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<br /> <br /> <br /> 9 <br />development. An additional 9% is dominated by wetlands. The State Historic Preservation Officer <br />(SHPO) determined that a finding of “no historic properties affected” was appropriate for the <br />proposed activities. <br /> <br />Geology and Topography – Sections 2.04.5 and 2.04.6 of the permit <br /> <br />The NHN is located three miles northwest of the town of Nucla, in Western Montrose County, <br />Colorado. The mine area lies within the southeastern section of the Colorado Plateau <br />Physiographic Province. The region is characterized by broad, fairly smooth surfaced sandstone <br />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 /> <br />Structurally, the NHN site is located near the axis of the northwest-trending Nucla Syncline. This <br />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 Anticline <br />to the southwest. Strata within the permit area strike at N 26° W, and dip at approximately 2° <br />westward. The Lower Dakota (LDx) Seam is mined along with the upper seam when it is available <br />and of sufficient quality. Overburden thicknesses range from approximately 10 feet near "Meehan <br />Draw" to slightly over 90 feet at the former Nucla Mine highwall that was exposed when mining <br />began. A general columnar geologic section is provided in the permit application with Figure <br />2.04.6-1. <br /> <br />Ground Water - Sections 2.04.5 and 2.04.7 of the permit <br /> <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 ground <br />water supplies relies on understanding the regional and local ground water systems. A general <br />discussion of the regional groundwater conditions is provided in the permit document and <br />summarized here. <br /> <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 /> <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.