2013-06-03_REVISION - C1981019 (2)

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INTEROFFICE MEMORANDUM TO: ROB ZUBER FROM: JASON MUSICK SUBJECT: C1981 -019 COLOWYO MINE SL -7 BOND RELEASE INSPECTION BACKFILLING AND GRADING GPS INSPECTION DATE: 06/03/2013 In order to determine compliance with Colowyo's backfilling and grading to meet the approximate original contour for SL -7, 25 locations were derived on contour lines and 10 locations along the Final East Pit Ditch and the West Taylor Fill utilizing Colowyo's SL -7 Bond Release Areas, Exhibit 1. Points were placed at various contour elevations in ArcGIS and those points were then downloaded into a Trimble Yuma. During the bond release inspection, the points were navigated to using the data in the Trimble and another point was collected to determine the elevation as compared to elevation information provided in the SL -7 Bond Release application. The points collected at the site were downloaded from the Trimble into Pathfinder office and converted into a point shapefile to utilize in ArcGIS. The points collected were compared with the random points based on elevation. Elevation data, using the Trimble Yuma is not exact. The Geoid used in the Trimble GeoXT is DMA 10X10 Global, which is a global elevation Geoid and not as accurate as a localized Geoid. For this reason a known point was collected at the Colowyo Mine office to determine a correction factor for the elevation collected in the Trimble Yuma. The elevation at the base station was 7287.6' with on the Trimble Yuma utilizing a projected coordinate system; UTM, NAD 83, Zone 13 North compared to 7263.1 with the coordinate system provided by Colowyo of UTM NAD 27 Colorado State Plane, which provide a correction of approximately +24.5 feet. The elevation data was corrected and post - processed data. The main purpose of the elevation collection was to determine if the elevation data showed any anomalies such as drastic elevation changes or fluctuations in elevation. All elevation points were found to be between +/ -20 feet of the as -built elevations, shown on SL -07 Exhibits 1, 2A, and 2B. Given the correction factor of +24.5' at the Colowyo Mine Survey Point the difference in elevation is acceptable. All of the measured elevations in the permanent post- mining drainage channels in the SL -07 area were also +/- 20 feet of the elevations shown on the approved channel profiles. As with the cross - section data, the measured and approved post mining drainages are consistent.