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i• <br />I • <br />-. J <br />B-Seam Portal and StockQile <br />Page 1 of this reports states the preliminary geotechnica] engineering study concluded with <br />recommendations regarding cult and fill slope inclinations. The recommendations were [hat <br />slopes at the site should not be steeper than 2:I (horizontal to vertical} unless they are <br />constructed in very stiff to hazd clays above ground water where slopes as steep as 1.5:1 would <br />be acceptable. The slopes should be vegetated and any areas of ground water seepage will <br />require drainage blankets. Fill slopes should be no steeper than 2.5:1, although, slopes at 2:1 <br />would be acceptable in azeas where risk of erosion, creep and shallow slope failures could be <br />accommodated. Steeper fill slopes will require selected rock fill or mechanical stabilization. <br />The 1997 site construction utilized 1.SH:1 V cut slopes and 2H:1 V fill slopes with excellent <br />results. During the ensuing six years, there have been minor surficial slope failures but no major <br />problems. Based on this experience, the B-Seam portals were designed with the same cut and fill <br />slope inclinations. <br />Lambert and Associates evaluated the stability of the cut and fill slopes at the proposed B-Seam <br />portal bench and the fill slopes at the upper and lower stockpile azeas. The stability analyses <br />indicated a theoretical calculated factor of safety in excess of 1.5 for the fill slopes and 1.26 for <br />the portal bench excavation cut slope. <br />The Operator will determine the suitability of its proposed portal bench excavation cut slope as <br />soon as access is sufficient to characterize the site soils/rock, so that alternative portal bench <br />designs can be timely considered with site-specific material strengths. Site specific material <br />strength tests will be obtained and utilized to check the theoretical calculated factor of safety. <br />The portal B bench cut slope will be constructed 1.SH:1 V in stiff soils; 2.0 or more horizontal to <br />1 vertical in soft soils; 0.25 horizontal to 1 vertical in rock; or design theoretical factors of safety <br />of 1.3 or more if the cut slope is steeper. Mechanical stabilization may be utilized. <br />The design theoretical factor of safety for the fill slopes will be 1.3 or greater. Generally the fill <br />slopes of the portal bench and excess material stockpiles will be constructed no steeper than <br />2H:1V. Steeper fill slopes will be designed with a factor of safety of 1.3 or greater. Mechanical <br />stabilization may be utilized. <br />Run-off from the cut and fill slopes is contained in one of two sediment ponds, The slopes will <br />be vegetated as soon as possible after construction to minimize erosion. Erosion control blankets <br />or another similar product will be placed on steepened slopes to control erosion. <br />-6- <br />PR-~ <br />A PPRovE0 <br />S~ri~o3 <br />5/07/03 <br />