2007-04-05_GENERAL DOCUMENTS - M1977493 (2)

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Climax Mine Arkansas River Restoration data, taking into account peak design flows, flow velocities and sediment transport to design appropriate individual restoration treatments and structures. Our designs are structurally sound, yet maximize the use of natural materials (rock and gravel on-site, root wads/balls, and logs) and native plants and vegetation to achieve stabilization and habitat enhancement. Our stream relocation and restoration design philosophy incorporates soft engineering, hard engineering and biotechnical engineering. Using this approach, the Habitat Team will restore approximately 2,000 feet of the East Fork Upper Arkansas River and the surrounding ecosystem to a close approximation of its remaining natural potential supported by the existing hydrology, climate and geology. Our goal is to end up with a stable but dynamic system that allows the restored stream to migrate vertically and horizontally, while optimizing the structural and non- structural measures necessary to stabilize the reach. 2.2.4 Retention of the Existing Pipeline The Habitat Team's design includes retaining the existing pipeline throughout stream channel construction. To provide greater assurances of success for the newly constructed channel the pipeline will be utilized during the initial monitoring period to moderate stream flow. Additionally, to allow future mining in the Storke Yard the pipeline will be sealed at each end and placed in a dormant state. Earthen materials will be used at the upstream side to create a natural meander, diverting water away from the entrance to the sealed pipeline. Currently, no technical analysis has been performed on the existing pipeline to quantify its condition. However, the pipeline is, by all appearances, functioning and has been modeled to pass 285 cfs. The advantages of pipeline retention are described below. First, by leaving the pipeline intact, it will be possible for the Habitat Team to regulate the discharge of water into the newly constructed stream channel, inundating riparian vegetation while limiting the amount of flow and sediment entering the watercourse. Historic base flow of the Arkansas River downstream of the project area must be maintained throughout the term of the project. Maintaining this base flow has the potential to seriously limit the available water to saturate the reconstructed channel bed, fill the lake and supply critical water to aquatic, riparian and wet meadow transplants. Due to typical late-season flow volumes in the Arkansas River, the predicted water volume required to fill the existing lake to design levels and saturate the channel bed in the fall of 2007 could affect requisite base flow in the existing channel downstream from the project area. Therefore, releasing limited flows during 2008 snow melt and spring runoff will help fill the lake and saturate the entire reconstructed channel bed without adversely affecting base flow volumes downstream into the Arkansas River. Second, retaining the pipeline will benefit brook trout recovery efforts. The Habitat team will be responsible for oversight and implementation of a flow regulation plan to provide greater assurances to the viability of the brook trout population. Benefits of retaining the pipeline for trout reintroduction include: • Regulating stream flows to improve trout population viability by increasing fry survival rates during fry emergence; • Maintaining adequate water depths for spawning habitat (0.6-1.0 ft); and Improved ease of modifying in-channel habitat as necessary following the initial construction. Third, it is likely that portions of the existing pipeline reside in or below the ground water table that would necessitate dewatering the trench and treating the water. Therefore, the removal of the pipeline will create unnecessary problems and costs to be associated with the project. Habitat Team March 28, 2007