2011-08-09_REVISION - C1981019 (10)

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RULE 4 PERFORMANCE STANDARDS sandstone with a thickness of between 50 and 70 feet and is approximately 1,200 to 1,300 feet below the ground surface in the current and proposed mining areas of Colowyo. This is the only mapped and known continuous unit in the area of the CM. This sandstone has been noted as being an excellent marker bed for correlation work with the overlying coal seams. Geologic Structure Two major features, the Collom Syncline (on the north) and the Danforth Hills Anticline/Wilson Dome (to the south), control the primary geologic structure in the area of CM. All of the current and proposed mining areas are located between these structural features. There are two minor synclines on the eastern and western edge of the current and proposed mining areas known as the Elkhorn and Morgan synclines, respectively. (As noted above, this data and associated geologic maps can be found in the recent permit applications to DRMS). The current mining area is located on the south flank of the Collom Syncline. The axis of the Collom Syncline, located approximately 0.5 miles north of the north edge of the reclaimed East Pit, trends west - northwest (approximately N60 °W) with a slight dip in the axis to the west - northwest. The Collom Syncline is sub - parallel to the Axial Anticline to the north and the Danforth Hills Anticline on the south. The Collom Syncline is asymmetrical, with the north flank of the syncline steeply dipping (20 ° -40 °) to the south - southwest. The south flank dips to the north - northeast at around 10 °±5 °. Thus, due the geologic structure of the area, the coal seams and non -coal beds dip to the north - northeast at approximately 10 °. The dip of the rock on the eastern portion of the CM is partially controlled by the Elkhorn syncline located east of the CM. Although the rock still has a primary north component there is some dip to the east. In the middle of the South Taylor mining area, a structural high, an unnamed anticline, is present, which is an offshoot of the Danforth Hills anticline. This is associated with a small- unnamed syncline near the valley floor of the West Fork of Good Spring Creek. The anticline causes the rock to dip predominantly to the north and south. The proposed Collom mining area is located in a similar geologic setting as the current Colowyo mining area of the West Pit and the inactive East Pit. Hydrologic Conditions Based on the above discussion, the Colowyo active mining area and associated Colowyo properties are located on a topographic and structural high. This causes any surface or ground water to flow from a south to north direction due to slope and dip of the sediments. In addition, the topography, structure and erosional features in the area south of the permitted areas cause the top of the Iles formation (including the TCSS) and the bottom one -half of the Williams Fork to be exposed on both sides of Wilson Creek, above the valley floor. Bedrock Ground Water With respect to ground water monitoring of the Williams Fork, the current mined sequence of non -coal and coal beds in the West and South Taylor Pits are above any significant recharge source, i.e., surface water recharge to the bedrock in the valleys. This is because the bottoms of the current pits are at an elevation higher than the elevation of the surface water in the valleys. Precipitation in this area is less than 22 inches. (on average) per year. Evaporation rates approach 30 inches per year. Any surface water /precipitation on the topographic highs has to percolate through the clayey soils, prevalent in the area of the CM and Collom, into the underlying Collom - Rule 4, Page 18 Revision Date: 8/5/11 Revision No.: PR -03