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Bowie No. 2 Mine <br />TR-61 Adequacy Review <br />29 May 2009 <br />Page 3 of 4 <br />Please detail the proposed methods of placement of coal mine waste, in accordance <br />with BGI's recommendations. <br />NC: Placement and Compaction of coal mine waste is described on the proposed <br />Page 9 of Volume IX. A comparison with the recommendations for placement of <br />coal waste found in Section 6.0 of the BGI TR-56 report reveals that not all of the <br />recommendations have been incorporated. Specifically, the details for benching new <br />coal mine waste into material previously placed should be described. <br />Please modify the Placement and Compaction section to incorporate all of the <br />recommendations included in the BGI TR-56 report. <br />NC: The third paragraph on Page 9 of Volume IX states that Compaction tests will <br />be taken at a frequency and location of not less than one per every other layer. A <br />review of the dimensions of CMWDA2 indicates that a single two-foot layer may <br />have a surface area of 600 feet by 1200 feet (a volume of approximately 50,000 cubic <br />yards). The proposed compaction test frequency is therefore apparently just one test <br />per 100,000 cubic yards. According to Volume IX Page 1, the mine's current <br />production of coal mine waste averages 330,000 cubic yards per year. Three to four <br />compaction tests per year for a pile this size is not sufficient to guarantee that <br />compaction is consistently achieved. <br />Please clarify and/or modify the proposed compaction test frequency, to ensure a <br />sufficient level of confidence in the uniform compaction of coal mine waste. <br />Analysis of Monitoring <br />OC: BGI's stability evaluation report recommends that monitoring of CMWDA2 <br />with piezometers and inclinometers be continued. Utilization of the monitoring data <br />collected was not discussed in the report. <br />In the upcoming Technical Revision, please describe, as a minimum: <br />• How the monitoring data collected will be used <br />• Measurements (of pore pressure or inclination) that might indicate any <br />potential instability in the CMWDA2 configuration <br />• Proposed mitigation of any potential or actual stability issues <br />• How often and by what means data will be reported to the Division <br />NC: The Stability Analysis portion of the proposed Volume IX text (pages 13 and <br />14) describes, in general terms, the collection, evaluation, and reporting of monitoring <br />data that will occur on a quarterly basis. <br />No further action is required.