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r <br /> <br />• <br />ICI <br />mine and plant were shut down and as we understand, significant <br />amounts of additional waste have not been placed since that time. <br />During the period between the 1995 investigation and the 1996 shut- <br />down, we performed periodic compaction testing and ground water <br />measurements on the working surface of the RDA, and ground water <br />measurements in the wells installed on the lower end benches. This <br />work was performed under CTUThompson, Inc. Job No. 22,905; copies <br />of the results of the testing and ground water measurements are <br />attached as Appendix A. The compaction testing and ground measure- <br />ments were performed in March, June, September, November of 1995, <br />and March of 1996. The density testing indicated satisfactory <br />compaction was achieved. The ground water measurements indicated <br />water was not building up within the pile and ground water levels were <br />generally at or below the base of the pile. <br />3. We discussed RDA conditions with Mr. Ron Thompson of Basin <br />Resources. We understand he has performed the quarterly inspection <br />for coal waste banks in accordance with rules 4.09(11) and 4.10(2)(2). <br />Mr. Thompson estimated approximately 15 to 20 feet of fill has been <br />placed since our 1995 supplemental stability investigation. This fill <br />was density tested as discussed above. Mr. Thompson indicated no <br />unfavorable conditions were identified in his quarterly inspections. <br />To summarize, the Supplemental Stability Evaluation performed in 1995 <br />judged the existing RDA configuration to be stable. At that point the RDA top <br />elevation was about 7640. The waste placed subsequent to this investigation was <br />estimated to be approximately 15 to 20 feet. This material was compaction tested, <br />ground water measurements performed, and quarterly inspections performed <br />according to CDMG regulations. Based upon the above information, we judge the <br />current RDA configuration to be stable. <br />We hope this provides the information you require. If you have questions, <br />please call. <br />Very truly yours, <br />~; °~. <br />'~<~r\ <br />,;; , <br />• <br />Project M <br />MGG:sf "' <br />(6 copies sent) <br />LORENCITO COAL MINE <br />NEW ELK RDA <br />CTLlT 26,600 <br />~~~: <br />~9 ~~~'~ <br />,. <br />2 <br />