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pipelines from each of the cutoff drains will discharge into the boundary cutoff manhole <br />which will, in turn, discharge into the first chamber of the siphon vault. <br />'The collection piping has been designed so that each drain trench is redundant. <br />Separate pipelines connect from each of the four upper drain trenches to the Boundary <br />Cutoff Manhole, and each pipeline will be fitted with a tee and perforated nipple as it <br />passes through progressively lower drain trenches (Detail 3, Drawing No. 3DS-2). If any <br />pipeline plugs between the trench drain and the boundary cutoff manhole the seepage <br />water from that drain will flow to the perforated nipple from another pipeline and that <br />pipeline will provide redundant collection. <br />Each drain trench will be equipped with clean-out risers at each end and <br />where the discharge pipe to the boundary manhole begins. <br />Connection at Existing Seep Water Pipeline (Reference Drawing No. 3DS-5) <br />The existing seep water pipelines are pressure tested from time to time. <br />Therefore, the connection of the two new 3-inch pipelines must be capable of being <br />isolated by valves to allow that pressure testing. In addition, the new pipelines will be <br />designed for similar pressure tests. The connections to the existing seep water pipeline <br />include the following features to allow pressure testing of any of the four pipelines that <br />will be affected: <br />• The connection to the seep water pipeline will be a pressure-rated HDPE Electro- <br />fusion Saddle fitting, or a stainless steel mechanical saddle fitting, whichever is more <br />cost effective. The fitting will be rated for pressure to the same rating as the existing <br />seep water pipeline. <br />• The saddle fitting can be isolated from the new pipes, allowing pressure testing of <br />the 10-inch pipeline, by closing a stainless steel butterfly valve. <br />• The two new pipelines will be tee'd together in the manhole so that they share the <br />entry point (the saddle fitting). The same stainless steel valve can be closed to <br />pressure test the two new pipelines. <br />• If the nearest 10-inch seep water pipeline is being tested, a drain outlet connected to <br />the new pipelines can be opened so that the water through the new 3-inch pipelines <br />can be temporarily pumped into the second seep water pipeline, as shown on Details <br />3 and 4. <br />Drainage Trench Design (Reference Drawing No. 3DS-2) <br />The seepage faces of the trench drains are oriented perpendicular to the flow to <br />be intercepted to maximize the exposure and therefore the collection efficiency. Five <br />Henderson Operations, Mill Site 9/7/10 <br />No. 3 Dam Seep Mitigation, Design Report Page 6