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most practical method of dealing with this geologic condition is to minimize the <br /> exposure of the highwall geometry to mining personnel by initiating a mining cut <br /> at 90 degrees to strike and mining the material at a normal (perpendicular) angle <br /> to dip. Mining this way will also minimize over-size production and improve <br /> breakage via blasting at as high an angle (90) as possible to dip direction. <br /> 2) Photo #2 also shows the active mining face stable at vertical attitude and <br /> 40'height for purposes of mining (short term stability). The photo also shows a <br /> clay zone in the center of the photograph as well as the staining of the limestone <br /> marl by overlying and interbedded clay and siltstone members. <br /> 3) Photo #3 is a shot of the southern end of active pit area, first bench, showing the <br /> 35 degree dip angle of the limestone bed as well at the tendency for rock to fail <br /> along the exposed edge of the vertical highwall. <br /> All of the photos show salt placement at the face via evaporation as meteoric water <br /> percolates through the dipping limestone beds and is exposed to atmosphere at the mining <br /> face. While this supports the writer's assumption that eventually, the vertical face will <br /> undergo further de-stabilization over time, it is apparent that the time frame of this <br /> phenomena is relatively large compared to mining timetables. This should allow for <br /> mining to continue without major concern of mining face stability over the time frame <br /> appropriate for active mining activities. This is not intended to downplay the need for <br /> careful inspection of the condition of the mining face, especially the top edge of the face, <br /> before each and every intent to drill or work under or close to the edge of the mining <br /> benches. Moreover, the appearance of a stable vertical face over the past five years of <br /> exposure does not apply to final reclamation of the highwall zone. <br /> Summary and Conclusions <br /> At present, the Byzantine Quarries site does not display evidence of pending failure of <br /> highwall structures presently in place, nor do conditions warrant any change in original <br /> mine plan. The original minimum bench width specification of 48' has been followed <br /> and should continue, especially if and when upper benches are developed. The <br /> established protocol of bench inspection and edge stabilization should be continued to be <br /> used at this location, knowing that the mining face exposed along the direction of strike <br /> of the bedding (N10W-N30W) will likely produce loose slabs of rock from along the top <br /> edge of the mining face due to freeze and thaw and gravity, enhanced by the 35 degree <br /> dip of bedding. This condition can be partially mitigated by mining at perpendicular <br /> angles to the dip direction, at least minimizing the exposure miners to large loose rock <br /> along the face edge. In addition, a thorough cleaning of the leading edge of mining face <br /> prior to drilling along the face, as well as specific instruction to drillers to stay behind the <br /> first row of drill holes along the face may help to mitigate the structural limitations <br /> imposed by geology at this site. <br /> In the event that this operation is under consideration for closure within the next decade, <br /> the first and second benches can easily meet original 1.6 : 1 final over all slope by taking <br /> advantage of the N/S drainage channel exposed west of the mining face (behind and <br /> slightly above the current first bench elevation), that will allow for the entire removal of <br /> the second bench as it terminates in the natural drainage channel present due to tensional <br /> forces applied to the moderate to steeply dipping beds off of the Royal Gorge Uplift <br />