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RULE 2 PERMITS <br /> Exploration Test Borings <br /> Exploration test borings have been conducted within the South Taylor/Lower Wilson mining areas and <br /> have been used for the following purposes: <br /> Identifying Location of Subsurface Water - Since most of the exploration drill holes were dry, the <br /> circulation medium for most exploration drill holes drilled within the mine areas was compressed air with <br /> water and foam to lift the cuttings to the surface. Drilling mud was used when heavy fracturing or burn <br /> areas were encountered. Several drill holes throughout the area encountered minor amounts of <br /> groundwater; however, all of the data obtained to date by Colowyo and the USGS have indicated that <br /> groundwater occurrences in the Williams Fork Formation in the area are not continuous but rather are a <br /> series of perched systems of limited lateral and vertical extent. Information on groundwater occurrence is <br /> provided in Section 2.04.7. <br /> Characterizing Physical Properties of the Overburden-The overburden material,which is removed as <br /> a part of the mining operation, consists mainly of mudstones, siltstones, and sandstones. Generally, the <br /> mudstones will have a relatively high erodibility and compaction factor, while sandstones and siltstones <br /> will have low erodibility factors and low to moderate compaction. Because of the variable lithology and <br /> lenticular nature of the strata in the permit area and the variations in the mining techniques (dragline, <br /> truck/shovel), it is difficult to determine an actual value for the swell of the overburden; therefore, the <br /> overall swell of the overburden material was estimated to be approximately twenty(20)percent. <br /> Evaluating Geochemical Properties of Overburden-Chemical analyses of overburden and interburden <br /> strata in the areas to be mined are provided in Exhibit 6, Item 6. The ongoing overburden sampling <br /> program at Colowyo described in Exhibit 6, Item 4 of the existing permit document has confirmed earlier <br /> estimates of the geochemical properties of the overburden identified by exploratory drilling. A summary <br /> of overburden geochemistry is presented in Table 2.04.6-3 and the relevant borehole locations are shown <br /> on Map 7A. <br /> This section presents the results and interpretations of geochemical tests performed on overburden <br /> material samples from the South Taylor/Lower Wilson pit areas. The purpose of these tests is to <br /> determine the chemical composition and assess the acid-forming, toxic-forming, or alkalinity-producing <br /> potential of overburden material within the South Taylor/Lower Wilson pit areas. This section describes <br /> the methods used in collecting overburden samples for testing, the types of tests performed and the tests <br /> results. In addition, test result were compared with appropriate overburden guidelines to assess the <br /> acid-forming, toxic-forming, or alkalinity-producing potential of overburden material within the South <br /> Taylor/Lower Wilson pit areas <br /> South Taylor/Lower Wilson—Rule 2,Page 14 Revision Date: 5/10/18 <br /> Revision No.: MR-187 <br />