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plateaus and mesas, with gently dipping slopes dissected by deep canyons. Elevations at the site <br /> range from 5,790 feet (MSL) in the northeast corner of the permit area to 5,540 feet (MSL) at the <br /> southern end of the equipment corridor, for a total topographic relief of 250 feet. Permit Map <br /> 2.04.5-1 illustrates the topography and geology of the area surrounding the area to be mined. <br /> Structurally, the NHN site is located near the axis of the northwest-trending Nucla Syncline. <br /> This syncline is a shallow, broad, structurally simple fold bounded by gently dipping flanks. The <br /> syncline rests between the Uncompahgre Uplift to the northeast and the Paradox Valley <br /> Anticline to the southwest. Strata within the permit area strike at N 26' W, and dip at <br /> approximately 2° westward. The Lower Dakota(LDx) Seam is mined along with the upper seam <br /> when it is available and of sufficient quality. Overburden thicknesses range from approximately <br /> 10 feet near "Meehan Draw" to slightly over 90 feet at the former Nucla Mine highwall that was <br /> exposed when mining began. A general columnar geologic section is provided in the permit <br /> application with Figure 2.04.6-1. <br /> Ground Water- Sections 2.04.5 and 2.04.7 of the permit <br /> Topography, lithology, and structural trends each play a principal role in controlling the quality, <br /> quantity and flow characteristics of the regional ground water regime in the direct vicinity of the <br /> NHN area. The geology of this region is complex. Consequently, the ground water system is <br /> difficult to interpret. Understanding the effect the NHN may have on the local and regional <br /> ground water supplies relies on understanding the regional and local ground water systems. A <br /> general discussion of the regional groundwater conditions is provided in the permit document <br /> and summarized here. <br /> Topography is the principal element governing shallow aquifers (100 feet) in this region. <br /> Topographic highs act as recharge areas, and lows along streams serve as discharge areas during <br /> periods of high water table. In alluvial and other unconsolidated material, ground water moves <br /> from high topography to low. This also appears to be the case for the unconfined portions of <br /> sandstones in the Dakota and Burro Canyon formations. <br /> Lithology governs the aquifer characteristics including water yielding ability and the chemical <br /> quality of the ground water. The lithology of the NHN area is extremely variable. Shallow <br /> aquifers of the area consist of unconsolidated valley deposits of the Quaternary system and the <br /> stratigraphically variable sandstone, shales and coals of Cretaceous Age (Dakota, and Burro <br /> Canyon Formations). Deeper aquifers consist of the varicolored Morrison Formation and the <br /> Entrada Formation, both of Jurassic Age. <br /> Structural control on the shallow ground water in the area, i.e., upper Dakota Sandstone and <br /> alluvium, appears to be insignificant. Deeper formations, such as the lower Dakota, Burro <br /> Canyon, Morrison, and Entrada Formations, whose ground water is under artesian pressure, <br /> exhibit piezometric surfaces that conform to structural influence. Water table conditions <br /> commonly exist in shallow alluvial aquifers along the larger streams, in principal recharge areas, <br /> and in the relatively flat-lying rocks that dominate certain sections of the region. Artesian <br /> conditions occur locally throughout the region but are prevalent in the bedrock aquifers of the <br /> major structural basin. <br /> 10 <br />