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-40- <br />- subsidence-induced flows into the mines. <br />Faults and Fractures <br />Faults and fractures which cut the bedrock strata produce a localized <br />increase in secondary permeability within the strata. If the faults <br />and fractures do not become sealed by clays, they may become conduits <br />for the flow of ground and surface water. When encountered within the <br />mine, faults and fractures will dewater. The amount of water flowing <br />into the mine from these sources depends on porosity and permeability <br />of faults or fractures, and on the open vertical connection within the <br />faults and fractures between the coal seam and sources of ground or <br />surface water. <br />Fault and fracture controlled inflows have been noted and mapped in the <br />U.S. Steel Corporation Somerset Mine application (Exhibit E8-3366), the <br />Western Slope Carbon Hawk's Nest Mine permit application (Exhibit <br />2.04.7(1) or W-1006), the Blue Ribbon Coal Company Blue Ribbon Mine <br />application (Exhibit T), and the Colorado Westmoreland Inc. Orchard <br />Valley Mine Annual Hydrologic Report dated December 30, 1982. The Bear <br />Mine is not presently experiencing any mine inflows. The Mt. Gunnison <br />No. 1 Mine has encountered only minor inflows from fractures in the <br />Number 1 portal. A quantitative assessment of surface water depletion <br />through mine inflows is contained in the surface water section of the <br />Cumulative Hydrologic Impact Study. <br />Dewatering of Coal, Roof, and Floor <br />From field observations made by C`~II~RD hydrologists in the mines and <br />from information contained in their respective permit applications, <br />water was noted to seep from the coal, roof, and floor upon advance of <br />mining in the "B" and "C" seams of the Somerset Mine, the "D" seam of <br />the Orchard Valley Mine, the "E" seam of the Hawk's Nest Mine and Blue <br />Ribbon Mine, and "F" seam of the Mt. Gunnison Mine. These sources of <br />mine inflows dry up one to two weeks after mining an area. The minor <br />amount of water resulting from dewatering of the coal, roof, and floor <br />indicates that the coals and the overlying and underlying strata in the <br />Mesa Verde Formation have very low permeabilities. Thus, these strata <br />store and transmit very little water and are not considered aquifers. <br />Therefore, the impacts of dewatering the coals and the strata <br />immediately above and below the coals within the Mesa Verde Formation <br />will have an insignificant impact on the hydrologic balance. Also, the <br />very slow rates of inflow resulting from dewatering strata indicate <br />that the quantity of water transmitted by these strata will not result <br />in depletion of surface water sources. <br />