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Mining Plan <br />• The height of the backwall is limited by the capabilities of the blasting. That is, the <br /> blasting process itself imposes limitations on the amount of variation that can be used in the <br /> backwall height. As a rule, blasting depth cannot be less than about 20 feet and still achieve the <br /> desired result in rock fracturing. On the other hand, going much over 30 feet can result in <br /> hazardous working conditions because of the height of the cliff. Figure MP-3 shows some <br /> variations that are possible by using various backwall heights. <br /> Ideally, a compromise point should be sought in the modeling to maximize resource <br /> recovery while still achieving a step width of not less than 20 to 25 feet and a maximum backfill <br /> depth of about 6 feet at the point where the backfill meets the backwall of the bench. Because <br /> mining by blasting is an inexact process, achieving the ideal may not always be possible, but <br /> coming as close as possible will be the goal. On occasion the rock may break differently than <br /> expected and steps may be produced that are a little wider or a little narrower than ideal, but <br /> rarely is this variation extreme as can be seen by examining width variability of benches <br /> produced in the past. <br /> Figure MP-4 shows the process of creating a bench and applying reclamation before <br /> completion of the bench. At the Snyder Quarry this procedure has been successfully used for <br />• several years and has resulted in a good reclamation topography. In essence, the sequence used <br />ill b <br />t <br />l <br />th <br />b <br />kf <br />ll <br />h <br />h <br />d <br />i <br />d <br />f <br />h <br />Th <br />if <br />d <br />th <br />b <br /> w <br />e <br />o p <br />ace <br />e <br />ac <br />i <br />on t <br />e step out to t <br />e <br />es <br />gne <br />e <br />or <br />enc <br />. <br />ge <br />at <br />us, <br />the step <br /> is to be 25 feet wide, backfill is placed against the backwall out to the 25 foot distance from the <br /> wall. Because there remains a large working area in front of the backfilled bench, this procedure <br /> allows a high degree of control over the shape and slope of the backfill material. <br /> Then topsoil, or whatever growth medium is used, can be spread on top of the backfill <br /> material and final grading implemented. If staining of the backwall is needed (see Enhanced <br /> Reclamation Plan in Exhibit E) that can be done before spreading the soil. Or, if weather <br /> conditions do not allow staining then, the soil can be spread and the final bench created with <br /> staining coming later but before seeding and planting. <br /> The final stage in the process, as shown on the figure, is to trim the bench at the edge <br /> of the backfilled portion. The trim point should not be within the backfill, but if desired, it can <br /> be a foot or two beyond the tce of the backfill. Whether some extra distance is left or not will <br /> be at the discretion of the operator and will be based upon past behavior of rock fracturing in <br /> this portion of the formation. If that particular area has tended to break in unexpected ways, <br /> leaving a small unbackfilled lip is advisable just in case the rock breaks back further than <br /> expected. <br />• <br />Pikeview Quarry Amendment Exhibit D Page 13 <br />