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COLORADO <br />Division of Reclamation, <br />Mining and Safety <br />Department of Natural Resources <br />1313 Sherman Street, Room 215 <br />Denver, CO 80203 <br />July 7, 2017 <br />Interoffice Memo <br />King Coal Mine (Permit No. C-1981-035) <br />2017 Waste Bank Compaction Results <br />M. <br />I have reviewed the compaction results for the King Coal Mine Coal Waste Bank and have the <br />following comments: <br />• As per King Coal Mine PAP, Appendix 10(1) — Waste Bank Design Summary Report, <br />GCC shall take a random compaction test during each of the first five years of <br />construction and at least every other year after that. The last compaction results for the <br />King Coal Waste Bank was 2016. GCC has met this requirement as per the King Coal <br />Mine PAP. <br />• As per Rule 4.10.4(3)(b), compaction must attain 90% of the maximum dry density <br />(proctor density). GCC took a total of six compaction tests, each resulting in 90% or <br />greater of the maximum dry density. <br />• Although all results meet the minimum requirements, I do have one comment regarding <br />the maximum dry density (or proctor density in the report provided by GCC) and <br />optimum moisture content used. In Appendix 10(1), material properties are summarized <br />with the maximum dry density as 91 pcf while the report uses 92.4 pcf. Additionally, the <br />optimum moisture content in the PAP is 12% but 12.5% is used in the report. Overall this <br />has little effect to the results (in fact it would increase relative compaction) but I am <br />curious on why there is a change. If the numbers used in the compaction report are <br />correct, then Appendix 10(1) may need updated to reflect these changes. <br />If you have any questions, feel free to contact me at any time. <br />Sincerely, <br />s' <br />awffl� <br />Zach Trujillo <br />Environmental Protection Specialist <br />(303) 866-3567 ext. 8164 <br />Zach.Trujillo@state.co.us <br />OF COLO <br />1313 Sherman Street, Room 215, Denver, CO 80203 P 303.866.3567 F 303.832.8106 http://mining. state. co. us I <br />John W. Hickenlooper, Governor I Robert W. Randall, Executive Director I Virginia Brannon, Director * r IR76 <br />