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Burro Canyon Formation, is separated from the Dakota by an unconformity. The <br />Burro Canyon is comprised of white, gray and light brown sandstones and <br />conglomerates interbedded with green and purplish shales, siltstones, <br />mudstones and thin beds of limestone. This formation has a maximum thickness <br />of 200 feet and outcrops on rims of canyons northwest of the mine. This <br />formation is difficult to differentiate from the Dakota in this area, and is <br />commonly considered hydrogeologically similar. <br />Five coal seams have been identified in the horizon to be mined in the permit <br />area (Figure 2). They are identified, in descending order, as the Upper <br />Dakota-1, (UD-1), Lower Dakota-1, (LD-1), Lower Dakota-2, (LD-2), Lower <br />Dakota-3 (LD-3), and Lower Dakota-4, (LD-4). The LD-2 and LD-3 seams are of a <br />mineable thickness throughout the permit area. In the southern portion of the <br />permit area the LD-4 seam is of a mineable thickness. The thickness of the <br />LD-2 seam ranges from 1.6 to 3.5 feet thick with an average thickness <br />throughout the permit area of 2.5 feet with depths form the surface to the top <br />of the seam ranging from 7.2 to 28.1 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 <br />3.1 feet fn thickness with an average of 2.1 feet. <br />The splits between coal consist primarily of thin, lenticular, dark, <br />carbonaceous shales. The split between the LD-2 and LD-3 seam ranges in <br />thickness from 0.3 to 1.0 feet with an average of 0.6 feet thick throughout <br />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. Any <br />splits within the seams of thickness less than 0.3 feet will be taken with the <br />Coal during the mining operation. <br />There are two rider coal seams identified 1n the permit area, referred to as <br />the UD-1 and LD-1 seams. Neither rider seam is consistent in extent within <br />the permit area and therefore not considered mineable. Where identifiable, <br />the UD-1 and LD-1 rider seams are as much as 1.2 and 2.0 feet in thickness, <br />respectfully. Rider seam LD-1 overlies an average .08 feet thick dark shale <br />layer. The stratum which overlies the LD-1 rider seam and underlies the UD-1 <br />rider seam consists of an average 7.0 feet thick gray shale. The stratum <br />overlying the UD-1 rider seam consists of a soft, yellowish, fine-grained <br />sandstone that varies in thickness from 2.8 to 19.0 feet thick from the top <br />of UD-1 to the ground surface. <br />The stratum Immediately below the lowest mineable coal seam consists of a <br />soft, gray to blue shale with sparse shaley siltstone lenses. This strata is <br />generally 26 feet thick throughout the permit area. Below this strata there <br />are four coat seams that are not considered mineable within the permit area. <br />These coai seams are referred to as Naturita Seams 1 through 4, in descending <br />order. <br />Hydrologic Balance - Ground Water <br />Information on the occurrence and quality of ground water to the permit and <br />surrounding area is provided in Sections 2.04.7(1) and in Exhibit 3 of the <br />Hamilton Mine permit application. The hydrologic monitoring plan is presented <br />on page 2.05-35, and is approved as proposed. <br />-5- <br />