| OCR Text |
Show alternative proposal which would omit all structures in Hades Canyon and the pipeline along the canyon wall of the North Fork of the Duchesne River, and instead pump an amount of water equal to the instantaneous flow of the Hades Creek from the North Fork of the Duchesne River at the site of the North Fork Siphon up to the entrance portal of the Hades Tunnel. Using the existing trench for the siphon, almost no additional adverse environmental impact would result from this alternative. An economic analysis of this plan showed that the construction and pumping costs would be approximately three times the cost of the proposed plan. This additional cost would make this plan economically inferior. It appears that the plan that would be least harmful and still fill the project needs would approximate the following Forest Service alternative: " Leave the Hades Creek Diversion Dam where it is in the proposal but line the pool area with concrete to prevent saturation of the toe slopes of Red Pine Shale. Then run the pipeline down the canyon bottom of Hades Creek and thence along the flood plain of the North Fork of the Duchesne River and inject the water under gravity head into the bottom of the North Fork Siphon." 102 The Hades Creek Diversion Structure in the proposed plan would be a drop- inlet- type structure without a pool, which would need no lining as described above. The beneficial effects of this plan compared to the proposed plan would be that ( l) the scar caused by construction of the pipeline under this alternative plan would be much less visible than under the proposed plan and ( 2) the chance of slides being caused by construction of the pipeline on unstable soil would be greatly reduced. North Fork Siphon The North Fork Siphon would convey water from the outlet portal of the Stillwater Tunnel, across the canyon of the North Fork of the Duchesne River to the inlet portal of Hades Tunnel. Under the proposed plan the siphon would be located in almost a straight line between the outlet portal of Stillwater Tunnel and the inlet portal of Hades Tunnel. Only steel pipe would be used at this 581 |
