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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 <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />provided at appropriate high points and other locations along the pipeline. <br />The air release and vacuum valves will need to be separated from the main line <br />so that repair or replacement of the air valve will not require the line to be <br />taken out of service. Orain valves at selected low points will also be <br />required so that the line can be drained if necessary. Isolation valves at <br />various locations along the main supply line are recommended so that selected <br />segments of the line can be drained if necessary, rather than requiring <br />draining the entire line to allow servicing a limited section. There will be <br />at least three line segments of approximate equal length selected for <br />isolating. Valved drains will be located at the seqment low points to allow <br />full 1rainage anti flushing. Isolation or "quad" valves are recommendeti on <br />each side of each automatic control valve so that the control valve can be <br />serviced or replaced without draining the entire line. <br /> <br />These in-line valves and drain outlets will be housed in appropriate vaults or <br />manholes, and located at pOints where access does not interfere with <br />activities of private property owners. The vaults or manholes will be secured <br />to assure controlled access to the valving system. There will also be valves <br />and pipe connections between storaqe tanks to allow drain-down to lower tanks, <br />or for drainage to flush and clean the tanks. <br /> <br />3.5 Pipe Type and Class <br /> <br />Several pipe materials have been considered for use in the Towaoc water supply <br />line. Those still considered suitable for use include ductile iron, <br />pretensioned concrete cylinder, mortar lined and coated steel, PVC, and <br />fiberqlass. Factors considered in comparinq these materials included the <br />del i vered pi pe cost, corrosi on resi stance, costs of corrosi on D~otecti on (if <br />needed), pressure class, availahility, durability, and factors inf1uencinq <br />install ati on costs such as beddi nq requi rements, and hanrll i ng care <br />requi rements. <br /> <br />All types of pipe will require monitoring at the plant by the engineer during <br />manufacture. <br /> <br />3-17 <br /> <br />1060c <br />