SW3230303_Design Calculations_20230803

Appendix C
Supporting Data
NOAA Atlas 14 Precipitation Data
Weighted Runoff Coefficient(C) Calculations
Stormwater Studios Plan, Profiles& Tables
Riprap Outlet Protection Calculations

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NOAA Atlas 14 Precipitation Data

NOAA Atlas 14,Volume 2,Version 3
,fi''" Location name:Waxhaw,North Carolina,USA* '✓ '`''
B Latitude: 34.9531°,Longitude: -80.7644° k '1UHA
vv
NIP Elevation:555.27 ft**
'ftra *source:ESRI Maps .,ry0"
**source:USGS
POINT PRECIPITATION FREQUENCY ESTIMATES
G.M.Bonnin,D.Martin,B.Lin,T.Parzybok,M.Yekta,and D.Riley
NOAA,National Weather Service,Silver Spring,Maryland
PF tabular I PF graphical I Maps &_aerials
PF tabular
PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches/hour)1
Average recurrence interval(years)
Duration
1 2 5 10 25 50 100 200 500 1000
5-min 5.03 5.93 6.88 7.58 8.39 8.94 9.46 9.91 10.5 10.8
_(4.63-5.46) (5.45-6.46) (6.31-7.49) (6.95-8.23) (7.66-9.10) (8.12-9.70) (8.54-10.2) (8.92-10.8) (9.31-11.4) (9.56-11.8)
10-min 4.01 4.74 5.51 6.07 6.68 7.12 7.51 7.86 8.26 8.52
_ (3.70-4.36) (4.36-5.17) (5.06-6.00) (5.56-6.58) (6.10-7.25) (6.47-7.72) (6.79-8.14) (7.07-8.53) (7.36-8.98) (7.54-9.28)
15-min 3.34 3.98 4.64 5.11 5.64 6.01 6.33 6.61 6.93 7.13
(3.08-3.63) (3.65-4.33) (4.26-5.06) (4.68-5.55) (5.15-6.12) (5.46-6.52) (5.72-6.86) (5.94-7.17) (6.18-7.54) (6.30-7.77)
30-min 2.29 2.74 3.30 3.70 4.18 4.53 4.85 5.15 5.52 5.77
(2.11-2.49) (2.52-2.99) (3.03-3.59) (3.39-4.02) (3.82-4.54) (4.11-4.91) (4.38-5.25) (4.63-5.58) (4.92-6.00) (5.10-6.29)
60-min 1.43 1.72 2.12 2.41 2.78 3.07 3.34 3.61 3.96 4.21
(1.32-1.55) (1.58-1.88) (1.94-2.30) (2.21-2.62) (2.54-3.02) (2.79-3.33) (3.02-3.62) (3.24-3.92) (3.53-4.30) (3.73-4.59)
2-hr 0.826 0.999 1.24 1.42 1.66 1.84 2.02 2.20 1 2.44 2.63
(0.757-0.904) (0.914-1.09) (1.13-1.35) (1.29-1.55) (1.50-1.81) (1.66-2.00) (1.82-2.20) (1.97-2.40) (2.16-2.66) (2.30-2.87)
3-hr 0.585 0.705 0.879 1.01 1.20 1.34 1.49 1.65 1.86 2.02
(0.534-0.643) (0.645-0.776) (0.802-0.966) (0.923-1.11) (1.08-1.31) (1.21-1.47) (1.33-1.63) (1.46-1.80) (1.63-2.03) (1.75-2.21)
6-hr 0.352 0.424 0.529 0.612 0.726 0.817 0.910 1.01 1.14 1.25
(0.322-0.387) (0.389-0.466) (0.484-0.581) (0.559-0.670) (0.658-0.792) (0.736-0.889) (0.814-0.991)1 (0.892-1.10) (0.998-1.24) (1.08-1.36)
12-hr 0.207 0.249 0.312 0.363 0.434 0.491 0.551 0.614 0.703 0.775
(0.190-0.227) (0.229-0.274) (0.286-0.343) (0.331-0.398) (0.393-0.474) (0.442-0.535) (0.491-0.600) (0.541-0.668) (0.609-0.764) (0.663-0.843)
24-hr 0.123 0.148 0.186 0.216 0.258 0.292 0.327 0.365 0.417 0.459
(0.113-0.133) (0.137-0.160) (0.172-0.201) (0.199-0.234) (0.237-0.279) (0.267-0.316) (0.299-0.355) (0.331-0.395) (0.376-0.452) (0.411-0.499)
2-day 0.072 0.087 0.108 0.126 0.149 0.169 0.188 0.209 0.238 0.262
(0.067-0.078) (0.081-0.094) (0.100-0.118) (0.116-0.136) (0.137-0.162) (0.154-0.183) (0.172-0.205) (0.190-0.228) (0.215-0.260) (0.235-0.286)
3-day 0.051 0.061 0.076 0.088 0.104 0.117 0.131 0.145 0.165 0.182
(0.047-0.055) (0.057-0.066) (0.071-0.082) (0.081-0.095) (0.096-0.113) (0.108-0.127) (0.120-0.142) (0.132-0.158)I(0.150-0.180) (0.163-0.198)
4-day 0.041 0.049 0.060 0.069 0.082 0.092 0.102 0.113 0.129 0.141
(0.038-0.044) (0.045-0.052) (0.056-0.065) (0.064-0.075) (0.075-0.088) (0.084-0.099) (0.094-0.111) (0.104-0.123) (0.117-0.140) (0.128-0.154)
7-day 0.027 0.032 0.039 0.045 0.052 0.059 0.065 0.072 0.081 0.089
(0.025-0.029) (0.030-0.034) (0.036-0.042) (0.042-0.048) (0.049-0.056) (0.054-0.063) (0.060-0.070) (0.066-0.077) (0.074-0.088) (0.081-0.096)
10-day 0.021 0.026 0.031 0.035 0.040 0.045 0.049 0.054 0.060 0.066
(0.020-0.023) (0.024-0.027) (0.029-0.033) (0.033-0.037) (0.038-0.043) (0.042-0.048) (0.046-0.053) (0.050-0.058) (0.055-0.065) (0.060-0.071)
20-day 0.014 0.017 0.020 0.022 0.026 0.028 0.031 0.034 0.037 0.040
(0.013-0.015) (0.016-0.018) (0.019-0.021) (0.021-0.024) (0.024-0.027) (0.026-0.030) (0.029-0.033) (0.031-0.036) (0.034-0.040) (0.037-0.043)
30-day 0.012 0.014 0.016 0.018 0.020 0.022 0.024 0.025 0.028 0.030
(0.011-0.012) (0.013-0.015) (0.015-0.017) (0.017-0.019) (0.019-0.021) (0.021-0.023) (0.022-0.025) (0.024-0.027) (0.026-0.030) (0.027-0.032)
45-day 0.010 0.012 0.013 0.014 0.016 0.017 0.019 0.020 0.021 0.023
(0.009-0.010) (0.011-0.012) (0.013-0.014) (0.014-0.015) (0.015-0.017) (0.016-0.018) (0.018-0.020) (0.019-0.021) (0.020-0.023) (0.021-0.024)
60-day 0.009 0.010 0.012 0.013 0.014 0.015 0.016 0.017 0.018 1 0.019
(0.008-0.009) (0.010-0.011) (0.011-0.012) (0.012-0.013) (0.013-0.015) (0.014-0.016) (0.015-0.017) (0.016-0.018) (0.017-0.019),(0.018-0.020)
1 Precipitation frequency(PF)estimates in this table are based on frequency analysis of partial duration series(PDS).
Numbers in parenthesis are PF estimates at lower and upper bounds of the 90%confidence interval.The probability that precipitation frequency estimates(for a
given duration and average recurrence interval)will be greater than the upper bound(or less than the lower bound)is 5%.Estimates at upper bounds are not
checked against probable maximum precipitation(PMP)estimates and may be higher than currently valid PMP values.
Please refer to NOAA Atlas 14 document for more information.
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PF graphical

PDS-based intensity-duration-frequency (IDF) curves
Latitude: 34.9531°, Longitude: -80.7644°
100.000 , , , , , , , , , , ,
Average recurrence
interval
r 10.000 - (years)
,Z' _ 2
CA• 1.000 _ -
c — 10
G • - 25
•y 0.100 - — SO
'a
a 0.010 — 500
— 1000
0.001
c •c c •c c I- I_ I- >, >,> >, >, >, >, >,>,
N re1 tb -O -O -O -O "O"O
u1 O IA O 8 N N A 4 N O O O Ill O
ri ri M ri N M .1 ko
Duration
100.000
1-2 10.000 —
S --
• Duration
1.000 ---•t - — 5-min — 2-day
c — 10-min — 3-day
:i — 4-15-min — day
° :::
ro
• • - — 3-hr — 30-day
— 6-hr — 45-day
— 12-hr — 60-day
0.001 1 l — 24-hr
1 2 5 10 25 50 100 200 500 1000
Average recurrence interval (years)
NOAA Atlas 14,Volume 2,Version 3 Created(GMT): Wed Nov 9 14:57:18 2022
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Maps & aerials
Small scale terrain

Weighted Runoff Coefficient(C) Calculations

Pre-CN
Basin ID Cl Total Area 2.10 Basin ID C2 Total Area 0.30 Basin ID C2A Total Area 0.35
C Value C Value C Value
Type % C Weighted C Type % C Weighted C Type % C Weighted C
Grass 0.95 0.3 0.28 Grass 0.34 0.3 0.10 Grass 0.48 0.3 0.14
Road 0.05 0.95 0.05 Road 0.66 0.95 0.62 Road 0.52 0.95 0.50
Final C 0.33 Final C 0.73 Final C 0.64
Basin ID C3 Total Area 0.19 Basin ID C3A Total Area 0.56 Basin ID C3B Total Area 0.64
C Value C Value C Value
Type % C Weighted C Type % C Weighted C Type % C Weighted C
Grass 0.92 0.3 0.28 Grass 0.73 0.3 0.22 Grass 0.48 0.3 0.15
Road 0.08 0.95 0.08 Road 0.27 0.95 0.25 Road 0.52 0.95 0.49
Final C 0.35 Final C 0.47 Final C 0.64
Basin ID C4 Total Area 0.08 Basin ID C4A Total Area 0.17 Basin ID C4B Total Area 0.82
C Value C Value C Value
Type % C Weighted C Type % C Weighted C Type % C Weighted C
Grass 0.10 0.3 0.03 Grass 0.06 0.3 0.02 Grass 0.59 0.3 0.18
Road 0.90 0.95 0.86 Road 0.94 0.95 0.89 Road 0.41 0.95 0.39
Final C 0.89 Final C 0.91 Final C 0.57
Basin ID C4C Total Area 0.18 Basin ID C5 Total Area 0.19 Basin ID C5A Total Area 0.20
C Value C Value C Value
Type % C Weighted C Type % C Weighted C Type % C Weighted C
Grass 0.93 0.3 0.28 Grass 0.07 0.3 0.02 Grass 0.00 0.3 0.00
Road 0.07 0.95 0.06 Road 0.93 0.95 0.89 Road 1.00 0.95 0.95
Final C 0.34 Final C 0.91 Final C 0.95
Basin ID J1 Total Area 0.53 Basin ID J2 Total Area 0.12 Basin ID J2A Total Area 0.11
C Value C Value C Value
Type % C Weighted C Type % C Weighted C Type % C Weighted C
Grass 0.70 0.3 0.21 Grass 0.00 0.3 0.00 Grass 0.08 0.3 0.02
Road 0.30 0.95 0.28 Road 1.00 0.95 0.95 Road 0.92 0.95 0.87
Final C 0.49 Final C 0.95 Final C 0.90
Basin ID K1 Total Area 0.14
C Value
Type % C Weighted C
Grass 0.11 0.3 0.03
Road_ 0.89 _ 0.95 0.85
Final C 0.88

Post-CN
Basin ID Cl Total Area 2.12 Basin ID C2 Total Area 0.30 Basin ID C2A Total Area 0.35
C Value C Value C Value
Type % C Weighted C Type % C Weighted C Type % C Weighted C
Grass 0.85 0.3 0.26 Grass 0.34 0.3 0.10 Grass 0.48 0.3 0.14
Road 0.15 0.95 0.14 Road 0.66 0.95 0.62 Road 0.52 0.95 0.50
Final C 0.40 Final C 0.73 Final C 0.64
Basin ID C3 Total Area 0.09 Basin ID C3A Total Area 0.51 Basin ID C3B Total Area 0.55
C Value C Value C Value
Type % C Weighted C Type % C Weighted C Type % C Weighted C
Grass 1.00 0.3 0.30 Grass 0.24 0.3 0.07 Grass 0.42 0.3 0.13
Road 0.00 0.95 0.00 Road 0.76 0.95 0.73 Road 0.58 0.95 0.55
Final C 0.30 Final C 0.80 Final C 0.68
Basin ID C3C Total Area 0.16 Basin ID C3D Total Area 0.00
C Value C Value
Type % C Weighted C Type % C Weighted C
Grass 0.74 0.3 0.22 Grass 0.00 0.3 0.00
Road 0.26 0.95 0.25 Road 0.00 0.95 0.00
Final C 0.47 Final C 0.00
Basin ID C4 Total Area 0.00 Basin ID C4A Total Area 0.89 Basin ID C4B Total Area 0.37
C Value C Value C Value
Type % C Weighted C Type % C Weighted C Type % C Weighted C
Grass 0.00 0.3 0.00 Grass 0.42 0.3 0.12 Grass 0.96 0.3 0.29
Road 0.00 0.95 0.00 Road 0.58 0.95 0.56 Road 0.04 0.95 0.04
Final C 0.00 Final C 0.68 Final C 0.32
Basin ID CRN Total Area 0.12 Basin ID C5 Total Area 0.13 Basin ID CRS Total Area 0.12
C Value C Value C Value
Type % C Weighted C Type % C Weighted C Type % C Weighted C
Grass 0.00 0.3 0.00 Grass 0.14 0.3 0.04 Grass 0.00 0.3 0.00
Road 1.00 0.95 0.95 Road 0.86 0.95 0.82 Road 1.00 0.95 0.95
Final C 0.95 Final C 0.86 Final C 0.95
Basin ID JI Total Area 0.53 Basin ID J2 Total Area 0.10 Basin ID J2A Total Area 0.11
C Value C Value C Value
Type % C Weighted C Type % C Weighted C Type % C Weighted C
Grass 0.73 0.3 0.22 Grass 0.00 0.3 0.00 Grass 0.08 0.3 0.02
Road 0.27 0.95 0.25 Road 1.00 0.95 0.95 Road 0.92 0.95 0.87
Final C 0.47 Final C 0.95 Final C 0.90
Basin ID Kl Total Area 0.15
C Value
Type % C Weighted C
Grass 0.09 0.3 0.03
Road 0.91 _ 0.95 0.87
Final C 0.89

Stormwater Studios Profiles& Tables

Plan View Twelve Mile Creek WRF 9.0 MGD Expansion
Stormwater Studio 2022 v 3.0.0.29 07-24-2023
CB
3CP. I, CB 11 8 12.�
MH-C3D
�r
YI-C3
..:Ic1
A - AO
5 y i "'117 48
YI-CCB-C2 C4A
MH-C4
CB-C2A
N
CB-05
Project File:System CCanopy Mod.sws

Plan View Twelve Mile Creek WRF 9.0 MGD Expansion
Stormwater Studio 2022 v 3.0.0.29 01-12-2023
MH-J3
•
ti
CB-J2
4
r
CB- A
41114,.
CB-J1
ti
Project File:Storm Drain at IPS.sws

P rof i le View Project Name:Twelve Mile Creek WRF 9.0 MGD Expansion
Stormwater Studio 2022 v 3.0.0.29 07-25-2023
System C: Profile 1
Elev(It)
560.00 560.00
>- J 6 o�5 S 6 c -5 s Og
555.00 il s itrA2 tv as -`os •{-'.5S-°�r•� RN° :g; 555.00
550.00 \ • 550.00
545.00 545.00
!gamEa
'''MN'" 85U.15'Q2OM5
540.00 3 f f 3% 540.00
A V' -S 2 52u"
„L.15'Q2."
cad 24.Q 2.55%
535.00 535.00
12713-2e5h2.5755
530.00 530.00
525.00 525.00
0 30 60 90 120 150 180 210 240 270 300 330 360 390 420
Reach(0)
m Grad Surface HGL EGL
Project File:System CCanopy Mod.sws

P rofi le View Project Name:Twelve Mile Creek WRF 9.0 MGD Expansion
Stormwater Studio 2022 v 3.0.0.29 07-25-2023
System C: Profile 2
Elev(ft)
552.00 552.00
NI'ifs . ..A.
550.00 g5.5s544-�l o.ARi - 550.00
m-E
g'cE' 'c 'c 'c==ww � Tn� giW
548.00 - 548.00
546.00 546.00
544.00 ^ 544.00
542.00
542.00
540.00 540.00
0 5 10 15 20 25
Gmd surfaceHGL EGL Reach(ft)
Project File:System CCanopy Mod.sws

P rofi le View Project Name:Twelve Mile Creek WRF 9.0 MGD Expansion
Stormwater Studio 2022 v 3.0.0.29 07-25-2023
System C: Profile 3
Elev(fl)
563.00 563.00
559.00 - 559.00
o m
a Y
_
oh 5 2 Os5 v o
V 5
555-00 p c c t> 0<< L,n g"+t 0 `,j c o$ci3O.e 0r' c 555.00
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551.00
547.00 —. 547.00
di
543.00 i — 543.00
I7Lf-15'312.01%
37Lf-15"@ 1.17%
-12L1-15"61.43%
539.00 - - 539.00
535.00 535.00
0 10 20 30 40 50 60 70
Gmd Surface HGL EGL Reach(R)
Project File:System CCanopy Mod.sws

P rofi le View Project Name:Twelve Mile Creek WRF 9.0 MGD Expansion
Stormwater Studio 2022 v 3.0.0.29 07-25-2023
System C: Profile 4
Elev(ft)
556.00 556.00
554.00 • 554.00
552.00 552.00
m c O c U O s
550.00 3tJ1 a - 550.00
0
i7 W W m E
c c c
548.00 - 548.00
:::
— 546.00
544.00
24Lf-15'@ 1.00%
542.00 542.00
540.00 540.00
0 10 20 30
Gmd Surface HGL EGL Reach(tt)
Project File:System CCanopy Mod.sws

Profile View Project Name:Twelve Mile Creek WRF 9.0 MGD Expansion
Stormwater Studio 2022 v 3.0.0.29 07-25-2023
System C: Profile 5
Elev(ft)
559.00 I 559.00
557.00 557.00
555.00 - 555.00
553.00 a V .5« 553.00
V < < «
551.00 042co4 '°1- N1RI Im ;°n „' A -°r.i 551.00
$W-wx aW-Wxlam aWWR555
549.00 HIMIIIIMIU1111111"
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i1W toa 0500, 549.00_
�547.00 547.00
545.00 545.00
543.00543.00
Ir1
1.02% 77Ll-75"@ O.B2%
541.00 — 541.00
539.00 539.00
537.00 537.00
535.00 535.00
0 10 20 30 40
Gmd Surface HGL • EGL Reach(II)
Project File:System CCanopy Mod.sws

P rof i le View Project Name:Twelve Mile Creek WRF 9.0 MGD Expansion
Stormwater Studio 2022 v 3.0.0.29 05-15-2023
System J: Profile 1
Elev(ft)
530.00 530.00
525.00 525.00
N gg
520.00 Q O < <.. c �' v ".m8- =.5 c 520.00
S m olopo�pa��0 c' e�m N pI,,,s., y♦ N N§i N pC NN T w y„j Rp pRO P,N
V99go"'�e yd g= sidd +n z gxxn
515.00 $em --�& — 515.00
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510.00 . 88a�- — 510.00
.Woc
a�6-='I il mommiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii"5"556665511
g l
5u.i5^62.77%
505.00 - i . . 505.00
mi.is,Teo3w
500.00 — 500.00
495.00 495.00
0 20 40 60 80 100 120 140 160 180
Gmd Surface HGL EGL Reach(It)
Project File:Storm Drain at IPS.sws

P rofi le View Project Name:Twelve Mile Creek WRF 9.0 MGD Expansion
Stormwater Studio 2022 v 3.0.0.29 05-15-2023
System J: Profile 2
Elev(ft)
519.00 519.00
517.00 - 517.00
515.00 •
A- 515.00
N
C 5 5 r 7
0 8 a M p V O'".s
� N!`0 O
vNi
513.00 $u mmm ^wNN g4 n oirgg2r,'' - 513.00
abgggdddd
i m E i w TA K�2
511.00 511.00
::.:
:::::
•
O2LI.15!0!9%
505.00 505.00
503.00 503.00
0 10 20 30 40 50 60
Grid Surface HGL EGL Reach(ft)
Project File:Storm Drain at IPS.sws

P rofi le View Project Name:Twelve Mile Creek WRF 9.0 MGD Expansion
Stormwater Studio 2022 v 3.0.0.29 05-15-2023
System K
Elev(ft)
522.00 522.00
520.00 520.00
518.00 - - 518.00
516.00 - • 516.00
514.00
s
o„ 514.00
V s e `e E
•p.2 N.6 g rn
512.00 aai,,;??8£ 512.00
Mi25xx,uw
510.00 510.00
o 8f
o
508-00 �-20 508-00
m c $Li W in�75z _. - --
506-00 506-00
491_1-15'®4.78%
504.00 504.00
502.00 502.00
0 5 10 15 20 25 30 35 40 45 50
Gma Surface HGL EGL Reach(ft)
Project File:Storm Drain at IPS.sws

Twelve Mile Creek WRF 9.0 MGD Expansion
Storm Sewer Calculations-System C
10-Year Storm Event Exported From Stormwater Studio
Length Drainage Area Runoff C x Cf x A Tc Intensity Runoff Add'I Total Pipe Ave Line Line Invert Elev HGL Elev Surface Ely Line
Line ID Incr Total Coeff Incr Total Inlet System Incr Total Incr Total Flow Flow Capac. Vel Size Slope Up Dn Up Dn Up Dn No.
(ft) (ac) (ac) (C) (min) (min) (in/hr) (in/hr) (cfs) (cfs) (cfs) (cfs) (do) (TVs) (in) (%) (ft) (ft) (ft) (ft) (ft) (ft)
YI-C1 to CB-C2 86.44 2.12 2.12 0.4 0.85 0.85 5 5 7.57 7.57 6.42 6.42 0 6.42 9.14 5.23 15 2 543.42 541.69 546.6 545.74 547.35 547.19 5
CB-C2A to CB-C2 21.56 0.35 0.35 0.64 0.22 0.22 5 5 7.57 7.57 1.7 1.7 0 1.7 10.95 1.38 15 2.88 542.31 541.69 546.15 546.14 547.21 547.19 6
CB-C2 to YI-C3 53.41 0.3 2.77 0.73 0.22 1.29 5 5.2 7.57 7.51 1.66 9.7 0 9.7 13.23 9.9 15 4.23 541.69 539.43 544.62 543.42 547.19 547 4
CB-C3B to MH-C3D 11.85 0.55 0.55 0.68 0.37 0.37 5 5 7.57 7.57 2.83 2.83 0 2.83 7.74 2.65 15 1.43 544.04 543.87 544.98 544.99 547.7 547.7 12
MH-C3D to CB-C3A 17.4 0 0.55 0 0 0.37 5 5 0 7.56 0 2.83 0 2.83 9.16 2.31 15 2.01 543.38 543.03 544.86 544.82 547.7 547.17 8
YI-C3C to CB-C3A 24 0.16 0.16 0.47 0.08 0.08 5 5 7.57 7.57 0.57 0.57 0 0.57 6.46 0.46 15 1 543.27 543.03 544.91 544.9 547 547.17 11
CB-C3A to YI-C3 37.14 0.51 1.22 0.8 0.41 0.86 5 5.1 7.57 7.53 3.09 6.46 0 6.46 9.05 6.65 15 1.97 543.03 542.2 544.05 543.15 547.17 547 7
YI-C3 to YI-C4 54.71 0.087 4.77 0.3 0.03 2.17 5 5.3 7.57 4.49 0.2 16.28 0 16.28 16.87 9.21 18 2.58 539.43 53/8.25 541.37 540.27 547 546.67 3
CB-C4B to MH-C4A 10.93 0.37 0.37 0.32 0.12 0.12 5 5 7.57 7.57 0.9 0.9 0 0.9 6.18 0.76 15 0.92 542.82 542.72 543.94 543.94 546.99 546.94 10
MH-C4A to YI-C4 51.57 0.56 0.93 0.58 0.32 0.44 5 5.1 7.57 7.56 2.46 3.35 0 3.35 6.52 4.69 15 1.02 542.72 542.5 543.45 543.18 546.94 546.67 9
YI-C4 to CB-05 97.6 0 5 0 0 2.62 0 5.3 0 7.46 0 19.53 0.86 20.39 36.13 7.03 24 2.55 537.75 535.26 539.35 537.98 546.67 545.5 2
CB-05 to HW-C6 126.9 0.13 5.14 0.86 0.11 2.73 5 5.5 7.57 7.42 0.85 20.24 0.86 21.96 36.25 9.48 24 2.57 535.26 532 536.92 533.21 545.5 533.25 1

Twelve Mile Creek WRF 9.0 MGD Expansion
Storm Sewer Calculations-System J
10-Year Storm Event Exported From Stormwater Studio
Length Drainage Area Runoff C x Cf x A Tc Intensity Runoff Add'I Total Pipe Ave Line Line Invert Elev HGL Elev Surface Ely Line
Line ID Incr Total Coeff Incr Total Inlet System Incr Total Incr Total Flow Flow Capac. Vel Size Slope Up Dn Up Dn Up Dn No.
(ft) (ac) (ac) (C) (min) (min) (in/hr) (in/hr) (cfs) (cfs) (cfs) (cfs) (cfs) (TVs) (in) (%( (ft) (ft) (ft) (ft) (ft) (ft)
CBJ1 to CB-J2 74.94 0.526 0.526 0.48 0.25 0.25 5 5 7.57 7.57 1.91 1.91 0 1.91 9.73 2.63 15 2.27 507.78 506.08 508.33 507.24 510.78 510.21 3
CB-J2A to CB-J2 52.32 0.109 0.109 0.9 0.1 0.1 5 5 7.57 7.57 0.74 0.74 0 0.74 2.82 1.94 15 0.19 507.02 506.92 507.46 507.36 509.78 510.21 4
CB-J2 to MH-J3 26.43 0.098 0.733 0.95 0.09 0.44 5 5.4 7.57 7.42 0.71 3.29 0 3.29 11.3 5.49 15 3.06 506 505.19 506.73 505.73 510.21 508.19 2
MH-J3 to FES-J4 61.53 0 0.733 0 0 0.44 0 5.5 0 7.4 0 3.28 0 3.28 15.86 3.56 15 6.03 503.29 499.58 504.02 500.83 508.19 499.58 1

Twelve Mile Creek WRF 9.0 MGD Expansion
Storm Sewer Calculations-System K
10-Year Storm Event Exported From Stormwater Studio
Length Drainage Area Runoff C x Cf x A Tc Intensity Runoff Add'I Total Pipe Ave Line Line Invert Elev HGL Elev Surface Ely Line
Line ID Incr Total Coeff Incr Total Inlet System Incr Total Incr Total Flow Flow Capac. Vel Size Slope Up Dn Up Dn Up Dn No.
(ft) (ac) (ac) (C) (min) (min) (inthr) (in/hr) (cfs) (cfs) (cfs) (cfs) (cfs) (ft/s) (in) (%) (ft) (ft) (ft) (ft) (ft) (ft)
CB-K1 to FES-K2 I 49 I 0.257 10 257 I 0.89 I 0 23 I 0.23 I 5 I 5 I 7.57 l 7.57 I 1 73 I 1.73 I 0 I 1.73 I 14.11 I 2 47 I 15 I 4.78 I 506.24 I 503.9 I 506.77 I 505.15 I 508.99 l 503.9 I 5

Twelve Mile Creek WRF 9.0 MGD Expansion
Storm Inlet Calculations
10-Year Storm Event Exported From Stormwater Studio
System C
Q Q Q Q Spread Spread Depth Depth Efficiency
Inlet ID Inlet Type Catchment +Carryover -Captured =Bypassed Gutter Inlet Gutter Inlet Line No.
1 (cfs) 1 (cfs) 1 (cfs) (cfs) 1 (ft) , (ft) , (ft) , (ft)
YI-C1 Drop Grate in Sag 6.4 0.0 6.4 0.0 43.5 43.5 0.4 0.4 ---- 5
CB-C2A Combination on Grade 1.7 0.0 1.7 0.0 6.1 6.1 0.2 0.2 100 6
CB-C2 Combination on Grade 1.7 0.0 1.7 0.0 6.1 6.1 0.2 0.2 100 4
YI-C3 Drop Grate in Sag 0.2 1.3 1.5 0.0 17.7 17.7 0.2 1.6 ---- 3
CB-C3A Combination on Grade 3.1 0.8 2.6 1.3 8.8 8.8 0.2 0.2 66 7
CB-C3B Combindation on Grade 2.8 0.0 2.1 0.8 7.7 7.7 0.2 0.2 73 12
YI-C3C Drop Grate in Sag 0.6 0.0 0.6 0.0 10.3 10.3 0.1 0.1 ---- 11
MH-C3D Manhole 0.0 0.8 0.0 0.8 - - - - ---- 8
MH-C4 Manhole 0.9 0.6 0.0 1.5 - - - - ---- 2
CB-C4A Combination on Grade 2.5 0.0 1.9 0.6 7.3 7.3 0.2 0.2 76 9
CB-C4B Drop Grate in Sag 0.9 0.0 0.9 0.0 13.2 13.2 0.1 0.1 ---- 10
CB-05 Combindation on Grade 1.7 1.5 2.4 0.8 8.1 8.1 0.2 0.2 76 1
System J
Q Q Q Q Spread Spread Depth Depth Efficiency
Inlet ID Inlet Type Catchment +Carryover -Captured =Bypassed Gutter Inlet Gutter Inlet Line No.
(cfs) (cfs) (cfs) (cfs) (ft) (ft) (ft) (ft)
CB-J1 Combination on Grade 1.91 0 1.56 0.35 6.45 6.45 0.19 0.19 82 3
CB-J2A Combination on Grade 0.74 0 0.74 0 4 4 0.14 0.14 100 4
CB-J2 Combination on Grade 0.71 0.35 1.06 0 4.85 4.85 0.16 0.16 100 2
MH-J3 Manhole 0 0 0 0 - - - - 1
System K
Q Q Q Q Spread Spread Depth Depth
Efficiency
Inlet ID Inlet Type Catchment +Carryover -Captured =Bypassed Gutter Inlet Gutter Inlet Line No.
(cfs) (cfs) (cfs) (cfs) (ft) (ft) (ft) (ft)
CB-K1 I Combination on Grade l 1.73 l 0 I 1.73 I 0 I 6.2 I 6.2 I 0.18 I 0.18 I 100 I 5

Riprap Outlet Protection Calculations

DESIGN OF RIPRAP OUTLET PROTECTION
User Input Data
Calculated Value
Reference Data
Designed By: QKT Date: 7/25/2023
Checked By: Date:
Company: Hazen&Sawyer
Project Name: Twelve Mile Creek WRF 9.0 MGD Expansion
Project No.: 30831-061
Site Location(City/Town) Waxhaw
Culvert Id. C6
Total Drainage Area(acres) 5.14
Step 1. Determine the tailwater depth from channel characteristics below the
pipe outlet for the design capacity of the pipe. If the tailwater depth is less
than half the outlet pipe diameter.it is classified minimum tailwater condition.
If it is greater than half the pipe diameter.it is classified maximum condition.
Pipes that outlet onto wide flat areas with no defined channel are assumed
to have a minimum tailwater condition unless reliable flood stage elevations
show otherwise.
Outlet pipe diameter,Do(in.) 24
Tailwater depth(in.) 0
Minimum/Maximum tailwater? Min TW(Fig.8.06a)
Discharge(cfs) 36.48
Velocity(ft./s) 11.61
Step 2. Based on the tailwater conditions determined in step 1.enter Figure
8.06a or Figure 8.06b.and determine d50 riprap size and minimum apron length
(Le). The d50 size is the median stone size in a well-graded riprap apron.
Step 3. Determine apron width at the pipe outlet.the apron shape.and the
apron width at the outlet end from the same figure used in Step 2.
Minimum TW Maximum TW
Figure 8.06a Figure 8.06b
Riprap d5o,(It.) 0.5 0.5
Minimum apron length,La(ft.) 13 10
Apron width at pipe outlet(ft.) 6 6
Apron shape
Apron width at outlet end(ft.) 15 6
Step 4. Determine the maximum stone diameter:
d,,,,,,=1.5 x d5o
Minimum TW Maximum TW
Max Stone Diameter,dmax(ft.) 0.75 0.75
Step 5. Determine the apron thicknes
Apron thickne s=1.5 x din,
Minimum TW Maximum TW
Apron Thickness(ft.) 1.125 1.125
Step 6. Fit the riprap apron to the site by making it level for the minimum
length. L,, from Figure 8.06a or Figure 8.06b. Extend the apron farther
downstream and along channel banks until stability is assured. Keep the
apron as straight as possible and align it with the flow of the receiving stream.
Make any necessary alignment bends near the pipe outlet so that the entrance
into the receiving stream is straight.
Some locations may require lining of the entire channel cross section to assure
stability.
It may be necessary to increase the size of riprap where protection of the
channel side slopes is necessary(Appendix 8.05). Where overfills exist at
pipe outlets or flows are excessive,a plunge pool should be considered,see
page 8.06.8.

DESIGN OF RIPRAP OUTLET PROTECTION
User Input Data
Calculated Value
Reference Data
Designed By: QKT Date: 7/25/2023
Checked By: Date:
Company: Hazen&Sawyer
Project Name: Twelve Mile Creek WRF 9.0 MGD Expansion
Project No.: 30831-061
Site Location(City/Town) Waxhaw
Culvert Id. J4
Total Drainage Area(acres) 0.733
Step 1. Determine the tailwater depth from channel characteristics below the
pipe outlet for the design capacity of the pipe. If the tailwater depth is less
than half the outlet pipe diameter.it is classified minimum tailwater condition.
If it is greater than half the pipe diameter.it is classified maximum condition.
Pipes that outlet onto wide flat areas with no defined channel are assumed
to have a minimum tailwater condition unless reliable flood stage elevations
show otherwise.
Outlet pipe diameter,Do(in.) 15
Tailwater depth(in.) 0
Minimum/Maximum tailwater? Min TW(Fig.8.06a)
Discharge(cfs) 15.86
Velocity(ft./s) 12.93
Step 2. Based on the tailwater conditions determined in step 1.enter Figure
8.06a or Figure 8.06b.and determine d50 riprap size and minimum apron length
(Le). The d50 size is the median stone size in a well-graded riprap apron.
Step 3. Determine apron width at the pipe outlet.the apron shape.and the
apron width at the outlet end from the same figure used in Step 2.
Minimum TW Maximum TW
Figure 8.06a Figure 8.06b
Riprap d5o,(ft.) 0.65 0.5
Minimum apron length,La(ft.) 14 34
Apron width at pipe outlet(ft.) 3.75 3.75
Apron shape
Apron width at outlet end(ft.) 15.25 14.85
Step 4. Determine the maximum stone diameter:
1.5xd5o
Minimum TW Maximum TW
Max Stone Diameter,dmax(ft.) 0.975 0.75
Step 5. Determine the apron thickness
Apron thickness=1.5 x din„
Minimum TW Maximum TW
Apron Thickness(ft.) 1.4625 1.125
Step 6. Fit the riprap apron to the site by making it level for the minimum
length. L,, from Figure 8.06a or Figure 8.06b. Extend the apron farther
downstream and along channel banks until stability is assured. Keep the
apron as straight as possible and align it with the flow of the receiving stream.
Make any necessary alignment bends near the pipe outlet so that the entrance
into the receiving stream is straight.
Some locations may require lining of the entire channel cross section to assure
stability.
It may be necessary to increase the size of riprap where protection of the
channel side slopes is necessary(Appendix 8.05). Where overfills exist at
pipe outlets or flows are excessive,a plunge pool should be considered,see
page 8.06.8.

DESIGN OF RIPRAP OUTLET PROTECTION
User Input Data
Calculated Value
Reference Data
Designed By: QKT Date: 7/25/2023
Checked By: Date:
Company: Hazen&Sawyer
Project Name: Twelve Mile Creek WRF 9.0 MGD Expansion
Project No.: 30831-061
Site Location(City/Town) Waxhaw
Culvert Id. K2
Total Drainage Area(acres) 0.257
Step 1. Determine the tailwater depth from channel characteristics below the
pipe outlet for the design capacity of the pipe. If the tailwater depth is less
than half the outlet pipe diameter.it is classified minimum tailwater condition.
If it is greater than half the pipe diameter.it is classified maximum condition.
Pipes that outlet onto wide flat areas with no defined channel are assumed
to have a minimum tailwater condition unless reliable flood stage elevations
show otherwise.
Outlet pipe diameter,Do(in.) 15
Tailwater depth(in.) 0
Minimum/Maximum tailwater? Min TW(Fig.8.06a)
Discharge(cfs) 14.15
Velocity(ft./s) 11.53
Step 2. Based on the tailwater conditions determined in step 1.enter Figure
8.06a or Figure 8.06b.and determine d50 riprap size and minimum apron length
(Le). The d50 size is the median stone size in a well-graded riprap apron.
Step 3. Determine apron width at the pipe outlet.the apron shape.and the
apron width at the outlet end from the same figure used in Step 2.
Minimum TW Maximum TW
Figure 8.06a Figure 8.06b
Riprap d5o,(It.) 0.5 0.5
Minimum apron length,La(ft.) 14 19
Apron width at pipe outlet(ft.) 3.75 3.75
Apron shape
Apron width at outlet end(ft.) 15.25 8.85
Step 4. Determine the maximum stone diameter:
d , =1.5xd5o
Minimum TW Maximum TW
Max Stone Diameter,dmax(ft.) 0.75 0.75
Step 5. Determine the apron thicknes
Apron thickne s=1.5 x din„
Minimum TW Maximum TW
Apron Thickness(ft.) 1.125 1.125
Step 6. Fit the riprap apron to the site by making it level for the minimum
length. L, from Figure 8.06a or Figure 8.06b. Extend the apron farther
downstream and along channel banks until stability is assured. Keep the
apron as straight as possible and align it with the flow of the receiving stream.
Make any necessary alignment bends near the pipe outlet so that the entrance
into the receiving stream is straight.
Some locations may require lining of the entire channel cross section to assure
stability.
It may be necessary to increase the size of riprap where protection of the
channel side slopes is necessary(Appendix 8.05). Where overfills exist at
pipe outlets or flows are excessive,a plunge pool should be considered,see
page 8.06.8.

Figure 8.06a: Design of outlet protection from a round pipe flowing full, minimum
tailwater condition (Tw<0.5 diameter)
Outlet w . Do * La Eeturn to Main Worksheet
pipe t Ildl
diameter Mot
il.+re r 0.5D0
xp
y A
20 r •
tom., r
........... . .. lirrdi
NO IN
0al, } 't i i' e
I II
... i ..::. • .. :: : .v •'.rlll..�l � • " it it 1 II ii i - C
p
`G� +��-�rW ���� nil .11irlr i: 1
%iiP2P.Aw illrlu.i
3 �s
v-5 �rrll�„ I.
3 5 10 20 50 100 200 500 1000
Discharge(tt3/sec)
Curves may not be extrapolated.
Figure 8.06a Design of outlet protection protection from a round pipe flowing full,minimum laitwater condition(T.<0.5 diameter).
Rev.1!93 8.063

Figure 8.06b: Design of outlet protection from a round pipe flowing full, maximum
tailwater condition (Tw>=0.5 diameter)
300 ,
1�
Outlet f 120 T - Return to Main Worksheet
pipe l --_ , I i i
diameter(WI. La 110 .: ... _ ;... ..i :: 'r,
. :.}:.:. .. .� i.i - ii�
100 _ r �wl ' ii
0 , I i
�, 6 r.. OR
c� All II
1 I 4,
/ _ w
In,' r ,rlif in i
• / l
/ 1 P dralf.
- ,, i
I
to 1:. AIh M . Af
V j ritly► v;
-- Ili li 0
3 5 10 20 50 100 200 500 1000
Discharge(ft3/sec)
Curves may not be extrapolated.
Figure 8.06b Design of outlet protection from a round pipe flowing full.maximum tailwater condition(T.?0.5 6ameter)
&OfA Rer.1:93

PIPE FLOW CALCULATIONS
Pipe Pipe Pipe Manning's Full-Flow Full Flow Full-Flow Flow Full-Flow Design-Flow
Location Diamater Slope n Area Wetted Perim. Hyd. Radius Capacity Velocity Velocity
(ft) (ft/ft) I (sq ft) (ft) (ft) (cfs) (fps) (fps)
FES C6 2 0.026 0.013 3.14 6.28 0.50 36.48 11.61 9.48
FES J4 1.25 0.06 0.013 1.23 3.93 0.31 15.86 12.93 3.56
FES K4 1.25 0.048 0.013 1.23 3.93 0.31 14.15 11.53 2.47
Note:Design flow was determined using the Stormwater Studio model, based on the 10-year design storm. Full
flow was calculated using the Manning's equation. The larger value between these two calculations were then
utilized to size the Riprap aprons for non-erosive discharge at the stormwater outlets.