SW8050322_COMPLIANCE_20051004

STORMWATER DIVISION CODING SHEET
POST -CONSTRUCTION PERMITS
PERMIT NO.
SW z
DOC TYPE
El CURRENT PERMIT
❑ APPROVED PLANS
❑ HISTORICAL FILE
OMPLIANCE EVALUATION INSPECTION
DOC DATE
WYYMMDD

INFILTRATION BASIN ANALYSIS
PROJECT NUMBER: SVV8050322
PROJECT NAME: Pine Grove Offices
DRAINAGE BASIN: 1
RECEIVING STREAM: Hew|ottsCmek
Index No.:
SITE AREA 1.36 acres
IMPERVIOUS AREA CALCULATION
BUILDINGS
PARKING/ASPHALT
CONCRETE
OTHER
96IMPERVIOUS, |=
ELEVATION OF SEASONAL HIGH WATER TABLE
REPORTED INFILTRATION RATE
SURFACE AREAS AND ELEVATIONS
FILENAME: O:\WO8\|NBAO|NVSVV8050323.WK1
DATE: 04-Oct-05
REVIEWER: R.Hall
CLASS: SA
If ORVV.issite within the 577AEC?
DRAINAGE AREA: �46.1' SF
Rational
8,051
14,520
2,531
Elev. (ft) Area, s0ft Inc. Volume AncVohume
BOTTOM 14.3 820
18.84 6.359 8175.86 8175,96
16.64 1.887 O 8175.96
TOP 18.84 1.867 0 8175.96
VOLUME /DEPTH / ORAWDOWN CALCULATION
DESIGN STORM, INCHES
DESIGN VOLUME
TOTAL VOLUME AVAILABLE
DEPTH OF RUNOFF
TIME TODRAWDOWN
25YEAR 24HOUR STORM NIA
Intensity, i=.33inches /hour
Or=CiA=
Opthrough the bottom of thobasin=
1OYEAR 1OMIN HIGH INTENSITY EVENT
Intensity, i=6.3inches /hour
Volume for 10yr. 18 min. evnnt=
COMMENTS
CUB|CFEET
CUBIC FEET
FEET
17.3 HOURS MUST 8E<12O
0.05 CF8
U13 CFS Must be>Qr
596.17 CF< 8175.98CF
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6f2212005 Pine Grove Offices Stormwater 04003
MBH Infiltration Basin
10-year Storm
WATERSHED DATA
Total Drainage Area
s . ft.
acres
59,461
1.37
Impervious Area
Land Use
s . ft.
acres
buildings
8,051
0,18
asphalt
14,528
0.33
concrete
2,531
0.06
0.00
Total
25,110
0.58
INFILTRATION SYSTEM:
Rv= 0.43 inlin
Design Rainfafl= 3
°% impervious = 0.422
= 42.2°%
say 42.2°%
CPRE = 0.25
CPOST = (°% imp.)(.95)+(1-°% imp.)(.25)
= 0.55
12 = 5.06 inlhr
110 = 6.30 inlhr
125 = 7.13 inlhr
Volume of first three inches of runoff = (Design rainfall)(Rv) (Drainage Area)
V=
6,393
cu-ft
Basin 1 Volume provided:
(L'W'D')
Area (st)
Elevation(ft)
V, =
6,316
cu-ft
Bottom:
293
14.00
Flood:
4,492
16.64
Basin 2 Volume provided:
(L'W'D')
Area (so
Elevation(ft)
V2 =
1,806
cu-ft
Bottom:
336
15.00
Flood:
1,867
16,64
Total Volume provided:
VT =
8,123
cu-ft
DRAWDOWN RATE:
RATE OF INFILTRATION 9 INIHR
DEPTH OF BASIN: 24 IN
DRAW DOWN RATE: 2.67 HRS
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OCT 04,2005 03:05P Tripp Engineering 9107635631 page 2
sWg os-asczz
10/04/05
Stormwater Narrative
Pine Grove Offices
New Hanover County, NC
TE04003
The Pine Grove Offices site is a 1.36-acre tract proposed for a veterinary office. Proposed
impervious areas include 8,051 SF of building, 2,531 SF of sidewalk, and 14,528 SF of asphalt
fora total of 25,110 SF. The total percent impervious is 42.4%. .
The stormwater runoff will be treated with an infiltration basin. The infiltration Pond will be
designed to meet the states 3" and the City's 10-year pre -post requirement. Outflow from the
pond drains to Hewlett's Creek, classification SA.

6l2212005 Pine Grove Offices Stormwater 04003
MBH Infiltration Basin
10-year Storm
WATERSHED DATA
Total Drainage Area
s . ft.
I acres
59,4j6
1.37
impervious Area
Land Use
s . ft,
acres
buildings
8,051
0.18
asphalt
14,528
0.33
concrete
2,531
0.06
0,00
Total
25,110
0.58
INFILTRATION SYSTEM:
Rv= 0.43 inlin
Design Rainfall= 3
% impervious = 0.422
= 42.2%
say 42.2%
CPRE = 0.25
CPOST = (% imp.)(.95)+(1-% imp.)(.25)
= 0.55
12 = 5.06 inihr
110 = 6.30 inlhr
125 = 7.13 inlhr
Volume of first three inches of runoff = (Design rainfall) (Rv) (Drainage Area)
V= 6,393 cu-ft
Basin 1 Volume provided: (L'W'D') Area (so Elevation(ft)
V, = 6,316 cu-ft Bottom: 293 14.00
Flood: 4,492 16.64
2 Volume provided. (L'W'D') Area (so Efevation(ft)
V2 = 1,806 cu-ft Bottom: 336 15,00
Flood: 1, 867 16.64
Total Volume provided:
VT = 8,123 cu-ft
DRAWDOWN RATE:
RATE OF INFILTRATION 9 INlHR
DEPTH OF BASIN: 24 IN
DRAW DOWN BATE: 2.67 HRS
CQ
= a O 4
SEAL
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