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Probable Hydrologic Consequences New Elk Mine 3 <br />3. HYDROGEOLOGIC SETTING <br />The geologic, and hydrologic setting of the mine area has been described in numerous reports by the United <br />States Geological Survey (Wood et al., 1951 and 1956; Johnson, 1961 and 1969; Flores and Bader, 1999; <br />and Watts, 2006a and 2006b) and in consultant reports that have been prepared to support permitting <br />analyses for the New Elk and Golden Eagle mines (Waste Water and Land [WWL], 1980 and Greystone, <br />1994). A summary of the geology and groundwater hydrology for the site is presented in the following <br />sections. <br />3.1 Geology <br />Coal that will be produced by the New Elk Mine is contained within the Upper Cretaceous to Tertiary <br />Raton Formation. The Raton Formation is a heterogeneous sequence of lenticular, argillaceous sandstone, <br />siltstone, mudstone, and coal. Lithology types are highly variable, both laterally and vertically, with <br />correlations being best established through the occurrence of coal beds. Surface and near - surface bedrock <br />in the mine area is limited to the Tertiary Poison Canyon Formation and the Raton Formation as shown on <br />Figure 2. <br />The mine is located on the west flank of the Raton Basin, an asymmetric, north -south trending structural <br />trough. Rocks in the permit area dip gently to the east - northeast with and average inclination of 2 to 4 <br />degrees. East trending normal faults with relatively small displacement (3 to 30 feet) were encountered <br />during previous mining and were successfully traversed without significant inflow to the underground <br />workings. Likewise, a thin basaltic dike was exposed in the Allen Mine, but it was crossed with minimal <br />impact to the mining operation. Fractures and cleats in the coal seams vary in orientation, but the dominant <br />trend appears to be east -west to northeast- southwest. <br />The Raton basin was intruded by magma during the Miocene and Pliocene. Intrusive activity related to <br />emplacement of the Spanish Peaks Igneous Complex was accompanied by extensive fracturing and <br />development of dikes, sills, plugs, and stocks. Igneous dikes are mapped north of the permit boundary and <br />trend east -west to northeast- southwest. They are mostly intermediate to ultramafic in composition. Dikes <br />can range from a few inches in thickness to more than 100 feet and are presumed to have intruded along <br />fractures. Sills occur northeast of the permit boundary where they intrude coal seams. <br />Four coals seams are of mining interest in the permit area. In stratigraphic order from bottom to top, they <br />include the Allen, Apache, Maxwell, and Blue coal seams. Previous mining in the project area produced <br />coal from the Allen and Maxwell seams. The current mining plan focuses on production from the Allen <br />and Apache coal seams. The Allen coal seam varies in thickness from 2 to 8 feet, and has an average <br />thickness of 5.5 feet in the mine area. It was the primary production horizon from the Allen and New Elk <br />mines, and extensive underground workings document its continuity. The Apache coal seam occurs 20 to <br />50 feet above the Allen seam and varies in thickness from 1 to 6 feet. The average thickness of the Apache <br />coal is 4.5 feet within the permit area. Extensive production of the Apache coal seam has not previously <br />occurred. The Maxwell seam is located about 25 to 50 feet above the Apache seam and has a thickness of <br />1 to 5 feet. The Maxwell seam was the main production horizon from the Golden Eagle Mine. The seam <br />thins westward from the Golden Eagle Mine toward the New Elk Mine where its average thickness is 2.5 <br />feet. The Blue seam occurs in the northern part of the permit area approximately 175 to 200 feet above the <br />Maxwell Seam and is contained in the Upper Coal Zone of the Raton Formation. The thickness of the Blue <br />coal varies from 1.5 to 7.4 feet where exposed in exploration boreholes. A number of other named coal <br />seams occur in the Raton Formation, but are not of economic interest. These seams include the Yellow, <br />Red, Green, and Upper and Lower Bingham Canyon coal seams. Coal beds within the Raton Formation <br />are targets for numerous coal bed methane (CBM) wells that are active within the permit and surrounding <br />areas. Cross sections showing the stratigraphic relationship of coal seams within the Raton Formation are <br />presented on Plate 2. <br />4164A.110421 Whetstone Associates <br />TD « QtAl D­ ion nMAI i <br />