20071470_Reports_20070607

sr1w
N d w^ "o
STATE OF NORTH CAROLINA
DEPARTN ENT OF TRANSPORTATION
MICHAEL F. EASLEY
GOVERNOR
June 4, 2007
MEMORANDUM TO:
FROM:
SUBJECT:
John Hennessy
Division of Water Quality
Colin Mellor 6/? ? H -
PDEA - Natural Environment Unit
R-2635 ICI Report
Overland Pollutant Loading Analyses
LYNDO TIPPETT
SECRETARY
Attached is a copy of the Indirect and Cumulative Impact Report on Overland Pollutant
Analyses for R-2635, the Western Wake Expressway. Please contact me by phone (715-
1426) or email (cmellor ibdot.state.nc.us) if you have any questions or comments. An
electronic copy will also be forwarded through NCDOT's file transfer system.
Cc: Greg Price,
Bob Deaton,
Missy Dickens,
Rob Ridings
Tracy Roberts

MAILING ADDRESS:
NC DEPARTMENT OF TRANSPORTATION
PROJECT DEVELOPMENT AND ENVIRONMENTAL ANALYSIS
NATURAL ENVIRONMENT UNIT
1598 MAIL SERVICE CENTER
RALEIGH NC 27699-1598
Natural environment Unit
Human Environment Unit
Project Development
Division of Water Quality (w/ electronic attachment)
NCTPA
TELEPHONE: [phone] or 919-715-1334 LOCATION:
FAX: [phone] TRANSPORTATION BUILDING
1 SOUTH WILMINGTON STREET
WEBSITE: WWW.NCDOT.ORG RALEIGH NC
INDIRECT AND CUMULATIVE IMPACT REPORT
OVERLAND POLLUTANT LOADING ANALYSES
WESTERN WAKE EXPRESSWAY
WAKE AND HARNETT COUNTIES,
NORTH CAROLINA
(R-2635)
PREPARED FOR:
P??oF NoarH c,?o j,
* ?C
a 2
19_ QO/
-•r OFTStAN'THE NORTH CAROLINA DEPARTMENT OF TRANSPORTATION
RALEIGH, NORTH CAROLINA
MAY 2007
EXECUTIVE SUMMARY
Watershed analyses were performed on behalf of the N.C. Department of Transportation
(NCDOT) for an area in the vicinity of the southern terminus of the proposed Western Wake
' Expressway (Expressway) (R-2635) for Current Condition and two future scenarios that
consider "without-Expressway" versus "with-Expressway" development levels. The analyses
conducted as part of this study include comparative modeling of current and future loadings for
' total nitrogen (TN), total phosphorus (TP), and overland sediment. The Study Area for these
analyses is defined by the upper reaches of impaired watersheds anticipated to receive a large
amount of development induced by the new commuting access provided by the Expressway to
regional job centers. The purpose of the study is to estimate the percentage difference in
nutrient and sediment loads between the without-Expressway and with-Expressway scenarios.
This study is required by the N.C. Division of Water Quality (NCDWQ) in an effort to address
i indirect and cumulative impacts for consideration during Section 401 Water Quality Certification
review. These analyses were completed using the PLOAD watershed model available in US
' Environmental Protection Agency (USEPA) Better Assessment Science Integrating point and
Nonpoint Sources (BASINS) modeling system. The PLOAD model is intended to be a generic,
screening resolution model that predicts the overland pollutant loading from multiple land use
' types. The simple design and implementation of the PLOAD model allows for broad resolution
screening to be performed quickly and cost effectively.
Two future scenarios were evaluated including: 1) year 2030 projected growth without the
Expressway and 2) year 2030 projected growth with the Expressway and proposed induced
development specifically attributable to the Expressway. Existing (current) condition was
evaluated to provide a baseline with similar model assumptions and parameters to facilitate a
comparative analysis without verification from field data. Both future scenarios include
reductions resulting from current and possible BMPs including Phase I and Phase II stormwater
1 controls (ponds) and riparian buffers specifically implemented to reflect the protection
ordinances mandated by local municipalities.
Study Area boundaries were defined through group consensus of the modeling team, the land
use consultant, NCDOT, and NCDWQ. Current Condition land use data were generated by
EcoScience Corporation using Geographical Information Systems to categorize 2005 aerial
photography as well as parcel, tax, zoning, and land use data obtained from both Wake and
Harnett County governments. Future land use coverages were predicted and spatially
distributed over the Current Condition data by HNTB Corporation. Land use data were provided
' in digital format and integrated into the water quality models using Environmental Services
ESRI's ArcMap software for analyses.
By year 2030, modeling of land use derived from predicted growth indicates that the
Expressway and associated induced development will result in a change of less than 1-percent
over ambient growth, absent the Expressway, for all modeled pollutants. These analyses have
' been performed to support a comparative evaluation of pollutant loads, and actual pollutant
loads are expected to be different than reported in this study. Additionally, the consideration of
Best Management Practices (BMPs) had a substantial effect on predicted loads. In future
' modeling projects, a focus on the type of land use developed as well as the effects of managed
and unmanaged stormwater on overall pollutant loads is recommended.

1

Executive Summary
TABLE OF CONTENTS
1.0 Introduction ....................................................................................................................1
1.1 Water Resources ..........................................................................................................1
1.1.1 Trends in Water Quality .........................................................................................4
1.1.2 Existing Water Quality Protection Measures ....................................................... ..5
1.2 Federally Protected Species ...................................................................................... ..7
1.3 Project Goals .............................................................................................................. ..8
2.0 Methods ..........................................................................................................................9
2.1 Study Area Definition .................................................................................................. ..9
2.2 Land Use Generation ................................................................................................. ..9
2.2.1 Current Condition ................................................................................................. 10
2.2.2 Year 2030 Predicted Condition: Scenarios 1 and 2 ............................................. 10
2.2.3 Identification of Best Management Practices (BMPs) .......................................... 11
Existing BMPs ........................................................................................................... 11
Stream and Sub-watershed Delineation .................................................................... 12
Buffer Generation ...................................................................................................... 12
Aerial Photography Interpretation .............................................................................. 12
Buffer Assessment Results ....................................................................................... 13
Implementation in the Best Management Practices in Future Scenarios .................. 13
3.0 Model Description ........................................................................................................ 14
3.1 PLOAD History ........................................................................................................... 14
3.2 Simple Method versus Export Coeficients .................................................................. 14
3.3 Input parameters ........................................................................................................ 15
3.4 BMP implementation .................................................................................................. 18
3.5 Future Load Calculation ............................................................................................. 20
4.0 Results and Discussion .............................................................................................. 22
4.1 Current Condition ....................................................................................................... 22
4.2 Scenario 1 (without Expressway) ............................................................................... 22
4.3 Scenario 2 (with Expressway) .................................................................................... 24
4.4 Effects of Best Management Practices on Pollutant Loading Estimates .................... 24
5.0 Summary ....................................................................................................................... 25
6.0 References .................................................................................................................... 27

1
11,
FIGURES
Figure 1. Study Area Location ............................................................................ Appendix A
Figure 2. Study Area Watersheds, 303(d) Streams, and Monitoring Sites......... Appendix A
Figure 3. Land Use for Three Modeled Scenarios .............................................. Appendix A
Figure 4. Existing Buffer Identification Examples ............................................... Appendix A
Figure 5. Future Pollutant Loading Example ...................................................... Appendix A
Figure 6. Total Sediment Load for 3 Modeled Scenarios ................................... Appendix A
Figure 7. Total Nitrogen Load for 3 Modeled Scenarios ..................................... Appendix A
Figure 8. Total Phosphorus Load for 3 Modeled Scenarios ............................... Appendix A
Figure 9. Change in Sediment Load Resulting from Development
for 3 Modeled Scenarios ..................................................................... Appendix A
Figure 10. Change in Nitrogen Load Resulting from Development
for 3 Modeled Scenarios ..................................................................... Appendix A
Figure 11. Change in Phosphorus Load Resulting from Development
for 3 Modeled Scenarios ..................................................................... Appendix A
TABLES
Table 1. Study Area stream classification units ..................................................................3
Table 2. Applicable BMP regulations within the Study Area ............................................ ..6
Table 3. Aquatic federally listed species in Wake and Harnett Counties, NC .................. ..7
Table 4. Corresponding land use categories used in PLOAD .......................................... 10
Table 5. Land use composition of Current Condition, Scenario 1, and Scenario 2.......... 11
Table 6. Study Area sub-watersheds classified by percentage of watershed
served by five buffer width categories ................................................................ 13
Table 7. Acreage of anticipated development per planning jurisdiction for future ............ 14
Table 8. EMC values for the PLOAD Model ..................................................................... 16
Table 9. BMP Percentage removal efficiencies for PLOAD model .................................. 18
Table 10. Example of BMP Effects using the polygon implementation method in
PLOAD ............................................................................................................... 19
Table 11. Exported annual loads of pollutants from the Study Area ................................... 23

17

INDIRECT AND CUMULATIVE IMPACT REPORT
OVERLAND POLLUTANT LOADING ANALYSES
WESTERN WAKE EXPRESSWAY(R-2635)
WAKE AND HARNETT COUNTIES, NORTH CAROLINA
1.0 INTRODUCTION
EcoScience Corporation (ESC) has been retained by the N.C. Department of Transportation
(NCDOT) to analyze anticipated changes in overland nutrient and sediment loads within two
watersheds in the proximity of the proposed Western Wake Expressway (the Expressway) in
Wake County, North Carolina (Figure 1, Appendix A). The purpose of this study is twofold: 1)
address water quality implications of the Expressway and associated future development on
already impaired waterbodies, as well as make inferences as to the possible impacts that may
result from additional water quality stressors on sensitive aquatic species afforded federal and
state protection; and 2) provide regulatory agencies with supporting documentation to determine
whether existing ordinances and Best Management Practices (BMPs), already mandated by
local municipalities, are sufficient to protect regional water quality and maintain the integrity of
existing federally protected aquatic species populations. The 67.3-square mile region of study
(hereafter referred to as the "Study Area") is composed of the headwaters of Middle and
Kenneth/Neills Creeks in southern Wake and northern Harnett Counties, NC. These
watersheds are not directly impacted by the Expressway but instead were deemed at risk for
induced development by the N.C. Division of Water Quality (NCDWQ), and were therefore
agreed upon to be the focus of study for this report.
The proposed alignment of the Expressway extends from a point on NC 55 approximately 1.5
miles north of the historic township of Carpenter southward in an arc that rounds west of the
Town of Apex and ties back into NC 55 approximately 0.4 mile north of the historic township of
Feltonville. The 12.5-mile corridor is proposed as a toll-funded, multi-lane, divided, controlled-
access facility on new location. Additional interchanges are planned at US Highway 64 and US
Highway 1. The Expressway will relieve traffic congestion, reduce commuting time, and
improve access to employment centers - Raleigh, Durham, and the Research Triangle Park
(RTP) - for rural areas located in southwestern Wake County and northern Harnett County.
This effort has been requested by the NCDWQ as part of the review process for issuance of
Section 401 Water Quality Certification. In addition, the U.S. Fish and Wildlife Service
(USFWS) is expected to have interest in these analyses in order to comment on the potential for
the Expressway to affect federally protect species.
1.1 Water Resources
The headwaters of the Middle Creek and Kenneth/Neills Creek watersheds occur within the
Study Area. The Study Area, which is bisected by an east-west oriented divide that separates
drainage between the Neuse and Cape Fear River basins, is located within sub-basins 03-04-03
of the Neuse River basin and sub-basin 03-06-07 of the Cape Fear River basin (NCDWQ 2002,
2005a). The portion of the Middle Creek watershed included in the Study Area (Neuse River
basin) is part of the USGS Hydrologic Unit 030202011201, while the Kenneth/Neills Creek
watershed portion (Cape Fear Basin) lies within the USGS Hydrologic Unit 030300040301. The
study area contains seven named streams and three lakes: Basal Creek, Middle Creek, Rocky
Branch, Camp Branch, Mills Branch, Kenneth Creek, Neills Creek, Sunset Lake, Bass Lake,
and Bells Lake (Figures 1-2, Appendix A).
06-296.01 1 Western Wake Expressway /Cl
In the Neuse River basin, Middle Creek originates near the Town of Apex and flows southeast
for approximately 13.3 miles until reaching the eastern boundary of the Study Area northeast of
Fuquay-Varina. Basal Creek enters the Study Area near the northwestern edge of Fuquay-
Varina and flows north for approximately 1.6 miles until it joins Middle Creek. Rocky Branch,
Camp Branch, and Mills Branch flow south from the northern boundary of the Study Area to
Middle Creek for distances of 3.1 miles, 4.4 miles, and 3.8 miles, respectively. In the Cape Fear
River basin, both Kenneth Creek and Neills Creek originate near the center of the Study Area
and flow generally south/southeast. The Study Area contains approximately 8.2 miles of
Kenneth Creek and approximately 5.3 miles of Neills Creek.
Classifications are assigned to waters of the State of North Carolina based on the existing or
contemplated best usage. Best Usage Classifications of B NSW and C NSW are listed for
Study Area streams in the Neuse River basin. Streams classified as nutrient sensitive waters
(NSW) are subject to growths of microscopic or macroscopic vegetation that can impact aquatic
communities (NCDWQ 2007). Class B waters are protected for primary recreation (involving
human contact such as swimming and water skiing) and other uses suitable for Class C.
Class C waters are protected for secondary recreation, fishing wildlife, fish and aquatic life
propagation and survival and other uses. All of the streams in the Neuse River basin portion of
the Study Area are fully supporting their designated uses according to NCDWQ's 2002 Neuse
River Basinwide Water Quality Plan (NCDWQ 2002) (See Table 1).
The Cape Fear River basin portion of the Study Area includes two class C streams and two WS-
IV (Water Supply IV) streams. Water Supply IV streams are freshwater streams used as water
supply and are provided restrictions on development and waste water discharges (NCDWQ
2007). Kenneth Creek has a classification of NS (not supporting designated use) for all reaches
classified as C and WS-IV within the Study Area (NCDWQ 2005a) (Table 1). One reach of
Neills Creek is designated as fully supporting the WS-IV classification, while the other reach has
a partially supporting classification.
NCDWQ has initiated a whole-basin approach to water quality management for the 17 river
basins within the state. Water quality for the Study Area is summarized in the Neuse River
Basinwide Water Quality Plan (NCDWQ 2002) and the Cape Fear River Basinwide Water
Quality Plan (NCDWQ 2005a). Water quality within the Neuse and Cape Fear River basins is
assessed by sampling of fish and benthic macroi nve rteb rates and data collected at ambient
(chemical and physical water quality) monitoring stations. The portion of Neuse River sub-basin
03-04-03 that occurs within the Study Area contains six benthic macroinvertebrate sampling
stations and one fish sampling station. The portion of the Cape Fear sub-basin that occurs
within the Study Area contains four macroinvertebrate sampling stations and one fish sampling
station (Figure 2, Appendix A). No ambient water quality monitoring stations currently occur
within the Study Area. All streams within the Study Area are considered to be warm water
streams (USACE et al. 2003).
06-296.01 2 Western Wake Expressway ICI
Table 1. Studv Area stream classification units.
Stream Stream Stream Classification River NCDWQ Use
Classification
Classification Index
Index
Basin Stream Support
Index Classification* Rating**
From source to a point
18-16-(0.3) Neills Creek (Neals 0.3 mile upstream of Cape C PS
Creek) Wake-Harnett County Fear
line
From a point 0.3 mile
18-16-(0.7) Neills Creek (Neals upstream of Wake- Cape WS-IV FS
Creek) Harnett County line to Fear
Cape Fear River
From source to a point Cape
18-16-1-(1) Kenneth Creek 0.6 mile downstream of C NS
US Hwy 40 Fear
From Wake-Harnett Cape
18-16-1-(2) Kenneth Creek County line to Neills WS-IV NS
Creek Fear
From source to
27-43-15-(1) Middle Creek backwaters of Sunset Neuse C NSW FS
Lake
Middle Creek From backwaters of
27-43-15-(2) (Sunset Lake) Sunset Lake to dam at Neuse B NSW FS
Sunset Lake
27-43-15-(4) Middle Creek From dam at Sunset Neuse C NSW FS
Lake to Swift Creek
27-43-15-3 Basal Creek (Bass From source to Sunset Neuse B NSW FS
Lake) Lake, Middle Creek
27-43-15-4.5 Rocky Branch From source to Middle Neuse C NSW FS
Creek
27-43-15-5 Camp Branch From source to Middle Neuse C NSW FS
Creek
Entire lake and
27-43-15-6 Bells Lake connecting stream to Neuse C NSW FS
Middle Creek
27-43-15-7 Mills Branch From source to Middle Neuse C NSW FS
Creek
-u=Mass m; L,=Mass L,; vv,s-iv=vvater,supply iv; N,sw=Nutrient,sensitive waters
**PS=Partially Supporting; FS=Fully Supporting; NS=Not Supporting
Source: NCDWQ 2002, NCDWQ 2005a
06-296.01 3 Western Wake Expressway ICI

NCDWQ has assembled a list of impaired water bodies according to the Clean Water Act
Section 303(d) and 40 CFR 130.7, which is typically compiled every two years. The most
recent, effective final list is dated 2004, while a draft list for 2006 is currently under public
review. These lists will be hereafter referred to by year release, such as the 2004 final list or
2006 draft list (NCDWQ 2004, NCDWQ 2006). These lists are a comprehensive accounting of
all impaired water bodies. An impaired water body is one that does not meet water quality
standards including designated uses, numeric and narrative criteria, and anti-degradation
requirements defined in 40 CFR 131. The standard violations may be due to an individual
pollutant, multiple pollutants, or an unknown cause of impairment. The impairment could come
from point sources, non-point sources, and/or atmospheric deposition. North Carolina's
designations are strongly based upon the aquatic-life, use-support guidelines available in the
Section 305(b) guidelines (USEPA-841-B-97-002A and -002B). Those streams only attaining
Partially Supporting or Not Supporting status are listed on the 2006 draft list (NCDWQ 2006).
Streams are further categorized into one of six parts within the 2006 draft list according to the
source of impairment and degree of rehabilitation required for the stream to adequately support
aquatic life. Within Parts 1, 4, 5, and 6 of the list, North Carolina has developed a priority
ranking scheme (low, medium, and high) that reflects the relative value and benefits those water
bodies provide to the State. In the Neuse River basin portion of the Study Area, the uppermost
0.5-mile reach of Middle Creek, from its source to the back waters of Sunset Lake, is on the
2006 draft list. In the Cape Fear River basin portion of the Study Area, an approximately 4.0-
mile stretch of Kenneth Creek, flowing from its source to the Harnett County line, is listed in both
the earlier 2002 final list and the current 2004 final list (NCDWQ 2002, NCDWQ 2004). The
next 3.6-mile reach of Kenneth Creek downstream of the Harnett County line extending south to
the boundary of the Study Area is listed in the 2006 draft list. Neills Creek, from its source to
the southern border of the Study Area, a distance of approximately 5.7 miles, is listed on the
2006 draft list.
1.1.1 Trends in Water Quality
The most obvious water quality trend detected is the continued deteroriation of Kenneth Creek
in the Cape Fear River basin portion of the Study Area. In 2004, approximately 4.2 miles of
Kenneth Creek was classified as a 303(d) stream and in 2006 approximately 8.2 miles of
Kenneth Creek are classified as a 303(d) stream. Additionally, Neills Creek was absent from
303(d) classification in 2004 but was listed as a 303(d) stream for approximately 5.3 miles in
2006 (NCDWQ 2006). The changes in 303(d) listed-stream length is depicted on Figure 2 (See
Appendix A).
In terms of bioclassification (benthic macroinvertebrates and fish sampling), Neills Creek
received a Fair rating in 1996 and Good-Fair in 2000, a five-year improvement (NCDWQ 1996,
NCDWQ 2000). Kenneth Creek, however, received a Poor rating for both 1996 and 2000, likely
a result of the sampling station's location below the Fuquay-Varina waste water treatment plant
and local urban nonpoint source pollution (NCDWQ 1996, NCDWQ 2000). Another possible
cause of impairment is nutrient enrichment from agricultural fields. In the 2005 Cape Fear River
Basinwide Management Plan (NCDWQ 2005a), Kenneth Creek is supporting of aquatic life,
indicated by a Good benthic community rating. However, below the Fuquay-Varina wastewater
treatment plant, Kenneth Creek has had several violations of biological oxygen demand permit
limits, which could negatively affect aquatic life. The benthic community rating for the reach of
Kenneth Creek from the Harnett County line to the confluence with Neills Creek is Poor and
06-296.01 4 Western Wake Expressway IC/
thus impaired for aquatic life. However, this reach of Kenneth Creek does meet its recreation
use support rating because fecal coliform levels were not exceeded.

1
r

1

The Neuse River fish monitoring station along Middle Creek at SR 1404 (Figure 2, Appendix
A) received a fish health rating of Fair-Good in 1991 and a rating of Excellent in 1995
(NCDWQ 1998). This shows an improving trend which correlates with improvements made at
the Cary waste water treatment plant; however, the trend could not be extrapolated to current
conditions, since 1995 was the most recent sample available. The 1998 Neuse River Basinwide
Management Plan (NCDWQ 1998) describes some reaches of Middle Creek as having stream
habitat problems (breaks in the riparian buffer and unstable banks). In terms of benthic
macroinvertebrates, the Middle Creek sampling station at SR 1375 rated Fair in 1986 and 1995
and for all successive samples, including the most recent sample in 2000, the site has improved
and stayed steady at a rating of Good-Fair (NCDWQ 2002). For the use support category of
Aquatic Life and Secondary Recreation, upper Middle Creek received a Supporting rating in
1998 and an Impaired rating in 2002 for a 1.4 mile section of the creek. One likely cause for
impairment is increased stormwater runoff from impervious surfaces in rapidly growing urban
areas, which contributes to increased channel scouring and destruction of habitat for fish and
macroinvertebrates.
1.1.2 Existing Water Quality Protection Measures
An important focus of the modeling analyses performed for this report is to determine whether
existing state and locally mandated regulations and ordinances are sufficient to protect regional
water quality as development pressure persists through the modeling forecast period. As part of
the preparation for the modeling effort, ESC personnel inventoried the variety of protective
measures for riparian buffer widths and stormwater requirements between the different planning
jurisdictions within the Study Area. Government organizations considered include the NCDWQ
(Neuse River Riparian Area Rule and Water Supply Watershed Regulations), the USEPA
(Phases I and II Stormwater Rules), Wake County, Harnett County, the Town of Cary, the Town
of Holly Springs, Town of Fuquay-Varina, and the Town of Apex. The BMPs considered in
these analyses are provided in Table 2.
06-296.01 5 Western Wake Expressway ICI
' R
L
7
CO)
4)
t
t
c
3
N
c
_R
3
d
IL
2
m
m
.c
R
V
CL
N
_d
73
R
F-
Z °

y , ++
C: c
L
O U N N
+N-i C f?0 O_ (D C
c O L O O_ R
_
0 O O
E c > c) c c

L

cm

't R

=1
-0 O`

U

E
? "J a =3
U)
O O U CL
N a
i cu co ° (N (D
N O O
N?
4) 0)
r
" N N N
E 0
- "
- v -°
E

° o
cu
o
c
o
CO -
O O L
'O CL L N
O
(n L (u
O L
O
L
a? -0 > -a E N
-o -v -o
m N 4 cu O +'

3
' -
' °

o Q
=3 Cl)

c
E cr L C U N L Q N
C U `? p N? N E
N N ,? N 2 N? Qj N c N
N L c`u p w U (LO N `u 7
o to to d CA to c U R
U a
F, a -O a N M U a. O w a 0
R UI 0 .C ? R L
L m° m ca m- w m 0 (,) m
it
C L Q
? L L
L L c°
= •O L
U N L c
R (u
3
ca
- ca `° m °
0
0
3 N
3 R
3
a? 3 ?° •

Z 3
`
a?

o
.. E a
E E E

0
N
0
o E
o m w C Q
° R
0 a)
o

a °
cn c
v) .?
U) rn o
U) . E 0)
U) z
i 0
E c co
o
m

co c R
ai
!E
U)

E ° 7
°
n
c o U)
E
16 cn o E c
o
a) 0 C)
CL E `O
L
°

c v
c E
rn
_0

°
co
m
(D `° AA,, E
a)
CL C: tr-
m ca En
E
co
a)
-O C

O +'
N O C
N
N C E m O_
c
4) r
C
C E C

C

N
m
E a)
C
3 ? O N
cn c
0- 0 :3
C C C ? •?
C O c O O C L O
L O L O L L US O L
3 ? ? O
m N N ? O N ?
1 -0 7 -0 -0
R .-.
0 O
O 0
N O
O O L
O C
O O
O?

Q' 0
w 0
-
° -

°

° O CL

° Q
O
' O O ° O c
O O O :3
U
) LO N O LO cn
c
0

13
N
c to
c

0 o
o c > U
U a
U)

c N
>+
X cc
7
C
R tC
U -
2 R
Q 0 L
I
CL U-
0
N
O
1.2 Federally Protected Species
While not directly measurable, it is assumed that increased pollutant loadings resulting from
Expressway-induced development may potentially have an adverse affect on local sensitive and
rare aquatic species. Aside from an interest in regional water quality, the NCDWQ has
requested this study to document the success of existing regulations aimed at preventing
overland pollutants from adversely impacting federally protected species. The NCDWQ and
NCDOT have a successful history of coordinating with local municipalities to strengthen existing
regulations to further protect federally protected aquatic species based upon the results of
modeling analyses similar to those described in this report.
' Species with the federal classification of Endangered, Threatened, or officially Proposed for
such listing are protected under the Endangered Species Act (ESA) of 1973, as amended (16
U.S.C. 1531 et seq.). The term "Endangered Species" is defined as "any species which is in
danger of extinction throughout all or a significant portion of its range," and the term
"Threatened Species" is defined as "any species which is likely to become an Endangered
species within the foreseeable future throughout all or a significant portion of its range" (16
U.S.C. 1532).
Eleven federally listed aquatic species are listed for Wake and Harnett Counties. Table 3
' presents only the listed aquatic federally protected species and specifies their status as
Endangered (E) or Federal Species of Concern (FSC).
Table 3. Aquatic federally listed species in Wake and Harnett Counties, NC.
Federal Record
Common Name Scientific name Status* Status County of Listing
' American eel Anguilla rostrata FSC Current Wake/Harnett
Atlantic pigtoe Fusconaia masoni FSC Current Wake/Harnett
Cape Fear shiner Notropis mekistocholas E Current Harnett
Carolina darter Etheostoma collis lepidinion FSC Probable/ Wake
potential
Carolina madtom Noturus furiosus FSC Current Wake
Carolina redhorse Moxostoma sp. 2 FSC Current Harnett
Green floater Lasmigona subviddis FSC Current Wake
Pinewoods shiner Lythrurus matutinus FSC Current Wake
Sandhills chub Semotilus lumbee FSC Current Harnett
'
Yellow lampmussel Lampsilis cariosa FSC Current Harnett
Yellow lance Elliptio lanceolata FSC Current Wake
"Federal Status: E=Listed Endangered, FSC=Federal Species of Concern
'
Source: USFWS 2007a, USFWS 2007b
Within the Study Area, a known record of the federally endangered Cape Fear shiner (Notropis
' mekistocholas) occurs within the lower reaches of the Kenneth Creek. There are also several
records of state threatened or special concern aquatic species within the Study Area or adjacent
(within 1 mile) region.
06-296.01 7 Western Wake Expressway /CI
1.3 Project Goals
' Results of these overland loading analyses will be used to quantify percentage increases of
sediment and nutrients between two future scenarios: 1) projected growth without the
Expressway and 2) projected growth with the Expressway and development induced by the
project. Analysis of Current Condition (year 2005) was conducted to provide a baseline for
comparison that uses similar assumptions as the future scenarios. Both future scenarios were
modeled with consideration for constraints resulting from current and anticipated BMPs, such as
Neuse River riparian buffers and stormwater ponds resulting from Phase I and II stormwater
controls.
' In order to estimate the overland loading rate-changes for each scenario, long-term, time-series
measurements of stream flow, total suspended sediment (TSS), and nutrient concentrations for
various stream stages in the growing and non-growing seasons are required. A detailed field
study is prohibitive for the current effort due to the large size of the Study Area (67.3 square
miles); therefore, predictive modeling efforts have been employed to determine future nutrient-
and sediment-load trends.
' The pollutant loading computer model chosen for this project was PLOAD, which is a
component model of the Better Assessment Science Integrating point and Nonpoint Sources
(BASINS) modeling system (USEPA 2004). The PLOAD model is intended to be a generic,
screening resolution model that predicts the overland pollutant loading from multiple land use
types. The simple design and implementation of the PLOAD model allows for broad resolution
screening to be performed quickly and cost effectively on multiple NCDOT projects.
Cooperation and coordination with a variety of groups and individuals was necessary for
' completion of this study. All study protocols were reviewed by NCDWQ prior to initiation of the
models.

1
1

06-296.01 8 Western Wake Expressway ICI
2.0 METHODS
This study was heavily dependent on accurate portrayal of available data from a number of
sources. Methods and data sources are described in three primary categories: Study Area
Definition, Land Use Generation, and Identification of Best Management Practices.
2.1 Study Area Definition
The Study Area boundary (Figure 1, Appendix A) was selected by consensus of personnel
from NCDOT, NCDWQ, and ESC. The definition of the Study Area boundaries was ultimately
determined by the 12-digit hydrologic boundaries of impaired (303(d) listed streams) believed to
have the greatest amount of land available for conversion to developed land uses after
Expressway construction. Factors such as overall development density and known populations
of federally protected aquatic species were also considered. The boundaries of the Middle
Creek and Kenneth/Neills Creek watersheds were digitized into a Geographical Information
' Systems (GIS) database by using 12-digit hydrologic unit boundaries created by the N.C.
Center for Geographic Information and Analysis (CGIA). The Study Area also defined the limits
for land use generation for the three modeled scenarios. The Study Area has been used for all
water-quality modeling associated with this study.
The Study Area incorporates portions of two 12-digit hydrologic units (030202011201,
030300040301) likely to be impacted from development induced by the Expressway. Portions
of the Towns of Apex, Cary, Holly Springs, Fuquay-Varina, Angier, and unincorporated areas of
Wake and Harnett Counties comprise the Study Area. Additionally, portions of major roads
' such as US-1, US-401, NC-210, NC-42, and NC-55 occur within the Study Area providing the
major infrastructure for commutes within the boundary.
2.2 Land Use Generation
Thirteen land use categories are utilized in the land use development for provision to PLOAD.
The 13 categories are defined by the amount of impervious area and vegetation cover within a
tax parcel unit (Table 4). Current Condition land use information was digitized by ESC, while
both future land use scenarios were forecast and spatially distributed by HNTB Corporation.
Both future scenarios used the Current Condition land use file as a base, and future
development (both attributable to and independent of the Expressway) was placed on parcels
that were left undeveloped (Woods, Cropland, WoodG) by ESC during the digitization of the
Current Condition. During the model preparation phase for implementing PLOAD, variables that
included cover type, percent impervious surface, and runoff curve numbers were assigned to
each land use category and applied to the parcels within that category. The land use is
depicted for all scenarios in Figure 3 (Appendix A).
06-296.01 9 Western Wake Expressway ICI
' Table 4. Corresponding land use categories used in PLOAD. Study Area land use was
categorized using tax parcels as land use units.
' PLOAD Land Use Category Description
Commercial Business, Commercial, 85-percent Impervious
Cropland Fallow, Row Crops, Small Grain
' House20 Housing, 1-acre lots, 20-percent Impervious
House25 Housing, 0.5-acre lots, 25-percent Impervious
House30 Housing, 0.3-acre lots, 30-percent Impervious
House38 Housing, 0.25-acre lots, 38-percent Impervious
House65 Housing, 0.125-acre lots, 65-percent Impervious
Industrial Business, Industrial, 72-percent Impervious
' Pasture Pasture, Grassland, or Range
Road Roads
Water Lakes, Ponds, Reservoirs
WoodG Woods-Grass Combination
Woods Woodland or Forest
2.2.1 Current Condition
' The Current Condition serves as the baseline against which both future land use scenarios were
developed. In addition to land use mapping provided by Wake and Harnett County GIS
departments, year 2005 Harnett and Wake Counties natural color digital aerial photography
' were used as sources of reference for selecting appropriate model parameters for specific land
uses. N.C. Floodplain Mapping Program (FMP) Light Distance and Ranging (LIDAR) data that
have been compiled by the NCDOT into a county-wide digital elevation model (DEM) were used
' to generate stream features for determination of existing riparian buffer coverage.
To generate the Current Condition land use, the Wake and Harnett County parcel data were
used as the base data layer. The Current Condition land use data were generated by
separating developed from undeveloped parcels, then assigning the most appropriate land use
category by separating residential from non-residential for developed parcels, and assigning a
undeveloped land use category by either aerial photography interpretation or from NC GAP
Analysis plant community data (NCGAP). Data files for zoning, tax information (area of heated
square feet), and information from the parcel database (structure classification codes) were
used in making the land use category assignment for developed parcels.
2.2.2 Year 2030 Predicted Condition: Scenarios 1 and 2
' New development within the Study Area was projected to year 2030 without (Scenario 1) and
with (Scenario 2) the Expressway. Scenarios 1 and 2 are based upon estimated secondary and
cumulative growth. These estimates were generated based on the following assumptions:
1. The Study Area will likely experience considerable
y y development regardless of the
project.
2. Growth generated by the project will mainly be limited to new interchange sub-
watershed areas within the Study Area. However, the region south and east of the
' Study Area may also experience development pressure due to increased
accessibility to regional employment centers.
06-296.01 10 Western Wake Expressway ICI
' New development in both future scenarios is dominated by residential categories in previously
rural areas of forest and cropland. Increases in the commercial and industrial categories are
' centered along major transportation corridors in both scenarios.
Scenario 1 predicts that 10.3 square miles (6,592 acres) will be converted to developed land
' use categories - House20-65, Commercial, Industrial, and Road. Scenario 2 predicts that an
additional 3.4 square miles, 13.7 square miles (8,768 acres) in all, will be converted to
developed land use categories. Table 5 presents the complete land use composition for
' Current Condition (column A), Scenario 1 (column B), and Scenario 2 (column C). The acreage
differences in land use composition between Scenario 1 and Current Condition and Scenario 2
and Current Condition are reported in columns B-A and C-A, respectively.
' Table 5. Land use composition of Current Condition, Scenario 1, and Scenario 2.
Current Scenario 1 A Scenario 2 A
' (acres) (acres) (acres) (acres) (acres)
Land Use A B B-A C C-A
Commercial 660 1537 876 1606 945
Cropland 14160 10570 -3590 10323 -3837
HOUSE20 1204 1182 -21 1108 -96
HOUSE25 8277 8483 206 9751 1474
' HOUSE30 767 3300 2533 1955 1188
HOUSE38 1568 2356 788 2476 908
HOUSE65 475 1919 1444 2056 1581
' Industrial 2269 2876 607 2949 680
Pasture 678 337 -341 443 -235
Road 3076 3076 0 3076 0
Water 446 446 0 446 0
WoodG 719 546 -174 512 -207
Woods 9478 7140 -2337 7055 -2422
2.2.3 Identification of Best Management Practices BMPs
' In order to implement BMPs in the modeling effort, these measures needed to be described and
a method of incorporating the measures into the model needed to be determined. First, a
thorough investigation into applicable ordinances and regulations for all planning jurisdictions
' within the Study Area was undertaken (see Section 1.1.2). Second, identification of the existing
network of riparian buffers was undertaken so that future development predicted to occur by
2030 could utilize BMPs required by local ordinances, while allowing detection of changes in
' existing BMP strategies.
Existing BMPs
A remote sensing exercise, namely aerial photography interpretation, was performed to identify
BMPs in the Current Condition scenario. The scope of this effort was limited to identifying
existing riparian buffers, which can readily be characterized using aerial photography. While it
' is conceded that a variety of existing BMPs, such as stormwater detention basins, likely occur
within the Study Area, the difficulty of locating and assessing the function of such BMPs by
simple aerial photography interpretation alone is prohibitive.
06-296.01 11 Western Wake Expressway ICI

Riparian buffer presence within the watershed of each (presumed) jurisdictional stream in the
Study Area was characterized by width of natural vegetation and percent of the watershed
' overland drainage treated by the buffer, referred to here as the percent served. Buffer widths of
0, 50, 100, 150, and 200 feet were considered. Categories of 0, 25, 75, and 100 percent were
used to describe the percentage of the sub-watershed served by the buffer. The procedure
' used to identify the existing buffers is described below.
Stream and Sub-watershed Delineation
Jurisdictional streams and associated sub-watersheds within the Study Area were delineated to
provide a stream network for the riparian buffer assessment. Stream jurisdiction was assumed
here to include intermittent and perennial streams. In the North Carolina Piedmont, the critical
source areas for intermittent and perennial flow were estimated at 6 and 24 hectares,
respectively (Smith unpublished, personal communication with Periann Russell, NCDWQ 1-23-
2007). Using the 6- and 24-hectare critical source areas, a digital stream network was
' developed for the Study Area with the ArcHydro (CRWR 2003) extension for ArcMap. The
resulting stream network delineates streams from the presumed point of intermittent flow
extending downstream to perennial reaches. Sub-watersheds corresponding to each stream
reach were also delineated.
Buffer Generation
' Five buffer widths were considered in this analysis: 0, 50, 100, 150, and 200 feet. Buffer
polygons corresponding to the five width intervals were described around each stream reach in
' the generated stream network.
Aerial Photography Interpretation
' The condition of riparian buffers in the Current Condition was determined by visual inspection of
year 2005 aerial photography for Wake and Harnett Counties. The stream network, watershed,
and buffer polygon GIS layers were overlaid on the aerial photography. Buffer widths and
percent served values were estimated for each sub-watershed according to the following
guidelines.
' 1. Buffers consist of natural vegetation contiguous to the generated stream channel.
Natural vegetation may be mature or regenerating forest as well as herbaceous marsh
vegetation. For example, consider sub-watershed 1 in Figure 4. Sub-watershed 1
' consists of an assemblage of forest and residential land covers. Only the undisturbed
portions of forest immediately adjacent the generated stream are considered to act as
buffers. Here, 50 percent of the sub-watershed is served by a 50-foot buffer.
' 2. Buffer disturbances include buildings, roads, and managed vegetation
(maintained lawns, utility corridors, and pasture). The buffers of sub-watershed 2 in
Figure 4 are disrupted by a road that extends east-west through the sub-watershed. In
' cases such as this, where all five buffer intervals are disturbed, a percentage served of
less than 100-percent is assigned. In this case, 75 percent of the sub-watershed is
served by a 100-foot buffer.
' 3. Assign the largest undisturbed buffer width. Consider watershed 3 in Figure 4.
Approximately 75 percent of the overland drainage within the sub-watershed passes
through the 200- and 150-foot buffers, while 100 percent of the drainage passes through
06-296.01 12 Western Wake Expressway ICI

' 100- and 50-foot buffers. In this example, the 100-foot buffer is the largest undisturbed
buffer; therefore, 100-percent of the sub-watershed is served by a 100-foot buffer.
' 4. If the stream is enveloped to the extent possible by a buffer, assign the sub-
watershed the width of the largest undisturbed buffer. The shape of sub-watershed
' 4 in Figure 4, in combination with the location of the generated stream, does not allow
for a buffer along the southwestern side of the stream. The remainder of the stream,
however, has an undisturbed 150-foot buffer. In this case, such a negligible portion of
the overland drainage drains to the southwest side of the stream that 100-percent of the
sub-watershed is served by a 150-foot buffer.
5. Consider the buffer condition around lakes and ponds overlain with the generated
' stream network. The pond located near the outlet of sub-watershed 5 is overlain by the
generated stream and, therefore, considered connected to the stream network.
Consequently, the buffer contiguous to the pond - or lack thereof as is the case here - is
' accounted for in the overall assessment of the watershed buffer condition. In this
example, 75 percent of the sub-watershed is served by a 50-foot buffer. Note: the buffer
condition around the pond at the top of the watershed is not considered due to the fact
' that the pond is not overlain by the generated stream and is, therefore, not considered
connected to the stream network.
' Buffer Assessment Results
The completed findings of the existing buffer assessment are presented in Table 6. Table 6
categorizes watersheds by buffer width and percent of the watershed served by the buffer. Of
' the 1731 watersheds within the Study Area, 1313 (76 percent) were identified as having a buffer
serving at least 25 percent of the watershed area. Moreover, 785 watersheds (45 percent) were
identified as having a buffer serving 100 percent of the watershed area.
' Table 6. Study Area sub-watersheds classified by percentage of watershed
served by five buffer width categories.
Buffer Width Percent Served
(feet) 0 25 50 75 100 Sum
0 418 - - - - 418
' 50 - 79 136 154 225 594
100 14 23 65 176 278
150 - 4 7 15 88 114
' 200 - 5 8 18 296 327
Sum 418 102 174 252 785 1731
' Implementation in the Best Management Practices in Future Scenarios
HTNB land use planners provided ESC separate inventories of parcels expected to develop in
' future Scenarios 1 and 2 (see Section 2.2.2). Of the total 67.3 square mile Study Area, 10.3
square miles are anticipated to develop in Scenario 1, and 13.7 square miles are anticipated to
' develop in Scenario 2. Developing parcels occur in each of the six planning jurisdictions listed
in Table 2. The total acreage of anticipated development planning jurisdiction are reported for
Scenarios 1 and 2 in Table 7. Each parcel identified as developing in future Scenarios 1 and 2
' was considered subject to the BMP regulations of the planning jurisdiction in which it occurs.
Section 3.4 details the implementation of future BMPs in the pollutant loading model.
06-296.01 13 Western Wake Expressway ICI

Table 7. Acreage of anticipate d development per planning jurisdiction for future
Scenarios 1 and 2.
Scenario 1 Scenario 2
Year 2030 Development Year 2030 Development
Planning Jurisdiction without Expressway (acres) with Expressway (acres)
' Apex 572 616
Cary 170 129
Fuquay-Varina 1453 1813
Holly Springs 1518 1659
Unincorporated Harnett 556 2493
Unincorporated Wake 2317 2085

3.0 MODEL DESCRIPTION
3.1 PLOAD History
' PLOAD (USEPA 2001) is a simplified, GIS-based, pollutant loading model integrated with the
BASINS modeling system from the USEPA. PLOAD predicts average annual loading to provide
a general planning estimate of likely storm pollutant export from areas at the scale of a sub-
watershed using either the Export Coefficient Method (Beaulac and Reckhow 1982) or the
Simple Method (CWP 2003). PLOAD was designed to be generic so it can be applied as a
screening tool in typical NPDES stormwater permitting, watershed management, or reservoir
' protection projects. PLOAD has previously been used for watershed planning in Wake County
(CH2M Hill 2001 and 2002).
3.2 Simple Method versus Export Coeficients
As stated above, PLOAD provides two methods for calculating watershed pollutant loads, the
export coefficient method and the Simple Method. Both are simplistic, empirical models relating
watershed characteristics to pollutant loadings: the export coefficient method uses land use
areas and pollutant loading rates to estimate total watershed loads; the Simple Method
estimates watershed loads based on land use, pollutant concentrations (referred to as event
' mean concentrations [EMCs]), a runoff coefficient, and precipitation.
The loading rates and EMCs required by the respective methods are of key importance to
' producing reasonable pollutant loads. Values for these parameters are typically obtained from
scientific literature. When choosing loading rates or EMCs, a concerted effort should be made
' to acquire values that are specific to the region of the study and best reflect land uses found in
the study watersheds.
In this analysis, the Simple Method was used to estimate sub-watershed loads for total
suspended sediment, total nitrogen, and total phosphorus. The decision to use the Simple
Method over the export coefficient method was based principally on the relatively wider
availability of suitable EMC values compared to export coefficients; studies performed by CH2M
Hill (2001 and 2002), Line et al. 2002, and Hunt and Lucas 2003b provide thorough lists of EMC
values for North Carolina, yet present only a limited inventory of export coefficients. Moreover,
06-296.01 14 Western Wake Expressway ICI

the use of the Simple Method in previous watershed studies performed in Wake County was
taken as further justification for the use of the model here.
3.3 Input parameters
The Simple Method employed through PLOAD estimates pollutant loads using sub-watershed
boundaries, average annual rainfall, land use/percent impervious cover extents, and pollutant
EMCs. Optionally, areas served by BMPs and BMP pollutant removal efficiencies can also be
supplied.
Sub-watershed boundaries were derived from Study Area elevation data using ArcHydro
(CRWR 2003). Average annual rainfall was defined as the long-term (1948 to 2005) average
rainfall at Raleigh Durham Airport (SERCC 2007). Existing land use and impervious cover
extents were derived by ESC (Section 2.2.1). Land use for future scenarios were provided by
HNTB Corporation (see Section 2.2.2).
After a review of available literature on EMCs for water quality modeling, four recent reference
sources of information for North Carolina were selected for inclusion in this modeling effort
(Table 8) (CH2M HILL 2000, CH2M HILL 2002, Line et al. 2002, Hunt and Lucas 2003b). EMC
values for total suspended sediment (TSS), total nitrogen (TN), and total phosphorus (TP) were
selected by matching the 13 land uses modeled in this study ("Land Use" column) to the most
closely resembling land use in the reference sources ("Description in Reference Source"
column). Ranges of possible values culled from all four sources are listed for each pollutant.
No range is specified if only one EMC value was reported in a reference.
Stable land uses (i.e., Water, WoodG, Pasture, and Woods) were assigned EMC values from
the lower end of the range of possible values cited. The other nine land uses were given values
from the upper end of their ranges in order to consider the assumed impact of development
anticipated to occur during the modeled time period. Using this approach, the nutrient load for
existing conditions may be overestimated. However, the difference between existing and future
scenarios should better account for the impact of a land-disturbing development phase
anticipated to occur at some time during the modeled period. EMC values for unstable land
uses, with the exception of Cropland, are no greater than those measured for developed sites in
a similar-sized watershed by Line et al (2002).
Water quality sampling from similar-sized watersheds in Mecklenburg and Durham counties
(Bales et al. 1999 and Oblinger et al. 2002) supports increasing loads from developing
watersheds. Bales et al. (1999) found higher TSS loading for streams in developing watersheds
as compared to those in stable, built-out areas. Median TSS concentrations in these developing
watersheds generally were an order of magnitude greater than median concentrations in other
watersheds. Increased TSS loads were accompanied by a corresponding increase in TP loads,
with TP loads in developing watersheds twice as high as those in other watersheds. Oblinger
et al. (2002) similarly reported the highest TSS loads and the second highest TN and TP loads
from a watershed characterized as "moderately developing" from agriculture to urban land use.
While the cited studies consider both overland and in-stream loads, the observed results were
06-296.01 15 Western Wake Expressway ICI

1
1
1
1
1
1
1
i
O
E
O
J
a
L
w
N
V
W
od
.C

N 1
m L
?
O f0
C :3
O .
i

O
U
p (?

O
N
w

(0 O

N
5
a
Z 4

C

N
C7 N
a
a c0
?
2 a
N
C
O
m

V
N y O 4a) i
a
.?
? a
N
?
(p
?
C
C
C Cc O
CL

Z 'O

a O

J tp

' co

? - 'C
Vi N

p

CL

C a
co
cc

O

7
O
?
_N •
C

O
O O

U

N O
CL a

-
>
>

C
<0
(0
T
O
N U

d
C
cc

a
N
o
O rn O
c _ N
-0 C
m C
o y
m
m C N

tq C co
-p
i?
O
N -0
y a)
? ?
?
-?
N

0 ` co C O
LL O

Ix m

Ix

•

C p

'0 O
75
a a
c
o tn
a ? i
p
c
U U
'
V c
co U a N - J
o r c
a
N o
a
N O U y
O
J 3
N 2 O
~ U
O m
Q
O
r
m M
O M
O Cl?
04
N U
N
6 LO
O U)
O LO
O O
I I L6
O O L

O O i
O O O O O O O O

d
V
L
r
r
N
r
N
M
Cl)

r

r

r

r

r

r
3
O

IL r N N N M ? U') Lo LO d
O O O O O O O O O O O O
*

C Cl?

N

- N W

-
N

M

O
?

r
L

r
? ti
r

r
cqr-
O
cD
N

N
I 1 vi 9
r C) r D) N r N r W r (D d r W V r
aI r O r N N N r

d
L
r N N r r M M M M r r r r
O

Z CD r r O N f- f- f- I- tt tF' d• Lq
O r r O M 6 6 6 6 N N N N
?c
CI
O O
!? O
r 0
6 0
69
69
O
M r
N fV
i
N
O
I p a I O) O nj t p M p M p M ^ CD ^ M 4 L i O N
N M r It N LO M fl- M f- M f- g ti 0 N In CO r r

d
L

7 r N N N r M M M r r r r r
O
CO)

N
O
N
O
N N 1%
M
I?
M
?
M
ti
CD
?
N
co
co
r?
I-
co O
O
N

M 6 :3
M co b D
M (n Z3
O o
U
O N N Z N Z Z Z Z5 (n
:3 C 0
=3 :
7
+.

Q. L

o fO (O

rn?a

N uj O

a Y N

6a N N

oa N

0a 4 N

0a N O

2•
N O
2•

v
O
c
•L co fop N N d N N N O

fA V)

'a

a) _0
"
O
(n

m
a

0

LL

C N

C

C

c

C

O

a
d U

)
d O (n cu
(0 U O N m N
N 2 O O
M 2 O N
2 O N
92 2 I-
.? L
E
co 16
r- r r
o a a a a a U
N 0 O O
N LO
N O co LO •V

L
O 'D

C
N
(0 U O
' O
0
O N N N O
E O N
C O M
a O O O O O -p Of O
J 2 2 2 2 2 o U

U
O
CL
(n
N
a
F-
ly
L
0
a
N
O
t
CL
m
_o
C
f0
Z
H
C
N
O
O
L
C
(?0
O
U)
U)
H
C
N
a?
N
C
N
n
7 ?
N M
O
V N
O O N
O O O N
L O N N ? V
O N J J N 7
? 0) J J_ J 'Cc
to v 2 2 N
Q) :°.
04 04 a) 2 2 c 7
i N M

' still taken as justification for using EMC values from the upper limits of the reported ranges,
despite the fact that only overland loading is considered in this study.
EMC values for land uses with equivalent or higher impervious percentages than those cited in
the reference sources were sometimes used. For example, residential development land uses
' with 25 percent or more impervious area (House25, House30, House38, and House65) were
given EMC values from Line et al. (2002), which were measured for a residential development
with 25- percent imperviousness under the assumption that the land uses with more impervious
area had at least as much nutrient concentration. This approach is consistent with studies that
find an increase in pollutants following a rise in the land use impervious percentage. Line et al.
found an increase in TSS, TN, and TP of 256 percent, 269 percent, and 302 percent,
' respectively, from pre-development to developed land use. Similarly, Oblinger et al. (2002)
found TN and TP loads both increased in a developed watershed relative to an undeveloped
baseline watershed. Bales et al. (1999) found that residential watersheds also had higher TN
compared to watersheds with less urban land use, but this study did not incorporate BMPs into
the analysis.
' EMCs for Cropland are high but within measured TSS ranges for North Carolina (Simmons
1993) as well as national TSS, TN, and TP ranges (Harmel et al. 2006).
' Five BMPs were included in this modeling effort. Four riparian buffer BMPs of differing widths
are considered in all three modeled scenarios (Current Condition, Scenario 1, and Scenario 2).
In addition, wet detention basins (a.k.a. detention ponds) were applied only in the two future
scenarios.
' After a review of available BMP efficiency literature, percentage removal efficiencies were
selected from the NCDWQ Draft BMP Manual (NCDWQ 2005b) and the USEPA/American
Society of Civil Engineers international stormwater BMP database (Strecker et al. 2001) for
inclusion in this modeling effort (Table 9). Riparian 50-foot buffer efficiencies were taken from
the NCDWQ manual. The remaining buffer efficiencies were derived from the 50-foot buffer
efficiencies by applying the buffers in series as described in the North Carolina State University
' (NCSU) stormwater guidelines (NCSU 2006). Detention pond efficiencies were derived from
measurements contained in the stormwater BMP database in the manner suggested by
Strecker et al. (2001). BMP estimated mean influent concentration was compared to estimated
' mean effluent concentration for the modeled pollutants at wet detention pond sites where
samples fit a lognormal distribution (significance level=0.05 for the Lilliefors' form of the
Kolmogorov-Smirnov test of normality for log-transformed data). The resulting ratio of total
outflow, for all detention ponds in the database, to total inflow determined the removal efficiency
for each modeled pollutant. Removal efficiencies for areas served by both detention ponds and
buffers were calculated by applying wet ponds and buffers in series (NCSU 2006).
1 06-296.01 17 Western Wake Expressway ICI
IJ
Table 9. BMP Percentage removal efficiencies for PLOAD model.
Percentage Removal by
Pollutant
BMP TSS TN TP
Wet Detention Basin 25.00 50.00 42.00
50' Buffer (restored riparian buffer with level spreader) 85.00 30.00 30.00
'
100' Buffer (restored riparian buffer with level spreader) 97.75 51.00 51.00
150' Buffer (restored riparian buffer with level spreader) 99.66 65.70 65.70
200' Buffer (restored riparian buffer with level spreader) 99.95 75.99 75.99
' Wet Detention Basin + 50' Buffer 88.75 65.00 59.40
Wet Detention Basin + 100' Buffer 98.31 75.50 71.58
Wet Detention Basin + 200' Buffer 99.96 88.00 86.07
' TSS=Total Suspended Sediment; TN= Total Nitrogen; TP= Total Phosphorus
Wet detention basin efficiencies were chosen from the stormwater BMP database instead of the
' NCDWQ manual because of the firm belief that wet ponds do not perform at design efficiencies,
as depicted in the NCDWQ manual, for the length of time modeled. Design efficiencies for all
structural BMPs do not reflect changes over time (e.g., wet ponds lose permanent pool volume,
' buffers can develop bypasses, etc.). The lack of long-term (i.e., 10-20 years) studies of
efficiencies forced the choice of an alternative approach to modeling this assumed loss of
efficiency.
Buffer BMPs are not part of the stormwater BMP database. The literature on riparian buffer
performance contains many field studies of removal efficiencies by buffers of various widths and
vegetation types in several physiographic provinces for each of the pollutants modeled.
Published sources contain values for TSS removal efficiencies ranging from 18 to 97 percent,
' TN removal efficiencies from 1 to 89 percent, and TP removal efficiencies from 18 to 95 percent
(Daniels and Gilliam 1996, Lowrance et al. 1997, Magette et al. 1989, Peterjohn and Correll
1984, Dillaha et al. 1989, Dillaha et al. 1988, Young et al. 1980, and Mayer et al. 2006). The
' few long-term studies by Cooper et al. (1987) and Lowrance et al. (1987) suggest that wider
buffers may be required for long-term detention of sediment than those considered in the
substantially more abundant short-term studies. These longer-term studies, however, provide
' little guidance on what reduction percentages can be expected over the lifetime of this particular
study. The range of variation made it difficult to select one set of removal efficiencies to reflect
an assumed long-term loss of efficiency as modeled by Bracmort et al. (2006) and noted by
' Daniels and Gilliam (1996). Therefore, buffer efficiencies from the NCDWQ manual were
chosen despite the belief that long-term efficiencies are over-estimated.
3.4 BMP implementation
There are two methods to describe BMPs in the PLOAD model. Individual points or polygons
may be used to represent the portion of a sub-watersheds served by a BMP. If points are used,
' the information associated with each point must include the area served (an amount, e.g.
acreage) along with the BMP type. That area served is used to calculate the proportion (area
served acreage divided by entire watershed acreage) of the entire sub-watershed's load that is
1 subject to the removal efficiency of the specified BMP. The initial load leaving each parcel,
before BMPs, is calculated by the Simple Method (USEPA 2001) as follows:
Linitial = P * Pi* Rv * C* A * 2.72 / 12
06-296.01 18 Western Wake Expressway /CI
' where: Rv = 0.05 + (0.009 * 1) = Runoff Coefficient for land use, inches run/inches rain
Linitia, = Pollutant load, pounds
' P = Precipitation, inches/year
Pj = Ratio of storms producing runoff = 0.9
C = Event Mean Concentration for land use type, milligrams/liter
' A = Area of land use type, acres
The after BMP pollutant load is calculated as (USEPA 2001):
Ltotai= (Linitial* %ASBMp ) * [1- RemovalEfficiency] + (Linitia) * (1-%ASBMp))
where: Ltotal = total load leaving watershed for an individual pollutant
Linitia, = pollutant load calculated by the Simple Method
%ASBMp = percent of watershed serviced by the BMP
Removal Efficiency = percent load reduction by the BMP
For example, in a 44.67 acre watershed served by a 50-foot buffer with a removal efficiency of
' 0.85, over 75 percent of the watershed area would see a reduction from an original TSS load of
21529.33 pounds to 7804.38 pounds ([(21529.33*0.75)*(1-0.85)+(21529.33*(1-0.75))] _
7804.38).
Polygons may also be used to specify BMPs in PLOAD. Polygons perform the same function
as the area served information included with the individual points, plus polygons provide the
' additional benefit of defining the actual location of the area served within the sub-watershed.
The location of the area served by a particular BMP allows PLOAD to reduce the load
generated by the land use overlain by the BMP polygon instead of reducing the total load for an
' indiscriminant portion of the sub-watershed. The computational example becomes more
complicated, but the reduction is more precise. For example, a watershed made up of four
parcels with the House65 category served by a detention pond and a 50-foot buffer generate
the sum of TSS loads as shown in Table 10. Each land use has a defined impervious
percentage and EMC. The Before BMP TSS load is calculated by the Simple Method, while the
BMP effect is calculated using a spreadsheet outside of PLOAD.
' Table 10. Example of BMP effects using the polygon implementation method in PLOAD. The type
of BMP used in this example is 50-foot riparian buffer.
' Land Use Acres Percent Impervious EMC Before BMP TSS After BMP TSS
Cropland 7.05 1 1200 4375.54 4375.54
Road 2.94 87 84 1804.31 1804.31
' House65* 6.04 65 76 2558.80 287.86
House25 0.31 25 73 53.73 53.73
*Served by detention pond and 50-foot buffer BMPs
Existing buffers were specified using individual points. The method described in Section 2.2.3 is
too time-consuming to allow for the determination of polygons for all existing buffers and implied
' a precision that the method did not allow. The added information provided by the identification
of individual parcels that are anticipated to develop allowed the use of BMP polygons to
describe pollutant-reduction measures in the future scenarios.
06-296.01 19 Western Wake Expressway ICI
Stormwater BMPs were applied to parcels anticipated to develop in Scenarios 1 or 2.
Stormwater BMPs were modeled as wet detention basins (Table 9). All planning jurisdictions in
' the Study Area, with the exception of Harnett County, have or are developing stormwater
ordinances. Considering the time-period of this modeling effort (2005 to 2030), all stormwater
regulations currently under consideration were modeled (Table 2). Most regulations require
' some threshold area limit and/or some threshold impervious percentage to be attained before
requiring stormwater BMPs. Wake County's newest stormwater regulations are the exception
(Table 2, Lee Squires personal communication, 2/21/07). The requirements of the new
' regulation are difficult to apply uniformly across the county without detailed knowledge of future
developments. For simplicity, we reverted to modeling a previous version of the county
regulations which required stormwater BMPs for development activities that disturb 1.0 acre or
' greater and/or result in greater than 15-percent impervious coverage (Betsy Pierce personal.
Communication, 1/16/07). All future development attains at least 20-percent impervious
percentage (by definition of House20 land use) and, assuming development occurs in blocks of
1.0-acre or more, all future development in any jurisdiction in Wake County received a
stormwater BMP (i.e., wet detention basin).
' Anticipated future development is assumed to impact existing buffers. The area of anticipated
future development within a watershed was removed from the area served by existing buffers.
Buffers associated with anticipated future development were given widths that are or will likely
be mandated by local regulations.
3.5 Future Load Calculation
' Calculation of future pollutant loads from sub-watersheds without BMPs is relatively
straightforward: PLOAD uses the Simple Method to estimate pollutant loads from each land use
type in the sub-watershed then sums the loads from the discrete land use types to calculate the
total sub-watershed pollutant loads. This process, however, becomes more complicated when
BMPs are considered.
Complications arise for two reasons. First, PLOAD allows BMPs to be represented as either
points or polygons but is only capable of processing one BMP type - either point or polygon -
' per model run. Second, as explained in Section 3.4, both point and polygon BMPs were used in
this analysis: existing buffers were modeled as points, and BMPs associated with future
development were modeled as polygons. This in itself is not an issue. The problem is in
' combining the point BMP information from existing buffers anticipated to remain intact in the
future scenarios with polygon BMP information from developed parcels.
To overcome PLOAD's inability to process point and polygon BMPs simultaneously, the multi-
step procedure outlined below was developed and performed separately for future Scenarios 1
and 2. In short, the total load reduction attributable to BMPs in the future scenarios is calculated
by summing the reduction from applying Current Condition buffers to parcels not anticipated to
develop with the reduction from applying future BMPs to parcels anticipated to development.
The total reduction is removed from the estimated future loads generated without consideration
for BMPs. Note: the procedure was developed based on polygon BMP implementation
assumptions described in Section 3.4.
06-296.01 20 Western Wake Expressway /Cl
' 1. Execute three separate PLOAD runs:
' A) Future land use scenario, no BMPs considered
B) Future land use scenario, existing BMPs adjusted for development considered
C) Future land use scenario, future development BMPs considered.
' 2. Calculate load reduction from existing BMPs by subtracting Run B loads from Run A
loads.
' 3. Calculate load reduction from future development BMPs by subtracting Run C loads
from Run A loads.
' 4. Calculate total load reduction from BMPs by summing the results of Steps 2 and 3.
5. Calculate total loads by subtracting total load reduction of Step 4 from run A loads.
As further demonstration of the above procedure, an example illustrating the calculation of TSS
' from the sub-watershed depicted in Figure 5 given future Scenario 2 land use conditions is
provided. In Figure 5, 2005 aerial photography is overlain by the watershed boundary and the
Scenario 2 land use parcels. Parcels expected to develop in the future condition are outlined in
red. The procedure is completed below.
1. Execute three separate PLOAD runs:
A) TSSFuture land use scenario, no BMPs = 8847 pounds.
B) TSSFuture land use scenario, existing BMPs adjusted for development = 7558 pounds.
C) TSSFuture land use scenario, future development BMPs - 6269 pounds.
' 2. Calculate TSS reduction from existing BMPs by subtracting Run B TSS from Run A
TSS: 8847 pounds - 7558 pounds = 1289 pounds.
' 3. Calculate TSS reduction from future development BMPs by subtracting Run C TSS from
' Run A TSS: 8847 pounds - 6269 pounds = 2578 pounds.
4. Calculate total TSS reduction from BMPs by summing the results of Steps 2 and 3:
' 1289 pounds + 2578 pounds = 3867 pounds.
5. Calculate total TSS load by subtracting total TSS reduction of Step 4 from run A TSS:
' 8847 pounds - 3867 pounds = 4980 pounds.
06-296.01 21 Western Wake Expressway ICI
' 4.0 RESULTS AND DISCUSSION
Loading rates of TSS, TN, and TP (referred to cumulatively as "pollutants") vary as land use
' patterns change within the Study Area. In both future scenarios, regardless of the Expressway,
increased coverage by impervious surfaces resulted in increases of pollutant loads as well as
' observed attenuation of those loads through BMP implementation. These results are expected
as increased urbanization occurs over time. Higher pollutant loads are anticipated as currently
undeveloped, unmanaged land use categories (Woods and WoodG) are converted to
residential, commercial, and industrial categories. Nutrient export loads from forest lands are
significantly less than export loads from commercial and industrial parcels (Dodd et al. 1992,
Hunt and Lucas 2003a). However, the change from undeveloped but managed land use
' categories (Cropland and Pasture) to developed land use categories can also result in
decreased pollutant loads when only overland loads are considered, particularly when BMPs
are implemented on the new development.
4.1 Current Condition
A description of Current Condition is necessary to establish baseline parameters for analysis of
' future scenarios. Changes in land use patterns are particularly relevant for use in the PLOAD
model due to the direct correlation between land use and pollutant loading. The results of the
modeling effort estimate 2,757.38 tons (143.45 pounds per acre [pounds/acre]) of sediment,
140.40 tons of TN (7.3 pounds/acre), and 19.53 tons of TP (1.02 pounds/acre) are currently
being exported from the Study Area (Table 11; Figures 6-8, Appendix A). These values are in
line with results from similar modeling efforts performed within this ecoregion (ESC 2004).
' 4.2 Scenario 1 (without Expressway)
Study Area land use is projected to change considerably by year 2030, even without additional
' growth associated with the Expressway. By year 2030, non-Expressway related growth is
expected to result in increases of 8.0 square miles of residential and 2.3 square miles of non-
residential (industrial and commercial) land uses. Residential growth is predicted to be
scattered and located primarily in sub-urban areas away from major thoroughfares, while non-
residential growth occurs within urban centers and along roads such as US-401, NC-55, and
' NC-42. Nutrient loading in year 2030 will increase in response to increased development, while
overland sediment loading is predicted to decrease by 0.24 percent resulting from conversion of
agricultural land to land uses with higher densities of impervious surfaces. However, previous
' modeling efforts have indicated that the largest source of total sediment in urban areas (up to 60
percent) is from in-stream erosion caused by higher flow volumes and velocities resulting from
increased impervious surface coverage without appropriate BMPs.
A decrease of 0.24 percent in exported TSS and increases of 2.96 percent in exported TN and
0.28 percent in exported TP and will result from the 10.3 square miles of predicted additional
' growth relative to Current Condition (Table 11, Figures 9-11, Appendix A).
1
1
06-296.01 22 Western Wake Expressway ICI
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
C CO
N
m = r
c. m
s 3
E u
L
V ?
L V
3a 3
a•
w c c
°m
'=cMui
s
O L =
d C O
m c.
O
O O
m N Q. N
N
O E ++
M _ d =
d
i Q O >
G1 N N '?
E m c 0
O o m y
= to
Q Q C +O+
RI 'p i e-
Q (q C. 0
_ aD z
v1mc
d 4- O =
s O F+
r
E m °.' +.
V
E
N +O+ 0
_'
M M H
O a N
Q. •a N
O d d
L L
w CL ++ _
+?+ •a
O
O C 0
L O.
r- 4a 0 O
M C O z
.a 13 v
d
O M
CL 0 N
W m, m
Q.
a o _
ca = O m
I- N Q 'a
U
CD
L C L C
3
> fA > N1
O 'k O '
W W W
?
d O O f0
L R i N r
a V o o
3
m?
I
a N
LO N
o 0
F- M C
j ,C w, ? 0 0
V
L' O O
z d C
IL V N N

z C fA (a

/1
N(W
r
C c
?' d o 0
CO) 4) C
H L fC Q1
i N r
V ? o 0
IL
4)
N N
C C , Cl) M
Ca N
V)
r0+ i (0 LO
V v
a c LO ° LO
1- o rn ai ai

z C C) LO O
li
r r
? N M LO o
~ r ti LO co
N N co

o ° 3 3
'L
Rf m Z
C
N
? N
LA 41 L
co w U- W LL W N
cp
0
[1
u
4.3 Scenario 2 (with Expressway)
New development resulting from Expressway construction will be dominated by residential
growth. Improved access to rural areas is expected to stimulate residential growth, as well as
the industry, commerce, and improved transportation infrastructure necessary to support the
new residential development. Land use changes implemented in this scenario include 3.4
square miles of new growth beyond that predicted for Scenario 1 or 13.7 square miles of new
development relative to Current Condition. Residential growth will predominantly be located in
unincorporated areas of Wake and Harnett Counties that may receive water and sewer utilities
by year 2030. Commercial and industrial growth is anticipated to occur adjacent to the
Expressway and be focused at interchanges and major arterial roadways.
Scenario 2 results in nutrient export increases of 2.58 percent in exported TN and 0.13 percent
in exported TP, while there is a predicted decrease of 0.19 percent in overland sediment from
Current Condition (Table 11, Figures 9-11, Appendix A). The Scenario 2 pollutant loading
loads are within 3 percent of the Scenario 1 loads for all modeled pollutants. This similar result
for the two year 2030 Scenarios suggests that increased development, coupled by the already
stringent local land use controls and BMPs within the Study Area, is likely to reduce overland
pollutant loading as higher loading land uses (Cropland) are converted to lower loading land
uses (House20 and House25).
It is important to note that consideration of pollutant loads during the development construction
phase, long-term BMP maintenance, and in-stream sources of pollutants are outside of the
scope of these analyses but are anticipated to be important factors that will likely affect regional
water quality as development pressure continues within the Study Area regardless of
construction of the Expressway.
4.4 Effects of Best Management Practices on Pollutant Loading Estimates
Study Area land use controls are currently mandated by local and state regulations (Table 2).
By year 2030, municipalities within the Study Area may be subject to Phase II stormwater
requirements. Modeled land use controls contribute to the protection of water quality and
minimize water quality degradation as the Study Area develops. It is well known that site-
specific runoff impacts can largely be managed through land use restrictions, impervious
surface limitations, implementation of riparian buffers, utilization of stormwater facilities (basins
and treatment wetlands), and effective use of other structural BMPs (silt fencing, grass swales,
biorention areas, etc.) during and after construction.
' Benefits associated with land use restrictions imposed by current stream buffer regulations are
fully considered in these analyses. No development was considered within riparian stream
buffers.
Efficiencies associated with sediment and nutrient removal by wet detention ponds and riparian
buffers are quantified in these analyses using PLOAD. The benefits of such measures are
observed to be within published ranges. It is expected that modeled BMPs would result in
reductions in Study Area stream flow volumes and velocities but likely will not prevent stream
erosion within quickly urbanizing watersheds.
06-296.01 24 Western Wake Expressway ICI
5.0 SUMMARY
• Nutrient and sediment analyses were performed for a Study Area inclusive of watersheds
anticipated to be impacted by the Western Wake Expressway (R-2635) in Wake and Harnett
Counties, North Carolina. The purpose of the study is to estimate the percentage difference
in pollutant loading between "with Expressway" and "without Expressway" development
levels, Scenarios 1 and 2, respectively. These analyses have been requested by the
NCDWQ to evaluate potential water quality impacts associated with future growth in the
Study Area with and without the Expressway.
• The 67.3 square mile Study Area is comprised of the headwaters of several 303(d)-listed
streams and includes watersheds that drain to both the Neuse and Cape Fear River basins.
The Study Area is believed by project planning participants to be the area most likely to
experience growth from the Expressway that would not develop to the same degree
otherwise. The three main named-streams within the Study Area (Middle, Kenneth, and
Neills Creek) all contain multiple populations of sensitive aquatic organisms that are of
interest to federal and state regulatory agencies.
• Predicted future land uses were estimated for both Scenarios 1 and 2 in year 2030. Use of
Best Management Practices (BMPs), such as riparian buffers and wet detention ponds were
considered in both future scenarios. Thirteen distinct land use categories were generated
and provided by HNTB Corporation.
• Analyses performed involved quantitative pollutant loading modeling using the PLOAD
watershed model available in USEPA's Better Assessment Science Integrating point and
Nonpoint Sources (BASINS) modeling system. Overland pollutant loads (sediment,
nitrogen, and phosphorus) were predicted for each land use scenario. Riparian buffers were
estimated based upon their current extent and width for Current Condition and the
controlling regulations or ordinances in the two future scenarios. BMPs (stormwater
controls) were implemented in areas anticipated to development in the future scenarios.
• Predicted pollutant loads increase as impervious area increases. This trend is further
supported in scientific literature (Dodd et al. 1992, Hunt and Lucas 2003a). Low-density
residential land use categories are responsible for the largest increases in predicted
pollutant loads in all modeled scenarios.
• Scenario 1 modeling predicts a pollutant load decrease of 0.24 percent for TSS and
' pollutant load increases of 2.96 percent for TN and 0.28 percent for TP relative to Current
Condition.
• In comparison to Scenario 1, Scenario 2 modeling predicts pollutant load reductions in TSS
of 0.05-percent, TN of 0.38-percent, and TP of 0.15-percent. The difference in pollutant
loads between the two scenarios is reflective of the 3.7 square miles of additional
development attributable to the Expressway in Scenario 2.
• When only considering overland pollutant loads, the additional development and associated
increase of impervious surfaces result in pollutant loads that appear to be incongruous with
06-296.01 25 Western Wake Expressway ICI

1

the knowledge that development impairs water quality due to increased pollutant loads.
However, the change in impervious area, coupled with the addition of BMPs in areas that
were previously unmanaged, suggests that when performing holistic watershed analyses,
specific attention should be placed on whether new development occurs on agricultural land
or on previously unmanaged land. In PLOAD, when agricultural land converts to a
developed land use category, overland pollutant loads are expected to decrease, since in-
stream hydrographs and stream erosion have not been considered for a total pollutant load.
When unmanaged (forested) land coverts to a developed land use category, all overland
pollutant loads increase, but the net change is muted by other areas where the conversion
of agricultural land controls the total load in these holistic analyses. Overall, these analyses
suggest that any land use changes attributable to the Expressway result in a less than 1-
percent difference in overland pollutant loads when compared to the ambient growth
pressure within the Study Area.
' Given detailed land use inputs, PLOAD has demonstrated an ability to predict reasonable
estimates of overland nutrient and sediment export loadings resulting from changes in land
use when compared to other published results (Dodd et al. 1992; Hunt and Lucas 2003a,
' ESC 2004). Additionally, loadings have been predicted to be reduced when reduction
efficiencies of BMPs are considered.
1
1
1
1
r
n

1
06-296.01 26 Western Wake Expressway ICI

6.0 REFERENCES
' Bales, J.D., Weaver, J.C., and J.B. Robinson. 1999. Relation of land use to streamflow and
water quality at selected sites in the City of Charlotte and Mecklenburg County, North
' Carolina, 1993-98. WRIR 99-4180. U.S. Geological Survey, Reston, Virginia.
Beaulac, M. and K. Reckhow. 1982. An examination of land use - nutrient export relationships.
Water Resources Bulletin 18 (6): 1013-1024.
Bracmort, K.S., M. Arabi, B.A. Frankenburg, B.A. Engel, and J.G. Arnold. 2006. Modeling Long-
Term Water Quality Impact of Structural BMPs. Transactions of the ASABE. Vol. 49(2):
367-374.
Center for Research In Water Resources (CRWR). 2003. ArcHydro Online Support System.
Available: http://www.crwr.utexas.edu/giswr/hydro/ArcHOSS/index.cfm [January 16,
2007].
' Center for Watershed Protection (CWP). 2003. Impacts of impervious cover on aquatic
' systems. Watershed Protection Research Monograph No. 1. Center for Watershed
Protection, Ellicott City, MD 21043
CH2M Hill. 2001. Wake County Watershed Modeling. Available:
http://projects.ch2m.com/WakeCounty/Docs/TM4%2OWatershed%20Modeling%20FinaI-
pdf [January 16, 2007].
' CH2M Hill. 2002. Planning Level Water Quality Assessment for Town of Cary. Town of Cary.
Available: http://www.townofcary.org/northwest/watergualitymodel.pdf [January 16,
' 2007].
CH2M Hill. 2000. Urban Stormwater Pollutant Assessment.
Cooper, J.R., J.W. Gilliam, R.B. Daniels, and W.P. Robarge. 1987. Riparian areas as filters for
agricultural sediment. Soil Sci. Soc. Am. J. 51(2); 416-420.
' Daniels, R.B. and J.W. Gilliam. 1996. Sediment and chemical load reduction by grass and
riparian filters. Soil Sci. Soc. Amer. J. 60; 246-251.
' Dillaha, T.A., R.M. Reneau, S. Mostaghima, and D. Lee. 1989. Vegetative filter strips for
agricultural non-point source pollution control. Trans. Amer. Soc. Agric. Engin. 32; 513-
519.
Dillaha, T.A., J.H. Sherrard, D. Lee, S. Mostaghimi, and V.O. Shanholtz. 1988. Evaluation of
' vegetative filter strips as a best management practice for feed lots. J. Water Pollut.
Contr. Fed. 60; 1231-1238.
' 06-296.01 27 Western Wake Expressway ICI

' Dodd, R.C., G. McMahon, and S. Stichter. 1992. Watershed Planning in the Albemarle-Pamlico
Estuarine System: Annual Average Nutrient Budgets. North Carolina Department of
' Environmental Health and Natural Resources. Report No. 92-10.
EcoScience Corporation (ESC). 2004. Secondary and Cumulative Impact Report: Nutrient and
' Sediment Analyses for the Clayton Bypass (R-2552) in Johnston and Wake Counties,
North Carolina. Technical Report submitted to N.C. Department of Transportation.
18pp.
' Floodplain Mapping Program (NCFLOOD). 2007. Neuse River Basin Light Detection and
Ranging Data: Bare Earth Resolution. Website citation: www.ncfloodmaps.com.
Harmel, D., S. Potter, P. Casebolt, K. Reckhow, C. Green, and R. Haney. 2006. Compilation of
measured nutrient load data for agricultural land uses in the United States. JOURNAL
OF THE AMERICAN WATER RESOURCES ASSOCIATION 42 (5):1163-1178.
Harnett County Government. 2007. Harnett County Watershed Supply Management and
Protection Ordinance. Website citation:
http://www.harnett.org/downloads/Watershed%200rdinance.pdf.
' Hunt, B. and A. Lucas. 2003a. Development of a Nutrient Export Model for New Developments
and Establishment of BMP Removal Rates for Stormwater BMPs in the Tar-Pamlico
River Basin. Biological and Agricultural Engineering, North Carolina State University.
' For the North Carolina Department of Environmental and Natural Resources, Tar-
Pamlico Stormwater Group.
' Hunt, B. and A. Lucas. 2003b. Development of a Nutrient Export Model for Development in the
Tar-Pamlico River Basin. City of Washington Stormwater Management Program for
Nutrient Control Appendix B.
Line, D.E., N. M. White D.L. Osmond, G.D. Jennings, and C.B. Mojonnier. 2002. Pollutant
Export from Various Land Uses in the Upper Neuse River Basin. Water Environment
Research. Vol. 74 (1): 100-108
' Lowrance, R., L.S. Altier, J.D. Newbold, R.R. Schnabel, P.M. Groffman, J.M. Denver, D.L.
Correll, J.W. Gilliam, J.L. Robinson, R.B. Brinsfield, W. Lucas, and A.H. Todd. 1997
Water quality functions of riparian forest buffers in Chesapeake Bay watersheds.
Environ. Manage. 21(5); 687-712.
Magette, W.L., R.B. Brinsfield, R.E. Palmer, and J.D. Wood. 1989. Nutrient and sediment
' removal by vegetated filter strips. Trans. Amer. Soc. Agric. Eng. 32(2); 663-667.
Mayer, P.M., S.K. Reynolds, M.D. McCutchen, and T.J. Canfield. 2006. Riparian buffer width,
vegetative cover, and nitrogen removal effectiveness: A review of current science and
regulations. USEPA/600/R-05/118. Cincinnati, OH, U.S. Environmental Protection
Agency, 2006.
06-296.01 28 Western Wake Expressway ICI
i
' North Carolina Division of Water Quality (NCDWQ). 1996. Cape Fear River Basinwide Water
Quality Management Plan. N.C. Department of Environment and Natural Resources,
' Water Quality Section, Raleigh, NC.
North Carolina Division of Water Quality (NCDWQ). 2000. Cape Fear River Basinwide Water
' Quality Management Plan. N.C. Department of Environment and Natural Resources,
Water Quality Section, Raleigh, NC.
' North Carolina Division of Water Quality (NCDWQ). 1998. Neuse River Basinwide Water
Quality Management Plan. N.C. Department of Environment and Natural Resources,
Water Quality Section, Raleigh, NC.
North Carolina Division of Water Quality (NCDWQ). 2002. Neuse River Basinwide Water
Quality Management Plan. N.C. Department of Environment and Natural Resources,
' Water Quality Section, Raleigh, NC.
North Carolina Division of Water Quality (NCDWQ). 2004. North Carolina Water Quality
' Assessment and Impaired Waters List (2004 Integrated 305(b) and 303(d) Report).
Website citation: http://h2o.enr.state.nc.us/tmdl/General 303d.htm#Downloads.
North Carolina Division of Water Quality (NCDWQ). 2005a. Cape Fear River Basinwide Water
Quality Management Plan. N.C. Department of Environment and Natural Resources,
Water Quality Section, Raleigh, NC.
' North Carolina Division of Water Quality (NCDWQ). 2005b. Updated Draft Manual of
' Stormwater Best Management Practices. North Carolina Department of Environment
and Natural Resources Division of Water Quality.
North Carolina Division of Water Quality (NCDWQ). 2006. North Carolina Water Quality
Assessment and Impaired Waters List (2006 Integrated 305(b) and 303(d) Report).
Public Review Draft. Website citation:
' http://h2o.enr.state.nc.us/tmdI/documents/20061RPublicReviewDraft pdf.
North Carolina Division of Water Quality (NCDWQ). 2007. Surface Freshwater Classifications
' Used in North Carolina. Website citation: http://h2o.enr.state.nc.us/wswp/higualty.htm1.
North Carolina State University (NCSU). 2006. Stormwater and Nutrient Management
' Guidelines. 2006. Stormwater Management Environmental Health and Public Safety
Center, North Carolina State University.
' Oblinger, CJ, T.F. Cuffney, M.R. Meador, and R.G. Garrett. 2002. Water-quality and physical
characteristics of streams in the Treyburn development area of Falls Lake watershed,
North Carolina, 1994-98. WRIR 02-4046. U.S. Geological Survey, Reston, Virginia.
' Peterjohn, W.T. and D.L. Correll. 1984. Nutrient dynamics in an agricultural watershed:
Observations on the role of a riparian forest. Ecology 65(5); 1466-1475.
' 06-296.01 29 Western Wake Expressway /Cl

Simmons, Clyde E.. 1993. Sediment Characteristics of North Carolina Streams, 1970-79.
Water-Supply Paper 2364. U.S. Geological Survey, Reston, Virginia.
' Smith, S.D. (Unpublished). Investigation of Piedmont stream origins in the Neuse River Basin,
North Carolina. MS Thesis, North Carolina State University, Raleigh, North Carolina.
' Southeast Regional Climate Center (SERCC). 2007. Period of Record Monthly Climate
Summary. Available: http://cirrus.dnr.state.sc.us/cgi-bin/sercc [January 16, 20071.
Strecker, E.W., M.M. Quigley, B.R. Urbonas, J.E. Jones, and J.K. Clary. 2001. Determining
Urban Stormwater BMP Effectivenes. Journal of Water Resources Planning and
' Management. Vol. 127 (3):144-149.
Town of Apex. 2007. Unified Development Ordinance. Watershed Protection Overlay Districts.
' Website citation: http://www.apexnc.org/docs/plan/udo/sections/section006 001.pdf.
Town of Cary. 2007. Stormwater Department, Buffer Facts. Website citation:
' http://www townofcarv org/depts/dsdept/engineering/engproi/stormwater/bufferfacts htm.
Town of Holly Springs. 2005. 10-Year Comprehensive Growth Plan. Website citation:
' http•//hollyspringsnc us/dept/pIanning/policy/10year/ch8 pdf.
Wake County Government. 2007. Wake County Land Use Plan. Website citation:
' http://www.wakegov.com/NR/rdonlyres/8F9350C9-E8F4-4BCE-97BB-
F18572E3CF5F/0/ChapterVWaterSupplyWatershed pdf.
' U.S. Army Corps of Engineers (USAGE), United States Environmental Protection Agency
(EPA), North Carolina Wildlife Resources Commission (NCWRC), Natural Resources
Conservation Service (NRCS), and North Carolina Division of Water Quality (NCDWQ).
2003. Stream Mitigation Guidelines. State of North Carolina.
' U. S. Environmental Protection Agency (USEPA). 2001. PLOAD version 3.0: An ArcView GIS
Tool to Calculate Nonpoint Sources of Pollution in Watershed and Stormwater Projects
- User's Manual. United States Environmental Protection Agency, January 2001.
' U.S. Fish and Wildlife Service USFWS . 2007a. Harnett County Endangered Species,
Threatened Species, and Federal Species of Concern (online). Available: hftp:Hnc-
es.fws.gov/es/countvfr.html [January 29, 2007]. U.S. Department of the Interior.
[October 20061.
' U.S. Fish and Wildlife Service (USFWS). 2007b. Wake County Endangered Species,
Threatened Species, and Federal Species of Concern (online). Available: hftp:Hnc-
es.fws.gov/es/countvfr.html [January 29, 20071. U.S. Department of the Interior.
[October 2006].
' 06-296.01 30 Western Wake Expressway ICI
' Young, R.A., T. Huntrods, and W. Anderson. 1980. Effectiveness of vegetated buffer strips in
controlling pollution from feedlot runoff. J. Environ. Qual. 9; 483-487.
06-296.01 31 Western Wake Expressway ICI

Appendix A
Figures
06-296.01 Western Wake Expressway ICI
m ' m = m m m m m = m m m m m

I I
L
_i 4 f '

`O' W
a N C 3 C C

0-
< C m

CL
<
h
Wo
'
cn D
< <°. D n
C7 a
f
W
t

cl)

a)

3 C D (a

Z
W S N

L
O

a co
o a
\ 1

m

?
n

i

f

.

y
N
7
CL
i`
;'
fD - -
4;
a)
3 N)
o CD
CL
m
fl t'

1
f ? I ?

.
'
I
r

i
r
/ A
' a

-
N
X { y
?

N 4 ,

a
17

1 <

CD (D
A Oo ?
n yb Y \\I jt _ 1 / S - 4 ? ?
o 1 _ [
$ Z
??
4
4
1
1
_

4

m ? a
6111-N

1 tc
( i `. I
lli
4;;;-,

m
n n
a o
S
m 2.

o W 0c ?_ m o
c " D D0 yD?

m
o
co
?
v
-0
-.1 D
o?
00 n
o CD V) T` M
m?
Z j
p? ?p
C/)
ZD
?; D Z
o.? -
N)
o

N
v
o z o

i

^. .. - -
?
p w cn
C n
C fn
C oo D y - 1
i
O W 6 7
7 {
1
III
w co

CD CD
w 0
m n ? o 3 r s ??
!
m
3 y
N 3
a W
Z C
y .

CD

(1) ?
`? , 9 r ?? r ns_?
1 ,: J ti(ti?

N o

rn

?

'

G

?
O

,• ? •?,y I ? \, ? 7 r

s: 0
CD ..
CD

R1 l
?
`
.
`
`•?: It W{

to
i 1.
1? A
_
D
fn

F
of ;
i
3 FK 1
lpl? \ ;f-,-)l
m O V
N x j ?
n
m ''AA N T_? °' m CAM
y/ D CD l'I
Z ?.
o° m m Z v Q° m
C D m Z O
npCl) 2) ;v 0Cl) -q o
CD x
r" CD n D Xpm °.n
?m z ;D CD
N N Omm ?g N w
, r c z
v
o 0 0 ) CAD
own 8y: FIGURE
FUTURE POLLUTANT LOADING EXAMPLE TBA
EcoScience Ckd 8y:
WESTERN WAKE EXPRESSWAY ICI Data: MAR M 2007 rc
Corporation 5
Raleigh, North Carolina
- Wake County, North Carolina ProIect. 06-296.01
?=I
O C o 0 o O = X'
j ,?- O O O O , N
O y
D A °d •?
00 @ (o 8'00'0
C O O O V
:3 CP
C O
a
N
N

0
n v v v v
C O
O C
d 00 O O
7
° S

3
0 01
D S A
Up
0
) O O 0

0
C:
CL
m

m ?

o v v v c CD CO)
C) C? CZ) C) H m
D
m OW Cn °O O O v f?xD N
CL y
N c
.Z 4)
m n o
f
n co ' 2 0
o 0K0n z
z
o m0Do? st ;u m p ,O o
o zDmv??O? Cv n?D? < a O
m 'o mrOmD °m NArn N A? C~?D• ??
D" m
O;o zr 70 ?m?
N N X O -i Nc z
NO V? W 7. D o• 0 ("?
O ? v y ? m

'0
0
n co v N J v O m
c D. CT cn O
CIt y
co @ W cn O A 3
C N v
7 W
CL p
n? c
a
v

?,1®??
w
L1
o
= o
n
v ? ? v O ,
N N
J7 V7 O ' N
C O. C §
O

0 CD W W CT C
"
c m - O
CD
CL ? -?
c x
C
N y

d

m
n n
a
y p
?

U)
?
m
v
2 0
m

?,
z

0
o
o
0 o
mOD??
za X
om C?

o

v CA
m ou
m .
C: o Dm
0D 00 ny?m

M

PO
??
Na
D"
X
X momr
0
?.? ?m?

7 o
N
m

~

m N) Z
Cl) L p
•'1 •-.
. p n
o N 0 W
N w
CD
am

? 1 I ? ?
LJ l? o 0
p A W N O 3 O UJ
d N
7 G A
D J ?
A W N y S d
W
o Z X O
W N
C O
a y
v
?
m
m o 0
n n ? ? m 2
0
C3 al
m
0
NCO= Z° X
o mopyp
00 C >M-nxv 0Cl) -yl ? z
M r0 o o (gTIT1
D" ?m?r m O
?m? N
N N X ov C Z
NJ M "0
CD cn CD'
O ? O _
m m ' m m m m m m m m m m m = m
?=I
O
(7 (n j V V V C
O A O 7
O O. O O O O , C K
? O O O O N
D o rn a °o
co m 0 0 o
02)-. O O O
CJl
CL co
D) C
7
CL
N

? ? , ?'
p O
'
? W
D1
`_ 7 O
N O
p C W* N
.
c cn
C < O U7 i O Q -.1 ,+ f?D
,?.. CD < ' N H
<
o D o cn y O
O Ct
?
o CD C
m
m
T co x
a Iv o U) V
PM
C CD
Cl) fn
CO)
2)

ca 0
ZO

O C c U1 IV o - =
O m
o u ,

C
° n
c
m Q.
=3 CD l< < a
I °o D rn cno cn m
co
"' °
-n < N
=w
m
p
a m
=3 a co
CL o k l3 N
y
N N ?
N D y
U H

07
i I
m
n o
n O TT
N m
v
= o

T W O
mm
Cl) M
z
m> v m

;L 90 n
n O ?
?
Ill !? `° y, m N Z i ,.
N N A
o Q m m
00z
Nm
z M TI
D Z p•?
o CD O -
i
O p y d CD

L1?11 ?a o
CT CT O y X
D w
°
? w a' cn
co
c
W
o
w c
4
n
v
,?Z

?o
N 3
p cn
--• O O
Ca y
C: CL
CD
'
CD
"
7 C
D l<
O
`< o D N) ,?
•
O O C
h
UD m m ° =
'
C CL o
O W X K s
C1 Cll O
?'
'
Z m O
C C
D
U! H
N
`G
D)

A4

? ? 1 ® ?
L_i 0 30
p CD ? j v v
p c)
C
m
I G
CD
° CL U1 w
O
D cn ° H G CD

O
?
CD
0 CL m c
CL O X'p N
y
C N
N

-Of
m C7 o T
n a - v X Z m i
co a)
o
0mm? m m C7?
N?< C? n z
o 0
mwr?0 D 0 9' - o
o z?0-mz 0? M> Cl)
o O
D? Z ny M
V)mm ° ?•
m m u Ko /M nZI?TI oCD
N CD
N vviirnz?rvZ C: D z
z
0 CD J v-3v N '< v

p c a w N) o O. m
A A W N y X•
D - U
co c ?
7 W
CL o
m c
a
m

L?oo??aao
n
N
o
=
O
? 3

C O O CA r
O
p CC

f?D
n
L
CD
N
01 ?
< CL
O
7 2 <

?? fD
O
.<
o
y n
0
W O O c=i
M
m
O
CD N N m M O
o X. x
CL
m
CL
pj ? N
y
? Ol

L
ioa?1oo o o
_
o ?? a
ooQ
c N a O O N
G CT O
d < lD
.: 7
_
n
07 N D C11 CJ v
0 S G1
°
a v m mx
CL oW X N
N W ? '? y
y Z N
d

(n
C) a
C3 0-0 m
m
D
Z 0W< vp= z
0 O z9, X -0D M>N
DOoOtmi?=0 ?? ??cmi?D
?1 m C 1? xvcECOm on ?m?
a NmZ zcvnZ D Z
O N O v Z y
Ott
X O Q
z?Cl?
o p
o r+
CD