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-33- <br />connection within the faults and fractures between the coal seam and sources <br />of ground or surface water. <br />Fault and fracture controlled inflows have been noted and mapped in the U.S. <br />Steel Corporation Somerset Mine application (Exhibit EB-3366), the Western <br />Slope Carbon Hawk's Nest Mine permit application (Exhibit 2.04.7(1) or <br />W-1006), the Western Associated Coal, Blue Ribbon Mine application <br />(Exhibit T), and the Colorado Westmoreland Inc. Orchard Yalley Mine Annual <br />Hydrologic Reports. The Bear Mine has not had, nor is it currently <br />experiencing, any mine inflows. The Mt. Gunnison No. 1 Mine has encountered <br />only minor inflows from fractures in the Number 1 portal. A quantitative <br />assessment of surface water depletion through mine inflows is contained in the <br />surface water section of the Cumulative Hydrologic Impact Study. <br />Fractures that intercept surface water exhibit flows that are similar to those <br />of the intercepted surface water system. Ephemeral streams will produce a <br />seasonal flow in the fractures while perennial streams will flow constantly. <br />A quantitative assessment of surface water depletion through mine inflows is <br />contained in the surface water section of the Cumulative Hydrologic Impact <br />Study. <br />Subsidence Impacts on Ground Water Hydrology <br />Subsidence-induced modifications in ground water hydrology can develop changes <br />in recharge or alterations in aquifer characteristics. In zones of limited <br />overburden of competent strata, fracturing could intersect the ground surface <br />or the base of colluvial deposits and result in increased infiltration of <br />surface waters. Subsidence fractures have been studied extensively in the <br />North Fork by Dunrud (1976), but no positive relationship between subsidence <br />fractures and water storage has been established. This is largely <br />attributable to the fact that the Mesa Verde is a poor aquifer composed <br />largely of incompeterrt shales and sandstone and water storage is restricted to <br />buried channels. However, the BLM has stipulated that mining be limited to <br />partial extraction below colluvial-alluvial deposits at the Orchard Valley <br />Mine, to minimize subsidence impacts. <br />Increased fracturing or surface infiltration may also result in the <br />modification of spring and seep flow. Changes in the local potentiometric <br />surface could cause waters to migrate towards the underground workings or to <br />re-emerge in other locations. South of the North Fork of the Gunnison spring <br />water would probably re-emerge as discharge from the portal or as springs <br />along the subcrop or outcrop. Spring water in areas north of the North Fork <br />of the Gunnison could also be discharged from the portal, or it would permeate <br />the strata and gradually migrate north beneath the Grand Mesa. The two <br />largest operating underground mines in the North Fork Valley, Orchard Valley <br />and Mt. Gunnison No. 1, have extensive subsidence and hydrologic monitoring <br />programs in place to identify changes in spring flow. <br />Should waters from different sources mix as a result of subsidence fracturing, <br />modifications in ground water chemistry could be observed. No significant <br />changes n water chemistry are predicted, however, due to the small volumes of <br />ground w~ter present in the Mesa Yerde and the similarity in water chemistry <br />of individual aquifers. <br />