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2009-04-02_REVISION - C1981010
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2009-04-02_REVISION - C1981010
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Entry Properties
Last modified
8/24/2016 3:45:08 PM
Creation date
7/21/2009 9:33:32 AM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1981010
IBM Index Class Name
Revision
Doc Date
4/2/2009
Doc Name
Revised Pages from Letter dated 3/13/09
Type & Sequence
PR6
Media Type
D
Archive
No
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• The fill area will be properly prepared and constructed as detailed in Agapito Associates, Inc.'s "Horse <br />Gulch Fill Stability Analysis." This report can be found in PR-6, Appendix T, and is dated December 2008. <br />The fill is constructed via dragline spoil from the K Ridge Pit, and TIE spoil. The dragline portion will be <br />constructed first through normal dragline spoiling. The T/E portion of the fill will be constructed in lifts from <br />the floor of Horse Gulch. Lifts will not exceed 100 vertical feet, and will typically be 25 to 50 vertical feet. <br />In general, these lifts will be placed from the outside toward the center. A suitable berm will be <br />constructed at dump points, allowing end dumps to back up to the edge of the fill, and dump. As <br />conditions require, and more likely with increased lift height, trucks may dump short of the berm, and use <br />of a dozer to push the material to the lift edge will be required. <br />The West face of the fill will have an overall slope not to exceed 3HAV. A 30 foot horizontal bench will be <br />constructed every 100 vertical feet. This will promote drainage of runoff at velocities low enough to <br />prevent cutting the face of the fill. Additionally, this will reduce the overall slope of the face to less than <br />3H A V. The final bench will be constructed at the 7570' level, and slopes at this point will reduce to 4HA V, <br />or less. Lifts will be placed to a maximum elevation of about 7740' and will tie into the existing ridgeline. <br />The profile of this head of hollow fill will slope downward from this point, and will remain lower than the <br />existing ridgeline. <br />Drainage is an important consideration in the design of this head of hollow fill. An underdrain will be <br />constructed as specified in AAI's "Horse Gulch Fill Stability Analysis" (Appendix T) to promote drainage <br />from within the fill. Surface water diversions are depicted in Figure T-1, Appendix T. <br />Lifts will be constructed to promote drainage, and reduce the ability of water to stand on the surface. This <br />will reduce the amount of infiltration into the fill. Where appropriate, best available construction practices <br />will be used to prevent fine material from entering the underdrain. <br />• This head of hollow fill will be left as a permanent feature because it is an excess spoil fill. As such, the fill <br />will be retopsoiled, and planted in permanent vegetation compatible with the planned post mining land use <br />of Rangeland and Wildlife Habitat. <br />K/G Pit Buttress Area <br />Geotechnical review of the K-Pit has indicated the construction of a buttress to be necessary for safe <br />mining operations, and long-term stability of the area. The need for a buttress is a direct result of the <br />landslide in the K/G Pit area that occurred in October of 2006. <br />The area to be filled will be properly prepared and constructed, in accordance with Agapito Associates, <br />Inc.'s "K-Pit Buttress Fill Stability Analysis" from December 2008. A copy of this document is included in <br />Appendix T. <br />The buttress will be constructed in lifts from the existing topography. Lifts will not exceed 100 vertical feet, <br />and will typically be 25 to 50 vertical feet. In general, these lifts will be placed from the outside toward the <br />center by a Truck/Excavator fleet. A suitable berm will be constructed at dump points, allowing end <br />dumps to back to the edge of the fill. As conditions require, and more likely with increased lift height, <br />trucks may dump short of the berm, and use of a dozer to push the material to the lift edge will be <br />required. <br />The slopes of the fill are planned at 3HAV. It will be contoured to blend with existing topography. Lifts <br />will be constructed to promote drainage and reduce the ability of water to stand on the surface. This will <br />minimize the amount of infiltration into the fill. <br />• <br />3-40a <br />Revision: P r-- b <br />Approved-
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