SW8060740_Historical File_20080130

,_ ..1 '6) Michael F.Easley,Governor
Uje \70
' , William G.Ross Jr.,Secretary
j T.1 North Carolina Department of Environment and Natural Resources
Coleen H.Sullins Director
;:a3 Division of Water Quality
January 30, 2008
Mr. Timothy J. Walter, Vice President
701 East Bay, Inc., General Partner
Port City Limited Partnership
201 N. Front street, Suite 314
Wilmington, NC 28401
Subject: Approved Plan Revision
Myrtle Grove Shopping Center
Stormwater Project No. SW8 060740MOD
New Hanover County
Dear Mr. Walter:
On January 30, 2008, the Wilmington Regional Office received a plan revision for Stormwater
Management Permit Number SW8 070740MOD. The revisions include replacement of an
earthen forebay (forebay#1, pond #2) with interlocking sheet piles. It has been determined
that a formal permit modification is not required for the proposed changes. We are forwarding
you an approved copy of the revised plans for your files. Please replace the old approved plan
sheets C4.1, C4.2, and C8.4 with the new ones.
Please be aware that all terms and conditions of the permit issued on March 19, 2007,
remain in full force and effect. Please also understand that the approval of this revision to
the approved plans for the subject State Stormwater Permit is done on a case-by-case
basis. Any other changes to this project must be submitted to and approved through the
Division of Water Quality prior to construction. The issuance of this plan revision does not
preclude the permittee from complying with all other applicable statutes, rules, regulations
or ordinances which may have jurisdiction over the proposed activity, and obtaining a
permit or approval prior to construction.
If you have any questions concerning this matter, please do not hesitate to call me at (910)
796-7215.
Sincerely,
L 114ce...,_
Chris Baker
Environmental Engineer II
ENB\csb: S:\WQS\STORMWATER\PERMIT1060740MODPR.jan08
cc: Robert P. Balland, P.E., Paramounte Engineering, Inc.
New Hanover County Building Inspections
Chris Baker
Wilmington Regional Office
Central Files
N�ifhCarolina
,Naturally
North Carolina Division of Water Quality 127 Cardinal Drive Extension Wilmington,NC 28405 Phone[phone] Customer Service
Wilmington Regional Office Internet: www.ncwaterouality.org Fax [phone]
An Equal Opportunity/Affirmative Action Employer—50%Recycled/10%Post Consumer Paper

'h MAR-21-2007 WED 03:22 PM NCDENR FAX NO. 9103502004 P. U8
State Stormwater Management Systems
Permit No. SW8 O6074OM0D
Myrtle Grove Village Shopping Center Page 1 of 2
Stormwater Permit No. SW8 060740MOD
New Hanover County
Designer's Certification
I,1? e r4} --P. j3kaktrof , as a duly registered k- ' in
the State of North Carolina, having been authorized to observe(periodical) eekly ull
time)the construction of the project,
ma r 4b2. GIALA4- v►1,11. �h oi4_____ -
(Project)
for gar Ct Ce,► 43j LTh Phr) (Project Owner) hereby state that,to the
best of my abil es, due care and diligence was used in the observation of the project
construction such that the construction was observed to be built within substantial
compliance and intent of the approved plans and specifications.
The checklist of items on page 2 of this form are a part of this Certification.
Nord deviations from approved plans and specifications:
A sht.e+p'L waL.0 wqc. iAtsM11 .( 4o creAvie elpa i*t amel no144o`
eof ed1 by+-rr• 44 pro/205*c( dvx. 46 Per s of 1 Co P-►ot 1 .0,4 . I.C. Loc„oJ+'oti
O. 4'4-L. sue- pile wkvl nr,,9.iu4 "s 4&t voi.."w„ LL,.;4s of ¢14. ,i'of. .
Signature�•t!~44, 7/ 52 �sok., CARo .i
Q� figs/ �iy%,
Registration Number 3/59/ 2�"rigs/
�9e 9
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Date 2Z88 _ 159
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Page 7 of 8

MAR-21-2007 WED 03:22 PM NCDENR FAX NO 9103502004 P. 09
State Stormwater Management Systems
Permit No. SW8 060740MOD
Certification Requirements: Page 2 of 2
✓ 1. The drainage area to the system contains approximately the permitted
acreage.
✓ 2. The drainage area to the system contains no more than the permitted
amount of built-upon area.
3. All the built-upon area associated with the project is graded such that the
runoff drains to the system.
✓ 4. All roof drains are located such that the runoff is directed into the system.
✓ 5. The outlet/bypass structure elevations are per the approved plan.
.✓ 6. The outlet structure is located per the approved plans.
✓7. Trash rack is provided on the outlet/bypass structure.
✓ 8. All slopes are grassed with permanent vegetation.
✓g. Vegetated slopes are no steeper than 3:1.
17 10. The inlets are located per the approved plans and do not cause short-
circuiting of the system.
11. The permitted amounts of surface area and/or volume have been
provided.
✓12. Required drawdown devices are correctly sized per the approved plans.
4713. All required design depths are provided.
All required parts of the system are provided, such as a vegetated shelf, a
/ forebay, and the vegetated filter.
✓ 15. The required dimensions of the system are provided, per the approved
plan.
cc: NCDENR-DWQ Regional Office
New Hanover County Building inspections
New Hanover County Engineering
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Page 8 of 8

State Stormwater Permit Application Tracking Cover Sheet
WilminL ion Reiional Office
Project Name: MYRTLE GROVE VILLAGE SHOPPING CENTER
Project Category: PR
Project Type: HD - DETENTION POND
App Accept Date: 1/30/2008
Application Fee Amt: $ is —
Fee Check Number: a SS 9 10
Reviewer Name: BAKER, CHRIS
Record the following information from RIMS after project has been entered!
Permit Number(RIMS): Swcd 0(.0140 W"t
Please update the SW Access System by entering the Permit Number for the project!
Date Entered in Access: 011,10 1)
Entered in Access By: 4 24 / gltr I
Date Printed: 1/30/2008 9:48:03 AM

pARATvitArou-N-TE
E N G ! N ? 'PRTF1
5 9 1 1 OLEANDER DRIVE , SUITE 2 0 1
W I L M I N G T O N , NC 2 8 4 0 3
9 1 0 - 7 9 1 - 6 7 0 7 ( O ) 9 1 0 - 7 9 1 - 6 7 6 0 ( F )
LETTER OF TRANSMITTAL
To: NCDENR Date 01/30/08
Re: Myrtle Grove Village:
Pond#2 Sheet Pile Revision
Attn: Chris Baker Project No. 06130.PE
IWe are sending: ®Originals ®Prints ❑ Shop Drawings ® Calculations
The following items: ❑ Correspondence ® Plans ❑ Specifications ® Other as listed below
Quantity Date Dwg.No. Description
3 01/30/08 24"x 36"Design Documents
1 Stormwater Narrative(Calculations)
1 $1,000 Check(#055910)
Issue.Status: ®For Approval ❑As Requested ❑Construction ❑Bid
❑ For Your Use El For Review and Comment ❑Approved as Noted ❑See Remarks
Action Takerni ❑ No Exceptions Taken ❑ Make Corrections Noted ❑ Amend&Resubmit
El Rejected-See Remarks El Approved as Submitted El Other
Remarks:
Cc: Signed: -L /g
Robert P. Balland, P.E.

MYRTLE GROVE VILLAGE
NEW HANOVER COUNTY, NC
STORMWATER NARRATIVE:
SHEET PILE REVISION
Prepared for:
Port City Central LTD. Partnership
701 East Bay Street
Charleston,SC 29403
Prepared by:
PARA $? PTcEmu
N GINEE .
5911 Oleander Drive,Suite 201
Wilmington, NC 28403
Project#06130.PE puau�„p44y,
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January 2008 :I
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MYRTLE GROVE VILLAGE
NEW HANOVER, NORTH CAROLINA
Project#06130.PE
Table of Contents
Design Narrative
Proposed Revision
Wet Detention Pond Calculations

MYRTLE GROVE VILLAGE
NEW HANOVER, NORTH CAROLINA
Project#06130.PE
PROPOSED REVISION
Port City Central LTD. Partnership is proposing to place a sheet pile in place of an earthen
berm for Forebay#1 of Pond#2 at the Myrtle Grove Village Shopping Center development.
During construction activities the earthen berm that separates Forebay#1 from the main pond
did not stabilize due to the intense inflow of stormwater against the berm;equalization
between the main pond and the forebay never occurred, resulting in the berm failure. In order
to complete the Forebay#1 our client proposes to construct a sheet pile in place of the earthen
berm for Forebay#1. All details, design drawings, and calculations relating to this revision can
be found in this submittal package.

WET DETENTION POND CALCULATIONS

Village at Myrtle Grove: Wet Detention Pond #2 Calculations (Sheet Pile MOD.)
NC DENR Retention Requirements
Objective:design a wet detention basin with the following characteristics:a permanent water pool depth between 3-and
6-feet, a surface area that meets TSS removal requirements(values set by NC DENR and included here), a forebay that
is approximately 20%of the total pond volume, a temporary water pool sized to detain the initial 1 inch of rainfall runoff an
outlet device that drains the temporary water pool within 2-5 days, and a length-to-width ratio of approximately 3:1.
Step 1: Determine the surface area required for 90% TSS removal
Post-Development Conditions
Total Drainage Area 42.01 ACRE Value from CAD
Impervious Drainage Area 32.27 ACRE Value from CAD
Impervious Cover 76.8% Impervious Cover=(Impervious Drainage
Area)/(Total Drainage Area)*100%
Elevation of Permanent Pool Surface 16.6 FT Value selected by designer
Depth of Permanent Pool 7.6 FT Value selected by designer
Elevation of Wet Detention Pond Bottom 9.0 FT (Bottom Elevation)=(Permanent Pool Surface
Elevation)-(Depth of Permanent Pool)
Approximate Pond Length 670 FT Value from CAD
Approximate Pond Width 140 FT Value from CAD
Length:Width Ratio 5:1 Ratio=(Length)/(Width):1
Required SA/DA Ratio for 90%TSS Removal 2.64 Value from chart. Reference: "90% TSS Removal
Required Permanent Pool Surface Area 48,311 SF Required Surface Area=(Required SA/DA
' Ratio)*(Total Drainage Area)
Provided Permanent Pool Surface Area 82,408 SF Interpolated value from stage-storage calculations
Step 2: Determine the 1-inch runoff elevation within the wet detention pond.
Runoff Coefficient, Rv 0.741 IN/IN Rv=0.05+0.009*(%Impervious)
Required 1"Runoff Volume(Volume of 113,051 CF 1"Runoff Volume=1 inch*Rv*1 foot/12 inch*(Total
Temporary Pool) Drainage Area)
Volume Below Permanent Pool 497,308 CF Value from stage-storage calculations(cumulative
pond volume at permanent pool elevation)
Total Volume to be Controlled 610,359 CF Total Volume to be Controlled=(Volume Below
Permanent Pool)+(1"Runoff Volume)
Stdrage Elevation at Required Volume 17.82 FT Value is interpolation based upon stage-storage
values. See stage-storage calculations
P:1Projects\ZIFF Properties106130.PE Village at Myrtle Grove\DocumentslDesign Calculations\Hydro\Stormwater Calcs\POND#2
Sheet Pile Modification\WET POND#2 Rev Sheet Pile.xls

Step 3: Calculate the required forebay volume(18-22%of total pond volume)and compare to the forebay volume provided.
Total Pond Volume 497,308 CF Value from stage-storage calculations
Required Total Forebay Volume 99,462 CF Forebay Volume=(Total Pond Volume)*20%
Provided Total Forebay Volume 110,850 CF Value from stage-storage calculations
Provided Forebay Volume:Total Pond Volume 22% (Provided Forebay Volume)/(Total Pond
Volume)*100%
Required Forebay#1 Volume(52%of Total DA) 51,720 Forebay#1 Volume=(Total Pond Volume)*10.4%
Provided Forebay#1 Volume(52%of Total DA) 73,159 Value from stage-storage calculations
Required Forebay#2 Volume(48%of Total DA) 47,742 Forebay#2 Volume=(Total Pond Volume)*9.6%
Provided Forebay#2 Volume(48%of Total DA) 37,691 Value from stage-storage calculations
Step 4: Verify that time required to drawdown the 1-inch runoff volume is within 2 to 5 days.
Diameter of Proposed Low-flow Orifice 4.00 IN Value chosen by designer
Elevation of Weir 18.60 FT Value chosen by designer
Total Elevation Head Above Orifice 2.00 FT (Total Elevation Head Above Orifice)=(Weir
Elevation)-(Elevation of Permanent Pool Surface)
(Average Elevation Head Above Orifice)=f(Storage
Average Elevation Head Above Orifice 1.00 FT Elevation at Required Volume)+(Elevation of
Permanent Pool Surface)J/2-(Storage Elevation at
Required Volume)
Cd, Coefficient of Discharge 0.60 Value chosen by designer
Q, Flowrate Through Low-flow Orifice 0.42 CFS Q=Cd*(Pi)*f(DlameterofOrifrce)*(1 ft/12
in)J^2/412*322*(Avenge Head)]"1/2
Drawdown Time for 1-inch Runoff 3.11 DAYS (Drawdown Time)=(1"Runoff Volume)/Q*(1
day/86400 seconds)
P:1Projects\ZIFF Properties106130.PE Village at Myrtle Grove\Documents\Design Calculations\HydrolStormwater Calcs1POND#2
Sheet Pile Modification MET POND#2 Rev Sheet Pile.xls

Village at Myrtle Grove (Sheet Pile MOD.)
Stage-Storage Calculations for Proposed Wet Detention Pond #2
determine the storage capacity and characteristics of the proposed wet detention pond.
Pond side slope above Permanent Pool 3
Planted shelf 2'below Permanent Pool 6
Side Slope below planted shelf 3
incremental and cumulative storage of the wet detention pond per contour interval.
Stage/Storage Above Permanent Pool(Including Forebay)
Cumulative
Contour Incremental Volume, S
Contour Area (SF) Volume (CF) (CF)
16.6 82,408 0 0 +Permanent Pool
17.0 92,371 34,956 34,956
18.0 97,534 94,953 129,908
19.0 102,903 100,219 230,127
20.0 108,250 105,577 335,703
21.0 113,080 110,665 446,368
P:1Projects\ZlFF Properties106130.PE Village at Myrtle Grove\Documents\Design Calculations\Hydro\Stormwater
CaIcs1PONC)#2 Sheet Pile Modification\WET POND#2 Rev Sheet Pile.xls

Village at Myrtle Grove (Sheet Pile MOD.)
Stage-Storage Calculations for Proposed Wet Detention Pond #2
Stage/Storage Total Pond (Including Forebay)
Cumulative
Contour Incremental Volume, S
Contour Area (SF) Volume (CF) (CF)
9.0 52,663 0 0 Pond Bottom
10.0 55,856 54,260 54,260
11.0 59,026 57,441 111,701
12.0 62,208 60,617 172,318
13.0 65,437 63,823 236,140
14.0 68,727 67,082 303,222
15.0 72,111 70,419 373,641
16.0 78,611 75,361 449,002
16.6 82,408 48,306 497,308 Permanent Pool
17.0 92,371 34,956 532,264
18.0 97,534 94,953 627,216
19.0 102,903 100,219 727,435
20.0 108,250 105,577 833,011
21.0 113,080 110,665 943,676
Forebay#1 (10.4%of Total Pond)
Cumulative
Contour Incremental Volume, S
Contour Area (SF) Volume(CF) (CF)
9.0 7,433 0 0 Bottom Elev.
10.0 7,950 7,692 7,692
11.0 8,496 8,223 15,915
12.0 9,066 8,781 24,696
13.0 9,669 9,368 34,063
14.0 10,313 9,991 44,054
15.0 10,977 10,645 54,699
16.0 11,657 11,317 66,016
16.6 12,153 7,143 73,159 i-Forebay Volume
Forebay#2(9.6%of Total Pond)
Cumulative
Contour Incremental Volume, S
Contour Area (SF) Volume(CF) (CF)
9.0 2,638 0 0 Bottom Elev.
10.0 3,144 2,891 2,891
11.0 3,711 3,428 6,319
12.0 4,325 4,018 10,337
13.0 4,980 4,653 14,989
14.0 5,674 5,327 20,316
15.0 6,417 6,046 26,362
16.0 7,222 6,820 33,181
16.6 7,812 4,510 37,691 •-Forebay Volume
P:1Projects\ZlFF Properties106130.PE Village at Myrtle Grove\Documents\Design Calculations\Hydro\Stormwater
Calcs\POND#2 Sheet Pile Modification\WET POND#2 Rev Sheet Pile.xls

PARA MOUNTE
E NI G I IV E. E F2 I NI G , 1 N G.
5 9 1 1 OLEANDER DRIVE , SUITE 2 0 1
W I L M I N G T O N , NC 2 8 4 0 3
9 1 0 - 7 9 1 - 6 7 0 7 ( 0 ) 9 1 0 - 7 9 1 - 6 7 6 0 ( F )
LETTER OF TRANSMITTAL
To: NCDENR Date 01/30/08
Re: Myrtle Grove Village:
Pond#2 Sheet Pile Revision
Attn: Chris Baker _ Project No. 061 30.PE
IWe are sending: ® Originals ®Prints ❑Shop Drawings ® Calculations
rile following items: El Correspondence ® Plans ❑ Specifications ® Other as listed below
Quantity Date Dwg.No. Description
3 01/30/08 24"x 36"Design Documents
1 Stormwater Narrative(Calculations)
1 $1,000 Check(#055910)
5wicO‘Oiblav►o.D
Issue Status: ®For Approval El As Requested El Construction El Bid
El For Your Use El For Review and Comment ❑Approved as Noted El See Remarks
'Action Taken El No Exceptions Taken El Make Corrections Noted El Amend&Resubmit
El Rejected-See Remarks El Approved as Submitted El Other
Remarks:
Cc: Signed:
Ro ert P. Balland, P.E.
received
�1 %noel 1