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Environmental Assessment Bowie Resources, L.L.C. <br />August 2005 Spruce Stomp Federal Coal Explomdon License (150- 2005 -43) <br />during periods of high to very high precipitation in the mid 1980s. The geologic hazards are <br />shown in Figure 3 -8, Geology Hazards, and listed below. Some of the geologic hazard map <br />units, as defined by the State, have been combined. <br />Landslide (Is): This geologic hazard type primarily describes landslides that have moved in the <br />last few centuries, decades, or years. It may include local, quasi - stable areas and some <br />colluvium. "Landslide" also includes earthflows, debris avalanches, mudflows, debris fans, and <br />' slope failure complexes (combinations of some or all of the above). Rockfalls may occur in the <br />upper portions of a slide, particularly where head scarps occur. The lower part of the slide, or <br />toe zone, may contain areas where rocks have accumulated. The toe zone may also contain <br />closed depressions that hold water and that are subject to hydrocompaction and the swelling and <br />shrinking of any expansive claystones. <br />Unstable Slope (Stabilized Landslide and Stabilized Earth Flow): An area where some type of <br />mass- gravity movement has likely occurred in the past, and where movement is likely, <br />particularly when highly saturated and/or disturbed. An "Unstable Slope" includes local areas of <br />potentially unstable slopes, soil creep, landslides, debris fans, rockfalls, earthflows, and <br />mudflows. <br />The majority of the geologic hazards within the SSCEL are stabilized earthflows and landslides. <br />The occurrences of historic and recent landslides are more limited. <br />3.3.5.2 Environmental Consequences <br />Proposed Action <br />Activities associated with the Proposed Action that may result in erosion or have an influence on <br />geologic hazards within the SSCEL include constructing temporary roads, improving existing <br />roads, and drilling exploration holes. <br />Potential for Erosion <br />The distribution and erosion potential of soil types at each exploration hole is shown in Table 3- <br />2. The potential for erosion is dependant upon soil type and topography. Surface textures, <br />subsurface textures, and slope would all affect mass movement potential (BLM and GMUG <br />2000). Soil types with percent slopes greater than 25 percent typically have medium to high <br />erosion potential, while those with percent slopes less than 25 percent have low to medium <br />erosion potential (BLM and GMUG 2000). As noted by Cryer and Hughes (1997), there is a <br />wide percentage range of slope associated with each soil unit. <br />Based on the erosion potential presented in Table 3 -2 and the distribution of soil types, the <br />improvement of existing roads and construction of temporary roads associated with the <br />exploration holes, have the potential to cause soil erosion. While the slope percentage is highly <br />variable in the SSCEL, exploration holes, as well as improved and temporary roads would be <br />situated on shallow to moderately steep slopes. <br />3 -42 <br />