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June 24, 1985 3 853-2038 <br />site inspection, extends to State 3Tighway 133. We understand <br />that the State Highway Department routinely excavates the toe of <br />this slide as it encroaches on the highway. This landslide has <br />caused substantial damage to the conveyor portal, and extends to <br />an elevation in excess of 100 feet above State Ilighway 133. <br />A third, smaller landslide lies immediately above the substation <br />to the west of the switching shed. This landslide currently <br />shows only small deformation. <br />The presence of surface-water flows and ground-water seeps within <br />the active landslide areas and their high rates of movement dur- <br />ing the spring season indicates that the landslide movements are <br />related to an increase in ground-water presures during spring <br />runoff. This is supported by observations by mine personnel that <br />landslide deformations were minor during operation of the East <br />Hawk Mine when the surface-water diversion system was maintained <br />in good condition. <br />During our site inspection, we saw no evidence that current land- <br />slide deformations are a result of subsidence due to coal extrac- <br />tion. This is consistent with our understanding of the mining <br />operations in the immediate vicinity of the landslides; mine <br />personnel indicated that pillars were robbed from this area dur- <br />ing the 1940's. <br />POTENTIAL DAMAGE FROM EXISTING LANDSLIDES <br />The switching shed landslide has already caused substantial <br />damage to this structure. Landslide deformations have also <br />severed underground power cables into the switching shed and <br />broken power poles in the vicinity. This slide is currently <br />quite active with indications of large recent deformations. We <br />Golder Associates <br />