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Fall 2008 Subsidence and Geologic Field Observations <br />Box Canyon, Apache Rocks, and South of Divide Mining Areas <br />The estimated thickness range of the soil, alluvium, and local colluvium in the Deer Creek Valley <br />is 50 to 150 feet. This material is expected to yield without cracking during the mining of <br />Longwall Panels E3 through E6. <br />Surface flow in Deer Creek was observed to be about 1-3 gpm near N', about 5 gpm near the <br />middle of the traverse, and non-existent at the mouth of the drainage even though there is no <br />current mining in the area. The reduction of surface flow over the 3,500-foot distance is likely <br />the result of increased flow to the alluvium and bedrock units underlying the valley floor. <br />There were no obvious slope instability areas observed along this traverse. <br />• <br />• <br />831-032.790 Wright Water Engineers, Inc. Page 64 <br />December 2008