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Rob Zuber <br />Page 2 <br />October 14, 2015 <br />difficult to extract relevant information from the figures (particularly the thickness of the K,,, <br />layer). <br />Please redraw the cross-sections with vertical exaggeration. A scale of 1" = 50'-100' on the <br />vertical axis would be appropriate. <br />4. The legend on Figure 2.04.6, Sheets 1 and 2, shows layers marked "Pit Shell", "TC -P' and "STCM" <br />in addition to the 70+ identified coal seams. These layers appear not to have been drawn. <br />Furthermore, it is not clear what "TCr' and "STCM" refer to. Per the text, the lowest coal seam <br />to be mined is GB which is shown in blue on the cross-sections. The Smectite layer (K,,,), which <br />has been identified as a laterally continuous low -permeability layer, is shown in pink. <br />Please clarify the terms used in the legend. Please also display the first aquifer below the <br />lowest coal seam to be mined (presumably the Trout Creek Sandstone) on the cross-section. <br />5. In Volume 15, Rule 2, Page 13 the text reads "The Trout Creek sandstone underlies the lowest <br />surface recoverable seam to be mined at South Taylor (the 6789 seams) by approximately 590 <br />feet" <br />Please revise this section of text to refer to the separation between the Trout Creek sandstone <br />and the lowest seam to be mined in the vicinity of the proposed Collom pit and use this value <br />consistently throughout the text of volume 15. Please also cite the data that allows CCC to <br />accurately assess the separation over this area. [Refer also item 17 in this letter] <br />6. In Volume 15, Rule 2, Page 16 a paragraph appears to have been inserted that is not relevant to <br />the Collom area: "Overburden and interburden samples from drill holes 97-06, 97-09..." <br />For clarity, please remove irrelevant text. <br />7. Of the six drill holes that were sampled for overburden/interburden analysis, only one falls <br />within the —1.4 square mile footprint of the newly proposed Collom pit (C-04-25). The guidelines <br />call for a minimum of 3 sampling locations with a spacing of approximately one hole per square <br />mile [1]. In the geochemical analysis, CCC has also cited a guideline published by the Wyoming <br />Department of Environmental Quality [2], which calls for an initial sample spacing of one hole <br />per 80 acres (which is equivalent to 8 holes per square mile). <br />The geochemical data from the six holes is presented in Exhibit 6, Item 9, and summarized in <br />table 2.04.6-7 and in the text. The data shows that hole C-04-25 contains a greater proportion of <br />unsuitable overburden material than the other five holes. For example: <br />a significant proportion of the overburden sampled at this point (27%) contains <br />Molybdenum at greater than 1ppm <br />the deeper horizons are notably high in Arsenic, with a maximum value of 39.8ppm <br />(compared to the WY DEQ criteria of <2.Oppm) <br />the deeper horizons also have elevated levels of Sodium, as indicated by the high SAR <br />values <br />