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Evaluation of Potential Subsidence Impacts of Longwall Mining in the Spruce Stomp Lease Area <br />to Aquatic Life and Water Supply <br />Section 6.1 summarizes potential impacts resulting from changes in channel profile, Sections 6.2 <br />and 6.3 address potential changes from fracturing and geologic hazards. <br />6.1 Impacts Resulting from Channel Profile Changes <br />As described above, the channel profile changes (over limited reaches) are expected to range <br />from 0 percent slope to 1.5 percent slope. These changes can be evaluated relatively; that is, <br />what is the relative impact of a 0 — 1.5 percent change to channel reaches with existing slopes of <br />3.0 — 10.6 percent? This question is explored below. <br />6.1.1 Changes in Fish Habitat <br />Based on the magnitude of absolute channel slope change (0 — 1.5 percent) and the typical <br />existing channel slope (3.0 — 10.6 percent), the areas with the most pronounced subsidence <br />impacts are not expected to have sufficient alteration so as to result in an observable change in <br />the ratio of pools:riffles. It is important to note that based on the maximum absolute slope <br />change of 1.5 percent and the minimum existing channel slope of 3.0 percent, there are no <br />reaches where slope change would cause impoundment (i.e., no portions of channel would have <br />positive slopes following mining). While existing pooled areas may be expanded slightly in <br />areas with flattened stream slope (see Section 6.1.2 immediately below), this would be countered <br />by pooled areas that would be contracted slightly in areas with steepened slopes. <br />6.1.2 Changes in Stream Flow <br />Based on modeling by Mr. Dunrud in this location and experience at other longwall mines in the <br />vicinity, stream flows are not expected to be altered by the Potential Project. Based on this, <br />adverse impacts to aquatic life resulting from decreased or increased stream flow are not <br />expected, nor will there be adverse impacts to water rights downstream. <br />6.1.3 Changes in Water Quality <br />As it pertains to channel profile changes, the primary concern with water quality would be <br />increased suspended solids. Based on the sediment transport analysis, the magnitude of change <br />to the creek's profile is not expected to be sufficient to elicit a significant change in sediment <br />121 - 014.000 Wright Water Engineers, Inc. Page 22 <br />January 2013 <br />