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REQUEST FOR TECHNICAL REVISION Mine ID# M-1993-035 Mine Name: Swan River Resource Location: Summit County These characteristics formed the basis for the developed Plan. The following Table provides a summary of the proposed channel characteristics per the Plan. Summary of Proposed Channel Characteristics Cha nel Length 4,810 feet Channel Slope 2% (Avg.) Bankfull Flow 103 cfs Avg Bankfull Width 20—25 feet Avg Depth (Riffle Sections) 1.5 feet Pool Spacing 168 feet(5-7 x bankfull width) Width/Depth Ratio >12 Entrenchment Ratio >2.2 Sinuosity 1.2 Groundwater Intercept As part of the restoration reclamation assessment, piezometers were installed throughout the Swan River Valley in order to understand the location and seasonal variation of the local groundwater table. Currently the Swan River is both a gaining and losing stream over individual sections at high flows;the stream generally runs subsurface at all other times. Overall, data suggests that lowest recorded groundwater and proposed streambed elevations are generally very similar in throughout the Project Area. Groundwater is estimated to be below the proposed streambed for approximately 85% of the Reach B reach (i.e.,final stream bed elevation is above the groundwater table). The upper 15%of Reach B streambed should be below groundwater for most of the year (excluding winter). Low Permeability Layer One of the important aspects of the planned stream restoration will be to ensure that flow is maintained at the surface and not allowed to go subsurface in the dredge material.The streambed is designed to be generally below the lowest recorded groundwater elevation.As part of construction, a low permeable layer zone will be incorporated.The low permeability zone will be constructed using a combination of finer mixed excavated material to create a substrate with low vertical permeability.This finer material will help to inhibit vertical migration of the water, maintaining flows at the surface. If the channel is set at an elevation that intercepts the groundwater and fine material underlies the stream,water will generally remain at the surface. Over time as more fine sediment flushes into the system,the system will become naturally perpetuating. Aquatic Habitat Restoration The restoration reclamation plan focuses on creating a healthy, diverse, and self-sustaining aquatic environment which includes specific habitat requirements for native cutthroat trout and other species.While native cutthroat trout are not the dominant species present, this species serves as the target species providing the basic habitat requirements for all regional trout species. The restoration reclamation plan also incorporates two types of 4 of 7