HomeMy WebLinkAbout82 Development 436 Britt Rice - Lake, Dam, SpillwayDEVELOPMENT PERMIT
PERMIT NO. 436
BRITT RICE SPILLWAY
FOR AREAS INSIDE THE SPECIAL FLOOD HAZARD AREA
RE : CHAPTER 13 OF THE COLLEGE STATION CITY CODE
SITE LEGAL DESCRIPTION:
Thomas Caruthers League, A-9
SITE ADDRESS:
Not Addressed
OWNER:
Britt Rice
Britt Rice Electric
3 002 - D Longmire
College Station, Texas 77845
DRAINAGE BASIN:
Foxfire Tributary
TYPE OF DEVELOPMENT:
This permit is valid ONLY for the construction of the spillway as shown in the Britt
Rice Lake, Dam and Spillway Report by Garrett Engineering dated October 28,
1996. Contractor shall notify the City at 764-3570 at least 24 hours prior to
construction. Contractor shall prevent silt and debris from leaving the site in accordance
with the City of College Station Drainage Policy and Design Criteria. Owner and/or
contractor shall be responsible for any damage to existing city streets or infrastructure due
to heavy machinery and/or equipment.
In accordance with Chapter 13 of the Code of Ordinances of the City of College Station,
measures shall be taken to insure that debris from construction, erosion, and sedimentation
shall not be deposited in city streets, or existing drainage facilities .
I hereby grant this permit for development of an area inside the special flood hazard area.
All development shall be in accordance with the plans and specifications submitted to and
approved by the City Engineer in the development permit application for the above named
pr ~ect and all of the codes and ordinances of the City of College Station that apply .
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Date
Contractor Date
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Spillways
SIDE CHANNEL
TR O UGH ----
CHUTE
ST I LL I NG BASIN
363
.·
Figure 238. Typical side channel and chute spillway arrangement. 288-0-2900.
control will shift from weir flow over the crest
to tube flow in the transition and then to full
pipe flow in the downstream portion. Full
pipe flow design for spillways except those with
extremely low drops is not recommended, as is
discussed in section 212 (e).
A drop inlet spillway can be used advanta-
geously at dam sites in narrow canyons where
the abutments rise steeply or where a diver-
sion tunnel or conduit is available for use as
the downstream leg. Another advantage of
this type of spillway is that near maximum
capacity is attained at relatively low heads;
this characteristic makes the spillway ideal for
use where the maximum spillway outflow is to
be limited. This characteristic also may be
considered disadvantageous, in that there is
little increase in capacity beyond the designed
heads, should a flood larger than the selected
inflow design flood occur. This would not be
a disadvantage if this type of spillway were
used as a service spillway in conjunction with
an auxiliary or emergency spillway.
An artist's conception of a drop inlet spill-
way used with a small earthfill dam is shown in
figure 240. Figure 241 shows such a conduit
under construction. The hydraulic design is
discussed in section 212. Additional informa-
tion on the design and performance of drop
inlet spillways is given in the references listed
in the bibliography [5, 6, 23].
(h) Baffle Apron Drop Spillways.-Baffled
364
Figure 239 . Chute spillway far Scofield Dam in Utah . 288-0-2901.
aprons or chutes are used in flow ways where
water is to be lowered from one level to another
and where it is desirable to avoid a stilling
DESIGN OF SMALL DAMS
basin. The baffle piers partially obstruct the
flow, dissipating energy as the water flow s
down the chute so that the flow velocities en-
tering the downstream channel are relatively
low. Advantages of baffled aprons include
economy, low terminal velocity of the flows re-
gardless of the height of the drop, down-
stream degradation does not affect the spillway
operation, and there are no requirements for
initial tailwater depth in order for the stilling
action to be effective.
The chute is normally constructed on a slop e.
of 2 :1 or flatter, extending below the outlet
channel floor. Chutes having slopes steeper
than 2 :1 should be model tested [11] and
their structural stability checked. The lower
end of the chute should be constructed far
enough below the channel floor to prevent dam-
figure 240. Drap inlet spillway for a small dam. 288-0-2902.
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Spillways 365
Figure 241 . Conduit ond stilling bosin for combined drop inlet spillway and outlet works at Heart Butte Dom during construction . Heart
Butte Dom is on the Heart River in North Dakota. 288-D-2903.
age from degradation or scour.
Design capacities of baffled aprons have var-
ied from less than 10 second-feet to over 80
second-feet per foot of width. At Conconully
Dam, the spillway baffled apron scale model
was designed to represent prototype discharge
up to 78 second-feet per foot of width and to
operate effectively at 150 second-feet per foot
of width. The completed spillway for Con-
conully Dam is shown in figure 242. The
generalized design procedures discussed in this
section were obtained from test · results on sev-
eral models of baffled chutes conducted at the
Bureau of Reclamation [11].
The typical hydraulic design procedure for a
baffle apron drop spillway is given in the num-
bered steps following and refers to figures 243
and 244:
366
Figure 242. Baffled apran drap spillway used at Cancanully Dam in
Washington . The flaw shawn pauing aver the spillway is abaul
• 50 ch. P21-1-41 -178NA.
(1) Determine the maximum expected dis-
charge, Q.
(2) Determine unit design discharge
q=Q/W, where W is the chute width.
The chute width may depend on the up-
stream channel width, the downstream
channel width, economy, topography,
and frequency of discharge, as well as
\ maximum discharge.
(3) Entrance velocity, V, should be as low
as practical. Ideal conditions exist
when V1=m-5, curve D, figure 244,
for discharges up to 69 second-feet per
foot of width. Velocities near critical,
V c=ffl, curve C, figure 244, or above
cause the flow to be thrown into
the air after striking the first baffle
pier. High velocities may cause the
flow to pass completely over the next
row or two of baffle piers. It is very
important that proper flow conditions
be provided at the entrance to the baf-
fle apron because satisfactory perform-
DESIGN OF SMALL DAMS
ance of the entire structure may
hinge on proper entrance . flow
conditions.
( 4) A vertical offset between the approach
channel floor and the chute i11 used to
form a desirable uniform entrance ve-
locity, V i, and will vary in individual
installations. A short radius curve pro-
vides a crest on the sloping chute. The
first row of baffle piers should be placed
no more than 12 inches in elevation be-
low the crest. Alternate rows should be
staggered to provide a baffle pier below
each space and a space below each baffle
pier.
( 5) The baffle pier height, H, should be
about 0.8 D e or 0.9 D e, where the critical
depth (D e ) for the rectangular chute is
given by the formula D 0 =ff/Y and is
shown by curve A of figure 244. Baffle
pier height is not a critical dimension
but should not be less than recommended.
(6) Baffle pier widths and spaces should be
equal, preferably about one and one-half
H, but not less than H. Other baffle
pier dimensions are not critical hydrau-
lically. Suggested cross sectional di-
mensions are given.
(7) Row spacing of baffle piers along the
chute slope should be H divided by the
s_lope, where the slope is given in deci-
mal form. A 2 :1 slope, 0.50 in decimal
form, makes the row spacing equal to
2H parallel to the chute floor.
( 8) The baffle piez:s are usually constructed
with the upstream face normal to the
chute floor surface; however, piers with
vertical faces may be used . Vertical
face piers tend to produce more splash
and less bed scour, but the differences
are minor.
(9) Four rows of baffle piers are needed to
establish full control of the flow, al -
though fewer rows have operated suc-
cessfully. As many additional rows as
required beyond the fourth maintain
the control established upstream. At
least one row of baffles should be buried
below the outlet channel grade to pro-
tect against scour. Additional rows of
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Spillways 367
(10)
Figure 243 . Basic proportions of o boffled chute spillwoy. 288-0-2807.
baffles should be buried as needed to
protect against degradation.
The chute training walls should be
three times as high as the baffle piers
measured normal to the floor. This
wall height will contain the main flow
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and most of the splash. It is not neces-
sary or practical to build the walls high
enough to contain all the splash.
(11) Riprap should be placed at the down-
stream ends of the training walls to pre-
vent erosion of the banks.
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10
Recommended Entronce Velocit-i D
ilic.::...-'-~-'---~~--'-~~~~.L.-~~~-'-~~~--'~~~~..._~~~-'O
10 20 30 40 50 60
DISCHARGE IN CFS PER FOOT OF W IDTH : q
Figure 244 . Recommended boffle pier heights ond ollowable veloc ities for baffled chute
spillways. 288-0-2806 •
70
Britt Rice
Lake, Dam, and Spillway
Thomas Caruthers League, A - 9
College Station, Brazos County, Texas
Prepared for:
Britt Rice
Britt Rice Electric
3002 -D Longmir
College Station, TX 7 84
(409) 693 -40'0
~
2 GARRETT ENGINEERING
c:aem1L aG I iUiG a LAllll IURVIWIG • •
.... CM1&~..-Y. . t•·mYAll. lECAS 11la •(.., ..._. •• ..,..._...
* October, 1996 *
""
-
Britt Rice
Lake, Dam, and Spillway
Thomas Caruthers League, A -9
College Station, Brazos County, Texas
Prepared for:
Britt Rice
Britt Rice Electric
3002 -D Longmire
College Station, TX 77845
(409) 693 -4076
Prepared By:
~
2 GARRETT ENGINEERING
COlllUl TllO llKI WWW & l.Alll IURVIVlllG '
.... CAllllll~NMWAY. surn••·mtYAll. TEXAS nm.,.., ....... .., .......
* October, l 99t'> *
The project site is located on a 61.08 acre tract, on the northwest side of Bird
Pond Road. The lake, which is in the east corner of the property, collects run-
off from approximately 21.14 acres.
The flow from the drainage basin (in cubic feet per second (cfs)) was determined
to be 86.12 cfs for the 100-year storm. This was determined from the Rational
Method as follows:
where:
Q=C*i*A
Q = flow in cfs
i =intensity in in./hr.
A = area in acres
C = runoff coefficient
= 11.64 in./hr. for 100-yr. storm
= 21.14 acres
= 0.35 (value for unimproved land)
9100 = 0.35 * 11.64 * 21.14 = 86.12 cfs
According to Manning Pipe Theory, an 5' line graded at 0 .54% can carry 190.80
cfs .
where:
Q = (1.49 / n) *A* R2/3 * s o.s
Q = flow in cubic feet per second (cf!')
n =Manning's roughness coefficient
n = 0.013 for reinforced concrete pipe
A = area of pipe in square feet
A= nd2 /4
A= 1t * (5)2 I 4 = 19.63
R = hydraulic radius = A I P
where:
A = area of pipe in square feet
P = wetted perimeter = 7t * diameter
p = 1t * 5 = 15. 71
R = 19.63 I 15.71 = 1.25
S =slope of pipe= 0 .0054
Q = (1.49 I o.013) * 19.63 * I.25213 * o.0054o.s
Q = 190.80 cfs
Since the ratio of loading to capacity is 86.12/ 190.80 = 0.45, the resulting
velocity (from design tables) will be 0.975 of full flow velocity. Full flow velocity
is calculated as follows:
Where:
V =QI A
full
v full = full flow velocity
Q = full flow capacity in cfs = 190.80 cfs
A= area of pipe in square feet= 19.63 ft2
Vru11 = 190.80 I 19.63 = 9. 72 ft/ sec
The resulting velocity for a pipe flowing at 0.45 full, being 0.975 of full flow
velocity, is thus:
v0.45full = 0.975 * 9. 72 ft/sec= 9.48 ft/sec
In this case, it is unlikely that pressure flow will occur in the 5' diameter
concrete pipe. However, a small baffled apron drop spillway should be used to
slow the resulting velocity to help prevent erosion and scouring. Four rows of
baffle piers are suggested to establish full control of the flow (see Figure 1).
Each baffle pier is 2' wide, 1.25' high, with a top length of 9", and a base length
of l' (see Figure 3). The baffle piers along each row will be placed 2' apart, and
the following row will be staggered at a distance of 2.5' (see Figure 1). Each
baffle will be reinforced with #4 stirrups, placed 4" from the ends, at 8" apart
(see Figure 3). These stirrups will be tied to the #4 bars that will be placed in
the concrete reinforced pad. This concrete reinforced pad will begin at the end
of the 5' reinforced concrete pipe, and extend 13.5' downstream to serve as the
apron for the spillway. The width of this pad will vary because it will be placed
between two existing concrete headwalls (see Figure 5). The apron will be 4"
thick, reinforced with #4 bars and will have an 18" toewall across the
downstream end (see Figure 4). Approximately 120 square feet ofT.C.S. #018
rock rubble rip-rap will also be placed at the downstream side of the concrete
apron to prevent erosion beyond the concrete apron.
REFERENCE
Desi~n of Small Dams. Prepared by the United States Department of the
Interior-Bureau of Reclamation. Water Resources Technical Publication: 1977.
-&£tffRA1-Noits: 1.) :ro1ttr 8£1WWJ ~1s-m1 Go ffiNCRf'tt; µ(f.tDWALJ., At-ro PRCi CONC/<.tr£ APPm WILL£,{ :£Ate Wmt A tr'f JCAL .foL~/Jf?!1'H!Nf stAL (5f!l t>b"All..) 11#<01J911DIJT 1-r5 f:tt1'Jl<t UN4-rH. z.)Al.()N~ EArn r«Y+J, 11-( 8AFftE PrtR5 ARE 2' Wll>£ AND Pl.AC@ 2' APART. f)J~ N cr a1JC-l('t1! 1-\(Jl)'i'JA.U.. £.XISflN~ 5' RclNFoPLEl> C6NCRti'£' l'IPC FIGURE 1. BAfflfl> AfflQN l>Re9 Sf>IU.WAY (N.T.~ . -~·1·:~ ~'.i'i~~·. F/GVR£ z. ll'PICAL SEAL JOINT (Nl.5) T.C.S #()lg ~~K R~Lt RIP~ RC>..\> I
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FIGURE /./. C~cRG1E APRON (N.15J
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Britt Rice
Lake, Dam, and Spillway
Thomas Caruthers League, A - 9
College Station, Brazos County, Texas
Prepared for:
Britt Rice
Britt Rice Electric
3002 - D Longmire
College Station, TX 77845
(409) 693 -4076
Prepared By:
GARRETT ENGINEERING
CIOlll&TillG ENZ!CLMG a LAlll WY11G
.... CMllRc.BPaMWAY, IURlt•·mlYM.IEXAS naa.c.., ....... , .. M-aM . .
* August, 1996 *
'
Britt Rice
Lake, Dam, and Spillway
Thomas Caruthers League, A-9
College Station, Brazos County, Texas
Prepared for:
Britt Rice
Britt Rice Electric
3002 - D Longmire
College Station, TX 77845
(409) 693 -4076
Prepared By:
GARRETT ENGINEERING
COlllULTllG OW I LNID 5'llV!YllG
4M4CMllR~PAMWAY, SUITU•-IRYAll. TEXAS nm-c.., ..... _,.., ....... . .
* August, 1996 *
The project site is located on a 61.08 acre tract, on the northwest side of Bird
Pond Road. The lake, which is in the east corner of the property, collects run-
off from approximately 21.14 acres.
The flow from the drainage basin (in cubic feet per second (cfs)) was determined
to be 86.12 cfs for the 100-year storm. This was determined from the Rational
Method as follows:
where:
Q=C*i*A
Q = flow in cfs
· i = intensity in in. /hr.
A = area in acres
C = runoff coefficient
= 11.64 in./hr. for 100-yr. storm
= 21.14 acres
= 0.35 (value for unimproved land)
Q = 0 .35 • 11.64 • 21.14 = 86.12 cfs
According to Manning Pipe Theory, an 5' line graded at 0.54% can carry 190.80
cfs.
where:
Q = (1.49 / n) •A• R2J3 • 5 0.5
Q =flow in cubic feet per second (cfs)
n =Manning's roughness coefficient
n = 0.013 for reinforced concrete pipe
A = area of pipe in square feet
A= 7td 2 /4
A= 7t • (5)2 I 4 = 19.63
R = hydraulic radius = A I P
where:
A = area of pipe in square feet
P =wetted perimeter= 7t •diameter
p = 7t. 5 = 15. 71
R = 19.63 I 15.71 = 1.25
S = slope of pipe = 0 .0054
Q = (1.49 I 0.013) • 19.63 • i.25213 • 0.00540.5
Q = 190.80 cfs
Since the ratio ofloading to capacity is 86.12/ 190.80 = 0.45 , the resulting
velocity (from design tables) will be 0.975 of full flow velocity. Full flow velocity
is calculated as follows : .
Where:
V =QI A
full
v full = full flow velocity
Q =full flow capacity in cfs = 190.80 cfs
A= area of pipe in square feet= 19.63 ft2
. ~
v,u11 = 190.80 / 19.63 = 9. 72 ft/ sec
The resulting velocity for a pipe flowing at 0.45 full, being 0.975 of full flow
velocity, is thus:
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DEVELOPMENT PERMIT
PERMIT NO. 436
BRJTT RlCE SPILLWAY
FOR AREAS INSIDE THE SPECIAL FLOOD HAZARD AREA
RE: CHAPTER 13 OF THE COLLEGE STATION CITY CODE
SITE LEGAL DESCRIPTION:
Thomas Caruthers League, A-9
SITE ADDRESS:
Not Addressed
OWNER:
Britt Rice
Britt Rice Electric
3002 - D Longmire
College Station, Texas 77845
DRAINAGE BASIN:
Foxfire Tributary
TYPE OF DEVELOPMENT:
This permit is valid ONLY for the construction of the spillway as shown in the Britt
Rice Lake, Dam and Spillway Report by Garrett Engineering dated October 28,
1996. Contractor shall notify the City at 764-3570 at least 24 hours prior to
construction. Contractor shall prevent silt and debris from leaving the site in accordance
with the City of College Station Drainage Policy and Design Criteria. Owner and/or
contractor shall be responsible for any damage to existing city streets or infrastructure due
to heavy machinery and/or equipment.
In accordance with Chapter 13 of the Code of Ordinances of the City of College Station,
measures shall be taken to insure that debris from construction, erosion, and sedimentation
shall not be deposited in city streets , or existing drainage facilities .
I hereby grant this permit for development of an area inside the special flood hazard area.
All development shall be in accordance with the plans and specifications submitted to and
approved by the City Engineer in the development permit application for the above named
project and all of the codes and ordinances of the City of College Station that apply .
. l , =---Dal~~~~,__..__~---
;/ -f-·k
Date
Contractor Date
-
Britt Rice
Lake, Dam, and Spillway
Thomas Caruthers League, A - 9
College Station, Brazos County, Texas
Prepared for:
Britt Rice
Britt Rice Electric
3002 -D Longmire
College Station, TX 77845
(409) 693 -4076
Prepared By:
~
2 GARRETT ENGINEERING
-=-.TID I I Ill & Ulm ..wt11C .... CMl9l~.-v. 111111•-IBAll. 'IDAS nm • .-....-• .._.._...
-
Britt Rice
Lake, Dam, and Spillway
Thomas Caruthers League, A -9
College Station, Brazos County, Texas
Prepared for:
Britt Rice
Britt Rice Electric
3002 -D Longmire
College Station, TX 77845
(409) 693 -4076
Prepared By:
~
2 GARRETT ENGINEERING
COlmll.TllG BIGI IQ & Ulm WWIG
..-.c:.una~NMWAY. sum••·IRYAll. 1IXAS nm.,.., .......• .., 141-aM
* October, 1996 *
-
The project site is located on a 61.08 acre tract, on the northwest side of Bird
Pond Road. The lake, which is in the east comer of the property, collects run-
off from approximately 21 .14 acres .
The flow from the drainage basin (in cubic feet per second (cfs)) w a s determined
to be 86.12 cfs for the 100-year storm. This was determined from the Rational
Method as follows:
where:
Q=C*i*A
Q = flow in cf s
i =intensity in in./hr.
A = area in acres
C = runoff coefficient
= 11.64 in./hr . for 100-yr. storm
= 21.14 acres
= 0 .35 (value for unimproved land)
Q 100 = 0.35 * 11.64 * 21.14 = 86 .12 cfs
According to Manning Pipe Theory, an 5' line graded at 0.54% can carry 190.80
cfs .
where:
Q = (1.49 / n) *A* R2J3 * 5 0.5
Q = flow in cubic feet per second (cfs)
n = Manning's roughness coefficient
n = 0.013 for reinforced concrete pipe
A = area of pipe in square feet
A= 7td 2/4
A= 7t * (5)2 I 4 = 19.63
R = hydraulic radius = A I P
where:
A = area of pipe in square feet
P = wetted perimeter = 7t * diameter
P=7t*5= 15 .71
R = 19.63 I 15.71=1.25
S = slope of pipe= 0.0054
Q = (1.49 I 0 .013) * 19.63 * i.25213 * o .0054°·5
Q = 190.80 cfs
Since the ratio ofloading to capacity is 86.12/190.80 = 0.45, the resulting
velocity (from design tables) will be 0 .975 of full flow velocity. Full flow velocity
is calculated as follows:
Where:
V =Q I A
fu ll
v full = full flow velocity
Q = full flow capacity in cfs = 190.80 cfs
A= area of pipe in square feet= 19.63 ft2
v,un = 190.80 / 19.63 = 9. 72 ft/ sec
The resulting velocity for a pipe flowing at 0.45 full, being 0.975 of full flow
velocity, is thus:
v0.45Cull = 0.975 * 9. 72 ft/sec= 9.48 ft/sec
In this case, it is unlikely that pressure flow will occur in the 5' diameter
concrete pipe.
Since the Froude number of the outflow is less than one, a small baffled apron
drop spillway should be used instead of a Saint Anthony Falls (SAF) basin or
any of the types of U.S. Bureau of Reclamation (USBR) basins, to slow the
resulting velocity and help prevent erosion and scouring.
The design of the baffled apron drop followed the design procedures set forth
by the USBR's Design of Small Dams. These design procedures were obtained
from empirical data from several models of baffled chutes conducted at the
USBR. These procedures do not show how to determine the exiting velocity,
but do point out that "four rows of baffle piers are needed to establish full
control of the flow" (Design 366).
Four rows of baffle piers are provided (See Figure 1). Each baffle pier is 2'
wide, 1.25' high, with a top length of 9", and a base length of l' (see Figure 2).
The baffle piers along each row will be placed 2' apart, and the following row
will be staggered at a (pier-face to pier-face) distance of 2.5' (see Figure 1).
Each baffle pier will be reinforced with two #4 stirrups, placed 8" apart, and
each 8" from the ends (see Figure 2). These stirrups will be doweled 2" into the
existing concrete apron, with epoxy (see Figure 4).
The concrete apron begins at the end of the 5' reinforced concrete pipe, and
extends 13.5' downstream to serve as the apron for the spillway. The width of
this pad varies from 7', at the end of the 5' pipe, to 12', at the end of the apron.
Approximately 800 square feet ofT.C.S. #018 rock rubble rip-rap will also be
placed at the downstn~am side of the concrete apron to prevent erosion beyond
the concrete apron.
REFERENCE
Design of Small Dams. Prepared by the United States Department of the
Interior-Bureau of Reclamation. Water Resources Technical Publication: 1977.
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