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_P2_ 2. Bear Coal Company, Inc. - Bear No. 1, 2, and 3 Mines, CMLRD File No. C-033-81 3. Colorado Westmoreland, Inc. -Orchard Valley Mine, CMLRD File No. C-038-83 4. U.S. Steel Corporation - Somerset Mines, CMLRD File No. C-022-81 5. Blue Ribbon Coal Co. - Blue Ribbon Mine, CMLRD File No. C-047-81 6. Western Slope Carbon - Hawk's Nest Mines, CMLRD File No. C-016-81 7. Terror Creek Company - Terror Creek Loadout, CMLRD File No. C-059-83. All of these coal mines have life-of-mine areas within a 247 square mile subwatershed of the 978 square mile North Fork of the Gunnison drainage basin. All mining operations in the general area are underground operations, with the exception of Terror Creek Loadout which is strictly a loading facility. The life-of-mine areas of the underground mines are plotted on Figure 2. ,In addition, the coal seams to be mined, the area of surface disturbance, the area to be undermined during the first five year permit period and the area to be undermined during the life-of-mine are tabulated in Table 1. This assessment is divided into the three major subsections: General Description of the Hydrologic Environment, Probable Hydrologic Consequences of the Bear Mine and Cumulative Hydrologic Impact Assessment. GENERAL BACKGROUND The Bear Mine lies on the southeast margin of the Piceance Basin. Sedimentary strata ranging from late Cretaceous to early Tertiary age, and dipping 3-5 degrees north to northeasterly, are exposed in the mine areas. Coal is to be produced from the Mesa Verde Formation, a 2,500-foot-thick sequence of beds overlain by the Ohio Creek Conglomerate and underlain by the Mancos Shale. The Mesa Verde Formation is composed of four members: the Rollins Sandstone, the Lower and Upper Coal members, and the Barren Member. The lowermost member of the Mesa Verde formation, the Rollins Sandstone, is a white to buff-colored, well-sorted, medium-grained sandstone, ranging from 150 feet to 300 feet thick in the permit area. The Lower Coal Member overlies the Rollins Sandstone and consists of interbedded sandstones, siltstones, coals, and shale. The unit averages 270 feet thick in the permit area and bears three significant coal seams--the A, 8, and C seams. A massive sandstone, 25 feet in thickness, lies at the top of the Lower Coal Member and separates it from the Upper Coal Member. The Upper Coal Member is approximately 220 feet thick, containing shales, siltstones, sandstones, and the D, E, and F coal seams.