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<br />. <br /> <br />. <br /> <br />. <br /> <br />bridge without pressure flow, generally up to the low chord of the bridge, The potential overflow is <br />the flow that can travel around the bridge and/or overtop the roadway. For example, the abandoned <br />railroad bridge at La Boca has a maximum hydraulic capacity of approximately 15,100 cfs. Long <br />before the maximum capacity is reached, the highway would be overtopped to the west of the bridge, <br />At the maximum bridge capacity, the potential exists for 8,600 cfs to overtop the railroad berm to the <br />west of the bridge, <br /> <br />Table 5 lists each structure, its location, cross section, type of structural data available, the <br />bridge's approximate maximum hydraulic capacity, and the amount of potential overflow, <br /> <br /> TABLE 5 <br /> STRUCTURAL CROSSING INVENTORY <br />Structure Location Cross Data Source Maximum Potential <br /> Section Hydraulic Overflow <br /> Capacity <br /> (cfs) (cfs) <br />Bear Dance Bridge Ignacio 1702.5 Field Inspection by USACE 800 N.A <br />State Route 151 Bridge Ignacio 1672.5 Field Inspection by USACE 9,000 2,000 <br />County Road 322 Bridge Upstream of La Boca 1362.5 Field Inspection by RTI 1,700 5.300 <br />Abandoned RR Bridge La Boca 1292,5 Field Inspection by RTI 15,100 8,600 <br /> <br />Hydraulic Model <br /> <br />The Los Piiios River was modeled using the U.S Army Corps of Engineers Hydrologic <br />Engineering Center's River Analysis System (HEC-RAS), This software is capable of performing <br />water surface profile computations for one-dimensional steady state gradually varied flow, The basic <br />computational procedure is based on the solution of the one-dimensional energy equation and <br />Manning's Equation, and in regions of rapidly varied flow regimes the momentum equation can be <br />used, The software is capable of modeling sub critical, supercritical, and mixed flow regime water <br />surface profiles, <br /> <br />Subcritical flow is the predominant flow regime in this reach, Several of the roadway and <br />bridge structures will, however, induce a rise in the water surface, producing a supercritical regime <br />downstream of the bridge, Therefore, the mixed flow regime option was selected for this analysis, <br /> <br />Although the flow channel splits at several locations along this reach, it was determined that a <br />split flow analysis would not be necessary because there are a number of crossover channels <br /> <br />14 <br />