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Harding Lawson Associates <br />' September 14, 1995 <br />32640.5 <br />Mr. Norm Every <br />Mountain Coal Company <br />t Page 3 <br />The most effective design for mitigating [he present soil failure below the none portal access road is a polygon <br />' wedge, shaped soil buttress. The approximate soil buttress dimensions are 5 fee[ wide, I30 fee[ long and 75 feet <br />high along the gradient of [he slope (refer [o Figures 5 & 6cross-sectional view). The soil buttress will be <br />constructed from pit-run gravel which can be easily repaired if subsequent failures occur at this location. The <br />soil butvess will have a volume design of approximately IS00 +%- 200 cubic yards. Installation and construction <br />' of the buttress may be achieved within seven working days with heavy equipment. The approximate <br />construction cost is $40,000 to build the buttress. <br />' Temporary water runoff during construction of the buttress has been controlled by attaching a corrugated flexible <br />discharge hose [o [he damaged drain pipe extending from [he base of [he bin wall ([his task completed August <br />30, 1995). Overall drainage and erosion control will be established concurtently with conswc[ion. Two <br />' permanently established hand perforated 4 metal corrugated pipes will be placed in [he keyway and near the base <br />of the existing bin wall. The ke}~vay pipe will discharge along the western flank of the soil buttress while the <br />bin wall pipe will discharge along the eastern Flank of the soil buttress (refer to Figure 2). <br />' If you have any questions please call either Chazlie Rehn or Loren Jalbert at (S01) 363-4455. <br />Sincerely, <br />' ING L W N ASSOCIATES <br />;a~~~ <br />' Loren A.J bert <br />Proj E 'neer <br />' Charles C. Rehn, P.E. ~~ ` ", <br />u_~ „" <br />Principal Engineer ~ "- ~ ; <br />j _.~,,,- <br />LAJ/CCR/ms f `~. :~ <br />Enclosures '~•x-""`ir~ ~-.t'~ °' <br />