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- 14 - <br />material and the relatively slow rate of placement, we analyzed a <br />single case of the coal waste ban k to cover all conditions between end • <br />of construction and long term. <br />ESnbanlanent failure under seismic loadings may also occur bar <br />liquefaction of the embankment or foundation materials. Liquefaction <br />can occur in saturated, uniform sands of similar grain size materials <br />when the pore pressures caused by the seismic forces reduce the <br />effective stresses to the point where failure occurs. Limited studies <br />of the liquefaction potential of coal refuse by E. D'Appalonia <br />Consulting Engineers, Inc. (D'Appalonia) Personal Communication 1974) <br />cited in Engineering and Design Manual, Coal Refuse Disposal <br />Facilities, U. S. Department of the Interior Mining Enforcement and <br />Safety Administration have shown that compacted coarse refuse will not <br />liquefy. <br />Seepage: The stability analysis has been conducted assumig that no • <br />phreatic surface will form within the coal refuse waste piles. 1t~e <br />moisture content of the refuse material is estimated to be between 108 <br />and 158 at the oompletirn of the washirg process. Zt~e moisture <br />intent will be further reduced by air drying during transportation <br />and spreading the coal refuse material in lifts on the disposal area. <br />We anticipate that the dewatering after the washing process and the <br />handling of the opal refuse material will result in a moisture content <br />which will be less than 108 in place. Therefore, in our opinion, <br />insufficient moisture will be available to develop a phreatic surface <br />within the coal refuse bank. The moisture will be firmly bonded to <br />the opal particles and not subject to significant gravity drainage. <br />• <br />