2010-03-29_REVISION - C1981019 (3)

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• Collom expansion area must also address wildlife habitat. There are also references in the permit revision application, (Exhibit 10) to recreational use for big-game hunting, cropland and to coal exploration. The narrative in the site description and land use section should describe the existing land uses in the Collom 16,833 acre expansion area using the definitions of land use in Rule 1.04(71) with the details required by Rule 2.04.3. Colowyo Response: Section 2.04.3 has been amended Rule 2.04.6 - Geology Description 6. A generalized stratigraphic column of the Collom project area was provided in Exhibit 7, Item 21. It would be helpful to include a stratigraphic column showing the geologic group and formations above and below the coal seams to be mined in the Geology Description section of the permit as well. Pursuant to Rule 2.04.6(2) please add a generalized columnar section and reference it in the text under Section 2.04.6 Geology Description. Colowyo Response: The generalized stratigraphic column includes the geologic system, group and formation names and thickness of the sequence of rocks in the area of the Colowyo property to be impacted by mining. The main unit of interest is the Williams Fork Formation, which is the only mineable coal bearing unit in this area. The upper portion of the Williams Fork formation is eroded. There is no overlying unit above the Williams Fork Formation in the Colowyo area except for occasional Quaternary deposits and the alluvium/colluvium material located in the valley bottoms. The only continuous units in the Colowyo area (as defined by Colowyo) are included in the generalized stratigraphic section. These are the main coal seams, the Win' marker bed and the Trout Creek Sandstone member of the Iles Formation. As described in the Section 2.04.6, General Geology - "coarse grained sediments in the proposed Collom mining area are typified by channel and bay-fill sandstones. These are of limited extent and laterally discontinuous." This is also the case for the finer grained sediments in the area. The discontinuous nature of the sediments in the Collom mining area precludes the construction of a generalized columnar section. The geologic cross section data (included in a separate notebook) in the current submittal has geologic core and lithologic chip logs that illustrate the discontinuous nature of the sediments. The color logs of the most recent drill holes (C-04, C-05 and C-06) can be laid next to one another using the cross sections presented as Figures 2.04.6-5A through 2.04.6-SH. 0 Colowyo Mine C-1981-019 page 3 of 16 25 March 2010 Permit Revision 03 - Collom Permit Expansion