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12-8a-1997 8:58at-t FROIt ENG. vaES7 ELK h1INE 970 9295E~5Ei SEP-18-1997 12~dd HARbItt, ~pWSOr+ Page Fotlr Mr. TYotm Every Mountain Coal Company 601 36~ aa76 P.05 P. 5 t'tardirl9 lawsOn AS60t~ite9 1. Sinex these workings would collect water from a large surface arw of fraztwed rock and coal and then permit the water to flow unrestricted ttrrough a large open void to the area immediately behind the slide mass through the floor, it should significantly shorten the time required to deliver significant pore pressure to the back of the slide. This charaeterisvc should manifest itself as a more rapid response during wet years (or otherwise stated as increase in the acceleration rates during the fall and winter months reducing lag time liom thn onset of significant snow melt aetiviry). ~ 2. The storage of a large volume of water vithin the old workings should extend the time ova which wattt and high pore pressure is delivered to the back of the slide. Manifestation of this effect should show up as an extended duration of the period over which acceleration occurs (or otherwise stated as an increase in the accelera4on rate through the spring aAd into the ear]y summer). A review of the monitoring data does disclose that movements on many of the monitoring points have continued to steadily accelerate from year to year since monitoring began in 1993 and especially since 1995. We have included several plots of the monitoring data to visually present this information. This data also discloses that the acceleration is greaur during the winter and spring periods and to an extent during the fell seasons with mittimal acceleration over the summer periods. This behavior would tend to support the scenazio of the collection of a large volume of water and development of port pmssure in the old workings. In our opinion direct infiltration of rainwater and snow melt from the ground surface above the slide mass itself either does not contribute or contributes minimally to pore pressure causing movement along the slide plane. Wetting liont progression from the surface at a unit gradient is simply too slow to covet the full 75 to 1W feet of depth in a ~ single season and cannot produce the rapid response and short !erg time observed between the onset of snow melt and the acceleration of the slide movement. Therefore it is believed that the water and pore pressure responsible for accelerating slide movements is sourced in areas off the slide mass, higher on the mountain where exposed cracks and joints near outcrop azeas pccmit rapid infiltration into fractured rock and the fractured rock permits relatively rapid delivery of the watK to the base of the slide m:us under pressure. This same mechanism could apply to old warkiags which collect watu i'nrm the same jointed rock masses, from caal scams. and from tension cocks and rubbly zones above subsidence areas to deliver the water and excess pore pressures rapidly to the area lx:hirtd the slide. Both of rhea mechanisms are felt ro be potentially viable mechanisms for reactivating of the existing slide mass.