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• Phvsical Properties Overburden -The overburden material which is removed as a part of the <br />mining operation, consists mainly of shales, claystones, siltstones, and sandstones. Generally, <br />the shales and claystones will have a relatively high erodibility and compaction factor, while <br />sandstones and siltstones will have low erodibility factors and low to moderate compaction. <br />Because of the extremely lenticular nature of the strata in the permit area and the variations in <br />the mining techniques (dragline, truck/shovel), it was difficult to determine an actual value <br />for the swell of the overburden; therefore, the overall swell of the overburden material was <br />estimated to be approximately twenty (20) percent. Data collected during the previous five <br />years of operation has shown that the swell factor has continued to increase for the mine to <br />date as the total amount of overburden moved by dragline increases. Calculations for <br />verification of swell factors were previously presented to the Colorado Division of Mineral <br />and Geology, and the approval to suspend the development and presentation of validation <br />calculations within the annual reports was subsequently granted. <br />Chemical Analyses Overburden -Chemical analyses of overburden stratum in the area to be <br />mined are set forth in Exhibit 6, Geological Information. Examination of the data indicates <br />that sampling did not show any of the stratum to contain any potential acid-forming, toxic- <br />forming, or alkalinity-producing material. The ongoing overburden sampling program at <br />Colowyo has indicated those earlier results are correct. With the exception of Sodium <br />Absorption Ratio, there is little evidence of any chemical constituents reaching suspect levels <br />for toxicity. <br />• <br />2.04.6-9 Revision Date: 6/28/05 <br />Revision No.: MR-73 <br />