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SubTerra, Inc. Twentymile Coal Company 05128/03 <br />PR6 AVF Subsidence Evaluation <br />• 4. Monitoring Requirements <br />Visual inspection and conventional or GPS surveys of the expanded Foidel and Fish Creek areas <br />may be used to confirm the predicted effects of mining. This methodology has previously been <br />successfully used where Panels 9, 8, and 7-Right in the Eastern Mining District have undermined <br />Foidel Creek. <br />5. Conclusions and Recommendations <br />The evaluation presented in Section 3 predicts that Fish creek will overflow its highbank(s), <br />primarily above 17-Right in the northern mining district at the Twentymile mine. Subsidence is <br />predicted to have the following impacts on Fish Creek and its AVF: <br />1. A maximum increase in creek bottom gradient of 0.006 (0.6%). <br />2. Increase in the surface area of Fish Creek from 2.4 acres to 6.8 and 7.3 acres <br />following excavation of Panels 17 and 18-Right in the Northern Mining district. <br />3. Temporary increase in Fish Creek's surface area to 12.3 acres during peak flow <br />conditions. <br />If you have any questions regarding the above, please do not hesitate to call us at 425-888- <br />5425. <br />• Best Regards <br />Chris Breeds, PE, PhD <br />President <br />i <br />PN: 2002-06 <br />