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-14- <br />Cumulative Hvdrolooic Imoact Studv -- Rules 2.05.6(3) and 2.07.6(2)(c) <br />This Cumulative Hydrologic Impact Study (CHIS) for the hydrologic basin of the <br />Coal Ridge No. 1 Mine has been prepared by the Colorado Mined Land Reclamation <br />Division (CMLRD) pursuant to Rule 2.07.6(2}(c). This CHIS assesses the <br />cumulative hydrologic impacts of all anticipated coal mining operations upon <br />the Colorado River Valley in the vicinity of the Coal Ridge No. 1 Mine. <br />Included in this assessment are the Eastside Mine and the proposed Coal Ridge <br />No. I Mine. These mines are both located along, or in close proximity to, the <br />Colorado A:iver. There are no other mines located in the general area, and no <br />other mines with impacts that have the potential to cumulatively add to the <br />effects of the Eastside and Coal Ridge No. 1 Mines to diminish or degrade the <br />hydrologic balance. The permit applications for these mines are located at <br />the offices of the Colorado Mined Land Reclamation Division, and are <br />designated as follows: <br />Eastside Coal Co., Inc.-- Eastside Mine, CMLRD File No. C-84-063 <br />New Castle Energy Corp.-- Coal Ridge No. 1 Underground Mine, CMLRD File <br />No. C-84-065 <br />These two mining operations are underground operations. The life-of-mine <br />areas of these mines are plotted on Figure 3. In addition, the area of <br />surface disturbance, the area to be undermined during the permit term, and the <br />area to be undermined during the life-of-mine are tabulated in Table 2. <br />The Coal Ridge No. 1 Mine and the Eastside Mine are both located along the <br />Grand Hogback Monocline. The Grand Hogback trends east-southeast in the area <br />with rock strata dipping to the south-southwest at an average of 50°. The <br />general direction of ground water movement is down dip. The life-of-mine <br />boundaries of the Eastside and Coal Ridge No 1 Mines are 7 miles apart along <br />strike. The coal seams to be mined are located within the lower section of <br />the Mesa Verde Group in the upper portion of the Iles Formation (E-seam) and <br />the lower portion of the Williams Fork Formation (Wheeler seam). These two <br />seams are :separated by 200 feet of interbedded shales, sandstones, siltstones, <br />and coal. The five-year operation plan of the Eastside Mine calls for mining <br />of the E-seam. The Coal Ridge No. 1 life-of-mine plan calls for mining of the <br />Wheeler se+~m. <br />The potential of the Mesa Verde to produce ground water within the area of <br />these miners is greatly limited by the extreme dip of the rock strata. An oil <br />and gas we11 drilled five miles southwest of the Eastside Mine encountered the <br />Wheeler coal at a depth of 7300 feet. Another well drilled approximately 6 <br />miles southwest of the Coal Ridge No. 1 Mine encountered the Wheeler seam at <br />approximately 9000 feet in depth (Tremain, 1983). <br />As previously stated in the Probable Hydrologic Consequences of the Coal Ridge <br />No. 1 Mine, there is little potential for cross-communication between strata <br />within the Mesa Verde Group due to the interbedded impermeable shales located <br />throughout the section. Also, in the vicinity of the mines, the Mesa Verde <br />Group is underlain and overlain by impermeable thick shale members of the <br />Mancos and Wasatch Formations respectively. Therefore, the ability of ground <br />water to migrate upward or downward through the section is extremely limited. <br />