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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 />I <br /> <br />poor condition. The existing Structure should be removed entirely before installing a new <br />Structure at an upstream location. <br /> <br />The existing StruCture is located at the end of a bend such that the approach conditions are <br />generally poor. The channel is marginally upstream and unstable downstream from the <br />structure. This S[nJcture serves as a check-drop with a drop of approximately 2.0 feet. <br />Erosion protection downstream of the Structure is currently inadequate both with respect (0 <br />configuration and material. The downstream plunge pool should be configured to provide <br />bank procection. energy management, and a smooth transition to the downstream conditions. <br />Those objectives can be largely achieved by upsU'earn location of the structure, proper riprap <br />sizing and placement below a new structure, and a reconfigured bank pcmecrion in the current <br />transition zone. <br /> <br />The proposed new strucrure consists of a I-foot thick reinforced concrete floor. with 8-inch <br />walls and wingwalls. and a 120' pipeline extension to the lower users. Some additional riprap <br />and bedding material would need [Q be imported to the site, and any broken concrete riprap <br />from demolition of the existing strucrure should be broken up such that me maximum <br />dimension is no greater man 3 times me minimum dimension. Riprap should be hand-placed <br />over bedding material to specified COntours to provide me previously mentioned hydraulic <br />objectives. <br /> <br />This strucrure was designed for throat width of 5.0 feet on the Decker side and 1.0 foot on <br />the lateral; a maximum discharge of 50 cfs on the Decker side with 2.0 feet of head and 2.0 <br />feet of drop; a maximwn discharge of 10 cfs on the lateral side with 2 feet of head; a 1.0 foot <br />ramp on both sides for a Replogle flume for flow measurements. The details of the Strucrure <br />are shown on Figure 9. <br /> <br />~IisceJlaneous Check Structures. There are six (6) locations between strucrure 7 and <br />strucrure I where i[ was identified that the installation of a check strucrure would be beneficial <br />[Q lhe operation of the ditch. The check strucrures are needed to raise me water level in the <br />ditch to facilitate the discharge into me headgates in these reaches. The structures will be a <br />concrete floor slab with a control wall across the ditch to act as the check and wingwalls to <br />retain the soil, Typically the strucrures will be approximately I5-foot in width and six to <br />eight feet in depm. Riprap and bedding will be placed on the downstream side to minimize <br />erosion. <br /> <br />The exact locations are not shown on the Vicinity Map included in Appendix A as the <br />locations may be varied after the ditch hydraulics are determined. Most of the locations <br />currently do nO( include a strucrure at this time. <br /> <br />Flood Control Structure <br /> <br />Strucrure Number 6. Strucrure number 6 shO\~n on the map in Appendix A is pan of a flood <br />control system at the confluence of Owl Creek with the Owl Creek Ditch. The system <br /> <br />Owl Creek Feasibility <br /> <br />Page 12 <br />