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4.0 PROJECT DESCRIPTION AND ALTERNATIVES ANALYSIS <br /> The former structure, believed to have been constructed in the early 1920s, • comprised of <br /> three major parts: canal control gates (3), a radial gate to flush sediment, and a spillway to <br /> control flow and level upstream of the canal measurement flume. Typically, the canal control <br /> gates were kept open, while the spillway was checked to increase the upstream water <br /> surface elevation. The radial gate was typically only used at the beginning and end of the <br /> season to flush out sediment. The US Army Corps of Engineers operates a flood control <br /> levee and gates immediately downstream of the structure. These gates are typically always <br /> kept open and only closed during floods. Four rehabilitation alternatives were evaluated, <br /> ranging from no action to complete replacement of the structure with modern controls. A <br /> description and comparison of each alternative follows. <br /> Figure 3: Original Spillway Structure <br /> /,1,..,k i**- <br /> �. w e*,,':* a <br /> pd <br /> 'w as; <br /> b ..fir 4 1 �v <br /> . ' + 1e'did <br /> :' ", "ii,- �t ifs <br /> r R« * Jw y <br /> r <br /> a <br /> "- <br /> a ¢ w .w <br /> ! '. w <br /> i4 t ' Via, <br /> ter,e. <br /> M w * .r '''''3 <br /> •. 1c earth <br /> September 2014 Draft <br /> Page 1 19 <br /> 1 <br /> 1 <br />