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• <br />• <br />i <br />• II <br />Bedrock at the site consists of shales, siltstones, <br />sandstones, and coal of the P1esa Verde Formation above <br />approximately elevation 6,875 and 1"lancos Shale below this <br />elevation. Rocks of the Mesa Verde Formation are exposed <br />in a number of rock cuts at the site. No substantial zone <br />of surface weathering which could act to reduce the strength <br />of this material near the bedrock surface has been observed. <br />Since tlancos Shale is generally susceptible to weathering, <br />no outcrops of this formation have been observed. The results <br />of our drilling program, in particular Boring B-3, suggest <br />that there may be a weathered zone at the top of the Mancos <br />Shale at least in some locations. However, since there is <br />penceally a substantial cover of colluvial soils over the <br />Plancos, the properties of this weathered layer, if it exists, <br />are not expected to have a significant effect on the stab- <br />ility of the waste rock pile. Although the extent of colluvial <br />soil cover above the weathered bedrock surfaca ~.s uncertain in <br />the immediate vicinity of Boring B-3, any surface weathering <br />of the Mancos Shale is not expected to influence the stab- <br />ility of the crushing and screening, level fill due to the <br />limited extent of the Mancos beneath the fill and the large <br />thickness of colluvial soil cover near the toe of the fill. <br />The 1`tancos does not directly underlie any other existing or <br />planned structures. <br />Existing fills Have been constructed from the colluvial <br />soils and bedrocks extracted from the cuts at the site. lde <br />understand that no significant amount of coal or mine trash <br />was incorporated into the fill; small amounts of coal which <br />were encountered are believed to be the result of excavation <br />of the outcrop oP some minor coal seams in the cuts. <br />Phe fills consist of sandy low plasticity clays and <br />„ravol-sand-c1.zy mixes (Cl., SC, and GC in the Unified Soil <br />Classi[ication System) with varying amounts of coal and rnck <br />- 1 1 - <br />GE6HVDR0 COHSULIING, INC. <br />