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Colowyo, C1981-019, PR3 adequacy 15 February 25, 2011 <br />to seeding." The Division is unsure what CCC is trying to say with this statement. Please <br />review this section of the application and revise accordingly. (Rule 4.06.3(2)(b)) <br />2. In the discussion of Topsoil redistribution, Rule 4, page 20-21, CCC commits to variable <br />topsoil depth replacement but does not explain how this will be implemented. A discussion of <br />the variable topsoil depth replacement is found in Section 2.05.4(2)(d). Topsoil handling map <br />28C does not show which topsoil thickness will be placed on the regraded contours. Please <br />provide the Division additional information regarding variable topsoil depth replacement on the <br />regraded landscape. A map with the post-mining contours showing the range of topsoil <br />replacement depths within a defined area would be appropriate. This replacement depth range <br />could be associated with slope gradient, post-mining land use, aspect, or other factors. <br />Proposed replacement depth needs to be described prior to placement and not only reported <br />after it has been placed as proposed in application Section 2.05.4(2)(d). <br />Rule 4.09 Disposal of Excess Spoil <br />A large (250,000,000 cy) temporary (-20-year) excess spoil pile is proposed. A Geotechnical <br />Study for the Collom Temporary Spoil Fill, conducted by Shannon & Wilson (S&W), is provided <br />in Exhibit 23, Item 1. The fill qualified as a "Valley Fill". Map 29C shows plan and cross- <br />sectional views of the proposed pile. General information regarding the pile is provided in Rule 2, <br />pp. 98-99; Rule 4, pp. 22-23 describes the proposed construction and inspection plans. <br />1. The S&W Study is thorough in its analysis of site conditions, material properties, and analysis <br />of stability. The study is dated July 2009, and was developed using the obsolete plan for <br />mining of Little Collom X Pit. Please update the S&W Study to address any revised ground or <br />spoil pile configurations that may arise as a result of the anticipated changes in mine plan for <br />Little Collom X Pit. <br />2. Exhibit 7 Item 26, Fig. 2 illustrates a proposed "Collom Sump". It appears that this sump pond <br />may be located near the toe of the proposed excess spoil pile. Please ensure that S&W are <br />informed of the presence of the sump, and its position in the mining sequence, so that any <br />potential effects it may have on the pile itself or the foundation materials may be considered in <br />the stability evaluation. <br />3. The 2nd paragraph on S&W Page 11 states that, "Prior to publication of our report, Colowyo <br />informed us the spoil slope will be decreased from the 3H: IV slope used in our models to a <br />slope of 3.5H:1 V ..." On Map 29C, Section A-A' does show a slope of 3.4H:1 V on the <br />southern slope of the pile, but the northern (and most critical, for stability) slope continues to be <br />labeled as 3H:1 V. <br />a. Please provide clarification of the actual slope proposed for construction of the northern <br />face of the temporary excess spoil pile. <br />b. The paragraph quoted in part, above, ends with an incomplete sentence. Please review and <br />revise, as appropriate.