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III IIIIIIIIIIIII III <br />STATE OF COLORADO <br />MINED LAND RECLAMATION DIVISION pF'CG <br />Department of Natural Resources ti~>~'~> <br />„~~~ ~~o <br />1313 Sherman SL, Room 215 + n ~ ~n , <br />Denver, CO 80203 ,/ <br />303 866-3567 +•i8 6++ <br />Fa x'303 832-8106 <br />Roy Romer. <br />Governor <br />Fred R Bama, <br />Dnision Director <br />DATE: May 3, 1990 <br />T0: Jim Pendleton <br />FROM: Larry Routten <br />RE: Twin Pines Coal Waste Pile <br />Larry White has submitted Twin Pines' adequacy response for TR-3 (the proposed <br />coal waste pile). He has also submitted the final design for the North Spoil <br />Area, as required in the mine's permit. I am forwarding copies of both so <br />that you may review the geotechnical aspects. A few comments: <br />TR-03 <br />Mr. White was very brief in addressing some of your questions. I thought I <br />would add a few points which I have becane aware of after inspecting the site <br />and talking with Mr. White. If you think it important that we have more <br />written justification from him, let me know. <br />Item 1 (of your memo): He neglected this in his written response. The area <br />where the pile is proposed was strip-mined and there are no underground <br />workings beneath it. The sealed portal I previously mentioned to you is in <br />the highwall next to the area, not beneath it. Jim Herron indicated that <br />there was no evidence of any water in the portion of the workings that AML saw <br />when they worked in the area, so there are no drainage structures in the <br />workings. <br />Item 4: Stability concerns are addressed by Mr. White by referring to test <br />data from the waste material in the North Spoil Area pile. He never did <br />indicate to me (I don't think he has a very good idea) what proportion of <br />material going to the new pile would be the 2 parting development waste. <br />vs {he <br />North Spoil Area <br />A preliminary design for this structure is included in the mine's PAP <br />(pp. 84-5 and Appendix B), along with the statement: "Final design of the <br />spoil pile will be completed when representative samples of the actual spoil <br />can be tested...." I presume the preliminary design was approved by the <br />Division with the assumption that a 1.5 safety factor would be attainable at a <br />2:1 slope, which is what Lincoln - De Vore's tests indicate. Do you see any <br />problems with the test results or pile design? <br />LPR/yjb <br />6785E <br />