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Mining Plan <br />probably filled the cracks that allowed seepage to the remaining clay. Additionally, the slide <br />itself probably destroyed most of the slip zone and restabilization occurred. <br />The third portion of this figure shows what will remain after completion of mining, <br />primarily in Area 1vIV. As can be seen the removal of the limestone will also remove whatever <br />remains of the clay zone that caused the slippages. In effect, after mining, the major zone of <br />weakness (the 6-inch clay layer) will not be there so the extensive mass wasting that occurred <br />in the past cannot occur in the future. The only remaining clay zone will be beyond and <br />effectively downhill from the mining. During mining, slippage is not a serious problem because <br />of the orientation of the mining area relative to the location of the mining. The mining will <br />almost always be inside (west ot) the slip zone, if it exists, and therefore any slippage would <br />occur outside (east of) the mining. This is largely because the slip zone is near the surface of the <br />deposit and not deep inside it. Also, the mining process itself, as it nears any slip zone, <br />fragments the zone which reduces its ability to slip. <br />Most if not all of Area MV will be mined out and placed under reclamation before the <br />Hole is created. "therefore, the hazard of massive landslides into the Hole caused by major <br />slippage on clay zones within the formation will be significantly reduced. <br />Undercutting - As shown in Figure MP-8, located elsewhere in this exhibit, it is • <br />apparent that there will be a slight increase in the average slope gradient where the top of the <br />western edge of the Hole is found. This increase in average slope is from about a 1.5:1 above <br />the Hole to a 1.2: l within the Hole. These slope gradients are average slope gradients. The <br />actual slope will be composed of a series of benches made of vertical walls and level reclaimed <br />steps. Using a benched pattern such as this is far more stable than producing a continuous slope <br />of the same average gradient. A 1.2:1 average slope has been produced elsewhere in the past <br />mining of this quarry and no stability problems have ever occurred, other than the small scale <br />bench decay previously discussed. <br />It should be; noted that the entire rest of the mountain above the quarry has effectively <br />been severely undercut since about 1955 and no slippage has occurred. In that ease, the average <br />slope gradient change at the western edge of the quarry is from about a 2.25:1 above the quarry <br />to about a 1.2:1 to 1.4:1 below the boundary. Thus, the slope below the boundary is about 1.7 <br />times steeper than the slope above the boundary. The west side of the Hole will be about 1.25 <br />times steeper than the slope above the Hole. <br />Of course, whenever undercutting is done there is a hazard of slippage and that hazard <br />is fully recognized by the company. But it does not appear that such a slight increase in average • <br />Page 22 Pikeview Quarry Amendment Exhibit D <br />