts back to MP -85, for example. , j During the 2012 survey, monitoring point P -04 was replaced with a new monument due to settlement of well backfill. There are currently 92 monitoring points in the North and South pits to monitor surficial slope movement. Of these 92 monitoring points, 29 had annual displacement magnitudes that were greater than survey error during 2013 — 2014 monitoring period, as shown on the summary table presented as Appendix A. By comparison, 8 points had annual displacement magnitudes greater than survey error during the 2013 — 2014 monitoring period. Displacement for monitoring points where displacement was not detected, or was less than calculated survey error is indicated as "ND" or non- , detectable. During the 2013 — 2014 monitoring period, 29 monitoring points indicated displacement greater than calculated survey error. As has been typical, the survey data indicated minor slope displacement in the northeast corner of the North Pit, the south wall of the 'North Pit, and the east wall of the South Pit. Displacement at the south wall of the North Pit ranged from 0.12 ft to 0.16 ft at 9 monitoring points. ' Displacement at the northeast corner of the North Pit ranged from 0.10 ft to 0.32 ft at 10 monitoring points. At the east wall of the South Pit, displacement during the 2013 to 2014 monitoring period ranged from 0.04 ft to 0.72 ft., also at 10 monitoring points: At two monitoring points located within the peat bog above the north wall of the North Pit, slope displacement of 0.21 ft and 0.34 ft was indicated. ' The current maximum displacement at the east wall of the North Pit is 0.32 ft/yr at MP -65. During the previous monitoring period, there was 0.10 ft/yr displacement at MP-43. The current maximum ' displacement at the east wall of the South Pit is 0.72 ft/yr at MP -92 compared to 0.37 ft at, also at MP -92 during the previous monitoring period. I ' 4.2 Inclinometer Evaluation Three slope inclinometers were installed in 2003 to monitor areas of the North Pit. Annual survey data I has been collected since July, 2003. Two slope inclinometers (198 -1 and 198 -2) are located on the south wall of the North pit and the other (198 -3) is above the crest of the east wall of the North Pit. I Total error, the sum of systematic and random error, associated with the slope inclinometer probe is 0.3 inches per 100 feet of depth according to the manufacturer (Durham - Slope Indicator, Inc.). The error associated with inclinometer 198 -1 is 0.75 inches, 198 -2 is 1.27 inches, and 198 -3 is 1.5 inches according to the depth of each installation. The data' collection system was repaired, tested and ' calibrated by Slope Indicator, Inc. in 2011. Baseline data for these inclinometers were initially collected on July 29, 2003. The initial baseline readings for these installations were corrupted due to data! collection equipment failure and subsequently ' replaced in 2011 with more recent surveys. The inclinometer data collection equipment was tested on site prior to collecting data for the 2012 surveys. The revised baseline survey date for 198 -1 is August 8, 2007. The revised baseline survey date for 198 -2 and 198 -3 is August 1, 2006. The impact of using more ' recent baseline surveys is essentially inconsequential, because any displacement indicated by the surveys has consistently been below error tolerances. In addition to the loss of baseline surveys, all other surveys prior to 2006 are no longer available. The plots for 198 -1 indicate minor slope displacement at about 20 ft below ground surface (bgs). There has been about 0.25 inches of displacement during the, 2013 — 2014 monitoring season. The total Pitch 2014 Reclamation Report 16Apri12016 Cw.Docx 22