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CERTIFlCATION
l, Joseph P. Schultz, Licensed Professional Engineer No. 65889, State of Texas, certify that this report
for the drainage design for the Graham Comer Plaza in College Station, Texas, was prepared by me in
accordance with the provisions of the City of College Station Drainage Policy and Design Standards
for the owners hereof, with the exception that storm water runoff detention is not being required for
this project since the site discharges directly into an existing drainage and irni11ediately into the I 00-
year floodplain limits.
Jose~}l&
TABLE OF CONTENTS
GRAHAM CORNER PLAZA
CERTIFICATION ................................................................................................................................................................. I
TABLE OF CONTENTS ....................................................................................................................................................... 2
LIST OFT ABLES .................................................................................................................................................................. 2
INTRODUCTION .................................................................................................................................................................. 3
GENERAL LOCATION AND DESCRIPTION ................................................................................................................. 3
FLOOD HAZARD INFORMATION ................................................................................................................................... 3
DEVELOPMENT DRAINAGE PATTERNS ...................................................................................................................... 3
DRAINAGE DESIGN CRITERIA····················································-··· ...................................... ~ ....................................... 3
STORM \VATER RUNOFF DETERMINATION .............................................................................................................. 4
STORM SEWER CUL VERT DESIGN ............................................................................................................................... 5
STORM SEWER PIPE & INLET DESIGN ........................................................................................................................ 5
CONCLUSIONS ..................................................................................................................................................................... 6
APPENDIX A ......................................................................................................................................................................... 7
Calculatio11s
EXHIBIT A ........................................................................................................................................................................... 19
Time of Coucentratio11 F/01v Path & Draiuage Area Map
EXHIBIT B ........................................................................................................................................................................... 21
Pre-and Post-Developmeut Drainage Area Map
EXHIBIT C ........................................................................................................................................................................... 23
Grading Plan
LIST OF TABLES
TABLE 1 -Rainfall Intensity & Runoff Data .......................................................................................... 4
TABLE 2 -Time of Concentration (tc) Equations .................................................................................. 5
DRAINAGE REPORT
GRAHAM CORNER PLAZA
INTRODUCTION
The purpose of this report is to provide th e hydrological effects of the construction of the
infrastructure for the Graham Comer Plaza project, and to show that the storm water runoff will
be controlled in such a manner so as to have minimal offsite or downstream impacl.
GENERAL LOCATION AND DESCRIPTION
The project is located on 10.73 acres located in College Station, Texas. Most o f the site is open
land with grass. A 1.093 acre portion along the North Fork of Lick Creek is being dedicated to
the City of College Station as green way. This area is primarily wooded. The existing ground
elevations range from elevation 2 76 to elevation 288 . The general location of the project site is
shown on the vicinity map in Exhibit A.
FLOOD HAZARD INFORMATION
The project site is located in the Lick Creek Drainage Basin. The site is located in a Zone X
Area according to the Flood lnsurance Rate Map (FIRM) prepared by the Federal Emergency
Management Agency for Brazos County, Texas and incorporated areas dated February 9, 2000,
panel number 48041C0201 D. Zone X Areas are detem1ined to be outside of the 500-yr
floodplain. This site is not within the limit of study for the FIRM. However, the approximate
100-year floodplain limits and the flood way were previously detem1ined by Robertson
Engineering for the City of College Station, and these limits were included on the Final Plat for
the project. This floodplain area is also shown on Exhibit A. Most of the floodplain area and
all of the flood way for this tract is located in the Greenways Dedication Area.
DEVELOPMENT DRAINAGE PATTERNS
The storm water runoff from the site flows into the North Fork of Lick Creek. The runoff from
this development will be discharged into the creek and the 100-year floodplain; therefore, no
detention is required for this project. The drainage area boundaries are shown on Exhibit A.
DRAINAGE DESIGN CRITERIA
The design parameters for the storm sewer are as follows:
• The Rational Method is utilized to dete1mine peak storm water runoff rates fo r the
stom1 sewer design.
• Design Stonn Frequency
Stom1 culverts
Sto1111 sewer system
25-year storm event
I 0 and I 00-year storms event s
• Runoff Coefficients
U ndevelopcd areas
Developed areas
Open space areas
Impervious surfaces
c = 0.30
c = 0.85
c = 0.40
c = 0.90
• Rainfall Intensity equations and values for Brazos County can be found in Table 1.
• Time of Concentration, tc -Calculations for are based on the method found in the TR-
55 publication. Refer to Appendix A for the equations and calculations. The drainage
runoff flow paths used for calculating the times of concentration for the desi gn of
Culvert No . 1 are shown in Exhibit B. For smaller drainage areas, a minimum tc of 10
minutes is used to detem1ine the rainfall intensity values.
STORM WATER RUNOFF DETERMINATION
The peak runoff values were detem1ined in accordance with the criteria presented in the
previous section for the 10-, 25-and 100-year storm events. The runoff coefficients are
based on the development of this tract. The drainage areas are shown in Exhibit A.
Runoff conditions are summarized in Table 1. The time of concentration equations are
shown in Table 2.
TABLE 1 -Rainfa ll Intensity & Runoff Data
Area c
Area# (acres) c, C2 C3 CTOt.ll A, Az Al Total
Area A 0.73 5.26 1.04 7.03 0.9 0.3 0.8 0.43
101 2.36 2.36 \.0.40 0.40
102 1.20 1.20 0.40 0.40
201 2.36 2.36 0.85 0.85
202 1.20 '~ 0.85 0.85 --------·----------203 0.23 0.23 0.90 0.90 ----------------204 0.23 0.23 0.90 0.90 ·--. . -·---·--· 205 0.09 0.09 0.90 0.90 ----------· ---·-· -· ---------· ------· 206 0.10 0.10 0.90 0.90 ·----·------··------------·----· --·-·-·--··-207 1.07 1.07 0.85 0.85
The Rational Method:
Q=CIA I = b I (tc+d)0
Q =Flow (cfs)
A= Area (acres)
C = Runoff Coeff.
le =Time of concentration (min)
I = Rainfall Intensity (in/hr)
Brazos County:
10 year storm
b = 80
d = 8.5
e = 0.763
25 year storm
b = 89
d = 8.5
e = 0.75
100 year storm
b = 96
d = 8.0
e = 0.730
.)
tc
(min)
17.8
10
10
10
10
10
10 ----··-10
10 ----10
10 year storm
1,. a,.
(in/hr) (cfs)
6.602 19.96
8.635 8.15
8.635 4.14
8.635 17.32
8.635 8.81
8.635 1.79 -·--8.635 1.79 ·---·-·· 8.635 0.70
8.635 0.78 ,_ -·--8.635 7.85
tc = U(V*60)
L = Length (ft)
25 year storm
l2s 02s
(in/hr) (cfs)
7.564 22.86
9.861 9.31
9.861 4.73
9.861 19.78
9.861 10.06
9.861 2.04 --9.861 2.04 -------· 9.861 0.80
9.861 0.89
9.861 ·s.g-y--
V =Velocity (fUsec)
100 year storm
1, .. a, ..
(in/hr) (cfs)
8.949 27.05
11.639 10.99
11.639 5.59
11 .639 23.35
11 .639 11.87
11 .639 2.41
11.639 2.41
11 .639 0.94 ---· 11 .639 1.05 --·-···-· -... 11.639 10.59
TABLE 2 -Time of Concentration (tc) Equations
Tlie ti111e o_f co11ce11tratio11 \llGS deter111i11 ed using 111etlwdsfo1111d in TR-55 . "Urhon
Hydrology for S111all Watersheds. " The equa lions a re as .follows:
Time of Concentration :
for Shallow Concentrated Flow :
Tc = Tt(slu .. ·cf flow)+ T1(concc111r;1h.·tl shl'l't llow}
where: T1 =Travel Time, minutes
T, =L I (60 *V)
where: T1 =tra ve l time, minutes
V =Velocity, fps (See Fig 3-1 , App. E)
L = now length, feet
Refer to Appendix A fo r calculations.
STORM SEWER CULVERT DESIGN
A stonn sewer culvert is proposed at the State Highway 6 West Frontage Road driveway
fo r this development. This culvert will be des igned for the 25-year stom1 event, and it will
also pass the lOO-year stonn event without overtopping the driveway. Refer to Appendi x
A for the culvert calculator data sheets for the 25-and 100-year stonn events.
STORM SEWER PIPE & INLET DESIGN
This project consists of the construction of the pri vate driveway and stom1 sewer system
and the public water and sanitary sewer lines for this development. No buildings or
structures are proposed at this time. The private stom1 sewer system is designed to collect
the developed condition runoff from Lots 1, 2, 4 & 5, and discharge it into the North Fork
of Lick Creek. Lots 3 & 6 will have separate storm sewer systems that will discharge
directly into the creek. The private driveway and the storm sewer curb inlets were
designed for the existing conditions of the property.
The storm sewer pipe system is designed for the future developed condition of the
property. Pipes 1 & 2 will be constructed with the ends plugged until development of Lots
1, 4 or 5. Inlets and additional storm sewer piping will be required when the development
plan for each lot is prepared. A drainage report shall be prepared for each lot before it is
developed in order to verify that the calculated runoff values used in this report are not
exceeded.
As previously stated, the storm water runoff from this site will be collected by the
proposed storm sewer system and then flow directly into the North Fork of Lick C reek.
The stom1 sewer piping for this project has been selected to be Reinforced Concrete Pipe
(RCP) meeting the requirements of ASTM C-76, Class III pipe meeting the requirements
of ASTM C-789. The curb inlets will be cast-in-place concrete.
Appendix A presents a summary of the stom1 sewer inlet design parameters and
calculations. The inlets were designed based on a 10-year design storm. As per Coll ege
Station guidelines, the capacities of inlets in sump were reduced by 10% to allow !o r
clogging.
inlets were located to maintain a gutter flow depth of 6" or less. This design depth will
prevent the spread of water from overtopping the curb of the road for the I 0-year storm
event. Refer to Appendix A for a summary of the gutter flow depths. The runoff
intercepted by the proposed stom1 sewer inlets was calculated using the following
equations. The depth of flow in the gutter was determined by using the Straight Crown
Flow equation. The capacities for the inlets in sump (Inlets l & 2) were calculated using
the [nlets in Sumps, Weir Flow equation with a maximum allowable depth of T' (5" gutter
flow plus 2" gutter depression). These equations and the resulting data are also
summarized in Appendix A. There are no inlets on grade proposed for this development.
Appendix A contains a summary of the storm sewer pipe design parameters and
calculations. All pipes are l 8" in diameter or larger. The pipes for the storm sewer system
were designed based on the l 0-year stonn event, and they will also pass the l 00-year
stonn event. Based on the depth of flow in the street determined for the 100-year stom1
event, this runoff will be contained within the street right-of-way until it enters the stom1
sewer system. The velocity of flow in the stom1 sewer pipe system is not lower than 2.5
feet per second, and it does not exceed 15 feet per second. As the data shows, even during
low flow conditions, the velocity in the pipes will exceed 2.5 feet per second and prevent
sediment build-up in the pipes. The maximum flow in the storm sewer pipe system will
occur in Pipe No. 4. The maximum velocity for the pipe system in this development will
be 8.9 feet per second and will occur in Pipe No. 4. A concrete headwall is proposed for
the end of Pipe 4 to dissipate the energy of the discharge and control erosion. Appendix A
contains a summary of the pipe calculations as well as a summary of the flows through the
stonn sewer system for the 10 and 100-year events.
A grading plan for this site is provided as Exhibit C. The private driveway is designed so
that it is above the base flood elevation for the North Fork of Lick Creek. The site will be
graded so that if there is any flow that exceeds the capacity of the stom1 sewer system it
would flow over the private driveway curb and immediately enter the floodplain area. The
outlet of Pipe 4 is below the Base Flood Elevation so there will be a tail water effect on the
discharge of Pipe 4. However, due to the close proximity of this site to the stream channel
and its location in the watershed, the peak runoff from this site will occur much sooner
than the peak runoff for the stream. Therefore, the tailwater condition should have little
effect on the capacity of the storm sewer pipe. As stated previously, the area adjacent to
Storm Inlet 2 has been designed to allow excess runoff to flow directly into the floodplain
area if the stom1 sewer pipes cannot carry the entire runoff from the site. This will limit
the depth of water in the private drive during these circumstances.
CONCLUSIONS
The construction of this project will increase the storm water runoff from this site.
However, the runoff wi 11 be carried through the proposed sto1111 sewer system and
immediately into the I 00-year floodplain. The increased flow in this tributary should not
have a significant impact on the surrounding property. No flood damage to downstream or
adjacent landowners is expected as a result of this development.
APPENDIX A
Calculations
Graham Corner Plaza
Existing Inlet A Bypass Calculations
The Rational Method:
Q =CIA
0 = Flow (cfs)
C = Runoff Coeff.
I = Rainfall Intensity (in/hr)
A = Area (acres)
Area
Inlet I I Total n A, A,
(acres)
A o.74 I 0.24 I o.96
c,
0.9
Top of curb = 1" lower than centerline of road
Transverse (Crown) slope (ft/ft) = 0.0200
Straight Crown Flow !Solved to find actual depth of flow. yl:
Q = 0.56 • (z/n) • S112 • y913 Q y ={QI [0.56 • (z/n) • S112]}318
(Eqn from C. of C.S. Design Standards, page 30; Design Procedures for Straight Crowns)
n = Rou.ghness Coefficient= 0.018
z = Reciprocal of crown slope = 50
S = StreeVGutter Slope (ft/ft)
y = Depth of flow at inlet (ft)
c
010 0 25 o, .. s Y10 Yzs Y100
c, Cr or.al
(cfs) (cfs) (cfs) (ft/ft) (ft) I (In) (ft) I (In) (ft) I
0.4 0.76 6.560 7.514 6.669 0.0050 o.346 I 4.17 o.366 I 4.39 o.369 I
(In)
4.67
Capacity of Inlets on grade:
Oc = 0.7 * [1/(H1 -H2)] • [H1
512-H2
512]
Oc = Flow capacity of inlet (cfs)
H1 =a+ y
H2 = a = gutter depression (2" Standard; 4" Recessed)
y = Depth of flow in approach gutter (ft)
Standard Inlet Length L = 15', a= 2" = 0.167'
Oc10 Oc1oeypau Oczs Oc2seypau Oc100
(cfs) (cfs) (cfs) (els) (cfs)
5.40 1.16 5.62 1.90 5.91
Oc1ooeyp.ss
(els)
2.95
Time of Concentration Calculations
Drainage Area for Proposed Culvert No. I
Flow along Pa vement Seglllent #/:
Flow length = 370' = L
Slope = 0.8%
For paved surface at 0.8%, Velocity V =1.8 fp s (see Fig. 3-1)
T, = U(60*V)
= 370' I (60*1.8) = 3.4 minutes
Flow along Pavement Segment #2:
Flow length = 615 ' = L
Slope = 1.2%
For paved surface at 1.2%, Velocity V =2.2 fps (Fig 3-1)
= 615 ' I (60*2.2) = 4.7 minutes
Flow along Pavement Seg111ent #3 :
Flow length = 565 ' = L
Slope = 1.0%
For paved surface at 1.0%, Velocity V =2.0 fps (Fig 3-1)
~ = 565 ' I (60*2.0) = 4.7 minutes
Flow thru Ditch Segment #4: (Refer to attached channel calculations)
Trapezoidal channel with l :5 sides, Bottom width = 24"
Flow length = 690' = L
Slope = 0.45%
(Note: slope & length estimated from topography.)
n = 0.035
Area= 7.03 acres (Drainage Area A)
Q25 = 22.86 cfs (using tc = 17.8 minutes, C = 0.43)
Upstream bypass from Existing Inlet A= I . 90 cfs
Total Q2s = 24.8 cfs
From Manning's data, Velocity, V = 2.3 fp s
t1 = 300 sec= 5.0 minutes
Tc = 3.4 + 4.7 + 4.7 + 5.0 = 17.8 minutes
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Ditch for Tc calculations .t xt
Channel Calculator
Given Input Data:
shape .......................... .
solving for .................... .
Fl ow rate ....................... .
slope .......................... .
Manning's n .................... .
Height ......................... .
Bottom width ................... .
Left slope ..................... .
Right slope .................... .
computed Results:
Depth ........................... .
vel oc1 ty ....................... .
Full Fl owrate .................. .
Flow area ...................... .
Fl ow perimeter ................. .
Hydraulic radius ............... .
Top width ...................... .
Area ........................... .
Perimeter ...................... .
Percent full ................... .
Trapezoidal
Depth of Flow
24.9000 cfs
0.0045 ft/ft
0.0350
24.0000 in
24.0000 in
0.2000 ft/ft (V/H)
0 .2000 ft/ft (V/H)
15 .4741 in
2.2858 fps
71. 5805 cfs
10.8932 ft2
181.8058 in
8. 6280 fo
178.7413 in
24.0000 ft2
268.7529 in
64.4755 %
PilCJe 1
Graham Corner Plaza
p· & C I rt C I I f 1pe u ve a cu a ions
Inlet Outlet 10-year storm 100-year storm Pipe# Size Length Slope Invert Elev Invert Elev 010 V10 Travel Time, tr10 0100 V100 Travel Time, lnoo
% Full % Full (in) (ft) (%) (ft) (ft) (cfs) (fps) (sec) (min) (cfs) (fps) (sec) (min)
1 18 45.3 1.20 282.54 282.00 7.85 6.6 63.7 7 0.11 10.59 6.9 81.2 7 0.11
. --···-···-·------------· ----------·· -·------· ·-------------------------------·-----·-··-2 30 191 .5 0.70 277.62 276.28 25.17 7.2 67.0 27 0.44 33.93 7.3 89.8 26 0.44 -· ----------------·--·---·---·--·-----------3 36 25.5 0.70 275.78 275.60 36.47 7.9 61 .9 3 0.05 49.16 8.3 77.7 3 0.05 .. ---------------------------·------·----------------------------4 36 80.3 0.80 275.50 274.86 39.03 8.5 61 .9 9 0.16 52.61 8.9 77 .8 9 0.15
Culvert Data 25-year storm 100-year storm
Culvert No. 1 2x24 48.0 0.50 282.14 281 .90 24.80 3.9 . 12 0.21 30.00 4.8 . 10 0.17
Top of Road= 284.85 Headwater = 284.36 Headwater= 284.59
Inlet 1 Pipe 2
010 Areas 101 , 102, 203, 205 = 14.78 010 Area 201 , 207 = 25.17
02~ Areas 101, 102, 203, 205 = 16.88 025 Area 201 , 207 = 28.75
0100 Areas 101 , 102, 203, 205 = 19.93 0100 Area 201 , 207 = 33 .93
Inlet 2 Pipe 3
010 Areas 204, 206 = 2.56 010 Areas 201, 202, 203, 205, 207 = 36A7
025 Areas 204, 206 = 2.93 025 Areas 201, 202, 203, 205, 207 = 41 .65
0100 Areas 204, 206 = 3.46 0100 Areas 201 , 202, 203, 205, 207 = 49 .16
.E.l.P.Ll Pipe 4
010 Area 207 = 7.85" 010 Areas 201 th ru 207 = 39 .03
0 25 Area 207 = 8.97 0 25 Areas 201 thru 207 = 44.58
0100 Area 207 = 10.59 0100 Areas 201 thru 207 = 52.61
Culvert No. 1
0 25 Area A, Bypass from Inlet A = 24 .8
0100 Area A, Bypass from Inlet A = 30.0
. ,
Pipe 1 -10 Year Storm
Manning Pipe Calculator
Given Input Data :
Shape .......................... .
Solving for .................... .
Diameter ....................... .
Flowrate ....................... .
Slope .......................... .
Manning's n .................... .
Computed Results:
Depth ............. .
Area .......................... , .
Wetted Area .................... .
Wetted Perimeter ............... .
Perimeter ...................... .
Velocity ....................... .
Hydraulic Radius ............... .
Percent Full ................... .
Full flow Flowrate ............. .
Full flow velocity ............. .
Circular
Depth of Flow
18.0000 in
7 .8500 cfs
0.0120 ft/ft
0 . 0140
11. 4659 in
1.7671 ft2
1.1879 ft2
33.2699 in
56.5487 in
6.608 3 fps
5 .1415 in
63.6992 %
10.6850 cfs
6 .0465 fps
Pipe 1 -100 Year Storm
Manning Pipe Calculator
Given Input Data:
Shape .......................... .
Solving for .................... .
Diameter ....................... .
Flowrate ....................... .
Slope .......................... .
Manning' s n .................... .
Computed Results:
Depth .......................... .
Area ........................... .
Wetted Area ...... · .............. .
Wetted Perimeter ............... .
Perimeter ...................... .
Velocity ....................... .
Hydraulic Radius ............... .
Percent Full ................... .
Full flow Flowrate ............. .
Full flow veloc ity ............. .
Graham Corner Plaza
Co l l.ege Stat ion . Te;.:.:1 ~;
Circular
Depth of Flow
18 .0000 in
10.5900 cfs
0 .0120 ft/ft
0 .0140
14.6100 in
1.7671 ft2
1.5363 ft2
40 .3883 in
56 .5487 in
6.8931 fps
5 .4775 in
81 .1667 %
10 .6850 cfs
6 .0465 fps
Pipe 2 -10 Ye ar Storm
Manning Pipe Calc ulator
Given Input Data :
Shape .......................... .
Solving for .............. .' ..... .
Diameter ....................... .
Flowrate ....................... .
Slope .......................... .
Manning's n .................... .
Co mputed Results :
Depth .......................... .
Area ............................ .
Wetted Area .................... .
Wetted Perimeter ............... .
Perimeter ...................... .
Velocity ....................... .
Hyd r aulic Radi us ............... .
Percent Full ................... .
Full flow Flowr ate ............. .
Full flow velocity ............. .
Circula r
Depth of Flow
30 .0000 in
25 .1700 cfs
0.0070 ft/ft
0 .0140
20 .1101 in
4 .9087 ft2
3 .4980 ft2
57 .5529 in
94 .2478 in
7 .1955 fps
8 .752 2 in
67 .0336 %
31 .8662 cfs
6 .4917 fps
Pipe 2 -100 Year Storm
Manning Pipe Calculat or
Given Input Data:
Shape .......................... .
Solving for .................... .
Diameter ....................... .
Flowrate ....................... .
Slope .......................... .
Manning's n .................... .
Computed Results :
Depth .......................... .
Area ........................... .
Wetted Area .................... .
Wetted Perimeter ............... .
Perimeter ...................... .
Velocity ....................... .
Hydraulic Radius ............... .
Percent Full ................... .
Full flow Flowrate ............. .
Full flow velocity ............. .
Graham Cor:net· Plaza
Col l ege St<1t.i o n . Te;-:a ~_;
Circular
Depth of Flow
30.0000 in
33.9300 cfs
0 .0070 ft/ft
0. 0140
26.9374 in
4 .9087 ft2
4.6454 ft2
74.7349 in
94 .2478 in
7.3040 fps
8 .9508 in
89.7912 %
31 .8662 c f s
6 .4917 fps
Pipe 3 -10 Year Storm
Manning Pipe Calculator
Given Input Data:
Shape .......................... .
Solving for .................... .
Diameter ....................... .
Flowrate ....................... .
Slope .......................... .
Manning ' s n .................... .
Computed Results:
Depth .......................... .
Area ............................ .
Wetted Area .................... .
Wetted Perimeter ............... .
Perimeter ...................... .
Velocity ....................... .
Hydraulic Radius ............... .
Percent Full ................... .
Full flow Flowrate ............. .
Full flow velocity ............. .
Circular
Depth of Flow
36.0000 i n
36 .4700 cfs
0.0070 ft/ft
0. 0140
22.2742 i n
7 .0686 ft2
4.5927 ft2
65.1795 in
113. 0973 in
7.9408 fps
10 .1466 in
61 .8728 %
51 .8179 cfs
7 .3307 fps
Pipe 3 -100 Year Storm
Manning Pipe Calculator
Given Input Data:
Shape .......................... .
Solving for .................... .
Diameter ....................... .
Flowrate ....................... .
Slope .......................... .
Manning' s n .................... .
Computed Results:
Depth .......................... .
Area ........................... .
Wetted Area .................... .
Wetted Perimeter ............... .
Perimeter ...................... .
Velocity ....................... .
Hydraulic Radi us ............... .
Percent Full ................... .
Full flow Flowrate ............. .
Full flow velocity ............. .
Graham Corner Plaza
Co I I ege St.al ion. '!'(·:·:<1~;
Circular
Depth of Flow
36 .0000 in
49.1600 cfs
0.0070 ft/ft
0 . 0140
27.9742 in
7 .0686 ft2
5 .8936 ft2
77 .6919 in
113 . 0973 in
8.3412 fps
10.9237 in
77 .7 062 %
51.8179 cfs
7 .3307 fps
Pipe 4 -10 Year Storm
Manning Pipe Calculator
Given Input Data :
Shape .......................... .
Solving for .................... .
Diameter ....................... .
Flowrate ....................... .
Slope .......................... .
Manning's n .................... .
Computed Results:
Depth .......................... .
Area .......................... , .
Wetted Area .................... .
Wetted Perimeter ............... .
Perimeter ...................... .
Velocity ....................... .
Hydraulic Radius ............... .
Percent Full ................... .
Full flow Flowrate ............. .
Full flow velocity ............. .
Circular
Depth of Flow
36 .0000 in
39 .0300 cfs
0.0080 ft/ft
0.0140
22.2902 in
7 .06 86 ft2
4 .5966 ft2
65.2126 in
113.0973 in
8 .4910 fps
10 .1501 in
61.9174 %
55.3957 cfs
7 .8369 fps
Pipe 4 -100 Year Storm
Manning Pipe Calculator
Given Input Data :
Shape .......................... .
Solving for .................... .
Diameter ....................... .
Flowrate ....................... .
Slope .......................... .
Manning's n .................... .
Computed Results:
Depth .......................... .
Area ........................... .
Wetted Area .................... .
Wetted Perimeter ............... .
Perimeter ...................... .
Velocity ....................... .
Hydraulic Radius ............... .
Percent Full ................... .
Full flow Flowrate ............. .
Full flow velocity ............. .
Graham Corner Plaza
Col l e9e SL1t i o n , Te :-:.'1!;
Circular
Depth of Flow
36.0000 in
52.6100 cfs
0.0080 ft/ft
0.0140
28.0020 in
7 .0686 ft2
5.8994 ft2
77.7587 in
113 .0973 in
8 .9179 fps
10 .9250 in
77 .7834 %
55.3957 cfs
7 .8369 fps
Culvert 1 -25 Year Storm
Culvert Calc ulator
Entered Data :
Shape ........... .
Number of Barre ls
Solving for ..... .
Chart Number .... .
Scale Number ................... .
Chart Description .............. .
Scale De scripti on .............. .
Overtopping .................... .
Flowrate ....................... .
·Manning's n .................... .
Roadway Elevation .............. .
Inlet Elevation ................ .
Outlet Elevation .
Diameter ................. .
Length ................... .
Entrance Loss ............ .
Tailwa t er ................ .
Computed Results :
Headwater ...................... .
Slope .......................... .
Velocit y ....................... .
Circular
2
Headwater
1
3
CONCRETE PI PE CULVERT ; NO BEVELED R IrJG ENTRANCE
GROOVE END ENTRANCE , PIPE PROJECTING FROM FILL
Off
24.8000 cf s
0 .0140
284 .8500 f t
282 . 1400 ft
281.9000 ft
24 .0000 in
48 .0000 ft
0.2000
2 .0000 f t
284 .3570 ft Outle t Control
0.0050 ft/ft
3.9470 fps
Culvert 1 -100 Year Storm
Culvert Calculator
Entered Data :
Shape .......................... .
Number of Barrels .............. .
Solving for .................... .
Chart Number ................... .
Scale Number ................... .
Chart Description .............. .
Scale Description .............. .
Overtopping .................... .
Flowrate ....................... .
Manning's n .................... .
Roadway Elevation .............. .
Inlet Elevation ................ .
Outlet Elevation ............... .
Diameter ....................... .
Length ......................... .
Entrance Loss .................. .
Tailwater ...................... .
Computed Results :
Headwater ...................... .
Slope .......................... .
Veloc i ty ....................... .
Graham Co 1·ne1· Plaza
Co l l ege Station , Te>:as
Circular
2
Headwater
1
3
CONCRETE PIPE CULVERT ; NO BEVELED RING ENTRANCE
GROOVE END ENTRANCE, PIPE PROJECTING FROM FILL
Off
30.0000 cfs
0 -0140
284.8500 ft
282 . 1400 ft
281 .9000 ft
24.0000 in
48.0000 ft
0 .2000
2 .0000 ft
284.5919 ft I nlet Contr ol
0 .0050 ft/ft
4 .7746 fps
Graham Corner Plaza
Inlet Length Calculations
Inlet#
1
2
Inlets 1 & 2
Inlets In Sump
Flow from A c a,. Ocury ovu Length Area# (acres) (cfs) (cfs) from Inlet II
15' 101, 102 3.56 0.4 12.30 --··-·-----·---203,205 0.32 0.90 2.49 -
5' 204 0.23 0.9 1.79 --··----·-----------206 0.10 0.9 0.78 -
20' Total Length a,oo = 23.38 cfs Y100 = 0.533 ft = 6.40 in
Transverse (Crown) slope (ft/ft)
= 0.0200
Straight Crown Flow !Solved to find actual depth of flow, yl:
Q = 0.56 * (z/n) * S112 * y813 q y ={Q I [0.56 * (z/n) * 5 112])318
n = Roughness Coefficient = 0.013
S = StreeVGutter Slope (ft/ft)
y = Depth of flow at inlet (ft)
Capacity of Inlets on grade:
Oc = 0.7 * [1/(H1 -H2)] • [H1
512-H2
512]
Oc = Flow capacity of inlet (cfs)
H, =a+ y
H2 = a = gutter depression (2" Standard; 4" Recessed)
y = Depth of flow in approach gutter (ft)
Oro111
(cfs)
12.30
2.49
1.79
0.78
1 O year storm 100 year storm
Orotal+10% Y 1 O;ictual gutter depth L10-Req'd . L10 .... ctual a, •• Ocarry over
(cfs) (ft) (In) (ft) (ft) (cfs) (cfs) from Inlet#
13.53 0.311 3.73 16.57 ----12.18 15 ---· --------2.74 0.171 2.05 3.35 -
1.97 0.151 1.81 2.41 ----·------2.11 5 ---------·-0.85 0.110 1.33 1.05
•using yrN• = r = 0.583'
z = Reciprocal of crown slope
50
Inlets in sumps, Weir Flow:
L = QI (3 * y312) q y = (QI 3L)213
L = Length of inlet opening (ft)
Q = Flow at inlet (cfs)
y = total depth of flow on inlet (ft)
max y for inlet in sump = 7" = 0.583'
-
OTotal Orou1+10•1io
(cfs) (cfs)
16.57 18.23 ------3.35 3.69
2.41 2.65 -----
1.05 1.15
Y100.Jnlet
(ft) (In)
0.619 7.43
0.401 4.81
EXHIBIT A
Time of Concentration Flow Path & Drainage Area Map
I'>
· na~
'I lj II I
I
McCLURE & BROWNE ENGINEERING/SURVEYING, INC.
1008 Woodcreek Drive, Suite 103 •College Station, Texas 77845
(979) 693-3838 •Fax (979) 693-2554 •Email: mcclurebrovme@verizon.net
November 15, 2005
Mr. Alan Gibbs
City of College Station
P.O. Box 9960
College Station, Texas 77842
Re: Popeye's Chicken Site Plan -Drainage Letter Report
Dear Alan:
The site plan for the new Popeye's Chicken Restaurant being proposed in the Graham Comer Plaza
is designed to comply with the drainage requirements and report that was prepared for that subdivision. The
drainage report states that no detention is necessary for the Graham Comer Plaza, but that each lot must
prepare a drainage report indicating that the development does not exceed the capacity of the underground
storm drain. The purpose of this letter is to provide a brief analysis of the anticipated runoff from the site.
The new restaurant will be located on Lot #4 of the Graham Comer Plaza, on the southwest comer
of the intersection between Graham Road and the private roadway through the subdivision. An 18" pipe was
extended across the private roadway to serve the site during initial construction as shown on the Drainage Area
Map in Exhibit A The drainage report for the subdivision indicates that the capacities of that pipe are as
follows :
Q10 = 7.85 cfs
Q100 = 10.59 cfs
Using the Rational Formula in Exhibit B, we are able to compute the following flowrates from the
planned development of the Popeye's Chicken Restaurant site.
Q10 = 3.70 cfs
Q100 = 5.40 cfs
From this comparison we conclude that the flow coming from the proposed site and the adjoining
drainage area is less than the capacity of the 18" outfall pipe, therefore no on-site detention is necessary for
the development of the property.
·-----1
~ J:!-Q.:~
~g t CQ
0 '-l ~
E: lt)
c:J ...... l -1::: 0 t> .......
(5
Graham Road
•
5' Std. Inlet
Graham Corner Plaza
Lot 6R, Block 1
l
I
Scale: 1" = 40'
~
J:! -Q.:
~"ti 0 t(Q ~ ~
E: ...... c:J 0 ..s:::: ....... ~ <.!)
POPJ:YrS CIDCKEN ~ BJSCUJ1S
"Exhibit A•
DRAINAGE MAP I ~'M'~~~'i=vlNG, INC.
1008 Woodcreek Drive, Suite 103
College Station, Texas 77845
(979) 693-3838
DATE: NOV, 2005
DRAWN BY: JL.R
DESIGNED BY:_...:!!:!t
10180001-DM.dwg
;:i 3: c 0 a: w ..I < ;:i c. 0 I&.
w 0 w .... 0
C> a: ..I c. z < z
< < ~ ;:i
0 w 0 5 ::c :E z ..I ..I ..I a: .... ~ < ~ w ~ ~~ .... ~ 0 ~~ 0 0 .... 0 c. .... o~
NO. AC. 0.4 0.85 0.9 ft.
Popeye's 0.51 0.05 0.00 0.46 0.43 14.0
EXHIBIT B
Rational Formula Drainage Area Calculations
Popeye's Chicken & Biscuits
~ 3: 3: ..I I&. 0 0 0 ..I ..I z I&. I&. ~ 5 a: ::c a: u 0 u w .... w .... .... a: ..I I: C> I: ..I 0 u w ..I ::Jz ::J ..I ..I w >ct ~ Ci I/) a .,,
Ou. C> ~ C> ~ 0 ::J ~ !!? a
ft. ft. ft. ft/s min min In/Hr cfs In/Hr cfs
0.5 130.0 0.8 1.5 1.6 10.0 6.33 2.7 7.7 3.3
0 .,,
0 .... .,, N !: a ~ a
In/Hr cfs In/Hr cfs
8.6 3.7 9.9 4.3
0 0 .,,
!!? a
In/Hr cfs
11.1 4.8
0 0 0 0 .... !: a
In/Hr cfs
12.5 5.4
11/15/2005
10180001-dra.xls
Exhibit 8
•