SW8080820_Historical File_20080904

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1. PROJECT DESCRIPTION
Design Calculations
Stormwater Treatment Facilities
for
Southeastern Pre -School Education Center (S.P.E.C.)
located in
Burton Industrial Park-Onslow County
The Project consists of proposed child care center.
2. COMPUTE POND AREA REQUIRED
a. Compute Percent Impervious:
Impervious Areas:
On -Site Buildings
On -Site Streets
On -Site Parking
On -Site Sidewalks
Other on -site
Off -site
Sub -Total
FUTURE
FUTURE(reserved)
Total
Total Area Drainage to Pond:
Percent Impervious =
b. Compute Pond Surface Area
s
y
>:•
v
Total
24,200
0
68,070
4,020
0
0
96,290 0 96,290
5,000
0 0 0
9e,290 5,000 101,290
0.427 or 42.7 %
Using Surface Area to Drainage Area Ratio Chart for 90% TSS Removal (copy attached) and
assuming ..= foot pond depth:
SAIDA = 4.40 % (interpolated - Select from Highlighted Cell in SAIDA)
Therefore:
Surface Area = SAIDA x Drainage Area
10,454 SF',, says, : '#: SF
Q E e > 10,454
H
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c. Compute Minimum Pond Dimensions
Assume rectangular shape with 3:1 Length (L) to Width (W) Ratio:
Min Length = 177.09 feet
Min Width = 59.03 feet
Site conditions, however, dictate irregular shaped pond:
Hydr. Length feet
so, Hydr. Width (aN A. 61.3 feet (avg)
Actual L/W = 3.0 (irregular shape)
3. DETERMINE REQUIRED STORAGE VOLUME
Design Rainfall Depth` inches
=�
Using Schuler "Simple Method":
Rv = 0.05 + 0.009(I) where I = percent impervious
Rv = 0.434 in/in
Control Volume = Design Rainfall x Rv x Drainage Area
Control Volume = 12,879 CF sa , ;,
Y = a ; " wCF
Must be > 12,879
4. DETERMINE REQUIRED STORAGE DEPTH
Assume: 3:1 side slopes
solving for depth (d) by trial & error:
d = 1.07
S. DETERMINE ORIFICE SIZE
Control Volume must be drawn down over a 2 day - 5 day period.
Using orifice equation, solve for Diameter (D) that results in 3-1/2 day period:
D=(Q10.026(h)')"
Where: Q = (Control Volume 1 3.5 days x 86,400 sec/day)
0.044 cfs
h= D13 E C E I V
= 0.36 � D
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Solving for D:
D = 1.69 Use `fs - �'"'-?avlE. " pipe
Actual Drawdown with actual drawdown pipe diameter (using orifice equation):
Qavg= 0.035 cfs
Draw Dow = days OK, ¢ 6.0
:8� x
Qmax= 0.061 cf
6. SELECT OUTLE UCT 5IZ
Size outlet structure such that depth of Q 10 now < or + to >>'. [5:;"'" Feet
Using Rational Formula (Q=CIA)where:
Ccum = 0.43
110 = ;::";:.:.v :: ` inlhr
A = 5.45 ac
010 = 16.67 cfs
Using Francis Formula (Q=3.OLH'-r) to solve for L such that H = i.5 Feet
Min L = 3.026 Linear Feet
Use
Use
7. DETERMINE Q10 STAGE
010 =
21 Linear Foot Weir
5 Square Precast Structure
16.67 cfs
From Routing Analysis, H 10 =
8. DETERMINE Q100 STAGE (ELEV. OF EMERGENCY SPILLWAY)
Using Rational Formula (Q=CIA) where:
Cimper = 0.8
Cpery = 0,2
Ccum = 0.43
A = 5.45 ac
E C �:
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Temporary level should be 33.07
Temp. Pool Volume = 13,341 CF
11. SUMMARY
Pond Elevations;
Top Berm (minimum)
100-Yr. Storm
10-Yr. Storm
1.5-inch Storage
Permanent Pool
Pond Bottom
12.'WET DETENTION BASIN SUPPLEMENT
Site Characteristics
Drainage Area
237,385 sf
Impervious Area
101,290 sf
% Impervious
42.7 %
Design Rainfall Depth
1.5 in
Storage Volume
Min, Volume Required
12,879 of
Volume Provided
13,341 cf
Peak Flow Calculations
1-yr. 24 hour rainfall depth
in
Rational C, predevelopment
~
Rational C, post development
0.43
Rainfall Intensity 1 yr 24 hr
0.15 inlhr
Pre Dev 01(24 hour)
0.12 cfs
Post Dev Q1 (24 hour)
0.35 cfs
PrelPost Flow Control
0.23 cfs
Basin Elevations
H= 0,39
H100 = 1.37
H10 = 1.12
storage depth = 1.07
Pond depth = 7,00
or greater
Relative al
9.83
33.76
9,44
33.37 (emerg. we
9.19
33.12
8.07
33.07 (primary we
7.00
32.00 (invert out i
0
25.00

Aug 07 08 10:07a
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Q1100 = 22.12 cfs
From Routing Analysis, H 100 =
9. DETERMINE Q100 STAGE OVER EMERGENCY SPILLWAY {TOP BERM ELEV.)
Assume primary spillway blocked (i.e., emergency spillway to accommodate Q100)
Emergency spillway shall be a broad crested earthern weir designed to pass 100 year storm.
Using broad crested weir equation H = (Q/(Cw x QP
where: Q = Q100 22.12 r-fs
Cw = 3.0
Length feet
H = 0.39 feet
10. FOREBAY SIZING
Compute Actual Pond Volumes (using average end method):
Avg Incr. Incr.
Main Bay Volume: Elevation Area (SE) Area (,SF DeRth (FT) ol (CF)
Pond Bottom
6.50 25,171
873
BBottomVeg $helf W
•0.50 3,908
A;-o 3: 7,817
Normal Pond
Main Bay Volume = 29,080 CF
Forebay Volume : Elevation Area (SF Area (SF Depth (FT) Vol (CE
Pond Bottom
NormalPond 32.00
1,159 7.00 N-`.1.':N.'M. ..' . 8,110
Forebay Volume = 8,110 CF
Total Pond Volume = 37,189 CF
Total Pond Area = 11,026 SF
Forebay Volume equates to of Total Volume
Must be > 18% and < 22%
Average Pond Depth = 3.37 feet
Compare to assumed Depth g,jfeet
Temp- Storage Volume : Elevation Area [SF) Area (SF) Depth (FI) Vol (CF)
Normal Pond 32,00 11,026
Temp. Pond Level 12,469 1.07 13,341
E
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Basin Bottom Elevation
Sediment Cleanout Elevation
Permanent Pool Elevation
Temporary Pool Elevation
24.00 feet (Elev)
25.00 feet (Elev)
32.00 feet (Elev)
33.07 feet (Elev)
Volume and Surface Area Calculations
SAIDA ratio
4.40
Surface Area Required
10,454 sf
Surface Area Provided
11,026 sf
Permanent Pool Volume
37,189 of
Average Depth
3.37 feet
Forebay Volume
8,110 of
Forebay % of Total Volume
21.8 %
Temporary pool Area
13,911 sf
Drawdown Calculations
Drawdown Time
4.42 days
ar ate
Pre Dev Q1(24 hour)
0.12 cfs
Post Dev Q1 (24 hour)
0.06 cfs
iiion mate%
Diameter of orifice
1.50 in
Design TSS Removal
90 %
Basin Side Slopes
3 :1
Vegetated Shelf Slope
10 :1
Vegetated Shelf Width
10 ft
Length to Width Ratio
3 :1
Trash Rack?
Yes
Freeboard Provided?
Yes
Vegetated Filter Provided?
No
Recorded Easement?
Yes
Captures all Runoff?
Yes
Drain Mechanism
Pump
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AUG 1
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JOHN L. PIERCE & ASSOCIATES, P.A.
LAND SURVEYWG - LAND PLANNING - MAPPING
P.O. BOX 1685
SACKSON`IILLE, NC 28541
OFFICE: [phone] FAX: [phone]
E-MAIL: [e-mail]
Or briani jl nn c.com
TO: Ms. Linda Lewis
N.C. Department of Environment and Natural
Resources — Department of Stormwater
127 Cardinal Drive Extension
Wilmington, NC 28405
Letter of Transmittal
BATE:
August 8, 2008
Ai TENT►ON:
Linda Levis
Re:
Southeastem Pre -School -Burton Industrial Park
COPIES DATE NUMBER DESCRIPTION
2 Copies of revised sheet 2 of 5
I
THIS WAS LEFT OUT OF THE PREVIOUS SUBMITTED
REVISED INFORMATION REQUESTED
i
REMARKS:

JOHN L. PIERCE & ASSOCIATES, P.A.
LAND SURVEYING — LAND PLANNING — MAPPING
OgS4-
PD. BOX 1685
JACKAMWMLE, NC'28541
OFFICE: [phone] FAX: [phone]
E-MAIL: [e-mail]
Or brianj a�jlnnc.com
TO: Ms. Linda Lewis
N.C. Department of Environment and Natural
Resources — Department of Stormwater
127 Cardinal Drive Extension
Wilmington, NC 28405
je
* 01�0*"er of Transmittal
COPIES DATE NUMBER DESCRIPTION
1 Copy of your e-mail dated 7/28/08
1 Letter from engineer Dave Newsom
2 Signed copies of page Form SWU-101
2 Wet Detention Basin Operation and Maintenance A eement
2 Revised Design Calculations
REMARKS:
SIGNED:- A�L A dz&x

Aug 07 08 10:06a
p.2
Crystal Coast En ineeri n� PA
3817-3 Freedom Way
Hubert, N.C. 28538
I Tel: [phone] Fax: [phone]
! Email: crystalcoasteng@Ibize xom
August 7, 2008
Ms. Linda Lewis
N.C. Division of Water Quality
127 Cardinal Drive Extension
Wilmington, N.C. 28405
Re: Southeastern Pre -School (S. P.E.C) — Burton Park
Onslow County
Dear Ms. Lewis,
We are in receipt of your Request for Additional fntormation dated July 28, 2008 for the
referenced project. We provide the following information to allow you to continue the
stonnwater review (item numbers correspond to your original Requeso:
1. Wet Pond Maintenance Agreement attached.
2. Dated application as requested.
3. Revised calculations confirming orifice flow rate < pre -development Q1 24 hour.
4. Soils report attached.
We are hopeful that this response addresses all concerns and that the permit can be issued in
the near future. Should you have questions or additional concerns, please feel free to contact
me.
Yours try
Davt'd K
CRYSTAL COAST ENGINEERING
cc: John L Pierce & Associates, PA
D E C E l 1Y iDD
AUG 1 I Z;,d3
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Southeastern Pre -School Burton IP
Subject: Southeastern Pre -School Burton IP
From: Linda Lewis <[e-mail]>
Date: Mon, 28 Jul 2O08 11:28:59 -0400
To: Betty Bullock <[e-mail]>, Dave Newsom <[e-mail]>
Betty & Dave:
The Division received an incomplete stormwater permit application for the subject
project on July 23, 2008. Please address the following deficiencies and resubmit
the information in order to accept this project for review:
1. Please provide a signed & notarized Wet Pond Operation and Maintenance plan.
2. Please date Mr. Saucier's signature on page 4 of the application.
3. Please note that for all projects subject to NPDES Phase II Session Law design
criteria, the pre -development peak flow from the 1 year 24 hour storm must be
included in the calculations. The orifice must have a flowrate that is less than
the pre -development peak flow.
4. A soils report for the site with the SHWT elevation noted.
Thanks,
Linda
1 of 1 7/28/2008 11:29 AM

JOHN L. PIERCE & ASSOCIATES, P.A.
LAND SURVEYING - LAND PLANNING - MAPPING
P.O. BOX 1685
JACKSONVILLE, NC 28541
OFFICE: [phone] FAX: [phone]
E-MAIL: bettybaj1pne.corn
Or [e-mail]
TO: Ms. Rhonda Hall
N.C. Department of Environment and Natural
Resources — Department of Stormwater
127 Cardinal Drive Extension
Wilmington, NC 28405
¢�, � Z
v �
2 a 2�
er of Transmittal
�1�
DATE:
July 22, 2008
ATTENTION:
Rhonda Hall
Re:
Southeastern Pre -School — Burton Industrial Park
COPIES DATE NUMBER DESCRIPTION
2 Sets of plans
2 Stormwater applications with calculations
1 Check in the amount of $505.00
L. .,
REMARKS: