Laserfiche WebLink
<br />Always, the thickness of the sliding block was about 20 to 30 feet and covered <br />surface areas of from 2 to 5 acres. <br />In the 1993 slippage, which was the largest prior to the current event, was <br />approximately 500,000 tons of rock about 25 feet thick slid about 400 to 500 feet <br />down the slope. This slide was the direct result of a combination of road building <br />across the land that slid and a prolonged, high volume rain about four months <br />before the slide. <br />Evaluation of the 1993 slide by geotechnical engineers concluded that if part <br />of the material that slid could be removed, most of the future hazard of additional <br />sliding would also be removed. A monitoring system was set up across the slide <br />and after removal of the upper several feet of the slide material, no subsequent <br />movement was observed. <br />The third portion of Fig. 5 shows what will remain after completion of mining, <br />• primarily in Area MV (slope below south and middle peaks). As can be seen, the <br />removal of the limestone also removed whatever remained of the clay zone that <br />caused the slippages. In effect, after mining, the major zone of weakness (the 6- <br />inch clay layer) was removed so the landslides that occurred in the past cannot <br />occur in the future. The only remaining portion of this clay zone was effectively <br />downhill during the subsequent mining. Most, if not all, of Area MV was mined out <br />and placed under reclamation before Area H was mined to create the current hole. <br />Therefore, the hazard of massive landslides into the "Hole" caused by major <br />slippage on this clay zone within this portion of the formation was significantly <br />reduced. <br />The actual slope was composed of a series of benches made of near vertical <br />walls and relatively level reclaimed steps, as shown on Fig. 6. A 1.2:1 average slope <br />has been produced elsewhere in the past mining of this quarry and no stability <br />problems occurred, other than the small scale bench decay. It should be noted that <br />the entire rest of the mountain above the quarry has effectively been severely <br />. undercut since about 1955 and no slippage occurred, except along the clay zone. <br />TRANSIT MIX AGGREGATES 15 <br />PIKEVIEW QUARRY SLOPE <br />CTLIT PROJECT NO. CS17341-125 <br />S:1CS17000-174991CS17341.0 0 011 2 512. ReportsICS1 7 341-1 2 5-R1-Final.doc