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. Physical 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, track/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 have been presented in the Colowyo Annual Report each year <br />since 1983. <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. Analyses of Overburden Chemistry is also present in Annual Reports since <br />1983. <br />J <br /> <br />2.04.6-9 <br />