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<br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />.' <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br /> <br /> <br />RosIe)! Wash Draina$e },;Jaster Plan. <br /> <br /> <br />Phase 2: Alternative Drainage Facility Evaluation <br /> <br />upstream side of the Government Highline Canal from 34 Road on the west to 34 6/10 <br />Road on the east (see Figure 5). <br /> <br />The ponding upstream of the G Road culvert inundates a number of structures, primarily <br />in the vicinity of G Road and 34 Road. However, the undersized culvert also significantly <br />reduces the downstream discharge, thereby reducing the downstream flood hazard. This <br />effect has been considered in the evaluation of downstream structures. <br /> <br />2.2.2 Government Highline Canal <br /> <br />The siphon under the Government Highline Canal has limited capacity. While inadequate <br />to convey the theoretical flow reaching the site, several hydraulic elements in the <br />u}Jstream Watershed 'limit the impacts of this undersized crossing. The overflows of the <br />Stub Ditch drainage channel divert some flows to the south via the Hency Waste. This <br />reduces the flow along the upstream face of the Canal from reaching the Government <br />Highline siphon. The G Road culvert also restricts the amount of flow reaching the <br />siphon. However, the depth of water necessary to convey the actual flow rate through the <br />siphon is such that water here mingles with the water trying to flow through the G Road <br />culvert, creating one large pondin!? area. Figure 5, which depicts ponding in the vicinity <br />of G Road, also shows the area of ponding that can be attributed to the siphon at the <br />Government Highline Canal. <br /> <br />2.2.3 Hwy 61UPRR <br /> <br />The culvert under Hwy 6 and the UPRR severely res.tricts discharges along Bosley Wash. <br />This culvert is the hydraulic equivalent of a 48-inch pipe, but is comprised of several <br />different sections joined end to end. The culvert is capable of handling 100 cfs, but <br />cannot handle the full discharge of 190 cfs. Water in excess of the culvert capacity ponds <br />along the north side of the tracks and spreads over a wide area (see Figure 6). The area <br />inundated by the ponded water extends from the culvert almost 1500 feet east and west <br />along the tracks. <br /> <br />~-- - '--'-,~ -:<";:', ~"';'."" -~:-':, :.,-,:';" -....... .~\ - <br />"'.'n_'_ ,_ . _, <br />""-.... .""'-"--~~'"",,~,;,",",~- <br /> <br />:~: <br /> <br />Q <br /> <br />Page 5 <br /> <br />(----'. <br />r4 <br />\~ <br /> <br />@'1 <br />