SW8960920_HISTORICAL FILE_19961112

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

EXISTING DITCH
1
1+
II �
to 36.0 RCP
II
' THE CAPE I, BOULEVARD �J:crs.,!'"�:2'.•7
:.7.}.F_,
OFFSITE
DRAINAGE l 1 I -I,-.4_t•_�,f` ?,. rlll II,II I I
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3.96 AC.
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r 1 27 I� / — J r r 1 !r �1 1v GREEN / GREEN
iF15
DRAINAGE / 20 r 24"RCP 7 r I
TO POND aft �' I r r ' ' , , rl�� CART PATH?
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APOROVED
/26,/ / /I or/ / NORTH CAROLINA; NVIRON'>t ENTAL
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ee
OCT 2 21996
TELFAIR SUMMIT PROJ D M ZD
STORMWAT R DETENTION
OFF —SITE DRAINAGE
z POVVDS # 18 2
SCALE: 1 200'

r
Exrsn,vc Dlrcx
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- - + re I I 3s' o RCP /
It
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It
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OFFSITE36"0 RCP "lII DRAINAGE
i
if l i
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3.93 AC.
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+ + ' / ,' S' � I 1 I I I ►►= ••' �• -�f1 /'
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! 1' 22 GREEN / GREEN
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DRAINAGE ! ��,rrrr^ + // 24" RCP
TO POND iR! ' 20 ,' + r ' /' ,' ,h'�j CART PAIN jir
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POND JV I
TELFAIRI�6
SUMMIT
_ i//
' 2Z.Z 22 I + e /',' '30,
• \ ' �, + ,'+1 t ,' LINKSIDER /,' /,' /!! ' '! , ''' /'/r"'APPROVED
////',30" .1, i is R,I'rl CAROL S"�F r''''rRCNMENTAL
22, /, '! , % - '/. '.' • ',' /MANAGEthr-
!sMSi Ca: QE ENWI' t ,�":.":U')ON
/ +21.0 /' / . �'� /�,' '� ; �26PWOEIJT,4L hIANAGEMENT
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E C E I V E
,Ill�ftl �I11 l
l2By,\ 1 I' ll lfl I t
' , 1 k ,% ,\,, { 1!l l,' yl 1 , !z OCT 2 21996
PAW 07q&
1 if
, I ♦ — f 1 /
TELFAIR SUMMIT
STORMWATER DETENTION
OFF —SITE DRAINAGE
TO PONDS * I & 2
SCALE: 1 200'

TELFAIR SUMMIT
STORMWATER DETENTION POND CALCULATIONS
RUNOFF CALCULATIONS - TELFAIR SUMMIT SITE
Impervious Surfaces:
40 units @ 2,100 SF each (includes option of covering decks and
front steps) = 1.93 AC.
Street and driveway paving (excludes section of Valley Brook Road
from Telfair's Creek to Building 20 which has no curb &
gutter) = 1.41 AC.
Impervious Surfaces (Onsite) = 3.34 AC -
Pervious Surfaces (Onsite) = 3.06 AC.
RUNOFF CALCULATIONS - OFF PROJECT SITE
Impervious Surfaces:
2 Buildings (7 -36' x 36' Blocks) in Linksider = 0.21 AC.
Driveways (3 single @ 440 SF; 5 double @ 880 SF) - 0.13 AC.
Street (3501 x 26'W) = 0.21 AC.
Cart Paths (1,430 LF x 7'W) = 0.23 AC.
Impervious Surfaces (Oftsite) = 0.78 AC.
Pervious Surfaces = 6.95AC.
STUB
POND SIZE CALCULATIONS:
4.12 AC. x 0.083' rainfall = 14,986 CF Q E C E I V E
x 10.01 A . ' rainfall x .2 _ 2 F � C • !i3 7 _ 3i C OCT 2 21996
Total Runoff Volume - 22,224 CF
PROD #5:,L}` °C(00
166,680 Gallons
Ponds #1 and #2 are interconnected to serve as a single detention pond (Ponds are
existing, side slopes are stabilized at approximately 2:1). S� -
Pond #1 area @ Storage Pool Elev. of 16.8' _ 29,795 SF .�
Pond #2 area @ Storage Pool Elev. of 16.8' = 19,994 SF '�" LAgOI
Total Storage Pool area of Elev. 16.8` = 49,789 SF
�LAL '
S.
SE/TSPOND - 1 ,
IofzL196

Pond #1 area @ Permanent Pool Elev. 16.3' = 28,075 SF
Pond #2 area @ Permanent Pool Elev. 16.3' = 18,750 SF
Total Permanent Pool Area at Elev. 16.3' = 46,825 SF
Average Pond Surface Area = 48,307 SF
22,224 CIF _ 48,307 CF = 0.46' Storage Depth Required
Percent Impervious Area = 4.12 AC. _ 14.13 AC. = 29.2%
Pond Depth = 6.0'
SA/DA % Required for 90% Solids Removal (See Chart) '= 1.6%
1.6% x 14.13 AC. = 0.23 AC. Require Pond Area
Permanent Pool Area = 1.07 AC.
Actual Pond Storage Volume - 0.5' Depth x 48,307 SF Average Area W 24,154 CIF
ORIFICE CALCULATIONS:
Use 2 1/2" 0 orifice for dewatering outlet
Calculate average discharge rate and time to lower orifice head from 0.5' to 0.4':
0.1' pond height x 48,307 Average Pond Area x 7.5 Gal/Ft3 = 36,230 Gallons Storage
Average head on orifice from 0.5' to 0.4' = 0.45'
Average discharge rate @ 0.45' head:
Q(GPM) = (449)c A 2gh
Q(GPM) = Volume discharged in gallons per minute
c = discharge coefficient = 0.6
A = orifice area in square feet
G = gravity = 32.2
h = head above center of gravity
Q(GPM) = (449)(.6)(0.0341) {2)(32.2)(0.45)
Q = 49.5 GPM
Time required to lower pond 0.1' @ 0.45' average head:
T = 36,230 Gal. _ 49.5 GPM = 731 minutes
49.5 GPM vs 731 minutes plotted on curve (see discharge curve).
Discharge rate and time to lower head from 0.4' to 0.3':
Q=43.6GPM
T = 36,230 Gal. _ 43.6 GPM = 831 minutes
43.6 GPM vs 1,562 minutes plotted on curve.
SEITSPOND - 2

Discharge rate and time to lower head from 0.3' to 0.2':
Q=36.9GPM
T 36,230 Gal. _ 36.9 GPM = 982 minutes
36.9 GPM vs 2,544 minutes plotted on curve.
Discharge rate and time to lower head from 0.2' to 0.1':
Q=28.6GPM
T 36,230 Gal. _ 28.6 GPM = 1,267 minutes
28.6 GPM vs 3,811 minutes plotted on curve.
Discharge rate and time to lower head from 0.1' to 0.00':
Q = 16.5 GPM
T = 36,230 Gal. _ 16.5 GPM = 2,196 minutes
16.5 GPM vs 6,007 minutes plotted on curve.
The outlet structure will discharge the total calculated runoff volume of 166,680
gallons in approximately 2.9 days (see Orifice Discharge Curve).
r �5SIO�ti1q"=
SEAL ;
898� •t
(D r2 Z 9(i
SEITSPOND - 3

so TE L F/M 5 JIB M I
29'2"Of ORIFICE DISCHARCF
44.5GPM,731-MIN sroRMYYArL�R DFrENripN -
q3.6 GPMl�5 -0 MIN
3 6, 9 G PM1354AL M►N
z8, bGPM�3Bl1 MIN 2,S'' � oRiFtc� t7rscl-��r�GEs
1(.6)6,90 GALS, CALCULArED
30 RUNOFF IN 2.9 DAYS
i I G,5 GPM cool MIN,
10
D4V*Y 3
�72, 5-00 GAL) &7J300 G,qt,)
I
0 30op 60OD 700D' -i a `•B0 04 90 DO
1 p 1000 20.0D 3000 i0 O
• f

TELFAIR SUMMIT
LOW DENSITY CALCULATIONS
NON CURB & GUTTER SECTION OF VALLEY BROOK ROAD
IMPERVIOUS SURFAQES:
Pavement (1,100 LF x 20'W) = 0.51 AC.
Site Area Impacted by Street = 16.96 AC.
0.51 _ 16.96 = 3.0% Impervious Area
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SEITSPOND - 4

SA/DA - 85% TSS REMOVAL WITH 30' VEGETATIVE FILTER
IMPER.% 3.OFT 3.5FT 4.OFT 4.5FT 5.OFT 5.5FT 6.OFT 6.5FT 7.OFT 7.5FT
10%
.9
.8
.7
.6
.5
20%
1.7
1.3
1.2
1.1
1.0
.9
.8
.7
.6
.5
30%
2.5
2.2
1.9
1.8
1.6
1.5
1.3
1.2
1.0
.9
40%
3.4
3.0
2.6
2.4
2.1
1.9.
1.6
1.4
1.1
1.0
50%
4.2
3.7
3.3
3.0
2.7
2.4
2.1
1.8
1.5
1.3
60%
5.0
4.5
3.8
3.5
3.2
2.9
2.6
2.3
2.0
1.6
70%
6.0
5.2
4.5
4.1
3.7
3.1
2.9
2.5
2.1
1.8
80%
6.8
6.0
5.2
4.7
4.2
3.7
3.2
2.7
2.2
2.0
90%
7.5
6.5
5.8
5.3
4.8
4.3.
3.8
3.3
2.8
.1.3
100%
8.2
7.4
6.8
6.2
5.6
5.0
.4.4
3.8
3..2
2.6
SA/DA - > 90% TSS REMOVAL
FOR WET DETENTION WITHOUT VEGETATIVE FILTER
IMPER A 3.OFT 3.5FT 4.OFT 4.5FT 5.OFT 5.5FT 6.0FT 6.5FT 7.OFT 7.5FT
10%
1.3
1.0
.8
.7
.6
.5
.4
.3
.2
.1
20%
2.4
2.0
1.8
1.7
1.5
1.4
1.2
1.0
.9
.6
30%
3.5
3.0
2.7
2.5
2.2 -
1.9
1.6
1.3
1.1
.8
40%
4.5
4.0
3.5
3.1
2.8
2.5
1.8
1.4
1.1
50%
5.6
5.0
4.3
3.9
3:5
3.1
2.7
2.3'
1.9
1.5
60%
'7.0
6.0
5.3
4.8
4.3
3.9
3.4
2.9
2.4
1.9
70%
8.1
7.0'
6.0
5.5'
5.0
.4.5
3.9
3.4
2.9
2.3
80%
9.4
8.0
7.0
6.4
5.7
5.2
4.6
4.0
3.4
2.8
90%
10.7
9.0
7.9
7.2
6.5
5.9
5.2
4.6
3.9
3.3
100%
12.0
10.0
8.8
8.1
7.3
6.6
-5.8
5.1
4.3
3.6
7ELFA)P- 5v/Y►017-

JOSEPH S. HILL, JIL AND ASSOCIATES
CONSULTING ENGINEERS and PLANNERS
1602 ILARBOIIR DRIVE
WILMINGTON, NORTH CAROUNA
TEL.1 PHOW 910.799-1544
October 22, 1996
Ms. Linda Lewis
N.C.D.E.M.
127 Cardinal Drive Extension
Wilmington, North Carolina 28405
Subject: Additional Information
Stormwater Project No. SW8 960920
Telfair Summit
New Hanover County '
Dear Ms. Lewis:
MAII ING ADDRESS:
POST OFFICE BOX 5592.STA. 1
WILMINGTON, NC 2W34155
S1111 T ink. 91-)� n P. 11 1419 41
, U 6 - "i � Tb� L�
E C E I V E
D
OCT 2`21996
P R 0 J #�� "[l 0Q70
In response to your letter, we submit the following additional information
regarding the Telfair Summit Stormwater Plan:
1. A topographic map with impervious areas clearly shown is enclosed.
Development of the off -site drainage areas is complete (Linksider at
The Cape and The Cape Golf Course).
2. The riser detail is revised to show 1.0' between the orifice and concrete
ballast.
3. A note is added to the plans requiring all rooftop drains be directed to
the pond.
4. Typical unit footprint is shown on building #6 with concrete steps and
covered deck noted. Due to differences in step dimensions only, all
left-hand unit are 2,040 SF, all right-hand units are 2,072 SF. 2,100 SF
was used in calculations as the typical unit rooftop area. Driveways are
16' wide, but length varies. Therefore driveways are included (area
calculations by planimeter) with street paving in impervious
calculations.
5. The permanent pool elevation of 16.3' and storage pool elevation of
16.8' were reversed in the originally submitted calculations. Corrected
copies of the calculations are enclosed.
6. Orifice size is increased to 2.5" 0.
7. Spot elevations and 6.0' depth contour (elevation 10.3') are shown for
the existing bottoms of the ponds.
8. A forebay is shown at the pipe inlet.
SEITSLEW IS2

Ms. Linda Lewis
Telfair Summit
October 22, 1996
Page 2
9. Buildings will be on pilings or elevated crawl spaces. With the street
drainage routed through gutters to the catch basin near building 13, the
small amount of driveway and front yard runoff can be routed around
the buildings as shown, as is typically done where buildings pads are at
or below street elevations.
Please contact me if you have any questions.
JSHlpat
attachments
Sincerely,
JOSEPH S. HILL, JR. and ASSOCIATES
a"�-5-`
Josep S. Hill, Jr., P.E.
SEITSLEWIS2

State of North Carolina
Department of Environment, Health, and Natural Resources
Wilmington Regional Office
James B. Hunt, Jr. DIVISION OF WATER QUALITY Jonathan B. Howes
Governor WATER QUALITY SECTION Secretary
October 10, 1996
Mr. Joseph Hill, P.E.
1602 Harbour Drive
Wilmington, North Carolina 28401
Subject: ADDITIONAL INFORMATION
Stormwater Project No. SW8 960920
Telfair Summit
New Hanover County
Dear Mr. Hill:
The Wilmington Regional Office received a Stormwater Management Permit Application for Telfair
Summit on September 25, 1996. A preliminary review of that information has determined that the
application is not complete. The following information is needed to continue the stormwater review:
1. Where is the 7.73 acres off -site area located. Three copies of a very dark, illegible map
where provided. Please provide a better map with contours and impervious areas clearly
shown. Also, -has the total build -out potential of the off -site runoff been taken into account?
2. The dimensions of the outlet structure do notadd up. If the orifice is at elevation 16.3, then
based on the 2.5' concrete ballast, and .5' to the orifice, the entire height of the box would
be 3.5' , not 4' . Please check and revise.
3. Note on the plans that all roof drains must be directed so that they drain to the pond.
4. Provide a typical unit footprint with dimensions, concrete areas, and wood decks noted.
5. The calculations report that the pond's surface area at 16.3 is more than the surface area at
16.8. Is this a mix-up?
6. The 2" orifice will draw down the pond in 5.8 days. Please revise and specify a larger
orifice.
127 Cardinal Drive Extension, Wilmington, N.C. 28405-3845 • Telephone [phone] • Fax [phone]
An Equal Opportunity Affirmative Action Employer

Mr. Hill
October 10, 1996
Stormwater Project No. SW8 960920
7_ Provide information on the existing bottom elevations of the ponds.
8. Construct a forebay prior to entering the pond without disturbing the pond any more than
you already propose.
9. I am a little concerned with the proposed drainage around Units 13, 14, and 15. It appears
that runoff will flow through front yards and drives prior to making it's way around and
between the units and sheet flowing into the ponds. I anticipate many calls about flooded
front yard, or water in people's houses.
Please note that this request for additional information is' in response to a preliminary review. The
requested information should be received by this Office prior to November 10, 1996, or the application
will be returned as incomplete. The return of a project will necessitate resubmittal of all required items,
including the application fee.
If you have any questions concerning this matter please feel free to call me at [phone].
Sincerely,
Ms. Linda Lewis
Environmental Engineer
JBBlarl: S:IWQSISTORMWATIADDINF01960920.00T
cc: Linda Lewis
Central Files
2

JOSEPH S. HILL, JIL AND ASSOCIATES
CONSULTING ENGINEERS and PLANNERS
1602 HARBOUR DRIVE
WILMINGTON, NORTH CAROUNA
TEI,I'PHONG 910-799.1544
September 23, 1996
Ms. Linda Lewis
N.C.D.E.M.
127 Cardinal Drive Extension
Wilmington, North Carolina 28405
Subject: Telfair Summit
Stormwater Management Plan
New Hanover County
Dear Ms. Lewis.
MAIUUQADDRESS:
POST OFFICE BOX 5592-STA. I
WILMINGTON, NC 28403-4155
e, " �.-�
SEp
Enclosed are three (3) copies of the Telfair Summit Stormwater Management
Plan. One (1) of the copies shows the drainage area to the stormwater pond in
colored ink.
Also included are two (2) copies each of the permit application, stormwater
calculations, erosion control calculations, operation and maintenance schedule, and a
check for the application fee of $385.00.
The plan proposes use of two existing ponds that will be interconnected to
serve as a single stormwater detention pond. All runoff from roof tops, driveways,
and curb and gutter streets is routed to the pond. Runoff from the section of Valley
Brook Road from Telfair's Creek to the beginning of the curb and gutter collection
system near building 20 will flow directly from the road shoulders into the adjacent
wetlands. Runoff from this street section is therefore not included in the detention
pond calculations.
Please review this plan as soon as possible.
Please contact me if you have any questions.
Sincerely,
JOSEPH S. HILL, JR. and ASSOCIATES
S,tka ,
JSHlpat Josep S. Hill, Jr., P.E.
attachments
SE/TSLEWISI