SW8000612_COMPLIANCE_20000620

STORMWATER DIVISION CODING SHEET
POST -CONSTRUCTION PERMITS
PERMIT NO. Sw dal
DOC TYPE ❑ CURRENT PERMIT
❑ APPROVED PLANS
❑ HISTORICAL FILE
COMPLIANCE EVALUATION INSPECTION
DOC DATEaGYJ
YYYYMM DD

Eastwind Engineering
Company, LLP Sheet No. 1 of 1
Job Kinko-a Subject lnfitration System Des' n Job No. 20001.00
Designed by BEE Date 612QM Checked by Date
infiltration System Design Kinko's Oleander Drive
Determine runoff amount:
Total area = 0.80 acres < 20 acres, therefore use the rational method
Impervious area = 0.54 acres
Pervious area = 0.26 acres % impervious = 67%
ESIGN
Collect the runoff from the first 1.5 inch of rainfall.
Determine Composite "C" value:
C (pavement) = 0.95 X 0.67 = 0.64
C (grass) = 0.20 X 0.33 = 0.07
Composite C = 0.71
Volume to store = Runoff = CIA - 3,100 ft3
MY DE WILMINGTQN-,
Store the volume of runoff minus the volume infiltrated during the storm.
,�+syioff- �e
ONrrrr0rr / I
�•' �FESSip'•��q •%,
t SEAL a
y� 19742 tku
CN
!' k AV,"
0.9�ov
Use 10-year design storm, 6 hr duration per City of Wilmington standards.
Depth = 4.80 inches = P
Use SCS Curve Number
Asphalt = 98
Baymeade Soil = 39
CN = (% impervious)(Asphalt C)+ (% pervious)(pervious C)
CN 7 79
Soil storage Capacity, S = 1000/CN-10 = 2.70
Runoff, R = P� 0.2S)z - 2.6 inches
(P+O.BS)
Runoff volume = Runoff Depth X Area = 7,573 W
Volume to store = 7,573 fta
Minimum Volume to Store (prior to subtracting infiltrated amount) = 7,573 ftCEIVE
JUN 2 9 2000
DWQ
PROJ # �5(,u$ 0b0cV12

Eastwind Engineering
Company, L.LP
6129/00
Sheet No. 1 of 2
Job Kinko's Subject Infitration System Design Job No. 20001.00
Designed by RPB Date 6/20/00 Checked by Date
Design Post Development Discharge Rate To Equal Pre -Development Discharge Rate .
Hydrogranh Formulation Kinko's Oleander Drive
1.) Estimate Peak
Watershed Area = 0.80 acres
Pre -Development Discharge Rate Determination, Qp, Qp,a=CIA C=
Determine Rainfall Intensity, I
Kirpich Method(<20 acres)
L H T, I (10 Year) t (50 Year)
185, . 2 ,; 2 7.23 8.87
Post Development Discharge Rate Determination, Qposr
Determine Rainfall Intensity, I
Kirpich Method(<20 acres)
L H T, 1 (10 Year) 1 (50 Year)
68.' 0.V i 7.23 8.87
2.) Estimate Volume of Run-off
(Cfs)
(Cfs)
1.16
1.42
Qp..t=CIA
C= 0.174`,-
00os40 QOsso
(Cfs)
(Cfs)
4.22
5.18
Use i0-year design storm, 6 hour duration. Depth = R'_' 4,40{;! inches
Pre Devel. Soil Storage Capacity, S = 10001CN -10 = 15.64 where CN =t_39j
Pre Devel. Run-off, R=(P - 0.2 S)`/(P + 0.8 S) P = 4.8
Post Devel. Soil Storage Capacity, S = 10001CN -10 = 2.70
Post Devel. Run-off, R=(P - 0.2 S)`/(P + 0.8 S)
3.) Set the shape of the hydrograph
Pre Devel. Time to Peak, Tp = 43.5 * Area * Runoff
Qpre10
Post Devel. Time to Peak, Tp = 43.5 * Area * Runoff
Qpostl 0
4.) Estimate the Required Storage, S
P = 4.8
R = 0.16
where CN
R = 2.61
-1 4.9 min.
S = (Qpost-Qpre) x Tpl Opost x 1.39 1 5,495 CF
5.) Hydrograph Formulation
21.5 min.
Discharge (Q)
Time t min. Post Pre Time Increment = `.%'0 1ti'r"j*Tp
C:\Eastwind\k!nkosl1nfi1_-2 10-Year Hydrograph

c
Eastwind Engineering
Company, LLP
Sheet No. 2 of 2
Job Kinko's Subject Infitration System Design Job No, 20001.00
Designed by RPB Date 6/20/00 Checked by Date
0
0.00
0.00
2.15
0.10
0.47
4.30
0.40
1.12
6.45
0.87
0.89
8.60
1.46
0.50
10.75
2.11
0.28
12.90
2.76
0.16
15.04
3.35
0.09
17.19
3.82
0.05
19.34
4.12
0.03
21.49
4.22
0.02
23.64
4.12
0.01
25.79
3.82
0.01
27.94
3.38
0.00
30.09
2.97
0.00
32.24
2.61
0.00
34.39
2.29
0.00
36.54
2.01
0.00
38.69
1.77
0.00
40.84
1.55
0.00
42.99
1.36
0.00
45.13
1.20
0.00
47.28
1.05
0.00
49.43
0.92
0.00
51.58
0.81
0.00
53.73
0.71
0.00
55.88
0.62
0.00
58.03
0.55
0.00
60.18
0.48
0.00
62.33
0.42
0.00
64.48
0.37
0.00
66.63
0.33
0.00
66.78
0.29
0.00
70.93
0.25
0.00
73.08
0.22
0.00
75.22
0.19
0.00
77.37
0.17
0.00
79.52
0.15
0.00
81.67
0.13
0.00
83.82
0.12
0.00
85.97
0.10
0.00
88.12
0.09
0.00
90.27
0.08
0.00
92.42
0.07
0.00
94.57
0.06
0.00
6/29/00
1Q;.Year Storm Event IlnfloHydrogrob
Post Devel Inflow -6-Pre Devel Inflow
Vl
4
2 A
i/i
ti.
0 20 40 60 80 100
Time, t (min)
C:\Eastw1ndWnkosllnfil_--2 10-Year Hydrograph

Eastwind Engineering
Company, LLP
Job Konko's Subject tnfitration_S_ystem Design Job No. (MF 001
Designed by 132$ Date 6120100 Checked by Date
Kinko's Oleander Drive
1.) Determine Trench Volume per linear foot including stone: Use 24" ADS Pipe
pipe inside diameter (in) =
24
clear width between pipes (ft) =
1.57
pipe outside diameter (in) =
27.8
trench width (in) =
46.6 - 3.89 feet
rock void,ratio (%) =
40
pipe volume (cf) =
3.14
rock volume (cf) =
6.08
void volume (cf) =
2.43
Total volume of water per linear foot (cf):
5.58
2.) Determine Infiltration Rate For Full Trench:
From Darcy's Law, q = kiA = (k)(h/L)(A), where h/L is the hydraulic gradient.
min. distance to SHWT (ft) = 2 0.00
min = depth EP to top of pipe (in) 16 2 — -- -1.35
•
depth of stone under pipe (in) =
4
depth to seasonal high water table (ft) =
6
coefficient of permeability, k (cm/s) =
0.0061
proposed bottom area of trench (sf) =
1,165
head loss, h(ft) =
-4.65
unit length, L(ft) =
-2.00
q (cfs/lf) = 0.001 B1 q (cfs) = 0.54
Ma.
E1ec
0.00
-1.35
-3.67 -3.67
-4.00 -4.00
-6.00 -6.00
Check the outflow from the pipe, (ADS Tech Note 2.105). hi= 24 inches
Outflow, Q= 0.04+1.1(h;)+0.112(h;)2 Q = 0.203 cfs/ft > 0.00181 cfs/lf
Therefore infiltration rate of 0.0018 cfs/If is OK.
3.) Approximate Infiltration Time For Full Trench:
Depth of water in trench will vary. Use one half of depth as an average.
qW2 (cfs/If) = 0.00090 q (cfs) = 0.27
Time for water to exfiltrate from trench = 7.8 hours
c:lEastwindlKink6sllnfil_-2 Infiltration-24" pipe

Eastwind Engineering
Company, LLP
Job K oko's Subject lnfitration System Desian Job No. QQE.001
Designed by E?P_S Date 6l20M Checked by Date
4.) Determine Infiltration Rate during Storm Event
Ideally, the trench will completely fill with water at the end of the storm event.
The amount infiltrated during the storm will vary with time, based on the driving head.
Since infiltration rate varies linearly with the driving head as shown below, assume
the trench is half full for the entire storm period as an average to determine amount
infiltrated during the storm event.
Amount infiltrated during the storm event = 6hrs x infiltration rate at h(ft) = 2.33
Rate of infiltration qw (cfsllf) = 0.00090
7.0
6.0
S 5.0
"O
M 4.0
2
M 3.0
C
2.0
�L
1.0
0.0
Ln 'qr Ir 'r a -It M Cl) CO CO CO C7 Cl) M C?
O O O O O O O O O O O O O O O
ilJ Lit W W W W W W W W W W W W W
- CO CO M V O Cn CC'?,CG OS O CO
C7 CD V O -3 O C7 d 2 h N
ti CV M LO r- CO +- r r r - - r N N
Infiltration Rate (cfs/10
5.) Size The Infiltration System
Linear feet required for storage(wjo infiltration): 1$358
Adjust layout until Runnoff - Q16 = Storage
Try 1.57 rows at 191 feet. End length = 4.5 feet.
Linear feet used for infiltration: 300 Infiltration Rate, q (cfs) = 0.27
Storage = 1,722 (cf)
Amount Infiltrated, Qlc = 5,855 (cf)
Runoff - Q16 = 1,717 (cf) < 1,722 (cf)
c:lEastwindlKinkoslinfif_-2 Infiltration-24" pipe

INFILTRATION TRENCH ANALYSIS
Project # 000612
Project Name Kinko's Retail Store
Recvng Stream Hewletts Creek
Drainage Basin Cape Fear
Site Area 0.8 acres
Impervious Area Calculation
Buildings
Parking/Asphalt
Concrete
Total
Volume/Storage Calculation
Required
Design Storm
RV
VoI u me'.fo Sti3ce
Provided
Filename: S:IWQSIINTRENCH1000612.WK1
Date 05-J u I-2000
Reviewer Lewis
Classification SA
Index # 18-87-26
Drainage Area 34848 SF
0.80 Acres
1 Rational C
5000 0.95
16532 0.95
1816 0.95
23348 Percent Impervious=
ti Pipe Diameter
Length Of Pipe
Length Of Trench
Width Of Trench
Height Of Trench
Cross -Sectional Area Of Trench
Storage In Piping
Available Volume (40% voids)
" Amount Infiltrated during storm
Total Volume
Elevation Of Bottom Of Trench
Elevation Of SHWT
Overflow Elevation
Exfiltration Rafe / Drawdown
Reported Hydraulic Conductivity
..,
Bottom Surface Area
IDrawdown. i me
1.5 inches
0.65
Trench A JTrench B
Cc 0.70
CIF
67.0%
2
2
Feet
100
200
Feet
100
100
Feet
3.89
7.78
Feet
2.816
2.816
Feet
10.95
21.91
SF
314
628
CF
'627
1253
Cubic Feet
5855'
Cubic Feet
.:.:..,._.7735
Cubic Feet
41.29
Mean Sea Level
39
Mean Sea Level
43.79
Mean Sea Level
0.725 Cubic Feet Per Hour Per Sq Ft
778 Square Feet
21' hours
COMMENTS
" The overflow weir elevation is set at the top of the pipe, rather than the top of the trench. Per the supplement, the trench
height is 25.
Storage volume is deficient.
"Based on a 6 hour storm at an average rate of infiltration = .0009 cfsllinear foot of trench x 300 if trench x 21600 sect 6 hr

INFILTRATION TRENCH_ANALYSIS
Filename: S:IWQSIINTRENCH1000612.WK1
Project # 000612
Project Name Kinko's Retail Store
Recvng Stream Hewletts Creek
Drainage Basin Cape Fear
Site Area 0.8 acres
Impervious Area Calculation
Buildings
Parking/Asphalt
Concrete
Total
Volume/Storage Calculation
Required
Provided
Design Storm
RV
Volume to Store'°':
Date 06-Jul-2000
Reviewer Lewis
Classification SA
Index # 18-87-26
Drainage Are 34848 SF
0.80 Acres
1 Rational C
5000— 0.95
16532 0.95
1816 0.95 Cc 0.70
23348 Percent Impervious= 67.0%
1.5 inches
0.65
3060 CF Ce2hCa.,2��
Trench A JTrench B
Pipe Diameter
Length Of Pipe
Length Of Trench
Width Of Trench
Height Of Trench
Cross -Sectional Area Of Trench
Storage In Piping
Available Volume (40% voids)
Amount Infiltrated during storm
Total Volume
Elevation Of Bottom Of Trench
Elevation Of SHWT
Overflow Elevation
Exfiltration Rate / Drawdown
Reported Hydraulic Conductivity
Bottom Surface Area
Drawdown .Time.
COMMENTS
2
2 Feet
100
200 Feet
100
100 Feet
3.89
7.78 Feet
3.32
3.32 Feet
12.91
25.83 SF
314
628 CF
:705
14.10
Cubic Feet
Cubic Feet
7970':
Cubic Feet
41.13 Mean Sea Level
39 Mean Sea Level
44.45 Mean Sea Level
0.725 Cubic Feet Per Hour Per Sq Ft
778 Square Feet
3 hours
**Based on a 6 hour storm at an average rate of infiltration = .0009 cfs/linear foot of trench x 300 If trench x 21600 sec/ 6 t o.

5 C7//ey
DIVISION OF WATER QUALITY
INFILTRATION SYSTEM INVESTIGATION
1. The minimum bore depth:
�X yroUa� C' IvweS� Pt = 52
l�rC�fJ. boi" m
j � 2
S`
2. The type of soil:
5-7ni— GIB C�
3. The expected infiltration rate:
4. The depth to the Seasonal High Water Table:
5. Additional comments:
z;-fv
Signature of Regional Office Personnel:
4�1�
Linda Lewis, DWQ
Permit Application No.
S :1W QSISTORMW ATIFORMSIINFINV ST. FOR
Vincent Lewis, Soil Scientist
Date &,27�-CO