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Physical Properties Overburden - The overburden material which is <br />removed as a part of the mining operation, consists mainly of <br />shales, claystones, siltstones, and sandstones. Generally, the <br />shales and claystones will have a relatively high erodibility and <br />compaction factor, while sandstones and siltstones will have low <br />erodibility factors and low to moderate compaction. Because of the <br />extremely lenticular nature of the strata in the permit area and <br />the variations in the mining techniques (dragline, truck/shovel), <br />it was difficult to determine an actual value for the swell of the <br />overburden; therefore, the overall swell of the overburden material <br />was estimated to be approximately twenty (20) percent. Data <br />collected during the previous five years of operation has shown <br />that the swell factor has continued to increase for the mine- <br />to-date as the total amount of overburden moved by dragline <br />increases. Calculations for verification of swell factors have <br />been presented in the Colowyo Annual Report each year since 1983. <br />Chemical Analyses Overburden - Chemical analyses of overburden <br />stratum in the area to be mined are set forth in Exhibit 6, <br />Geological Information. Examination of the data indicates that <br />sampling did not show any of the stratum to contain any potential <br />• acid-forming, toxic-forming, or alkalinity-producing material. The <br />ongoing overburden sampling program at Colowyo has indicated those <br />earlier results are correct. with the exception of Sodium <br />Absorption Ratio, there is little evidence of any chemical <br />constituents reaching suspect levels for toxicity. Analyses of <br />Overburden Chemistry is also present in Annual Reports since 1983. <br /> <br />2.04.6-9 <br />