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CHAPTER III ALTERNATIVES Fifty-two lateral and thirty farm turnouts would be replaced. The initial capacities of the lateral turnouts would range from 1 to 34 cfs, and the farm turnout capacities would range from 1 to 6 cfs. West end portion of the Government Highline Canal.--The west end por- tion of the Government Highline Canal extends for 7 miles from the end of Stage One to the terminus of the Government Highline Canal 6 miles north- west of Mack. Due to the relatively small flows, the last mile of this reach would be placed in pipe and would be considered a lateral served by the canal. Major existing waterway structures in this section include a 360-foot-long concrete flume across Mack Wash and a mile-long siphon under East Salt Creek. A check and watteway structure would be constructed at both the East Salt Creek and the Badger Wash siphons. One centerline check structure would be added in the 120-cfs reach. Ten lateral and eighteen farm turnouts would be replaced with eight lateral and thirteen farm turnouts, with the initial lateral turnout capacities ranging from 3 to 40 cfs and the farm turnout capacities from 2 to 6 cfs. Cross-Drainage Facilities Cross-drainage facilities would be constructed to protect the • membrane-lined canal. Present cross-drainage facilities in the minor drainages consist of a series of culverts which are in poor condition due to age, siltation, and poor maintenance and would be replaced with a detention ditch and dike system. As in the Stage One area, the cross-drainage system would be con- structed uphill from and parallel to the canal. Detention ditches de- signed for a 25-year flood would collect floodflows and convey them to drainage channels where they would cross either under the canal through concrete boxes or corrugated culverts, cross over the canal through overchutes, or enter the canal through drain inlets. Four detention dams located north of the cross-drainage detention ditch and dike system have been designed for 100-year flood protection because the potential for hazard to life and property damage from failure of these dams is significantly greater. The system would consist of 34.5 miles of detention ditches and dikes and four detention dams designed for a 100-year flood, which would be used to create small impoundments for leveling out stormflows in natural drainages. The east end portion of the Government Highline Canal would have 6.5 miles of detention ditches and dikes starting 3.5 miles downstream of the Price-Stub Ditch Pumping Plant and two detention dams located at Moulton Valley and Lewis Wash. The middle portion of the Government Highline Canal would have detention ditches and dikes along its entire 20-mile length, plus two detention dams located at Leach Creek and the East 24