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observed in drill holes at the Hamilton Mine area. The Nucla Syncline is 10-15 miles southwest of <br />the major regional geologic feature of the azea, the Uncompahgre Uplift. The region lies in the <br />Dolores River Basin. The mine is located one and one half miles south of the San Miguel River. <br />The mine is located in the Nucla-Naturita Coal Field. The coal is found in Late Cretaceous <br />sediments. The youngest Cretaceous rocks in the azea consist of Mancos Shale, a dazk gray marine <br />shale, present only on isolated hilltops south of the town of Nucla. Two hundred feet of Dakota <br />sandstone outcrops extensively along the axis of the Nucla Syncline. This formation consists of a <br />yellowish-gray, fissile sandstone and conglomeratic sandstone interbedded with dazk gray shale and <br />coal. There aze nine coal seams within 100 feet of the base of the Dakota. The Lower Cretaceous <br />unit in the area, the Burro Canyon Fonnation, is separated from the Dakota by an unconfomity. <br />The Burro Canyon is comprised of white, gray and light brown sandstones and conglomerates <br />interbedded with green and purplish shales, siltstones, mdstones and thin beds of limestone. This <br />formation has a maximum thickness of 200 feet and outcrops on rims of canyons northwest of the <br />mine. Ttis formation is difficult to differentiate from the Dakota in this azea, and is commonly <br />considered hydrogeologically similar. <br />Five coal seams have been identified in the horizon that was mined in the permit azea. They aze <br />identified, in descending order, as the Upper Dakota-1, (UD-1), Lower Dakota-1, (LD-1), Lower <br />Dakota-2, (LD-2), Lower Dakota-3 (hD-3), and Lower Dakota-4, (LD-4). The LD-2 and LD-3 <br />seams are of a minable thickness throughout the pemit area. In the southern portion of the permit <br />azea, the LD-4 seam is of a minable thickness. The thickness of the LD-2 seam ranges from 1.6 to <br />3.5 feet thick, with an average thickness throughout the permit area of 2.5 feet and with depths from <br />the surface to the top of the seam ranging from 7.2 to 28.7 feet. The LD-3 seam averages 1.6 feet <br />thick and ranges from 0.8 to 2.9 feet thick. The LD-4 seam ranges from 1.2 to 3.1 feet in thickness <br />with an average of 2.1 feet. <br />The splits between coal consist primarily of thin, lenticular, dazk, cazbonaceous shales. The split <br />between the LD-2 and LD-3 seam ranges in thickness from 0.3 to 1.0 feet with an average of 0.6 <br />feet thick throughout the permit area. The split between the LD-3 and LD-4 seam averages a <br />thickness of 1.1 feet and ranges from 0.7 to 1.7 feet in thickness. <br />There aze two rider coal seams identified in the permit azea, referred to as the UD-1 and LD-1 <br />seams. Neither rider seam is consistent in extent within the permit azea and therefore were not <br />considered for mining. Where identifiable, the UD-1 and LD-1 rider seams are as much as 1.2 and <br />2.0 feet in thickness, respectfiilly. Rider seam LD-1 overlies an average .OS feet thick dazk shale <br />layer. The stratum which overlies the LD-1 rider seam and underlies the UD-1 rider seam consists <br />of an average 7.0 feet thick gray shale. The stratum overlying the UD-1 rider seam consists of a <br />soft, yellowish, fine-grained sandstone that varies in thickness from 2.8 to 19.0 feet thick from the <br />top of UD-1 to the ground surface. <br />The stratum immediately below the lowest minable coal seam consists of a soft, gray to blue shale <br />with sparse shaley siltstone lenses. This strata is generally 26 feet thick throughout the permit area. <br />Below this strata aze four coal seams that aze not considered minable within the permit azea. These <br />coal seams are referred to as Naturita Seams 1 through 4, in descending order. <br />3 <br />