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2004 Geologic Hazard Field Observations <br />South of Divide Mining Area <br /> <br />4. A lazge landslide located neaz the southwest corner of projected longwall panel 8 in the <br />Nl/z of Section 8 and the S'/z of Section 5, Township 14 South, Range 90 West. <br />10.1.1 Landslide Movement Based on Past Observations <br />Historical records, which evaluate and document the effects observed in the field in landslide <br />areas-both related to mine subsidence and mine-induced seismic activity, is the best <br />information available to predict haw longwall mining will affect areas that will be mined in the <br />future. Considerable valuable information has been collected during the last nine years of annual <br />observations (I996 to 2004 inclusive). The most important observations regazding mine <br />subsidence and mine-induced seismicity aze itemized briefly below. <br />1. Longwall panels 8 and 9 were mined beneath landslides and landslide areas on Jumbo <br />Mountain during the mid 1990s. The landslides occurred during wet periods before <br />mining occuned, during mining, and after mining and subsidence was completed. The <br />landslides on Jumbo Mountain aze similar to those that occur north and south of <br />Minnesota Reservoir. Both occur in surficial material (rocks, gravel, sand, silt, clay, and <br />soil) and local bedrock that have slumped and flowed downhill, primarily during periods <br />of increased saturation. Cracks, bulges, local azeas containing depressions or troughs and <br />springs were observed in both landslide azeas. The following statements and conclusions <br />regarding longwall mining and overlying and adjacent landslides can be found in the <br />annual inspection reports sent to the Colorado Deparhnent of Mining and Geology <br />(CDMG) (data is in chronological order) fast by CDMG personnel in the field during <br />1996 and by the author during the period 1996 through 2004. <br />a Based on 17 yeazs of landslide experience, Dr. James Pendleton (CDMG) concluded <br />that subsidence (due to longwall mining below the 30 to 50 acre landslide area above <br />longwall pane18) "...did not appear to be a significant determinant in the reactivation <br />or initiation of landslide activity." Dr. Pendleton further stated "there is no evidence <br /> <br />831-032.621 Wright Water Engineers, Inc. Page 40 <br />November 2004 <br />