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Show Canal- Siphon System The canal- siphon system would sbustitute canals and siphons in lieu of the tunnels and pipelines of the proposed plan. The canals would involve difficult construction across the faces of cliffs, across talus slopes, and through dense timberbrush areas and would be about 190 miles long or approximately five times the length of the tunnel- pipeline system proposed. Undesirable construction scars along its entire length, hindrance to wildlife migration, increased seepage losses, and increased difficulties in maintaining effective operation during winter periods would be some of the disadvantages of the canal- siphon system. On the other hand, the tunnel- pipeline system, which would be almost completely underground, would be more efficient and less disruptive to the environment both during and after construction. Tunnel- Pipeline System Many alternative studies were made to determine optimum alinement of the Strawberry Aqueduct. Two elevations along the Strawberry Aqueduct govern to a large extent the location and elevation of the aqueduct and individual diversion and feeder lines into the aqueduct. The first is the normal water surface elevation in the enlarged Strawberry Reservoir, and the second is the elevation of Rock Creek at the primitive or wilderness area boundary, which would determine- within limits- the normal water surface elevation in Upper Stillwater Reservoir. The relatively small difference in elevation between the two reservoirs governs the design slope and restricts the location of the Strawberry Aqueduct within these limits. Alternatives within these limits are described below. i » Stillwater Tunnel The Stillwater Tunnel heads at Upper Stillwater Reservoir and is the uppermost section of the Strawberry Aqueduct. The tunnel passes through the drainage divide separating Rock Creek from the North Fork of the Duchesne River. The South Flank fault intercepts the tunnel alinement approximately 0.8 miles downstream from the tunnel inlet. In an attempt to avoid the fault, an alternative plan was considered which would relocate the tunnel inlet portal approximately a mile downstream from the proposed location. This would require increasing the capacity of the Upper Stillwater 577 |
