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Tom Bird, GCC Energy <br />C -1981 -035 / TR -20 PAR <br />29- Nov -2013 <br />Page 10 of 12 <br />g) In 6.5, Trautner recommends the CMW be placed with a moisture content within 3% <br />of optimum and compacted to a minimum of 90% MDD (standard Proctor). An initial <br />lift thickness of 12" is recommended, possibly adjusted to 24" as field monitoring and <br />testing is done. These recommendations are acceptable; Rule 4.10.4(3)(a) requires <br />that CMW be spread in layers no more than 24" in thickness, and (b) requires <br />compaction of 90% MDD to prevent spontaneous combustion and provide the strength <br />required for stability of the waste bank. <br />6.5.1 says that Trautner should be contacted to observe the materials exposed, to <br />identify any potential sources of moisture that would require the installation of a <br />subdrainage system. Has Trautner evaluated the foundation since the CMW Backfill <br />was removed? The second paragraph of this subsection addresses Trautner's <br />monitoring of CMW placement, once construction of the waste bank has commenced. <br />The approach described is generally acceptable. Rules 4.09.1(11) and 4.10.2 address <br />the inspection requirements for spoil and CMW. Please note that 4.09.1(11)(4) <br />requires that an engineer (or representative) be on -hand during placement and <br />compaction of fill materials. On this point (frequency of testing), the current permit is <br />inadequate. Please update the permit to address the frequency of compaction testing <br />that wi1I be conducted for both the West Waste Bank and the Refuse Pile. <br />h) Section 2.05.4 of the permit refers to the Trautner report for determination of cover <br />material. Subsection 6.7 of Trautner addresses placement of cover material, and refers <br />the reader to the Appendix C (by CDS Environmental) of the report, Page 5 of the <br />CDS report (Appendix C) recommends the following: apply 6 -8 inches of a high clay <br />soil to the final surface of the waste bank, and roto -till 15 -18 inches deep. Then, apply <br />a 24 inch top soil cap suitable for plant growth. For the Refuse Pile, the permit <br />requires 3.5 feet of "cover ", topped with 6 inches of "plant growth medium ". <br />i) Does GCC wish to utilize a different reclamation and cover strategy (i.e. the CDS <br />plan) for the West Waste Bank than that which is currently permitted for the <br />Refuse Pile, per Rule 4.10.4(5)? <br />ii) The permit text should be revised to include the cover requirements for the West <br />Waste Bank just as it does for the Refuse Pile. <br />5. 7.0 Slope Stability Analysis <br />a) With the August 14, 2012 report, Trautner evaluated waste bank heights of 10 and 20 <br />feet, and outslopes of 2h:ly, 2.5h :1v, and 3h:ly. All of the analyses produced a factor <br />of safety (FOS) which exceeded the minimum static FOS of 1.5 required by Rule <br />4.10.4(2). The report did recommend that slopes of 2h:1v should be avoided, due to <br />construction limitations. <br />b) With the February 2013 submittal, a new stability analysis from Trautner was <br />provided which utilized the specific dimensions now proposed for the West Waste <br />Bank. This analysis considered a pile height of 30 feet with a face constructed at <br />2.5h:Iv. The result is a predicted FOS of 1. 69, which exceeds the required minimum <br />of 1.5. <br />