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• <br />• <br />• <br />H3.0 Corrective Measures <br />This section is an update of Section 3.0 of the "1997/98 Landslide Corrective Measures Report". This <br />section provides new information on corrective measures implemented in 1998 and 1999, and their effects <br />on the landslide. <br />To recap, during 1997 and 1998, the immediate, short-term approach to stabilization of the West Elk <br />Landslide was to slow landslide movement by using mechanical methods. First, an RCC buttress was <br />expanded to provide mass resistance at the toe of the landslide, then pins (micro-piles) were used to <br />intercept the slide plane and increase shear resistance, thereby slowing movement. These measures were <br />designed to stabilize the landslide enough to provide time to implement essential longer-tetra mitigation <br />strategies. The long-term approach is then to dewater the landslide: a method which requires greater time <br />to accomplish due to the slow nature in which the colluvium drains. <br />As mentioned, the essential, long-term approach to landslide stabilization is to remove the primary trigger <br />of landslide movement, groundwater within and around the slide mass. Beginning in 1998 and as part of <br />an ongoing effort into the future, dewa[ering the landslide is being accomplished using several methods <br />including: <br />• A series of deep, granulaz-filled, horizontal trenches. The trenches reduce build-up of water at the <br />head and carry water efficiently out of the slide, thus reducing saturation of slide mass. <br />• Stone columns at the head of the slide which attempt to collect water and drain it to a deep, underlying <br />cobble layer. Stone columns that do not drain water to the cobble zone, but effectively collect water, <br />are periodically pumped to remove water from the slide. <br />• Lining of ponds and ditches, and active maintenance of this infrastructure to prevent surface <br />infiltration of water into the landslide. <br />Barr Engineering Company <br />PCDOCS1208220/CAK <br />July 37, 1999 <br />Appendix H <br />1999 Addendum to <br />7997/98 Landslide Corrective Measures Report <br />