SW8040836_Historical File_20060831

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August 31, 2006
Mr. Jon Rosborough, Director
New Hanover County Airport Authority
1740 Airport Boulevard
Wilmington, NC 28405
Michael F. Easley, Governor
William G. Ross Jr., Secretary
North Carolina Department of Environment and Natural Resources
Subject: Approved Plan Revision
Wilmington International Airport Stormwater Master Plan
Stormwater Project No. SW8 040836
New Hanover County
Dear Mr. Rosborough:
Alan W. Klimek, P.E. Director
Division or Water Quality
On August 1, 2006, the Wilmington Regional Office received a plan revision for Stormwater
Management Permit Number SW8 040836. The revisions include the construction of 1.56
acres of built -upon area for the Locator Outer Marker project. After the construction of the
Locator Outer Marker projects, there will be 211.1 acres of built -upon area remaining for future
development. 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 Locator Outer Marker
project plans for your files. Please add these plans to the previously approved Master Plan
sheets. We are also forwarding an updated page 2 of the permit application. Please replace
page 2 of the November 24, 2004, application with the revised page 2, enclosed.
Please be aware that all terms and conditions of the permit issued on November 24, 2004,
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 approved through this Office 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)
796-7335.
Sincerely,
C�� od"
Linda Lewis
Environmental Engineer II
ENB\arl: S:\WQS\STORMWATER\REVISION\040836.aug06
cc: Greg Adams, Parsons
Beth Wetherill, New Hanover County Engineering
City of Wilmington Development Services
Tony Roberts, New Hanover County Building Inspections
Linda Lewis
One
Wilmington Regional Office NorthCaro ina
Central Files �Vaiural2Vj
North Carolina Division of Water Quality 127 Cardinal Drive Extension Wilmington, NC 28405 Phone [phone] Customer Service
Wilmington Regional Office Internet: www.ncwateraualitv.ore Fax [phone]
An Equal Opportunity/Affirmative Action Employer — 50% Recyoled110% Post Consumer Paper

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w
2. If this application is being submitted as the result of a renewal or modification to an existing perT
it, lis the
existing permit number F Q jsJ 8y o f� 3 (o and its issue date (if known) ! 1 0
..
3. Specify the type of project (check one):
✓ Low Density High Density Redevelop General Permit Other
4. Additional Project Requirements (check applicable blanks):
CAMA Major ►Sedimentation/Erosion Control 404/401 Permit _NPDES Stormwater
Information on required state permits can be obtained by contacting the Customer Service Center at
1-877-623-6748.
III. PROJECT INFORMATION
1. In the space provided below, summarize how stormwater will be treated. Also attach a detailed narrative
(one to two pages) describing stormwater management for the project.
2. Stormwater runoff from this project drains to the 0A PC F CA F <' River basin.
3. Total Project Area: d i (D 10, 6 acres
5. How many drainage areas does the project have? I
4. Project Built Upon Area: / %, a %
6. Complete the following information, for each drainage area. If there are more than two drainage areas in the
project, attach an additional sheet with the information for each area provided in the same format as below.
19Ver2%l 2 v^ izor I
Basin Wormation
.Drainage Area 1
Drainage Area 2
Receiving Stream Name
3 114 / -04 0 R EE 1,
S yr, it e.21c.
Receiving Stream Class
(?(S W
C S W
Drainage Area
G 2— 0. Ga Ci�S
/� �� $ OC
Existing Impervious* Area
.2 % -� , 5 &
Proposed Impervious*Area
/ , 5 & a crre S
$ 13 3
% Impervious* Area (total)
j 'J , 0 %, I1
q q�
Impervious* Surface Area
Drainage Area 1
Drainage Area 2
-On-site Buildings s-tkwC-A'"
g 2 2 3 sF
On -site Streets lacnes5 kvad3
0191 900SF
On -site Parking
1 050 sr
On -site Sidewalks wa l kwa ,
14 r- (o O SF
Other on -site , gravel ar7 Qy
J L1q 00 S r
Off -site
Total: 6,9 3 S F
Total:
Impervious area is defined as the built upon area including, but not limited to, buildings, roads, parking areas,
sidewalks, gravel areas, etc.
Form SWU-101 Version 3.99
Page 2 of 4

PARSONS
TSSC 111 Southern Region Office
100 Hartsfield Centre Parkway, Suite 540 a Atlanta, GA 30354 • [phone] • fax [phone]
July 31, 2006
Linda Lewis
Environmental Engineer
North Carolina Department of Environment and Natural Resources
127 Cardinal Drive Extension
Wilmington, NC 28405
Re: Response to Request for Additional Information
Stormwater Project No. SW8 040836
Wilmington International Airport Master Plan
New Hanover County
Dear Ms. Lewis:
Wl92
AUG O 1 2006
W
On behalf of the New Hanover County Airport Authority and the Federal Aviation
Administration, Parsons submits the enclosed documents, which have been revised to contain
the additional information that you requested in your letter dated July 27, 2006:
• Revised Stormwater Management Permit Application Form
• Revised Project Narrative
• Revised Plans
If you have any questions regarding these documents, please contact me at
[phone]. Thank you for your assistance!
Sincerely,
i
Jayne Park
PARSONS
Enclosures
Cc: Julie Wilsey, ILM
Greg Adams, Parsons
Project file, Work Release 78
TAProject FileAANI-3801078-Wilmington, NC ILMEnvironmentAStomwater PernritlCormspondence\Letter to Linda Lewis 7-31-06.DOC

RECEIVED
AUG 01 2006
DWQ
PROD # 3G 40
Stormwater Management Permit Application
Attachment 1- Project Narrative
Wilmington International Airport MALSR & ILS
ATTACHMENT I (REVISED 7/28/06)
PROJECT NARRATIVE
The Federal Aviation Administration (FAA) proposes to upgrade the navigation
system at the Wilmington International Airport by constructing, operating, and
maintaining a Medium Intensity Approach Lighting System with Runway Alignment
Indicator Lights (MALSR) for Runway 24 and an Instrument Landing System (ILS) for
both Runways 6 and 24. The MALSR and ILS would allow for increased navigational
capability to the airport during most weather conditions and assist incoming aircraft
during lowered ceilings.
PROJECT LOCATION
The Wilmington International Airport is located in New Hanover County,
approximately three miles northeast of Wilmington, North Carolina. The airport is
located on Airport Boulevard near the intersection of 23d Street and Blue Clay Road.
The airport has two runways, Runway 6/24 and Runway 17/35. Runway 6/24 is oriented
in a northeast -southwest direction (see attached plans).
The MALSR would be located at the end of Runway 24. Each ILS would consist of
three components, which would be located as follows:
• Localizer antenna - at the opposite end of the runway (for example, the
localizer antenna for Runway 6 is located at the Runway 24 end)
• Localizer shelter - at the opposite end of the runway that it serves
• Glide slope - at the end of the runway that it serves
The ILS for Runway 24 would include one additional component:
• Locator outer marker - The outer marker (including a non -directional radio
beacon) for Runway 24 would be located approximately 5.5 nautical miles
from the threshold of Runway 24 along the extended runway centerline,
southwest of the intersection of Farm Road and Sidbury Road in New
uanover County (see attached plans). A separate stormwater management
permit application has been submitted for this site.
1
T:IPROJECT FI1.EMANI-380,078-WII.MINGTON, NC ELMENVIRONMENTAUSTORMWATER PERMITISTORMWATER PERMIT
APPLICATIONWORMW ATER MGMT NARRATIVE - AIRPORT.DOC

Stormwater Management Permit Application
Attachment 1— Project Narrative
Wilmington International Airport MALSR & ILS
PROJECT CONSTRUCTION
Disturbed Land
The total area of disturbed land as a result of the proposed project would be 2.16
acres. This land would be disturbed for the following construction activities:
• Installation of buried electrical cables
• Construction of asphalt or gravel access roads, walkways, and parking areas
• Construction of concrete foundations or pads
• Placement of gravel around MALSR and ILS components
Built -upon Areas
The total area of built -upon areas as a result of the proposed project would be 1.56
acres. The built -upon land would consist of the following:
• Asphalt or gravel access roads, walkways, and parking areas to allow FAA
personnel to access equipment for maintenance
• Shelters for housing equipment
• Concrete foundations or pads for antenna towers and shelters
• Gravel -covered areas around antenna towers and other structures so that these
areas remain free of obstructions, such as vegetation
STORMWATER MANAGEMENT
The project areas are currently drained by overland sheet flow to grass -lined swales,
which convey stormwater off of the property. Construction of the project will result in
the addition of 1.56 acres of built -upon areas. The total area of disturbed land as a result
of the project will be 2.16 acres, while the allowable maximum of total built -upon area at
the airport is 486.2 acres (as of May 2006, there were 273.58 acres of existing built -upon
area, leaving 212.62 acres available for development).
All drainage will be conveyed through the existing grass -lined swales, and
sedimentation and erosion control practices will be used until a good stand of grass is
established in all disturbed areas. Specifically, silt fences will be installed between areas
of land -disturbing activities and any nearby ditches to treat sheet flow prior to it entering
the ditches (see attached plans). Temporary seeding and mulching will also be used in
disturbed areas where permanent seeding will not be immediately used.
T:\PROJECT FILEM\ANI-380\078-WII.MINGTON, NC IISIENVIRONMENTAL\STORMWATER PERMITISTORMWATER PERMIT
APPLICATION\STORMWATER MGMT NARRATIVE - AIRPORT.DOC

TOTAL AREA OF DISTURBED LAND AND IMPERVIOUS SURFACES
WILMINGTON INTERNATIONAL AIRPORT
WILMINGTON, NC
TOTAL FOR AIRPORT
Disturbed area
Impervious surface area
BREAKDOWN OF IMPERVIOUS SURFACE AREAS
buildings/structures
access roads
parking areas
walkways
gravel areas around structures
Total:
94,183 SF
2.1621 acres
ROUNDED TOI 2.16 acres
68,133 SF
1.5641 acres
ROUNDED TO:j 1.56 acres
14,223 SF
33,900 SF
1,050 SF
4,560 SF
14,400 SF
68,133 SF

AREA OF DISTURBED LAND AND IMPERVIOUS SURFACES
ESTABLISHMENT OF MALSR FOR RUNWAY 24
WILMINGTON INTERNATIONAL AIRPORT
WILMINGTON, NC
MAILS -1 threshold bar and 9 sets of five -light bars
threshold bar
270
19
5,130
1 five -light bar
28
19
532
1 five -light bar
28
19
532
1 five -light bar
28
19
532
1 five -light bar
28
19
532
1 five -light bar
28
19
532
1 five -light bar
28
19
532
3 five -light bars at 1,000 feet from threshold
84
19
1,596
Subtotal
9,918 SF
RAIL - 5 sequenced flashers
sequenced flasher
37
9
333
SF
sequenced flasher
37
9
333
SF
sequenced flasher
37
9
333
SF
sequenced flasher
37
9
333
SF
sequenced flasher
37
9
333
SF
Subtotal
1,665
SF
Main Asphalt/Gravel Access Road
Disturbed area
Impervious surface area
2,500 15 .375500 SF
2,500 10 25,000 SF
Four Gravel Walkways - from first four MAILS stations to existing access road
250
4
1,000 SF
250
4
1,000 SF
250
4
1,000 SF
250
4
1,000 SF
Subtotal
4,000 SF
Power & Controls Shelter - inc. in ILS
TOTAL
Disturbed area 53,083 SF
1.2186 acres
Impervious surface area 40,583 SF
0.9317 acres

AREA OF DISTURBED LAND AND IMPERVIOUS SURFACES
ESTABLISHMENT OF ILS FOR RUNWAY 24
WILMINGTON INTERNATIONAL AIRPORT
WILMINGTON, NC
Cable Trench (for both ILSs and MALSR)
Disturbed area 9100 1 9,100
Subtotal 9,100 SF
Impervious surface area 0 SF
Localizer Antenna Array - 7 pairs of antenna on concrete pad in gravel area
Disturbed area and impervious surface area
gravel area inc. antenna 134 30 4,020
gravel walkway 70 4 280
Subtotal 4,300 SF
Localizer Shelter -10 foot by 16 foot shelter surrounded by gravel with parking area and gravel access road
Disturbed area
Impervious surface area
gravel area inc. shelter 70 35 2,450 SF
gravel access road 200 15 3,000 SF
Subtotal 5,450 SF
gravel area (inc. shelter) 70 35 2,450 SF
gravel access road 200 10 2,000 SF
Subtotal 4,450 SF
Glide Slope - 10 foot by 12 foot shelter surrounded by asphalt parking area and apshalt access road
Disturbed area
gravel area (inc. shelter & antenna) 45 37 1,665 SF
asphalt parking area 35 15 525 SF
asphalt access road 170 15 2,550 SF
Subtotal 4,740 SF
impervious surface area
gravel area (inc. shelter & antenna) 45 37 1,665 SF
asphalt parking area 35 15 525 SF
asphalt access road 170 10 1,700 SF
Subtotal 3,890 SF
TOTAL
Disturbed area 72,574 SF
1.6661 acres
impervious surface area 61,624 SF
1.4147 acres

AREA OF DISTURBED LAND AND IMPERVIOUS SURFACES
ESTABLISHMENT OF ILS FOR RUNWAY 06
WILMINGTON INTERNATIONAL AIRPORT
WILMINGTON, NC
Localizer Antenna Arrav - 7 pairs of antenna on concrete pad in gravel area
Disturbed area and impervious surface area
gravel area inc. antenna 134 30 4,020
gravel walkway 70 4 280
Subtotal 4,300 SF
Localizer Shelter - 10 foot by 16 foot shelter surrounded by gravel with parking area and gravel access road
(inc. MALSR shelter)
Disturbed area
gravel area (inc. both shelters) 70 46 3,220 SF
gravel access road 350 15 5,250 SF
Subtotal 8,470 SF
Impervious surface area
gravel area (inc. both shelters) 70 46 3,220 SF
gravel access road 350 10 3,500 SF
Subtotal 6,720 SF
Glide Slope
10 foot by 12 foot shelter surrounded by asphalt parking area and asphalt access road
Disturbed area
gravel area (inc. shelter & antenna) 45 37 1,665 SF
asphalt parking area 35 15 525 SF
asphalt access road 170 15 2,550 SF
Subtotal 4,740 SF
Impervious surface area
gravel area (inc. shelter & antenna) 45 37 1,665 SF
asphalt parking area 35 15 525 SF
asphalt access road 170 10 1,700 SF
Subtotal 3,890 SF
TOTAL
Disturbed area 17,510 SF
0.4020 acres
Impervious surface area 14,910 SF
0.3423 acres

ATF9
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July 27, 2006
Mr. Jon Rosborough, Airport Director
New Hanover County Airport Authority
1740 Airport Boulevard
Wilmington, NC 28405
Michael F. Easley, Governor
William G. Ross Jr., Secretary
North Carolina Department of Environment and Natural Resources
Subject: Request for Additional Information
Stormwater Project No. SW8 040836
Wilmington International Airport Master Plan
New Hanover County
Dear Mr. Rosborough:
Alan W. Klimek, P.E. Director
Division of Water Quality
The Wilmington Regional Office received a plan revision for the existing Stormwater
Management Permit for Wilmington International Airport Master Plan on June 28, 2006, with a
scheduled Express Review date of July 26, 2006. This plan revision includes the Locator
Outer Marker (LOM) system. A preliminary review of that information has determined that the
application is not complete. The following information is needed to continue the stormwater
review:
Please complete the lower half of Section 111.6 on page 2 of the application by
revising the attached sheets (copied from the current permit file) to include the
BUA associated with the LOM system that is within the 1620.8 acre airport
property, excluding the BUA associated with the LOM system that is located off
Sidbury Road. The Sidbury Road site is 6 miles from the airport, and was not part
of the original 1620.8 acre project area, therefore, the BUA associated with it
need not be included on this application. Only that portion of the LOM system
that is located within the 1620.8 acre airport property need be listed on this
application. The BUA for the LOM system on Sidbury Road has been accounted
for in the stand-alone project under SW8 060662.
2. Due to the reduced size of the plans, the noted scale is off. It is now 0.9"=40'
instead of the original 1 °=20' or the reduced 1"=40'. Do you have the ability to
provide plans that are at a standard engineering scale?
Please note that this request for additional information is in response to a preliminary review.
The requested information should be received in this Office prior to August 11, 2006, 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 need additional time to submit the information, please mail or fax your request for a time
extension to the Division at the address and fax number at the bottom of this letter. The
request must indicate the date by which you expect to submit the required information. The
Division is allowed 90 days from the receipt of a completed application to issue the permit.
The construction of any impervious surfaces, other than a construction entrance under an
approved Sedimentation Erosion Control Plan, is a violation of NCGS 143-215.1 and is subject
to enforcement action pursuant to NCGS 143-215.6A.
1Vo°0 Carora' a
dvaiul��y
North Carolina Division of Water Quality 127 Cardinal Drive Extension Wilmington, NC 28405 Phone [phone] Customer Service
Wilmington Regional Office Internet: www.ncwa"uality.org Fax [phone]
An Equal Opportunity/Affirmative Action Employer — 50% Recycled/10% Post Consumer Paper

Mr. Rosborough
July 27, 2006
Stormwater Application No. SW8 040836 Mod.
Please reference the State assigned project number on all correspondence. Any
original documents that need to be revised have been sent to the engineer or agent. All
original documents must be returned or new originals must be provided. Copies are not
acceptable. If you have any questions concerning this matter please feel free to call me
at [phone].
Sincerely,
Linda Lewis
Environmental Engineer
ENB/arl: S:IWQSISTORMWATERIADDINFO120061040836.ju106
cc: Greg Adams, Parsons
Linda Lewis
Page 2 of 2

Wilmington International Airport
Stormwater Master Plan
Drainage Areas - Impervious Surfacing
Drainage Area
Number
Total Area -
Acres
Existing
Impervious
Area -Acres
Existing %
Impervious
1
8.2
1.9
23%
2
11.4
1.0
9%
3
115.1
9.7
8%
4
62.6
15.9
25%
5
53.9
3.5
6%
6
122.7
57.3
47%
7
57.5
17.6
31 %
8
121.6
22.1
18%
9
59.3
12.4
21 %
10
189.9
40.7
21 %
11
102.9
3.2
36/6
12
90.7
16.9
19%
13
207.0
46.0
22%
14
66.41
1.4
2%
15
63.2
3.0
5%
16
288.6
8.1
3%
Total, Existing
1620.8
260.E
16%
FUTURE: 1620.8 486.2 30%
D�2 1
1
Note: Area 16 represents airport land along Smith Creek below areas 3,4,5,6,7 and 8.

Wilmington International Airport
Stormwater Master Plan
Low Density Areas
Two Areas are proposed as Low Density areas.
"Low Density Stormwater management Area" - This area is cross hatched on Plan Sheet EX1.0.
Total Area:
1100
Acres
Existing Impervious Area
150
Acres
Existing Percent Impervious
14%
Maximum Additional Impervious Surfacing
180
Acres
Maximum % Impervious
30%
Drainage Area 9 - This area is depicted om Plan Sheet DA9.
Total Area:
59.3
Acres
Existing Impervious Area
12.4
Acres
Existing Percent Impervious
21 %
Future Impervious Surfacing Near Term
12.8
Acres
Future % Impervious
22%

PARSONS
TSSC III Southern Region Office
100 Hartsfield Centre Parkway, Suite 540 • Atlanta, GA 30354 • [phone] . fax [phone]�
June 26, 2006 C/, ��
Cameron Weaver A'0*1 �QvfsidA
Coordinator, Express Permitting
North Carolina Department of Environment and Natural Resources
127 Cardinal Drive Extension
Wilmington, NC 28405
Re: Stormwater Management Permit Applications
Wilmington International Airport (H..M), Wilmington, North Carolina
Dear Mr. Weaver:
On behalf of the New Hanover County Airport Authority and the Federal Aviation
Administration, Parsons submits the enclosed Stormwater Management Permit Applications
for the following projects:
Modification of the Wilmington International Airport (ELM) Master Plan
Stormwater Management Permit for installation of lighting systems for
Runway 6/24 within airport property
• New Stormwater Management Permit for construction of locator outer marker
at Sidbury Road site, approximately six miles northeast of the airport
Also enclosed is a check in the amount of $3,000, which covers the permit fees for each
of the projects: pia, r-ekAsI Cr
• $1,000 for express processing o modification f existing master plan permit
• $2,000 for express processing of new permit
If you have any questions regarding the application, please contact me at
[phone]. Thank you for your assistance!
Sincerely,
/r/ Z
Jayne Park
PARSONS
Y'Y
Enclosures'
Cc: Julie Wilsey, ILM
Greg Adams, Parsons =�
Project file, Work Release 78
TAProject FileAANI-380\078-Wilmington, NC RMEnvironmentahStormwater PenniACorrespondence\Letter to Cameron Weaver 6-26-06.DOC

PLC
& BR IGH T
MEMORANDUM
Date: February 7, 2006
To: File
From: Eric M. Stumph, P.E.
RE: Wilmington International Airport
Stormwater Master Plan
Stormwater Management — Phase I
AIP-34
TBI No. 3301-0305 & 0501
Subj.: Coordination Meeting at NCDENR
December 20, 2005, 10:00 AM
Sc,��U4U��Cd
3 2006
Attendees: NCDENR — Paul Bartlett, Linda Lewis, Ed Beck
New Hanover County Airport Authority - Whitney Prease, Julie Wilsey
Norris, Kuske & Tunstall - John A. Kuske, III
Talbert & Bright - Eric Stumph
Notes:
1. This meeting was called to resolve stormwater permitting issues for projects at the
Wilmington International Airport.
2. A Stormwater Master Plan for the Wilmington International Airport was completed
by Talbert & Bright in October 2004. Based on that Master Plan, NCDENR issued
10-year Stormwater Master Plan Permit No. SW8 040836 to the New Hanover
County Airport Authority on November 24, 2004.
3. Design documentation for the Stormwater Management — Phase I project at the
Wilmington International Airport, including Extended Dry Detention Basin No. 1 and
a stormwater conveyance pipeline, was completed by Talbert & Bright in May 2005.
Based on that documentation and the Master Plan Permit, NCDENR issued
Stormwater Permit No. SW8 050547 to the New Hanover County Airport Authority
on June 15, 2005. Project construction is complete.
4. The Stormwater Master Plan and the Stormwater Management — Phase I project were
developed using the April 1999 NCDENR Stormwater Best Management Practices
manual. Due to limitations associated with FAA wildlife hazard management
requirements, the extended dry detention and grassed swale BMP's were selected for
high density control at the Wilmington International Airport. The use of this BMP
ENGINEERING & PLANNING CONSULTANTS
WWW.TALBERTANDBR[GIJT.COM
4810 SHELLEY DRIVE WILMINGTON, NC 2840S 910.763.5350 FAX [phone]
WILMINGTON, NORTH CAROLINA • CHARLOTTE, NORTH CAROLINA : RICHMOND, VIRGINIA

Memorandum
Page 2
combination is expressly acknowledged in the Master Plan Permit. Series
implementation of the extended dry detention and grassed swale BMP's has been
contemplated using simple, linear addition of the assumed TSS removal efficiencies
listed in the BMP manual. Hence, one grassed swale in series with one extended dry
detention basin would have a total assumed TSS removal efficiency of 35% + 50% _
85%.
5. NCDENR is developing a new BMP manual to replace the current (April 1999)
manual. The latest draft of the new manual was issued for public comment in July
2005. The draft manual includes language which would prohibit linear addition of
BMP efficiencies. Instead, the draft manual would require computation of total
efficiency by a compounding method. To meet the 85% total efficiency requirement
would then require 3 extended dry detention basins in series, 3 grassed swales in
series with one extended dry detention basin, 5 grassed swales in series, or some other
equally impractical combination.
6. Design documentation for the General Aviation Apron Expansion project at the
Wilmington International Airport was completed by Talbert & Bright in July 2005.
The project involved a net increase in built upon surfacing of approximately 1.5
acres. The project drainage system intercepts flow from an additional 2 acres of
existing built upon area, for a total of 3.5 acres, to be discharged to Extended Dry
Detention Basin No. 1. Due to unique grading restraints for this project, it was
impractical to drain the pavement to a grassed swale. Therefore, a proprietary BMP
system was proposed for supplemental treatment in lieu of a swale. NCDENR
required that the BMP be sized to a TSS removal efficiency of 70%, in order to
achieve a total compounded efficiency of 85%. The New Hanover County Airport
Authority agreed to this requirement for this project because (1) the incremental cost
to upgrade the BMP from 35% to 70% efficiency was minimal (due to the relatively
small tributary area), and (2), the proprietary BMP represents a departure from the
Master Plan, which calls for the use of grassed swales. NCDENR issued Stormwater
Permit SW8 050801 for the project on August 12, 2005. Project construction is
complete.
7. Norris, Kuske & Tunstall is preparing design documentation for new general aviation
facilities (terminal building, hangars, and auto parking) and for expanded airline
terminal auto parking. The use of grassed swales for secondary stormwater treatment
is proposed for these projects, in accordance with the Master Plan. We understand
that, during initial pre -application consultations with NCDENR, Mr. Kuske was
advised that the use of grassed swales would not be acceptable, and that use of the
draft BMP manual would be required (including the compounding method of
computing total efficiency).

Memorandum
Page 3
8. Following discussion of the matter, Mr. Beck indicated that NCDENR would accept
grassed swales used in series with extended dry detention (with linear addition of
efficiencies) for projects at the Wilmington International Airport.
9. Please forward any corrections or additions to these notes to Eric Stumph at Talbert &
Bright.
C: Attendees

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