20090430 Ver 1_More Info Received_20090807

w y
WL
community infra
August 7, 2009
structure consultants
Ms. Cyndi Karoly
Division of Water Quality
401 Wetlands Unit
2321 Crabtree Blvd., Suite 250
Raleigh, NC 27604
01- D%k 3o
AUG 7 2009
OENR - WATER QUALITY
WETLANDS AND STORMWA7MRE: Response to NCDWQ Comments on 401 Water Quality Certification Application for
Johnston County Airport Runway Safety Area and Corporate Area Development
Dear Ms. Karoly:
Attached to this letter is Addendum #1 and Addendum #2 for Individual 401 Water Quality
Certification. These addenda address DWQ and USACE Public comments; also attached are revised
project plans, stormwater plan, and fill slope analysis. These documents are also being submitted to
the US Army Corps of Engineers.
During the review process to address agency comments several minor revisions were made to the
project plans that affected jurisdictional impacts. The table below reflects these changes.
Site Feature Excavation Fill Total Change
RSA Perm. Riparian Wetland (acres) 0.18 7.55 7.73 -1.11
RSA Temp. Riparian Wetland None 0.17 0.17 +0.05
Corp. Area Non-Riparian Wetland (acres) None 10.31 10.31 None
RSA Stream (linear feet) None 685 685 -94
RSA Buffer Zone 1 (square feet) 653 43,843 44,496 -3,971
RSA Buffer Zone 2 (square feet) 149 28,325 28,474 -2,185
am hopeful that these addenda satisfy your comments. Please contact me if you have any questions
regarding this submittal ([e-mail]). Thank you for your prompt attention to this
important aviation project.
Sincerely,
W.K. Dickson & Co., Inc.
Daniel Ingram
Project Scientist
cc: Thomas Brown, USACE
Ray Blackmon, Johnston County Airport
Carroll Triplett, WK Dickson
Chastity N. Clark, NCDOA
Project file, 80324.00.CA
C #r [Rive
? .3 ? ? .. +b {,{:{7111 a1'It?`?
0
of -o43o
Addendum #1
Response to N CD W Q Comments
RR&TOWL-4DO
AUG 7 2009
DENR • WATER QUALITY
WETLANDS AND STQRMNATER BRANCH
40 Prepared For:
Johnston County Airport Authority
3149 Swift Creek Road
Smithfield, NC 27577
Phone [phone]
Fax [phone]
Prepared by:
WK Dickson & Company, Inc.
720 Corporate Center Drive
Raleigh, NC 27607
Phone [phone]
Fax [phone]
August 2009
0
•
This Addendum #1 addresses comments by NCDWQ on the Johnston County Airport
Extended Runway Safety Area and Corporate Are Development Application for 401
Water Quality Certification (DWQ Project #09-0430). The Application was submitted
April 15, 2009 and NCDWQ comments were received on June 15, 2009. Specific
NCDWQ comments are addressed below.
1. Comment: Please re-submit your site plans on full plan sheets at a scale no
smaller than 1 "= 50" with topographic contours shown.
Response: Five sets of the requested full-size plan sheets are included.
2. Comment: Please provide cross section details showing the provisions for
aquatic life passage
Response: The requested detail is shown on Sheet C-15 of the plan set. The
proposed triple box culvert system will provide for aquatic life passage by burying
the center box culvert to convey the base flow. The two adjacent barrels will
convey high flows. The table below details the proposed culvert slope and invert
elevations, and existing stream bed slope and elevations.
Upstream Downstream Percent Slope
Elevation> Elevation ft
Existing Bed 138.89 136.94 0.250
Proposed 135.65 134.49 0.187
Culvert
Buried 3.24 2.45 NA
Depth
3. Comment: Please indicate all stream impacts including all fill slopes,
dissipaters, and bank stabilization on the site plan.
Response: The requested impact call-outs for the Runway Safety Area are
shown on sheets C-7 and C-10 of the plan set.
4. Comment: Please indicate all wetland impacts including fill slopes on the site
plan.
Response: The requested impact call-outs for the Corporate Area are shown
on sheets C-0, C-8, and C-9 of the plan set. The requested impact call-outs for the
Runway Safety Area are shown on sheets C-7 and C-10 of the plan set.
5. Comment: Please enumerate all riparian buffer impacts on the site plan and
clearly label impacts.
9

Response: The requested impact call-outs for the Runway Safety Area are
shown on sheets C-7 and C-10 of the plan set.
6. Comment: Please locate all isolated or non-isolated wetlands, streams, and
other waters of the Sate as overlays on the site plan.
Response: All waters of the State are shown on the site plan. In addition
Sheet C-24 has been added to the plan set which shows the Waters of the US
delineation across the entire Airport property. There are no isolated wetlands on
the Airport property.
7. Comment: Per the requirements of GC 3705, this project must comply with
Stormwater Management Plan (SMP) Requirements for Applicants Other Than
The North Carolina Department of Transportation. Please include an SMP that
removes a minimum of 85 percent TSS and 30 percent TN from the stormwater
generated by this project. For each proposed BMP, please provide a completed
BMP Supplement Form, with the required items.
Response: The Stormwater Plan and BMP design provided with the original
permit application has been substantially revised to comply with the Neuse Basin
Nutrient Rules. The revised Stormwater plan is attached. The proposed BMPs are
shown on sheet C-13 of the plan set.
8. Comment: Please provide a Compensatory Mitigation Plan. The Plan must
conform to the requirements of 15A NCAC 2H .0500 and must be appropriate for
the type of impacts proposed.
Response: On-site mitigation was investigated but was determined to be not
allowed by FAA guidelines due to the proximity to aircraft operations. Offsite
mitigation was investigated during the NEPA process but no suitable sites were
located that satisfied all mitigation needs. Therefore, purchase of mitigation
credits is the most feasible method available to provide for the mitigation needs.
The Applicant intends to utilize a commercial mitigation bank and/or the NC
Ecosystem Enhancement Program to satisfy wetland, stream, buffer, and nutrient
mitigation needs. All mitigation credits purchased will be appropriate for the
types of impacts proposed. The specific mitigation provider has not been
identified. NCDWQ will be notified when a mitigation provider is identified.
The Table below details the expected mitigation credit requirements.

•
Proposed Mitigation Credits
- Proposed Impacts

Impact Type
ERSA Corporate
Area Credit
Ratio Total
Credits
Riparian Wetland 7.73 ac 2 15.46
Non-Riparian Wetland 10.31 ac 2 20.62
Buffer Zone 1 44,496 sf 3 133,488
Buffer Zone 2 28,474 sf 1.5 42,711
Stream 685 If 2 1,370
Nutrient (Nitrogen) 92.66 Ibs 30 (years) 2,779.8
9. Comment: Please verify that herbicides will not be used within Waters of the
State.
Response: No herbicides will be used within waters of the State. A General
Note has been added to Sheet C-3 stating this.
10. Comment: Per the Requirements of the Neuse River Riparian Buffer Rule, you
must show that this site meets diffuse flow requirements with a level spreader or
other BMP per Chapter 8 of the BMP Manual. Please label all level spreaders
clearly on the site plans.
Response: The stormwater BMPs have been redesigned significantly from the
initial Application. The attached stormwater plan details the plan as it relates to
the Neuse River rules and diffuse flow requirements.
11. Comment: The description for Alternative 2 for the Corporate Area states that
a bridge or culvert will be necessary to cross Reedy Branch, but the cost estimates
in Table 10 do not indicate whether a bridge or culvert is used to determine the
road costs. Please provide cost estimates for both scenarios.
Response: The original Alternative 2 cost estimate assumed a bridge over
Reddy Branch to replace the existing bridge on Swift Creek Road. A cost estimate for a
culvert option has been developed. A revised Table 10 is provided below that includes
current cost estimates for all Corporate Area scenarios.
E
1]
Table 10. Summarv of Construction Cost Estimates for "Build" Alternatives
Cost Item Alternative 1 Alternative 2 Alternative 2 Alternative 3 Alternative 3
culvert bride culvert (bridge)
Grading, drainage,
erosion control, and $5,040,598 $3,215,075 $3,666,415 $9,343,109 $8,768,949
other site work
Roads (major access and
relocations None $2,605,200 $10,986,000 $1,153,500 $6,663,500
Paving (hangars, aprons,
taxiways) $2,009,205 $2,116,050 $2,116,050 $2,659,525 $2,659,525
Hangars $7,384,800 $7,384,800 $7,384,800 $7,384,800 $7,384,800
Wetland, Stream, and
buffer mitigation $886,660 $449,057 $172,000 $455,724 $53,680
Land acquisition and
residential relocation None $1,930,500 $1,930,500 $189,300 $189,300
Fencing None $42,000 $42,000 $54,000 $54,000
Engineering and
Contingencies
,349,533
$2
$2,661,
403 $3,944,665 $3,185,994 $3,866,063
Total $17,670,796 $20,404,085 $30,242,430 $24,425,952 $29,639,817

E
f
?o
-- ry ' --°>
LLJ
? 00,1 ° a

W
Z
_
J U
Z
} Q

z

0 z

Q
m z

Q
m
It

V

Z

O
m m
D

W
D

0

z
?
W
J d
U
W

o U)

LL.
O
IN-
M
J

L
O
H
m
J

i
Z
O
af
LWi
lL
N

Lli
Z
O
w
LWi
LL O
Q

H

0
z
H
N W
LL

m
J
Z
O
H
0
m
I') m W Q

J

I
•
I I
I
I
I
O
m
I

?
I

I I
I
I
I
I
;

O_ lo?
n
W
d
o
-i
W
N

?

N

Q

0

t\

?i
N
0
r

d•

It

c
It

O

N

U

0 O

cD

L
J

LO
tmp

H
U

a W
a_
o
J V) }
(n W LL- Li. U
U (n Ln
W 0
F- - Q C 0 Li
Q 0 J

f? O In
't N 00
(DD

W
N
W W

? O O Y
Q N N 0
0
w
C-) a w a
? ?
a: of
~
m m w v
i
8 w
W O
w u
o ?
Z
0
ap?
?zz
a ?
'--142 .._,,,,,•_
\ l
I f '------ too

LLI V)
I/
W () Y
Q Q .-
J m
I J LLJ
LLI
oN oQ
VIo U)
LL.
4 LLJ
o
Qco

Z

C) Lki
Q J
c, z
2J Io
ti
Z
\ W I
O ?LLI
Q
LLJ ?i1Q l O N(!)

\??O
Q
W ss
\ Q I
?wma
o Q z? \
L
) -J
?Q°
- - W
•
?W . L
I
mQ

I
D? W
zLi ° II
0 V o Of
N Z I
0 I N Q ?
p
W
Op I
W
Z

O •-

W, LZ

Q00

?
NQ I N` ZO
U-Q? I L
D (r a- LL. LL.
r-
r
-'? -'
CM ir
D V)
z 0-
x <
W J /
m, Ilr l
E v- r
H
M O z
X
W ? O

W _
Q
Q
U
?
O ?
W ~ z

V
5 I-
O
o o? z
V) Z
W
z U)
Q =
0 N
?!oroN
a
aw?y ffi$
t1 ?
E
S
.2 Y
p
33?
o
Y
al

•
Addendum #2
•
Response to USACE
Public Notice Comments
RIE&EBY91
AUG 7 2009
DENR • WAtER Q?AU'fY
WEMNpS ANp StORMWATM BRANCH
Prepared For:
Johnston County Airport Authority
3149 Swift Creek Road
Smithfield, NC 27577
Phone [phone]
Fax [phone]
Prepared by:
WK Dickson & Company, Inc.
720 Corporate Center Drive
Raleigh, NC 27607
Phone [phone]
Fax [phone]
August 2009
0
•
This Addendum #2 addresses USACE public comments on the Johnston County Airport
Extended Runway Safety Area and Corporate Area Development Application for 404
Individual Permit (action ID: SAW-2009-00846). The Application was submitted April 6,
2009, the public notice was issued on May 15, 2009, and comments were received from
USACE on June 25, 2009. Specific comments are addressed below and are grouped by
commenting party.
David and Grace Knox
3147 Swift Creek Road
Clayton, NC 27520
919-934-0920
1 A. Comment: What are the plans for handling the increased traffic on Swift Creek
Road by the entrance to the airport?
Response: - The construction of the Runway Safety Area (RSA) will not increase
air or ground traffic other then would have occurred without the construction of the
RSA. The Corporate Area may increase the traffic on Swift Creek road by several
vehicles per hour. The expected traffic flow contributed by the airport was
estimated to total approximately 80 vehicles (40 in each direction) in the year 2007 •
and is projected to increase to 198 by 2027 (99 in each direction). The Average
Daily Traffic count as surveyed by NC DOT Traffic Survey Group in 2007 indicated
that Swift Creek Road had approximately 2,600 vehicles per day. The capacity of a
rural two lane road is approximately 2000 vehicles per hour (1000 vehicles per
hour in each direction). Swift Creek road will not have to be widened to
accommodate the expected traffic generated by the airport and no properties are
expected to be acquired along the road opposite the airport property. The
projected contribution of approximately 199 vehicles by 2027 will not meet or
exceed the capacity of the roadway.
143. Comment: Will there be a new terminal built to take care of the increased fly-
in traffic?
Response: A new terminal is planned to replace the existing terminal at some
point in the future. This was initially estimated to occur in Stage 1(first 5 years) of
development, but due to budgetary considerations and additional planning needed
to provide this facility it will likely not be considered until Stage 2 (5 to 10 year
timeframe). The proposed terminal is not planned as a result of increased traffic,
but rather to replace an aging facility which is currently in need of repair and is
inadequate to satisfy the demand of current users. In time, the existing facility will
be in need of significant renovation and expansion. Replacing the terminal is
generally a wiser investment and use of funds. The terminal will be sized to
accommodate demand for a 20 year period.
U
•
2 A. Comment: The trees on this area (Corporate Area) have been a great noise and
wind buffer. Some 15 or so years ago, all the trees were removed and the wind
and noise increased tremendously. Now the forest is back, here we go again.
Response: The proposed hangars are generally used less then twice per day,
once when an aircraft departs and once when it returns. The proposed hangars are
not expected to house commercial operations which may have repeated departures
and arrivals during the day (i.e. flight ambulance service). The activity levels and
types of aircraft using the facility (C-II) fall below the Federal Aviation
Administration guidelines for a detailed noise analysis. The Environmental
Assessment (September 2003), page D1 and the FONSI (September 12, 2004), page
4, address this issue:
Environmental Assessment - "The projects discussed in this assessment are
not going to alter any airport noise patterns that exist or that have been
previously documented. Further, FAA Handbook 5050.4A states that "no
noise analysis is needed for proposals involving design Group I and II
airplanes on utility or transport type airports whose forecast operations in
the period covered by the environmental assessment do not exceed 90,000
annual propeller operations, or 700 annual adjusted jet operations."
Forecasts presented in Section A depict forecast jet, and overall operations,
• for the Airport. Johnston County is not expected to exceed 90,000 annual
operations, nor is it expected to exceed over 700 jet operations. The jet fleet
operations at Johnston County Airport must be adjusted for Cessna Citation
500 and Learjet 35, or equivalent aircraft, operations. According to FAA
Handbook 5050.4A, these two aircraft are quieter than many propeller
driven aircraft and are to be counted as propeller operations. Once jet
operations for the Airport are adjusted by type aircraft, adjusted jet
operations are below the requirements for a noise analysis. A Noise Contour
Map for the year 2016 was presented earlier as Exhibit C-1. Operations
counts and fleet mixes used to determine the Noise Exposure Contour were
presented earlier in Table A-2.'
FONSI - "A detailed discussion of noise, and the potential related impacts
took place in the EA and will not be repeated here. Therefore, it may be
assumed that there will be no significant noise impacts."
The "Land Use Plan - Year 2016" (Exhibit C-1) presented in the EA shows the Knox
property in LUG ZONE - A, with an average day-night sound level of 55 dB and
less. This zone is labeled as having "clearly acceptable noise level, no special
considerations required."
2$. Comment: Does the Airport Authority anticipate obtaining properties across
Swift Creek Road for future expansions of airport property?
0
•
Response: There are no plans to acquire any property on Swift Creek Road
opposite the airport for future expansion.
Larry and Rhonda Hicks
620 Ogburn Road
Smithfield, NC 27577
919-880-4669
1. Comment: We are greatly concerned about the flood impact on our
property ...I would like to see a proposed flood elevation increase and runoff
impact on downstream properties.
Response: The RSA is anticipated to impact 8.84 acres of riparian wetland and
779 linear feet of stream. The development of the Corporate Area will impact
approximately 10.31 acres of non-riparian wetland. The RSA consists of an
embankment and triple box culverts are over the existing floodplain at Reedy
Creek. The culverts are sized to pass the 100-year flood without causing flooding
upstream. The embankment and culverts will back up flows in the larger flood
events (greater than the 100-year flood) and reduce flows on the downstream side
of the Airport (i.e. Hicks property). The embankment will be grassed with no
increase in impervious surface. The RSA will not increase peak flows experienced
downstream of the airport. The proposed Corporate Area development will
increase impervious surface and stormwater runoff. To offset increases to peak
flows a large bioretention pond and dry pond will be constructed. These ponds
will attenuate flows to below pre-project conditions. As with the RSA, the
Corporate Area development will not result in increases to flooding for downstream
properties. The attached revised project plans and stormwater plan detail the
proposed stormwater controls.
2. Comment: I am requesting a public hearing and information on any flood
study changes and an environmental impact statement relevant to the affect (sic)
on my property and wildlife.
Response: During the NEPA process an advertisement for a public hearing was
published in the Smithfield Herald. No requests for a public hearing were received
regarding the improvement projects and any related effects. Mr. Hick'sconcerns
regarding potential flood impacts and environmental impacts have been adequately
addressed in the Environmental Assessment (September 2003), Finding of No
Significant Impact (September 2004), Application for 404 Individual Permit (April
2009), and this addendum and revised project plans (August 2009).
F_ 7
f?
•
NC Division of Water Quality
401 Oversight/Express Review Permitting Unit
2321 Crabtree Boulevard
Raleigh, NC 27604
919-733-1786
Comment: Please explain how your stated "need" is for "larger planes" to be
accommodated and increased business aircraft? What is your stated purpose for
the project?
Response: This project is not designed to accommodate larger planes than
currently operate at the Johnston County Airport. There is no runway extension
associated with the requested action. The project consistsof an "Extended Runway
Safety Area" (RSA) which is a non-paved area 500' wide and 1000' long beginning
at the end of the paved surface and extending outward from the runway end. The
purpose of this RSA is to provide a grassed-stabilized overrun to support an aircraft
in the event of the aircraft either under shooting or over shooting the paved surface
of the airport to minimize potential injury to people and damage to the aircraft.
The RSA is required by the Federal Aviation Administration as a fundamental safety
improvement at all airports that accommodate jet aircraft in the C II category
(approach speed of less than 141 knots and a wing span of 79 feet or less (current
type of aircraft operating at the airport). This is detailed in the April 2, 2009
application on the first page of the cover letter and on page 2 of the Finding of No
Significant Impact (FONSI). Any additional activity increases at the airport which
may occur would occur with or without the construction of the RSA. The current
and estimated growth at the Johnston County Airport predicts a need to develop
facilities for hangar and apron square footage to accommodate the projected
demand important to the economic vitality of the airport and the surrounding
community and to continue its important role as a general aviation reliever for
Raleigh-Durham International Airport. The proposed Corporate Area Development
will meet the need for this projected growth. The forecast and proposed facility
requirements were derived in the Airport's last Airport Layout and Master Plan
dated July 2008.
The RSA project's needs are to provide safety for aviators, passengers, people on the
ground, and to bring the airport into compliance with current FAA standards and
regulations. The purpose of the proposed RSA project is to satisfy the needs by
constructing an extended Runway Safety Area 1000 feet long and 500 feet wide
that satisfies current FAA requirements for a class C-II airport.
The Corporate Area development project's need is to accommodate projected
increases in airport usage and hangar space demand. The purpose of the proposed
Corporate Area development is to satisfy the project need in an efficient manner
compliant with current FAA guidelines and the Airport Master Plan.
0
•
2. Comment: The Nature of Activity section from your project narrative
description details that the fill slopes will be at a 4:1 ratio. This office believes
that these slopes can be steepened to a 3:1 ratio or greater to reduce fill impacts,
but still allow for maintenance and mowing. Please provide revised impact
estimates and drawings based on 3:1 fill slopes.
Response: The RSA fill slopes were designed at 4:1 ratio to comply with FAA
guidelines for runway design (305.c). The maximum fill slope for extended
Runway Safety Areas is recommended 4:1. As requested, a comparison was made
of 4:1 versus 3:1 fill slopes. The results are displayed in the attached figure. As
expected, fill quantities and jurisdictional impacts decrease slightly with a 3:1
slope. However, the failure to comply with FAA guidelines, increased
stabilization costs, and long-term maintenance costs make 3:1 slopes not
preferred.
The RSA grading design was refined and corrected in some areas resulting in
reduced impacts to jurisdictional features. Below is a revised Table 12
(Jurisdictional Impacts Summary) with the impact reduction also shown. This Table
12 replaces Table 12 in the original permit application.
Table 12 (Revised). Jurisdictional Impacts Summary and Reduction From Initial Application
Site Feature Excavation Fill Total Reduction
RSA Perm. Riparian Wetland 0.18 7.55 7.73 -1.11
(acres)
RSA Temp. Riparian Wetland None 0.17 0.17 +0.05
(acres)
Corp. Non-Riparian Wetland None 10.31 10.31 None
Area (acres)
RSA Stream None 685 685 -94
(linear feet)
RSA Buffer Zone 1 653 43,843 44,496 -3,971
square feet
RSA Buffer Zone 2 149 28,325 28,474 -2,185
(square feet)
•

•
STORMWATER DESIGN REPORT
CORPORATE AREA
AT
JOHNSTON COUNTY AIRPORT
JOHNSTON, NORTH CAROLINA
•
Prepared for
Johnston County Airport
@R0WLq0
AUG 7 2009
DENR - Mr41TER Q(MLITY
SANp S?MWA IXTMMCH
80324.00.CA
0
1001 Pinnacle Point Drive, Suite 110, Columbia, SC 29223
August 2009
Johnston County Airport
Stormwater Design Report
• Table of Contents
1. Introduction
1.1. Project Description
1.2. Stormwater Design Requirements
1.3. Water Quality Results
1.4. Water Quantity Results
2. Mapping
2.1. USGS Map
2.2. Soil Survey Map
2.3. FEMA FIRM
2.4. Aerial Photo
3. Water Quality
3.1. Overview
3.2. Water Quality Volume
3.3. Flow Splitter
4. Water Quantity
4.1. Methodology
4.2. NRCS Curve Numbers
4.3. Time of Concentrations
4.4. Drainage Basins
• 5. Erosion Control Measures
5.1. Background
5.2. Project Phasing
Appendices
Appendix A - Nitrogen Loadings Summary
Appendix B - Watershed Maps
Appendix C - Soils Data
Appendix D - FEMA Firmette
Appendix E - Pre/Post Analysis Calculations
Appendix F - Stormdrain Hydraulic Calculations
Appendix G - Erosion Control Calculations
•
P-kWK
WOICKSON
StormwaterDesian Report
Johnston County Airport
Stormwater Design Report
1.0 Introduction
The Johnston County Airport in Smithfield, North Carolina is proposing two onsite projects that
will require best management practices (BMPs) and erosion control measures to bring it into
compliance with Johnston County, NCDENR DWQ and Land Quality stormwater and erosion
control requirements. The projects are referred to in this report and as the t-hangar expansion
project and extended runway safety area project. This report supports the design of those
proposed BMPs shown in the separately attached plans that help the airport meet local and state
regulatory requirements for stormwater.
1.1 Project Description
For the purposes of addressing stormwater requirements the t-hangar expansion project and
extended runway safety area projects are two independent projects. The t-hangar expansion
project is located adjacent to the main terminal area while the extended runway safety area
project is located at the northern side of the existing runway. A further description of the project
follows:
T-Hangar Expansion Project: This is a multi-phased project that will involve the upfront
construction of the bioretention pond and dry pond which will be sized for the ultimate build out
of the site. The following is a more detailed description of the two phases for this project:
• Phase 1 - T-Hangar Expansion Project: The future construction of the concrete pads and
hangars will occur an unknown time period behind the upfront tree clearing and grading
of the site. The proposed closed drainage systems will also lag in time behind the upfront
clearing. For this reason, a series of grass lined open channels are proposed to collect
stormwater runoff and direct it into the bioretention pond and dry pond.
• Phase 2 - T-Hangar Expansion Project: Grading and installation of a new apron for the
proposed set of hangars that will include a closed and open drainage system that collects
stormwater runoff, a bioretention pond and dry pond that treats water quality and
provides detention of water quantity. 16.0 acres of new impervious area which includes
the hangar apron and buildings is proposed as part of this project. The apron will be
built now with hangar construction scheduled for the next one to two years.
Extended Runway Safety Area: The existing grass safety area north of the runway will be
extended approximately 700 linear feet over Reedy Creek. As much as 25 feet of fill will be
placed over the proposed culverts at Reedy Creek. The proposed culverts at Reedy Creek are
twin 10 feet by 6 feet reinforced concrete box culverts (RCBCs) flanking a 9 feet by 7 feet center
RCBC. This reach of Reedy Creek is not a FEMA identified stream and therefore a submittal to
FEMA will not be required. A separate report has been prepared addressing the design of these
culverts.
•
W DIC KSON
Stormwater Design Report
Johnston County Airport
Stormwater Design Report
C
C
N
?ytY
N ?
go,1?rr,Cy Rd 3
A
arth'-
?? 4
C}?
Obrerpaie Q ? 5'
Whaley
Helghls
Ly
BMUWi?
a %
Johnston
Ctwn"
Airport
O
s
OkY«a?°.r.
210
r ?'o
N
911
f
SUr"?
?y
b
!? o
Oa F
yr N
Project
`Location Q? ' y
a.. N O R T H C tiA R O L
70 °<H-'sr A.*' Oa.f RC
West Smithfield 4"e wr ! I{ ri 7?
in
Cas'.lehavov
ye!I St <P 30
? A 4's Ln
s
y Hasorra? Rn
s;
3o yS 301
Smithfield= ?
6 86
'Pra h a
.F ti ?a ?s? E of Sr
0
y y sei`? .,,a
A s
Fairfleld =
y ..r
p ?3< Rc
B
°a
r'aedm R` 8s .
Qua
Bus
70
US ?r,ynw•v l
Ra`dr a9;
:??a pu I miles
Figure 1: Location Map
•
1.2 Stormwater Design Requirements
The following water quality and quantity requirements taken from DWQ and Johnston County
were used in the design the proposed onsite BMPs:
• TSS: Remove 85% TSS to meet DWQ stormwater requirements for the Neuse River
Basin.
• Total Nitrogen, N: Reduce nitrogen loadings down to 8.0 lbs/ac/year to qualify for the
buy-down program or reduce nitrogen loadings down to 3.6 lb/ac/year to meet Johnston
County requirements for water quality.
• Attenuation for 1-Year, 24-hour Storm: Reduce post project peak flows for the 1-year
frequency 24-hour duration storm to at or below the pre-project peak flow. This is a
Johnston County requirement for water quantity.
• Attenuation for the 10- and 25-Year, 24-hour Storms: Check the peak flows for the 10-
and 25-year flood events to confirm that there is less than a 10% increase to pre-project
conditions flows. Provide detention or secure a waiver from the Johnston County
stormwater administrator if peak flows exceed pre-project flows by more than 10%. This
is a Johnston County requirement for water quantity.
r ?CKSON
Stormwater Design Report
Johnston County Airport
Stormwater Design Report
1.3 Water Quality Results:
As shown in ;ApI)cndI\ :A and the separately attached plans, the BMPs needed to meet nitrogen
and TSS removal requirements are a bioretention pond and dry pond in series. These BMPs meet
nutrient and TSS removal requirements yet do not permanently store stormwater runoff and
therefore are sensitive to the airport's concerns with bird strikes. Because the site is in an
environmentally sensitive watershed, the maximum export loading rate is 8.0 lbs/ac/year. The
proposed plan to address nitrogen removal is to reduce the loadings to 8.0 lbs/ac/year to qualify
for entrance into the buy down program. Achieving the maximum export rate of 3.6 lbs/ac/year
will require purchasing credits from a mitigation bank. Because a bioretention pond removes
85% TSS all requirements for TSS will be met with this single BMP facility. The following table
summarizes the removal of nitrogen necessary to bring the T-Hangar project into County
requirements:
Table I: Nitrogen Removal Summary
Proposed TN TN Removed by TN Removed by TN Removed Net Export
Loading Rate w/ No Bioretention Area Dry Pond by both BMPs Loading Rate
BMPs (lbs/ac/yr) (Ibs/ yr) (Ibs /yr) (Ibs /yr) (Ibs/ac/yr)
16.0 164.9 11.1 176.0 7.9
As shown in Table 1 and Appcii(h\ iA, the proposed BMPs exceed the minimum nitrogen removal
amounts to enter the buy-down program. The net export loading rate with the bioretention pond
and dry pond in place is 7.9 Ibs/ac/year which qualifies the project for participation in the buy-
down program.
1.4 Water Quantity Results:
To achieve the pre-vs-post requirements for water quantity a dry pond is proposed just
downstream of the proposed bioretention pond. As shown in Table 2, the peak flows leaving the
site for the proposed conditions 1-, 10- and 25-year flood events is less than the pre-project
conditions.
Table 2: Peak Flow Summary

Storm Frequency Peak Discharge, Q (cfs)
Pre-Developed Post-Developed
1 Year 46.24 43.73
10 Year 105.23 86.39
25 Year 134.54 109.63
A more detailed description of the hydrologic modeling and supporting data is provided in a later
section of this report.

F-k fx
iCKSON
Stormwater Design Report
Johnston County Airport
Stormwater Design Report
2.0 Mapping
2.1 USGS Map:
Discharge flows into Reedy Branch, then in a westerly direction to Swift Creek.. The project
coordinates are 35"32'27"N, 78"23'31 "W.
•

Figure 2: USGS Topographic Quadrangle (Saluda South)
•

Ilk- Stormwater Design Report }11CKSON
Johnston County Airport
Stormwater Design Report
• 2.2 Soil Survey Map
The soils found on the site have a NRCS rating of B to D. The following map shows the
distribution of the soils over the project area.
•
•
Figure 3: NRCS Hydrologic Soil Groups
See Appendix C for soil descriptions.
°CKSOn
Stormwater Design Report
Johnston County Airport
Stormwater Design Report
•
CJ
A FIRM, Panel
IRM a ortion of the FEM As shown in
12 FE MA F of the airport on P endix D.
location ded in APP etter of
shows the A firmette is Pro" conditional I
The exhibit below ber 5, 2005. and therefore a
dated Decem MA identified stream
31201685001 not on a FE ro1ect. -} "
protect is art of this P
Figure 4 the be required as P' ---- ,
will not - --
Map Revision
0
o?x el 45081 C0300E
?- a
Figure 4: FEMA M P Pan
C u?i1y ?Oli Oftiu 1U18 LOnfu
Johnston County Airport
Stormwater Design Report
2.4 AERIAL PHOTO
The exhibit below shows the location of the airport on an aerial photo, courtesy of Google Earth.
The project coordinates are 3532'27"N, 78"23'3 1 "W.
E
•
Stormwater Design Report o,Figure 5: Existing Conditions Land Use
'iCKSON

Johnston County Airport
Stormwater Design Report
• 3.0 Water Quality
3.1 Overview
To meet local and state requirements for water quality a series of BMPs are proposed to address
both TSS and nitrogen export from the site. The following two sections describe the overall
concept of how water quality was addressed for each of the two projects:
T-Hangar Expansion Project
As described earlier in the report, a bioretention pond and a dry pond in series are proposed to
bring the project into compliance with local and state regulatory requirements. At a minimum the
proposed BMPs are required to reduce nitrogen to at or below 8.0 lbs/acre/year. With the
construction of 16.0 acres of impervious area the pre-BMP export rate of nitrogen is 16.01
lbs/acre/year. Therefore BMPs are required. A bioretention pond and dry pond in series will
exceed the minimum amount needed for removal (See Table 1) and allow the airport to
participate in the buy-down program. A bioretention pond was chosen because the newly
adopted removal rates for nitrogen are now 60% for a bioretention pond with an internal water
storage zone. In addition, this facility limits the time water is ponding and therefore limits
potential for bird strikes.
The proposed bioretention pond will have an internal water storage zone and therefore the
calculations submitted with this report show a 60% reduction of nitrogen through this BMP. The
• grassed dry pond will retreat the runoff from the bioretention pond prior to outfalling into the
closed 24" diameter RCP drainage system that leaves the hangar area. A flow splitter is proposed
in the forebay of the bioretention pond which will divert large flood events around the
bioretention pond. An 18-inch diameter RCP allows the smaller rainfall events to pass directly
into the bioretention pond. Once the flood events rise 8" above the invert of the 18-inch diameter
outfall pipe flows will be redirected over a 20 foot long weir that outfalls into a 42-inch diameter
RCP. This 42-inch diameter RCP will outfall directly into the dry pond for water quality
retreatment and attenuation.
Extended Runway Safety Area
Because the extended runway safety area does not involve the installation of impervious areas
there are no TSS or nitrogen removal requirements for this project. No specific water quality
BMPs are proposed as part of this project.
3.2 Water Quality Volume
The runoff volume generated from the first inch of rainfall was estimated using NRCS methods
as described in TR-55. As shown in Appendix E the runoff volume needed for water quality
treatment is 38,979 cubic feet along with a minimum surface area of 14,437 square feet. The
bioretention pond will provide 39,472 cubic feet of storage and 15,145 square feet of surface area
as shown in the Appendix E.
•
P_kWK
WDICKSON
Stormwater Design Report
Johnston County Airport
Stormwater Design Report
3.3 Flow Splitter
A flow splitter will be constructed in the concrete forebay to control flows entering the
bioretention pond. An 18-inch diameter RCP will direct the runoff from the first inch of rainfall
directly into the bioretention pond. A 20 feet long weir set 8 inches above the invert of the 18-
inch diameter RCP will divert flows around the bioretention in large flood events. Runoff in the
large flood events will bypass the bioretention pond and will be attenuated by the dry pond for
water quantity control. An 18-inch diameter RCP was chosen because it will pass just more than
the runoff generated from 1-inch of rainfall with 8 inches of head on it. A peak flow of 8 cfs was
targeted as the flow needed to pass directly into the bioretention pond prior to any diversion into
the dry pond.
4.0 Water Quantity
A dry pond is proposed as part of the T-Hangar project to attenuate peak flows so that the post-
project flows are at or below the pre-project flows for the 1-, 10- and 25-year flood events. As
shown in Table 2 all peak flows are reducing and the project meets Johnston County stormwater
requirements for water quantity. Appendix B includes a map that shows the proposed drainage
areas. For the purposes of making a comparison to the changes in peak flows, a single basin with
the same drainage area was assumed for the pre-project conditions. Because no new impervious
areas are proposed as part of the Extended Runway Safety Area project an analysis of the peak
flows was not prepared for this project.
is 4.1 Methodology
The proposed dry pond was sized using Intelisolve's computer model Hydraflow Hydrographs
2007. This program simulates the stormwater runoff process in estimating the peak flows for pre-
and post-project conditions. In addition this program will account for the attenuation effect the
dry pond with riser/barrel configuration will have on peak flows. Hydraflow offers a variety of
methods for simulating rainfall-runoff response and hydrograph development. An NRSCS Type
Il storm was chosen along with precipitation data for the 1-, 10-, 25-, and 100-year frequency; 24-
hour duration. The NRCS curve number approach was selected to calculate runoff volumes from
the precipitation data. Sub-basin unit hydrographs for these flood volumes were developed using
the NRCS lag times.
Hydraflow Storm Sewers 2008 was used to design the closed drainage systems. The hydrology
for this model is based on the Rational Method along with intensity-duration-frequency curves for
the Johnston County regional area. The system was designed to pass the 10-year flood event
without inundating the rims of the drop inlets.
4.2 NRCS Curve Numbers
Runoff curve numbers (RCNs), which are presented in this report, were generated using the
hydrologic soil group and corresponding existing and proposed landuse. Runoff curve numbers
• were developed by weighting the area and corresponding curve numbers for each type of landuse.
I<
/ I 1<S
Stormwater Design Report
Johnston County Airport
Stormwater Design Report
This methodology is based on the NRCS document entitled Urban Hydrology for Small
Watersheds, dated June 1986 and commonly referred to as TR-55.
4.3 Time of Concentrations
Existing and future time of concentrations were calculated using GIS topographic mapping.
Because the computed times of concentration were less than 5 minutes, a time of 5 minutes was
assumed per standard hydrologic practices. Time of concentrations calculations are shown in
Appendix F. The time of concentration for the proposed conditions Basin #1 was assumed to be
5.0 minutes due to the almost entire coverage of hangar apron. A summary of all input data is
shown in the following table:
Table 3: Peak Hvdrologic Innut Data
Conditions Drainage Area Runoff Curve Number Time of
Concentration (min)
Existing 21.66 74 22
Proposed 21.66 93 5
4.4 Drainage Basins
Two drainage basins were delineated at the T-Hangar Expansion Project area to account for the
flows that enter the dry pond and a separate area that passes through the drainage system
is undetained. These basins were delineated using the proposed contours and drainage system. For
the purposes of comparison it was assumed that the existing a proposed drainage basins would be
the same in area. Although Basin #2 goes around the dry pond undetained, the dry pond over
detains flows so that the next effect results in no increases to peak flows leaving the site.
5.0 Erosion Control Measures
5.1 Back rg ound
This section of the report supports the design of the erosion control measures proposed for this
project. Erosion control measures were design in accordance with the North Carolina Department
of Environment and Natural Resources (NCDENR) erosion and sediment control manual. As
shown on the attached design plans, the project is made up of the following:
The erosion control for the project will be done in two phases to correlate with the grading plan
(see attached plans). Phase 1 erosion control measures will be installed for the initial clearing of
the site. These measures will include a series of temporary sediment basin with Phase 1 ditches,
grass lined channels, silt fencing, rock pipe inlet protection, and a temporary gravel construction
entrance. The future dry pond will be used as a temporary sediment basin with riser/barrel.
After the site has been filled and a storm drainage system installed, the Phase 2 erosion control
measures will be installed. Immediately after the site has been graded, the proposed drop inlets
PKWK
WDICW,: KSON
Stormwater Design Report mm o = ,o „
Johnston County Airport
Stormwater Design Report
and catch basins will be protected with inlet protection. See the separately attached plans for
additional information about the sediment and erosion control and construction sequencing.
5.2. Project Phasing
Corporate Hangar Area - Phase 1
Sediment Basin with Riser
A sediment basin with riser (NCDENR E&SC Std. 6.61.1) has been proposed onsite in the future
grass dry pond. This basin was designed for the criteria listed in the North Carolina Erosion and
Sediment Control Planning and Design Manual, dated June 1, 2006. The sediment basin is
provided to detain sediment-laden runoff and trap the sediment to protect receiving streams,
lakes, drainage systems, and protect adjacent property. Appendix G shows the in-house
spreadsheets and calculations used to size the sediment basin for this project.
Grass Lined Channels
There are 3 grass lined channels NCDENR E&SC Std. 6.30.1 that will be constructed during the
Phase I grading plan. The 3 channels will convey and dispose of concentrated surface runoff
without damage from erosion, deposition, or flooding. An in-house spreadsheet and calculations
(see Appendix G) shows the hydraulic evaluation used in the design of these channels.
Channel #1 at the hanger area is approximately 375 linear feet of open ditch that will be
• temporarily created in the Phase I grading plan near the proposed detention pond. This channel
slopes at about .022 ft/ft with a 10 foot bottom width. The 10-year channel velocity is
approximately 1.47 feet per second which is non-erosive for clay soils. A temporary jute net liner
is called out to help facilitate grass growth despite there not being a need for a liner for erosion
control purposes.
Channel #2 at the hanger area is approximately 660 linear feet of open ditch that will be
temporarily created in the Phase I grading plan near the proposed detention pond. This channel
slopes at about .015 ft/ft with a 10 foot bottom width. The 10-year channel velocity is
approximately 2.04 feet per second which is non-erosive for clay soils. A temporary jute net liner
is called out to help facilitate grass growth despite there not being a need for a liner for erosion
control purposes.
Channel #3 at the hanger area is approximately 750 linear feet of open ditch that will be
temporarily created in the Phase I grading plan near the proposed detention pond. This channel
slopes at about .013 ft/ft with a 16 foot bottom width. The 10-year channel velocity is
approximately 1.74 feet per second which is non-erosive for clay soils. A temporary jute net liner
is called out to help facilitate grass growth despite there not being a need for a liner for erosion
control purposes.
•
P_kWK
StormwaterDesian Report
? '?? N
u Ify inifafltU^_iur¢ COnsulf
Johnston County Airport
Stormwater Design Report
• Silt Fence
Silt fence (NCDENR E&SC Std. 6.62. 1) shall be placed in several areas onsite as shown in the
Corporate Area Erosion and Sediment Control Plan. In all locations of proposed silt fence, the
drainage area is less than 1/4-acre per 100 linear feet of fencing.
Temporary Gravel Construction Entrance/Exit
A temporary construction entrance (NCDENR E&SC Std. 6.06. 1) will be provided off of Charlie
Day Memorial Drive as shown in the Corporate Area Erosion and Sediment Control Plan. The
construction entrance will provide a buffer area where vehicles can drop their mud and sediment
to avoid transporting it onto public roads, to control erosion from surface runoff and to help
control dust.
Corporate Hangar Area - Phase 2
Block and gravel inlet protection (NCDENR E&SC Std. 6.52. 1) will be provided at all inlets as
shown on the Corporate Area Erosion and Sediment Control Plan. The inlet protection will help
prevent sediment from entering storm drains before stabilizing the contributing watershed. This
practice allows early use of the storm drain system.
Extended Runway Safety Area
As shown in the separately attached plans, erosion control at the Extended Runway Safety Area
• will be performed through a use of the following measures:
• Temporary diversion ditches
• Silt fence
• Sediment traps
• Inlet protect
• Permanent channel liners
Sediment traps in the runway safety area were limited to less than 5.0 acres of drainage area per
the erosion and sediment control manual. Appendix G includes the erosion control calculations
used to support the design of this project.

P&WK
Stormwater Design Report rC?l 3<SC R!
u.tY inltaslru Clure cOnsullOnif
Nitrogen Loadings Summary
• Project: Johnston County Airport
Prepared by: DJK
Dated: 7-20-09
Project Location: Airport T-Han ar Expansion Site
TN Export Coeff.
Type of Land Cover Area ac Ibs/ac/ ear TN Export Ibs/ ear
Permanently Protected
Undisturbed Open Space
forest, unmown meadow 0.5 0.6 0.3
Permanently Protected
Managed Open Space
lawn, grass, landscaping) 5.1 1.2 6.2
Impervious Surfaces
(roads, parking
lots,driveways, roofs,
storage areas, gravel
roads 16.0 21.2 340.2
Totals 21.7 346.6
• Weighted Loading Rate for Site = 16.01 Ib/ac/yr
Required removal amount to achieve 8 Ibs/ac/yr = 173.38 Ibs/yr
Required removal amount to achieve 3.6 Ibs/ac/yr = 268.67 Ibs/yr
TN Export Removed by Bioretenion Area = 164.87 Ibs/yr
TN Export Removed by Dry Pond = 11.14 Ibs/yr
TN Export Removed by both BMPs = 176.01 Ibs/yr
TN Export from site = 170.63 Ibs/yr
Weighted Loading Rate for Site after BMP = 7.88 Ib/ac/yr
Cost of buydown per acre = 25.00 $/Ib
Buydown payout period = 30 years
Buydown amount = $69,494.56
0
EXISTING CONDITIONS WATERSHED MAP
M/ /? / / / / / I ,? /1?
140 - I

+
/

\
4
+ + +++4
# # \
\ i
I
+ + +

+

" `\ ??? PASIN 11
I
I i \

\
1 1 / / / I I I
?
_
40--'
?-
1

------------
/
--
-
?' ?'? I i \ \ (
,- 1
--- ------- 1
/
II

I 1
\ ?
1
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
\
II ? 1
II _
`---- _-_'-----_-----_-_-_-_--_- %?'_SIN`?_
- - - - - - - - - - - - - - - - - - - -_- ?\ - \
-----------------
!- --- .-" ----
------
------.

/
/

i/
I

MANAQM
? DRAWIND SCALE
=
JK I
r
BY PROJECT ECT DATE WK
w OX
OVED BY PROJECT NUMBER DICKSON
En
ineers • Planners • Sww
m
FILE NAME PLOT DATE g
y
Landscape Architects

5540 CENTERVIEW DRIVE RELEASED FOR DATE
SUITE 315
RALEIGH, NC 27606 APPROVALS
[phone]
BIDDING
Columbia, SC
Asheville, NC Hickory, NC CONSTRUCTION
Atlanta, GA Raleigh, NC
Charlotte, NC Wilmington, NC RECORD DWG.
rOJECT MANAGER
IF DJK
DRAWN BY
DJK
APPROVED BY
DRAWING SCALE
i•zoo Ph
PROJECT DATE
PRWECT NUMBER
PLOT DATE
WK
DICKSON
Engineers • Planners • Surveyors
Landscape Architects
5540 CENTERVIEW DRIVE
SUITE 315
RALEIGH, NC 27606
[phone]
Columbia, SC
Asheville, NC Hickory, NC
Atlanta, GA Raleigh, NC
Charlotte, NC Wilmington, NC
RELEASED FOR
APPROVALS
BIDDING
CONSTRUCTION
RECORD DWG.
DATE
Soil Map-Johnston County, North Carolina
(Johnston County Airport)
io
0' 33'31"
16
35° 31' 30"
is
m
r r?
.
0
Map Scale: 1:17,900 if printed on As ize (8.5" x 11") sheet.
a
N N Meters
A 0 150 300 600 900
N Feet
0 500 1,000 2,000 3,000
USDA Natural Resources Web Soil Survey
Conservation Service National Cooperative Soil Survey
35° 33' 29"
35'31'27"
(V
N
8/7/2009
Page 1 of 4

co
_c
0
`m
U
L v
r
Z .a
?Q
c c
O
U
7
C C
O O
u) N
C C
0 L
0 0
CL v
co
O
U)
Z
O
NQ
LL
O
LL
Z
cCL
G
Z
LLl
W
J
a
Op
U)

C
0
v E m m r
v a? >
V
_0
3 C
Q)

L

m

U 0)

m

a) 0
7
O C
m m (? U)
7 H- _ CO
p
p c° E
N
O_
0-
m C

O U r

U C

O N - U
.6 E
L O
X
a)
a)
Z C)
U
U
? m
L
In L O O 00
D Q'
Z L O
p 7
U E

a) 3 a
co C
Q
0 z
L (V
p
z -p N
N
O
E
U -
)
U
?
L
3 N m
N Q L N N
O cn
5 y
7 a
m C N
O(D Q
"
Q
C
O
> U
m
N
a) O
7 3 C
U
L C
7
° M
IM
O _
O
>
M L a)
O ,
m
w c
° °mZz- o
aN
m .
.
g
E o U?
c c o
a f ?m o
a) E

C
O- a)
t0 _
Of
L 2 a)
-0 O
N .N
2 N L a) >
m o w m
a o w m _0 r m m a Y E

p U m m J m
U) > N L
C .?
N
0 5 m Z E E 01 _
° w
m

T

c
0
a T
m
io
? i
m
E °
o
o a) j
_0
=
a)
O
m U)
2
-0
Q ?
m
-° n ?°

m >'E
a? 0)
-t6 3c
-0 o v0

Q nmN-'
o a c
0

(
N` 7
U)
a

m m 7n

m m n a

7 L 0 a a
i
> U N

- Z °

m
Co
2
E
<n?U
?.
cn°cn
o m E
E
°.!= o

-Ln u)
m T
0
a 0
U 3

t
C/)
N 10
y
c

O O

O Q)

N c
C
O
=
a1
tq
N
'O
O

m
a m

y
LL T U)
N m

O t O

N

N

N

O
0-' R'

O

_
m
> L
O c C? U O U O o D J
J O ?
i9 LL
N
C
E3 CL 0 d)
U)
a
o

3
O c

o d

m °
CL
to

a`' CL

c
a o
o
O o o ° Q
°
O _
Q O m m?
O
U a
(n d >
N m _
-
4- o

E L

O m °

C

O U) _,

N

O U)

o a

U) 0

Q a

U)

N
y N

.O .
3
C U
' N
O
T y
LO U
> >
N (6

C
c9 N
>
N
C_
U

41
Q)
Y

U ID
C
-O
C
N
>
L
Y
N
U

'Q
T
C
d Q (n Q m m U U U J J U) (n (n (n (n
(n
fn
(n
a, a
S 6
„ _
m
SD N
.6 G
U)
Q fA
Cr) Kt
O w
p o
N CV
a)
00 0)
m
a
m
Z
7
? o
? U
7 N
m
'o ?
C/) a
U
m
C
O
m
z
a)
v
N
d ?
L
? C
y O
m y
7 a1
., C
m O
Z U
DI
I
Jr
0
Soil Map-Johnston County, North Carolina
0
•
r?
Map Unit Legend
Johnston County Airport
Johnston County, North Carolina (NC101)
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
AaA Altavista fine sandy loam, 0 to 2 percent slopes, 70.2 4.9%
occasionally flooded
AmB Appling-Marlboro complex 1 to 6 percent slopes 12.6 0.9%
AsA Augusta sandy loam, 0 to 2 percent slopes, 54.5 3.8%
occasionally flooded
Bb Bibb sandy loam, 0 to 2 percent slopes, 10.5 0.7%
frequently flooded
Ch Chewacla loam, 0 to 2 percent slopes, frequently 51.4 3.6%
flooded
CoB Cowarts loamy sand, 2 to 6 percent slopes 16.9 1.2%
DoA Dorian fine sandy loam, 0 to 2 percent slopes, 57.4 4.0%
rarely flooded
FaB Faceville sandy loam, 2 to 6 percent slopes 6.4 0.4%
GeB Gilead sandy loam, 2 to 8 percent slopes 38.4 2.7%
GeD Gilead sandy loam, 8 to 15 percent slopes 5.3 0.4%
GoA Goldsboro sandy loam, 0 to 2 percent slopes 26.6 1.9%
Le Leaf silt loam, 0 to 2 percent slopes 45.2 3.2%
Ly Lynchburg sandy loam, 0 to 2 percent slopes 25.5 1.8%0
McB Marlboro-Cecil complex, 2 to 8 percent slopes 8.9 0.6%
NnB Nason silt loam, 2 to 8 percent slopes 28.5 2.0%
NnD Nason silt loam, 8 to 15 percent slopes 80.3 5.6%
NnE Nason silt loam, 15 to 25 percent slopes 76.8 5.4%
NoA Norfolk loamy sand, 0 to 2 percent slopes 25.9 1.8%
NoB Norfolk loamy sand, 2 to 6 percent slopes 207.0 14.5%
PaE Pacolet loam, 15 to 25 percent slopes 9.9 0.7%

Ra
4 Rains sandy loam, 0 to 2 percent slopes 18.6 1.3%
StA State sandy loam, 0 to 3 percent slopes, 57.0 4.0%
occasionally flooded
Ta Tarboro loamy sand, 0 to 2 percent slopes, rarely 14.3 1.0%
flooded

Tn Toisnot loam, 0 to 2 percent slopes 7.8 0.5%
To Tomotley sandy loam, 0 to 2 percent slopes, 103.7 7.2%
rarely flooded
UcB Uchee loamy coarse sand, 2 to 6 percent slopes 2.4 0.2%
UCC Uchee loamy coarse sand, 6 to 12 percent slopes 3.2 0.2%
Ud Udorthents, loamy 155.6 10.9%
W Water 5.1- -- - - 0.4%
WaB Wagram loamy sand, 0 to 6 percent slopes 3.4 0.2%
U3"H Natural Kesources Web Soil Survey 8/7/2009
?? Conservation Service National Cooperative Soil Survey Page 3 of 4
Soil Map-Johnston County, North Carolina
Johnston County Airport
• Johnston County, North Carolina (NC101)
Map Unit Symbol Map Unit Name Acres in AOI
Wh Warne loam, 0 to 2 percent slopes, occasionally 22.3
flooded
wt Wehadkee loam, 0 to 2 percent slopes, 115.5
frequently flooded
WW Wehadkee-Chastain association, 0 to 2 percent 64.6
slopes, frequently flooded
Totals for Area of Interest 1,431.6
C
•
Percent of AOI
1.6%
8.1%
4.5%
100.0%
Natural Kesources Web Soil Survey 8/7/2009
aiiiiiiiiiiiiiii Conservation Service National Cooperative Soil Survey Page 4 of 4
I•

0
?g
? o a w.
a C ? C U
E?DOE
w CL.
w aC LL o o
JL C vii mttl L O Q O ULLL
O G ?j . u Z' OD 40 ?O N «
Q O"? oE, OCO C .6m$c
Q'- W x z s s ° 20 ;v v om
CL.
02
61 l0 7 z nc? Qcn y E ° a v
oe=` C m
z O O QT X O N C
v _ LL7 O
a ? m a
W ?' Q _ O z u N O
Z Q'' W N M , C Y
CE OE LL
Lr,
o a Z r c?? r. },1 v v O v y C?
Z Q m ai ?m ?? ?i nua r 53v
Lf) C=
_ O J oa L z? ?ME g.OL 2
C= 0 Z CT V N H S O.y
0 W
J r
LL ? E NL
H d ?Q ° U C E ? of W O Y O
1? U C O
IF LL 0
M. V M. d 99 a e F Q o f
m c U E
V a?E $0
- -
co m 0 ol
.
z
a, R • ? ? s i Y .fir i, .?,. i' ? ? ?+a ? t 1., ,
"s ?r A • i ? v r i a.,
r
§; ,> y
am
a
K ? t
rot, ,
cn w N =
,.
® m w. _
T s`
e? q w Q i
U- cc
aw cc
FD • J
^ ! _
CC 2m,
?- kt m ? ?• d ? 'fir ?. C ® ?
LO
rS
y '
?? =sue ?• ? ?°.
r. 5w
X
' .?'.
N
W W
C
N_
Cf)
C
T
O
C
C
Q
C
O
0-
C
O
C
N
N
O
m
N
d
E a
m ?
? N
5 ?s
w U
N
0 U
O
2 m a
-ct
¢
Q
x
U
O
W
x
y
¢
? fW..
N Z
W
C
O
_ a
w
rt+
W
d o
O_ w
m a
•
N
? CL .o
? c m
`1 al
u, m U
a?
U
¢ 'm
Ip I. _ (q
N N
UI
3 U U
O N y
? C
>
0
x
¢
w
Q
V
U
C
Cl)
LL
LL
U-
0
z
m
¢
Z
2
CL
O
w
Q
O
0
z
Q
J
Q
Z
Q
LLJ
3
U
C U

ro
OI C
m

O2'
T °

Cl) a

N

C
A
Cf)
C
U)
o
m O
rn
N
M co
co
T
m
U
+ T
lu
U
+
/n
N
c
N
°
C
ll
N
. LL
C
W

V

C
d
H N
OT
? o o
o
u) O O

L 0
U o
U
? m m
r N In

co o
M
o O
c
m

E
w '- u
u Z.
J o N N
O
ca
(n >
O IT
II U l

L w
-Fo

°
¢
w w oo
? o H W
m m
w
?_
Y r a o 0
>>
>

I L
a>c
o L
a?
y
H W c
C C
ww
'-
o-
a)N
Y O O
to N d d
O O
(
f
ZY OY LL LL n
n
N
N
U
L
r
E
v
0
0
L
N
N
m
C
N
M
U
_N
u
U
d
O
Z
n.
m
Y
¢
a
I? O
(n N N N M rn t` M
Cl) O r CO N

O
(n ^
co
^ co (° N
O cl)
w
V O
N O
N
N Ln o)
r r N (o r
U

N v
o O C C
N N O O
m m N N
m (9
Il IL
L
C C C C
? ? r ? ? E
O O 0 0 C
m
E O
m
N
'
Q) N O a) al O
j

Ir o O
N° O Q C
m L E N
E E
s
o E E o
m a o
d F F ?> H H H
CM - (o (n
V
? o
E N co
V
O
O
Z
m 7
7 7
n rn o
C
?
r
Q
O
O
U
O N
m
N N L L O c
U c a a i)
¢
N
3 o 3
Q
?O m 0 O V
ro 0 O O j
? a a a U)
E
m
a
N Cl) V (n (o h
O
O
Z
M (f] (O N (O N
r rn O N h o
C l0 (O (O f? r`
?
O
O
I
G
QI
7
N
ti
c
0
U
N
U

v
v m
3 N
w e
73
<D O 2
° L O

O 'O
? ? J= U U ?
U E o
N U C
O o U
.C
? C
?
o r o co
m
o m ID
ii
O N
O -o co
m (o
W r (o r
0 0 0 E Lo
E o (n
Q
° ...'?
: E
O n
W , N O O O '? T m
m o
3
Y " )
o 3
0 3
o o
c U m

U
" m
'?A

N ?
Q W
a y
a 4

N
°'
?
N
E

G

Z
U `v q!
C m
w > 'v
E o r ?. d

F-
qty
L
H
N
K o
L w
(n o
¢ a
O N
II

_j
m

`

o

.Q j

C

W

W
E
J

O

L

I _

?
c) c

t0
U
C

U

. l

.;?o n.

rtc_ 'C d>
j m

O C7 Y
v

r Y
v

:E a)
7

o ¢ E
.?
_
O

L m
•(D

o e
c c

5 y

a o

5 -o

a
C,
0
•
•
a
a°
O
f+
L
MO
W
_L
L
O
7@
L
O
+.a
2
s
?L
3
V.
?Q
v
55
0
O
2-
Q
T
C
7
O
U
C 0
? O
(n N
C
0 N
ci)
U M
O O O
L L (?
CL d 0
UJ O (o V V LA I- O O 0) M C co
J
< 2 O 0)100 00 M co M O
M LA (o r 00 O O
0 O
c N?
c 6 LA
I0 r-
O
r
?
' '6
J
O O O
-
iO O
O O C O OIO 6 10
0
H I
>
I

I M' N I V Lr)
Lr)
OD
cl)
Lo
N
'.V ICI, LA O 0) (D con co N
LL M' (D 0) O M M, (D O O O O r
0,OOr 0 00 0 0
W
>_

Q C) LA (o 100 r O
''. Lo I'?t co O co r? (D O)
V 10)': M
? 0) AI N
co 0 1
o
J
J U '.. 00 N Q)I Co CAIN
?MII?IN LA (D O'N
r N It 'IT to (o r- (D (D?r
M
r (D
Cl)
?.
j M,
to
O ...
Q M 0)V N V (D j'(D r- m M LA
O M,N(D r- (1) LA r
N V V
=L (D O'.. M co co 0 V N LA (D
C¢7 O O'I
O ? N MIV It r NN N CO')
*- N?IM M ?t 7LA
:00 3- 0) M (D
N N 00 LA OD
I? Lo co Lo
N co
! r l-
M
LL i
O') co co 6 N OiN E O O ,O
' O
(? 0 0 0 0 0 0 O a) a) 0 0 6 6 O
Q I I I
= 7
U U U
U
U
U
7 M I CO
LL LAIl0) V
MM00
M V M O M r T (D O r
to -
O (A W
It (D

U
z2
rjr
rv? O
0
W J (V r M M

>
Z I
co !l- V M N' O
OM00M na)
I , ro N
(a n
LA V M
Lo n Lo
LA co
O
'?
(D V
N O co 0)
O O O N
N
0 0) n M
E M 00 Lo T
r (D
M
N
=L 00
0
0
'O
?
r O
? C
0 .0 C
0 N
O >
> 0)
L (0
-
i c ? 3 - - o
O N 0_0 (D O LA O V
O O (D
I O V
O Lo N
I- 0) N It o
N N O 0 . V N N I OD O O
MC
M M 7 V L() (0 (U -0 r N I
N 4)
Z) co (z
0 LLJ co 0)'=
O Q N N M co M? Lo N
M M M M M M M M 0)
O O
0 N
0 N A
0 M V
0 0 LA
0 Lo >
0
U U O O c) 0 0 0 O! O
O O 0 0 0 0 0 0
Q i m N ?

E
-, m
:3 m -
000OLAOLo 'o
O O O O'N O N O E o E
>?
m

cr ,,f'Lo co rN o00
M M MM M M T M'. 0 O
> > E
p 0
> O
0
0 6
LA
O
O O N O
Q L` p ?• Lo (D n 00 00 0)
M
r M cM co M M
Z °
0 0

ui
N
DD
r
c
0
0)
N
ca
N
U U
V M
M M
O
O ? 0)
0 O 0
2
E E E
O O
Q > >
T
0 N N
? n is
U)
is
•
•
•
MG
W
a
a°
i
CL
O
1.`
cc
I-
0
f?
VI
2
i
G
S:
s
1
W V
i
s?
i
^u 5
r ?n
V-
O
a
L
Q
C
O
U rn
O O
O
U) O
7 N
U cz
Q N
O " M
a. a_ 0
c?
O
C
cz

J ui o ,,I- r co O N O
O ,N oOiO (fl r- O ,
Q O 'O TiCO LO f, O i
O J° O O O O O O r
~ 0

O O T1r O) 00

lL O (fl M r O) 00
O O r N N M
W
? I
ui
Q
J CD

N ?', r- - M I
i

Cn
U O)
M O T CO O 00
00, (
O
0
0) ,
O N
(
0
-] T T

< O O O M O O
-
J M r-
CO f- CO
¢ O
N
SILO
U N , L
O
I
N It (O O N
T i
O O N O) 00 O)
0
O
0
o (
0. (
j 00
0 ? ?
U 0 000C70
Q
J (O N 00 M I(0 d'
Q N N N ?t - t ,

LJJ O)
M r (O N 00
LO
Z CY) Cl)
N o CY)
LLJ U

W 0
>
U
Z (D O (A T LO
(O O f- 00 M o
CO It M r" o
O)
N
O)
Lo LO "I' M co
N N,N N
T Lo (nO M I 't O
V 0) 00 N N CO ,
't co M O) LO r
M
' CO MoO

Q N
i N M,M co co
0 LL1 i

? i
Z
O Q O
O It
LO 0 N co ? O'
CO n ? 00 O)
U U O O O O O O o
Q
0i 0 0 o Of 0
0
?
Ln? o o;0 0 0 0
N
M M
M ? LO CO I? aD
M
'

_

T

T
M
,
M M M
T l r T
O I

Z
O
U
O
M
C=
O
co
>
N
cz
N N
U U
N
N CD

N ?
m >
c O
L a
E E
=3 2
O O
Y
O -
a ? ?
f CT CT
`V L L
L cz w
Z
•
C7
•
W
E
I-
0
cn
^L
W
1
T
C
O
U
L
0
2
rn
.r3
s?
Yv
pia
Q
6
V-
O
Q
Q
c
O
U
c =
U rn
? o
o
U O
c?
O Q N
O N cv
CL 0- r)
0000 0
0 (7 (7 C7 0 a
O Z z z z z z o f
-C z C U fOA L
r LC) p? It CO O CO It N C\j OO r_
E CO C) T T O O H O r M
r
-0 _j 70 '
N W O .? O N CO) ._ C O O
2.2 O O
-g co Q a a
O -6 -
> > O O O O E O O m O) «s
a> c o . _5 p p o U E E
E O O?c Z U U? .V O 0 C
??i8 QOM. C
o 0))? QO o
O O -o -a
T 7
E
ca o O O
7EE
Q -2-2
O >
6 O O
O O (D
0) H
T
a)
Q
W O It M O N O
J O N a0 O r- 0
Q o o r M LO l? r- o
O -J - 0 0 0 0 0 0 -
0
>
0 0 0 r T CD 00
O O a) OD c7 M O
LL O O CO CY) r CA O
U 0 0 0 r N N M

W
>
Q W O o n LO O 't Co
N
O ?t
O r- r
OD C7
O r?
00
(n :D J U
` C7 O
co O
(4 N
C) 00
N LO
(o
O T T
U >
U

Q o cO O O rn o ln
(n n It N (0 LO
J C'Y) I- T C7 r` OO
¢
C
7 N N LO rn to T
N 't CO M N
T
O O O N O OD O
O O O O 't O co
LL O O (O O r- CO O0
U o 0 0 0 0 0 0
Q
J
Q
z w O (O N OD co (O 't
l1J 2i C\l
0)

N

N It
0 -

N "t
00
w J U Cl) o o N LO f"
'
O N C7 C7 C7 C
7
CC >
U
z
O (D 'It O (A T LO
(O O f- 00 ('7 CY)
CO ?t C')
't
0
C3
0)
N
LO Cn
N
It
(D
00
T N N N N
LO CO o Cf) ? o
It CF) CO N N OD
It CO CO CY) L(]
Cn (Y) CO T
' co
Y (D
Y CA
N N O
) (
) C
) co
O w

Z
Q
O O
O I-
LC) O
co N
? OD
N It
00 o
CA
U U 0 0 0 0 0 0 0
Q
0 0 0 0 0 0 0
Ln O O O O O o
N M 4 6 CO r- 00
M M M M M M
T M

O

z?
O
U
(D
C7
c
0
>
_N
O
T
U U
O It
00 r
M It
? N
.>
ZS O
a)Q
2 2
2 2
O O
73
CL zz- -F
ZT ZT
ro
E a) a)
z 3 3:
•
Time of Concentration Calculation
SCS Segmental Method
Project: Johnston County Airport
Conditions: Existing
Prepared by: DJK Date: 7-21-09 r p ?{ S; O N
Engineers . Planners . Surveyors
L.andsrcaye Architects
Basin #1
C?
Sheet Flow Segment ID AB
1. Surface description (Table 3-1) Woods
2. Manning's roughness coeff., n (Table 3-1) 0.40
3. Flow length, L (Total < 300 ft) ft 100
4. Two-year 24-hour rainfall, P in 3.6
5. Land slope, S T, = 0.007(nL)° ' ft/ft
0.040
6. Travel time, T t p2 0.5S0.4 hr 0.26
Shallow Concentrated Flow Segment ID BC
7. Surface description (Paved or Unpaved) Un aved
8. Flow length, L ft 460
9. Watercourse slope, S ft/ft 0.016
10. Average velocity, (Figure 3-1) v, = 20s2a2<s>O5 ft/sec 2.1
11.Travel time, T t v = 16.1345(s)O5 hd 0.06
Channel Flow Segment ID CD
12. Cross sectional flow area, A ft 12
13. Wetted perimeter, P ft 8.6
14. Hydraulic radius, R = ft 1.4
15. Channel slope, S ft/ft 0.009
16. Manning's roughness coeff., n 0.045
17. Channel velocity, V 2„ ,/, ft/sec 3.8
18. Flow length, L V = 1.49R s ft 703
19.Travel time, T t n hr 0.05
Time of Concentration = 0.37 hr
Time of Concentration = 22.1 min
0
•
Time of Concentration Calculation
SCS Segmental Method
Project: Johnston County Airport
Conditions: Proposed
Prepared by:DJK Date: 7-21-09 r I= I G l<Vs.O 1V
Engineers . Planners . Surveyors
Landscape Architects
Basin #2
•
Sheet Flow Segment ID AB
1. Surface description (Table 3-1) Grass
2. Manning's roughness coeff., n (Table 3-1) 0.24
3. Flow length, L (Total < 300 ft) ft 100
4. Two-year 24-hour rainfall, P in 3.6
5. Land slope, S T, = 0.007(nL)09 ft/ft 0.005
6. Travel time, T t p20._550.4 hr 0.39
Shallow Concentrated Flow Segment ID BC
7. Surface description (Paved or Unpaved) Unpaved
8. Flow length, L ft 278
9. Watercourse slope, S v, = 20.3ft/ft 0.005
10. Average velocity, (Figure 3-1) ft/sec 1.1
11.Travel time, T t v, = 16.1345(s)hr 0.07
Channel Flow Segment ID CD
12. Cross sectional flow area, A ft 40
13. Wetted perimeter, P ft 20
14. Hydraulic radius, R = ft 2.0
15. Channel slope, S ft/ft 0.009
16. Manning's roughness coeff., n 0.045
17. Channel velocity, V 2,32 ft/sec 4.9
18. Flow length, L V = 1.49 R s ft 703
19.Travel time, T t n hr 0.04
Time of Concentration = 0.50 hr
Time of Concentration = 29.9 min
0
• Inlet Structure Flotation
Project: StayRight Pre-Cast
•
......................................................
......................................................
......................................................
......................................................
......................................................
......................................................
......................................................
......................................................
......................................................
......................................................
......................................................
...................................................... ..................
...................
..................
...................
..................
...................
..................
...................
..................
...................
..................
...................
Invert Out Elev. 130.50
Prima Weir Elev. 134.60
Overflow Weir Elev. 136.00
Secondary Weir H ht (ft) 1.25
Secondary Weir Width (ft) 3.00 caic
Prima Weir H ht (ft) 2.65 caic
Prima Weir Width (ft) 3.00 caic
To of Box Elev. 138.00 caic
..................................................
......................................................
...................................................... ..................
..................
..................

Inside L th (ft) (perpendicular to flow 3.00
Inside Width (ft) 3.00
Outside L th ft (perpendicular to flow 4.00 caic
Outside Width ft 4.00 caic
Prima weir h th ft CALCULATED 4.10 calc
Overflow weir h th ft CALCULATED 5.50 caic
Wall thickness ft 0.50
To thickness ft 0.75
Grout thickness ft 0.25
Base thickness (ft) 1.50 Des
...................................................... ..
..................................... .. ....
Orifice diameter in 8.00
Orifice area s -ft 0.35 caic
Outlet pipe dia in 24.00
Outlet pipe areas ft 3.14 caic

............................................................ ..................
Concrete weight (lbs/cu ft) 146.00
Water weight Ibs/cu ft 62.40

........................................................................................ F
obbW.
.....................................
Str volume (cu-yd) 2.82

....................................................... ..................................
Str weight (Ibs) 11,126

....................................................................................... .....................................
Buoyant force (Ibs) 7,488

........................................................... .........:...:......................
Resultant weight (Ibs) 3,638

................................................................................ .....................................
Factor of Safety 1.49

........................................................... ..:.....:...........................
Bearing Weight (Ibs/sq ft) 695.37

gn Input
• Conservative:
Bouyant force measured at top of structure lid
•
•
C7

y >

U '
y -
g
CL Z Z Z Z Z _

a) bA _ - -
_-

S
Z?
?

r

N

W
O
O
O y =? g ?

O r
Q r

I
i
L
,a 0
n o O O O O

c o
C\j
N
?
M
N
L
L .?.?.-
ca o O _
d i

U =
ca
=
II
"
-?^ o

a

W
ro
Oq
0
O a)

c -

S
2
a N
O L Q L
o a.

O ?

m ?
U
°
CS N
U
0

- co
U
O N v O
Q)

N N
32 >
T .0 C
CO c Cd
L
Q 3 4 M O
LL
C
cu
J Y
U

C O
_U
° 0
ca
-
U a o [t
N N
4
CO
°

EU

a U c 3 c >

O ?
a> O a,
? C Q O 0 tn p C CL N
L
? y N L
-
°
Z ^ L
V
j
y ?
II
a)
?O 41. C\j co It LO .?

cu L: . a) N 3
O ° c

Q
?r` °
4. ?'c of
?
a)
--
n O 7 c - U a)
O
a
) 0
-C
C
-C
Z ,? II II II II p co
CL H > o rn Z co

ro ca m ca co
LL J C7 C7 C7 C'3 C7
m a> a? a? m
?,
J .O. N N N a)
? 7 7 7 7 7

w
L
O
O
I? V It N M
o
m
U ? CV
a N ? ? r
U

? CO CO V O O

O
IT O)
0 M Cf)
I N
Q c
0 n t M

c
O
O
O
O

U F O O
O O O
c_ co CO M M M
c O O O
O O
g O O O O O
U N
? ?
O)
O)
O
O)
O)
a m
? N

3
? a M co M M M
M M M
It co
[L
c
ca O O O
ro
U Q (MO O M n
C
O OD (
O
c
? Q
O
O
O
O
O
? ? co co co co co

o? O O O O O
??
a N N N N N
°? n
D 0 O O O O

O
CO L
O
O
O
O
O
c -
s O O CO O
U
N
7
CO
V
N
? N N
0
?
? c
C
C
U

c c c
c c c
Cd t0 o CO a7

U
U
U
U
U cu

•
U
N
.N!
?+
m
C
C--)
M_
0
0
?Q
r?
v
I I
N
Q
N
L
~ 'C
c O
G! C.
N C
1- O
U
Q. c
E O
yY
CD r-
O o
L
O. d v C
v? r
d C O
wawa
L p
C ? M
L
C'0
y O
0 N
3
o
L Q ? 0
a; m
0°3
`o>F
E
a m ?
O
V LL
C h
m ar
C
CD W
N Q ? ?
y ?
C
m
9 m C
Q ? 0
ar
O
J
W
O
O
C L O
m O a?
E 3
L
7 ? V
m?. C6
N
N W
m a W Go
CL
m I
o ? E
oa
0 go
04
co
W
-`
o
C3 a N
m .OW..
CR
7 W
H?
oa
`W M
a cc
q Q N
C3
o
a ~