Feasibility Study, Enlargement of Julesburg Reservoir

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-10- subject to erosion. These concerns can be alleviated by grouting the permeable portion of the bedrock, by replacing the permeable bedrock with compacted impervious fill, or by constructing a slurry trench cutoff. The selected cutoff is the most practical method for rehabilitation of the existing embankments given the in -situ conditions and the cost implications. The slurry trench should be constructed into the unweathered portion of bedrock. 3.3.3 Slope Stability Recent stability studies were performed on the relatively; steep uup °s"tream slopes of Dam 2 and Dam 3. The analyses indicate that in event of rapid drawdown exceeding 5 feet, the upstream slopes will have an inadequate factor of safety. Therefore,,flattening of the upstream slopes of Dams 2 and 3 should also be part of the rehabilitation. 4.0 DESIGN PARAMETERS 4.1 General The proposed rehabilitation and enlargement project would -involve three general alternatives. These include: • Stabilization of Dam 1 to a condition equivalent to the current condition of the remaining facility and/or, rehabilitate the existing dams and foundations to current day ;standards to the extent, reasonably possible, storing water at the normal operating level of Gage 24.0. • Rehabilitate and /or`reconstruct the existing dams to meet current dam design criteria to the extent reasonably possible and increase the normal operation level by 3.5. • Rehabilitate and /or reconstruct the existing dams or construct new dams to enlarge the reservoir and increase the normal operation level by 6.5 feet. 4.2 Hydrologic and Hydraulic 4.2.1 Freeboard The dam freeboard provided for wave height, wave runup and flood surcharge storage should be 8.0 feet. The addition of a 3 -foot high parapet wall for additional wave protection is PrePorts \97- 1- 500.nk