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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 /> <br />existing strucrure is in poor condition and should be removed entirely before installing a new <br />Structure. All remnants of the present and former StrucUJres should be demolished and <br />convened to riprap. <br /> <br />The strucrure is located on a right-angle bend of the lateral, with relatively good approach <br />conditions. The main channel is generally stable upstream from the structure. Erosion <br />prmection in the lateral downslTeam of the Structure is currently inadequate. both with respect <br />to configuration and material. Meter gate measurement StruCOlres are recommended for each <br />of the turn-oulS and a right-angle check-drop should be constructed with a plunge pool below <br />to provide bank prolection, energy management. and a smooth transition [0 the downstream <br />conditions. Those objectives can be largely achieved by proper riprap sizing and placement <br />below the new Structure. <br /> <br />The proposed new StruClUre was designed with 8-inch thick reinforced concrete floor, with <br />8.inch walls and wingwaIls. Some riprap bedding material would need to be imported to the <br />site, and any existing broken concrete riprap should be further broken up such that the <br />maximum dimension is no greater than 3 times the minimum dimension. Riprap should be <br />hand-placed over bedding material to specified COntours to provide the previously mentioned <br />hydraulic objectives. <br /> <br />The slructure was designed for a throat width of 4.0 feet; a maximum discharge of 15 cfs at <br />a maximum head of 2.0 feet; with a hydraulic drop of 2.5 feet. The details of the Structure <br />are shown on Figure 6. <br /> <br />Structure 9 ~ Branch Oil'ider, The purpose of the Structure is to apportion flows between <br />me Branch and a west side lateral. The existing structure appears to have been designed for <br />a 60% [0 40% split from the main Branch and to the smaller lateral. Under current <br />operations, the maximum flow is estimated to be 15 cfs in the Branch and 3 cfs in the smaller <br />lateral. The existing srructure has been modified at least twice, and is in poor condition. The <br />existing strucrure should be removed entirely, before installing a new StruCture. The existing <br />[wo-foot slide gate could be overhauled and reinstalled. <br /> <br />The strucrure is located on a relatively straight reach of the lateral, so that approach <br />conditions are generally good. The main channel is generally stable, both upstream and <br />downstream from the structure. Erosion protection in the minor lateral downstream of the <br />structure in currently inadequate, both with respect to configuration and material. A weir box <br />measurement structure is recommended at the discharge point downstream of the 2 foot gate, <br />below which a plunge pool should be configured to provide bank protection, energy <br />management, and a smooth transition to the downstream conditions. Those objectives can be <br />largely achieved by proper riprap sizing and placement below a new structure. <br /> <br />The proposed new structure has an 8-inch thick reinforced concrete floor with 8-inch walls <br />and wingwalls. Some oprap bedding material would need to be imported to the site, and any <br />existing broken concrete ripeap should be further broken up such that the maximum dimension <br /> <br />Owl Creek Feasibility <br /> <br />Page 10 <br />