2016-10-19_REVISION - C1981019 (5)

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Proposed Decision and Findings of Compliance September 2016 Partial Phase I Bond Release SL-09 Page 5 mining topography, Maps 29 and 29A show the backfilling and grading schedule, and Maps 41 and 41A show the location of the permanent, post-mining drainage channels. The pre-mining and post-mining cross-sections are shown on Maps 20 and 20B, and the permanent drainage channel profiles are shown on Maps 33 and 33B. Exhibits 2 of the SL-09 application show cross-sections of the SL-09 area, including approved post mining topography alongside the constructed topography. IV. OBSERVATIONS AND FINDINGS The following discussion of observations and findings focuses on the results of backfilling and grading work and drainage reestablishment in West Pit for the partial Phase I Bond Release. The evaluation of the bond release application included the bond release inspection, an office review of the permit requirements and regulatory criteria, and review of past inspection reports. The bond release inspection was conducted on May 11, 2016. Several items were reviewed by the Division during the technical evaluation of the bond release application before, during, and after the inspection, including: the post-mining topography and cross-sections of backfilled and graded areas. 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-09, 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-09 areas, elevation data provided in the SL-09 Bond Release application was compared to GPS data collected by the Division. Thirteen points were selected near the cross-sections provided with the SL-09 application as well as additional cross-sections created by the Division. These points were selected utilizing Exhibit 1 of the SL-09 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. The elevation at the base station was 7234.1’ on Trimble Yuma, which utilizes a projected coordinate system of UTM, NAD 83, Zone 13 North. In Colowyo’s coordinate system (UTM NAD 27 Colorado State Plane)