2019-10-18_GENERAL DOCUMENTS - C1981022

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general terms of the approved reclamation plan. In order to evaluate the success of the work against specific criteria, data was collected during the SL-1 bond release inspection using an Unmanned Aerial Vehicle(UAV, or"drone")which would allow comparison of the as-built topography with the approved post-mining topography, shown on Map 2.05-M6 (Sheets 1 and 3) and Map 2.05-M7 (Sheets 1 and 2), and with the following commitment made in the text of Section 2.05.4 of the PAP: Final grading plans are designed to establish slope gradients consistent with upgradient natural slopes but not exceeding 2H.•I V, unless features of the natural topography dictate otherwise. The UAV data,together with supplemental measurements made on the ground, would also allow the reconstructed Elk Creek channel to be compared with the design in Exhibit 2.05-E3 of the PAP. Equipment used for the UAV survey was a DJI Phantom 4 Pro, which was flown using the Pix4D Capture app on an Apple IPad. Propeller Aeropoints were distributed around the survey area for use as ground control during data processing. A total of 186 overlapping images were collected during 3 flights, with an approximate average ground sampling distance of 5.5cm/pixel (although given the significant topographic relief the actual resolution varied around the site). The images were processed using Pix4D Mapper on a desktop PC(Intel Core i7-7700 CPU @ 3.60GHz, 32 GB RAM). The processing report is attached as Appendix 1 of this Findings document. Pix4D Mapper was used to generate a 2D orthoimage(a mosaic of the 186 raw images) and a 3D point cloud. The point cloud was classified initially using a standard classification algorithm, and then manually, to put points into the following groups: Ground, Road Surface, High Vegetation, Building and Human Made Object. A terrain mask was applied and a Digital Terrain Model (DTM)was generated using only points in the Ground and Road Surface groups. The DTM generation algorithm includes a smoothing parameter,therefore the resolution is reduced(in this case to—26cm/pixel). The DTM was imported into Global Mapper, which was used for all subsequent analysis. Figures generated during the analysis are presented in Appendix 2. Geographic data is projected in UTM NAD83 Zone 13N. Standard US units are used, so as to allow direct comparison with maps and figures from the PAP. Meanwhile, the map submitted with the SL-1 application was georeferenced using physical features identifiable on publicly available aerial imagery. The boundaries of the SL-1 parcels were digitized and saved as a .kmz file. Figure 1 shows the SL-1 parcels overlain on the 2D orthoimage. Figure 2 shows the DTM, shaded by elevation, which was used to generate contours at 1Oft intervals. C-1981-022,SL-1 Page 9 of 19