20080214 Ver 1_More Info Received_20080227

Environmental Consultants, PA
Road • Raleigh, North Carolina 27614 • Phone: [phone] • Fax: [phone]
www.SandEC.com
27 February 2008
S&EC Project # 10775.W8
N.C. DWQ
Attn: Mrs. Cyndi Karoly
2321 Crabtree Blvd., Ste. 250
Raleigh, NC 27604
Re: DWQ EXP No. 08-0214
E-27 (Fuquay Elementary School)
Wake County, NC
Dear Mrs. Karoly:

DENR - *AI t-H Q fAV i'Y
"STtANDS AND STORMWATER BRANCA
The attached information should satisfy the request for additional site plan revisions and/or
related information that we received from Mr. Gyamfi in your office via fax on the afternoon of
22 February 2008, and via U.S. mail the following Monday.
Please review the attached response from the site planner and the related level spreader design
information. It corresponds to DWQ design requirements, and meets the requirements for the
requested Water Quality Certification. We look forward to hearing from you soon.
Attachments:
DWQ Response Letter
Level Spreader Design Calculations
Level Spreader Design Supplement
Outlet Protection Design Calculations
C3.1 through C3.5
C7.9 through C7.10
Charlotte Office:
236 LePhillip Court, Suite C
Concord, NC 28025
Phone: [phone]
Fax: [phone]
Greensboro Office:
3817-E Lawndale Drive
Greensboro, NC 27455
Phone: [phone]
Fax: [phone]

26-February-08
TO: Mr. Joseph Gyamfi- Division of Water Quality
FROM: Renee C. Pfeifer - CLH Design, PA
RE: DWQ EXP NO. 08-0214- RESPONSES TO EXPRESS REVIEW COMMENTS
E-27 ELEMENTARY SCHOOL- HERBERT AKINS ROAD
CC: File (07-129/prmt)
Please find attached as follows:
Exterior Level Spreader:
Comment 1: Receiving Flow in Excess of Bioretention Design Volume:
a. Please provide calculations for the flow used to design the level spreader. This is
supposed to be the flow in excess of the Bioretention treatment volume. Alternatively, as
discussed during our phone conversation on Friday, February 22, 2008, please provide design
calculations, revised Level Spreader Supplement and plan sheets for the newly proposed level
spreader and by-pass system.
Response: As discussed in our phone conversation feb. 22nd the level spreader has been sized for the 1"per
hour flow discharged from the upstream Bioretention area. Larger flows bypass the level
spreader and are routed through a 15" RCP to a rip rap dissapator. Design Calculations BMP
Supplement are enclosed.
CLH design, P.a.
MacGregor Park, I25 Edinburgh South, Suite 310
Cary, North Carolina 27911
Phone: [phone] Fax: [phone]
End of responses
PROJECT NAME
E-27 Elementrv School
NC
For Level Spreaders Receiving Flow From a BMP
Type of BMP
Drawdown flow from the BMP cfs
For Level Spreaders Receiving Flow from the Drainage Area
Drainage area 97,574 ft2
Impervious surface area 33,970 ft2
Percent impervious 0.35
Rational C coefficient 0.52
Peak flow from the 1 in/hr storm 1.165 cfs
Time of concentration 5 min
Rainfall intensity, 1 0-yr storm 7.22 in/hr
Peak flow from the 10-yr storm 8.41 cfs
Where Does the Level Spreader Discharge?
To a bioretention cell? N (Y or N)
To a wetland? Y (Y or N)
To a filter strip or riparian buffer? N (Y or N)
Other (specify)
Filter Strip or Riparian Buffer Characterization (if applicable)
Width of grass 30 ft
Width of dense ground cover ft
Width of wooded vegetation 0 ft
Total width 30 ft
Slope (from level lip to to top of bank) 6 %
Are any draws present? N (Y or N)
Level Spreader Design
Forebay surface area 68 sq ft
Feet of level lip needed per cfs 13 ft/cfs
Answer "Y" to one of the following:
Length based on the 1 in/hr storm? Y (Y or N)
Length based on the 10-yr, 24-hr storm? N (Y or N)
Length based on the BMP discharge rate? N (Y or N)
Design flow 1.165 cfs
Is a bypass device provided? Y (Y or N)
Length of the level lip 15 ft
Are level spreaders in series? N (Y or N)
DATE
2/25/2008
PROJECT NO
07-127
BY
JPK

s:\1319\0001`talcs\07-127_Le iSpreader.XLS printed: 2/27/20088:32 AM Page 1 of 2
DATE
LEVEL SPREADER DESIGN
2 08
PROJECT NAME PROJE ROJECT NO
E-27 Element School 07-127
LOCATION BY
Fuauav-Varina. NC JPK
Pipe Size to Level Spreader
Bypass Pipe Size
8 in
15 in
Max Head on Level Spreader Pipe
Area of Pipe to Level Spreader
Max Flow to Level Spreader
1 in/hr design flow
Level Spreader Design Criteria
Required length of Level Spreader (based on Max Flow)
0.5 ft
0.35 sf
1.188 cfs (orifice equation)
1.165 cfs (Less than or equal to Max Flow)
13.00 ft/cfs
15 ft.
s:\1319\0001\ca1cs\07-127_ LewlSpreader.XLS printed: 2/27/2008 8:32 AM Page 2 of 2
o?oF WArF9oc
WDENR
STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
LEVEL SPREADER, FILTER STRIP AND RESTORED RIPARIAN BUFFER SUPPLEMENT
This form must be filled out printed and submitted.
The Required Items Checklist (Part III) must be printed, filled out and submitted along with all of the required information.
I. PROJECT INFORMATION
Project name E-27
Contact name Renee Pfeifer
Phone number [phone]
Date February 26, 2008
Drainage area number A
11. DESIGN INFORMATION
For Level Spreaders Receiving Flow From a BMP
Type of BMP Bioretention- Overflow (1 in/hr)
Drawdown flow from the BMP 1.165 cfs
For Level Spreaders Receiving Flow from the Drainage Area
Drainage area
Impervious surface area
Percent impervious
Rational C coefficient
Peak flow from the 1 in/hr storm
Time of concentration
Rainfall intensity, 10-yr storm
Peak flow from the 10-yr storm
Where Does the Level Spreader Discharge?
To a bioretention cell?
To a wetland?
To a filter strip or riparian buffer?
Other (specify)
Filter Strip or Riparian Buffer Characterization (if applicable)
Width of grass
Width of dense ground cover
Width of wooded vegetation
Total width
Slope (from level lip to to top of bank)
Are any draws present?
Level Spreader Design
Forebay surface area
Feet of level lip needed per cfs
Answer "Y' to one of the following:
Length based on the f in/hr storm?
Length based on the 10-yr, 24-hr storm?
Length based on the BMP discharge rate?
Design flow
Is a bypass device provided?
Length of the level lip
Are level spreaders in series?
Do not complete this section of the worksheet.
ft2
ft2
Do not complete this section of the worksheet.
Do not complete this section of the worksheet.
cfs Do not complete this section of the worksheet.
min
in/hr Do not complete this section of the worksheet.
cfs Do not complete this section of the worksheet.
N (Y or N)
N (Y or N)
Y (Y or N) Please complete filter strip characterization below.
4 filter strip is specified from the level lip of the level spreader to the property line (aprx. 25)
15 ft
0 ft
0 ft
15 ft
5 %
N (Y or N) OK
N sq ft OK
13 ft/cfs
Y (Y or N)
N (Y or N)
N (Y or N)
1.165 cfs
Y (Y or N)
15 ft
N (Y or N)
OK
#VALUE!
Form SW401-Level Spreader, Filter Strip, Restored Riparian Buffer-Rev.3 Parts I. and ll. Design Summary, page 1 of 2
Bypass Channel Design (if applicable)
Does the bypass discharge through a wetland? N (Y or N)
Does the channel enter the stream at an angle? N/A
Dimensions of the channel (see diagram below):
M ft
B ft
W ft
y ft
Peak velocity in the channel during the 10-yr, 24-hr storm cfs
Channel lining material

M
M

B
Form SW401-Level Spreader, Filter Strip, Restored Riparian Buffer-Rev.3 Parts I. and II. Design Summary, page 2 of 2
• ' ' • • DATE DESIGN PHASE
12-11-07 PRELIM
PROJECT NAME PROJECT NO CONSTR
Akins Road Elementary School 07-129 REVISION
LOCATION BY RECORD
Fu ua Varina, NC KAL OTHER / X /
CHECKED BY (SPECIFY) Permit
SJ M
Storm Outlet Structure
FES No.= E6 Q1/Qfull = 0.11 Qio/Qfull = 0.77
Pipe Dia= 18 in ViNfull = 0.67 VNfull = 1.10
Qio= 8.38 cfs V10= 6.7 fps
Qfull = 10.90 cfs Slope= 1.0%
Vfull = 6.10 fps Pipe Inv= 395.60 ft
Q1 = 1.19 cfs V1 = 4.1 fps
From Fig. 8.06.b.1: Zone = 2
From Fig. 8.06.b.2: D50 = 8 in
DMAX = 12 in
Riprap Class = B
Apron Thickness = 18 in
3 Apron Length = 9 ft

Length Apron Width = 3xDia = 5 ft
Storm Outlet Structure
FES No.= Bio-Retention Q1/Qfull = 0.10 Qio/Qfull = 0.27
Pipe Dia= 15 in ViNfull = 0.67 VNfull = 0.83
Qio = 3.83 cfs Vio = 9.7 fps
Qfull = 14.30 cfs Slope= 4.9%
Vfull = 11.65 fps Pipe Inv= 394.13 ft
Q1 = 1.47 cfs V1 = 7.8 fps
From Fig. 8.06.b.1: Zone = 2
From Fig. 8.06.b.2: D50 = 8 in
DMAX = 12 in
Riprap Class = B
s Apron Thickness = 18 in
3 Apron Length = 8 ft

Length Apron Width = 3xDia = 4 ft