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<br />could utilize the larger, more competent sandstone boulder frag- <br />• menu in c•oc•k buttress type walls. Such construction could be <br />particularly effecti~~e if the alluvial gravel and cobble can be <br />utilized as backfill and fill construction. Drainage, both <br />surface and subsurface will be extremely important in the east <br />portion of the waste pile and construction of the access and <br />permanent roads. Subsurface drainage of the coal mine waste pile <br />should be carefully addressed. If large amounts of water are <br />added as the waste pile is being constructed or if area wide <br />precipitation is allowed to soak or saturate the waste pile <br />during and after construction, a significant number of perched <br />water tables may develop. It has been the experience of Lincoln <br />DeVoc•e, during the placement of exploration borings in existing <br />waste piles that, vertical permeability is very low relative to <br />• horizontal permeability in the individual waste strata or con- <br />struction lifts. In two instances, perched water tables were <br />encountered throughout the coal waste piles which were under <br />construction, requiring a reassessment of the stabilitq of the <br />waste bank mass. <br />We hope this letter has provided you <br />wit}r the information required. If questions arise or further <br />information, is needed, please feel free to contact Lincoln-DeVore <br />at auy time. `0~03'POY! <br />Respectfully submitted, ~ - <br />LINCOLN-DeVORE, INC. t W <br />by: Edward M~~Forris <br />Engineer/Western S <br />• LD Job +85688-J <br />8 <br />