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T Technical Revision No. 80 September 12, 1997 Page 2 4. The estimated B-Seam outcrop outflow range of 0.2 to 2.4 acre-feet per year (0.1 to 1.5 gpm) is 0.1 percent to 1.4 percent of the average annual surface water and groundwater supply for the colluvial "wedge" (from the B-Seam outcrop down to the valley bottom) that could receive B-seam outcrop outflows, as discussed in response #21. 5. The yeaz-to-year, natural variation in surface water supply to the 30 acre (surface area) colluvial "wedge", is 140 acre-feet to 350 acre-feet per yeaz. Therefore, the potential variation in natural water supply of 210 acre-feet (350 acre-feet - 140 acre-feet = 210 acre- feet) from one year to the next is 2 to 3 orders of magnitude lazger than the projected B-Seam outflow of 0.2 to 2.4 acre-feet per year, as discussed in response #21. 6. Based on review of historic reports and aerial photographs, the majority of unstable areas are located above the D-Seam, or neariy 250 feet vertically above the B-Seam outcrop. The areas of instability that do extend down into the colluvial strip beneath the B-Seam are shallow "skin slides" or earth flows, mudflows, and/or debris flows, which flow over the surface of the colluvium, as discussed in response #21. MCC believes that it will be beneficial to meet with the Division to further discuss these PHC issues and MCC's responses. MCC would like to schedule a meeting on September 29, 1997. Sumoina and Aandline of Mine Inflow Water MCC is aware of the Division's position that, pursuant to Rule 4.05.16, it must pre-approve the dischazge of water into underground mine workings. MCC does not, however, agree with the Division's interpretation of this rule. In particular, MCC believes that the regulation requires prior approval to discharge water from the surface or from one underground mine into the workings of another underground mine. However, MCC believes that it is inconsistent with both the letter and the intent of the regulation to require prior approval for the routine management of water within a mine, including the movement of water from one part of the mine to another part of that same mine. Moreover, MCC does not believe the words "divert or otherwise discharge" apply to the routine operational practices of handling water in the mine, such as collecting and storing water in active or sealed underground workings within the mine, prior to discharge out of the mine. Because the NW Panels sealed sump does not involve final storage or disposition of surface water, nor water from another underground mine, and because the sumping of underground water (or seepage or evaporation therefrom) is not covered by the phrase "divert or otherwise discharge," MCC does not agree that prior Division approval was necessary for the NW Panels sealed sump, nor is it necessary for the NE Panels and Box Canyon Panels sealed sumps (which have not yet been mined or utilized as sumps). However, notwithstanding MCC's interpretation of this rule, and without waiving our right to assert this interpretation, MCC will continue to work with the Division on this PHC revision to address the most recent large inflows and the PHCs of utilizing mined areas within the West Elk Mine as large volume sumps.