20120285 Ver 1_Report_20111001

Gaston East-West Connector
Indirect and Cumulative Effects
Water Quality Analysis - Draft
Cleveland, Gaston, and Mecklenburg Counties, North Carolina;
York County, South Carolina
(STIP U-33211
Prepared for the North Carolina Turnpike Authority
� NORTH CAROLINA
; � Turnpike Authority
Prepared by
nT�i N s
1616 East Millbrook Road, Suite 310
Raleigh, North Carolina 27609
October 2011

This Page Left Blank Intentionally

Gaston East-West Connector Wa ter Quality Analysis
October 2011- Draft
EXECUTIVE SUMMARY
The North Carolina Turnpike Authority (NCTA), operating as part of the North Carolina Department of
Transportation (NCDOT), proposes the Gaston East-West Connector as a controlled-access toll road from I-85
west of the City of Gastonia in Gaston County, NC to I-485 near the Charlotte Douglas International Airport in
Mecklenburg County, NC. The purpose of the Gaston East-West Connector (the Project) is to improve east-west
transportation mobility in the area around the Gastonia and other municipalities in southern Gaston County to
the City of Charlotte metropolitan area. Importantly, the project will establish direct access between the rapidly
growing areas of southeast Gaston County and western Mecklenburg County. The Gaston East-West Connector,
which is locally known as the Garden Parkway, is included in the State Transportation Improvement Program
(STIP) as project U-3321.
The Gaston East-West Connector Draft Environmental Impact Statement (DEIS), circulated in April 2009,
included a summary of the qualitative indirect and cumulative effects (ICE) analysis prepared for the Detailed
Study Alternatives (Indirect and Cumulative Effects Assessment for the Gaston East-West Connector, Louis Berger
Group, Inc., March 2009). The U.S. Environmental Protection Agency (EPA), U.S. Fish and Wildlife Service
(USFWS), N.C. Department of Environment and Natural Resources (NCDENR), and N.C. Wildlife Resources
Commission (NCWRC) provided comments on the DEIS. Regarding indirect and cumulative effects, the
Resource Agencies requested additional quantitative data on the Preferred Alternative.
A quantitative indirect and cumulative effects study was prepared for the Preferred Alternative (Gaston East-
West Connector Quantitative Indirect and Cumulative Effects Analysis, Louis Berger Group, Inc., August 2010).
This report is summarized in the ProjecYs Final EIS, circulated in December 2010. In a comment letter on the
Final EIS dated February 21, 2011, the NCDENR Division of Water Quality (NCDWQ) noted that "NCDWQ will
require additional modeling of pollutant loadings for this project."
This report presents a quantitative water quality analysis performed in response to NCDWQ's requirement, and
to determine how estimated induced land use changes resulting from the Project may affect water quality
throughout the 265-square mile Study Area defined for this analysis. The water quality analysis involved
constructing watershed models for the nine 12-digit hydrologic units (HUs) comprising the Study Area using the
BasinSim build of the Generalized Watershed Loading Functions (GWLF) model. The watershed models were
used to estimate annual runoff and annual overland pollutant loading rates of total nitrogen (TN), total
phosphorus (TP), total suspended sediment (TSS) produced from the three land use scenarios: a year 2006
baseline condition (Baseline Condition), year 2035 future condition without the Project (2035 No Build), and
year 2035 future condition with the Project (2035 PA).
Five of the nine HUs composing the Study Area contain streams or waterbodies on the 2010 North Carolina or
South Carolina 303(d) list (NCDWQ 2010a, SCDHEC 2010): Catawba Creek, Duharts Creek-South Fork Catawba
River, Lower Crowders Creek, Mill Creek-Lake Wylie, and Upper Crowders Creek. The Project alignment
intersects all five HUs. Further, interchanges are planned in all five HUs. The watershed model results for the
Catawba Creek, Lower Crowders Creek, and Mill Creek-Lake Wylie HUs indicate increased runoff and TN and TP
loads in the 2035 PA scenario compared to the 2035 No Build scenario. The model results indicate increased
runoff and TP loads for the Duharts Creek-South Fork Catawba River and Upper Crowders Creek HUs as well, but
lower TN loads. An increase in TSS load is expected for 4 of the 5 HUs containing 303(d)-listed waters, Mill
Creek-Lake Wylie HU being the exception. Of the five HUs, the Catawba Creek HU experiences the largest
indirect effects: the HU incurs the greatest increase in urban land use and, in turn, the largest increase in

Gaston East-West Connector Wa ter Quality Analysis
October 2011- Draft
impervious surface coverage. As a result, the Catawba Creek HU is projected to have the greatest increases in
runoff and nutrient loading rates.
For the Study Area as a whole, all nine HUs are anticipated to experience some degree of direct or indirect
effects from the Project. Direct effects result from the additional paved surface and right-of-way associated
with the Project alignment. Indirect effects are in the form of increased residential development or
commercial/industrial/office development. The result of these effects are apparent in the increases in runoff
and nutrient loading rates projected for all HUs. As mentioned above, the Catawba Creek HU experiences the
largest indirect effect and is projected to have the largest increase in runoff and nutrient loadings. Over 80
percent of the land consumed by the direct and indirect effects of the project is forecasted to come from
existing forest and pasture lands.
It should be noted that the analysis documented in this report was not conducted for the purpose of predicting
the specific amount of pollutants delivered at the outlet of each modeled HU. Rather, the aim of the analysis
was to determine the magnitude of runoff and pollutant change between the 2035 No Build and 2035 PA
scenarios. This measurement indicates the trend of water quality over time in each HU and the Study Area as a
whole. Also, in terms of BMPs, the analysis only considered riparian buffers. No site-specific BMPs -
bioretention basins, stormwater ponds, grass swales, etc. - are accounted for in the results. Consequently, the
watershed model overestimates pollutant loadings from areas that would otherwise receive stormwater
treatment. Site-specific BMPs were omitted due to a lack information regarding the projected future
development. However, the three of the four counties intersected by the Study Area -Gaston and Mecklenburg
Counties, NC and York County, SC-are NPDES Phase II communities. Under this designation, the counties must
require land disturbances greater than or equal to 1 acre to implement runoff and pollutant reduction measures
(USEPA 2005). Compliance with Phase II rules would likely result in reduced runoff and nutrient loading rates
compared to those produced by the modeled 2035 No Build and 2035 PA scenarios.
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Gaston East-West Connector Wa ter Quality Analysis
October 2011- Draft
TABLE OF CONTENTS
ExecutiveSummary .....................................................................................................................................................i
Tableof Contents ......................................................................................................................................................iii
Figures....................................................................................................................................................................... iv
Tables iv
Appendices................................................................................................................................................................ iv
1.0 Introduction ....................................................................................................................................................1
2.0 Study Area .......................................................................................................................................................2
2.1 Study Area Definition .................................................................................................................................2
2.2 Water Resources ........................................................................................................................................3
2.2.1 Existing Water Quality ........................................................................................................................7
2.2.2 Existing Water Quality Measures .......................................................................................................9
3.0 Water Quality Analysis Approach ................................................................................................................ 11
3.1 BasinSim Description ............................................................................................................................... 11
3.2 Input Parameters ..................................................................................................................................... 12
3.2.1 Land Use .......................................................................................................................................... 14
3.2.2 Soils ..................................................................................................................................................15
3.2.3 Curve Numbers ................................................................................................................................ 16
3.2.4 Streams ............................................................................................................................................16
3.2.5 Weather Stations ............................................................................................................................. 16
3.2.6 Point Sources ................................................................................................................................... 17
3.2.7 Surface Elevation ............................................................................................................................. 17
3.2.8 Erosion and Sediment Yield ............................................................................................................. 17
3.2.9 Septic Areas ..................................................................................................................................... 18
3.2.10 Best Management Practice (BMP) Implementation ....................................................................... 18
3.3 Model Calibration .................................................................................................................................... 21
4.0 ResultsandDiscussion .................................................................................................................................23
4.1 Baseline Condition ................................................................................................................................... 26
4.2 2035 No Build .......................................................................................................................................... 27
4.3 2035 Preferred Alternative (PA) .............................................................................................................. 27
4.4 ResultsTables ..........................................................................................................................................28
5.0 Conclusions ..................................................................................................................................................34
6.0 References ................................................................................................................................................... 36
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Gaston East-West Connector Wa ter Quality Analysis
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FIGURES
Figure 1: GWLF surface and sub-surface hydrology and loading pathways (adapted from Haith et al. 1992)....... 12
Figure 2: Calibration and Validation Model Monthly Streamflows Plotted with Observed Monthly Streamflow. 23
TABLES
Table 1: Land Use Scenarios Considered in the Quantitative Water Quality Analysis ...............................................2
Table 2: Study Area Hydrologic Units (HUs) ...............................................................................................................3
Table 3: Classifications and Use Support Ratings of Named Study Area Waterbodies in North Carolina .................4
Table 4: Classifications of Study Area Waterbodies in South Carolina ......................................................................6
Table 5: Study Area Waterbodies on the North Carolina 2000- 2010 303(d) Lists ..................................................8
Table 6: Study Area Waterbodies on the South Carolina 2000 - 2010 303(d) Lists ..................................................9
Table 7: Study Area Stormwater BMPs ................................................................................................................... 10
Table 8: Model Inputs and Data Sources ................................................................................................................. 13
Table 9: NCLD Land Cover Categories for the Study Area ....................................................................................... 14
Table 10: Quantitative ICE Land Use Class CN Assignments ................................................................................... 16
Table11: USLE Cover factors ................................................................................................................................... 17
Table 12: Study Area Regulated Buffer Widths ....................................................................................................... 19
Table 13: Average Buffer Width by HU ................................................................................................................... 20
Table 14: GWLF Buffer Reduction Efficiencies ........................................................................................................ 20
Table 15: CN and Nitrogen and Phosphorus Buildup Rates for Urban Areas for the Baseline, 2035 No Build
(Build), and 2035 PA (PA) Scenarios ........................................................................................................................ 25
Table 16: Reported Significant Figures .................................................................................................................... 28
Table 17: Comparison of Annual Runoff Results for Baseline Condition, 2035 No Build, and 2035 PA Scenarios. 30
Table 18: Comparison of Annual Total Nitrogen (TN) Results for Baseline Condition, 2035 No Build, and 2035 PA
Scenarios. ................................................................................................................................................................ 31
Table 19: Comparison of Annual Total Phosphorus (TP) Results for Baseline Condition, 2035 No Build, and 2035
PAScenarios ............................................................................................................................................................ 32
Table 20: Comparison of Annual Total Suspended Sediment (TSS) Results for Baseline Condition, 2035 No Build,
and2035 PA Scenarios ............................................................................................................................................ 33
APPENDICES
A. Large Format Figures
B. Select Figures from the Gaston East-West Connector Quantitative Indirect and Cumulative Effects
Analysis
C. GWLF-E and RUNQUAL-E Input Parameters
D. Correspondence with N.C. Division of Water Quality Regarding Analysis Methodology
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Gaston East-West Connector Wa ter Quality Analysis
October 2011- Draft
1.0 INTRODUCTION
The North Carolina Turnpike Authority (NCTA), operating as part of the North Carolina Department of
Transportation (NCDOT), proposes the Gaston East-West Connector as a controlled-access toll road from I-85
west of the City of Gastonia in Gaston County, NC to I-485 near the Charlotte Douglas International Airport in
Mecklenburg County, NC. The purpose of the Gaston East-West Connector is to improve east-west
transportation mobility in the area around the Gastonia and other municipalities in southern Gaston County to
the City of Charlotte metropolitan area. Importantly, the project will establish direct access between the rapidly
growing areas of southeast Gaston County and western Mecklenburg County. The Gaston East-West Connector,
which is locally known as the Garden Parkway, is included in the State Transportation Improvement Program
(STIP) as project U-3321. For the purposes of this report, the Gaston East-West Connector will be referred to as
the Project.
The Gaston East-West Connector Draft Environmental Impact Statement (DEIS), circulated in April 2009,
included a summary of the qualitative indirect and cumulative effects (ICE) analysis prepared for the Detailed
Study Alternatives (Indirect and Cumulative Effects Assessment for the Gaston East-West Connector, Louis Berger
Group, Inc., March 2009). The U.S. Environmental Protection Agency (EPA), U.S. Fish and Wildlife Service
(USFWS), N.C. Department of Environment and Natural Resources (NCDENR), and N.C. Wildlife Resources
Commission (NCWRC), collectively referred to as the Resource Agencies hereafter, provided comments on the
DEIS. Regarding indirect and cumulative effects, the Resource Agencies requested additional quantitative data
on the Preferred Alternative.
A quantitative indirect and cumulative effects study was prepared for the Preferred Alternative (Gaston East-
West Connector Quantitative Indirect and Cumulative Effects Analysis, Louis Berger Group, Inc., August 2010).
This report is summarized in the projecYs Final EIS, circulated in December 2010. In a comment letter on the
Final EIS dated February 21, 2011, the NCDENR Division of Water Quality (NCDWQ) noted that "NCDWQ will
require additional modeling of pollutant loadings for this project."
Subsequent to the August 2010 version of the quantitative ICE assessment report circulated with the Final EIS,
the quantitative ICE assessment was updated (Gaston East-West Connector Quantitative Indirect and Cumulative
Effects Analysis, Louis Berger Group, Inc., July 2011) to include the Fites-Creek Catawba River subwatershed
(Hydrologic Unit Code [HUC] 030501011405).
This report presents a quantitative water quality analysis performed in response to NCDWQ's requirement, and
to determine how estimated induced land use changes resulting from the Project may affect water quality
throughout the 265-square mile Study Area defined for this analysis. The water quality analysis involved
constructing watershed models for the nine 12-digit hydrologic units (HUs) comprising the Study Area. The
watershed models were used to estimate annual runoff and annual overland pollutant loading rates of total
nitrogen (TN), total phosphorus (TP), total suspended sediment (TSS) produced from the three land use
scenarios described in Table 1. Comparison of the runoff and pollutant loading rates projected for the 2035 No
Build Alternative (No Build) and 2035 Preferred Alternative (PA) scenarios provides an indication of the ProjecYs
potential water quality effects.

Gaston East-West Connector Wa ter Quality Analysis
October 2011- Draft
Table 1: Land Use Scenarios Considered in the Quantitative Water Quality Analysis
. . . �.. -. �- .
Baseline Condition Baseline Land use conditions existing in 2006
2035 No Build Alternative
Year 2035 Preferred Alternative
(PA)
2035 No Build
2035 PA
Forecasted land use for the year 2035 without
construction of the Project
Forecasted land use for the year 2035 with
construction of the PA as presented in the FEIS
The watershed model selected for this analysis was the Virginia lnstitute of Marine Science BasinSim 1.0 (VIMS
2000) build of the Generalized Watershed Loading Functions model (Haith and Shoemaker 1987, Haith et al.
1992). GWLF is considered an effective tool for watershed planning efforts where runoff and overland pollutant
loadings are primary concerns (EPA 2008) as it simulates runoff and overland nutrient (TN and TP) and sediment
(TSS) loading by considering variable land uses. In this analysis, land use is isolated as the experimental variable.
As such, the difference between runoff and loadings calculated by GWLF for the 2035 No Build and 2035 PA
scenarios is dictated by the direct effects of the Project and Project induced development (indirect effects)
captured in the 2035 PA scenario.
The water quality analysis scope, study area, and model selection were coordinated with NCDWQ at a meeting
held on October 18, 2010. Minutes from this meeting and follow-up emails regarding the Fites Creek-Catawba
River subwatershed are included in Appendix C. The Fites Creek-Catawba River subwatershed was initially
excluded from the quantitative ICE assessment study area used by Louis Berger Group, Inc. (Berger) due to a lack
of substantial changes in travel times for the majority of this area with the completion of the Gaston East-West
Connector. However, due to the proximity of the southern boundary of the subwatershed to the Preferred
Alternative, it was decided that this subwatershed should be included to capture any potential induced growth
that may occur in this subwatershed. This water quality analysis also includes the Fites Creek-Catawba River
subwatershed.
2.0 STUDY AREA
The Study Area marks the extent of the water quality analysis. The following sections describe the process by
which the Study Area was defined and the condition of the Study Area water resources.
2.1 Study Area Definition
This water quality analysis adopted the Study Area developed for the Gaston East-West Connector Quantitative
Indirect and Cumulative Effects (ICE) Analysis performed by Berger (Berger 2011). The primary factors
considered in the defining the Study Area included the following: the Natural Resources Conservation Service
Watershed Boundary Dataset (NRCS WBD) Subwatershed boundaries (12-digit HUs), potential changes in
accessibility, and potential changes in travel times. By considering these and other factors in combination,
Berger determined the Study Area to be the aggregate extent of the nine 12-digit HUs listed in Table 2.
The Study Area is 265 square miles and contains portions of North Carolina and South Carolina. From west to
east, the Study Area extends from Cleveland County, NC, through Gaston County, NC, into western Mecklenburg
County, NC. From south to north, it extends from the Town of Clover, SC to the Town of Spence Mountain, NC.
The North Carolina portion composes 207 square miles (78 percent) of the Study Area, while South Carolina
portion constitutes 58 square miles (22 percent). Municipalities located in the Study Area include the Cities of

Gaston East-West Connector Wa ter Quality Analysis
October 2011- Draft
Belmont, Bessemer City, Charlotte, Gastionia, Kings Mountain, Lowell, and Mount Holly and Towns of
Cramerton, McAdenville, Ranlo, and Spencer Mountain in North Carolina. The Town of Clover is the only
municipality in South Carolina included the Study Area. The extent of the Study Area as well as municipalities
and roads are depicted in Figure Al, Appendix A.
2.2 Water Resources
The Study Area is located on the border of North and South Carolina within the Catawba-Santee River Basin.
The entirety of the Study Area is located within the Catawba River Basin (0305) and includes portions the
Catawba River Headwaters Subbasin (USGS Hydrologic Unit [HUC] 03050101) and the South Fork Catawba River
Subbasin (USGS HUC 03050102) (NCDWQ 2010b). The Study Area includes the nine 12-digit HUs listed in Table
2. Streams in the North Carolina portion of the Study Area represent 76 percent of the total stream footage;
South Carolina contains 24 percent of the Study Area stream footage.
The Study Area contains 36 named streams (Table 3) from both North and South Carolina. The headwaters of 26
streams occur within the Study Area: Abernathy Creek, Anthony Creek, Beaverdam Creek, Blackwood Creek,
Camp Run, Catawba Creek, Crowders Creek, Duharts Creek, Ferguson Branch, First Creek, Fites Creek, Little Paw
Creek, McGill Creek, Mill Creek, Neal Branch, Oates Creek, Paw Creek, Porter Branch, Rocky Branch, Shoal
Branch, South Crowders Creek, Spring Creek, Squirrel Branch, Stowe Branch, Studman Branch, and Ticer Branch.
Classifications are assigned to waters of the State of North Carolina based on the existing or contemplated best
usage. Thirty of the named streams within the Catawba Study Area are Class C streams. Class C streams are
protected for secondary recreation, fishing, wildlife, fish and aquatic life propagation, and other uses (NCDWQ
2009). The Study Area also includes three WS-IV (Water Supply IV) streams, and three WS-V (Water Supply V)
streams. Water Supply III and IV streams are used as sources of water supply for drinking, culinary, or food
processing purposes and are protected through restrictions on development and waste water discharges. Water
Supply V streams are also used as sources of water supply but have no categorical restrictions on watershed
development or wastewater discharges. Local governments are not required to adopt watershed protection
ordinances for Water Supply V streams but are required to do so for WS-III and WS-IV streams (NCDWQ 2009).
Of the streams with Water Supply classifications, four are also assigned a CA (Critical Area) designation. CA
refers to an area adjacent to the water supply intake where risk associated with pollution is greater than from
the remaining portions of the watershed (NCDWQ 2007a). CAs require additional restrictions on watershed
development beyond those required for a WS classification. Table 3 lists the best usage classifications for all
named streams within the North Carolina portion of the Study Area.
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Gaston East-West Connector Wa ter Quality Analysis
October 2011- Draft
The North Carolina Division of Water Quality (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
Catawba River Basinwide Water Quality Plan (NCDWQ 2010b). Water quality within the Catawba River Basin is
assessed by sampling of fish and benthic macroinvertebrates, and data collected at ambient (chemical and
physical water quality) monitoring stations. The collected data is compared against water quality standards in
order to evaluate the various best uses of North Carolina waters including aquatic life or biological integrity,
recreation or swimming, and water supply. Table 3 lists the use support categories for aquatic life, recreation,
and water supply use for all NCDWQ evaluated waterbodies within the Study Area. Blank cells indicate use
support category was not rated.
Similarly, the South Carolina Department of Health and Environmental Control (SCDHEC) assigns use
classifications to waters of the state. The classifications establish the general rules and specific water quality
criteria applicable to a given waterbody for protecting its classification and existing use. All Study Area streams
in South Carolina carry the Freshwaters (FW) classification. Freshwaters are suitable for primary and secondary
contact recreation; as a source of drinking water supply after conventional treatment; for fishing and the
survival and propagation of aquatic fauna and flora; and for industrial and agricultural uses (SCDHEC 2006a,
2008a).
Table 4 presents the named waterbodies of the Study Area located in South Carolina. Stream classifications are
included, but use support ratings are not.
Table 3: Classifications and Use Support Ratings of Named Study Area Waterbodies in North Carolina
. .
...
... �- . .
11-135-4a AbemethyCreek FromsourcetoFirst C Supporting
Creek
11-135-4b AbemethyCreek FromFirstCreekto C Supporting
Crowders Creek
11-130-2-�1) Anthony Creek From source to Dam at C
(Robinwood Lake) Robinwood Lake
11-130-2-�2) Anthony Creek From Dam at C
Robinwood lake to
Catawba Creek
11-126 Beaverdam Creek From sourceto Lake C
Wylie, Catawba River
11-135-5 Bessemer Branch From source to C
Crowders Creek
11-135-7 Blackwood Creek From sourceto C Supporting Supporting
Crowders Creek
11-130a Catawba Creek From sourceto C Supporting Supporting
SR2446,Gaston
11-130b Catawba Creek From SR2446, Gaston C Supporting Supporting
to SR2439, Gaston
11-130c Catawba Creek From5R2439to Lake C Supporting
Wylie
11-�117) CATAWBA RIVER From Mountain Island WS-IV;CA Supporting Supporting Supporting
(LakeWyliebelow Damtolnterstate
elevation 570) Highway 85 Bridge at
Belmont
11-�122) CATAWBA RIVER From I-85 bridgeto WS-IV,B;CA Supporting Supporting Supporting
(Lake Wylie below the upstream side of
elevation 570) Paw CreekArm of
Lake Wylie, Catawba
River
4

Gaston East-West Connector Wa ter Quality Analysis
October 2011- Draft
. .
...
... �- . .
11-�123.5) CATAWBA RIVER From the upstream WS-V, B Supporting Supporting Supporting
(LakeWyliebelow sideofPawCreekArm
elevation 570) of Lake Wylie to North
North Carolina Carolina-South
portion Carolina5tateLine
11-135a CrowdersCreek Fromsourceto C Supporting
SR1118
11-135b CrowdersCreek From State Route C Supporting
1118 to State Route
1122
11-135c CrowdersCreek From State Route C Supporting
1122 to State Route
1131
11-135d CrowdersCreek From State Route C Supporting
1131 to State Route
1108
11-135e CrowdersCreek From State Route C Supporting Supporting
1108 To NC 321
11-135f CrowdersCreek FromStateRoute321 C Supporting Supporting
to State Route 2424
11-135g CrowdersCreek From State Route C Supporting Supporting
2424 to North
Carolina-South
Carolina State Line
11-129-19 DuhartsCreek Fromsourceto5outh WS-V Supporting Supporting Supporting
Fork Catawba River
11-135-8 Fergumn Branch From sourceto C
Crowders Creek
11-135-4-1 FirstCreek Fromsourceto C
Abemethy Creek
11-121-�1) FitesCreek Fromsourcetoapoint WS-IV Supporting Supporting Supporting
03 mile downstream
of N.C. Hwy. 273
11-121-�2) FitesCreek Fromsourcetoapoint WS-IV;CA
03 mile downstream
of N.C. Hwy. 273 to
Lake Wylie, Catawba
River
11-129-17 HousersBranch Fromsourceto5outh C
Fork Catawba River
11-126-1 Legion Lake and Entire lake and C
ShoafLake mnnectingstreamto
Beaverdam Creek
11-125 Little Paw Creek From source to Lake C
(Danga Lake) Wylie, Catawba River
11-132 LongCove FromsourcetoLake C
Wylie, Catawba River
11-135-9 McGill Branch From sourceto C Supporting Supporting
Crowders Creek
11-135-2 McGill Creek From sourceto C Supporting
Crowders Creek
11-131 Mill Creek From sourceto North C
Carolina-South
Carolina State Line

Gaston East-West Connector Wa ter Quality Analysis
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. .
...
... �- . .
11-128 Neal Branch From sourceto Lake C
(ArmourCreek) Wylie, Catawba River
11-135-6 Oakland Lake Entire lake and C
mnnecting stream to
Crowders Creek
11-135-5-1 OatesCreek Fromsourceto C
Bessemer Branch
11-124 PawCreek FromsourcetoLake C
Wylie, Catawba River
11-133 Porter Branch From source to Lake C
Wylie, Catawba River
11-135-11 Rocky Branch From source to North C
Carolina-South
Carolina State Line
11-130-4 Shoal Branch From sourceto C
Catawba Creek
11-135-10-1 SouthCrowders Fromsourceto5outh C Impaired Supporting
Creek ForkCrowdersCreek
11-129-�15.5) South Fork From a point 0.4 mile WS-V Impaired Supporting Supporting
Catawba River upstream of Long
Creekto Cramerton
Dam and Lake Wylie at
UpperArmstrong
Bridge (mouth of
South Fork Catawba
River)
11-135-10 South Fork North Carolina Portion C Supporting
Crowders Creek
11-135-1 Squirrel Branch From sourceto C
Crowders Creek
11-127 Stowe Branch From sourceto Lake C
Wylie, Catawba River
11-134 Studman Branch From sourceto Lake C
Wylie, Catawba River
11-124-1 Ticer Branch (Tiser From source to Paw C
Branch) Creek
ts: rnmary necreanon, rresn water
C: Aquatic Life, Semndary Recreation, Fres
CA: Critical Area
WS-IV: Water Supply IV - Highly Developed
WS-V: Water 5upply V- U pstream
Table 4: Classifications of Study Area Waterbodies in South Carolina

Gaston East-West Connector Wa ter Quality Analysis
October 2011- Draft
2.2.1 Existing Water Quality
NCDWQ and SCDHEC are required by Clean Water Act Section 303(d) and 40 CFR 130J to maintain a list of
impaired waterbodies. Commonly referred to as the 303(d) list, the list is typically complied every two years,
with the last effective final list dated 2010 for North Carolina and South Carolina. These lists are a
comprehensive accounting of all impaired waterbodies. An impaired waterbody 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.
In both states, inclusion to the 303(d) list is based upon use-support guidelines in Section 305(b) (USEPA-841-B-
97-002A and -002B). Those waterbodies only attaining Partially Supporting or Not Supporting status are
included on the 303(d) list. Tables 5 and 6 list the Study Area waterbodies that are found on the year 2000 to
2010 303(d) lists for North and South Carolina. The waterbodies occur in the Catawba Creek, Duharts Creek —
South Fork Catawba River, Lower Crowders Creek, Mill Creek-Lake Wylie, and Upper Crowder Creek HUs (Figure
A2, Appendix A).
Review of current and past 303(d) lists as well as the NCDWQ Catawba River Basinwide Water Quality Plan and
SCDHEC Catawba River Basin Watershed Water Quality Assessment provide an indication of water quality trends
in the Study Area. Based on inspection of Tables 5 and 6, it is apparent the number of Study Area waterbodies
listed as impaired by North Carolina has increased slightly over the period from 2000 (12 listed waterbodies) to
2010 (14 listed waterbodies) (NCDWQ 2000, 2003, 2006, 2007b, 2010a, 2010c). In contrast, South Carolina has
seen a marked reduction in the number of impaired waterbodies, from six in 2000 to two in 2010 (SCDHEC 2000,
2002, 2004, 2006b, 2008b, 2010). In all cases, the waterbodies delisted by South Carolina between 2008 and
2010 were removed because water quality standards were attained (SCDHEC 2010).
Additionally, Clean Water Act Section 303(d) requires states to develop Total Maximum Daily Loads (TMDLs) for
impaired waterbodies. A TMDL establishes 1) the maximum amount of a pollutant a waterbody can receive and
still comply with water quality standards and 2) pollutant loading limits on known sources. By accounting for
and limiting loadings of a pollutant, steps can then be taken to restore the waterbody to its assigned uses
(USEPA 1991, from Crowders Creek TMDL). The following waterbodies in the Study Area have existing TMDLs:
Crowders Creek, Lake Wylie, Beaverdam Creek, and Brown Creek.
In 2004, NCDWQ in coordination with SCDHEC developed a TMDL for fecal coliform bacteria (FCB) for the last
four miles of Crowders Creek from State Route 1108 to the North Carolina/South Carolina state line
(classification indexes 11-135e-g). This section of Crowders Creek in North Carolina as well as the remainder in
South Carolina has historically experienced elevated FCB concentrations, as indicated by its listing on the North
and South Carolina 303(d) lists for over a decade and the implementation of a previous TMDL in 1996. Sources
of FCB are attributed to discharge from multiple waste water treatment plants, faulty sewage collection system
lines, septic systems, biosolids application, and livestock.
Lake Wylie has a history of nutrient enrichment problems. In 1992, a report authored by the NCDWQ and
SCDHEC concluded the lake's assimilative capacity for nutrients was exhausted. Subsequently, the Lake Wylie
Nutrient Management Plan and accompanying TMDL was implemented in 1996. The nutrient management
7

Gaston East-West Connector Wa ter Quality Analysis
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strategy established by the TMDL targeted non-point source reductions and placed stringent nutrient removal
requirements on point source dischargers to the most highly eutrophic arms of the lake (NCDWQ 2010b). The
latest water quality data reported in the 2010 Catawba River Basinwide Water Quality Plan (NC DWQ 2010b)
indicates nutrient enrichment remains a problem in the lake. Samples of the main stem of Lake Wylie produced
no chlorophyll a standard exceedances, yet all samples demonstrated elevated chlorophyll a. Further, sampling
from the Crowders Creek and South Fork Catawba arms of the lake suggested localized areas of eutrophication.
In addition to nutrient enrichment, portions of Lake Wylie have more recently been cited as impaired for aquatic
life support due to water quality standard exceedances of low pH, copper, chlorophyll a, and high water
temperature.
SCDHEC developed FCB TMDLs for two streams in the Study Area - Beaverdam Creek and Brown Creek - in
2001. For Beaverdam Creek, runoff from livestock pastures and built-up land were noted as the primary and
secondary FCB sources (SCDHEC 2001a). In the case of Brown Creek, urban runoff as well as failing septic
systems and direct sewage discharges were described as the principal sources of FCB (SCDHEC 2001b).
Table 5: Study Area Waterbodies on the North Carolina 2000- 2010 303(d) Lists
• ��� �� ��� ��. ��: � �
.-
... �- . . .
11-135-4b AbemethyCreek From FirstCreekto Impaired biological integrity No No No Yes Yes No
Crowders Creek
11-130a CatawbaCreek Frommurceto5R2446, Unknown�2000-02),impaired Yes Yes Yes Yes Yes Yes
Gaston biologicalintegrity�2004-10)
11-130b CatawbaCreek From5R2446,Gastonto Unknown�2000-02),impaired Yes Yes Yes Yes Yes Yes
SR2439, Gaston biological integrity (2004-10)
11-130c CatawbaCreek From5R2439toLake Unknown�2000-02),impaired Yes Yes Yes Yes Yes Yes
Wylie biologicalintegrity�2004-10)
11-�117) Catawba River (Lake From I-85 bridge to the Low pH No No No No Yes Yes
Wylie below elevation upstream side of Paw
570) CreekArm of Lake Wylie,
Catawba River
11-�123.5)b Catawba River (Lake South Fork Catawba Copper, chlorophyll a(2008), No No No No Yes Yes
Wylie South Fork River Arm of Lake Wylie turbidity (2008), high water
Catawba arm) North temperature (2010)
Carolina portion
11-135a CrowdersCreek Frommurceto5R1118 Unknown�2000-02),impaired Yes Yes Yes Yes Yes Yes
biologicalintegrity (2004-10)
11-135b Crowders Creek From State Route 1118 Unknown (2000-02), impaired Yes Yes Yes No Yes No
to State Route 1122 biological integrity (2004,2008)
11-135c Crowders Creek From State Route 1122 Unknown (2000-02), impaired Yes Yes Yes Yes Yes Yes
to State Route 1131 biological integrity (2004-10)
11-135d Crowders Creek From State Route 1131 Unknown (2000-02), impaired Yes Yes Yes Yes Yes Yes
to State Route 1108 biological integrity (2004-10)
11-135e Crowders Creek From State Route 1108 Fecal Coliform, impaired biological Yes Yes Yes Yes Yes Yes
To NC 321 integrity (2004-06, 2010)
11-135f Crowders Creek From State Route 321to Fecal Coliform, impaired biological Yes Yes Yes Yes Yes Yes
State Route 2424 integrity (2004-06, 2010)
11-135g Crowders Creek From State Route 2424 Fecal Coliform (2000-06, impaired Yes Yes Yes Yes Yes No
toNC/SCLine biologicalintegrity�2006-08)
11-135-2 McGiIlCreek Frommurceto Unknown�2000-02),impaired Yes Yes Yes Yes Yes Yes
Crowders Creek biological integrity (2004-10)
11-135-10-1 South Crowders Creek From murce to South Low Dissolved Oxygen No No No No No Yes
Fork Crowders Creek
11-129-�15.5) South ForkCatawba From a point0.4 mile Turbidity, low pH (2010) No No No No Yes Yes
River upstream of Long Creek
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*Note: 2 of the 9 waterbodies listed in Table 6 are classified as impaired in 2010.
2.2.2 Existing Water Quality Measures
As part of the preparation for the modeling effort, and in order to determine whether existing regulations and
ordinances are sufficient to protect water quality, Atkins inventoried the variety of protective measures for
riparian buffer widths and stormwater requirements of the different planning jurisdictions within the Study
Area. Government organizations that were considered include the North Carolina municipalities of Belmont,
Bessemer City, Charlotte, Cramerton, Gastionia, Kings Mountain, Lowell, McAdenville, Mount Holly, Ranlo, and
Spencer Mountain. In South Carolina and the Town of Clover was considered .
Additionally, EPA Phase I or Phase II Stormwater Rules are in effect in nearly the entire Study Area (99 percent).
NCDWQ identifies the City of Charlotte as a Phase I stormwater permittee by the EPA as of 1993. As required
by National Pollutant Discharge Elimination System (NPDES) regulations, Charlotte must develop and implement
a storm water program including public education, illicit discharge detection and elimination, storm sewer
system and land use mapping, and analytical monitoring. Gaston County, NC and York County, SC are both
Phase II stormwater permittees. NPDES regulations require them to, at a minimum, develop, implement, and
enforce a storm water program designed to reduce the discharge of pollutants from the municipal separate
storm sewer system (MS4). Stormwater best management practices (BMPs) drafted by Gaston and
Mecklenburg Counties are provided in Table 7.
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Table 7: StudY Area Stormwater BMPs
• Establishes minimum post-construction storm water management standards and design criteria for the regulation
and control of storm water runoff quantity and quality
Mecklenburg County' • Establishes design and review criteria for the construction, function, and use of structural storm water best
management practices (BMPs)
• Provides pollutant removal efficiency requirements of BMPs for TSS and TP
• Establishes stormwater management regulations to control the adverse effects of stormwater runoff associated
with new development
Gaston County (except the Mount Holly,
Kings Mountain, and properties with • Establishes design and review criteria for promoting sound development practices that meet the minimum
water supply watersheds)Z stormwater management standards
• All structural storm water treatment systems used to meet these requirements shall be designed to have a
minimum of 85%average annual removal for TSS
'Stormwater Post Construction Controls Ordinance Administrative Manual (Charlotte MecklenburgJuly 2009)
�Gaston County Stormwater Ordinance (Gaston County, NC July 2007)
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3.0 WATER QUALITY ANALYSIS APPROACH
This section outlines the methodology used to quantify the ProjecYs potential water quality effects. The
BasinSim GWLF watershed model employed in the analysis is discussed in detail. The procedures used to derive
model input parameters, special model considerations, and model calibration are also presented.
3.1 BasinSim Description
BasinSim is a desktop simulation system that predicts sediment and nutrient loads for small to mid-sized
watersheds. The simulation system is based on the Generalized Watershed Loading Functions (GWLF), a tested
watershed model developed by Dr. Douglas Haith and his colleagues at Cornell University, New York (Haith and
Shoemaker 1987, Haith et al. 1992). BasinSim 1.0 integrates an easy-to-use graphic Windows interface,
extensive databases (land uses, population, soils, water discharge, water quality, climate, point nutrient sources,
etc.), and the GWLF model (with modifications) into a single software package. It was designed to enable
resource managers to visualize watershed characteristics, retrieve historic data (at the county and sub-
watershed levels), manipulate land use patterns, and simulate nutrient (N, P, and organic C) and sediment
loadings under various scenarios. The latest version of BasinSim, version 1.0.0, was released in April 1999.
The GWLF model, developed by Haith and Shoemaker (1987), is currently used in different platforms under
different names (Dai et al. 2000; Schneiderman et al. 2002; Evans et al. 2002; Hong and Swaney 2004; Morth et
al. 2007). Each version has particular modifications but all follow the same conceptual framework. GWLF
simulates runoff, sediment delivery, and average nutrient concentration based on land use. Figure 1 depicts the
major components of GWLF. The model uses daily steps for weather data and water balance calculation.
Evapotranspiration is determined using daily weather data and a cover factor dependent upon land use/land
cover type. Sediment and nutrient loads are estimated monthly, based on the daily water balance accumulated
to monthly values.
GWLF has been described as an "engineering compromise between the empiricism of export coefficients and
the complexity of chemical simulation models" (Haith and Shoemaker, 1987). GWLF is considered a combined
distributed/lumped parameter watershed model. For surface loading, it is distributed in the sense that it allows
multiple land use/land cover scenarios, but each area is assumed to be homogenous with regard to various
attributes considered by the model. The model does not spatially distribute the source areas, but simply
aggregates the loads from each area into a watershed total; in other words there is no spatial routing.
Groundwater runoff and discharge are obtained from a lumped-parameter watershed water balance for both
shallow saturated and unsaturated zones.
Runoff is calculated by means of the U.S. Soil Conservation Service's (SCS) curve number equation (SCS 1986).
The Universal Soil Loss Equation (USLE) is applied to simulate erosion. Rural nutrients are estimated using
empirical concentrations of each land use, which are based on both dissolved concentration in runoff and solid
concentration in sediment. Urban nutrient loads are computed by exponential accumulation and washoff
functions. Nutrient loads from septic systems are calculated by estimating the per capita daily load from each
type of septic system and the number of people in the watershed served by each type. Sub-surface losses are
calculated using dissolved N and P coefficients for shallow groundwater contributions to stream nutrient loads,
and the sub-surface sub-model only considers a single, lumped-parameter contributing area, as mentioned
previously. GWLF does not include instream flow and transport of loads. However, GWLF provides for ground
water discharges to stream systems, offering an opportunity for calibrating instream flow volume.
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Gaston East-West Connector Wa ter Quality Analysis
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Figure 1: GWLF surface and sub-surface hydrology and loading pathways (adapted from Haith et al. 1992).
BasinSim's implementation of GWLF has incorporated a variable seepage control into the model, replacing a
constant seepage coefficient, to help with calibration of streamflow. GWLF in BasinSim also supplies a time-
delay feature which postpones the effect of weather events on stream responses, a population growth function
which permits the nutrient contribution by septic systems to change over time, and the ability to assign variable
nutrient concentrations as a function of streamflow.
3.2 Input Parameters
Spatial (GIS data layers) and non-spatial data were used to derive input parameters for the GWLF watershed
model. Data sources are listed in Table 8 and their use is described in the following sections. Table 8 also lists
the units, significant figures, and decimal places used for the model inputs. Significant figures are not relevant
to some of the data listed, such as the aerial photography, and sewer service extent data. With the exception of
the Study Area land use, the significant figures and decimal places listed are determined by the data provider.
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Gaston East-West Connector Wa ter Quality Analysis
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Table 8: Model Inputs and Data Sources
�. .
�-
Study Area land use The Louis Berger Group, Inc Area: Acres Area: Generally 3 figures Area: 0
2009NationalAgriculturelmagery USDepartmentofAgriculture NotApplicable NotApplicable NotApplicable
Program aerialphotography
National Hydrography Datasetstream
flowlines U5G5 NotApplicable NotApplicable NotApplicable
NationalOceanicandAtmospheric Temperature:°Fahrenheit Temperature:2 Temperature:0
Weatherstationlocationsanddata qdministrationandU5G5 Precipitation:inches Precipitation:3 Precipitation:2
Cleveland, Gaston, and Mecklenburg North Carolina Floodplain Mapping
Co., NC digital elevation model Program Elevation: feet Elevation: 5 Elevation: 2
York Co., SC digital elevation model U5G5 Elevation: meters Elevation: 5 Elevation: 2
Sewerserviceareas TheLouisBergerGroup,lnc NotApplicable NotApplicable NotApplicable
Streamflowdata U5G5 Streamflow:feet'/semnd Streamflow:lto3 Streamflow:Oto2
SoilSurveyGeographic�55URG0) NaturalRemurceConservation AvailableWaterStorage:centimeters AvailableWaterStorage:4 AvailableWaterStorage:2
Database Service Soil Erodibility Factoc unitless Soil Erodibility Factoc 2 Soil Erodibility Factoc 2
Pointmurce dischargers location and Total nitrogen: milligrams/Liter Total nitrogen:2 Total nitrogen:0 to 1
NCDWQ
discharges in NC Total phosphorus milligrams/Liter Total phosphorus 2 Total phosphorus 0 to 1
Point murce dischargers location and
discharges in SC SCDHEC Total phosphorus milligrams/Liter Total phosphorus 2 Total phosphorus 0 to 1
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3.2.1 Land Use
Study Area land use for the Baseline Condition, 2035 No Build, and 2035 PA scenarios was provided by Berger
and described in the Gaston East-West Connector Quantitative Indirect and Cumulative Effects Analysis (Berger
2011). The land use datasets were developed as part of the Gaston East-West Connector quantitative ICE
analysis.
A spatially-explicit Baseline Condition land use dataset was produced for the year 2006 condition of the Study
Area by using high resolution aerial photography to update the 2001 National Land Cover Database (NLCD)
(USGS 2003). The NLCD is a spatially-explicit, gridded dataset with a 30-meter resolution. That is, each 30
meter-by-30 meter grid cell in the dataset is assigned a land cover category. The update process focused on
identifying large areas of land, such as subdivisions and shopping centers, that converted from forest to
developed land cover in the interim time period. The land cover categories of the NLCD grid cells were modified
to reflect areas of land use conversion. Fifteen NLCD 2001 land cover categories occur in the Study Area (see
Table 9).
Land use forecasts for the 2035 No Build and 2035 PA scenarios, in contrast, were developed as non-spatially
explicit datasets. In other words, the individual 30 meter-by-30 meter grid cells of the spatially-explicit Baseline
Condition land use dataset were not changed to reflect a land use conversion in the future scenarios. Instead,
the land use forecasts were performed at the scale of Traffic Analysis Zones (TAZs). The Study Area was found
to encompass 275 TAZs. The TAZ boundaries, however, did not necessarily conform to the HU boundaries of the
Study Area. To summarize the TAZ land use forecasts by HU, the 275 TAZs were intersected with the nine Study
Area HUs. The result was 387 forecasting zones, with each zone corresponding to exactly one TAZ and one HU.
The forecasting zones provided the geographic framework for the 2035 No Build and 2035 PA land use forecasts
and are the smallest unit for which land use change results are reported.
Figures depicting the forecasting zones and results of the quantitative ICE analysis are provided in Appendix B.
Further explanation of the land use forecast can be found in the Gaston East-West Connector Quantitative
Indirect and Cumulative Effects Analysis (Berger 2011).
Table 9: NCLD Land Cover Categories for the Study Area
� •. �- . .
All areas of open water, generally with less than 25% cover of
Open Water vegetation or soil.
Includes areas with a mixture of some constructed materials, but
mostly vegetation in the form of lawn grasses. Impervious surfaces
Developed, Open Space account for less than 20% of total cover. These areas most
commonly include large-lot single-family housing units, parks, golf
courses, and vegetation planted in developed settings for
recreation, erosion control, or aesthetic purposes.
Includes areas with a mixture of constructed materials and
vegetation. Impervious surfaces account for 20-49%oftotal cover.
Developed, Low Intensity These areas most commonly include single-family housing units.
Includes areas with a mixture of constructed materials and
vegetation. Impervious surfaces account for 50-79%ofthe total
Developed, Medium Intensity �over. These areas most commonly include single-family housing
units.
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Gaston East-West Connector Wa ter Quality Analysis
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� •. �- . .
Includes highly developed areas where people reside or work in
high numbers. Examples include apartment complexes, row houses,
Developed, High Intensity and commercial/industrial. Impervious surfaces account for 80-
100% ofthetotalcover.
Barren areas of bedrock, desert pavement, scarps, talus, slides,
Barren Land (Rock/Sand/Clay) volcanic material, glacial debris, sand dunes, strip mines, gravel pits
and other accumulations of earthen material. Generally, vegetation
accountsforlessthan 15% oftotalcover.
Areas dominated by trees generally greater than 5 meters tall, and
greaterthan 20%oftotal vegetation cover. Morethan 75%ofthe
Deciduous Forest tree species shed foliage simultaneously in response to seasonal
change.
Areas dominated by trees generally greater than 5 meters tall, and
greaterthan 20%oftotal vegetation cover. Morethan 75%ofthe
Evergreen Forest tree species maintain their leaves all year. Canopy is never without
green foliage.
Areas dominated by trees generally greater than 5 meters tall, and
greater than 20%of total vegetation cover. Neither deciduous nor
Mixed Forest evergreen species are greater than 75% of total tree cover.
Areas dominated by shrubs; less than 5 meters tall with shrub
canopy typically greater than 20%oftotal vegetation. This class
Shrub/Scrub includes true shrubs, young trees in an early successional stage or
trees stunted from environmental conditions.
Areas dominated by grammanoid or herbaceous vegetation,
generally greater than 80% of total vegetation. These areas are not
Grassland/Herbaceous subject to intensive management such as tilling, but can be utilized
for grazi ng.
Areas of grasses, legumes, or grass-legume mixtures planted for
livestock grazing or the production of seed or hay crops, typically on
Pasture/Hay a perennial cycle. Pasture/hay vegetation accounts for greater than
20% of total vegetation.
Areas used for the production of annual crops, such as corn,
soybeans, vegetables, tobacco, and cotton, and also perennial
Cultivated Crops woody crops such as orchards and vineyards. Crop vegetation
accounts for greater than 20%oftotal vegetation. This class also
includes all land being actively tilled.
Areas where forest or shrubland vegetation accounts for greater
than 20% of vegetative cover and the soil or substrate is
Woody Wetlands periodically saturated with or covered with water.
Areas where perennial herbaceous vegetation accounts for greater
than 80% of vegetative cover and the soil or substrate is
Emergent Herbaceous Wetlands periodically saturated with or covered with water.
3.2.2 Soils
Spatial and tabular Soil Survey Geographic (SSURGO) soil information was downloaded from NRCS (NRCS 2010)
for Cleveland, Gaston, and Mecklenburg Counties, NC as well as York County, SC. The soils were clipped to the
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Gaston East-West Connector Wa ter Quality Analysis
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Study Area boundary. Soil series, or map units, which occurred in the Study Area, were assigned available
water-holding capacity, soil erodibility (K) factor, dominant hydrologic soil group, and organic matter content as
required by GWLF. Available water-holding capacity was assigned by using the Available Water Storage 0-100
cm - Weighted Average value provided for each map unit in the Mapunit Aggregated Attribute table. Soil
erodibility (K) factor was assigned using the Kf value provided for the top horizon in the Horizon table for each
map unit. Dominant hydrologic soil group was assigned by using the Hydrologic Group - Dominant Conditions
value provided for each map unit in the Mapunit Aggregated Attribute table. Organic matter content is not
currently used by the model and was not assigned a value.
3.2.3 Curve Numbers
GWLF computes runoff from each land use class using the SCS Curve Number Equation (Ogrosky and Mockus,
1964, SCS 1986). Curve Numbers (CNs), an essential component to this method, were assigned to each land use
class by relating the individual classes to a cover type and hydrologic condition category described in Soil
Conservation Service Technical Release 55 (SCS 1986). CNs assignments are presented in Table 10. The GWLF
model used in this analysis only accepts one CN per land use class. As such, a single, area-weighted average CN
was calculated for each land use class of each HU based on the area of the land use class overlying the four
hydrologic soil groups. The resultant average CN value was provided to GWLF.
3.2.4 Streams
The stream layer was derived from the National Hydrography Dataset (NHD) (USGS 2010) by extracting the high
resolution NHD flow lines from the prestaged Edisto-Santee subregion. The merged streams were then clipped
to the Study Area boundary. The clipped streams were used in delineating the extent of existing riparian
buffers.
3.2.5 Weather Stations
The location of weather stations with daily temperature (maximum and minimum) and precipitation records for
the period 1999-2010 were retrieved from State Climate Office of North Carolina (SCO) (SCO 2011). Weather
data from the Gastonia Municipal Airport (KAKH) in Gaston County was formatted for use by BasinSim.
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3.2.6 Point Sources
Location of point source dischargers within the Study Area were identified by retrieving NPDES permits from
NCDWQ (NCDWQ 2011a) and SCDHEC (Larry Turner, SCDHEC, personal communication, 6/20/2011). Monthly
discharge reports for all dischargers were retrieved from NCDWQ for 2009 (NCDWQ 2011b). Additionally,
monthly discharge permits for dischargers in the calibration watersheds were retrieved for the calibration and
validation periods, 1999-2003 (Jaeha Ho, SCDHEC, personal communication, 10/7/2010).
3.2.7 Surface Elevation
A 20-foot resolution Digital Elevation Model (DEM) was constructed for the Study Area. Elevation data for the
North Carolina portion of the Study Area were obtained from N.C. Floodplain Mapping Program (NCFMP)
(NCFMP 2007). Elevation data for the portion of the Study Area extending to South Carolina was obtained from
the U.S. Geologic Survey National Elevation Dataset (USGS 2009).
3.2.8 Erosion and Sediment Yield
GWLF computes erosion using the Universal Soil Loss Equation (USLE), and the sediment yield is the product of
erosion and sediment delivery ratio. Models derived from USLE are some of the most widely applied tools for
predicting sediment yield from catchments. USLE factors K, LS, C and P must be specified as the product K* LS *
C* P for each rural runoff source area. Erosion from urban land is not explicitly handled by GWLF. For sediment
loading from urban land uses, some applications of GWLF (e.g., Schneiderman et. al, 2002) use the accumulation
and washoff functions given for nutrients in the original model (Haith et al., 1992), substituting sediment
accumulation rates given in Haith et al. (1992) for particulate nutrient accumulation rates. In this application of
GWLF, USLE was used to compute erosion from urban areas as well.
Residential and rural residential land uses are not addressed directly by USLE though a number of studies have
successfully applied USLE to catchments containing an urban component (Ricker et. al, 2008, Jackson et. al,
2005, Fu et. al, 2005, and Boyle et. al, 2011). Estimates of the percent tree cover, bare soil, grass, and relative
herbaceous cover based on Study Area observations and land use descriptions were used to estimate the
appropriate C factors for urban land covers in this study (Table 11) in a manner similar to the method used to
calculate C factors for rural land uses. USLE K, LS, and P factors for urban land use were estimated in the same
manner as for rural land uses (Appendix B).
Table 11: USLE Cover factors
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3.2.9 Septic Areas
GIS layers describing the extent of current and future sewer systems for the Study Area were supplied by Berger
(Tidd, Louis Berger Group, Inc., personal communication, 10/15/2010). Current septic service was assumed to
occupy the portion of the Study Area not served by the current sewer system and likewise for the future septic
service. The future septic service area was further reduced by the land area converted to Developed, High
Intensity land use in the future land use scenarios. Developed, High Intensity land use is described in Table 9 as
apartment complexes, row houses, and commercial/industrial areas with 80- to 100-percent impervious cover.
Lots built-upon to this extent typically do not have adequate remaining area to support septic fields.
The population served by current and future septic systems was derived from population data supplied by
Berger (Tidd, Louis Berger Group, Inc., personal communication, 1/10/2011). The septic population estimates
assumed that the Project will not make southern Gaston County more attractive to the types of facilities
counted as group quarters (i.e., college dorms, prisons, nursing homes etc.) and that the future group quarters
population is the same in the No Build and Build scenarios. The group quarters facilities are assumed to be
distributed proportional to land area for TAZs only partially contained within the Study Area. Population in
households was assumed to take into account the trend of decreasing household sizes over time in the
forecasts. Therefore, the future population in the Study Area is based on the relationship between future
population in households and future households in Metrolina Travel Demand Model estimates.
3.2.10 Best Management Practice (BMP) [mplementation
The BasinSim GWLF build does not account for pollutant load reductions provided by BMPs.
For this study, pollutant load reductions attributable to riparian buffers (buffers) BMPs were instead accounted
for in a post-processing effort in which GWLF-calculated TN, TP, and TSS loads for a given HU were reduced
according to the existing buffer characteristics of the HU. The implementation of the buffer post-processing
calculations is described below.
Existing buffers were delineated and characterized in portions of the Study Area with legally-protected buffers,
such as the main stem of the Catawba River. The process was initiated by identifying buffer regulations in the
various planning jurisdictions of the Study Area. Table 12 summarizes the Study Area buffer regulations. Using
GIS, the stream network represented by the NHD flowlines was buffered based on the buffer requirements
applicable to the stream location. The resulting buffer layer establishes the extent of regulated buffers in the
Study Area. However, the buffer layer does not necessarily reflect the existing extent of intact buffers. To
delineate the existing extent of intact buffers, the buffer layer was overlaid on 2009 National Agriculture
Imagery Program (NAIP) aerial photography (USDA 2009a, 2009b, 2009c). Areas of disturbed buffer were
removed from the buffer layer, leaving only intact buffers within regulated buffer areas. The final buffer layer
represents the Baseline Condition buffer extent.
It should be emphasized that only buffers in areas with legal protection were delineated. Further, the buffers
were only delineated to their legally-protected width. For example, a riparian buffers along the Catawba River
would only be delineated to 50 feet, even if the vegetated area extends beyond 50 feet. This judgment was
made because the vegetated area beyond 50 feet is not protected and consequently not guaranteed to persist
in the 2035 No Build and 2035 PA scenarios.
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Gaston East-West Connector Wa ter Quality Analysis
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Table 12: StudyArea Regulated Buffer Widths.
, • Main Catawba River stem and the 7 main stem ,
Catawba River' lakes below Lake James south to the NC/SC 50
border
WS-III, 1 dwelling units (DU)/ac or 12% built
Gaston County, NCZ upon area (low density), 0.5 mile critical area, 30
perennial stream
Gaston County, NCZ WS-III, 1 du/0.5 ac or 24% built upon area (low 30
density), Rest of watershed, perennial stream
Gaston County, NCZ WS-IV, 1 du/0.5 ac or 24% built upon area (low 30
density), 0.5 mile critical area, perennial stream
WS-IV, (1 du/0.5 ac or 24% built upon area with
Gaston County, NCZ �urb and gutter) or (1 du/033 ac or 36% built 30
upon area with no curb and gutter), Protected
Area, perennial stream
Gaston County, NCZ WS-III, 12-30% built upon area, 0.5 mile critical 100
area, perennial stream
Gaston County, NCZ WS-III, 24-50% built upon area, Rest of 100
watershed, perennial stream
Gaston County, NCZ WS-IV, 24-50% built upon area, 0.5 mile critical 100
area, perennial stream
Gaston County, NCZ WS-IV, 24-70% built upon area, 0.5 mile critical 100
area, perennial stream
Mecklenburg County, NC3 Drainage area >= 100 acres 35
Mecklenburg County, NC3 Drainage area >= 300 acres 50
MecklenburgCounty,NC3 Drainagearea>=640acres 100+50%floodplainfringe
York County, SC° Lake Wylie 50
York County, SC° Catawba River 100
Perennial streams draining directly to the
a Catawba River or Lake Wylie. Perennial streams
York County, SC 50
are defined as solid blue lines on USGS
topographic maps.
�Catawba River Basin Buffer Rules (15a ncac 026 .0243)
�Gaston County, NC (2011)
3Mecklenburg County, NC (1999)
°York County, SC (2009)
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The buffered stream fraction and average buffer width was determined for each Study Area HU using the
Baseline Condition buffer extent described above. The buffered stream fraction was calculated as follows:
Bu f f ered Stream Length in HU
Bu f f ered Stre am Fraction =
Total Stream Length in HU
The NHD flowlines were used to determine the total HU stream length value in the above equation.
The average buffer width in each HU was calculated as a weighted average based on the length of the buffered
stream segments. Again, only buffers in areas with legal protection were considered. Average buffer widths
calculated for the HUs ranged from 0 feet to 76 feet.
The buffered stream fraction and average buffer width determined for each HU are presented in Table 13. The
average buffer width for Beaverdam Creek-Catawba River is reported as 0 feet because no buffer protection
ordinances are in effect in this HU.
The NCDWQ Stormwater Best Management Practices Manual (2007c) provides pollutant reduction efficiencies
for 50-foot riparian buffers (Table 14). The reduction efficiencies were applied in the post-processing of the
GWLF-calculated TN, TP, and TSS loads to account for pollutant reduction by buffers as follows:
Reduced Pollutant Loading = GWLF Loading x Buf fered Stream Fraction x Reduction Ef ficienry
Pollutant reduction by buffers was only considered for HUs with an average buffer width of 50 feet or greater.
Upper Crowders Creek and Beaverdam Creek-Catawba River HUs do not meet this criterion. As such, the GWLF-
calculated loads for these HUs were not modified.
Table 14: GWLF Buffer Reduction Efficiencies.
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Gaston East-West Connector Wa ter Quality Analysis
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Riparian buffers were the only BMP considered in this analysis. Implementation of other BMPs - bioretention
basins, stormwater ponds, grass swales, etc. - requires site-specific information unavailable at this time. Atkins
believes that, without site-specific information, simulating such BMPs for developed areas in the future land use
scenarios amounts to applying a blanket pollutant loading reduction to all runoff from these areas. Substantial
pollutant load reductions beyond those provided by the simulated riparian buffers could be realized if the EPA
Phase I and II Stormwater Rules, in effect through 99 percent of the Study Area, and locally-mandated
stormwater treatment requirements are enforced.
3.3 Model Calibration
A modeling analysis of any type may include a calibration procedure in which model parameters are adjusted to
achieve a best-fit model, or a model that best accords with observed data. This process occurs in two steps:
calibration and validation. Before either is performed, the observed data record is split into corresponding
calibration and validation periods. The observed record for model calibration consisted of daily streamflow
(USGS 2010) at USGS gage 02145642 Crowders Creek (RD 1104) near Clover, SC in the Lower Crowders Creek
watershed (HU 030501011504) for the period 10/1/1999 through 9/30/2003. Missing observations (July 11,
2000 and 17 dates in August 2000) were replaced with streamflow for same day in 2001.
Since the headwaters of Crowders Creek are also contained within the Study Area (Upper Crowders Creek HU),
Upper and Lower Crowders Creek were modeled and their output combined to compare to the observed
streamflow from the USGS gage. GWLF reports streamflow in depth (centimeters) over the modeled area. As
such, total catchment streamflow was calculated as the area-weighted average of the two watersheds. This
approach uses area to scale the contribution of each watershed to the total streamflow. Pollutant loadings were
not calibrated due to the lack of adequate monitoring data.
The goal of the calibration effort for this analysis was to produce the best fit between modeled monthly
streamflow and observed monthly streamflow for the validation period. The observed period of record was
divided evenly to establish the calibration (10/1/1999 through 9/30/2001) and validation periods (10/1/2001
through 9/30/2003). During calibration, model parameters are adjusted within reasonable ranges until the
model results best fit the observed data of the calibration period. The performance of the calibrated model is
then tested in the validation step by executing the model for the validation period and comparing the results to
observed data (EPA 2008). In watershed modeling studies, the scope of the calibration effort depends in part on
the nature of the analysis and the availability of observed data. Comparative analysis such as one the described
in this report often do not require a rigorous calibration effort as model error is expected to affect the study
scenarios equally.
Calibration involved adjusting the GWLF parameters of the Upper and Lower Crowders Creek watershed models
to achieve better agreement between the model monthly streamflow and observed streamflow.
Evapotranspiration and seepage coefficient parameters were adjusted during calibration. Dai et al. (2000)
recommended calibrating streamflow by adjusting the seepage parameters. Seepage flow in GWLF represents
the water lost to the deep saturated zone (aquifer), and it may remain in the aquifer or exit the aquifer in areas
other than the watershed being studied. The final parameter values are listed in Appendix B.
The Nash-Sutcliffe statistic (Nash and Sutcliffe 1970), a goodness-of-fit statistic recommended by the American
Society of Civil Engineers (1993) for hydrologic studies, was used to evaluate the fit of the modeled streamflow
to observed stream. The Nash-Sutcliffe statistic (N-S value) can range from -� to 1. The statistic measures the
models predictive performance relative to the mean of the observed data. A value of 1 indicates a perfect fit,
while a value of 0 indicates the model is predicting no better than mean of the observed data.
21

Gaston East-West Connector Wa ter Quality Analysis
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Modeled streamflows produced for Upper and Lower Crowders Creek watersheds correlated poorly with the
observed monthly streamflow (N-S value = 0.26) for the calibration period. Low flows during the period made
the calibration difficult. The root mean square error (RMSE) between the modeled and observed monthly
streamflows for the calibration watershed was 0.9 cm; however, modeled streamflow did not provide a
satisfactory fit for the calibration period (Moriasi et al. 2007). RMSE-observations standard deviation ratio (RSR
= 0.84) (Moriasi et al. 2007) was relatively small indicating that, while the RMSE was small, low flow rates were
the major reason and RSR was within acceptable limits. Percent bias (PBIAS = 37) measures the average
tendency of the simulated data to be smaller than their observed counterparts and indicates that the
underestimation provides an unsatisfactory fit. Modeled streamflow generally replicated the observed
streamflow response peaks and valleys (Figure 2).
Modeled streamflows for the validation period correlated well with the observed monthly streamflow (N-S value
= 0.89). The RMSE between the modeled and observed monthly streamflows for the calibration watershed was
1.4 cm. RSR was acceptably small (0.33). PBIAS (0.18) indicates minimal underestimation. Modeled streamflow
provided a satisfactory fit for the validation period (Moriasi et al. 2007).
Modeled monthly flows are plotted against the observed monthly streamflows of the calibration and validation
periods in Figure 2; monthly precipitation is plotted along the top axis. In general, the peaks of the modeled
streamflow align with the observed streamflow in terms of magnitude and duration; although, the amplitudes of
the modeled peaks are often larger than those of the observed streamflow in the later portion of the calibration
period. The monthly streamflow values estimated by the final calibration and validation models are plotted in
Figure 2.
Ultimately, it was concluded the watershed models constructed for the Upper and Lower Crowders Creek
watersheds performed adequately well in calibration and validation procedures. The ET and seepage coefficient
parameter values used in the best-fit models were incorporated in the watershed models constructed for the
nine 12-digit HUs composing the Study Area.
22

Gaston East-West Connector Wa ter Quality Analysis
October 2011- Draft
Calibration Period 10/1/1999 through 9/31/2001
Observed Monthly StreamFlow vs. Modeled StreamFlow
� 15
0 10
E
a 5
. � f+.�.
�+ .Y_"_. ��: ��.-r+
0 _ '-' _ ' _�--rr _ ' _ ' _ ' _ r. _ _
E
3
a
m
:
�
15
10
5
0
Precipitation �Observed Streamflow Modeled Flow
ValidationPeriod 10/1/2001through9/31/2003
Observed Monthly StreamFlow vs. Modeled StreamFlow
Precipitation �Observed Streamflow Modeled Flow
0
v
'm
10 0
w
20 �
3
30 �
0
v
'm
10 0
w
20 �
3
30
Figure 2: Calibration and Validation Model Monthly Streamflows Plotted with Observed Monthly Streamflow.
4.0 RESULTS AND DISCUSSION
GWLF was run for three land use scenarios: Baseline Condition, 2035 No Build, and 2035 PA. Between scenarios,
land use was modified to reflect forecasted land use conversions. Other input parameters (Appendix B)
remained constant for all modeled scenarios. Simulations were run for two years using weather data for the
period 2008 to 2010.
Runoff and loading rates of TN, TP, and TSS (referred to cumulatively as "pollutants") vary as land use patterns
change within the Study Area. In both future scenarios, increased coverage by impervious surfaces resulted in
increases in runoff. These results are expected as increased urbanization occurs. Higher pollutant loads are
anticipated as currently undeveloped, unmanaged land use categories (namely forest lands) are converted to
residential, commercial, and industrial categories and as residential communities are established in septic
service areas . Nutrient export loads from forest lands are significantly less than export loads from commercial
and industrial parcels. The change from undeveloped but managed land use categories (agricultural land and
pasture) to developed land use categories can result in decreased pollutant loads but increases in runoff.
In reviewing the GWLF model output, patterns emerged between the calculated runoff and nutrient loading
rates and the average HU CN, nitrogen buildup rate for urban areas, and phosphorus buildup rate for urban
areas. The CN and nitrogen and phosphorus buildup rates for urban areas are parameters considered by GWLF
in calculating runoff, TN loading, and TP loading, respectively. In general, runoff increases as CN increases; TN
loading increases as the nitrogen buildup rate increases; and TP increases as the phosphorus buildup rate
increases. These observations are a gross simplification of the relationship between land use and runoff and
pollutant loads, yet the pattern generally bears out in the model results reported in Tables 17-19. Table 15
23

Gaston East-West Connector Wa ter Quality Analysis
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presents the CN, nitrogen build rates, and phosphorus buildup rates for the Baseline, 2035 No Build, and 2035
PA scenarios. The values are helpful in explaining differences between the 2035 No Build and 2035 PA scenarios
and will be referred to throughout this section.
A similar trend was not found for the TSS loading rate. The TSS loading rate is determined by a more
complicated relationship of model parameters, which makes it difficult to isolate any one parameter as a
controlling factor.
The results of the water quality analysis are discussed individually for the three modeled land use scenarios.
Tables comparing the streamflow and pollutant loadings for the three scenarios are provided (Tables 17-20).
The presentation format of the tables is discussed in section 4.4. Analysis results are graphically presented in
Figures A4-A6 in Appendix A.
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25

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4.1 Baseline Condition
The Study Area primarily consists of suburban and rural land uses (Berger 2011). Urban and suburban land uses
are concentrated around Gastonia, NC in the north-central portion of the Study Area - an area corresponding to
the Catawba Creek, Duharts Creek-South Fork Catawba River, and Upper Crowders Creek HUs. In the
northeastern portion of the Study Area, Belmont, NC and the western extent of Charlotte, NC impart an urban
character to the Fites Creek-Catawba River and Paw Creek-Lake Wylie HUs (Figures A1 and A2, Appendix A).
HUs containing a high percentage of impervious surface, as described in Berger (2011), and high average CN
value (Table 15) were found to produce the most runoff on a per acre basis (e.g., Lake Wylie-Catawba River,
Fites Creek-Catawba River, and Paw Creek-Lake Wylie). As expected, these HUs correspond to the urban areas
of Belmont, Gastonia, and Charlotte, NC. The Mill Creek-Lake Wylie HU was found to have the second highest
runoff rate, despite having only the third highest percentage of impervious surface. This result is explained by
the large proportion of the HU comprised by Lake Wylie. In the GWLF model, water surfaces, such as lakes, yield
high amounts of runoff because, unlike soils, water is not considered to have any absorptive capacity. In effect,
all precipitation falling on a waterbody is treated as runoff.
High rates of TN loading may be attributable to several factors: agricultural land, high-density urban land uses,
septic systems, and point source discharges. In the case of the Duharts Creek-South Fork Catawba River HU, the
high TN loading rate is caused by the presence of septic systems and multiple point source dischargers, three of
which are waste water treatment plants (WWTPs). The Fites Creek-Catawba River HU has the second highest TN
and TP loading rates of the Study Area. Here, the high loadings are attributable to a combination of two
WWTPs, urban runoff, and septic systems. Compared to other HUs, the TN loading rate from the Paw Creek-
Lake Wylie HU is seemingly lower than expected: the HU has the highest percentage of urban land uses, but
generates a relatively low amount of TN. Other HUs with lower concentrations of urban land use exceed the TN
loading rate of the Paw Creek-Lake Wylie HU because of the presence of septic systems.
The pattern of TP loading rates in the HUs closely follows the average phosphorus buildup for urban areas: the
TP loading rate increases as the average phosphorus buildup rate increases. Deviations from this relationship
are the result of point source dischargers, namely WWTPs. For instance, the Paw Creek-Lake Wylie HU has the
highest average phosphorus buildup rate and produces the highest rate of TP loading among the HUs without
WWTPs. The Duharts Creek-South Fork Catawba River and Fites Creek-Catawba River HUs have high average
phosphorus buildup rates and both contain WWTPs. Discharge from the WWTPs causes these HUs to surpass
the TP loading rate of the Paw Creek-Lake Wylie HU.
TSS is calculated as a proportion of overland erosion by GWLF. Overland erosion is related to runoff, but is also
influenced by watershed specific conditions such as slope, soil properties, and land use practices. Agricultural
lands used for crop cultivation in particular are major generators of overland erosion. In urban areas,
developed open space and developed low-intensity land uses are the largest generators of overland erosion, but
produce much less erosion than agricultural land uses. Accordingly, these land uses have the comparatively
high TSS loading rates. Due to watershed conditions and a relatively high composition of developed open space
and developed low-intensity land uses, the Duharts Creek-South Fork Catawba River, Fites Creek-Catawba River,
and Upper Crowders Creek produce the highest TSS concentrations. The Paw Creek-Lake Wylie HU is notable
here because the high percentage of developed open space and developed low-intensity land uses would
suggest that the HU rank as one of the highest TSS exporters. However, the slopes and soil properties of the HU
are less conducive to erosion and serve to moderate the erosive potential of these land uses.
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Gaston East-West Connector Wa ter Quality Analysis
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4.2 2035 No Build
Development is predicted to increase throughout the Study Area. Socio-economic factors contributing to the
development are discussed in Berger 2011. The greatest increase in households and residential land use
acreage is expected around Gastonia, NC, in the Catawba Creek, Duharts Creek-South Fork Catawba River, and
Upper Crowders Creek HUs (Figure A2, Appendix A).
The attendant increase in impervious area results in increased modeled runoff across all HUs. The major
contributors of runoff do not change between the Baseline and 2035 No Build scenario. HUs with high
impervious percentages and high average CN values (Table 15) continue to contribute high runoff (Lake Wylie-
Catawba River, Fites Creek-Catawba River, and Paw Creek-Lake Wylie). The Paw Creek-Lake Wylie and Upper
Crowders Creek HUs are projected to experience relatively large increases in urban land uses under the 2035 No
Build scenario. Consequently, these two HUs are predicted to experience the greatest increase in runoff.
TN loading rates increase in all but the Beaverdam Creek-Catawba River and Mill Creek-Lake Wylie HUs, which
see reductions as a result of the expansion of sewer service in the future land use scenarios. The largest TN
exporters are unchanged in the 2035 No Build Scenario: the Duharts Creek-South Fork Catawba River HU
remains the largest exporter of TN, and the Fites Creek-Catawba River and Upper Crowders Creek HUs are also
still among the largest exporters. However, in a departure from the Baseline scenario, the Paw Creek-Lake Wylie
and Lake Wylie-Catawba River HUs transition from low to moderate TN exporters. These HUs experience the
largest increase in TN loading rate as a result of relatively high increases in urban land uses.
A similar pattern was observed for the TP loading rates as well. The Duharts Creek-South Fork Catawba River HU
is still projected to have the largest TP loading rate, just as in the Baseline scenario. Yet, as explained above for
TN, increases in urban land use cause the Paw Creek-Lake Wylie and Lake Wylie-Catawba River HUs to
experience the greatest increase in TP loading rate.
Eight of the nine HUs experience an increase in TSS loading rate as a result of the conversion of less erosive,
undisturbed land uses, namely forest, to more erosive developed land uses. The overall pattern of TSS exporters
changes only for the highest generators - Upper Crowders Creek, Duharts Creek-South Fork Catawba River HUs,
and Fites Creek-Catawba River.
4.3 2035 Preferred Alternative (PA)
The land use condition captured by the 2035 PA scenario is differentiated from the 2035 No Build scenario by
construction of the Project. In aggregate, The 2035 PA scenario would see approximately 1,100 additional acres
of residential development and approximately 100 fewer acres of commercial/industrial/office development in
the Study Area as compared to the 2035 No-Build scenario. The increase in residential development is expected
to produce 3,300 additional households. Most of the resident development (70 percent) is forecasted to occur
in the Catawba Creek and Lower Crowders HUs (Berger 2011). Additionally, 1,500 acres of direct impacts
resulting Gaston East-West Connector right-of-way are expected. Direct impacts will be distributed among the
six HUs traversed by the proposed alignment: Catawba Creek, Duharts Creek-South Fork Catawba River, Lake
Wylie-Catawba River, Lower Crowders Creek, Mill Creek-Lake Wylie, and Upper Crowders Creek HUs.
Five of the nine Study Area HUs add impervious surface cover in the 2035 PA scenario (Berger 2011): Beaverdam
Creek, Catawba Creek, Lake Wylie-Catawba River, Lower Crowders Creek, and Mill Creek-Lake Wylie. The
Catawba Creek and Lower Crowders Creek experience the largest area of change between the 2035 No Build
and the 2035 PA scenarios. Of these HUs, Catawba Creek is projected to have largest increase in development
density as measured by change in impervious surface coverage (Berger 2011) and further evidenced by the
increase in the 2035 No Build and 2035 PA CN values reported in Table 15.
27

Gaston East-West Connector Wa ter Quality Analysis
October 2011- Draft
The HU runoff and pollutant loading rates in the 2035 PA scenario for the most part mirror the pattern observed
for the 2035 No Build scenario: Lake Wylie-Catawba River is still the largest generator of runoff, Duharts Creek-
South Fork Catawba River still has the highest TN loading rate, and so on. While the relationship among the HUs
remains unchanged in terms of which HUs generate the largest runoff and nutrient exports, the predicted runoff
and nutrient loading rates have changed. Differences in runoff and pollutant loading rates observed between
the 2035 PA scenario and 2035 No Build scenarios reflect changes in development density and the type of land
use converted. Specifically, differences in runoff are caused by increased impervious surface coverage in the
2035 PA scenario. Increased in nutrient loads (TN and TP) are attributable to added impervious surface
coverage and the expansion of residential development within septic service areas. HUs with large increases in
the highest density development or the largest increase in households in septic service areas are projected to
experience the largest increase in runoff and nutrient loading. The Catawba Creek HU, which experiences the
largest increase in impervious surface coverage, demonstrates this point: Catawba Creek is projected to have
the largest the increase in nutrient loads and second largest increase in runoff.
It is more difficult to identify such a simple relationship between TSS loading rates and other model parameters
as TSS loading trends are confounded by the number of factors involved in computing sediment yield. Sediment
transport capacity is proportional to runoff and watershed size as reflected in the sediment delivery ratio.
Runoff and erosion change between the No Build and Build scenarios. The degree in land use change is reflected
in the erosion load factors; however, the magnitude of that change does not directly map to the magnitude of
changein TSSload.
4.4 Results Tables
The water quality analysis results are compared in the series of tables that follow (Tables 17-20). Each table
presents the results of a single experimental parameter for the nine HUs composing the Study Area. The
percent difference between the 2035 No Build and 2035 PA results are reported in the rightmost column of the
tables, with the heading "2035 PA - 2035 No Build". The values in this column quantify the water quality effects
of the Project as measured by this analysis.
GWLF consumes the data listed in Table 8 to produce runoff and pollutant loads. The number of decimal places
and significant figures generally used by GWLF for reporting various model outputs are displayed in Table 16.
The significant figures listed in Table 16 determined the significant figures used to report the analysis results in
Tables 17-20. Some pollutant loads are presented as annual loading per unit HU area. In these cases, pollutant
load value is divided by the HU area, which has fewer significant figures. The resulting quotient should contain
five significant figures as the HU area does. However, reported values have been truncated to three or four
significant figures (i.e., three decimal places) to avoid excessively long decimal values.
Table 16:
Runoff (centimeters/ year) � 2 � 5
Total Nitrogen (tons/year) � 4 � 7
Total Phosphorus (tons/year) � 4 � 6
Total Suspended Sediment 1 5
Ron x 1000/vearl
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Gaston East-West Connector Wa ter Quality Analysis
October 2011- Draft
29

Gaston East-West Connector Wa ter Quality Analysis
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Table 17: Comparison of Annual Runoff Results for Baseline Condition. 2035 No Build. and 2035 PA Scenarios.
Paw Creek-Lake Wylie 30501011404 0.00058 0.00111 0.00 89.9 0.00111 0.00 90.1
Fites Creek-Catawba River 30501011405 0.00123 0.00160 0.00 30.4 0.00159 0.00 29.7
Lake Wylie-Catawba River 30501011406 0.00210 0.00267 0.00 273 0.00275 0.00 30.9
Upper Crowders Creek 30501011501 0.00012 0.00023 0.00 89.9 0.00024 0.00 97.5
Catawba Creek 30501011502 0.00030 0.00038 0.00 24.1 0.00041 0.00 34.0
Beaverdam Creek-Catawba 30501011503 0.00023 0.00029 0.00 263 0.00032 0.00 37.4
River
Lower Crowders Creek 30501011504 0.00011 0.00012 0.00 113 0.00013 0.00 19.4
Mill Creek-Lake Wylie 30501011505 0.00165 0.00181 0.00 93 0.00183 0.00 11.0
Duharts Creek-South Fork 30501020605 0.00037 0.00049 0.00 30.1 0.00049 0.00 30.1
Catawba River
1Centimeters per year per acre
ZDifference between future condition and Baseline Condition: future condition - Baseline Condition
3Percent difference between future condition and Baseline Condition: (future condition - Baseline Condition) = Baseline Condition x 100
°Percent difference between 2035 PA and 2035 No Build: (2035 PA - 2035 No Build) = 2035 No Build x 100
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Gaston East-West Connector Wa ter Quality Analysis
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Table 18: Comparison of Annual Total Nitroeen fTN) Results for Baseline Condition. 2035 No Build. and 2035 PA Scenarios.
Paw Creek-Lake Wylie 30501011404 2.475 4.231 1.757 71.0 4.230 1.756 71.0
Fites Creek-Catawba River 30501011405 4.000 6.081 2.081 52.0 5.717 1.717 42.9
Lake Wylie-Catawba River 30501011406 2.208 3.830 1.622 73.5 3.990 1.782 80.7
Upper Crowders Creek 30501011501 3.251 5.043 1.791 55.1 5.004 1.753 53.9
Catawba Creek 30501011502 3.235 5.110 1.875 57.9 5.617 2382 73.6
Beaverdam Creek-Catawba 30501011503 2.267 1.809 -0.457 -20.2 1.917 -0350 -15.4
River
Lower Crowders Creek 30501011504 2.994 3.059 0.064 2.1 3.225 0.231 7.7
Mill Creek-Lake Wylie 30501011505 2.763 2.678 -0.084 -3.1 2.838 0.075 2.7
Duharts Creek-South Fork 30501020605 6.881 8.491 1.610 23.4 8372 1.491 21.7
Catawba River
1Kilograms per year per acre
ZDifference between future condition and Baseline Condition: future condition - Baseline Condition
3Percent difference between future condition and Baseline Condition: (future condition - Baseline Condition) = Baseline Condition x 100
°Percent difference between 2035 PA and 2035 No Build: (2035 PA - 2035 No Build) = 2035 No Build x 100
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Gaston East-West Connector Wa ter Quality Analysis
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Table 19: Comparison of Annual Total Phosphorus fTP) Results for Baseline Condition. 2035 No Build. and 2035 PA Scenarios.
Paw Creek-Lake Wylie 30501011404 0381 0.639 0.258 67.8 0.640 0.258 67.8
Fites Creek-Catawba River 30501011405 0391 0.627 0.235 60.1 0.594 0.203 51.9
Lake Wylie-Catawba River 30501011406 0327 0.591 0.264 81.0 0.620 0.294 90.0
Upper Crowders Creek 30501011501 0350 0.522 0.172 49.1 0.526 0.176 503
Catawba Creek 30501011502 0365 0.500 0.135 36.9 0.542 0.177 48.5
Beaverdam Creek-Catawba 30501011503 0.266 0.284 0.018 6.8 0301 0.035 13.1
River
Lower Crowders Creek 30501011504 0.291 0319 0.028 9.6 0339 0.048 16.4
Mill Creek-Lake Wylie 30501011505 0320 0.413 0.093 29.1 0.432 0.112 34.9
Duharts Creek-South Fork 30501020605 0.524 0.684 0.159 30.4 0.685 0.161 30.7
Catawba River
1Kilograms per year per acre
ZDifference between future condition and Baseline Condition: future condition - Baseline Condition
3Percent difference between future condition and Baseline Condition: (future condition - Baseline Condition) = Baseline Condition x 100
°Percent difference between 2035 PA and 2035 No Build: (2035 PA - 2035 No Build) = 2035 No Build x 100
32

Table 20: Comparison of Annual Total
Gaston East-West Connector Wa ter Quality Analysis
October 2011- Draft
Sediment fTSS) Results for Baseline Condition. 2035 No Build. and 2035 PA Scenarios.
Paw Creek-Lake Wylie 30501011404 380.699 388326 7.627 2.0 389.615 8.915 23
Fites Creek-Catawba River 30501011405 424.103 423.727 -0376 -0.1 422.851 -1.252 -03
Lake Wylie-Catawba River 30501011406 334.567 343.188 8.621 2.6 335.807 1.240 0.4
Upper Crowders Creek 30501011501 419.609 483.732 64.123 153 485.675 66.066 15.7
Catawba Creek 30501011502 300.437 319.820 19383 6.5 327.526 27.089 9.0
Beaverdam Creek-Catawba 30501011503 312.975 331329 18354 5.9 337.982 25.007 8.0
River
Lower Crowders Creek 30501011504 386.523 402.779 16.257 4.2 411.901 25379 6.6
Mill Creek-Lake Wylie 30501011505 347.174 355.615 8.441 2.4 352.184 5.010 1.4
Duharts Creek-South Fork 30501020605 426326 437.216 10.890 2.6 439.951 13.625 3.2
Catawba River
1Kilograms per year per acre
ZDifference between future condition and Baseline Condition: future condition - Baseline Condition
3Percent difference between future condition and Baseline Condition: (future condition - Baseline Condition) = Baseline Condition x 100
°Percent difference between 2035 PA and 2035 No Build: (2035 PA - 2035 No Build) = 2035 No Build x 100
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Gaston East-West Connector Wa ter Quality Analysis
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5.0 CONCLUSIONS
The water quality analysis described in this report was performed in response to the Resource Agencies request
for additional quantitative data on the Preferred Alternative, particularly NCDWQ's request for additional
modeling of pollutant loadings attributable to the Project. As such, the analysis sought to determine how
estimated induced land use changes resulting from the Project may affect water quality throughout the 265-
square mile Study Area defined for the analysis.
The analysis was performed by constructing watershed models for nine 12-digit hydrologic units (HUs)
composing the Study Area (Figure A2, Appendix A) using the BasinSim build of GLWF. Model estimates of annual
runoff and annual overland pollutant loadings of total nitrogen (TN), total phosphorus (TP), and total suspended
sediment (TSS) loads produced from three land use scenarios - Baseline Condition, 2035 No Build, and 2035 PA
(Table 1) - were reviewed to assess the Project effects. Specifically, model results of the 2035 No Build and
2035 PA scenarios were compared.
Five of the nine HUs composing the Study Area contain streams or waterbodies on the 2010 North Carolina or
South Carolina 303(d) list (NCDWQ 2010a, SCDHEC 2010) (Figure 2A, Appendix A): Catawba Creek, Duharts
Creek-South Fork Catawba River, Lower Crowders Creek, Mill Creek-Lake Wylie, and Upper Crowders Creek. The
Project alignment intersects all five HUs. Further, interchanges are planned in all five HUs. The watershed
model results for the Catawba Creek, Lower Crowders Creek, and Mill Creek-Lake Wylie HUs indicate increased
runoff and TN and TP loads in the 2035 PA scenario compared to the 2035 No Build scenario. The model results
indicate increased runoff and TP loads for the Duharts Creek-South Fork Catawba River and Upper Crowders
Creek HUs as well. TN loads, however, decrease for these two HUs as sewer service is expected to be extended
to Developed, High Intensity land uses. An increase in TSS load is expected for 4 of the 5 HUs containing 303(d)-
listed waters. The Mill Creek-Lake Wylie HU is the exception as the TSS loading rate was estimated to decrease
by 1.0 percent.
For the Study Area as a whole, all nine HUs are anticipated to experience some degree of direct or indirect
effects from the Project. Direct effects result from additional paved surface and right-of-way associated with
the Project alignment. Indirect effects are in the form of increased residential development or
commercial/industrial/office development. The result of these effects are apparent in the increases in runoff
and nutrient loading rates projected for all nine HUs. As mentioned above, the Catawba Creek HU experiences
the largest indirect effect and is projected to have the largest increase in runoff and nutrient loadings. Over 80
percent of the land consumed by the direct and indirect effects is forecasted to come from forest and pasture
lands.
Lastly, several further points warrant mentioning. First, the analysis documented in this report was not
conducted for the purpose of predicting the specific amount of pollutants delivered at the outlet of each
modeled HU. Rather, the aim of the analysis was to determine the magnitude of runoff and pollutant loading
change between the 2035 No Build and 2035 PA scenarios. These measurements indicate the trend of water
quality over time in each HU and the Study Area as a whole. And second, in terms of BMPs, the analysis only
considered riparian buffers. No site-specific BMPs, such as bioretention basins, stormwater ponds, grass
swales, etc., are accounted for in the results. Consequently, the watershed model overestimates pollutant
loadings from areas that would otherwise receive stormwater treatment. Site-specific BMPs were omitted due
to a lack information regarding future development. However, the three of the four counties intersected by the
Study Area - Gaston and Mecklenburg Counties, NC and York County, SC - are NPDES Phase II communities.
Under this designation, the counties must require land disturbances greater than or equal to 1 acre to
34

Gaston East-West Connector Wa ter Quality Analysis
October 2011- Draft
implement runoff and pollutant reduction measures (USEPA 2005). Compliance with Phase II rules would likely
result in reduced runoff and nutrient loading rates compared to those produced by the modeled 2035 No Build
and 2035 PA scenarios.
35

Gaston East-West Connector Wa ter Quality Analysis
October 2011- Draft
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at:
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Gaston East-West Connector Wa ter Quality Analysis
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Gaston East-West Connector Wa ter Quality Analysis
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htt p://www.yorkco u ntygov.com/Li n kCl ick.aspx?fi let icket=2CqZGx3faa8%3 D&ta bid=561&m id=1203
41

Appendix A
Large Format Figures

This Page Left Blank Intentionally

�e�e
— PA@ntedine
OStuMArea
'L__�I �unTyBOUntlary
— Inters[ate
— US Poute
NC Route
�! �����11�{L���1
y 11�� �a��R ����I�
ra1 i�[�=T ►, i����I j Y� � i���
�fj��-���A+ r�rrl
�;�+.�yY=r.r�i
� �+�
t°
~� Turnpike Authority
Gaston East-West
Connector
(STIP U-3321)
Qeveland, 6aston, and
Mecklenburg Counties, NC
York County, SC
iiFk
Water Quality
Analysis
Study Area
Figure A1

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Legend
PA Centerline
303 (d)-List Streams - 2010
Named Streams
� Waterbody
OStudy Area
Roads
L_ j County Boundary
Location Map
- Study Area
�Gaston and Mecklenburg Counties, NC
York County, SC
Project
��NORTH CAROLINA
Turnpike Authority
Gaston East-West
Connector
(STIP U-3321)
Cleveland, Gaston, and
Mecklenburg Counties, NC
York County, SC
Title
Study Area
Hydrologic Units
&
Water
Resources
Figure A2

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Le9end
— PACenterline
Runoff (cm/acre/year�*
0 0.00010 - 0.00020
0 >0.00020 - 0.00030
� >0.00030 - 0.00040
- >0.00040 - 0.00050
- >0.00050 - 0.00060
- >0.00100 - 0.00200
- >0.00200 - 0.00300
Percent Change
% -From Baseline to Future Scenario
% -Increase from 2035 No Build
to 2035 PA
%-Decreasefrom 2035 No Build
to 2035 PA
*Note: Intervals not equally distributed.
Prale[[
� NOrsTH UROUNn
; � Turnpike Authority
Gaston East-West
Connector
(STIP U-3321)
Cleveland, Gaston, and
Mecklenburg Counties, NC
York County, SC
Ti[le
Annual
Runoff
for 3
Modeled Scenarios
Figure A3

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Le9end
— PACenterline
TN (kg/acre/year)
� 1.500-2.500
� >2.500 - 3.500
� >3.500 - 4.500
- >4.500 - 5.500
- >5.500 - 6.500
- >6.500 - 7.500
- >7.500 - 8.500
Percent Change
% -From Baseline to Future Scenario
% -Increase from 2035 No Build
to 2035 PA
% -Decrease from 2035 No Build
to 2035 PA
*Note: Intervals not equally distributed.
Prale[[
� NOrsTH <�ROUNn
; / Turnpike Authority
Ti[le
Gaston East-West
Connector
(STIP U-3321)
Cleveland, Gaston, and
Mecklenburg Counties, NC
York County, SC
Annual Total
Nitrogen
for 3
Modeled Scenarios
Figure A4

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Le9end
— PACenterline
TP(kg/acre/year)
� 0.200 - 0300
� >0300-0.400
� >0.400 - 0.500
� >0.500 - 0.600
- >0.600-OJ00
Percent Change
% -From Baseline to Future Scenario
% -Increase from 2035 No Build
to 2035 PA
% -Decrease from 2035 No Build
to 2035 PA
*Note: Intervals not equally distributed.
Prale[[
� NOrsTH <�ROUNn
; / Turnpike Authority
Ti[le
Gaston East-West
Connector
(STIP U-3321)
Cleveland, Gaston, and
Mecklenburg Counties, NC
York County, SC
Annual Total
Phosphorus
for 3
Modeled Scenarios
Figure A5

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Le9end
PA Centerline
TSS (kg/acre/year)
0 300.000 - 325.000
0 >325.000 - 350.000
0 >350.000 - 375.000
0 >375.000 - 400.000
- >400.000 - 425.000
- >425.000 - 450.000
- >450.000 - 475.000
- >475.000 - 500.000
Percent Change
% -From Baseline to Future Scenario
% -Increase from 2035 No Build
to 2035 PA
% -Decrease from 2035 No Build
to 2035 PA
*Note: Intervals not equally distributed.
Prale[[
� NOrsTH <�ROUNn
; / Turnpike Authority
Gaston East-West
Connector
(STIP U-3321)
Cleveland, Gaston, and
Mecklenburg Counties, NC
York County, SC
Ti[le
Annual Total
Suspended
Sediment Load
for 3
Modeled Scenarios
Figure A6

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Appendix B
Select Figures from the Gaston East-West Connector Quantitative
Indirect and Cumulative Effects Analysis

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Appendix C
GWLF-E and RUNQUAL-E Input Parameters

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. . .
Max. seepage meffcient 0.0092 0.0092 unitless BasinSim addition to�GWLF 2.0, default Calibration and Dai et. al 2000
Daily seepage 0.031 0.031 cm BasinSim addition to�GWLF 2.0, default Calibration and Dai et. al 2000
Annual seepage 7.84 7.84 cm BasinSim addition to�GWLF 2.0, default Calibration and Dai et. al 2000
Sediment N 1400 1400 mg/L Dai et. al 2000
Sediment P 352 352 mg/L Dai et. al 2000
groundwater N 0.42 0.42 mg/L Spruil et. al 1998
groundwater P 0.04 0.04 mg/L Spruil et. al 1998
Number of areas had manure
0 0 Not a major problem in the study area Cathey, NRCS, permnal mmmunication, 1/13/11
application
start month 1 1 month Cathey, NRCS, permnal mmmunication, 1/13/11
end month 2 2 month Cathey, NRCS, permnal mmmunication, 1/13/11
N mncentr Ition in runofffor rural z 59 0 mg/L Varies by land use Tetra Tech 2005 and NCDWQ 2007d
andtypes.
P mncentration in runoff for rural 0.4 0 mg/L Varies by land use Tetra Tech 2005 and NCDWQ 2007d
andtypes.
Nbuild-uprateforurbanlandtypes. 0.219 0.191 kg/ha/day Variesbylanduse NCDWQ2007d
P build-up ratefor urban landtypes. 0.04 0.029 kg/ha/day Varies by land use NCDWQ2007d
MonthlyNloadsfrompointsources 13318 0 kg/mo Variesbywatershed NCDWQ2011b
MonthlyPloadsfrompointmurces 695 12 kg/mo Variesbywatershed NCDWQ2011b
Numberof peoplethat use normal Tidd, Louis Berger Group, personal
septicrystems 8190 0 people Variesbywatershed mmmunication,l/10/2011
Assume failure rate of 15%, equally
Number of people that use ponding Tidd, Louis Berger Group, personal
septic rystems 615 0 people divided between ponding and short- mmmunication, 1/10/2011
cicuit

. . .
Numberof eo lethatuseshort- Assumefailurerateofl5%,equally Tidd,LouisBer erGrou
P P 615 0 people divided between ponding and short- g P, Personal
circuit septic rystems mmmunication, 1/10/2011
cicuit
Number of peoplethat use direct 0 0 people Assume no illegal direct discharges Tidd, Louis Berger Group, personal
septic rystems mmmunication, 1/10/2011
Per capita tank effluent load for N 1233 1233 g/day Beutow 2002
PercapitatankeffluentloadforP 1J5 1J5 g/day Beutow2002
plant uptake for N 1.6 1.6 g/day Dai et. al 2000
plant uptake for P 0.4 0.4 g/day Dai et. al 2000
Calculated for calibration watersheds
Recession mef. 0.5 0.5 and held mnstant for remaining Calibration and Amold et. al 1995
watersheds
initial unsat. storage 10 10 cm Effects of initial mnditions diminish Dai et. al 2000
after 3 months
initial saturated storage 0 0 cm Effects of initial mnditions diminish Dai et. al 2000
after 3 months
initial mow 0 0 cm Effects of initial mnditions diminish Dai et. al 2000
after 3 months
sedimentdeliveryratio 0.1592804 0.098 none Basin5im5DRtool
unsaturated zone available water Calculated for calibration watersheds
1431706709 1431706709 cm and held mnstantfor remaining Calibrated and NRCS 2010
capacity watersheds
Antecedent precipitation for day d Effects of initial mnditions diminish
to day -5 0 0 cm after 3 months Dai et. al 2000
Monthly ET mver mef. 1.08 03 unitless Area weighted average by month Calibration and Dai et. al 2000
Monthly day hours 143 9.6 hours Dai et. al 2000
Monthlygrowingseamn�l=yes/ 1 0 Boolean SC51989.SoilSurveyofGastonCounty,NC.
0=no)
erosivitymefficient 033 0.12 none ValuesforCharlotte,NC Daiet.a12000
curve number 100 48 none Varies by land use USSC51975

. . .
USLE—Kfactor 031 0.19 tons/acre/unit Variesbywatershed NRC52010
area
USLE—LSfactor 5.904 3.111 unitless Variesbywatershed LauraGarrett,NEDandNCFMPDEMs
USLE—Cfactor 1 0 unitless Seesection3.2.8 Wischmeir,W.H.,andD.D.Smith1978
Worst case assumption of no support
USLE—Pfactor 1 1 unitless practicesareappliedtoattenuatesoil Wischmeir,W.H.,andD.D.Smith1978
erosion
landtypearea 7268.66 0 hectare 1 Berger2011

Appendix D
Correspondence with N.C. Division of Water Quality Regarding
Analysis Methodology

This Page Left Blank Intentionally

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an Atkins company
To: Polly Lespinasse, Brian Wrenn, Colin Mellor
From: Brad Allen
CC: Christy Shumate, Jennifer Harris, Jill Gurack, David O'Loughlin
Date: October 22, 2010; Updated
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Re: Minutes for Gaston ICE Water Quality Analyis Meeting with NCDWQ
Attendees:
• Polly Lespinasse (NCDWQ)
• Brain Wrenn (NCDWQ)
• Colin Mellor (NCDOT
• Dave O'Loughlin (PBS&J)
• Brad Allen (PBS&J)
On October 18, 2010, the above personnel from the NC Division of Water Quality (NCDWQ), NC
Department of Transportation (NCDO�, and PBS&J met at the NCDWQ Winston-Salem, NC office.
The purpose of the meeting was to discuss issues related to the Gaston East/West Connector (the
Project) indirect and cumulative effects (ICE) water quality analysis (Analysis).
The meeting started with PBS&J summarizing the status of the Analysis. PBS&J explained work had
begun to develop the Analysis methodology, but they had reached a point at which they would like to
receive NCDWQ's approval on several key elements of the proposed Analysis before moving forward.
The focus of the meeting was then turned to the following six questions identified by PBS&J as
requiring resolution.
Is it acceptable to use the quantitative ICE boundary for the Analysis?
The Gaston East-West Connector Quantitative lndirect and Cumulative Effects Analysis
(August 3, 2010) was prepared by Louis Berger Group. The report was posted on the
NCTA website and environmental resource and regulatory agencies were nofified and
asked to review and comment. To date, no commenfs have been received.
2. Are the 12-digit Hydrologic Units (HUs) acceptable reporting units forthe Analysis results?
3. Is focusing the Analysis on non-point source nitrogen, phosphorus, and sediment
adequate for addressing regulatory agency concerns over the ProjecYs ICE?
• Page 1

4. Is it acceptable to only consider the effect of riparian buffer best management
practices (BMPs) in the Analysis?
5. Is the resolution of the forecast-zone scale for which No Build and Build land use
forecasts are reported adequate for the Analysis?
6. Is PBS&J's recommended approach for processing the forecast data of the future
land use scenarios acceptable?
The resolution and discussion corresponding to each question are summarized below.
1. ls it acceptab/e to use the quantitative lCE boundary for the Analysis?
Resolution: No resolution was reached during the meeting.
Resolution Update: Brian Wrenn of NCDWQ responded to this issue in an email on October 22,
2010. In the email, he requests that the Fites Creek-Catawba River 12-digit hydrologic unit (H UC
30501011405) be included in the study area of the ICE quantitative land use and water quality analysis.
Brian's email is included at the end of this memorandum as a record of documentation.
NCDWQ had questions regarding the quantitative ICE boundary and requested to withhold comments
on the matter until those questions are answered . Specifically, NCDWQ questioned why the 12-digit
H Us highlighted in green and marked with asterisks in the below figure were not included in the
quantitative ICE analysis. The point was made that both HUs are in the vicinity of the proposed
roadway alignment, and both appear to have open space available for development. Neither Colin nor
PBS&J could provide an answer, but agreed to find out why the HUs were not considered. PBS&J will
inform NCDWQ of the findings. At which time, NCDWQ will then provide an opinion on the suitability of
the quantitative ICE boundary for the Analysis.
• Page 2

In answer to NCDWQ's questions concerning the quantitative ICE boundary, PBS&J has identifi�' that
sections 2.1.1 ano' 2.1.2 of the Gaston East- West Connector Quantitative Indirect and Cumulative
Effects Analysis explain the exclusion of the HUs. The content of both s�tions is provid�' below.
PBS&J requests that NCDWQ reply to indicate if the explanations are sufficient.
2.1.1 Gaston County
In Gaston County, a small portion of the northwest corner of the
qualitative ICE study area was removed, including the northern half of
Bessemer City and part of Gastonia. To the east of Gastonia, a portion of
Belmont and an adjacent unincorporated area along the 1-85 corridor
was removed. The transportation modeling conducted for the project with
the Metrolina Travel Demand Model shows that the TAZs in these areas
would notexperience any substantial change in travel times as a result of
the Gaston East- West Connector and thus are unlikely to experience
growth pressures attributable to the project. The reason this area would
not experience substantial changes in accessibility is that it is already in
close proximity to 1-85, which is the existing primary east-west roadway
and crossing of the Catawba River in Gaston County.
The study area was expanded to the north to include the entirety of the
Duharts Creek-South Fork Catawba River subwatershed
(030501020605). The expanded area includes parts of Gastonia, Lowell,
McAdenville, Ranlo and Spencer Mountain. This expansion of the study
area was made only for the purpose of including the entire watershed in
the study area, not because of accessibility changes in this area.
2.1.2 Mecklenburg County
In Mecklenburg County, the study area was expanded to include the
entire Paw Creek-Lake Wylie subwatershed (030501011404). Although
there are not substantial accessibility changes for this watershed, it does
contain part of two important No Build condition projects-- the Charlotte-
Douglas International Airport third runway and intermodal freight facility.
A portion of the study area to the east of 1-485 was removed based on
the results of the projected travel time improvements being the greatest
around and to the east of the Gaston East- West Connector's interchange
with 1-485. The subwatersheds in this location (030501030103- Upper
Sugar Creek and 030501030108- Steele Creek) are within a heavily
developed portion of the City of Charlotte and would be unlikely to
experience further environmental impacts from land use change because
the majority of the land in these subwatersheds is already developed.
While a portion of the Charlotte-Douglas International Airport is within the
Upper Sugar Creek watershed, the primary considerations in terms of
cumulative impacts (the new runway and the proposed intermodal
facility) are not and remain within the study area for the quantitative ICE
assessment.
Additionally, NCDWQ mentioned that a population of Carolina heelsplitter (Lasmigona d�orata) may
have been found in the Catawba River; although, they were not sure of the details. The heelsplitter has
hereunto not been mentioned as an issue for this project. PBS&J will investigate this matter and inform
NCDWQ of the findings.
• Page 3

2. Are the 12-digit HUs acceptable reporting units for the Analysis results?
Resolution: NCDWQ confirmed that the 12-digit HUs are acceptable.
This question generated little discussion as it is typical to report the results of such analyses at the 14-
digit or 12-digit HU scale.
3. Is focusing the Analysis on non-point source nitrogen, phasphorus, and sediment
adequate for addressing regulatory agency concems over the ProjecYs ICE?
Resolution: NCDWQ confirmed that modeling non-poir�t source nitrogen, phosphorus, and sedimer�t is
adequate, but the analysis may need to be expanded to include metal loadings.
The topic of inetal pollution came up while reviewing impaired parameters for 303(d)-listed water s in
the project study area; the Catawba River is impaired in part for copper standard violations. Colin
meritioned metal pollution (such as copper and zinc) from highway runoff has become an issue of
increasing concern at NCDOT. Yet, no previous water quality analyses performed in support of
roadway ICE analyses in North Carolina have considered metal loadings. In fact, it is still unclear how
metals should be addressed in such analyses or if they should be considered at all. Colin and PBS&J
will continue to irrvestigate the issue. NCDWQ recommended contacting Cindy Moore or Carol
Hollenkamp in NCDWQ's Aquatic Toxicology unit for assistance. Depending on the findings, the metal
loadings may be incorporated into the analysis.
4. Is it acceptable to only consider the effect of riparian buffer BMPs in the Analysis?
Resolution: NCDWQ confirmed that considering only riparian buffer BMPs is acceptable.
PBS&J discussed the uncertainty involved in modeling structural stormwater BMPs — bioretention
basins, stormwater ponds, grass swales, etc —for future land use conditions. It was PBS&J's
conterition that such BMPs should not be considered in the water quality model. Instead, a qualitative
discussion of these BMPs will be provided in the Analysis report. NCDWQ agreed.
5. Is the resolution of the traffic analysis zone (TAZ) (or forecast-zone) scale for which No
Build and Build land use forecasts are reported adequate for the Anal ysis?
Resolution: NCDWQ confirmed that the forecast zones used to report the No Build and Build land use
forecasts were adequate. Further, NCDWQ requested that the Existing land use be aggregated to the
forecast-zones too. The purpose in normalizing all the land use datasets to the forecast zones is to
provide consistent reporting scale for all land use scenarios.
PBS&J discussed the format of the Existing, No Build, and Build land use datasets developed by the
Louis Berger Group. It was noted that the Existing land use was formatted as a spatially-explicit raster
dataset with a 30-meter resolution. In contrast, the No Build and Build land use datasets are not
spatially explicit and are constructed at the much coarser resolution of the forecast zones. Because of
the varying resolutions of the land use datasets, separate techniques would need to be used to
generate model parameters and the reporting of results would differ too. NCDWQ expressed concern
over this seeming disparity between the Existing dataset and future land use forecasts, stating that it
creates doubt that a direct comparison of pollutant loadings can be made. Esseritially, the Analysis
would not provide an "apples to apples" comparison if the land use datasets are not normalized to a
• Page 4

consistent scale. PBS&J and Colin acknowledged as much. Two solutions were then discussed: 1)
spatially-explicit future land use forecasts could be generated to match the format of the Existing
dataset or 2) the spatially-explicit Existing dataset could be aggregated to the forecast-zone scale to
match the format of the future land use forecasts. Ultimately, it was decided to pursue the second
option.
6. Is PBS&J's recommended approach forprocessing the forecast data of the
future land use scenarios acceptable?
Resolution: NCDWQ suggested the approach detailed in question 5 above.
NCDWQ, as well as Colin and PBS&J, felt that PBS&J's initial recommendation to process the lower
resolution future land use datasets in a different manner than the Existing dataset would introduce
unnecessary confusion ir�to the Analysis and subsequer�t report. All attendees concluded an
alternative approach in which the Existing dataset would be aggregated to the forecast-zone scale to
match the lower resolution format of the future land use forecasts should be used. By processing the
Existing dataset to match the format of the future land use forecasts, the same techniques can be used
to calculate the water quality model parameters for all three land use scenarios. This will eliminate the
need to explain and justify the use of separate modeling techniques for the Existing and future land use
scenarios.
• Page 5

Allen, Thomas B
From: Wrenn, Brian
Sent: Friday, October 22, 2010 10:26 AM
To: Allen, Thomas B; Lespinasse, Polly; Mellor, Colin
Cc: jsgurak,; Shumate, Christy; Harris, Jennifer; O'Loughlin, David K
Subject: RE: Minutes for Gaston WQ Analysis Meeting
I have one comment regarding the minutes. For the explanation of excluding the watersheds in Gaston
Co. near Bessemer City, although I can understand the travel time savings will not be significantly
increased for the northern portion of the HUC, surely there will be some induced growth south of 85
and 29. I think this HUC should be included in the analysis. Several of the HUCs included in the analysis
have portions that will not experience significant travel time savings, but they are still part of the study
area. No reason for this HUC to be excluded. That being said, Polly holds the trump card in this, so if
she disagrees with me, I will concede.
Brian Wrenn
Transportation Permitting Unit, Supervisor
NC Division of Water Quality
brian.wrenn @ncdenr.¢ov
585 Waughtown Street
Winston-Salem, NC 27107-2241
336-771-4952 (Winston-Salem no.)
336-771-4631(Fax)
or
2321 Crabtree Blvd., Ste 250
Raleigh, NC 27103
919-733-5715 (Raleigh no.)
919-733-6893 (Raleigh Fax)
From: Allen, Thomas B [mailto:[e-mail]]
Sent: Friday, October 22, 2010 10:02 AM
To: Wrenn, Brian; Lespinasse, Polly; Mellor, Colin
Cc: jsgurak,; Shumate, Christy; Harris, Jennifer; O'Loughlin, David K
Subject: Minutes for Gaston WQ Analysis Meeting
Polly, Brian, Colin:
Please find attached the minutes for the Gaston East/West Connector water quality analysis meeting
held on October 18, 2010. Perhaps the largest outstanding question from the meeting was why were
12-digit HUs 030501011405 (Fites Creek-Lake Wylie) and 030501030103 (Sugar Creek Headwaters)
excluded from the study area? An explanation to this question is provided in the minutes. Brian and
Polly, would you please review the explanation and let me know if it is sufficient. Feel free to contact
me if you have any further questions or comments.
Thanks,

Brad Allen, E.I.
Senior Scientist
PBS&J - Mid-Atlantic Sciences
1616 E. Millbrook Road, Suite 310
Raleigh, NC 27609
Office: 919.876.6888 (Main)
Office: 919.431.5222 (Direct)
Fax: [phone]
tballenCa)pbsi.com
www.pbsi.com