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• <br />• <br />• <br />Although there are certain advantages to mining in benches or lifts, that approach has one <br />serious problem that renders it essentially unworkable. This operation produces a wide variety of <br />products that require different qualities of sand. This variety can only be supplied if the sand is <br />mined to full depth along a working face. Mining in lifts is also more expensive. <br />The upper zones of the sand tend to be of a finer texture than the lower zones. Many <br />products require a mixture of particle sizes and this can only be supplied by mining the entire face at <br />once. If lifts were used there would be times when only the more coarse sand or more fine sand <br />would be mined. This would limit the kinds of products available for the consumer. Therefore, <br />except where safety determines the mining method, the entire depth of the sand will be worked at <br />one time. This also has some advantages for reclamation, the details of which are contained in <br />Exhibit E, Reclamation Plan. <br />Because the working face is often up to 90 feet in height, safety is a concern. Safety rules <br />require there be sufficient backup room For equipment that is mining a face. Where sufficient <br />backup room is not available (e.g. a narrow and deep hole) mining in lifts is necessary, although it <br />limits the products that can be produced at any one time. Therefore, the plan and sequencing has <br />been designed to avoid, as much as possible, mining in narrow, closed holes. <br />When mining the working face the wall is induced to slump by removing the slope support <br />using a front end loader. It requires very little work for a loader to induce the slump. When the wall <br />collapses it undergoes a reverse rotation rather than falling outward. This is because the wall, <br />although steep, is rarely vertical. The force vectors cause the top of the face to move downward <br />which pushes the bottom of the face outward. Because large masses of the sand cannot stand in an <br />overhang position it is not possible for the face to fall outward. After the collapse, the slope of the <br />face is somewhat steeper than the angle of repose. In a few days additional minor slumpage induced <br />by gravity creates a slope that is near the angle of repose. <br />MATERIAL PROCESSING: <br />Until the mining can make mom to move the processing plant from the west side of Academy <br />Boulevard to the east side, all processing will be done on the west side of Academy Boulevard. This <br />also reduces the distance wash fines must be pumped to complete the backfilling of the mined areas <br />on the west side of Academy. <br />The sand mined from the east side of Academy is hauled by truck through a tunnel under the <br />highway. This tunnel was built in 1972 when Academy Boulevard was extended south to join <br />Interstate 25 and has been in use ever since. <br />The plant will be moved to the east side after the backfilling on the west side of Academy is <br />completed and there is sufficient room on the east side of Academy to install the processing plant. <br />The clarifier may remain on the west side of Academy for a while longer, assuming the large tank is <br />still in good condition. If the tank is no longer in good condition the current tank will be removed <br />and a new tank built on the east side of Academy. If the clarifier tank remains on the west side of <br />Academy, sediment will be pumped to the east side of Academy for deposition in mined out areas. <br />Because it is not known exactly when the processing plant will be moved, it cannot be determined <br />exactly what will happen to the clarifier tank. The existing Clarifier tank may not last until the end <br />of the operation. Eventually a new tank will probably be needed and it would be installed on the <br />east side of the highway. <br />Easl of Academy <br />Mining Plan <br />Page D$ <br /> <br />