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project. For input to the model, we will use the peak flow results obtained from the IJNET <br /> model developed in the preliminary hydraulic analysis. We will use the 100-year water <br /> surface elevations from the UNET model to identify the base flood elevations (BFEs) for the <br /> Diversion Channel and the A Channel upstream of 1135 project levee. We will use the 100- <br /> year water surface elevations from the HEC-RAS models to define the BFEs for the <br /> Diversion Channel, the A Channel, and the Greenhill Tributary downstream of the 1135 <br /> project. The BFEs for the Diversion Channel downstream of 1135 project levee will be <br /> based on the hydraulic results for four different levee configurations. <br /> The procedures involved in the hydraulic analyses are explained below. <br /> Step 1. Modify the updated UNET model to incorporate <br /> • the bike path and pedestrian bridge in the 1135 project area <br /> • the inflow from the Greenhill Tributary <br /> Step 2. Run the modified UNET model for the 100-year storm event and generate peak flow <br /> information for modeled cross sections on the A Channel and the Diversion Channel <br /> downstream of 1135 project levee <br /> Step 3. Develop separate HEC-RAS models for the Diversion Channel and the A Channel <br /> downstream of the 1135 project using the peak flow data generated by the UNET <br /> model <br /> Step 4. Modify the HEC-RAS model for the Diversion Channel downstream of Royal <br /> Avenue to represent four levee configurations <br /> Step 5. Develop a HEC-RAS model for the Greenhill Tributary from Terry Street to the <br /> confluence with the A Channel based on the information provided by the City <br /> Step 6. Define the BFEs for the Diversion Channel, the A Channel and the Greenhill <br /> Tributary <br /> Step 7. Perform the required floodway analysis for the Diversion Channel, the A Channel and <br /> the Greenhill Tributary <br /> A detailed breakdown on the additional budget needs for the hydraulic analysis is presented <br /> in Table 2. We estimate that the budget implications from the remaining work would be <br /> approximately $39,600. This estimate is based on the following assumptions: <br /> <br /> • The Corps will certify the 1135 project levee; <br /> <br /> • FEMA will accept the Corps' certification letter; <br /> s:\proj94\945042°d\amazonFEMA\contractaddendum.doc <br /> 07/13/01 <br /> 4 <br /> <br />