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Mr. Ron Bottoms, City Manager <br />October 1, 2008 <br />Page 24 of 31 <br />k I o t z associates <br />prevention measures, prevention of excessive siltation, and capture of floatables <br />potentially entering the channel. <br />Drainage channel cross or are crossed by numerous roads, railroads, and pipelines. <br />Bridges and culverts are commonly used to make such crossings. Other <br />miscellaneous hydraulic structures such as flow splitters, drops, and constructed <br />bends can also be present in a channel. Crossings and miscellaneous structures, <br />pipelines, and, in particular, culverts and smaller bridges, can significantly <br />increase energy losses and reduce channel capacity. Improvements in structures <br />can have conveyance improvement benefits and, as well, lower tailwaters. <br />Structural modification to improve conveyance and capacity of a channel will <br />commonly • one • the following: <br />• • the size (diameter) • a culvert • the individual barrels • a culvert <br />by adding barrels or replacing existing culvert barrels <br />• Decreasing the length • culverts as •. • culvert replacement <br />• Upgrade of a bridge by 1) raising the low chord of the bridge, 2) increasing <br />the spacing between bridge piers, 3) reducing the bridge skew, or 4) <br />increasing the size of the opening under the bridge <br />• Adjustments around pipeline restrictions to reduce constrictions or limit <br />blockage <br />IZKIIRZ�i 1� <br />• To remove a property subject to flood damage from the floodplain by property <br />purchase, followed by removal of structures on the property <br />• To allow for development of sheet flow pathways for safe discharge of <br />ponded waters <br />• To use the property for construction of critical flood control facilities, such as <br />a detention pond <br />• Allow adjustment of floodway boundaries to facilitate development in other <br />areas <br />Table 4 presents a summary of representative unit costs for estimating the <br />potential costs of various conceptual projects for addressing particular drainage or <br />flooding problems identified for the City Wide Drainage Study. Estimated costs <br />