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WEBER John J <br /> From: WEBER John J <br /> To: WESTFALL Wayne T <br /> Cc: ETTER John F; MORGAN Dick A; KLOPE Paul W <br /> Subject: RE: A -2 Channel culvert design at Golden Gardens <br /> Date: Wednesday, April 19, 1995 1:41 PM <br /> Wayne, thanks for your response to the information I sent over. 1 will certainly put a hold on the DSU Corps <br /> permit until we have had a chance to discuss the project further and any alternated design approaches. When t 1 <br /> here from Paul Klope on the in -house design option I will get together with Dick Morgan and John Etter to <br /> re- evaluate the project. Maybe we need to reconsider the option of another bridge crossing? <br /> -john W. <br /> From: WESTFALL Wayne T <br /> To: WEBER John J <br /> Cc: KLOPE Paul W; LARSEN Tom C <br /> Subject: A -2 Channel culvert design at Golden Gardens <br /> Date: Wednesday, April 19, 1995 1:21 PM <br /> Paul, see note #7 first. <br /> John, I'm glad you called. I'm afraid I have bad news. Your <br /> design appears to have some fatal flaws: <br /> 1. The flow to use for design needs to come from Table <br /> 3.10 rather than Table 3.4, which means design flow should <br /> probably be 900 cfs (25 -year future) or 1197 cfs (100 -year <br /> future) rather than 40 or 50cfs, which it appears you used. <br /> 2. The concept of 2 small pipes for low flow MAY be OK, <br /> but we need to think that through over here in Engineering. <br /> Also, see #4 below; FEMA may have something to say about it. <br /> 3. No matter what design flow and pipe size we decide <br /> to go with, I feel the roadway should be structurally designed <br /> so that overtopping floodwaters CANNOT wash it away, which <br /> would be highly likely with your design. <br /> 4. The A -2 Channel is a major waterway and was mapped by <br /> FEMA in the 1986 floodplain study. Unfortunately, it lies <br /> outside the City limits so I have no information about the <br /> FLOODWAY delineation for it. The FLOODWAY probably lies <br /> completely within the channel banks, but you or the project <br /> designer need to check with Lane County about this. FEMA has <br /> always said that no fill can be placed in FLOODWAY if it would <br /> cause a rise in the water surface of a 100 -year flood. The <br /> low -flow design may cause such a rise in the water surface; <br /> most likely this would need to be analyzed using the HEC 2 <br /> computer model, and include a request for approval from FEMA. <br /> This process may take awhile and may not result in FEMA <br /> approval. <br /> 5. In addition to doing the HEC 2 modeling, it would be <br /> appropriate to remodel the upper A -2 on " Storm Plus ", the <br /> model used by OTAK in their 1990 Drainage Master Plan. <br /> 6. Inasmuch as there probably will be some revision of <br /> your design, you may want to hold or revise your joint <br /> application to DSUCorps. <br /> 7. The design needs to be engineered and stamped by a <br /> Civil Engineer. The obvious options are 1)the privately <br /> engineered public improvement process, and 2)design by our <br /> Page 1 <br />