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Memo to Dan Mathews National King Coal Response page 2 properties could be derived from the original storage structure' s simplistic analysis. If not, the appropriate material properties will need to be aetermined through laboratory analysis of appropriate refuse samples. A coal mine waste bank is required by Rule 4.10.4(2) to attain a static slope safety factor of at least 1 .5. The operator should be applauded for proposing to use the available waste material to achieve AOC. However, as I mentioned in our earlier meeting with the operator's representatives, this proposal entails exposure to the more stringent design and construction requirements of Rule 4.10. As an alternative, the temporary coal refuse storage structure could be modified to comply with 4.10 specifications. The coal refuse could then be permanently retained within that structure. Ground Subsidence MY final topic of comments deal with subsidence above the underground workings. The operator proposes to mine beneath Pine Gulch. You expressed concern with this proposal in your adequacy comments. As we also discussed in our earlier meeting with the operator's representatives, it will be necessary for the application to demonstrate that the probable hydrologic consequences of mining beneath Pine Gulch are acceptable, i .e. that material damage will not occur. Map C-12 appears to depict a preferred pillar and cross cut alignment and limited extraction plan, I assume for the intended purpose of controlling subsidence. The text should be amended to present a straightforward discussion of this control plan. In addition, a discussion of what sort of control techniques, if any, will be applied to preclude damage at locations of higher cover beneath Pine Gulch, should also be provided. This topic was discussed at our meeting but does not appear to have been included within the amended application. cc: Jim Stevens Mike Long JP/Jp Doc. No: 7960F