Reserve-CS000111 9729319538
· tm Kent Collins Frmm Daniel Heischman
Fag~ 972-304-3570 l~agem 10
Phmtm g72-304-3681 Oatm 01111/00
Rm ~ I~ Bill Anderson
Junclion Box John Papagoios
n Uegent [] For Review [] Please 4:~, ,mo.d. [] Plmlam ReIMy [] Please
· ~: The following sheets show the methods and the calculations used
in designing the proposed junction box along Bethel Road for the Resewe
Subdivision. Please feel free to contact me if you have any comments and/or
questions.
AREA AREA C TC I100QIO0 COMMENTS
t~ (Ac.) (min.) (in)hr) (cfs) .
1 1.3 0.55 10 8.88 6.5 10' CURB INLET
2 1.2 0.55 10 8.88 5.9 4'X4' "Y"INLET
5 2.5 0.55 10 8.88 11.2 14'CURB INLET
4 I0.8 0.55 10 8.88 5.9 10'CURB INLET
5 I~.~ I 0.55 ! 10 I 8.8s 1'6.~I10' CURB INLET
RAINFALL INTENSITIES FROM HYDRO-55
~ · AREA (AC.)
GlO0 (c.f.s.)
Or.,..I -- 33.'70
. 'i .~' "l ~'~ ~ '
~ ...........
'~' ~"'.-"-' -:~--'.-
--- ~ ~.-" . .,,~..~ ~
............. ~ ~".-~...-'-: ;~-~;.;~
'~.-'~' -~. -". '.-' -" ~"..' m
...
~ ........ ' .-' :".-' ~' .~. .- . '1
.....'. ~.-. . .....d ....... ~.,._,,'.-, ~. ., ,~
.'
01/11/00 TUE 14:24 FAX 9729319538 DOWDEY ANDERSON ASSOC ~008
GIVEN: Existln~ Conditions
C~s -- 0.38
I~oo = 8.88 iz~hr
A = 5.63 Ac.
Qi00= 19.00 els
Outflow Structure - (2) 21" RCP's - FL 489.20
Provosed Conditions
C = 0.55
I ~00 = 8.88 in/hr
A=6.9Ac.
Q,00 = 33.70 cfs
Design Sunction Box so flow out of the 2-21" RCP's equ__s_!s existing conditions. Additional flow
will go to bar ditch via opening in junction box.
For Q = 19 els (out of culverts), headwater depth = 21"
(HW/D = ---1 - see homograph)
Flow into ditch - Q~00 = 14.7 cfs
Using Weir formula, design size of junction box opening
Weir formula, Q = 3.087 LH 3/2 => Q = 14.7
For L = 5', H = 1' (0.97 rounded)
Q = 3.087 LH 3/2
14.7 cfs = 3.087 (5') 3/2
H 3/2 -- 14.7/(3.087) (5)
H = 0.97'
Comments:
By taking the area that flows into the culverts prior to development, I calculated a Q~0o of 19.00
els. The proposed conditions would have 33.70 els flowing through the (2) 21" culverts. The
junction box is designed to produce a head that will allow only 19.0 els through the culverts with
the _r~rnalnlng flOW exiting the junction box through an opening on the east side. This remaining
flow will travel down the bar ditch and into the creek.
01/11/00 TUE 14:25 FAX 9729319538 DOWDEY ANDERSON ASSOC ~009
The headwater depth was determined usin~ the ettsche~ homograph (taken f~m TxDOT Bridge
Division Hydraulic Manual). Given a diameter of 21" and a flow of 9.5 cfs (per pipe), a HW/D
ratio of 1.0 was determined. Thus, a head of 1.75' (2I") is needed to allow 9.~ cfs throush each
culvert.
Then using the Weir formula, the size of the openin~ needed to keep the waterhead depth at
1.75' and allow the remslnlng 14.7 cfs to exit the junction box was determined. ThrouF, h trial
and error, a 5' x I' opening is needed. And so, the junction box is designed nccordin__F, ly.
01/11/00 TUE 14:25 FAX 9729319538 DOWDE¥ ANDERSON ASSOC ~010
f~ - 18o - io~ooo
~- III - I,ooo EXAMPLE ( I ) (2) (3)
- 6,~ ..... ' ~ ·
-I~ ~ · -- '
- -- 4,~ ~t flW -- 8. . -- S.. ..
- IB~ - ~ fm '
~ ~ B~ O] LS i.8 ~ ~' ~ ' .-- 4..
_,. , -
-- -60 o~i~ / m~15
' ~ ffi 7 SO HW ENTRANGE ~ -
o _ 40 ~ SGALE TYPE ~-- i.o -
~ ~ e,~. M - .o
~ / ~, b,b.,t.,, ,..NS, (,), t~,,
..... / fie llrdgk, inollned fin
/ ~ 4 D Nd O ,eileo, w reverse se -- .6 -- .6
¢
~ ~ ilJ~tr~tod.
-- 15
-- .5 -- .5
' ~ ~.0 -- .5
-,a HEADWATER DEPTH FOR
GONGRETE PIPE GULVERTS
( FHWA WITH INLET CONTROL
~ I
BRIDGE DIVISION HYDRAULIC MANUAL 12