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t <br /> Materials Handling—Backfilling <br /> The site will be concurrently reclaimed to create the water storage reservoirs. Compaction for the reservoir side <br /> slopes at this site will be 95 percent(or better)standard proctor. When an area is completely mined out from grade <br /> to bedrock,each section approximately 800-foot-wide(or approximately 30 acres),will begin side slope construction <br /> while the next contiguous area or consecutive phase is beginning mining. Due to the floodway,there is limited space <br /> for stockpile placement at this site; by concurrently reclaiming,as an area is being prepared for mining,the <br /> overburden and topsoil can be stripped and immediately placed,or stockpiled in the previously mined area, limiting <br /> the material handling. It is estimated that within 6 months of an area being completely mined, it will be reclaimed. <br /> Backfilling of mining cells and other reclamation activities will be concurrent with mining. Topsoil,overburden, and <br /> non-marketable material excavated during mining will be used almost immediately. The only exception is during <br /> mining in the South cell (Phase 1)when topsoil and overburden will be used to create stockpiles along the north side <br /> of the cell for screening. Scrapers or haul trucks will be used to transport backfill material from the West cell (Phase <br /> 2), to the mined-out South cell for backfilling. Once the South cell is backfilled,the reserved topsoil and overburden <br /> will be used to create the finished grade prior to revegetation. Small temporary stockpiles may be created within or <br /> along the edge of the mining cells. When enough material is available in the stockpile,the material will be graded <br /> into the previously mined areas. Locations of topsoil and overburden stockpiles are shown on Exhibit C Mining <br /> Maps. <br /> Material may be imported for reclamation if on-site material is insufficient to create the reclaimed pond slopes and <br /> backfill the South cell. Prior to receiving any backfill material from outside the proposed permit area,the operator will <br /> provide notice with information that includes the backfill location and volume of off-site material to be used, an <br /> affidavit certifying that the material is clean and inert, an approximate time frame for backfilling with off-site material, <br /> and an update regarding material placement procedures and the final reclamation configuration. The on-site or off- <br /> site backfill material used will not contain known toxic or hazardous materials. <br /> All backfilling and grading will be done to stabilize the material and control erosion. Final grading and seeding will be <br /> done as soon as possible after backfilling,grading, and top soiling have been completed. The reclamation will not <br /> leave high walls on the property. In addition,there will be no auger holes,excavations, or shafts left on the property. <br /> Materials Handling-Grading <br /> Once backfill is placed to the approximate final grade for upland meadow or pond side slope creation,the area will be <br /> rough graded to establish final elevations, slopes, and transitions. Final grading will include addition of topsoil and <br /> surface preparation for revegetation. Special attention shall be given to transitions from reclaimed areas to <br /> undisturbed land. The final topography will not create new surface drainage directed onto adjacent properties. <br /> Reservoir side slopes will include the steepest reclaimed grades on the site, potentially as steep as 3HAV. The side <br /> slopes will be graded smooth to accommodate future maintenance of the lined reservoirs. The reclamation will not <br /> leave high walls on the property. <br /> Materials Handling—Slurry Wall <br /> The proposed slurry wall will provide a vertical low permeable cutoff between alluvial groundwater outside of mining <br /> cells and water stored below-grade inside of mining cells. Slurry walls(also known as slurry cutoff walls or slurry <br /> trenches) are non-structural liners constructed to provide a primary low permeability liner and isolate a mining cell <br /> from the existing alluvial aquifer. Soil-bentonite slurry walls are a very common type of liner constructed in Colorado. <br /> Construction of a soil-bentonite slurry wall liner is planned at the Tucson South Resource. Once the liners are <br /> Aggregate Industries Tucson South Resource <br /> Permit#M-2004-044112 Permit Amendment <br /> Page E-4 <br />