Laserfiche WebLink
Evaluation of Potential Subsidence Impacts of Longwall Mining in the Spruce Stomp Lease Area <br />to Aquatic Life and Water Supply <br />expected to change noticeably following subsidence. Further, since the net change of channel <br />slope over the Potential Project area should be zero, minimal constriction of the creek's wetted <br />perimeter at certain locations should be balanced by minimal expansion of the creek's wetted <br />perimeter at other locations. Based on the existing presence of steep slopes along the creek and <br />expected magnitude of slope changes, increased slope instability is not expected to a degree that <br />would result in impacts to the vegetation community. Adverse impacts to riparian vegetation <br />resulting from channel profile changes are not expected. <br />6.2 Potential Impacts Resulting from Surface Fractures <br />If the Potential Project were expected to have significant fractures within bedrock at the surface, <br />there could be a variety of impacts to aquatic life. Based on the geologic analysis performed by <br />Mr. Dunrud, surface fractures are expected to be minimal, as follows. <br />• Changes in Stream Flows - Based on the analysis of Mr. Dunrud, subsidence associated <br />with longwall mining is not expected to result in a change to stream flows. Thus, adverse <br />impacts to aquatic life and downstream water users from this activity are not expected. <br />• <br />Changes in Water Quality- Based on the amount of unconsolidated colluvium under <br />West Fork Terror Creek within the Potential Project area, fractures in bedrock would <br />appear to be sufficiently deep such that they would not be likely to result in altered water <br />quality as a result of enhanced weathering. Thus, adverse impacts to aquatic life are not <br />expected. <br />• Changes in Physical Habitat - Since fractures are not expected or persist within the West <br />Fork Terror Creek channel, adverse impacts to aquatic life are not expected. <br />6.3 Impacts Resulting from Geologic Hazards <br />When assessing the potential for new or increased geologic hazards occurring and adversely <br />impacting aquatic life, it is important to note that West Fork Terror Creek in the Potential Project <br />area is actively and continuously undergoing change from geologic hazards. During WWE's <br />April 2012 field visit, several areas with active or recently active landslides were identified. In <br />addition, more localized erosion and earth movement were occurring along the channel banks. <br />121 - 014.000 Wright Water Engineers, Inc. Page 24 <br />January 2013 <br />