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Page 2 Mr. Tom Pike March 14, 1980 being discharged. Without a sump down dip of the slurry fill to drain water by gravity, a certain amount of water loss can be expected with the slurry operation. The operator should attempt to quantify the amount of water which will remain in the slurry filled sections of the mine should the susp system not be implemen*_ed. The slurry filled plan calls for filling approximately half of the main slope sections of the Hawks Nest West Mine. The vertical drop from the mid paint in the main slope to the lower-most point is approximately eighty feet. There ore, eighty feet of head can be expected to develop against the barrier pillar at the northernmost down-dip portion of the Hawks Nest (Jest Mi_ne~after the slum fill is complete. The long wall mining section has preceded 400 feet further north than the lower most point in the Hawks Nest [Jest Pfine. If any of the coal in the barrier pillar betcaeen the long wall section and Hawks Nest West Mine wire removed, drilling would have to proceed ahead of the mining operation. Water would then be removed from the Hawks Nest West 4fine which had accumulated in thy. slurry filling operation thru the long wall section. Mining has occurred • to the east and to the west of the main slope section to be filled r+ith slurry waste in the Hawks Nest West Pline. These sections have been sealed off accord- ing to Mine Safety and Health Regulations, however, the exact structure of the seals is not available in our application materials. Z understand th_t `iSN_a has been considering the design of the bulk head seals to be used by Western Slope Carbon in sealing off the slurry filled areas of the west mine. I believe these designs are properly in the domain of the Mire Safety and Health Administration as they relate more to safety than to environmental considerations. Another consideration related to safety may be the possibility of roof cave-ins during the active slurry fill operations which could displace valuaes of water associated with the slurry fill, rather explosively. For this reason the slurry fill operation should be supervised very closely by mine safety inspectors. From the environmental standpoint, the slurry fill system should not alter the existing hydrologic balance in any fundamental way. The processes of salt loading which occur naturally as water comes in contact with sedimentary formations be dramatically accelerated in the slurr}• system, since water would be ea-pose3 to saline materials with far greater surface area than in their natural states. Residual ground water left behind in the slurry fill will undoubtedly contain higher total dissolved solids levels than unaffected groun3 waters iu the same formations. This would be of concern if, for some reason, long wall ;.ini:.g oper- ation resulted in the necessity of bringing these residual ground waters back to the surface where they may enter the surface water forces. Along the sane lines, if underground mining is to occut in lower coal seals (i.e. the wi'.d seam and B seam) the possibility of residual ground water from the slurry back • fill of perculating down into the lower coal mining sections should be z-:alyxed very carefully. I think conditions in the lower coal seams might be rerz diifi- - cult.