20100425 Ver 2_Stormwater Info_20101027

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LITTLE & LITTLE
27 October 2010
Received by:
Date:
TRANSMITTAL
TO: Mr. Ian McMillan
DENR DWQ
W
Wetlands and Stormwater Branch, t`5
401 Oversight/Express Permitting Unit +5
2321 Crabtree Blvd. OAT 2 7 2010
Raleigh, NC 27604
DENR - WER OU"
FROM: Amy Mackintosh DS MDSTMW- ATER BWJ01
SUBJECT: DWQ # 10-0425 Ver. 2, Wake County
Stream Restoration Project - N4 Cluster, NCSU Centennial Campus
We are sending to you via: Courier
Quantity Date Description
1 10-27-2010 Cover letter
2 sets 10-22-2010 Stream Restoration Plans - Sheets L1-L-9 -
full size
3 sets 10-22-2010 Stream Restoration Plans - Sheets L1-L-9 -
11x17
3 sets 10-21-2010 Level Spreader Supplementary Work Sheet
and calculations
1 CD with pdfs of plans
For permitting
Remarks:
The O&M agreement will follow shortly. We are awaiting the University's signature.
Copy (transmittal only, via email):
Jamie Shern, US Army Corps of Engineers
Michael Harwood c/o Rachel Miller, NCSU Project Manager
George Retschle, Ballentine Associates
L&L Project Number (ncssr.01)
Landscape Architecture / Planning PO Box 1448 Raleigh, North Carolina 27602 9191821-5645 Fax [phone]
LITTLE & LITTLE
27 October 2010
DWQ # 10-0425, Ver. 2
Wake County
Mr. Ian McMillan
NC DENR DWQ
Wetlands and Stormwater Branch,
401 Oversight/Express Permitting Unit
1650 Mail Service Center
Raleigh, NC 27699-1650
SUBJECT: Stream Restoration Project - N4 Cluster, NCSU Centennial Campus
North Creek/Lake Raleigh/Ut to Walnut Creek (030402, 27-34-(3.5), B, NSW)
Dear Ian:
Attached are the level spreader calculations, details and Supplementary Form you requested
recently. I am also attaching new sets of the plans showing the corrected level spreader and
overflow design.
References to Phase A and Phase B are internal to the project. The plan is to repair the existing
48" CMP outlet pipe and construct the associated storm drainage and diversions this fall and
stabilize the areas outside the NRB, but wait until spring to do the stream grading and
restoration. However, it is still all one project, which we plan to start as soon as the permits are
in place.
Please contact me if you have further questions about this project.
Sin rely
Mack Little, RLA, ASLA, LEED A
LITTLE & LITTLE
Attachments
Copy: Jamie Shern
Michael Harwood
Rachel Miller
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Prepared by;
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221 Providence Road
Chapel Pull, NC 27514
[phone]
BA Project # 109010.10 Vol. I "L"
Hanging Pile
1ssuw Dates Descri ;,doii
21 Oct 10 DWQ Sui)iaittal
Level Spreader Design Calculations
NCSU N4 Stream Restoration
21 Oct 10
Ballentine
Associates, P.A.
List of Exhibits:
• Level Spreader Supplement Form
• Level Spreader Drainage Area Map
• Overflow Channel Drainage Area Map
• Level Spreader Sizing Calculations
• Overflow Channel Sizing & Lining Calculations
• Riprap Apron Calculations - Overflow Channel Entrance
• Splitter Box Orifice Calculations
• Splitter Box Weir Calculations
E
STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
LEVEL SPREADER - VEGETATED FILTER STRIP (L -VFS) SUPPLEMENT
I. PROJECT INFORMATION
Project name NCSU - N4 Stream Restoration
Contact name Ballentine Associates. P.A. Contact: George J. Retschle. P.E.
Phone number [phone]
Date October 20. 2010
Drainage area number
II. DESIGN INFORMATION
The purpose of the LS-VFS Buffer Rule: Diffuse Flow
Stormwater enters LS-VFS from The drainage area
Type of VFS Protected riparian buffer (slope < 5%)
Explanation of any "Other" responses above Stream and riparian buffer will be re-constructed as part of this project.
If Stormwater Enters the LS-VFS from the Drainage Area
Drainage area 65.080 ft2
Impervious surface area 52.987 ft2
Percent impervious 81.42 %
Rational C coefficient 0.87
Peak flow from the 1 in/hr storm 1.30 cfs
Time of concentration 5.00 min
Rainfall intensity, 10-yr storm 7.22 in/hr
Peak flow from the 10-yr storm 9.38 cfs
Design storm 1 inch/hour storm
Maximum amount of flow directed to the LS-VFS 1.3 cfs
Is a flow bypass system going to be used? Y (Y or N)

Explanation of any "Other" responses above 1.30 cfs is the peak flow to the LS. some of which is from overland flow not routed through
splitter box. Therefore. splitter box calcs are based on a slighly lower flow.
If Stormwater Enters the LS-VFS from a BMP
Type of BMP Other: Explained below
Peak discharge from the BMP during the design storm cfs
Peak discharge from the BMP during the 10-year storm cfs
Maximum capacity of a 100-foot long LS-VFS 2 cfs
Peak flow directed to the LS-VFS cfs I
Is a flow bypass system going to be used? (Y or N)
Explanation of any "Other" responses above
Form SW401 - LS-VFS - 22Sep2010 - Rev.7 page 1 of 3
LS-VFS Design
Forebay surface area
Depth of forebay at stormwater entry point
Depth of forebay at stormwater exit point
Feet of level lip needed per cfs
Computed minimum length of the level lip needed
Length of level lip provided
Width of VFS
Elevation at downslope base of level lip
Elevation at the end of the VFS that is farthest from the LS
Slope (from level lip to the end of the VFS)
Are any draws present in the VFS?
Is there a collector swale at the end of the VFS?
Bypass System Design (if applicable)
Is a bypass system provided?
Is there an engineered flow splitting device?
Dimensions of the channel (see diagram below):
M
B
W
y (flow depth for 10-year storm)
freeboard (during the 10-year storm)
Peak velocity in the channel during the 10-yr storm
Channel lining material
Does the bypass discharge through a wetland?
Does the channel enter the stream at an angle?
Explanation of any "Other' responses above
0 ft
0 in in
0 in
50 fUcfs
65 ft
66 ft
53 ft
332.20 fmsl
330.50 fmsl
3.21 %
n (Y or N) OK
n (Y or N)
Y (Y or N)
y (Y or N)
3.00 ft
8.00 ft
15.50 ft
0.25 ft
1.00 ft
4.31 fVsec
Pick one
n (Y or N)
y (Y or N)
Piprap lining will be provided in blind swale. Therefore. a forebay is not provided. By-pass
channel will be temporarily lined with straw matting, permanently lined with grass.
LV

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Form SW401 - LS-VFS - 22Sep2010 - Rev.7 page 2 of 3
III. REQUIRED ITEMS CHECKLIST
EDIT Please indicate the page or plan sheet numbers where the supporting documentation can be found. An incomplete submittal package will result
in a request for additional information. This will delay final review and approval of the project. Initial in the space provided to indicate the following
design requirements have been met. If the applicant has designated an agent, the agent may initial below. If a requirement has not been met, attach
justification.
Requried Item:
1. Plans (1" - 50' or larger) of the entire site showing:
- Design at ultimate build-out,
Off-site drainage (if applicable),
Delineated drainage basins (include Rational C coefficient per basin),
Forebay (if applicable),
High flow bypass system,
Maintenance access,
Proposed drainage easement and public right of way (ROW), and
Boundaries of drainage easement.
Initials Page or plan sheet number and any notes:
L4 Site & Grading Plan Level
Spreader Drainage Area Map
Level spreader will be located Wthin Centennial Campus. No
public rights-of-way are within close proximity to the project
site. Level Spreader to
be maintained by NCSU.
2. Plan details (1" = 30' or larger) for the level spreader showing:
- Forebay (if applicable),
High flow bypass system,
One foot topo lines between the level lip and top of stream bank,
Proposed drainage easement, and
Design at ultimate build-out.
3. Section view of the level spreader (1" = 20' or larger) showing:
- Underdrain system (if applicable),
Level lip,
Upslope channel, and
Downslope filter fabric.
4. Plan details of the flow splitting device and supporting calculations (if applicable).
5. A construction sequence that shows how the level spreader will be protected from
sediment until the entire drainage area is stabilized.
6. If a non-engineered VFS is being used, then provide a photograph of the VFS showing
that no draws are present.
7. The supporting calculations.
8. A copy of the signed and notarized operation and maintenance (0&M) agreement.
C4201 Level Spreader Enlargement & Details
C4201 Level Spreader Enlargement & Details
C4201 Level Spreader Enlargement & Details Splitter
Box Orifice Sizing Calculations Splitter Box
Weir Calculation
C4201 Level Spreader Enlargement & Details
N/A. VFS will be established with the reconstruction of the
stream and its buffer.
Level Spreader Sizing Calculations
Form SW401 - LS-VFS - 22Sep2010 - Rev.7 page 3 of 3
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0.27 AC (12,095 SF)
LEVEL SPREADER
IMPERVIOUS AREA= 1.22 AC (52,985 SF)
TOTAL LEVEL SPREADER
DRAINAGE AREA= 1.49 AC (65,080 SF)

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BALLE TINE
ASSOCIATES, PA
221 PRONDENCE ROAD, CHAPEL HILL, N.C. 27514
(919) 929 - 0481 (919) 489 - 4789
SCALE: 1" = 60,
DATE: 22 OCT 10
JOB NUMBER: 109010.10
DRAWN BY: SRM/MN
REVIEWED BY: GJR
SHEET
DA-2
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BY-PASS CHANNEL
OVERLAND AREA= 0.05 AC (2,469 SF)
BY-PASS CHANNEL
IMPERVIOUS AREA= 1.22 AC (52,985 SF)
TOTAL BY-PASS CHANNEL
DRAINAGE AREA= 1.27 AC (55,454 SF)

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BALLENTINE
ASSOCIATES, PA
221 PRONDENCE ROAD, CHAPEL HILL, N.C. 27514
(919) 929 - 0481 (919) 489 - 4789
SCALE: 1" = 60,
DATE: 22 OCT 10
JOB NUMBER: 109010.10
DRAWN BY: SRM/MN
REVIEWED BY: GJR
SHEET
DA-3
Level Spreader Sizina Calculations
PROJECT: NCSU N4 Stream Restoration
PROJECT NO.: 109010.10 Vol. 1 "O"
DATE: 20-Oct-10
LATEST PRINT DATE: 20-Oct-10
BMP ID: Level Spreader (only one proposed on project)
Level Spreader Purpose: Buffer Rule/Diffuse Flow
Level Spreader Receives Flow From:
Type of VFS:
Total Drainage Area to Level Spreader =
(see attached drainage area map)
Impervious Area to Level Spreader =
Percent Impervious =
ComDOSite Rational C Factor:
Cover Area C CA
Description (ac.)
Impervious: Deck 1.22 0.98 1.19
Pervious: Grass 0.27 0.40 0.11
Totals 1.49 1.30
Composite Rational C =
Design Storm:
Design Flow: Q = CIA =
Level Spreader Minimum Length = Q x 50 ft. _
0.87
1 in/hr Storm
1.30 cfs
65.00 ft
Ballentine
Associates, P.A.
CHANNEL DESIGN CALCULATIONS
BALLENTINE ASSOCIATES, P.A.
221 Providence Rd.
Chapel Hill, NC 27514
Ph. [phone] fax [phone]
PROJECT : NCSU N4 Stream Restoration
10-YrStorm
DATE : 25-Aug-10
REVISED: 20-Oct-10
10 YEAR CHANNEL FLOW DATA -DITCH SECTION
AREA = 1
C = C 'Ac Impervious C 0.9 , 5 Ac Pervious C 3.4 ,
Tc = 5.00
INTENSITY = 7.22 (in/hr)
FLOW = 8.81 (cfs)
DESIGN CRITERIA - MAX SLOPE USED TO CHECK LINING DESIGN
CHANNEL PROPERTIES:
N = 0.025 (Mannings 'n')
SLOPE= 0.038 (ft/ft)
Z REQUID= 0.76
M = 3 :1 (sideslope)
CHANNEL DIMENSIONS
DEPTH = 0.25 (ft)
WIDTH = 8 (ft) Bottom Width
TRACTIVE FORCE
T =Y*D*S Tractive Force (#/sq ft)
Y =WEIGHT OF WATER (62.4 #/cf)
D = DEPTH OF FLOW IN CHANNEL (ft)
S = SLOPE OF CHANNEL (ft/ft)
T = 0.6 (#/sq ft)
Maximum Allowable Tractive Force
L (#/sq ft)
I (#/sq ft)
N (#/sq ft)
I (#/sq ft)
N (#/sq ft)
G (#/sq ft)
Z ACTUAL
AREA = 2.19 (sq/ft)
WP = 9.58 (ft)
R = 0.23
Z ACTUAL= 0.82 MUST BE > THAN Z REQ'D. = 0.76
V = 4.31 (ft/sec)
LINING REQUIREMENTS
LINING : STRAW BLANKET 1.75 (#/sq ft) 0.59 #/sq ft
TOP WIDTH AT COMPUTED DEPTH = 9.50 ft
(DEPTH BASED ON CAPACITY CALCS)
COMPUTED
DEPTH = 0.25 ft
(BASED ON
CAPACITY CALCS)
8.00 ft
(BOTTOM WIDTH)
RiaraD Aaron Sizina Calculations
PROJECT: NCSU N4 Stream Restoration
PROJECT NO.: 109010.10 Vol. I "L"
DATE: 22-Oct-10
LATEST PRINT DATE: 22-Oct-10
Flow Rate and velocity based on : 10-yr storm
Diam inches
A 1.22 ft2
Q = cfs
V= fps
Ballentine
Associates, P.A.
221 Providence Road 919/929-0481 Chapel Hill
Eastowne Office Park 919/489-4789 Durham
Chapel Hill, NC 27514 919/489-2803 Fax
RipRap Size/Apron Length: Based upon Figures 8.06c and 8.06d from the New York DOT Dissipator Method
in the North Carolina Erosion and Sediment Control Planning and Design Manual, Revised June 1, 2006
Outfall Pipe Diam
(in) Flow, Q
(cfs) Velocity, V
(fps) Zone
(Fig. 8.06c) Class
(Fig. 8.06d)

FES 31 18 8.63 7.16 1 A - Stone Filling Fine
Calculations:
Zone Width Length Min Thickness Min d(max) Diameter
1 3 4 9 3
2 3 6 22 6
3 4 8 18 13
4 4 8 18 13
5 5 10 27 23
6 6 10 27 23
FES 31
d (max, design) = 6 inches From Figure 8.06e
d (max) = 3 inches Check min diameter above
Diameter of Pipe = 1.5 ft
Zone = 1
Length of Apron = 6 ft
Width Apron = 4.5 ft
Thickness (design) = 9 Use the greater dmax
Thickness (min.) = 9 in formula
Thickness (actual) = 9 inches
Length of Apron = 6 ft
Width Apron = 4.5 ft
Thickness (actual) = 9 inches

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Solitter Box Orifice Sizina Calculations
PROJECT: NCSU N4 Stream Restoration
PROJECT NO.: 109010.10 Vol. 1 "O"
DATE: 20-Oct-10
LATEST PRINT DATE: 20-Oct-10
BMP: Level Spreader - Splitter Box
Q = CdA x J(291-10), where:
Q= Discharge (cfs)
C, = Coefficient of discharge (0.60 is common for stormwater orifices)
A = Cross-sectional area of flow at orifice entrance (sq. ft.)
g = Acceleration from gravity (32.2 ft/sec2)
Ho = Driving Head (ft) - measured from centroid of orifice area to water surface
[Use Ho/3 to reflect that head is falling as drawndown occurs]
Targeted Flow Rate (Q)* = 1.196 cfs (max)
1.22 ac x 0.98 x 1 in/hr
Selected Ho = 1.50 ft. (= Ho)
Actual Average Flow to
Using Chosen Orifice Diameter
Hd3 = 0.500 ft.
Cd = 0.60
A= Q
CA29Ho)
A = 0.351161 s.f.
Theoretical Orifice Diameter to
Carry Targeted Flow Rate = 0.668834 ft.
= 8.03 inches
Diameter Chosen = 8.00 inches
1.188 cfs
Ballentine
Associates, P.A.
A= 0.348889 s.f.
* This is the flow that will pass through the splitter box and be directed to the BMP. Flows in excess of this will
flow over the by-pass weir within the splitter box and will by-pass the BMP.
Hydrology Report
Hydraflow Express by Intelisolve
N4 Stream Restoration - Splitter Box Weir
Hydrograph type = Rational
Storm frequency (yrs) = 10
Drainage area (ac) = 1.270
Rainfall Inten (in/hr) = 7.238
OF Curve = SampleExpress.IDF
Thursday, Oct 21 2010
Peak discharge (cfs) = 8.825
Time interval (min) = 1
Runoff coeff. (C) = 0.96
Tc by User (min) = 5
Rec limb factor = 1.00
Hydrograph Volume = 2,647 (cult); 0.061 (acft)
Q (cfs)
10.00
Runoff Hydrograph
10-yr frequency
8.00
6.00
4.00
2.00
0.00 -11
0
5

Q (cfs)
10.00
8.00
6.00
4.00
2.00
0.00
10
Time (min)
Runoff Hyd - Qp = 8.82 (cfs)
Weir Report
Hydraflow Express by Intelisolve
Splitter Box #30
Rectangular Weir
Crest = Sharp
Bottom Length (ft) = 6.00
Total Depth (ft) = 1.00
Calculations
Weir Coeff. Cw = 3.33
Compute by: Known Q
Known Q (cfs) = 8.82
Depth (ft)
2.00
1.50
1.00
0.50
0.00
-0.50
0 1
Weir
Splitter Box #30
Highlighted
Depth (ft)
Q (cfs)
Area (sqft)
Velocity (ft/s)
Top Width (ft)
Thursday, Oct 21 2010
= 0.58
= 8.820
= 3.48
= 2.54
= 6.00
Depth (ft)
2.00
1.50
1.00
0.50
0.00
-0.50
8
Length (ft)
2 3 4 5 6 7
W. S.