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<br />I <br />I- <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />II <br />: I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />6. <br /> <br />Constructina Relief Bridaes or Extra Spans on the Main Bridge. This <br />approach of providing additional waterway to relieve existing flow <br />conditions is essentially a design problem and the guidance in Chapters III <br />and IV are applicable to its implementation. In some locations with very <br />unstable banks, the addit~on of spans May be MOre cost-effective than <br />attempting to stabilize the channel slopes in the vicinity of the bridge. <br /> <br />\ <br /> <br />SUMMARY - The foregoing discussion of countermeasures presents a wide variety of <br />concepts and approaches for addressing scour problems at bridges. The <br />Interdisciplinary team needs to collect and evaluate information about the <br />behavior of the stream and its flood flow patterns through the bridge so that <br />they can select the most appropriate countermeasure for the particular set of <br />site conditions under study. An FHWA publication entitled, .Countermeasures for <br />Hydraulic Problems at Bridges (Volume 2, Case Histories),. is recommended as a <br />guide for reviewing the performance the types of countermeasures discussed above. <br /> <br />63 <br />