DR8601-CS 860620
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ESPEY,
HUSTON &
ASSOCIATES, INC.
Engineering & Environmental Consultants
June 20, 1986
Mr. Ed Powell, P .E.
Coppell City Engineer
City of Coppell
P.O. Box 478
Coppell, Texas 75011
EH&A Job
No. 8237-30
Dear Mr. Powell:
As we discussed by telephone on June 18, 1986, we are responding to the
letter from General Homes dated June 16, 1986.
We will address each item as they appear in the General Homes letter
da ted June 16, 1986 as follows:
1) Our intent was to show that erosion began at the downstream
outfall of the channel and then this erosion migrated upstream due
to excessive velocities. The concrete lined channel (0.10% slope)
upstream of the failure has not experienced erosion. In our report
conclusions, Item I, we indicated what the lined and the unlined
channel velocities would be for a particular depth. This was
primarily due to that there were not any available recorded flows
for this channel.
2) In our conclusions Item 2 we stated that the excavation
downstream did contribute to the likelyhood of erosion but from
our interviews, previous correspondence and construction plans we
were able to review we were unable to determine what impact it
had on the erosion and failure of the channel.
There is one item that we were unable to resolve during our review that
may have some impact on this issue. This item is on the construction plans
submitted by General Homes. They had labeled the unlined channel as temporary
which would lead one to believe someone had some permanent channel and/or drop
structure for future construction. But from all our conversations, we were unable to
find what was intented to be constructed.
It is our professional opinion that erosion and the ultimate failure of the
lined channel was due to excessive velocities which our previous report dated May
20, 1986 had stated.
333 West Campbell Road, Suite 400, 4th Floor' Richardson, Texas 75080 . (214) 669-9600
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JPEY, HUSTON & ASSOCIATES, INC
Mr. Powell
June 20, 1986
Page 2 of 2
We are availabe at your convenience to discuss our conclusions with you.
If we can be of any further assistance please let me know.
Sincerely,
2J;d tik,e::?
Bob Whaling
B W :cb
Enclosures
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II
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II PROJECT: CITy OF CO~~LL
! I PROJ NO: 8237
II CHANNEL: DRAINAGE CHANNEL
II REACH: CHNL WID PILOT
II ENGINEER: BW
II CK BY:
II DATE: 5/18/86
II
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I i TO VIEW CROSS-SECTION
II PRESS F9 THEN TYPE GP .
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THIS SPREADSHEET CAN I PLEASE DEFINE THE FOLLOWING ! SOLUTION: AREA
DETERMINE THE CAPACITY I PP"AMETERS: I PERIMETER
[f Po TRAPEZOIDAL CHANNEL I I HYD RAD
WITH (OR WITHOUT) A I MAIN CHANNEL: I
TRAPEZOIDAL PILOT CHANNEL. I BOTTOM WIDTH........... 15.0 !
I DEPTH................. 1.0
I ROUGHNESS COEFFICIENT.. 0.045
SLOPE OF EMBANKMENT.... 4.00 :11
INVERT SLOPE........... 0.03050
...-----H.-MAUf -- ...
19.00
23.25
0.82
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II
II
II
II
II
DATA FOR HEC2 GR CARDS
AND EARTHWORK TEMPLATE
FOR THIS CROSS-SECTION
CAN BE FOUND BELOW.
I BOTTOM WIDTH...........
I DEPTH. . . . . . . . . . . . . . . . . .
I ROUGHNESS C~cFFICIENT..
I SLOPE OF EMBANKMENT....
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95.95 II
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ERR II
31.00 II
0.00 II
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WARNING! !... THIS SOLUTION SHOULD NOT &E I I
USED TO ;~EPlACE PROPtR BACKWATER COMPUTATIONS II
II
II
CAPACI1Y =
MAIN CHANNEL VELOCITY =
PILOT CHANNEL VELOCITY =
TOP WIDTH MAIN CHANNEL =
TOP WIDTH PILOT CHANNEL =
I PILOT CHANNEL: (ALL 0'5 NO PILOT)
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II
II PROJECT: CITY OF COPPELL
II PROJ NO: 82:~
II CHANNEL: DRAINAGE CHANNEL
i: REACH: CHNL 101/0 PILOT
i I ENGINEER: BW
II CK BY:
II DATE: 6/18/86
II
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II
II
II
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II
II
I I
-----MAnr-------plcor-11
46.00 0.00 II
31.49 f! ~0 'I
t. 46 ERR II
II
II
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342.07 II
7.44 II
ERR II
39.00 II
0.00 Ii
II
WARNING' !... THIS SOLUTION SHOULD NOT BE II
USED TO REPLACE PROPER BACKWATER COMPUTATIONS i I
Ii
II
HYDRAULICS
WORKSHEET
1 :
TO VIEW CROSS-SECTION
PRESS F9 THEN TYPE GP .
CAPACITY =
MAIN CHANNEL VELOCITY =
PILOT CHANNEL VELOCITY =
TOP WIDTH MAIN CHANNEL =
TOP WIDTH PILOT CHANNEL =
II
Ii
Ii
II
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DATA FOR HEC2 GR CARDS
AND EARTHWORK IHI~LATE
FOR THIS CROSS-SECTION
CAN BE FOUND BELOW.
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Il PROJECT: CITY OF COf~~LL
II PROJ NO: 8237
II CHANNEL: DRAINAGE CHANNEL
II REACH: CHNl WID PILOT
II ENGINEER: BW
II CK BY:
II DATE: 6/18/86
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I I THIS SPREADSHEET CAN I PLEASE DEFINE THE FOLLOWING I SOLUTION: AREA
II
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81. 00 0.00 II
HYDRAULICS
WORKSHEET
II ....-..-- ----'----'-----.----"-'-- .- - -----.-...----.-..-----------------...----.------------ .-.------ -- --------------.-----------------.. .----.-.----11
II PROJECT: CITY OF COPPELL Ii
II PROJ NO: 8237 Ii
! I CHANNEL: DRAINAGE CHANNEL i !
II REACH: CHNL WID PILOT II
I i ENGINEER: BW
! I CK BY:
I I DATE: 6i18/8&
HYDRAULICS
WORKSHEET
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I I WITH (OR WITHOUT) A I MAIN CHANNEL:
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II PRESS F:3 mEN TYPE GP . I ~ OF EMBANKMENT.... 4.00 :11 MAIN Cli\NNEL VELOCITY = '3.29 t I
- j I I .RT SLOPE........... 0.03060 I PILOT ~EL VELOCITY = ERR II
II DATAFORHEC26RCARDS I I TOPWh. I'IAINCHANNEL= 47.0011
II AND EARTli/ORK TEMPLATE I PILOT CHANNEL: (ALL 0' 5 NO PILon I TOP WIDTH PILOT CIIlNNEL = 0.00 II
II FOR THIS CROSS-SECTION I BOTTOM WIDTH........... 0.0 I II
II CIV'l BE FOUND BELOW. I DEPTH....... ........... 0.8 I WARNING' !... THIS SOlUTION SHOUlD NOT BE II
II t ROUGHNESS COEFFICIENT.. 0.000 I USED TO REPLOCE PROPER BACKWATER COMPUTATIONS II
II I SLOPE OF EMBANKMENT.... 0. 00 : 11 II
I 1____.___________________________1____________________________________1__________________________________________________1 I
11----------------------------------------------.--------------------------------------------------.--------------.--------11
II PROJECT: CITY OF ClPPELL II
II PROJ NO: 8237 HYDRfiJlICS II
II CHIlNNEL: DRAINAGE CHANNEL II
II REACH: CHNL WIO PILOT WORKSHEET II
II ENGINEER: BW II
II CK BY: II
II DATE: 6/18/86 II
II II
I I-------------------------------T------------------------------------T---------------------------------MAIA-------PICOT-II
II THIS SPREADSHEET CIV'l I PLEASE DEFIlE THE FIl.LOWING I SIl.UTION: AREA 124.00 8.00 1\
II DETERMItE TIE CAPACITY I PARAMETERS: I PERIMETER 47.98 0.00 1\
II OF A TRAPEZOIDAl. CHANNEl I I HYD RAn 2.58 ERR II
II WITH <OR WITHlllJn A I MAIN CHANNEL: I II
II TRAPEZOIDAl. PILOT CHANNEL. I BOTTOM WIDTH........... 15. 0 I 1\
1\ I DEPTH ................. 4.8 I 1\
II TO VIEW CROSS-SECTION I ROl.Il3IfESS COEFFICIENT.. 0.Il4S I CAPACITY = lM3.78 II
1\ PRESS F9 TIEN TYPE 6P . I SLOPE OF E~MENT.... 4.00 : 11 MAIN CHIlNNEL VELOCITY = II. 88 II
II I INllERT SlOPE........... 0.0386i'l I PILOT CHANNEl VELOCITY = ERR II
II DATA FOR IiEC2 6R CARDS I I TOP WIDTH MAIN CHANNEL = 55.00 II
II AND EARTHWORK TEMPLATE I PILOT CIiAN'El.: (ALL 0'5 NO PILon I TOP WIDTH PILOT CHAItEL = 0.00 II
II FOR THIS CROSS-SECTION I BOTTOM WIDTH........... 0.0 I II
II CAN BE F~D BELOW. I DEPTH. .. . .. .. . .. .. . .. .. 0.0 I WARNING! ! .. . THIS SOlUTION SHW..D NOT BE II
II I IllIII6MSS COEFFICIENT.. 0.000 I USED TO REPLACE PROPER BACKWATER COMPUTATIONS II
II I SlOPE OF EMBANKMENT.... 0. 00 : 11 II
11_--____------------------______1______-----------------_____________,__________________________________________________11
1'-------------------------------------.-..-----..--..-------------------------------------------------------------------.----11
II PROJECT: CITY OF CIJlPELL II
II PROJ NO: 8237 HYDRAlLICS II
I' CHANNEL: DRAINAGE CHANtEL II
II REACH: CHNL WIO PILOT WORKSHEET II
II ENGINEER: BW II
II CK BY: II
II DATE: 6/18/86 II
II II
I ,-------------------------------T------------------------------------T---------------------------------MAIR-------PICOT-II
I' THIS SPREADSHEET CAN I PLEASE DEFINE THE FIl.LOWING I SIl.UTION: AREA 17S.0i'l 0.00 II
II DETEflItIINE THE CAPACITY I PARAMETERS: I PERIMETER 56.23 0.00 II
II OF A TRAPEZOIDRL CHANNEL I I HYD RAn 3. 11 ERR II
-
II II
I' PROJECT: CITY OF ClPPELL II
II PROJ NO: 8237 HYDRAULICS II
II CHANNEL: DRAINAGE CHANNEL II
II REOCH: CHNL 14/0 PILOT l()RKSHEET II
II ENGINEER: 8W II
II CK BY: II
II DATE: 6/18/86 II
II II
11---gITR-10R-QITROOTi-A---------T-~IA-~:----------------------T-------------------------------------------------- ,
II TRAPEZOIDAL PILOT cmNNEL. I BOTTOM WIDTH........... IS. 0 I I
II I DEPTH ................. 5.1 I I
II TO VIEW CROSS-SECTION I RIlIJIHESS COEFFICIENT.. 0.1l45 I CAPACITY = 2154.67 I
II PRESS F9 THEN TYPE GP . 'SLrPE OF EllBAN<lENT.... 4.. :11 MAIN CHANNEL VELOCITY = 12.31 I
II I INVERT SLOPE........... 0.0386i'l I PILOT Cl-tlH€L VELOCITY = ERR I
II DATA FOR HEC2 6R CARDS , I TOP WIDTH MAIN ClRtEL = 63.00 I
II AND EARTHWORK TEMPLATE I PILOT CHANNEL: (ALL 0' 5 NO PILon I TOP WIDTH PILOT CIIlNNEL = 0.00 I
II FOR THIS CROSS-SECTION I BOTTOM WIDTH........... 0.0 I I
II CAN BE FOUNIJ BELOW. I DEPTH.. .. .. .. .. . .. . .. .. 0.0 I WARNING! !.. . THIS SIl.UTION SIIlUlD NOT BE I
II I IlllIJ6H'ESS COEFFICIENT.. 0.000 I USED TO REPI..OCE PROPER BACKWATER COi'lPUTATIONS I
II I SLOPE OF EMIlANKIf:NT.... 0. 00 : 11 I
11________________________________1____________________________________,__________________________________________________ I
1-----------------------------------------------------------------------------------------------------------------------11
I PROJECT: CITY OF COPPELL II
I PROJ NO: 8237 HYDRAlLICS II
I CHAtfEL: DRAINAGE CHANNEL II
I REACH: CHNL WIO PILOT WORKSl-EET II
I ENGINEER: 8W II
I CK BY: II
I DATE: 6/18/86 II
I 1\
I-------------------------------r-------.----------------------------r---------------.---------------MAIR------"llI[ilT-11
I THIS SPREADSHEET CAN I PLEASE DEFINE THE FOLLOWING I SIl.UTION: AREA 234.00 0.00 1\
I DETERMINE THE CAPACITY I PARAMETERS: PERIMETER 64.48 0.00 II
or- n. TnlV".d:'".1innl\l ('\fllU...lr"'l uvn onn '2 c.l: J:DD II
. ,
WITH ([IfI WITHuUT) Ii
TRAPEZOIDAL PILOT CHANNEL.
TO VIEW CROSS-SECTION
PRESS F9 THEN TYPE GP .
DATA FOR HEC2 GR CARDS
AND EARTHWORK TEMPLATE
FOR THIS CROSS-SECTION
CAN BE FOUND BELOW.
6.0
..~.JGHNESS COEFFICIENT.. 0.045 I
SLOPE OF EMBANKMENT.... 4.00 :11
INVERT SLOPE........... 0.03060 I
I
OILOT CHANNEL: (A~L 0'5 NO PILOT) I
I
~iAIN C>tANNtL:
~TTOM WIDTH...........
TH ....""..."""" 'I".
BOTTOM WIDTH...........
DEPTH. . . . . . . . . . . . . . . . . .
I ROUGHNESS COEFFICIENT..
I SLOPE OF EMBANKMENT....
I
15rlll
0.0
0.0
0.000 !
0.00 :11
j
I:
) I
II
3191. 92 II
13.6'1 II
ERR II
71. 00 II
0.00 II
! I
WARNING I !... THIS SOLUTION SHOULD NOT BE II
USED TO REPLACE PROPER BACKWATER COMPUTATIONS II
1/
II
~,
CAPAC ITY =
MAIN CHANNEL VELOCITY =
PILOT CHANNEL VELOCITY =
TOP WIDTH MAIN CHANNEL =
TOP WIDTH PILOT CHANNEL =
_~_.~__ __.. ._w~~._._. ___. ._______ __ __________ -__.___ ___ -. --------, -- -------- ------.-.--- ---------... .--,.- -----.-. ----. ...... ---".", -.-.------ --.-.-... -----~~-,,--_. -,-
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