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Page 3of10 <br />The date of the September 2012 report is listed as September 5, 2012. The report is <br />actually dated September 7, 2012. Please correct the TOC with the correct date for the <br />September 7, 2012 report. <br />It would also be helpful if the list of stability analyses were further identified by the <br />permitting action that prompted the report. Please consider adding the applicable <br />revision number to each listed report. <br />6. This item has been addressed. <br />7. This item has been addressed. <br />8. This item has been addressed. <br />9. This item has been addressed. <br />10. This item has been addressed. <br />11. This item has been addressed. <br />After reviewing the proposed revision materials for TR85 and 84, the Division has identified areas <br />of potential concern with Gob Pile #2, which are listed below. The attached summary provides <br />background information on the materials reviewed to identify these concerns. <br />12. Recent stability analyses (since 2012) have assumed no phreatic surface exists in the <br />compacted waste. Based on the fact that pore pressures, as observed in two Vibrating <br />Wire Piezometers installed in Gob Pile #2, are not dissipating, this assumption may not <br />be valid. At a minimum, the presence of a phreatic surface needs to be incorporated <br />into all future analyses. <br />13. Also related to pore pressures: is there a potential for Undrained conditions to <br />prevail? This option was considered in studies performed in 2006 and 2007, but <br />deemed inappropriate in later studies. <br />14. Currently there are two functioning VWPs in the upper region of Gob Pile #2 and three <br />at the toe. Is the current number of VWPs sufficient, given the slow rate of dissipation <br />observed in the active areas of the waste pile? Are the VWPs installed there sufficient <br />to provide reliable information about the behavior of coal mine waste disposed of in <br />Gob Pile #3? or should additional VWPs be installed at #3? <br />15. Are the consistently high pore pressures measured at VWP -06 and VWP -08 a cause for <br />concern? If not, what level of pressure would indicate that the stability of the pile may <br />be in jeopardy? <br />