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PIPEUNE <br /> A new pipeline will be required to deliver the discharge from the new pump station <br /> to either Tenmile or Robinson Tailing Ponds. The proposed route of the pipeline is shown <br /> on drawing 1051.15b-1. The route of the pipeline was located such that it is contained <br /> entirely within the present and expected future process water system boundaries to control <br /> water within the process water system. Therefore, the Eagle River stormwater zone will <br /> not be impacted by the existence of the new pipeline. The construction specifications will <br /> include specific requirements regarding the handling of topsoil along the pipeline route and <br /> erosion control measures. <br /> The new pipeline would consist of approximately 5,100 feet of 20-inch diameter <br /> high-density polyethylene (HDPE) pipe and 1,500 feet of 24-inch HDPE pipe. HDPE pipe <br /> material was assumed in the preliminary design because of the high resistance to corrosion <br /> and chemical attack, and its inherent properties for attenuating transient surge pressure. <br /> The joints of the pipeline would primarily be butt-fused while connections in the vaults and <br /> at the pump station would be flanged. The entire length of the pipeline would be buried <br /> and bedded in coarse tailing sands to protect the pipeline and provide some insulation from <br /> freezing temperatures. <br /> The internal pressure design of the pipeline was based on a maximum flow of 7000 <br /> gpm. This is slightly greater than the pumping capacity of all three 629 pumps operating <br /> in parallel. The pressure rating of the pipeline was reduced (i.e. thinner wall sections) as <br /> the line elevation increases up the hill to the crest of No. 1 Dam. This results in <br /> considerable material cost savings. The flow velocity in the pipeline at a flow rate of 2700 <br /> gpm (one 629 pump) would be about four feet per second. Velocities would approach ten <br /> feet per second if all three 629 pumps were run in parallel. Surge protection becomes <br /> increasingly important as the flow velocity in the pipeline increases. <br /> Beginning at the new pump station, the pipeline generally follows along the north <br /> abutment of No. 1 Dam on a fairly steep ascent to a high point on the knoll at the west <br /> 16 <br />