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<br />Section 779.14(a) Continued. Rule 2.04.6 <br />Thompson of CTL Thompson Inc., presented in Exhibit 23, Physical <br />Properties of Overburden. Generally, it was found that the shales and <br />claystones had relatively high erodibility and compaction factors while <br />sandstones and siltstones had very low erodibility factors and low to <br />moderate compaction factors. <br />The samples utilized to determine physical properties of the overburden <br />materials to be disturbed by future mining were obtained from existing <br />mine spoils. These spoils are composed of the same lithic materials as <br />will be disturbed as mining progresses northward. This method is <br />preferable to taking core samples from the area to be mined for the <br />following reasons: 1) a greater quantity of material can be sampled; and <br />2) samples can be collected to accurately reflect the various stages of <br />weathering. Because the overburden lithology is similar in the Marr mine <br />• area and the Kerr north area, as shown by the Geologic Cross-Sections A- <br />G (Maps 7a through 13a), the data compiled by sampling the overburden from <br />the Marr mine area can be applied to the Kerr north area (the area to be <br />mined). <br />The texture of each lithologic type within the overburden to be disturbed <br />by mining has been analyzed using samples collected from the intervals <br />shown on the revised Geologic Cross-Section G (Map 13a). The samples were <br />collected and analyzed in accordance with the 1977 Wyoming DEQ Guideline <br />No. 1. The sample intervals are as follows: Hole No. 028-79-40C: 0-20', <br />20-40' and 40-53'; Hole No. 028-80-21C: 15-80'; Hole No. 028-80-23C: 5- <br />100', 100-200', 200-318', 318-350'; and Hole No. 028-80-24C: 10-75' and <br />75-160'. Additionally, one (1) sample of spoil material was analyzed for <br />texture. <br />In accordance with the guideline each sample used for textural <br />determination is to be ground to 20 mesh prior to sizing. Due to the need <br />• to obtain a realistic textural analysis of the spoil material, a textural <br />determination was made using the composite spoil sample without the <br />specified physical reduction in particle size. The results of textural <br />analysis for the I1 samples presented in Table 76, Textural Analysis of <br />Overburden, are reported as percent sand, percent silt, and percent clay. <br />779-15 b Revised-Aori1.1990 <br />