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• west of TH-3 and at an elevation of about 6865. This is about 15 feet above <br />the water elevation measured in the boring and pits near TH-3. <br />Based on the results of the exploration, we do not believe a <br />groundwater "table" exists below the base of the RDA. The water found in the <br />lower portion of the valley, near the flow line is considered to be perched <br />water of limited extent. The remaining borings did not indicate water at <br />depths below the proposed RDA which will influence stability. Considering <br />the permeability of the coal waste we also believe it unlikely that a consistent <br />zone of saturation of significant height will develop within the pile. A toe drain <br />was designed to provide an outlet for water which infiltrates the pile. The <br />waste will not be placed in a saturated condition. We analyzed two water <br />• level conditions to check the senskivity of the pile to the presence of water, <br />a low water level condition with water about 5 feet above the base of the pile <br />and a high water level condition with water present in the pile to a height of <br />. about one-half the pile height at the crest. <br />Results of Stability Analysis. The results of the stability analysis are <br /> <br />presented in Appendix C. The results are grouped in Table C-1 and are <br />discussed below. <br />Group 1 In this group the normal strength values were used. We believe <br />this represents a conservative estimate of conditions based upon <br />the laboratory test results for this investigation. <br /> <br />• <br />Case 1A represents a static condition without groundwater. <br />Infinite slope conditions control for this model with a calculated <br />factor of safety of 2.0. The computer models verified that deeper <br />failure circles result in a factor of safety on the order of 2.1 (Fig. <br />C-1 ). <br />14 <br /> <br />