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' Battle Mountain Ruourcea, Inc. .112 Pcrmit Modification ' D.2.6 ~ InFlows The South wall of the West Pit has experienced some seepage toward and into the pit through the surface alluvium and the Santa Fe Conglo(rlerate units. The seepage is actively managed through a series of collection sumps ko prevent pit slope ' deterioration. . ' The approved permit contains a discussion of additional measures that may be necessary to ensure long-term stability of the south wall of the V~'est Pit. Measures included dewatering of the Santa Fe Conglomerate through a series of horizontal drains; the construction of a rock buttress composed of inter~urden waste rock materials; and installation of a low permeability barrier, such as ~ slurry wall, to cut ' off seepage through the alluvium. This permit modification provides for partial backfilling of the West Pit, which eliminates the need for a buttress. Pursuant to th approved plan, ongoing seepage management will continue during mining and until ' backfilling in the south wall area is completed. Ongoing seepa4ge monitoring and evaluation will indicate the need for horizontal drains or a sltJtry wall to ensure stability during operations and through completion of reclamatiop. ' Y D.3 Waste Rock DisyQsa_1 tom'-~ ~ ~ D.3.1 General ~~. ~ x` ~`o~o~ Six waste rock disposal azeas have been approved as pert of the San Luis Project permit. The proposed permit modification will affect thr of the waste rock disposal areas. ac 1 1 f the West Pit will eliminate a need for disposal ' of approximate 564,000 to waste rock outside of the mine pit limits. This plan will eliminate Waste Rock Disposal Area A, and significantib reduce the size of ' the South Waste Rock Disposal Area. Temporary stockpiling pf 864,000 tons of waste rock on Waste Rock Disposal Area B is planned prior to its leventuai placement ' as backfill in the West Pit after completion of mining. The waste rock disposal facilities at San Luis have ~een designed and constructed in accordance with previously approved design specifications. The waste piles have been designed with slope angles of 33.5 degrees ~r 1.5 horizontal:l vertical (1.SH:1~, with a 75 ft setback (or bench) between eadh lift. In practice, ' the waste rock is end-dumped in 50-ft lifts at the material's a~gle of repose. At reclamation, the outslopes at each lift will be regraded and a benches will be ' aY DJ lest o.