2015-02-18_INSPECTION - C1981028

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February 5, 2015 C- 1981 - 028 /Keenesburg Strip Mine JLE Figure 2 Map and the measured topography. For area 32, walking from the east to the west, the topography rises in elevation and then falls in elevation into the west drainage. The SL7 Map elevations ranged from about 4 feet lower to about 5.19 feet higher than the approved post mine elevation with an average difference of 1.16 feet higher in elevation. The general shape of the actual topography approximates the approved post mine topography when comparing the Q -1 map elevations to the SL7 map elevations. The slope of the hill on the eastern aspect is not as steep as anticipated. The measured elevations ranged from 2.19 feet lower to 14.92 feet higher than the approved post mine elevations with an average difference of 6.46 feet higher in elevation. It would appear that the measured elevations do vary significantly from the approved post mine topography. After downloading the data collected in the field, the vertical precision which measures the accuracy of the elevation collected was reviewed. The vertical precision was fairly large, meaning the elevation measured varied about 10 meters. Given this, the Division does not believe the elevation measured during the inspection reflect the actual topography. After processing the data collected in the field, I researched what would cause the inaccurate measurements. Based on this information, I will conduct a follow -up inspection to attempt to collect more accurate data. For Area 31, walking from west to east, the topography rises and then falls to east. The SL7 Map elevation ranged from about 4 feet lower to about 2.29 feet higher than the approved post mine elevations with an average difference of .45 feet lower in elevation. The general shape of the actual topography approximates the approved post mine topography when comparing the Q -1 map elevations to the SL7 map elevations. The slope of the hill on both the eastern and western aspect is not as steep as anticipated. The measured elevations ranged from 1.1 feet lower to 16.75 feet higher than the approved post mine elevations with an average difference of 6.98 feet higher in elevation. For the reasons discussed above for Area 32, the Division does not believe the elevations collected in the field are accurate. For Area 30, walking from east to west the topography rises and then falls in elevation to the west drainage. The SL7 Map elevation ranged from about .82 to 1.47 feet higher than the approved post mine elevations with an average difference of 1.05 feet higher in elevation. The general shape of the actual topography approximates the approved post mine topography when comparing the Q -1 map elevations to the SL7 map elevations and slope percentage. The measured elevations ranged from 2.33 to 10.04 feet higher than the approved post mine elevations with an average difference of 6.26 feet higher in elevation. For the reasons discussed above for Area 32, the Division does not believe the elevations collected in the field are accurate. I walked a transect down the western drainage from the south end to the north. The SL7 Map elevation ranged from about .75 to 2.93 feet higher than the approved post mine elevation with an average difference of 1.83 feet higher in elevation. The general shape of the actual topography approximates the approved post mine topography when comparing the Q -1 map elevations to the SL7 map elevations and slope percentage. The measured elevations ranged from .17 to 3.87 feet higher than the approved post mine elevations with an average difference of 1.6 feet higher in elevation. The measured elevations seem to be more accurate for these GPS points. The western drainage should positively drain water to the north as designed. It appears CEC did not backfill as high in elevation as originally intended for areas 31 and 32. However, if the Number of Partial Inspection this Fiscal Year: 5 Number of Complete Inspections this Fiscal Year: 2 Page 4 of 9