St Joseph-CS020517~~~~~
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May 17, 2002 ~~
Mr. Kenneth M. Griffin, P.E.
Director of Engineering
City of Coppell
255 Parkway
Coppell TX 75019
Re: Woodbridge Channel Water Surface Elevations
St. Joseph Village
Coppell, Texas
Aguirre Proj. No. 1030009900, Task 0400
Dear Mr. Griffin,
Senders direct dial 972-789-2695
Senders Fax 972-788-1583
m m i l l i ca n@ ag u i rre. com
We are presently completing our hydraulic calculations for the St. Joseph Village storm
sewer systems that discharge into Woodbridge Channel along the south side of Sandy
Lake Road. A review of available data regarding water surface elevations in the channel
reveals the following:
1. From the 1981 construction plans for Woodbridge Channel:
• In Denton Creek downstream of existing MBC under Sandy Lake Road
25-yr Water Surface = 443.50
50-yr Water Surface = 444.00
• In Woodbridge Channel upstream of existing MBC under Sandy Lake Road
25-yr Water Surface = 443.75
50-yr Water Surface = 444.33
• In Woodbridge Channel at upstream of St. Joseph site
25-yr Water Surface = 444.71
50-yr Water Surface = 445.37
2. From the 2002 proposed costruction plans for Sandy Lake Road:
• In Denton Creek downstream of existing MBC under Sandy Lake Road
25-yr Water Surface = 443.82
50-yr Water Surface = No Data
• In Woodbridge Channel upstream of existing MBC under Sandy Lake Road
25-yr Water Surface = 443.78
50-yr Water Surface = No Data
• In Woodbridge Channel at upstream of St. Joseph site
25-yr Water Surface = 444.44
50-yr Water Surface = No Data
3. From the August 2001 FEMA FIRM for this area, a 100-yr water surface elevation of
445 in the Elm Fork of the Trinity River which water surface is presumed to extend into
Denton Creek at the downstream side of the existing MBC under Sandy Lake Road.
No water surface elevations are shown on the FIRM for Woodbridge Channel.
AGUIRRE CORPORATION
12700 PARK CENTRAL DR FLOOR 15
DALLAS TEXAS 75251
FAX 972 788 1583
PHONE 972 788 1508
THE CAN-00 SPIRIT THAI GETS THE J06 OONE®
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Mr. Wonderful Client
January 27, 1997
Page 2 of 2
tlVl1l4\6 SCL..TION59~NGE 19EC
We respectfully submit that it is unlikely that a 100-yr rainfall event would occur on the St.
Joseph site at the same time as a 100-yr flood was occurring on the Elm Fork; and thus, it
is overly conservative to adopt a water surface of 445+ in Woodbridge Channel as a
beginning elevation for on-site storm sewer calculations. We also note that the Sandy
Lake Road plans, as prepared for Dallas County, adopted a 25-yr water surface in the
channel as a starting point for its calculations. Therefore, we request that we be allowed to
utilize for our calculations the same hydraulic conditions as the County plans for Sandy
Lake Road. If you would like to visit with us regarding this issue, please call.
Respectfully,
AGUIRREcorporation
Ot,/,~ ,
CG~t,Q~~S UI~L~i1'-4,
J. Michael Millican, PE
Dir. Civil Engineering
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For more information on AGUIRREcorporation visit our web site at www.aguirre.com
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