2016-01-07_GENERAL DOCUMENTS - C1981019

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and after the inspection, including: the post-mining topography, cross-sections of backfilled and graded areas, and as-built drainage profiles. During the partial Phase I Bond Release inspection, participants walked through most of the bond release request area to allow for visual assessment of compliance with pertinent requirements. Backfilling and Grading For the SL-08, observations were made during the bond release inspection with regard to approximate original contour and stability of the reclaimed landscape. To determine compliance with Colowyo’s approved approximate original contour (AOC) in the SL-08 areas, elevation data provided in the SL-08 Bond Release application was compared to GPS data collected by the Division staff. Twenty-seven points were selected near the cross-sections of the seven reclamation parcels or “zones” that are being requested for partial Phase I Bond Release. These points were selected utilizing Exhibit 1 of the SL-08 application. Points were placed at selected contour elevations in ArcGIS (to try to cover the majority of the area), and those points were then downloaded into a Trimble Yuma. During the bond release inspection, Zach Trujillo navigated to the points using the data in the Trimble, and a GPS data point was collected at each site. The points collected at the site were downloaded from the Trimble into Pathfinder office and converted into a point shape file to utilize in ArcGIS. 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. Unfortunately, an error occurred with the Trimble Yuma for this specific point and no elevation data was able to be collected. All measured elevations documented in this report will be uncorrected data. However, as shown in the Figures section of this report, the comparison between measured and approved elevations shows a consistent parallel relationship with each other. It can be assumed from this relationship that the difference in measured versus approved elevations is due to the inability to obtain corrected data. The elevation data collected by the Division was compared to elevation information provided in the SL-08 Bond Release application. After comparison of the Division’s uncorrected data and associated known elevation, uncorrected elevation points were found to be on average of +38 feet off the as-built elevations, shown on SL-08 Exhibits 1, 2A, 2B and 3. Given the expanse of the mine site and the steepness of the terrain at Colowyo and parallel relationship between the measured and approved elevations, the difference in elevation is acceptable. For the West Pit, East Pit and the South Taylor Pit, the Division finds that the Colowyo Mine has achieved a post-mining surface that conforms to the approved post-mining topography and resembles the general surface configuration of the land prior to mining. All highwalls have been eliminated and the reclaimed lands blend in well with the adjacent undisturbed slopes. No Proposed Decision and Findings of Compliance January 2016 Partial Phase I Bond Release SL-08 Page 6