2021-09-09_REVISION - M2004044 (10)

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standard proctor. When an area is completely mined out from grade to bedrock, each section approximately 800-foot-wide (or approximately 30 acres), will begin side slope construction while the next contiguous area or consecutive phase is beginning mining. Due to the floodway, there is limited space for stockpile placement at this site; by concurrently reclaiming, as an area is being prepared for mining, the overburden and topsoil can be stripped and immediately placed, or stockpiled in the previously mined area, limiting the material handling. It is estimated that within 6 months of an area being completely mined, it will be reclaimed. Backfilling of mining cells and other reclamation activities will be concurrent with mining. Topsoil, overburden, and non-marketable material excavated during mining will be used almost immediately. The reserved topsoil and overburden will be used to create the finished grade prior to revegetation. Small temporary stockpiles may be created within or along the edge of the mining cells. When enough material is available in the stockpile, the material will be graded into the previously mined areas. Locations of topsoil and overburden stockpiles are shown on Exhibit C Mining Maps. Material may be imported for reclamation if on-site material is insufficient to create the reclaimed pond slopes. Prior to receiving any backfill material from outside the proposed permit area, the operator will provide notice with information that includes the backfill location and volume of off-site material to be used, an affidavit certifying that the material is clean and inert, an approximate time frame for backfilling with off-site material, and an update regarding material placement procedures and the final reclamation configuration. The on-site or offsite backfill material used will not contain known toxic or hazardous materials. All backfilling and grading will be done to stabilize the material and control erosion. Final grading and seeding will be done as soon as possible after backfilling, grading, and top soiling have been completed. The reclamation will not leave high walls on the property. In addition, there will be no auger holes, excavations, or shafts left on the property. Materials Handling— Grading Once backfill is placed to the approximate final grade for upland meadow, pond side slope creation, or agricultural reclamation; the area will be rough graded to establish final elevations, slopes, and transitions. Final grading will include addition of topsoil and surface preparation for revegetation. Special attention shall be given to transitions from reclaimed areas to undisturbed land. The final topography will not create new surface drainage directed onto adjacent properties. Reservoir side slopes will include the steepest reclaimed grades on the site, potentially as steep as 3H:1 V. The side slopes will be graded smooth to accommodate future maintenance of the lined reservoirs. The reclamation will not leave high walls on the property. Materials Handling- Soil Bentonite Slurry Wall The proposed slurry wall will provide a vertical low permeable cutoff between alluvial groundwater outside of mining cells and water stored below-grade inside of mining cells. Slurry walls (also known as slurry cutoff walls) are non-structural liners constructed to provide a primary low permeability liner and isolate a mining cell from the existing alluvial Aggregate Industries—Tucson South Amendment—MLRB 112 Permit Application Exhibit E-4