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COLORADO <br />Division of Reclarnatio , <br />,. <br />Mining and safety <br />Department of Natural Resources <br />1313 Sherman Street, Roorn 215 <br />Denver, CO 80203 <br />August 27, 2015 <br />Interoffice Memo <br />King Coal Mine (Permit No. C-1981-035) <br />Technical Revision No. 20 (TR -20) <br />Robin, <br />In our discussions, you had requested me to review two questions regarding to the geotechnical report <br />"Revised Geotehcnical Engineering Study For the National King Coal I West Waste Bank Coal Mine <br />Waste Disposal Area" (Report) conducted by Trautner Geotech, LLC. I have finished my requested <br />review of King Coal Mine's TR -20 and have the following comments: <br />The first requested adequacy question, Appendix 10(4) — 6.0 (b) [as labeled in the document], refers <br />to the compaction requirement for coal mine waste. As per Rule 4.10.4(3), coal mine waste is to be <br />compacted to a minimum of 90% proctor [or maximum dry density (MDD) as stated in the adequacy <br />letter]. The Division's comment was referring to the reports recommendation of 95% compaction and <br />with this recommendation, the Division would be increasing its permitted minimum compaction <br />requirement for coal mine waste to 95%. However, as stated by GCC, the 95% MDD recommendation <br />in the Report was in reference to the subgrade or foundation that the pile is to be constructed on and <br />not the actual mine waste. Thus, all previous minimum requirements of compaction for coal mine <br />waste will remain the same (90% proctor). This item no longer requires any additional comments and <br />is resolved. <br />The second requested adequacy question, Appendix 10(4) — 6.0(g), refers to compaction testing <br />frequency. As stated by the Division, GCC's required frequency of testing in the permit is currently <br />inadequate and needs to be updated. GCC currently has not yet provided these revised pages but has <br />agreed to include them with the next submission of revised permit text. Also, an additional question <br />was raised by the Division on whether Trautner Geotech, LLC had evaluated the foundation since the <br />"CMW Backfill" was removed. GCC responded with a yes and stated the Division was present at a <br />site meeting with GCC and Trautner on September 11, 2014 in regards to the foundation. Since no <br />1313 Sherman S'tree't, Roorn 215, Denver, CO 80203 P 303,8EiE 3567 F 303,832,8106 Ih't'tl:a:l/rnining.sta'te.co.0 s <br />John W. Hickenlool:aer, Governor I Mike King, Executive Director I Virginia Brannon, Director <br />