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Subsidence and Geologic Field Observations <br />Apache Rocks and Box Canyon Mining Areas <br />July 12-15, 2004 <br />4.4.5 Analysis of the Effects of Longwall Mining on Landslides <br />No effects of Longwall mining on landslides in the Apache Rocks and Box Canyon mining areas <br />have been observed around the cliffs and over-steepened slopes around West Flatiron. For <br />example, no effects were observed on the debris flows near the southwest part of West Flatiron <br />as Longwall panels 14 and 15 were mined, and no effects were observed on the landslide on the <br />west side of Deep Creek when Longwall panel 17 was mined. In addition, little or no effects were <br />observed on the landslides on Jumbo Mountain when Longwall panels 8 and 9 were mined during <br />a period of above average precipitation. In summary, little or no effects on landslides were <br />observed as a result of the dynamic tilt and strain produced by mine subsidence. In addition, any <br />seismic effects that may have been caused by stress-strain adjustments during mining had no <br />noticeable effect on the landslides. <br />Based on this historic information, no effects on the landslides located south of the North Fork <br />' of the Gunnison River (the Highway 133 landslides), are expected if Longwall mining panels 18, <br />18A, and 19 are mined in times of normal precipitation. Should these Longwall panels be mined <br />during a very wet period, renewed landslide activity could occur. However, based on the <br />observation that very little, if any, effects were observed on landslides on Jumbo Mountain <br />' during the mining of Longwall panels 8 and 9, any renewed landslide activity would be primarily <br />due to natural mass-gravity movements. <br />831-032.640 Wright Water Engineers, Inc. Page 45 <br />September 2004 <br />