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-15- <br />IX. PROBABLE HYDROLOGIC CONSEQUENCES OF MINING AND CUMULATIVE HYDROLOGIC <br />rnno nrr criinv oni rc ~ nr c ~ ..,a ~ m c ~ .. <br />This Cumulative Hydrologic Impact Study (CRIB) for the drainage basin <br />of the North Fork of the Gunnison River has been prepared by the <br />Colorado Mined Land Reclamation Division (CMLRD) pursuant to Rule <br />2.07.6(2)(c). This CHIS assesses the probable cumulative hydrologic <br />impacts of all anticipated coal mining operations upon the general area <br />of the North Fork of the Gunnison River Valley. Included in this <br />assessment are all existing coal mines and those proposed coal mines <br />for which permit applications have been submitted to the Division. <br />This study has been prepared using information and analyses contained <br />in the Mt. Gunnison Mine permit application, information and analyses <br />contained in other permit applications for mines located in the general <br />area and other available information including site visitation by <br />members of the Division staff. <br />Coal mining operations in the study area include: <br />West Elk Coal - Mt. Gunnison No. 1 Mine, CMLRD File No. C-007-80 <br />2. Bear Coal Company, Inc. - Bear No. 1, 2, and 3 Mines, CMLRD File <br />No. C-033-81 <br />3. Colorado Westmoreland - Orchard Valley Mine, CMLRD File No. C-038-83 <br />4. U.S. Steel - Somerset Mines, CMLRD File No. C-022-81 <br />5. Blue Ribbon Coal Co. - Blue Ribbon Mine, CMLRD File No. C-047-81 <br />6. Western Slope Carbon - Hawk's Nest Mines, CMLRD File No. C-016-81 <br />All of these coal mines have life-of-mine areas within a 247 square <br />mile subwatershed of the 978 square mile North Fork of the Gunnison <br />drainage basin. <br />All mining operations in the general area are underground operations. The <br />life-of-mine areas of these mines are plotted on Figure 2. In addition, the <br />coal seams to be mined, the area of surface disturbance, the area to be <br />undermined during the first 5-year permit period and the area to be undermined <br />during the life-of-mine are tabulated in Table 1. This assessment is divided <br />into the three major subsections: General Description of the Hydrologic <br />Environment, Probable Hydrologic Consequences of the Mt. Gunnison No.l Mine <br />and Cumulative Hydrologic Impact Assessment. <br />GENERAL BACKGROUND <br />The Mt. Gunnison No. 1 Mine lies on the southeast margin of the <br />Piceance Basin. Sediments ranging from late Cretaceous to early <br />Tertiary age, and dipping 3-5 degrees north to northeasterly, are <br />exposed in the mine areas. Structural-Stratigraphic cross sections are <br />