2012-02-16_REVISION - M2002020 (9)

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Aspect Mining Operation Disturbed Area (acres) A Slurry Wall Construction: 5,000 feet x 60 feet NA Site Grading: reservoir top bank following slurry wall construction; mining cell side slopes for added stability; selected areas of site to facilitate revegetation 15.5 B Overburden/Topsoil Placement: for internal haul roads, processing facility, and other miscellaneous areas 17 C Revegetation: complete for newly disturbed areas and partial for undisturbed and previously reclaimed areas. 40 Total Disturbed Area 72.5 and adjacent to the areas that will be backfilled. When sufficient material is available in the stockpile, the material will be backfilled into previously mined areas. Mining of the aggregate will progress down to the underlying bedrock. The bedrock material is rippable and, if necessary, may be excavated and used for reclamation. However, since reclamation will occur concurrently with mining, it is not anticipated that bedrock material will be stockpiled long -term prior to use. During mining, excavation will leave 3H:1 V slopes along the pit edges to facilitate final reclamation of reservoir slopes. No highwalls will be created from the mining operation. The aggregate material from the pit will be temporarily stockpiled within the pit or placed directly onto a conveyor system or haul truck for transport to the processing facility. During mining and reclamation activities, watering trucks for dust control will be used as needed. Since excavation will create 3H:1V slopes during mining, and no highwalls will be created, slope stability will not be a threat to adjacent properties. Therefore, setbacks from the mine pit top of slope to the proposed permit boundary or man -made structures not owned by the applicant will be 50 feet or greater. For setbacks closer than 50 feet, an agreement will obtained from the property owner or an engineering slope stability analysis will be performed. In order to gain an understanding of the extent of the mining operation, it is helpful to know the acres disturbed by different aspects of the mining operation. Each aspect is listed in the following table with associated disturbed area. The table illustrates a point in time where the mining disturbance could be at its maximum. It is assumed that the mining disturbance will be at its greatest during the beginning of the operation when the existing pit has just begun to be mined and the slurry wall has not been constructed. During this conservative scenario, most of the existing mining cell slopes are still at 3H:1 V, mining has created disturbances associated with internal haul roads, stockpiles, and the processing facility. For disturbed area estimates, it is assumed that the existing mining cell excavation depth (bottom of lake to top of adjacent land surface) is approximately 20 feet. Greeley 25 Avenue Site DRMS 112 Permit Amendment Application Page 8