Jayson Teno
Hello All,
The UDFCD Manual Volume 2 Section 3.2.4 for Simplified Full Spectrum Detention Sizing (EURV Flow Control) states that the formula in figure SO-13a (eq13a) should be used to determine the area per row Ao, of the perforated plate and one should seek a drill bit size that will deliver an area within +5% and -10% of this area. Given this, can anyone explain the formulas used to determine of the recommended outlet area per row ( Ao ) for an EURV outlet structure as calculated by the UD Detention excel workbook (WQCV worksheet) for an EURV 72 hr release, and the UD-BMP V3.01 excel workbook (EDB worksheet) for an EURV method.
I have received different resulting values for Ao for the same input parameters between the two workbooks.
Also, I noticed that the Micropool and Outlet Structure (part 7) of the UD-BMP workbook EDB worksheet is somehow tied to the trickle channel section (part 6)
Any information would be greatly appreciated.
Jayson Teno
David E. Archer & Associates Inc.
105 Wilcox St.
Castle Rock, CO 80104
P: 303-688-4642
F: 303-688-4675
Ken MacKenzie
Jayson, welcome to the forum.
Please go to http://www.udfcd.org/downloads/down_sw_bmp.htm and read the pdf titled “UDFCD orifice sizing memorandum”.
The UD-BMP workbook is correct, but the UD-Detention workbook has not been updated yet. Also the Storage chapter in Volume 2 of the USDCM is undergoing an update now - the new version will have the correct equation but the current one does not.
The new equation should get you much closer to the desired drain time than either of the two previous equations did, but I still recommend a reservoir routing when possible to fine-tune the orifice sizing.
-Ken
Ken A. MacKenzie, P.E., CFM
Manager, Master Planning Program
Urban Drainage and Flood Control District
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Jayson Teno
Holly Piza
The technical memorandum that Ken referenced in his response details the new equation pretty well and within this memo you will find how the trickle channel slope relates to the outlet structure. The equation is based on a number of assumptions regarding basin geometry because the specific stage discharge for any basin will vary affecting the time it takes for that basin to drain. The new equation is improved in this way, using the trickle channel slope to help define the shape of the basin in an effort to get a more accurate orifice size for the specified drain time.
Holly Piza, PE
Senior Project Engineer
Master Planning Program
Urban Drainage and Flood Control District
From: udfcd-...@googlegroups.com [mailto:udfcd-...@googlegroups.com] On Behalf Of Jayson Teno
Sent: Tuesday, October 18, 2011 12:40 PM
To: udfcd-...@googlegroups.com
Subject: [UDFCD-support]
Hello All,
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