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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />'I <br />i I <br />I <br />I <br />I <br />I <br />I <br />II <br />I <br /> <br />Pipe for each of the proposed alternatives will be rated for 200 ft of hydraulic head. This pressure <br />rating was determined based on the hydraulic grade lines found in Western Engineers report <br />entitled "Feasibility Study, Plateau Creek Pipeline" dated October, 1987 and adding an additional <br />50 foot of head for hydraulic surge. The head losses within the tunnel should be frictional head <br />losses only. It is estimated that the total frictional head losses will vary between 0.5 and 3 feet. <br /> <br />Based on our preliminary analysis, a 42 inch diameter pipe will be adequate to meet the future <br />water demands. However, the capacity of the tunnel alternatives is mainly regulated by the hydraulic <br />characteristics of the entire pipeline system. In order to meet the proposed future water demands, <br />hydraulic energy lines should be developed for the entire delivery system including each of the <br />tunnel alternatives. The optimum pipeline diameter and configuration can then be determined <br />based on capacity/cost considerations during the hydraulic evaluation and design project phases. <br /> <br />It is anticipated that an additional 1,600 ft of 30-inch pipeline will be installed parallel to the existing <br />24 inch pipeline up to a junction box at the east portal for both tunnel alignment alternatives as <br />shown on Figure 5.1. This installation proceeds up a steep slope and will require some blasting and <br />special construction practices to bury the pipe. The special construction will include anchoring the <br />pipeline to the slope to prevent a catastrophic failure should a minor leak occur. Tunnel Alignment <br />A will require a junction box at its west portal to connect it to the existing 24 inch diameter <br />pipeline. Tunnel Alignment B will require 350 ft of new 42 inch pipeline be installed from the west <br />portal to a junction box at the existing 24 inch pipeline as shown on Figure 5.1. It is anticipated <br />that this 24 inch diameter descending pipeline will be upgraded as other sections of downgradient <br />pipeline system are upgraded. For cost estimating purposes the descending pipeline has been <br />assumed to be 42 inch diameter from either western portals to the western project terminus point. <br /> <br />The geologic conditions as previously described in Section 4 are very suitable for tunnel <br />construction. The existing bedrock is quite stable and it is anticipated that the tunnel can be <br />excavated with only a minor amount of temporary support. Additional investigations would need <br />to be performed to assure that the tunnel is placed in a stable geologic environment similar to the <br />original Plateau Tunnel construction. However, based on the original tunnel and initial geological <br />investigations performed it is believed that no major geological problems will be encountered. The <br />proposed tunnel is in stable rock and no groundwater is anticipated to be present. <br /> <br />5.5 Construction Considerations <br /> <br />It is anticipated that the tunnel will be constructed using conventional methods similar to that for <br />the original Plateau Tunnel. A rail will be laid on the tunnel invert and a battery-operated <br />locomotive will haul out rail-mounted muck cars. The typical excavation sequence will involve <br /> <br />17 <br />