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12-Bd-1997 8:56At-1 FR0t1 ENG. WEST ELK F11NE 970 9295L50 <br /> <br />Ua.~la9 Lawsw. AssxlaN~ <br />September 17. 1997 <br />Ivlr. Norm Every <br />Mountain Coal Company <br />West Elk Mine <br />P.0. Box 591 <br />Somerset. Colorado 84134 <br />RE: MCC Landslide MitiP,atioa Rceotnmeadatioas <br />The following report sutnmanzes the potentia! mitigation methods that could be used by <br />MCC on the active landslide to slow down the rate of movemcnt to previoa; background <br />rates. "Phis letter report wilt sern as a guide for MCC in making the linancial decisions <br />needed for this site. <br />1.0 INTRODUCTION <br /> <br />A review of existing monitoring dare over the last four years shows a disturbing pattern. <br />/'~ Although the buttress that was constructed in the Spring of 1997 effectively stopptd the <br />(V~~ landslide in the vicinity of the screening plant and thus is protecting these local critical <br />strocturt:s, an aaeletatmg but not exponential acceleration is noted in the monitoring data <br />at other facilities starling in 1995 with large stuficial movements observed in 1997. <br />Utv current data shows the lrngth of the landslide to be approximately 1000 feet in <br />length. Sheaz strength data of the native colluvial soils shows that total failure occurs <br />when the soil has strained to as little as 0.5% to an upper limit of t%. In other words, <br />when displacemrnt of the monitoring mirrors that are installed on critical structures shows <br />anywhere from 5 to 10 feet of total movement, a potential major displacement of critical <br />structures is likely. The scarp, which grew extensively in f997 to approximately halfway <br />down to the rue of the landslide, will continue to elongate in a north direction until it <br />reaches the tce of the slide. At this time, the landslide will rcleae with horizontal <br />potential movement of 50 feet or morn possibly based on past landslide know9edge and <br />stability analyxs. Obviously critical structure damage will occur in this event. <br />HLA has presented with this report potynomial craves that show total movement of the <br />landslide has leached 30 to as much as 70 percent of the allowable strain prior to litiltue <br />` ~ assuming movement began in 1992. Total failure of the upper portion'of the slide is <br />possible in 1998 while the? lower portion may be delayed to possibly the year 2000 if <br />normal climatic: conditions occur. However the effects of a far wetter than normal <br />winter/spring as may be associated with the predicted "El tdirto wear this winter may <br />have serious consequences to the operation az WENf. <br />This report will discuss information recently acquired concerning the character of the <br />existing landslide at the site of the ARCOiMountain Coal Company west Elk Minc <br />Engm~a~nq Ma X35 S°u[n 7°° Wear. Sul! +°7. Sent IJIY Gary. Uen l~tT lbeprorc (B°t) 369w+f! he9miK~. Iff°~17°7+~+6 <br />[nmm~mama~5eticaf <br />P. 2 <br />