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Vegetation Approximately 7 acres of vegetation could be removed through construction of the degasification sells. After rehabilitation of the sites, the over- all impact should not be significant. Hining's short-term effect on palustrine vegetation cannot be accurately predicted. Subsidence is not expected to noticeably affect flows in Red Wash. Ten- sion cracks which appear in the Red Wash channel would be expected to rapidly fill with sediment and present no impedance to surface flows. Since underlying strata ace believed to be resistant to water movement, accelerated percolation is not anticipated. Slumping in the channel is expected to approach 4.3 Eeet over Longwell sections on the western edge of the lease, and is not expected to exceed 1.5 feet on remaining channel overlying the room and pillar operation. It is presumed that differential slumping over active mine areas in the I.!!U would temporarily impound a portion of Elow during high runoff events, or restrain low flows. Due to this drainage's tendency to transport extremely high sediment loads during runoff events (measured maximum--256,000 mg/1; WF-U Mining Permit Applica- tion data), deposition would be expected to rapidly fill such depressions. If this proves to be the full complement of impacts imposed on the Red Wash channel, continued maintenance of current palustrine vegetation would be expected. However, it is possible that subsidence events could induce changes in stream gradients and/or channel stability and alter the extent and condi- tion of wetland vegetation in the short-term. Elevation differences at the interface between subsidence-influenced and unaffected channel (north- ern boundary of the lease) may initiate headcutting upstream. Attendant base level lowering and channel incision may tend to reduce lateral avail- ability of moisture for plant maintenance. Additionally, it is not known what effect the subsidence wave would have on streamside substrate. Abrupt tilting could destabilize channel banks and aggravate bank sloughing. Over the long-term, channel configuration and sites available for vegeta- tion establishment would likely assume characteristics similar to present via erosional processes. Although incorporation of this lease with WF-U's LMU would increase Red Wash involvement by 50 percent, the ultimate affect relative to the extent of Red Wash currently sub,~ect to subsidence would be negligible. Direct removal of palustrine vegetation could occur during mechanized channel work proposed by WF-U to maintain uninterrupted flow to the White River. Based on the composition of Red Wash's depauperate wetland associ- ations, limited removal would be of no consequence, however, channel response to subsidence should be evaluated to determine iE such work is necessary or prudent. 17 c