SW3220305_Design Calculations_20220325

Brown-,,- Caldwell
SUBJECT: Stormwater Network Sizing
SYSTEM:O
CLIENT: Water and Sewer Authority of Cabarrus County
PROJECT NAME: Rocky River Regional Wastewater Treatment Plant Expansion
PROJECT
NUMBER: 156673
DISCIPLINE: Civil
CREATED BY: Daniel Wright
CHECKED BY: Dave Varjabedian
DATE: 2/9/22
CURRENT
REVISION: 0
PPLICATION SOFTWARE USED
QC Checker Section Sign -Off: -
Software Name
REFERENCES
-QC Checker Section Sign -Off: -
D. Version/Date
CALCULATION BASIS AND ASSUMPTIONS
QC Checker Section Sign -Off: -
C Factors
Impervious Area 0.95
Pervious Area -Gras; 0.3
Pervious Area -Soil 0.6
Basin Areas and C Factors
Impervious
Basin #
Area
x C Impery
+ Pervious area
x C' Pery
_ Total Area - Composite'C
ENDWALL - 1
0.08
0.95
3.81
0.3
3.89 0.31
STD 1 - DI
0.036
0.95
0.374
0.3
0.41 0.36
STD 3 - DI
0.002
0.95
0.288
0.3
0.29 0.30
TRENCH DRAIN
0.21
0.95
0.79
0.3
1.00 0.44
TOC (min) 5.00 Assumed
Intensity (10-yr) (in/hr) 7.32
Basin Flow (Q=CIA)
Basin (cfs)
ENDWALL - 1
8.92
STD 1 - DI
1.07
STD 3-DI
0.65
TRENCH DRAIN
3.20
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•••.K Y D Ev..••
02/147ZZ-9:54 AM
0.46 8/3 1/2 Mannings equation for pipe flow flowing full
Q= - �D� s 9 q p�p 9
n
D = Qn 3/8 Mannings Equation solved for diameter
0.46s 1/2
Actual flow to basin structure (additive from upstream structures. See drainaae plans for structures
Basin #
Q (cts)
D (ft) D (in)
Use D (in)
ENDWALL - 2
9.99
1.58 18.95
30
ENDWALL - 1
8.92
1.51 18.16
24
STD 1 - DI
1.07
0.68 8.20
15
STD 3 - DI
3.84
1.10 13.24
24
TRENCH DRAIN
3.20
6" width
n
0.011
Concrete Mannings n
s (ft/ft)
0.005
Minimum slope to be used (min. value gives largest diameter)
24" pipe is existing
conclusion note
Provided diameters are all larger than the required diameter that was calculated. The trench drain dimension is sized at a 6" width due to suppliers
recommending 6" wide drains for flows up to 4 cfs and the actual flow is 3.20 cfs.
2/10/2022 Page 1 of 1
10:41 AM 8x11 Portrait Calculation STRM-Pipe-Sizing