2013-10-07_REVISION - C1981025 (8)

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Most faults along the Grand Hogback are perpendicular to the strike of the strata and trend east- west. The faults in the area of the mines are low displacement normal faults. The displacements of faults increase in faults located south of the mines. Sedimentary rock units within the permit and adjacent areas of the mines range in age from Pennsylvanian to Tertiary Formation. The formations, in ascending order, are the Maroon Formation, Entrada Formation, Morrison Formation, Dakota Sandstone, Mancos Shale, Iles Formation, Williams Fork Formation, and Wasatch Formation. The most significant sandstones and coals in the permit and adjacent areas of the mines are contained in the lies and Williams Fork Formations. The mined resources included the A seam and the Anderson seam. The A seam is seven to ten feet thick and lies above the Rollins Sandstone of the Iles Formation. It is 3,300 to 3,500 feet below the ground surface. The Anderson seam is nine to ten feet thick and lies approximately 2,400 feet below the ground surface. Ground Water Hydrology- There are three majorbedrock aquifers within the mine area: the Upper Sandstone, the Middle Sandstone, and the Rollins Sandstone. These are regional aquifers and are relatively thick and laterally extensive throughout the mine area. The Rollins Sandstone is below the lowest coal seam that was mined (A seam) and is within the Iles Formation. The A coal seam, the Middle Sandstone and the Upper Sandstone all lie within the Bowie member of the Williams Fork Formation. The Anderson coal seam lies within the Paonia member. The North Thompson Creek No. 1 Mine is in the A seam, while the No. 3 Mine is in the Anderson seam. In addition to the sandstone aquifers mentioned above, several other potential sandstone aquifers exist above and below the Anderson seam. However, these sandstones are thin and laterally discontinuous. A shallow and discontinuous alluvial aquifer exists on portions of the permit area adjacent to North Thompson Creek. The alluvial aquifer along the Roaring Fork River has good quality water. Surface Water Hydrology- Two perennial streams are in the permit area: North Thompson Creek and Middle Thompson Creek. The watersheds of both drainages are very similar. Elevation ranges from 7,600 feet at the mine site to over 11,000 feet in the headwater. Stream flow on North Thompson and Middle Thompson Creeks is derived primarily from snowmelt. Flows resulting from snowmelt typically have a gradual rise, moderate peak, lengthy recession and large volume. The peak occurs in May or June, while base flow is in late fall or winter. All surface disturbances, coal preparation structures and adits are in the North Thompson Creek drainage. The underground workings for the No. 3 Mine are entirely within the North Thompson Creek drainage. The adit for the No. 1 Mine is in the North Thompson Creek drainage, but the 4