SW7061104_COMPLIANCE_20070130

STORMWATER DIVISION CODING SHEET
POST -CONSTRUCTION PERMITS
PERMIT NO.
SW'�11/P1/ z/
DOC TYPE
❑ CURRENT PERMIT
❑ APPROVED PLANS
❑ 'HISTORICAL FILE
I COMPLIANCE EVALUATION INSPECTION
DOC DATE
,Z�J^ZU l 3l7
YYYYMMDD

44 17e5lgn & eng1teentr, PC, R �T
f?0, 6ox 1470
Kitty Hawk, NC 27999
/'hone; (252) Z6/-B7/9, Cax; C252> 261-7970
January 30, 2007
DWQ
Surface Water Protection
943 Washington Square Mall
Washington, NC 27889
RIECIEVED
FEB 0 12007
�..�� �" R�,
RE: Stormwater Application of OBX I, LLC SW7061104
Six Single Family Residences in Nags Head, NC
Dare County
Dear Mr. Roger K. Thorpe:
Two copies of revised plans are being sent you for the referenced project. The plans and
calculations have been modified as follows:
I. Infiltration basins 2, 3, 4, 5, and 6 have been modified to provide storage for the first 1.5
inches of rainfall. Volume calculations are provided and the swale detail has been
modified.
2. Area #7 swale is located entirely within the drainage easement. It is shown on the plans
and in an additional detail.
3. Area #1 has an infiltration swale shown within the drainage easement and a detail has
been added showing that as well.
4. The ends of the swales should be closed and grade changes have been added to show this.
5. The property line swales are not evident on the plans however a detail is provided.
If you have any questions or need additional information please feel free to contact me at (252)
261-8714.
Sincerely,
Melissa A. McAllister, P.E.,

OBX I, LLC
BASIN INFORMATION
AREA
s.f.
AREA2
s.f.
AREA
s.f.
AREA4
s.f.
AREA5
s.f.
AREA
s.f.
AREA
s.f.
Receiving Stream Name
Roanoke
Sound
Roanoke
Sound
Roanoke
Sound
Roanoke
Sound
Roanoke
Sound
Roanoke
Sound
Roanoke
Sound
Recewing Stream Class
SA
SA
SA
SA
SA
SA
SA
Drainage Area
5,000
10000
10000
10000
10000
10000
5000
Existing Impervious Area
0
0
0
0
0
0
0
Proposed Impervious
1,555
2,820
3,175
2,840
3,085
2,999
1,555
%Impervious Area total
31.1%
28.2%
31.8%
28.4%
30.9%
1 30.0%
31.1%
IMPERVIOUS SURFACE AREA
On -site Building
810
1640
1555
1670
1555
1666
810
On -site Streets
0
0
0
0
0
0
0
On -site Parking
745
1180
1620
1170
1530
1333
745
On -she Sidewalks
0
0
0
0
0
0
0
Other On -site
0
0
0
0
0
0
0
Offsita
0
0
0
0
0
0
0
TOTAL COVERAGE
1,555
2820
3175
2840
3085
2999
1555
STORMWATER CALCULATIONS
SURFACE C
AREA 1
(s.f.)
AREA 2
(s.f.)
AREA 3
(s.f.)
AREA 4
(s.f.)
AREA 5
(s.f.)
AREA 6
(s.f.)
AREA 7
(s.f.)
ROOF 0.85
810
1640
1555.0
1670
1555
1666
810
CONCRETE 0.95
745
1180
1620
1170
1530
1333
745
VEGETATIVE FILTER 0.1
848
1696
1696
1696
1696
1696
E 848
COMPOSITE C
0.62
0.59
0.62
0.60
0.62
0.61
0.62
STORAGE VOLUME Q (cf): (Q=CiA)
Modified Rational Method
C = composite run off coef.
i = rainfall (1.5") in ft.
A =Area in s.f.
AREA 1
AREA 2
AREA 3 AREA 4 AREA 5 AREA 6 AREA 7
(cf)
(cf)
(cf) (cf) (cf)
(cn (cf)
REQUIRED 1 1851
3361
3791 3381 3681
357 185
PROVIDED:
SWALE VOLUME
12.5" deep 106' long 3:1 Jj/)p
460
460 460 460
460 �c
12" deep 106' long 3:1 318
318
FILTER INFILTRATION 1413
2827
2827 2827 2827
2827 1413
20 in/hr in one hour
TOTAL PROVIDED 1 1731
3287
3287 3287 3287
3287 1731
DRAWDOWN 1.5" EVENT (hrs) 0.13
0.12
0.13 0.12 0.13
0.13 0.13
�81PIE••��5��\
TOTAL
18,029
30.0%
9706
0
8323
0
0
0
18,029.0
Site Design023106 1/30/2007

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