2013-12-05_GENERAL DOCUMENTS - C1981010

Home Browse Search

address stability and safety concerns for mining within the slide area. As a result of the slide, Trapper devised a plan to backfill excess spoil from the K -Pit excavations and created a fill area known as the Horse Gulch Fill. Designs for the Horse Gulch fill are located in Appendix T of the permit. Horse Gulch Fill was designed to store 24.6 million BCY of excess spoil. The west face of the fill is not to exceed a I I horizontal to vertical ratio slope. Approximately a 30 foot horizontal bench will be constructed every 100 vertical feet of the fill. An under drain was to be constructed in accordance with the approved designs located in Appendix T of the permit. IV. OBSERVATIONS AND FINDINGS The bond release inspection was conducted on August 15, 2013. The Division had evaluated the backfilling and grading work completed on several of the SL14 parcels during previous inspections conducted on May 16, 2013 and April 24, 2012. Details of the Divisions observation during these inspections can be found in their respective inspection reports. The SL14 Bond Release Application Maps (Sheets 1 to 3) submitted by TMI depict the bond release area and the exclusion areas. Also, as a reference for this document; enclosed is Attachment 1, the SL14 bond Release Areas & Exclusion Area Map (Sheets 1 to 4) generated by the Division using the maps submitted with the application. Compliance with Approved Post Mining Topomphv The Division evaluated the reclamation parcels to determine if the affected areas have been backfilled and graded in accordance with the approved post mine topography. Reclamation of these parcels occurred in 2009 to 2012. The SL14 bond release block consists of many different reclamation parcels. The Division evaluated the backfilling and grading work completed on several of these parcels included in the SL14 bond release application during previous inspections (May 16, 2013 and April 24, 2012). To evaluate the SL14 bond release block for Phase 1 bond release, the Division compared the approved post mining topography (PMT) as depicted on Map M12 in the permit to the actual on the ground topography after backfilling and grading had occurred. Two maps submitted by Trapper depict the actual on the ground topography after backfilling and grading has occurred; the SL14 bond release map and the Annual Reclamation Report (ARR) maps in Appendix W of the permit which is updated every year through a technical revision. The topography of the 2012 ARR map and the SL 14 bond release map appear to be the exact same. During the field inspections, the Division confirmed the on- the- ground topography of the bond release parcels. Using ArcMap 10, the Division geo- referenced the approved PMT Maps; Map M 12, the SL 14 Bond Release Maps and /or the latest 2012 ARR Maps. These maps can overlay each other allowing for a visual comparison of the topography. The Division then placed transects through the reclamation parcels to be evaluated. Along each transect, multiple sample points were placed. The elevation of each of these points was interpolated from the PMT maps and the SL 14 maps and /or the 2012 ARR Maps. During the ground inspection, the Division walked each of these transects and logged the elevation at each sample point using a Trimble YUMA GPS unit. Many variables effect the precision of the elevations measured with the GPS unit, however the error in elevation is generally consistent throughout the site. A surveyed elevation point is located near the water tanks adjacent to the mine office. The elevation at this point was measured with the YUMA GPS unit and the difference of that measurement from the know elevation is used as a correction factor. Using Microsoft Excel®, the Division charted the PMT map elevation, SL14 /ARR map elevation and the on the ground measured elevation to create cross - sections from the transects for each reclamation parcel for an easy Trapper Mine Page 7 December 2013 SL -14 Phase I Bond Release