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2004 Geologic Hazard Field Observations <br />South of Divide Mining Area <br />2, No cracks are expected to occur in the alluvium in Dry Fork or the drainages of Dry Fork <br />of Minnesota Creek or Lick Creek. Based on observations in the Apache Rocks mining <br />area during the last 6 yeazs (1999 to 2004 inclusive), it is unlikely that the alluvium in <br />Dry Fork and its tributaries will be affected by longwall mining. No cracks were <br />observed in the alluvium above the four mined longwall panels in the Deep Creek area, <br />where the overburden depth to the B Seam ranges from about 950 to I,O50 feet. No <br />cracks were observed in alluvium above four mined longwall panels in the upper part of <br />Sylvester Gulch, where the overburden depth ranges from about 900 to 1,600 feet. <br />Finally, no cracks were observed in the Bear Creek alluvium above groom-and-pillar <br />extraction azea, where the overburden depth ranges from 220 to 300 feet. <br />The alluvium in the South of Divide mining area contains more Wasatch clays than in <br />Deep Creek and Sylvester Gulch. Therefore, mining effects on the alluvium are even less <br />likely to occur. <br />3. Mining projected longwall panel E9 is not expected to affect the large landslide located <br />south of Minnesota Reservoir. Based on annual observations over anine-yeaz period, the <br />primary conclusion regarding the effects of longwall mining beneath Landslides on Jumbo <br />Mountain and the Apache Rocks and Box Canyon areas, is that the landslide movement <br />occurs in response to increased ground saturation and is not significantly affected by <br />subsidence or any seismic activity generated by longwall mining beneath, or near, <br />landslides. <br />4. Mining impacts on rockfalls were not observed during annual subsidence observations in <br />the Apache Rocks and Box Canyon mining areas over the last six years (1999 to 2004 <br />inclusive), in areas where the estimated rockfall potential was moderate to high. The <br />highest estimated rockfall potential is classified as moderate to high in the South of <br />Divide mining area, and many of these are located in areas where no mining is currently <br />planned. Consequently, the natural rockfall process is not expected to be significantly <br />accelerated by longwall mining. Evidence of naturally occurring rockfalls, such as <br />831-032.621 Wright Water Engineers, Inc, Page 48 <br />November 2004 <br />