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Mr. Martin Azcarraga June 19,2000 Page 2 of 4 The closest man-made structure to the mining area is a catch basin structure located at the northwest comer of the property, which is owned by the Grand Junction Drainage District. Minine Description The sand and gravel will be mined by a progressive, open pit method. Reclamation for the site will consist of backfi{ling the site to approximate pre-mining grades. A lazge amount of import fill will be required, in addition to the existing overburden material, to accomplish this task. As mining operations occur at the sand and gravel highwall, overburden stripped immediately in front of this highwall will be used as backfill material behind areas that were previously mined. The maximum depth of the mining operations is estimated at 32-ft below the existing ground surface. The "excavation area", which consists of the sand and gravel highwall, the overburden highwall, and backfill azea will be limited to a maximum of three acres at any one time. Groundwater at the site is approximately 12-ft below the ground surface. Therefore, dewatering operations will be required for sand and gravel highwall mining, and backfill placement. Damages to offsite man-made structures, which could occur as a result of the sand and gravel mining operations, include: • Landslide /Slope failures from the sand, gravel, and overburden highwall; • Groundwater Impacts; • Drainage Impacts; • Compaction /Vibration Impacts; • Motor Vehicle accidents; Landslide / Slooe Failures The total mining depth is expected to be approximately 32-ft below the existing ground surface. The closest man-made structure, a catch basin structure, is located 30 feet from the mining area. Overburden removal at the site consists of a silty-clay material approximately 12-ft in depth. The silty clay soils in the Appleton Wash and Canning Factory Drain, located north of the proposed site, provide a good indication of the expected slope stability of the silty clay material. These drainages have numerous areas of near vertical faces and no areas of slope failures were observed, except for a localized failure in the Canning Factory Drain, located near the northeast corner of the site. A slope failure occurring at this location appears to be the result of a crushed drainage/irrigation culvert. Water draining through this culvert has leaked out into the surrounding bank area and saturating it to a point where small-localized failures along the bank are present. All of the overburden is anticipated to be located above the groundwater table. A slope/landslide failure of this 12-ft highwall area large enough to damage any offsite man-made structure is unlikely.