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<br />The existing siphon pipeline crossing of Smith Arroyo apparently was designed in <br />1918. Copies of the original 1918 siphon pipeline system design plans are presented in <br />Appendix A. The existing pipeline crossing is a below-grade concrete-encased wood <br />stave siphon pipeline. Smith Arroyo is an intermittent streamcourse.i Existing <br />reinforced concrete inlet and outlet structures for the existing irrigatfon pipeline <br />crossing are located at the left-bank and right-bank sides of Smith A!rroyo, <br />respectively. The actual date of the pipeline and appurtenances cons~ruction is <br />unknown but probably occurred soon after the system was designed. The existing <br />siphon pipeline system consists of an existing nominal6-foot diameter wood stave <br />pipeline approximately 300 feet long (plan view distance) that is concrete-encased with <br />an installed blow-off and drain valve assembly. <br /> <br />I <br />I <br />I' <br />I' <br />I' <br />I <br />I' <br />I <br />I <br />It <br />I' <br />I <br />I' <br />I' <br />I <br />I <br />I <br />I <br />I <br /> <br />for a future-year replacement of the existing but badly-deteriorated pipeline system. <br /> <br />A partial or total collapse of the buried pipeline could disrupt the deHvery of needed <br />irrigation water to downstream users for several days until effective system repairs could <br />be made. Approximately two-thirds (2/3) of the High Line Canal Company members <br />farm downstream of the Smith Arroyo siphon site. Based on providing 2/3 of the 501-cfs <br />water right downstream, the shareholders require a minimum flow of 334 cfs. <br /> <br />Should the existing siphon pipeline system ever collapse (either pa.rqally or totally) <br />because of its badly deteriorated physical condition, about 15,000 acres of the farm <br />lands below Smith Arroyo would be adversely impacted by the loss of irrigation water <br />delivery. <br /> <br />The High Line Canal Company later thought that the pipeline replacement could be <br />either an in-place removal and demolition of the old pipeline with a pew pipeline <br />installation to replace the old pipeline, or a new pipeline at some offset location <br />parallel to the existing pipeline alignment which would in turn tie into the existing <br />reaches of the irrigation canal both upstream and downstream of S1l)ith Arroyo. <br /> <br />EXISTING FACILITIES <br /> <br />Copiesofthe 1918 design drawings for the existing Smith Arroyo siphon pipeline and <br />appurtenances are presented in Appendix B. The existing pipeline system includes a <br />nominal 6-foot diameter wood stave pipe that is concrete-encased with a blow-off and <br />drain valve assembly. The existing inlet and outlet structures are both of reinforced <br />concrete, and are for all practical purposes structurally sound. . <br /> <br />An existing "trash rack system" is made up of six (6) large drill rods in parallel that <br />rest in place against the inlet structure. When sufficient debris is collected by these <br />"trash rack rods" at the inlet structure end and in the canal reach immediately above it <br />(that reportedly occurs often after significant contributing storm water runoff in the <br />canal itself), the existing carrying capacity of the existing siphon pipeline is reduced <br />accordingly. When trash plugs the pipeline, a canal gate located abopt 300 feet <br />upstream of the siphon entrance is opened to allow some or all of th~ canal water to <br />flow into Smith Arroyo until the trash is removed from the siphon entrance. <br />