NC0021849_Application (ATC)_20240201 (10)

DocuSign Envelope ID: 9BCC84A1-38A6-466F-A3F6-832034E1194A
W"thersRavenet
Our People. Your Success.
Hertford WWTP Design Calculations
Town of Hertford
Collection System Rehab (WWTP)
114 W. Grubb Street, Hertford, NC 27944
Prepared For:
Town of Hertford
114 W. Grubb Street, PO Box 32
Hertford, NC 27944
ATTN: Janice McKenzie Cole, Town Manager & Leonard McBryde, Director of Utilities
Prepared By:
WithersRavenel
115 MacKenan Drive
Cary, NC 27511
Phone: [phone]
License #: F-1479
December 12, 2023
WithersRavenel Project Number: 09220405.01
DWI Project Number: VUR-W-ARP-0068 & CS370526-05
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Carolyn Hawkins, PE
Engineer of Record

Project: Collection System Rehab (WWTP)
Project #: 09220405.01
Design: WWTP Design Calculations
Date: 12/12/2023
Page 1 of 2
Current Population
2,194
Computed Peaking Factor
3.15
Average Flow
700,000
gpd
Average Flow
486.11
gpm
Peak hourly Flow
1,529
gpm
Peak Daily Flow
2,201,623
igpd
Manual Bar Screen
Invert El =
14
ft
Screen Width =
1.67
ft
Bar Spacing =
1
in
Bar Thkness =
0.375
in
k =
1.5
Blind =
0.5
HGL-Parshall
14.72
1
14.98
15.56
Flume(ft)
Q (mgd) =
0.70
1.10
2.20
Depth ds (ft) =
0.72
0.98
1.56
V us (fps) =
0.90
1.04
1.31
V bars (fps) =
2.46
2.86
3.60
H L (ft) =
1 0.121
0.171
0.26
HGL Upstream
14.85
15.15
15.82
of Screens
At a peak flow of 2.2 MGD, freeboard is 1.2ft for the manual bar screen.

Project: Collection System Rehab (WWTP)
Project #: 09220405.01
Design: WWTP Design Calculations
Date: 12/12/2023
Page 2 of 2
Current Population
2,194
Computed Peaking Factor
3.15
Average Flow
700,000
gpd
Average Flow
486.11
gpm
Peak hourly Flow
1,529
gpm
Peak Daily Flow
2,201,623
Igpd
At a peak flow of 2.2 MGD and an HGL of 15.56', the proposed step screens will have up to 5.5"
of headloss to maintain 1 ft of freeboard. The headloss provided by one of the manufacturers
was 0.62". Please see attached specification for the proposed screens.
The proposed grit system can handle up to 2.5 MGD, which is larger than the peak flow of 2.2
MGD. The capacity of the system was provided by the manufacturer. Please see attached
specification for the proposed grit system.