2009-02-27_REVISION - C1981019 - Laserfiche WebLink

Home Browse Search

significantly affect the spoil foundation conditions and should not reduce the global stability of the spoil fill." This general statement was based on their review of the Agapito reports for highwall mining and the design criteria for web and barrier pillars. The information that Shannon reviewed was also exclusively for the E-Seam highwall mining evaluated in the Agapito study. As with question 1 above, if Colowyo is planning on conducting highwall mining in any other seams, a revised determination regarding the stability of the fills must be performed. 6. The above referenced Shannon letter states that highwall mining under the South Taylor fills will not affect the "global" stability of the spoil fills. This statement leaves open the possibility that local stability issues may occur and the possibility that a local stability issue may lead to a more widespread stability problem. Because there is a possibility of either local or more wide spread stability problems with the spoil fills, please provide a mitigation plan for any stability problems or failures that may occur on the fills as a result of highwall mining. 7. The above referenced Shannon letter states that they have revised a Figure 5 in their original geotechnical study for the South Taylor Fills. This figure shows the areas of highwall mining proposed below the two fills in South Taylor. Please provide the Division with a copy of this revised Figure 5 for Exhibit 21, Item 1 - Geotechnical Report South Taylor Excess Fills. This completes the preliminary adequacy review for Colowyo Mine's Technical Revision 77. The decision date for this revision is 31 March 2008. Colowyo's prompt responses to these adequacy questions will help us meet this date. Please call me at (303)866-3567 X8145 if you have any questions. Sincerely, James R. Stark Environmental Protection Specialist cc: Sandy Brown