2013-12-05_GENERAL DOCUMENTS - C1981010

Home Browse Search

comparison. The detailed results of this analysis for each of the bond release parcels can be viewed in the August 15, 2013; May 16, 2013 and the April 24, 2012 inspection reports. Overall, it appears the bond release parcels have been backfilled and graded in accordance with the approved reclamation plan and the approved post mining topography. The grade and slope of the reclaimed parcels were comparable to the approved post mining topography. The highwalls have been reclaimed. Some rills and gullies were observed in the bond release parcels however significant erosional features and signs of instability were not observed during the bond release inspection. As vegetation established throughout the reclaimed parcels the amount of rills and gullies diminish. Large swales and depressions were not observed during the inspection of the bond release parcels. The graded parcels blend into adjacent regarded land. Each of these parcels drains into a reconstructed channel which discharges into a system of sediment ponds. See the Drainage Reconstruction section below for more details. Horse Gulch Fill Parcels K -A -10 and K -A -11 encompass the Horse Gulch fill, based on the analysis discussed above, it appears these parcels have been graded in accordance with the approved post mine topography. Appendix T of the permit includes the design of the fill. The Division evaluated the configuration of the fill and the drainage features constructed in conjunction with the fill. The west face of the fill does not exceed the approved 3:1 horizontal to vertical ratio slope. A 30 foot horizontal bench is constructed every 100 vertical feet of the fill. The fill is inspected by a qualified engineer every quarter. TMI has been submitting these quarterly fill inspection reports since construction on the fill began and significant stability and erosional features have not been identified. The under -drain was constructed and completed and certified during the first quarter of 2010. Based on the field inspections and engineer certifications provided as quarterly monitoring reports for the fill, the Horse Gulch Fill has been constructed as designed. Drainage Reconstruction In general, each of the SL 14 bond release parcels have a northeast or a northwest aspect with the exception of Parcels K -A -11 and K -A -10 which encompass the Horse Gulch Fill. Runoff from each parcel flows through a reconstructed drainage channel into sedimentation ponds prior to water discharging from the site. Several portions of permanent reconstructed drainage channels are located within the SL14 bond release parcels. Portions of the Middle Pyeatt drainage is within parcel A -B -10, portions of the Oak drainage is within parcel A -B -09 and portions of the East Pyeatt channel is within parcels F -A -12 and Z -A -12. As discussed above, a corridor has been delineated within these parcels and these corridors and reconstructed drainage channels have been excluded from the SL 14 bond release area given instabilities noticed during the bond release inspection. For the Horse Gulch Fill located in parcels K -A -11 and K -A -10, two rip -rap surface drains are located north and south of the face of the fill. They are known as the North Rip -Rap Channel and the South Rip -Rap Channel. Also, small "V" channels are constructed at the toe of each bench to drain water off the face of the fill to the side drains. These surface drainage features have been constructed in accordance with the approved designs and they are functioning and appeared stable during the inspection. Drainage from the Horse Gulch Fill discharges into the Horse Gulch sediment pond. Trapper Mine Page 8 December 2013 SL -14 Phase I Bond Release