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• 2.05.3 <br />In February, 1993, two slides occurred on the West Mine portal face-up cut slope. Both slides <br />occurred on the northern aspect and were thought to be the result of unusually high precipitation <br />levels and unusually moderate winter temperatures combining to develop saturated soil <br />conditions. No slide material was deposited offthe permit area, however, some topsoil <br />(approximately 40 yards) was lost as the shde crest progressed upslope into a previously <br />undisturbed area. <br />The following remediation measures were implemented to ensure that further loss of the topsoil <br />resource did not occur in association with the slide. A topsoil salvage buffer zone was established <br />in the area immediately adjacent to the slide crest (see Map No. 8-7). Topsoil was salvaged to a <br />minimum depth of 24" within this 20 foot wide buffer zone by raking with a track hoe or dozing <br />the material away from the slide crest. The topsoil is stored in a topsoil pile established adjacent <br />to the site (see Map No. 8-7). The topsoil pile is protected from water erosion by locating it <br />below the clean water diversion ditch at the West Mine. It is estimated that a total of 240 yards <br />of topsoil was salvaged. <br />Additional topsoil from within the buffer zone was salvaged where available to offset the previous <br />loss of topsoil. The topsoil which was lost to the slide was retrieved to the extent possible <br />without compromising operator safety. Any topsoil retrieved from the previous slide was also <br />• stockpiled. All stockpiled topsoil is protected from wind erosion by seeding with the approved <br />temporary seed mix and mulching. The stripped buffer zone area was also seeded and mulched. <br />The buffer zone will be monitored for any signs of further slope instability which might jeopazdize <br />additional topsoil. <br />The drainage channel on the portal face-up cut slope bench was reestablished to minimize <br />saturation and further movement of the unconsolidated material deposited on the bench as a result <br />of the slide. Material located on the bench was dozed downslope off of the bench and compacted <br />at the base of the cut on the portal level. <br />Little additional surface disturbance would have been required to face-up the proposed portals in <br />existing cutslopes along the portal level access road. Refer to the Golder Associates designs in <br />the Phase I and II Stability Analysis Appendices, Volume 6, for specific information regarding the <br />rock tunnels portals, cuts and fills construction. The rock tunnels were never constructed and will <br />not be constructed in the future. <br />The remaining structures are existing and as such, are discussed in Section 2.05.3(3)(b) Operation <br />Plan -Existing Structures. <br />See Maps 2-3, 6A-IA through H, 6A-2A, and 8A-8. <br />• <br />TR-32 <br />1~ - <br />9/99 <br />=/ s/oo <br />