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~OUHTAIH COAL ~ COMPANYL.L.C. West Elk Mine A Subsidiary of Arch Western Resources, LtC P O Box 591 5174 Highway 133 Somerset, CO 81434 (970)929-SOTS Fax (970) 929-5595 MCC Response: Section 11.3 of the November 2004 version of Exhibit 60B (particularly the first 4 paragraphs) includes a detailed discussion ojthe geologic and hydrologic reasons why no cracks are expected in the Dry Fork (including its tributaries) and Lick Creek drainages during longwall mining. The following major points of Section 11.3, which support Conclusion No. 3, and are discussed in paragraphs 2 through 4, are again summarized below: 1) No cracks were observed in detailed periodic observation traverses in [he alluvium of Sylvester Gulch and Deep Creek, where the overburden depth ranges from 800 to 1,050 feet The traverses were above solid coal (un-mined coal) boundaries where maximum displacement and strain is predicted 2) Also, no cracks or effects on streamJTow were observed above aroom-and~il[ar extraction area beneath the alluvium in the Bear Creek area. The overburden depth to the B Seam in this area ranges from 220 to 300 feet 3) To restate comment 94, point 2 (above), room-and~illar extraction mining historically was observed by the author to cause significantly greater surface cracking than does longwall mining. 4) Mr. Dunrud believes that subsidence observations and analyses made during the past nine years in the West Elk mining area---and also observations made while mapping for the USGS in the • Bear Creek area-are significantly more reliable than extrapolating findings from other coal mines in d~erent geologic, topographic, and hydrologic environments. Therefore, the expected ejjects on the alluvium in the South of Divide mining area should be based on observations in the West Elk and nearby U. S. Steel mining areas, which are the most logical and scientifically sound, site-specific data. 5) As discussed in the last paragraph of 11.3, it is recommended that streamflow and subsidence be measured-and periodic observations made prior to, during, and after mining above longwall mining panels El, E2, and E3-near the western part of the mining panels, where the overburden depth is at a minimum (375 to 400 feet) and subsidence ejjects (vertical displacement of 8.4 to 11.2 feet, tilt ranging from 1.3 to 6.4 percent, and strain ranging from 0.7 to 4.2 percent) are predicted to be at a maximum for the South ojDivide mining area Speciftc and valid concerns have been raised by the Colorado Division ojMinerals and Geology (DMG) concerning the potential for the creation of subsidence cracks beneath the alluvium in the Dry Fork drainage in the South of the Divide (SOD) area The concerns expressed by the DMG specifically relate to the diversion of the surface flows in Dry Fork and waters from the saturated alluvium in the canyon floor will be diverted into the subsurface through subsidence cracks related to the mining activities of Mountain Coal Company. Additional concerns were raised about ejjects of subsidence on water quality. Two specific examples ojsurface waters being diverted to the subsurface as the result of mining were referenced The first was related to the North Fork ojthe Right Fork of Miller Creek in Carbon County, Utah and the second was the Foidel Creek Mine in Colorado. The diversion of the Miller Creek f lows was documented in USGS Water Resources Investigations Report 95-4025. No specific documentation reference was given for the Foidel Creek incident MCC has reviewed the data presented in the North Fork of the Right Fork ojMiller Creek (NFRF Miller Creek) study and the data presented by Dunrud in PR 10 Exhibit 60B "Subsidence Evaluation 14