25F - AGMT - DELHI DIVERSION PROJECT

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Preliminary Design Report Addendum No.2 Channel Hydraulic Analysis Results Tables A -2 -1 and A -2 -2 show the HEC -RAS results for every cross section for the existing and proposed conditions, respectively. Figure A -2 -2 shows the existing and proposed conditions profile plots. Figure A- 2-3 shows the existing and proposed conditions cross - section flow depths. For the proposed conditions, the largest flow that can pass through the channel in which the depth everywhere in the channel is below 15 feet (which includes 1 foot freeboard) is the 1.2 -year storm. This is equivalent to a flow of 2,483 cfs in the upstream part of the channel and 2,633 cfs in the downstream part of the channel, at the in- channel flow diversion structure. 3.7.2 Diversion Facility Hydraulics This section summarizes the results of the hydraulic analysis for the diversion facility, which includes the intake, coarse - screen, fine- screen, sedimentation chamber, storage tank and outlet discharge structure, pump station and associated conveyance force mains. For conveyance pipeline by gravity and pressurized force mains, the C factor (Hazen - Williams coefficient) of 120 was used for all pipe sizes in this hydraulic study, which corresponds to a moderate pipe operational condition. The specified inside diameter dimensions, pipe length and associated valves, bends and other appurtenances were based on preliminary levels, and verification will be needed in further design stages. The proposed facility's hydraulic profiles for 0.4 cfs dry- weather and 100 cfs maximum design flow conditions are depicted in Appendix A -1 sheet PD -2. Detailed diversion facility hydraulic analyses results can be found in Appendix A- 3 Intake Pipe to Pre Coarse - screen Chamber Of particular importance is the need to provide redundancy for each component within the intake structure for the diversion facility. Various events could potentially reduce or eliminate the water supply normally available via a single intake (e.g., periodic maintenance on the intake structure). To adequately ensure a robust intake system, two 48" diameter RCP and channel side inlets are proposed for the preliminary design of the intake structure. The proposed intake pipe from the proposed intake to the proposed treatment facility is shown in Appendix A -1 PD -1. The intake consists of two parallel slide gate structures at the intake within the Delhi Channel, followed by two parallel 48 -inch diameter RCPs, approximately 50 feet long each. The estimated flow velocity for maximum flow of 100 cfs is estimated to be 8 feet per second (fps), and head loss is estimated to be 1.7 feet. The estimated velocity and headloss for dry- weather flow of 0.4 cfs are negligible. Coarse - screen and Baffle Wall The maximum velocity through the screen open area is 3.3 fps, assuming a clogging factor of 50 %. The headloss by coarse screen for maximum flow 100 cfs is estimated to be 0.27 ft. Flow velocity through the orifices after the coarse screen baffle wall is estimated to be 5 fps and headloss through orifices is 1.0 ft. The estimated velocity and headloss for dry- weather flow of 0.4 cfs are negligible. URS 13 25F -145