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t <br /> Site Reclamation Activity <br /> Page 4 <br /> This was done because significant settlement is expected due to ice <br /> buildup in the hole before filling. As it melts, the area will <br /> subside and the stockpiled material will be used for filling back <br /> to grade. The capping layer was only placed over the area not <br /> expected to subside. The areas where the open pit waste was <br /> stockpiled have been contoured and the topsoil that was stripped <br /> from the borrow area was respread over the borrow area slope. This <br /> slope was seeded in September , 1992 with the "Alpine Mix" (seed mix <br /> is included in the Appendix) in the reclamation plan for this area. <br /> The seeded area was covered with 2 tons/acre of hay mulch. <br /> Additional work in the Sunnyside Basin area consisted of: <br /> 1) removal of the half culvert in the rock trench. The culvert <br /> was removed and the bottom of the trench in the area of the <br /> culvert was sealed with a compacted clay layer . This area was <br /> an area of subsidence that had been previously backfilled. <br /> Monitoring over the last several years has shown the backfill <br /> to be stable. <br /> 2) drilling for definition of the rock-overburden contact <br /> on the northwest side of the hole. A test section of ditch <br /> was dug to determine if groundwater was flowing on this <br /> contact in order to evaluate the potential of intercepting <br /> groundwater flow into the Lake Emma hole. Flow was <br /> encountered although a quantity evaluation will be made again <br /> in early summer , 1993 . A TR (TR-15) was submitted to include <br /> an open perimeter ditch or subsurface drain around the hole <br /> based on field evaluations. The excavated material from the <br /> ditch was used to reduce the highwall in the Sunnyside Pit or <br /> spread uphill of the ditch. Final form or existence at all of <br /> a perimeter ditch or subsurface drain will depend on TR <br /> approval and field evaluation of potential effectiveness. <br /> Monitoring -of the subsidence points above the open pit highwalls <br /> was performed . The results are in the Appendix and show no <br /> significant changes. <br /> Planned activity for 1993 includes: <br /> 1 ) backfilling of the test ditch section discussed above or <br /> completion of construction for interception/diversion of <br /> groundwater along the test section. <br /> 2) possible expansion of the interception/diversion to cover a <br /> larger proportion of the Lake Emma hole perimeter . <br /> 3 ) refilling of any subsidence of the Lake Emma backfill. <br /> 4) maintenance of the seeded areas and monitoring for growth , <br /> etc. <br /> 5) monitoring the subsidence points above the open pits if <br /> reclamation is not complete. <br />