HomeMy WebLinkAboutFourthCkTurbidityTMDL-FinalReport
Total Maximum Daily Load (TMDL)
For Turbidity
Final Report
May 2004
Fourth Creek (Subbasin 03-07-06)
Yadkin River Basin
North Carolina
Prepared by:
NC Department of Environment and Natural Resources
Division of Water Quality
Water Quality Section
1617 Mail Service Center
Raleigh, NC 27699-1617
(919) 733-5083
Fourth Creek Turbidity TMDL November 2003
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Fourth Creek Turbidity TMDL November 2003
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INDEX OF TMDL SUBMITTAL
303(d) List Information
State: North Carolina
Counties: Iredell and Rowan
Basin: Yadkin River Basin
303(D) LISTED WATERS
Name of Stream Description Class Index # Subbasin Miles
Fourth Creek From SR 2308 Iredell
Co 1.5 mile upstream.
C 12-108-20-(1)b 30706 9.5
14 digit HUC or Cataloging Unit(s) 3040102030010 and 3040102030020
Area of Impairment 9.5 miles
WQS Violated Turbidity
Pollutant of Concern Turbidity
Applicable Water Quality Standards for Class
C Waters:
Turbidity not to exceed 50 NTU
Sources of Impairment Nonpoint sources throughout watershed
Public Notice Information
A draft of the TMDL was publicly noticed through various means, including notification in a
local newspaper, the Statesville Record and Landmark on February 24, 2004. The TMDL
was also available from the Division of Water Quality’s website during the comment period
at: http://h2o.enr.state.nc.us/tmdl/TMDL_list.htm.
The public comment period began February 24 and was held for 30 days. A public meeting
was held on March 26 at the Old City Hall Building, Council Chambers, 301 South Center
Street, in Statesville, North Carolina.
Did notification contain specific mention of TMDL proposal? Yes
Were comments received from the public? No
Was a responsiveness summary prepared? No
Fourth Creek Turbidity TMDL November 2003
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TMDL Information
Critical conditions: Hydrologically high flow conditions during all seasons but
particularly during late winter and early spring.
Seasonality: TMDL is based on meeting the target standard during all seasons and
is applied on an annual basis.
Development tools: Load duration curves based on cumulative frequency distribution of
flow conditions in the watershed. Allowable loads are average loads
over the recurrence interval between the 95th and 10th percent flow
exceeded (excludes extreme drought (>95th percentile) and floods
(<10th percentile). Percent reductions expressed as the average value
between existing loads (calculated using an equation to fit a curve
through actual water quality violations) and the allowable load at
each percent flow exceeded.
Supporting
documents:
Total Maximum Daily Load (TMDL) For Turbidity in Fourth Creek,
NC Division of Water Quality (2004)
TMDL Allocations TSS Load (lbs/day)
Existing 19,703
WLA - NC0031836 (4 MGD, 30 mg TSS/L limit) 1,001
WLA - NC0082821 (0.114 MGD, 30 mg TSS/L limit) 29
Sum of WLAs 1,030
LA – Urban 1,044
LA – Rural (Non-Urban) 8,445
Sum of LAs 9,489
MOS Explicit 10%
TMDL 10,519
TMDL – Percent Reduction Required 47%
WLA = wasteload allocation, LA = load allocation, MOS = margin of safety
Fourth Creek Turbidity TMDL November 2003
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TABLE OF CONTENTS
INDEX OF FIGURES.............................................................................................................................. VII
INDEX OF TABLES................................................................................................................................ VII
1.0 INTRODUCTION .................................................................................................................................. 1
1.1 WATERSHED DESCRIPTION.............................................................................................................. 2
1.1.1 Land use/ Land cover.............................................................................................................. 3
1.1.2 Geology................................................................................................................................... 5
1.1.3 Soils ........................................................................................................................................ 5
1.2 WATER QUALITY MONITORING PROGRAM...................................................................................... 7
1.2.1 Chemical Monitoring.............................................................................................................. 7
1.2.2 Biological Monitoring............................................................................................................. 8
1.3 WATER QUALITY TARGET............................................................................................................... 9
2.0 SOURCE ASSESSMENT .................................................................................................................... 10
2.1 ASSESSMENT OF POINT SOURCES .................................................................................................. 10
2.1.1 NPDES-Regulated Municipal and Industrial Wastewater Treatment Facilities .................. 10
2.1.2 NPDES General Permits ...................................................................................................... 11
2.2 ASSESSMENT OF NONPOINT AND STORMWATER SOURCES ............................................................ 11
2.2.1 Stormwater Discharges in the Fourth Creek Basin.............................................................. 12
2.2.2 Load Duration Curve............................................................................................................13
2.3 DATA SOURCES ............................................................................................................................. 15
3.0 TECHNICAL APPROACH ................................................................................................................ 16
3.1 TMDL ENDPOINTS........................................................................................................................ 16
3.2 LOAD DURATION CURVE............................................................................................................... 16
3.3 ASSIMILATIVE CAPACITY .............................................................................................................. 17
4.0 TMDL CALCULATION ..................................................................................................................... 18
4.1 TMDL ENDPOINTS........................................................................................................................ 19
4.2 CRITICAL CONDITIONS .................................................................................................................. 19
4.3 SEASONAL VARIATION .................................................................................................................. 19
4.4 MARGIN OF SAFETY ...................................................................................................................... 19
4.5 RESERVE CAPACITY ...................................................................................................................... 19
4.6 TMDL CALCULATION................................................................................................................... 20
4.7 WASTELOAD AND LOAD ALLOCATIONS ........................................................................................ 21
5.0 FOLLOW – UP MONITORING......................................................................................................... 23
6.0 IMPLEMENTATION.......................................................................................................................... 23
7.0 PUBLIC PARTICIPATION................................................................................................................ 26
8.0 ADDITIONAL INFORMATION........................................................................................................ 26
REFERENCES ........................................................................................................................................... 27
APPENDIX A. DWQ AMBIENT MONITORING AND DISCHARGER COALITION DATA........ 30
APPENDIX B. MONTHLY AVERAGE EFFLUENT TSS CONCENTRATIONS (MG/L) AT THE
STATESVILLE WWTP (NC0031836) AND SOUTHERN STATES COOPERATIVE FACILITY
(NC0082821) DURING YEARS 1998-2003.............................................................................................. 36
Fourth Creek Turbidity TMDL November 2003
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APPENDIX C. GENERAL PERMITEES LOCATED WITHIN THE FOURTH CREEK
WATERSHED. ........................................................................................................................................... 37
APPENDIX D. METHODOLOGY FOR DEVELOPING THE LOAD DURATION CURVE .......... 39
APPENDIX E. LOAD REDUCTION ESTIMATES FOR TURBIDITY IN FOURTH CREEK....... 40
APPENDIX F. RELATIVE POLLUTANT CONTRIBUTIONS FROM THE USGS REPORT
“RELATION OF LAND USE TO STREAMFLOW AND WATER QUALITY AT SELECTED
SITES IN THE CITY OF CHARLOTTE AND MECKLENBURG COUNTY, NORTH CAROLINA,
1993-98” (USGS, 1999)............................................................................................................................... 42
APPENDIX G. AGRICULTURE SEDIMENT SURVEY/ACTION PLAN FOR FOURTH CREEK –
IREDELL COUNTY CONDUCTED BY THE SOIL AND WATER CONSERVATION DISTRICT,
IREDELL COUNTY IN 1999.................................................................................................................... 43
APPENDIX H. PUBLIC NOTIFICATION OF PUBLIC REVIEW DRAFT OF FOURTH CREEK
TURBIDITY TMDL................................................................................................................................... 50
Fourth Creek Turbidity TMDL November 2003
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INDEX OF FIGURES
FIGURE 1. FOURTH CREEK WATERSHED AND SURROUNDING AREA. IMPAIRED STREAM LENGTHS
ARE BASED ON THE IMPAIRED WATERS LIST (2002 INTEGRATED 305(B) AND 303(D)
REPORT) AND MONITORING CONDUCTED SUBSEQUENT TO THE 2002 LISTING.......................... 3
FIGURE 2. LAND USE/ LAND COVER DISTRIBUTION WITHIN THE FOURTH CREEK WATERSHED....... 4
FIGURE 3. DETAILED LAND USE/ LAND COVER DISTRIBUTION WITHIN FOURTH CK WATERSHED... 4
FIGURE 4. FOURTH CREEK WATERSHED INCLUDING AREAS OF BENTHIC MACROINVERTEBRATE
AND FISH MONITORING, AMBIENT CHEMICAL MONITORING, AND WASTEWATER TREATMENT
DISCHARGES......................................................................................................................................... 8
FIGURE 5. LINEAR REGRESSION FOR TSS-TURBIDITY AT FOURTH CREEK AT SR 2308 NEAR
ELMWOOD, NC (USGS STATION #02120780) USING DATA COLLECTED DURING YEARS 1997-
2003..................................................................................................................................................... 14
FIGURE 6. EXAMPLE LOAD DURATION CURVE....................................................................................... 14
FIGURE 7. FOURTH CREEK AT USGS STATION 02120780 (FOURTH CREEK AT SR 2308 NEAR
ELMWOOD); FLOW DURATION AND TSS CONCENTRATION DURING YEARS 1997-2003........ 17
FIGURE 8. FOURTH CREEK AT USGS STATION 02120780 (FOURTH CREEK AT SR 2308 NEAR
ELMWOOD); LOAD DURATION CURVE USING WATER QUALITY DATA FROM YEARS 1997-
2003..................................................................................................................................................... 18
FIGURE 9. FOURTH CREEK AT USGS STATION 02120780 (FOURTH CREEK AT SR 2308 NEAR
ELMWOOD); LOAD DURATION CURVE WITH REGRESSION LINE USING WATER QUALITY FROM
YEARS 1997-2003.............................................................................................................................. 21
INDEX OF TABLES
TABLE 1 SURFACE RUNOFF AND THE HAZARD OF WATER EROSION CHARACTERISTICS ARE
PRESENTED FOR PREDOMINANT SOIL SERIES (BOLDED) AND LESS DOMINANT SOILS SERIES
(NON-BOLDED) IN THE FOURTH CREEK WATERSHED. LESS DOMINANT SOIL SERIES INCLUDE
ONLY SERIES THAT DISPLAYED A HIGH HAZARD OF WATER EROSION CLASSIFICATION (USDA
1995; USDA, 1964)............................................................................................................................. 6
TABLE 2 “HAZARD OF WATER EROSION” CLASSIFICATIONS AS DEFINED BY THE NRCS................. 6
TABLE 3 BIOLOGICAL AND HABITAT RATINGS AT THE SIX MONITORING STATIONS IN THE FOURTH
CREEK WATERSHED............................................................................................................................. 9
TABLE 4 CORRELATION COEFFICIENTS FOR TURBIDITY AT DWQ AMBIENT STATION # Q3735000.
.............................................................................................................................................................. 13
TABLE 5 FLOW STATISTICS FOR USGS GAGE STATION #02120780 DURING YEARS 1979-2003... 16
TABLE 6 NUMBER OF VIOLATIONS TO THE 50 NTU STANDARD FOR EACH MONTH DURING THE
1997-2003 PERIOD............................................................................................................................. 19
TABLE 7 UNALLOCATED TMDL LOAD AND ASSOCIATED PERCENT REDUCTION ............................ 21
TABLE 8 RELATIVE POLLUTANT CONCENTRATIONS USING USGS (1999) STUDY AND FOURTH
CREEK LANDUSE................................................................................................................................22
TABLE 9 FOURTH CREEK TMDL WASTELOAD AND LOAD ALLOCATIONS FOR TURBIDITY
EXPRESSED AS LBS/DAY TSS............................................................................................................ 23
1.0 Introduction
The 2002 North Carolina Water Quality Assessment and Impaired Waters List (also
known as the Integrated 305(b) and 303(d) Report) identified Fourth Creek in the Yadkin
River Basin as impaired by elevated turbidity. Based on this report, the impaired segment
(assessment unit 12-108-20-(1)b) includes a 9.5-mile segment located in subbasin 03-07-
06 between State Route 2308 in Iredell County downstream to 1.5 miles upstream of
Rowan County State Road 1985 in Rowan County. Subsequent to the 2002 listing,
additional monitoring has been conducted and suggests that the area of impairment
includes the Fourth Creek from its source to SR 1972 (Figure 1). This report will
establish a Total Maximum Daily Load (TMDL) for turbidity for the entire Fourth Creek
watershed. This report will serve as a management approach or restoration plan aimed
toward reducing loadings of sediment from various sources in order to attain applicable
surface water quality standards for turbidity.
In accordance with Section 305(b) of the Federal Clean Water Act (CWA) (33 U.S.C.
1315(B)), the State of North Carolina is required to biennially prepare and submit to the
USEPA a report addressing the overall water quality of the State’s waters. This report is
commonly referred to as the 305(b) Report or the Water Quality Inventory Report. In
accordance with Section 303(d) of the Clean Water Act (CWA), the State is also required
to biennially prepare and submit to USEPA a report that identifies waters that do not
meet or are not expected to meet surface water quality standards (SWQS) after
implementation of technology-based effluent limitations or other required controls. This
report is commonly referred to as the 303(d) List. The 303(d) process requires that a
TMDL be developed for each of the waters appearing on Category 5 of North Carolina’s
Water Quality Assessment and Impaired Waters List (formerly Part 1 of North Carolina’s
303(d) list). The objective of a TMDL is to quantify the amount of a pollutant a water
body can assimilate without violating a state’s water quality standards and allocate that
load capacity to point and nonpoint sources in the form of wasteload allocations (WLAs),
load allocations (LAs), and a margin of safety (MOS) (USEPA, 1991). Generally, the
primary components of a TMDL, as identified by EPA (1991, 2000) and the Federal
Advisory Committee (USEPA FACA, 1998) are as follows:
Target identification or selection of pollutant(s) and end-point(s) for consideration.
The pollutant and end-point are generally associated with measurable water
quality related characteristics that indicate compliance with water quality
standards. North Carolina indicates known pollutants on the 303(d) list.
Source assessment. All sources that contribute to the impairment should be identified
and loads quantified, where sufficient data exist.
Reduction target. Estimation or level of pollutant reduction needed to achieve water
quality goal. The level of pollution should be characterized for the waterbody,
highlighting how current conditions deviate from the target end-point. Generally,
this component is identified through water quality modeling.
Fourth Creek Turbidity TMDL November 2003
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Allocation of pollutant loads. Allocating pollutant control responsibility to the
sources of impairment. The wasteload allocation portion of the TMDL accounts
for the loads associated with existing and future point sources. Similarly, the load
allocation portion of the TMDL accounts for the loads associated with existing
and future non-point sources, stormwater, and natural background.
Margin of Safety. The margin of safety addresses uncertainties associated with
pollutant loads, modeling techniques, and data collection. Per EPA (2000), the
margin of safety may be expressed explicitly as unallocated assimilative capacity
or implicitly due to conservative assumptions.
Seasonal variation. The TMDL should consider seasonal variation in the pollutant
loads and end-point. Variability can arise due to stream flows, temperatures, and
exceptional events (e.g., droughts, hurricanes).
Critical Conditions. Critical conditions indicate the combination of environmental
factors that result in just meeting the water quality criterion and have an
acceptably low frequency of occurrence.
Section 303(d) of the CWA and the Water Quality Planning and Management regulation
(USEPA, 2000) require EPA to review all TMDLs for approval or disapproval. Once
EPA approves a TMDL, then the waterbody may be moved to Category 4a of the
Integrated 305(b) and 303(d) Report. Waterbodies remain in Category 4a until
compliance with water quality standards is achieved. Where conditions are not
appropriate for the development of a TMDL, management strategies may still result in
the restoration of water quality.
The goal of the TMDL program is to restore designated uses to water bodies. Thus, the
implementation of sediment controls throughout the watershed will be necessary to
restore uses in the most downstream portion of Fourth Creek. Although a site specific
implementation plan is not included as part of this TMDL, reduction strategies are
needed. The involvement of local governments and agencies will be critical in order to
develop implementation plans and reduction strategies. Implementation discussion will
begin during public review of the TMDL.
1.1 Watershed Description
Fourth Creek is located within the Inner Piedmont region of the Yadkin-Pee Dee River
Basin and flows in a southeasterly direction from near the town of Stony Point in Iredell
County through Statesville to its confluence with Third Creek in rural Rowan County
(see Figure 1). The majority of the impaired stream segment is located in the downstream
portion in Rowan County, however, this TMDL will address the entire watershed of
Fourth Creek (approximately 83 square miles) which includes approximately 116 river
miles (approximately 30 miles in the mainstem Fourth Creek and 86 miles of tributaries
to Fourth Creek) upstream of its confluence with Third Creek. Two named tributaries,
Morrison Creek and Gregory Creek, are located in the watershed and are located in the
southwest portion of the watershed, west of the city of Statesville. Fourth Creek consists
Fourth Creek Turbidity TMDL November 2003
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of two USGS 14-digit hydrologic unit codes (HUCs); units 3040102030010 and
3040102030020.
Figure 1. Fourth Creek watershed and surrounding area. Impaired stream lengths are
based on the Impaired Waters List (2002 Integrated 305(b) and 303(d) Report) and
monitoring conducted subsequent to the 2002 listing.
Rowan County
Statesville
Iredell County
Davie County
Fourth Creek
Gregory Creek
New reach identified as impaired based on
monitoring subsequent to the 2002 Integrated
303(d) and 305(b) List.
Morrison Creek
Impaired portion of Fourth Creek based on
Category 5 of the 2002 Integrated 303(d) and
305(b) List of Impaired Waterbodies
Yadkin River Basin
Catawba River
Basin
Statesville Boundary
Fourth Ck HUC 14s
County Boundaries
Fourth Creek
Morrison Creek
Gregory Creek
2002 Impaired Length
Newly Impaired Length
NFourth Creek
3 0 3 6 Miles
1.1.1 Land use/ Land cover
The land use/land cover characteristics of the watershed were determined using 1996 land
cover data that were developed from 1993-94 LANDSAT satellite imagery. The North
Carolina Center for Geographic Information and Analysis, in cooperation with the NC
Department of Transportation and the United States Environmental Protection Agency
Region IV Wetlands Division, contracted Earth Satellite Corporation of Rockville,
Maryland to generate comprehensive land cover data for the entire state of North
Carolina. Land cover/land use data for the Fourth Creek watershed are identified in
Figures 2 and 3. During the formation of this geographic dataset, the proportion of
synthetic cover was used to identify developed land as either low density developed (50-
80% synthetic cover) or high density developed (80-100% synthetic cover) (Earth
Satellite Corporation, 1997). Assuming that synthetic cover is impervious, and that all
non-developed land cover classes have 1% impervious cover, the Lower Fourth Creek
watershed is estimated to have 4.9-6.5% impervious surface.
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Figure 2. Land use/ land cover distribution within the Fourth Creek watershed.
Statesville
G en eral Landuse
Cultivated C rop
Forest/W etland
P asture/M anag ed H erbaceous
U rb an
W ater
0 2 4 M iles
N
Figure 3. Detailed land use/ land cover distribution within Fourth Ck watershed.
Cultivated Crop
6.44%
Water
0.23%
Urban
6.09%
Forest/Wetland
48.52%
Pasture/Managed
Herbaceous
38.71%
0.44% Evergreen Shrubland
0.27% Deciduous Shrubland
44.02% Mixed Hardwoods
0.04% Hardwood Swamps
0.01% Other Broadleaf Deciduous Forests
0.06% Mountain Conifers
0.64% Southern Yellow Pine
0.04% Other Needleleaf Evergreen Forests
3.00% Mixed Hardwoods/Conifers
38.50% Managed Herbaceous Cover
0.21% Unmanaged Herbaceous Upland
2.88% Low Intensity Developed
Fourth Creek Turbidity TMDL November 2003
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1.1.2 Geology
Iredell County is in the heart of the Piedmont physiographic province. Predominantly,
three rock types occur in the Fourth Creek watershed; composite gneiss, hornblende
gneiss, and gabbro-diorite (LeGrand, 1954).
1.1.3 Soils
Soils types and characteristics vary throughout the Fourth Creek watershed. In the
headwaters portion, west and north of Statesville, predominant soils include Lloyd-Cecil
and Lloyd series. In the central portion the watershed, inclusive of the Statesville area
downstream to the Iredell-Rowan Counties border, the primary soils include Cecil-
Appling, Lloyd, and Iredell-Mecklenburg-Lloyd series. The predominant soils in the
lower portion of the watershed, in Rowan County, include Enon, Mecklenburg,
Hiwassee, Cecil, and Poindexter soil series. A number of these soil types exhibit above-
normal erodeability. A description of the runoff and erosion potential for several soils in
the Fourth Creek watershed are presented in Table 1. Soils highlighted bold are the
predominant soils of the watershed; non-bold soils listed are present in the Fourth Creek
watershed and exhibit highly erosive characteristics. Soils in Rowan County were
identified as predominant based on GIS analysis (coverages using 1995 updated soil
survey) and, in the case of Iredell County, analysis of soil survey maps (maps updated in
1964). GIS Soils (SSURGO) coverages are currently not available for Iredell County.
Surface runoff and hazard of water erosion values were obtained from the NRCS and are
defined below in Table 2 (USDA, 1995; USDA, 1964).
“Slow” surface runoff defines soils where surface water flows away so slowly that free
water stands on the surface for moderate periods or enters the soil rapidly. Most of the
water passes through the soil, is used by plants, or evaporates. The soils are nearly level
or very gently sloping, or they are steeper but absorb precipitation very rapidly.
“Medium” surface runoff is used to define soils where surface water flows away so
rapidly that free water stands on the surface for only short periods. These soils are nearly
level or gently sloping and absorb precipitation at a moderate rate, or they are steeper but
absorb water rapidly. “Rapid” surface runoff is used to define soils where surface water
flows away so rapidly that the period of concentration is brief and free water does not
stand on the surface. These soils are mainly moderately steep or steep and have moderate
or slow rates of absorption. “Very rapid” is used to define soils where surface water
flows away so rapidly that the period of concentration is very brief and free water does
not stand on the surface. The soils are mainly steep or very steep and absorb precipitation
slowly (USDA, 1995).
The “erosion hazard” is a term developed by the NRCS (USDA, 1995) and is used to
describe the potential for future erosion, inherent in the soil itself, in inadequately
protected areas. The estimated erosion for each erosion classification is based on
estimated annual soil loss in metric tons per hectare. Values were determined using the
Universal Soil Loss Equation assuming bare soil conditions and using rainfall and climate
factors for North Carolina.
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Table 1 Surface runoff and the hazard of water erosion characteristics are presented for
predominant soil series (bolded) and less dominant soils series (non-bolded) in the Fourth
Creek watershed. Less dominant soil series include only series that displayed a high hazard
of water erosion classification (USDA 1995; USDA, 1964).
Soil
Map
Unit Soil Series Surface runoff
Hazard of
water
erosion*
AsB Appling Sandy Loam, 2 to 6 Percent slopes, Eroded Medium to very Moderate
CeB Cecil Sandy Clay Loam, 2 to 6 Percent slopes, Eroded Medium to rapid Severe
CcC Cecil Sandy Loam, 8 To 15 Percent Slopes Medium to rapid Severe
CeC Cecil Sandy Clay Loam, 8 To 15 Percent Slopes, Eroded Rapid Very severe
CfB Cecil-Urban Land complex, 2 to 6 Percent slopes, Eroded Medium to very Severe
CfC Cecil-Urban Land complex, 6 to 10 Percent slopes, Eroded Medium Severe
EnB Enon Fine Sandy Loam, 2 To 6 Percent Slopes Medium Moderate
EnC Enon Fine Sandy Loam, 8 To 15 Percent Slopes Medium to rapid Severe
HsD Hiwassee Loam, 15 To 25 Percent Slopes Rapid Very severe
HwB Hiwassee Loam, 2 to 6 Percent Slopes, Eroded Medium to rapid Severe
HwC Hiwassee Clay Loam, 8 To 15 Percent Slopes, Eroded Rapid Very severe
IrB Iredell loam, 2 to 6 Percent Slopes, Eroded Medium Moderate
LaD Lloyd clay loam, 10 to 15 Percent Slopes, Severely Eroded Rapid Very severe
LbB Lloyd loam, 2 to 6 Percent Slopes, Eroded Medium Moderate
LbC Lloyd loam, 6 to 10 Percent Slopes, Eroded Rapid Severe
MeB Mecklenburg Clay Loam, 2 To 8 Percent Slopes, Eroded Slow or medium Severe
MeC Mecklenburg Clay Loam, 8 To 15 Percent Slopes, Eroded Medium Very severe
PaC Pacolet Sandy Loam, 8 To 15 Percent Slopes Medium to rapid Severe
PaD Pacolet Sandy Loam, 15 To 25 Percent Slopes Rapid Very severe
PaE Pacolet Sandy Loam, 25 To 45 Percent Slopes Rapid Very severe
PcB Pacolet Sandy Clay Loam, 2 To 8 Percent Slopes, Eroded Medium Severe
PcC Pacolet Sandy Clay Loam, 8 To 15 Percent Slopes, Eroded Rapid Very severe
PxC Poindexter-Mocksville Complex, 8 To 15 Percent Slopes Rapid Severe
PxD Poindexter-Mocksville Complex, 15 To 25 Percent Slopes Rapid Very severe
PxE Poindexter-Mocksville Complex, 25 To 45 Percent Slopes Rapid Very severe
RnC Rion-Wedowee Complex, 8 To 15 Percent Slopes Rapid Severe
VnB Vance Sandy Clay Loam, 2 To 8 Percent Slopes, Eroded Medium to rapid Severe
VnC Vance Sandy Clay Loam, 8 To 15 Percent Slopes, Eroded Medium to rapid Very severe
ZeC Zion-Enon Complex, 8 To 15 Percent Slopes Medium Severe
* A description of each classification is presented in Table 2.
Table 2 “Hazard of water erosion” classifications as defined by the NRCS.
Hazard of Water
Erosion Classification Estimated Annual Erosion
None 0 tons per hectare
Slight Less than 2.5 tons per hectare
Moderate 2.5 to 10 tons per hectare
Severe 10 to 25 tons per hectare
Very Severe More than 25 tons per hectare
Fourth Creek Turbidity TMDL November 2003
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1.2 Water Quality Monitoring Program
Water quality monitoring for turbidity, performed by the NCDENR and Yadkin
discharger coalition, has shown occasional violations of the water quality standard (24
out of 135 samples or 18%). As part of this TMDL, chemical and biological assessments
were conducted throughout the Fourth Creek watershed to characterize the impact of
turbidity impairment. Both chemical and biological assessments suggest significant
water quality and habitat impairment and support the inclusion of Fourth Creek on the
Impaired Waters List (2002 Integrated 305(b) and 303(d) Report).
1.2.1 Chemical Monitoring
Fourth Creek was listed as impaired on North Carolina’s 2002 Integrated 303(d) and
305(b) based on monthly data collected between 1992 and 1996 at ambient monitoring
station Q3735000 located at SR 2308 near the town of Elmwood. Two Yadkin-Pee Dee
River Basin Association discharger coalition monitoring stations are located in the Fourth
Creek watershed; one at station Q3735000 and one at an unnamed tributary of Fourth
Creek at SR 2316 (Q3720000). The discharger coalition has been monitoring turbidity at
these locations since 1998. Water quality monitoring performed by NCDENR for
turbidity has shown occasional violations of the water quality standard. Similarly,
monitoring by the Yadkin discharger coalition indicates occasional violations and
supports the decision to list Fourth Creek based on turbidity impairment. Figure 4 shows
the locations of the monitoring stations in the Fourth Creek watershed. Data from each of
these monitoring stations during 1997-2003 are presented in Appendix A.
Fourth Creek Turbidity TMDL November 2003
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Figure 4. Fourth Creek watershed including areas of benthic macroinvertebrate and fish
monitoring, ambient chemical monitoring, and wastewater treatment discharges.
SR 2316
SR 1003
SR 1985
Q3735000
SR 2308
NC0031836
NC0082821
Q3720000
SR 2320
SR 2322
SR 1930
Morrison Ck at SR1907
Yadkin River Basin
Catawba River
Basin
Statesville
Davie County
Iredell County
Rowan County
4 0 4 MilesN
Statesville Boundary
Fourth Creek
DWQ and Discharger Coalition Stations
Fish Community Sampling
Benthic Macroinvertebrate Stations
Fair
Good
Good-Fair
Not Rated
NPDES Discharges
Fourth Ck HUC 14s
Fourth Creek
The turbidity concentrations of the samples collected at the DWQ ambient monitoring
station ranged from 3.7 NTU to 500 NTU with an average of 48 NTU, a median value of
14 NTU, and mode value of 10 NTU. The turbidity concentrations for the samples
collected by the Yadkin discharger coalition at station Q3735000 ranged between 4 and
600 NTU with an average of 51 NTU and a median value of 15 NTU. The turbidity
concentrations for the samples collected by the discharger coalition at station Q3720000
ranged between 4.3 and 880 with an average value of 54 NTU and a median value of 15
NTU.
1.2.2 Biological Monitoring
The DWQ maintains an extensive biological monitoring network of ambient stations. In
the Fourth Creek watershed recent monitoring conducted by DWQs Environmental
Sciences Branch has included assessment for basin wide monitoring plans (1996 and
2001), site specific biological studies below a WWTP point source discharge (1987,
1989, 2001, and 2003), and monitoring for biological stressors (2003). Most recently, in
June and July 2003, an intensive monitoring effort was conducted that included benthic
Fourth Creek Turbidity TMDL November 2003
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macroinvertebrate populations, fish populations, physical and water chemistry
characteristics, and site descriptions and instream and riparian habitats at six locations in
the Fourth Creek watershed. These locations are shown in Figure 4. A summary of fish
and benthic invertebrate results from this study are presented in Table 3.
Table 3 Biological and habitat ratings at the six monitoring stations in the Fourth Creek
watershed.
Site/Assessment
Location (see below
descriptions)
Benthic
macroinvertebrate Fish
Habitat
(1-100 scale)
Overall
rating
1. At SR 1930 Good-Fair Poor 42/41 Fair
2. At SR 2320 Good-Fair Good-Fair 46/34 Good-Fair
3. At SR 2308 Fair Poor 50/46 Fair
4. At ST 1985 Good-Fair Poor 43/41 Fair
5. UT Fourth Creek Not rated --- 72 Not rated
6. Morrison Creek Good-Fair --- 37 Good-Fair
1. Fourth Creek Site No. 1 at SR 1930, north of Interstate 40 and above Statesville.
2. Fourth Creek Site No. 2 at SR 2320, east of Statesville. This site is upstream of the city’s WWTP, but still receives urban runoff.
The SR 2320 site replaced the historically sampled site above the WWTP (SR 2316) The new site is about three miles upstream of the
SR 2316 site.
3. Fourth Creek Site No. 3 at SR 2308, southeast of Statesville and approximately three miles below the city’s WWTP.
4. Fourth Creek Site No. 4 at SR 1985 in Rowan County, east of Statesville, approximately 15 miles below the city’s WWTP, and one
mile above its confluence with Third Creek. This site is intended to measure any potential recovery from the WWTP discharges and
urban runoff from Statesville.
5. UT Fourth Creek at SR 2322. Most small streams draining the urbanized area were too small to sample. The largest of the
tributaries (UT Fourth Creek at SR 2322) drained a highly urbanized section of Statesville.
6. Morrison Creek at SR 1907, above Statesville.
Most notable in this study was the widespread finding of stream bank erosion and habitat
degradation. Instream and riparian habitats at all sites except the UT Fourth Creek were
of low quality; the habitat scores were generally less than 50 (1 and 100 scale). Instream
habitats were identified as severely degraded and were characterized as having bottom
substrates of primarily sand, shallow and sand-filled pools, a general lack of gravel or
cobble riffles, and very unstable, easily eroded banks. At all locations along Fourth Creek
there remained repercussions of extremely high 2003 winter flows, including large
woody debris and obstructions, sloughing and exposed banks with minimal stabilizing
vegetation, recent bank erosion, and tires, plastics, lumber, and other domestic items in
the stream and along the shoreline. Bank erosion was noted as a large contributor of
sediment and habitat degradation. The study concludes by identifying a number of
sources (including poor landuse practices, urbanization, and wastewater treatment
discharges), all contributors to hydromodification that, in connection with highly
erodable soils, has resulted in the current state of habitat degradation.
While this biological information is not used directly in calculation the TMDL, it will be
a primary information source when implementing the load and wasteload reductions set
forward in this TMDL.
1.3 Water Quality Target
Turbidity is a unit of measurement quantifying the degree to which light traveling
through a water column is scattered by the suspended organic and inorganic particles.
The scattering of light increases with a greater suspended load. Turbidity is commonly
Fourth Creek Turbidity TMDL November 2003
10
measured in Nephelometric Turbidity Units (NTU), but may also be measured in Jackson
Turbidity Units (JTU).
The NC DWQ has classified Fourth Creek and its tributaries as Class C waters. Class C
waters are defined as “Waters protected for secondary recreation, fishing, wildlife, fish
and aquatic life propagation and survival, agriculture and other uses suitable for Class C.
Secondary recreation includes wading, boating, and other uses involving human body
contact with water where such activities take place in an infrequent, unorganized, or
incidental manner.” The North Carolina fresh water quality standard for turbidity in
Class C waters (T15A: NCAC 2B.0211 (3)k) states:
The turbidity in the receiving water shall not exceed 50 Nephelometric Turbidity
Units (NTU) in streams not designated as trout waters and 10 NTU in streams,
lakes or reservoirs designated as trout waters; for lakes and reservoirs not
designated as trout waters, the turbidity shall not exceed 25 NTU; if turbidity
exceeds these levels due to natural background conditions, the existing turbidity
level cannot be increased. Compliance with this turbidity standard can be met
when land management activities employ Best Management Practices (BMPs) [as
defined by Rule .0202 of this Section] recommended by the Designated Nonpoint
Source Agency [as defined by Rule .0202 of this Section]. BMPs must be in full
compliance with all specifications governing the proper design, installation,
operation and maintenance of such BMPs;
The in-stream numeric target is the restoration objective that is expected to be reached by
implementing the specified load reductions in this TMDL. The target allows for
evaluation of progress toward the goal of reaching water quality standards for the
impaired stream by comparing the in-stream data to the target. In the Fourth Creek
watershed, the applicable water quality target is the 50 NTU standard.
2.0 Source Assessment
A source assessment is used to identify and characterize the known and suspected sources
of turbidity in the Fourth Creek watershed. This section outlines the assessment
completed for the purpose of developing this TMDL.
2.1 Assessment of Point Sources
Two categories are included under this discussion; NPDES-regulated municipal and
industrial wastewater treatment facilities and NPDES general permitted facilities.
2.1.1 NPDES-Regulated Municipal and Industrial Wastewater Treatment
Facilities
Discharges from wastewater treatment facilities may contribute sediment to receiving
waters as total suspended solids (TSS) and/or turbidity. Municipal treatment plants and
industrial treatment plants are required to meet surface water quality criteria for turbidity
in their effluent. Since these facilities are routinely achieving surface water quality
criteria, this TMDL will not impose additional limits to current practices or existing
effluent limits for POTWs and industrial treatment plants. When effluent turbidity
Fourth Creek Turbidity TMDL November 2003
11
concentrations exceed surface water quality criteria, and result in permit violations,
action will be taken through the NPDES unit of North Carolina’s Division of Water
Quality.
Currently, there are two NPDES permitted wastewater treatment plant dischargers
located in the Fourth Creek watershed. The Statesville WWTP (NC0031836) has a 4.0
MGD flow limit and a TSS effluent limit of 30 mg/l on a monthly average and 45 mg/L
on a weekly average. Southern States Cooperative (NC0082821) has a 0.114 MGD flow
limit and a TSS effluent limit of 30 mg/l on a monthly average and 45 mg/L as a daily
maximum. Average monthly TSS values for both facilities are available in Appendix B.
2.1.2 NPDES General Permits
Twenty-six general permitted facilities are located in the Fourth Creek watershed. A list
of these facilities is presented in Appendix C. General permitted facilities are not subject
to effluent TSS or turbidity limitations nor are they required to monitor for TSS or
turbidity. Thus, this TMDL will not allocate a load reduction for general permitted
facilities.
A number of manufacturing facilities are located in the Fourth Creek watershed. Included
are operations involving granite mining, metal processing, paper milling, textile,
paperboard and rubber processing, food and tobacco processing, paint processing, auto
junk yards, landfills, asphalt paving, furniture production, and homebuilding
construction. Sediment loading from NPDES-regulated construction activities are
considered point sources of sediments to surface waters. Discharges from regulated
mining activities may also contribute sediment to surface waters as TSS. Discharges from
active mines may result from dewatering operations and/or in response to storm events.
Discharges from permitted inactive mines are only in response to storm events. Inactive
sites with successful surface reclamation contribute relatively little solids loading.
Sediment loading in the Fourth Creek watershed that is a result of mining activity is not
specifically addressed as part of this TMDL.
2.2 Assessment of Nonpoint and Stormwater Sources
Nonpoint and stormwater sources include various erosional processes, including
sheetwash, gully and rill erosion, wind, landslides, dry ravel, and human excavation that
contribute sediment during storm or runoff events. Sediments are also often produced as a
result of stream channel and bank erosion and channel disturbance (EPA, 1999).
Nonpoint sources account for the vast majority of sediment loading to surface waters. A
few of these sources include:
Natural erosion occurring form the weathering of soils, rocks, and uncultivated
land; geological abrasion; and other natural phenomena.
Erosion from agricultural activities. This erosion can be due to the large land area
involved and the land-disturbing effects of cultivation. Grazing livestock can
Fourth Creek Turbidity TMDL November 2003
12
leave areas of ground with little vegetative cover. Unconfined animals with direct
access to streams can cause streambank damage and erosion.
Urban sources include erosion from bare soil areas under construction and
washoff of accumulated street dust and litter from impervious surfaces.
Erosion from unpaved roadways can be a significant source of sediment to rivers
and streams. Exposed soils, high runoff velocities and volumes and poor road
compaction all increase the potential for erosion.
Runoff from active or abandoned mines may be a significant source of solids
loading. Mining activities typically involve removal of vegetation, displacement
of soils and other significant land disturbing activities.
Soil erosion from forested land that occurs during timber harvesting and
reforestation activities. Timber harvesting includes the layout of access roads, log
decks, and skid trails; the construction and stabilization of these areas; and the
cutting of trees. Established forest areas produce very little erosion.
Streambank and streambed erosion processes often contribute a significant
portion of the overall sediment budget. The consequence of increased streambank
erosion is both water quality degradation as well as increased stream channel
instability and accelerated sediment yields. Streambank erosion can be traced to
two major factors: stream bank characteristics (erodibility potential) and
hydraulic/gravitational forces (Rosgen, online). The predominant processes of
stream bank erosion include: surface erosion, mass failure (planar and rotational),
fluvial entrainment (particle detachment by flowing water, generally at the bank
toe), freeze-thaw, dry ravel, ice scour, liquifaction/collapse, positive pore water
pressure, both saturated and unsaturated failures and soil piping.
2.2.1 Stormwater Discharges in the Fourth Creek Basin
Urban runoff can contribute significant amounts of turbidity, however, much of this
runoff is designed to be regulated under the Storm Water Phase II Final Rule (EPA,
2000). Amendments were made to the Clean Water Act in 1990 and most recently in
1999 pertaining to permit requirements for stormwater dischargers associated with
industrial activities and municipal separate storm sewer systems (MS4s). MS4s can
discharge sediment to waterbodies in response to storm events through road drainage
systems, curb and gutter systems, ditches, and storm drains. This rule applies to a cities or
counties which own or operate a municipal separate storm sewer system (MS4). As a
result of the Phase II Rule, MS4 owners are required to obtain a National Point Source
Discharge Elimination System (NPDES) permit for their stormwater discharges to
surface waters. Currently, the City of Statesville does not fall under the Phase II Rule,
however, it is clear that Statesville causes and contributes to impairment in Fourth Creek
and should initiate a storm water management program.
Fourth Creek Turbidity TMDL November 2003
13
2.2.2 Load Duration Curve
When streamflow gage information is available, a load duration curve (LDC) is useful in
identifying and differentiating between storm-driven and steady-input sources. Turbidity
is measured in NTUs, not a concentration, so another parameter that is measured as a
concentration must be used to represent turbidity loadings in the watershed. To
accomplish this, correlation coefficients were determined for all parameters at the Fourth
Creek ambient station # Q3735000. Highest correlations for turbidity are shown below in
Table 4.
Table 4 Correlation coefficients for turbidity at DWQ ambient station # Q3735000.
Parameter and Units Correlation Coefficient
Total Precipitation (inches per day) 0.85
Total Suspended Solids (mg/L) 0.92
Total Chromium (ug/L as Cr) 0.67
Total Copper (ug/L as Cu) 0.83
Total Iron (ug/L as Fe) 0.88
Total Nickel (ug/L as Ni) 0.61
Total Zinc (ug/L as Zn) 0.60
Total Aluminum (ug/L as Al) 0.84
Correlation coefficients were determined using the below formula:
( )( )
yx
yi
n
i
xi
xy
yxn
σσ
µµ
ρ ⋅
−−
=
∑
=1
1
where:
11≤≤−xyρ
Of the available parameters, the strongest correlation is present between turbidity and
TSS. High correlations between turbidity and precipitation, and turbidity and iron support
the turbidity –TSS correlation and suggest a strong relationship between storm driven
TSS inputs that correspond to elevated turbidity measurements. Given this information, a
linear regression was developed between turbidity and TSS to allow for the use of TSS
values in developing a LDC. This correlation is shown in Figure 5. An example LDC
using the 50 NTU criterion is presented in Figure 6. Steps used to develop the LDC are
presented in Appendix D.
Fourth Creek Turbidity TMDL November 2003
14
Figure 5. Linear regression for TSS-Turbidity at Fourth Creek at SR 2308 near Elmwood,
NC (USGS station #02120780) using data collected during years 1997-2003.
y = 1.3408x - 1.0079
R2 = 0.8435
0
50
100
150
200
250
300
350
400
450
0 50 100 150 200 250 300 350
Turbidity (NTU)
TS
S
(
m
g
/
L
)
Figure 6. Example load duration curve.
1.0E+02
1.0E+03
1.0E+04
1.0E+05
1.0E+06
1.0E+07
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Percent of Days Flow is Exceeded
TS
S
(
l
b
s
/
d
a
Area outside
technically or
economically
feasible
management
0-10%
NPS contributions
from runoff
0-85%
Contributions
from steady input
85-100%
Load Duration Curve using 66 mg TSS/L; the TSS
equivelant to the Turbidity standard of 50 NTU.
Values that plot below the LDC represent samples below the concentration threshold
whereas values that plot above represent samples that exceed the concentration threshold.
Loads that plot above the curve and in the region between 85 and 100 percent of days in
Fourth Creek Turbidity TMDL November 2003
15
which flow is exceeded indicate a steady-input source contribution. Loads that plot in the
region between 10 and 70 percent suggest the presence of storm-driven source
contributions. A combination of both storm-driven and steady-input sources occurs in
the transition zone between 70 and 85 percent. Loads that plot above 99 percent or below
10 percent represent values occurring during either extreme low or high flows conditions
and are thus considered to be outside the region of technically and economically feasible
management.
2.3 Data Sources
The NCDENR’s Geographic Information System (GIS) was used extensively to describe
the Fourth Creek watershed characteristics. The following is general information
regarding the data used to describe the watershed:
• Ambient chemical monitoring locations: NC DENR Div of Water Quality,
Water Quality Section, 9/30/2000, Ambient Water Quality Monitoring Sites: NC
DENR Div of Water Quality, Water Quality Section, Raleigh, North Carolina.
• Biological monitoring locations: NC DENR Clean Water Management Trust
Fund, NC DENR - Div. of Water Quality, Biological Assessment Unit,
11/15/2000, Benthic monitoring results: NC DENR - Div. of Water Quality,
Biological Assessment Unit, Raleigh, North Carolina.
• City of Statesville Boundary: NC Department of Transportation-GIS Unit,
7/17/2000, Municipal Boundaries - Powell Bill 1999: NC Department of
Transportation, Raleigh, North Carolina.
• County boundaries: information NC Center for Geographic Information &
Analysis, 12/01/1998, Boundaries - County (1:100,000): NC Center for
Geographic Information & Analysis, Raleigh, North Carolina.
• Detailed stream coverage: North Carolina Center for Geographic Information
and Analysis, 4/19/2001, Hydrography (1:24,000): North Carolina Center for
Geographic Information and Analysis, Raleigh, NC.
• Hydrologic Units: USDA, Natural Resources Conservation Service, 12/01/1998,
Hydrologic Units - North Carolina River Basins: USDA, Natural Resources
Conservation Service, Raleigh, North Carolina..
• Land use/Land cover information: Earth Satellite Corporation (EarthSat),
6/12/1998, Statewide Land Cover - 1996: EarthSat, Raleigh, North Carolina.
• NPDES Permitted Facilities: NC DENR Division of Water Quality, Planning
Branch, 10/11/2000, National Pollutant Discharge Elimination System Sites: NC
DENR Division of Water Quality, Planning Branch, Raleigh, North Carolina.
• Roads: NC Department of Transportation - GIS Unit, 9/21/1999, Transportation -
NCDOT Roads (1:24,000): NC Department of Transportation, Raleigh, NC.
• Stream Gaging Stations: NC DENR-Division of Water Resources, 12/01/1998,
Stream Gaging Stations: NC DENR-Division of Water Resources, Raleigh, North
Carolina.
• Streamflow gage data was obtained online from the United States Geological
Survey (USGS) at: http://nc.water.usgs.gov/ .
Fourth Creek Turbidity TMDL November 2003
16
3.0 Technical Approach
A LDC and mass-balance approach was chosen to calculate this TMDL for turbidity in
Fourth Creek (ASIWPCA, 2002; Kansas, 2002; Sheely, 2002). The load duration curve
approach is advantageous because it is applicable in the initial phases of source
identification, in water quality assessment to quantifying the magnitude of exceedence
during critical conditions, and in implementation planning. Given this, the LDC/mass
balance approach was used to identify source types, specify the assimilative capacity of
the stream, and quantify the necessary load reduction needed to meet water quality
standards
3.1 TMDL Endpoints
Given that the turbidity standard is expressed as NTU, a correlation between TSS and
turbidity was necessary in applying the LDC method. A discussion surrounding the
selection of TSS as a surrogate for turbidity is presented in Section 2.2.2. As discussed, a
correlation of 0.92 exists between the TSS – turbidity data, and in using a linear
regression, the following relationship is observed:
TSS = (1.3408 * Turbidity) –1.0079
R2 = 0.84
Thus, the Surface Water Quality Standard turbidity target of 50 NTU in Class C waters
correlates to a TSS value of 66.0 mg/L. The results from this regression are presented in
Figure 5.
3.2 Load Duration Curve
A load duration curve is based on comparison of the frequency of a given flow even with
its associated water quality load. As previously discussed, flow gage information is not
available in the Fourth Creek watershed, thus, daily flow data (during April 1979 through
August 2003) from a nearby USGS Station #02120780, Second Creek near Barber, was
used to establish the historic flow regimes and define ranges for the high, typical, and low
flow conditions. Flows at the Fourth Creek ambient station at SR 2308 were estimated
based on a drainage area ratio between USGS station #02120780 and the watershed area
upstream of SR 2308. Flows were also adjusted to account for point sources in each
watershed by subtracting the average point source flow in Second Ck and adding the
flows from the effluent of the Fourth Ck WWTP (NC0031836) and the Southern States
Cooperative (NC0082821). Table 5 presents flow statistics for station #02120780
obtained from the USGS and LDC analysis.
Table 5 Flow statistics for USGS gage station #02120780 during years 1979-2003.
Parameter Value
Drainage Area 118 mi2
Average flow 104 cfs
Minimum flow 0.5 cfs
Maximum flow 5,280 cfs
High Flow Range (> 10% exceed) > 1,050 cfs
Nonpoint Source Contributions from runoff (10-85%) 11- 1,050 cfs
Fourth Creek Turbidity TMDL November 2003
17
Parameter Value
Low Flow Range (95-100%) < 4.6 cfs
Using the drainage-area and point source adjusted flow values, flow duration graphs were
developed for the Fourth Creek ambient station. Monitoring data was then matched up
with the flow duration ranking based on the collection date. Figure 7 shows TSS data as a
function of estimated flow duration at the Fourth Creek ambient station. As shown in
Figure 7, the majority of Surface Water Quality violations occur under low percent
exceedence flows and are likely the result of storm events. Infrequently, exceedences also
occur under mid-range and low flow conditions.
Figure 7. Fourth Creek at USGS station 02120780 (Fourth Creek at SR 2308 near
Elmwood); Flow Duration and TSS Concentration during years 1997-2003.
0
200
400
600
800
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Percent of Days Flow is Exceeded
Discharger Coalition Data - TSS estimated
DWQ Data - TSS measured
DWQ Data - TSS data estimated
Instantaneous Standard TSS equivelant (66 mg/L)
High flows
outside feasible mgmt
Nonpoint Source contributions from runoff
Contributions
under
steady input
3.3 Assimilative Capacity
The assimilative capacity is the maximum level of pollutant allowable while achieving
the water quality goal. As discussed in section 2.2.2, TSS was selected as a surrogate for
turbidity in this TMDL. To determine the TSS assimilative capacity, the TSS
concentration equivalent to the turbidity standard of 50 NTU (66 mg TSS/L) was
multiplied by the full range of measured flow values. The assimilative capacity is shown
graphically in the form of a blue line in Figure 8.
Fourth Creek Turbidity TMDL November 2003
18
Figure 8. Fourth Creek at USGS station 02120780 (Fourth Creek at SR 2308 near
Elmwood); Load Duration Curve using water quality data from years 1997-2003.
1.E+02
1.E+03
1.E+04
1.E+05
1.E+06
1.E+07
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Percent of Days Flow is Exceeded
SWQS with MOS = 45 NTU or 59.3 mg/L TSS
Discharger Coalition Data - TSS estimated
DWQ Data - TSS measured
DWQ Data - TSS data estimated
4.0 TMDL Calculation
A Total Maximum Daily Load (TMDL) represents the assimilative or carrying capacity
of a waterbody, taking into consideration point and nonpoint sources of pollutants of
concern, natural background and surface water withdrawals. A TMDL quantifies the
amount of a pollutant a water body can assimilate without violating a state’s water quality
standards (in our case, Class C freshwaters) and allocates that load capacity to known
point and nonpoint sources in the form of wasteload allocations (WLAs), load allocations
(LAs). In addition, the TMDL must include a margin of safety (MOS), either implicitly
or explicitly, that accounts for the uncertainty in the relationship between pollutant loads
and the quality of the receiving waterbody. This definition is expressed by the following
equation:
TMDL = WLAs + LAs + MOS
A TMDL is developed as a mechanism for identifying all the contributors to surface
water quality impacts and setting goals for load reductions for pollutants of concern as
necessary to meet the SWQS. The Code of Federal Regulations (40 CFR §130.2(1))
states that TMDLs can be expressed in terms of mass per time, toxicity, or other
appropriate measures. This TMDL will be expressed in terms of mass per time and a
percent reduction that is calculated based on estimated stream flow and both estimated
Fourth Creek Turbidity TMDL November 2003
19
and measured instream TSS concentrations. At total of 135 TSS values were used in this
TMDL analysis; 74 collected during 1997-2003 by the DWQ and 61 collected by the
Yadkin River Discharger Coalition. Of the 74 DWQ TSS values, 53 are actual
measurements and 21 are estimated based on the turbidity-TSS linear regression. All of
the 61 TSS values in the Discharger Coalition dataset are estimated based on the
turbidity-TSS linear regression.
4.1 TMDL Endpoints
TMDL endpoints represent the instream water quality targets used in quantifying TMDLs
and their individual components. As discussed in Section 3, turbidity as a measure is not
applicable to the estimation of loading to a stream. TSS was selected as a surrogate
measure for turbidity. Based on the regression analysis, a TSS limit of 66 mg/L was
determined to be equivalent to a turbidity measure of 50 NTU. As will be discussed in
Section 4.4, a 10% explicit margin of safety was applied to the endpoint and resulted in a
reduction of the target value from 50 NTU to 45 NTU (66 mg TSS/L to 59.3 mg TSS/L).
4.2 Critical Conditions
Elevated turbidity concentrations occur predominantly during high flow conditions.
However, five of the measurements over the 50 NTU standard were taken under flows
that occur no less than 50 % of the time.
4.3 Seasonal Variation
Exceedences to the 50 NTU turbidity standard during 1997-2003 have occurred during all
months of the year with the exception of December. During 1997-2003, the majority of
violations occurred during the late winter and spring months. Table 6 shows the number
of violations in each month during the 1997-2003 period. Seasonal variation is
considered in this TMDL by applying the load reduction to all seasons.
Table 6 Number of violations to the 50 NTU standard for each month during the 1997-2003
period.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Violations (#) 3 4 4 5 2 2 2 1 1 1 1 0
4.4 Margin of Safety
A Margin of Safety (MOS) is provided to account for “lack of knowledge concerning the
relationship between effluent limitations and water quality” (40 CFR 130.7(c)). The MOS
may be incorporated into a TMDL either implicitly, through the use of conservative
assumptions to develop the allocations, or explicitly through a reduction in the TMDL
target. For this TMDL, an explicit margin of safety was incorporated in the analysis by
setting the TMDL target at 45 NTU, or equivalent 59.3 mg TSS/L, which is 10% lower
than the water quality target of 50 NTU or equivalent 66 mg TSS/L.
4.5 Reserve Capacity
Reserve capacity is an optional means of reserving a portion of the loading capacity to
allow for future growth. Reserve capacities are not included at this time. The loading
capacity of each stream is expressed as a function of the current load (Section 4.0), and
Fourth Creek Turbidity TMDL November 2003
20
both WLAs and LAs are expressed as reductions for the entire Fourth Creek watershed.
Therefore, the reductions from current levels, outlined in this TMDL, must be attained in
consideration of any new sources that may accompany future development. Strategies
for source reduction will apply equally to new development as to existing development.
4.6 TMDL Calculation
As presented in Section 3.0, loading curves were used to identify the target and reduction
necessary for turbidity in Fourth Creek. The load duration curve presents a maximum
allowable concentration of 59.3 mg TSS/L (value includes a 10% MOS and is equivalent
to 45 NTU) and identifies a maximum allowable load under any given flow experienced
in Fourth Creek. The TMDL calculation focuses on measurements observed under a
range of normal or expected flow conditions and excludes data collected under extremely
high flows (occurring less than 10% of the time) and low flows (occurring more than
95% of the time). While data obtained under extreme flow conditions are not used to
develop the TMDL, they may be appropriate for decision making during TMDL
implementation.
Data collected under flows that occur between 10% and 95% of the time that exceeded
either the 50 NTU or 66 mg TSS/L were used to calculate the TMDL. An exponential
regression line was fit to these values and was used to estimate the corresponding TSS
load at each percent between 10% and 95%. Allowable loading was also calculated at
each percentage between 10% and 95% based on the MOS-adjusted target concentration.
An overall load reduction of 47% was determined by calculating the average load
reduction and comparing it to the average target load at all flows between 10% and 95%.
The target and regression curves are shown in Figure 9. The average existing and target
loadings estimated at each flow interval are presented in Appendix E and summarized in
Table 7. The average existing TSS load of 19,703 lbs TSS/day, identified in Table 7, is
equivalent to an average turbidity value of 75.7 NTU.
Fourth Creek Turbidity TMDL November 2003
21
Figure 9. Fourth Creek at USGS station 02120780 (Fourth Creek at SR 2308 near
Elmwood); Load Duration Curve with Regression line using water quality from years 1997-
2003.
y = 75087e-3.0737x
1.E+02
1.E+03
1.E+04
1.E+05
1.E+06
1.E+07
0% 10% 20% 30% 40% 50% 60% 70% 80% 90%
Percent of Days Flow is Exceeded
SWQS with MOS = 45 NTU or 59.3 mg/L TSS
Discharger Coalition Data - TSS estimated
DWQ Data - TSS measured
DWQ Data - TSS data estimated
Exponential regression line to values between 10 and
95% and above the TSS equivelant (59.3 mg TSS/L)
instantaneous turbidity SWQS with MOS (45 NTU).
Table 7 Unallocated TMDL load and associated percent reduction
Target
Concentration with
MOS (mg/L TSS)
Existing Load
(Average, lbs/day)
Target Load
(Average, lbs/day)
Reduction
Required (Percent)
59.3 19,703 10,519 47%
4.7 Wasteload and Load Allocations
Additional analysis is required to address the TMDL reduction by identifying point and
nonpoint contributors of turbidity and calculating wasteload and load allocations. WLAs
are hereby established for all NPDES-regulated point sources, while LAs are established
for all stormwater sources that are not subject to NPDES regulation, and for all nonpoint
sources.
As previously discussed, two NPDES-permitted facilities are located in the Fourth Creek
watershed. Both facilities are subject to monthly TSS effluent limitations of 30 mg
TSS/L. As such, this TMDL will not result in changes to these limits. For the purposes of
this TMDL, a wasteload allocation will be apportioned based on the maximum permitted
load allowable at each NPDES facility.
Fourth Creek Turbidity TMDL November 2003
22
To apportion the TMDL to WLAs and LAs, additional analysis beyond the LDC method
is necessary. As earlier noted, Fourth Creek is primarily composed of agricultural and
forested land uses. Given this, urban stormwater flows from the city of Statesville are
known to have a significant impact on instream turbidity concentrations. Percent land use
in association with relative loading rates associated with that land use have been applied
previously in identifying wasteload and load allocations (NCDWQ, 2003) and a similar
method will be used to determine appropriate WLAs and LAs for this TMDL.
A number of studies have attempted to quantify pollutant loading relative to land use.
One such study, conducted by the USGS, estimated pollutant loads from nine
subwatersheds in the Charlotte area (USGS, 1999). Streamflow and water-quality data
were collected at nine sites in the city of Charlotte and Mecklenburg County, North
Carolina, during 1993-97. Six of the basins drained areas having relatively homogeneous
land use and were less than 0.3 square mile in size; the other three basins had mixed land
use. Sediment yields at the nine sites ranged from 77 tons per square mile per year in a
residential basin to 4,700 tons per square mile per year at the developing basin. The
application of the USGS results of this report is appropriate given the close proximity of
the two study sites and the common landuses involved in each. Relative pollutant
contributions from different landuses in the USGS report are presented in Appendix F.
For this TMDL, landuse-specific sediment loading estimates from the USGS (1999)
study were categorized as either urban or rural, and the relative percent TSS contribution
was determined for both land use types. The resulting relative percent TSS contributions
were combined with the Fourth Creek landuse distribution to estimate the overall relative
loading ratios for urban and rural areas. These results are presented in Table 8. The city
of Statesville constitutes nearly all of the urban land use in the Fourth Creek watershed.
While the boundary of the city of Statesville constitutes over 16.4% of the Fourth Creek
watershed, the 1993-94 land use/land cover classification identifies 6.9% of the total area
as “urban” because of the presence of parks, vegetation, and other mixed land uses in the
boundary of Statesville. For the purposes of this TMDL, the Statesville boundary
(16.4%) was used to calculate the urban area and the remainder of the watershed is
characterized as rural.
Table 8 Relative Pollutant concentrations using USGS (1999) study and Fourth Creek
landuse.
Landuse
TSS load
(tons/mi2/yr)
USGS (1999) study
Landuse Percent
from Fourth Creek
TSS Loading Ratio
for Fourth Creek
Urban 1071 16.4% 11%
Rural 1688 83.6% 89%
Wasteload allocations for NC0031836 and NC0082821 are based on permitted flow and
effluent TSS limits and do not result in additional reductions for these facilities. Load
allocations for urban and rural landuses were determined by first subtracting the WWTP
Fourth Creek Turbidity TMDL November 2003
23
point source loads (combined 1030 lbs/day) from the overall TMDL load (10,519
lbs/day) and multiplying the resulting TMDL load (9,489 lbs/day) by the associated TSS
loading ratio (11% for urban, 89% for rural). The resulting load and wasteload allocations
are presented in Table 9.
Table 9 Fourth Creek TMDL Wasteload and Load Allocations for Turbidity expressed as
lbs/day TSS.
TMDL Allocations TSS Load (lbs/day)
Existing 19,703
WLA - NC0031836 (4 MGD, 30 mg TSS/L limit) 1,001
WLA - NC0082821 (0.114 MGD, 30 mg TSS/L limit) 29
Sum of WLAs 1,030
LA – Urban 1,044
LA – Rural (Non-Urban) 8,445
Sum of LAs 9,489
MOS Explicit 10%
TMDL 10,519
TMDL – Percent Reduction Required 47%
5.0 Follow – up Monitoring
Turbidity monitoring will continue on a monthly interval at the ambient monitoring
station at SR2308 near Elmwood and will allow for the evaluation of progress towards
the goal of reaching water quality standards. Short-term flow monitoring at the Fourth
Creek at SR2308 near Elmwood is currently underway for the purpose of increasing the
accuracy of estimating flows in Fourth Creek to assist in verifying an appropriate near-by
station for future flow estimation. Additional monitoring could focus on identifying
critical areas of streambank erosion and turbidity source assessment in the watershed.
This would further aid in the evaluation of the progress towards meeting the water quality
standard.
6.0 Implementation
Turbidity impairments in the Fourth Creek watershed are primarily due to excessive
stream channel and bank erosion. This erosion is, in part, a result of higher flows and
volumes associated with increased urbanization and impervious surface in the Fourth
Creek watershed. Enforcement of stormwater BMP requirements for construction sites,
education on farm practices, and consideration of urban stormwater controls for sediment
are potential management options for improving turbidity levels. Other TSS sources
include runoff from disturbed landuses, such as agriculture and construction areas where
conversion from rural to urban uses is occurring. While stormwater controls are required
on construction sites, significant loadings can occur due to initial periods of land
Fourth Creek Turbidity TMDL November 2003
24
disturbance before controls are in place or during high rainfall periods during which the
controls are inadequate. North Carolina Phase II rules require development,
implementation, and enforcement of an erosion and sediment control program for
construction activities that disturb one or more acres of land. In addition, Phase II rules
require the development, implementation, and enforcement of a program to address
discharges of post-construction storm water runoff from new development and
redevelopment areas.
Implementation of conservation management plans and best management practices are
the best means of controlling agricultural sources of suspended solids. Several programs
are available to assist farmers in the development and implementation of conservation
management plans and best management practices. The Natural Resource Conservation
Service is the primary source of assistance for landowners in the development of resource
management pertaining to soil conservation, water quality improvement, wildlife habitat
enhancement, and irrigation water management. The USDA Farm Services Agency
performs most of the funding assistance. All agricultural technical assistance is
coordinated through the locally led Naturally Resource Conservation Service offices (Soil
Conservation Districts). The funding programs include:
• The Environmental Quality Incentive Program (EQIP) is designed to provide
technical, financial, and educational assistance to farmers/producers for
conservation practices that address natural resource concerns, such as water
quality. Practices under this program include integrated crop management,
grazing land management, well sealing, erosion control systems, agri-chemical
handling facilities, vegetative filter strips/riparian buffers, animal waste
management facilities and irrigation systems.
• The Conservation Reserve Program (CRP) is designed to provide technical and
financial assistance to farmers/producers to address the agricultural impacts on
water quality and to maintain and improve wildlife habitat. CRP practices include
the establishment of filter strips, riparian buffers and permanent wildlife habitats.
This program provides the basis for the Conservation Reserve Enhancement
Program (CREP). In 1999 The North Carolina DENR Departments of
Environmental Protection and Agriculture, in partnership with Commodity Credit
Corporation (CCC), submitted a proposal to the USDA to offer financial
incentives for agricultural landowners to voluntarily implement conservation
practices on agricultural lands through CREP. The goals for this program are to
significantly reduce the amount of nutrients entering estuaries from agricultural
sources through a voluntary, incentive-based program; to assist North Carolina in
achieving the nutrient reduction goals for agriculture in the area; to significantly
reduce the amount of sediment entering water courses; to enhance habitat for a
range of threatened and endangered species dependent on riparian areas; and to
decrease excess pulses of freshwater in primary nursery areas. NC CREP will be
part of the USDA’s Conservation Reserve Program (CRP). The enrollment of
farmland into CREP in North Carolina is expected to improve stream health
Fourth Creek Turbidity TMDL November 2003
25
through the installation of water quality conservation practices on North Carolina
farmland.
• The Soil & Water Conservation Cost-Sharing Program is available to
participants in a Farmland Preservation Program pursuant to the Agriculture
Retention and Development Act. A Farmland Preservation Program (FPP) means
any voluntary FPP or municipally approved FPP, the duration of which is at least
8 years, which has as its principal purpose as long-term preservation of significant
masses of reasonably contiguous agricultural land within agricultural
development areas. The maintenance and support of increased agricultural
production must be the first priority use of the land. Eligible practices include
erosion control, animal waste control facilities, and water management practices.
Cost sharing is provided for up to 50% of the cost to establish eligible practices.
Management Strategies
Management measures are “economically achievable measures for the control of the
addition of pollutants from existing and new categories and classes of nonpoint and
stormwater sources of pollution, which reflect the greatest degree of pollutant reduction
achievable through the application of the best available nonpoint and stormwater source
pollution control practices, technologies, processes, siting criteria, operating methods, or
other alternatives” (USEPA, 1993). Development of effective management measures
depends on accurate source assessment. A few projects recently completed, underway
and planned are identified below.
The Iredell Soil and Water Conservation District (SWCD), located in Statesville, Iredell
County, has been active in assessing issues related to sediment loading in Fourth Creek.
In 1999 the SWCD conducted a sediment survey to identify sediment sources and
provide a description of the landuses and sediment BMPs adjacent to Fourth Ck and in
the watershed (Soil and Water Conservation District, 1999). An action plan was also
developed and includes recommendations, goals, and estimates of associated financial
expenditures needed for remediation to problems in-stream, in adjacent land areas, and in
the watershed as a whole. Lastly, barriers and limiting factors toward achieving the
recommended goals are identified in the action plan. This report is provided in Appendix
G.
The Division of Water Quality, in cooperation with the Iredell SWCD, and USDA,
NRCS in Statesville, NC, is supporting a Fourth Creek fecal coliform TMDL
implementation project aimed at meeting the objectives for fecal coliform reduction as
outlined in the 2001 TMDL report on fecal coliform in Fourth Creek (DWQ, 2001). The
main goal of this project is to reduce fecal coliform loading to Fourth Creek from
agricultural sources by providing alternative water sources and excluding grazing cattle
from the stream. While not specifically addressing turbidity or TSS, management
measures taken to reduce bacterial loads will likely have the direct effect of reducing
sediment erosion and resuspension. A few of such actions in the implementation plan
include: construction of fencing along 30,000 feet of stream bank, reestablishing 2,000
Fourth Creek Turbidity TMDL November 2003
26
feet of riparian vegetation in the buffer zone to reduce erosion, 2 acres of tree planting, 3
acres of critical area seeding/treatment, and construction of 12 stream crossings.
Fourth Creek and the lower South Yadkin River watersheds (HUCs 3040102030010 and
3040102030020) are two of 55 watersheds in the Yadkin-Pee Dee River basin that have
been identified by the NC Wetlands Restoration Program (NCWRP) as areas with the
greatest need and opportunity for stream and wetland restoration efforts. This watershed
will be given higher priority than a non-targeted watershed for the implementation of
NCWRP restoration projects.
7.0 Public Participation
The City of Statesville in Iredell County and Rowan County has been notified of the
Fourth Creek turbidity TMDL. The county extension service and soil and water
conservation districts will be involved in the implementation portion of the TMDL. A
public meeting will be held in the watershed on March 26, 2004 to discuss the TMDL.
The TMDL has been publicly noticed and comments on the TMDL will be accepted over
a period of at least thirty days.
8.0 Additional Information
Further information concerning North Carolina’s TMDL program can be found on the
Internet at the Division of Water Quality website:
http://h2o.enr.state.nc.us/tmdl/index.htm
Technical questions regarding this TMDL should be directed to the following members
of the DWQ Modeling/TMDL Unit:
Brian Jacobson, Modeler
e-mail: Brian.Jacobson@ncmail.net
Fourth Creek Turbidity TMDL November 2003
27
References
ASIWPCA TMDL, “Brown Bag,” Conference Call on Load Duration Curve
Methodology, June 12, 2002.
Cleland, B.R. 2002. TMDL Development from the “Bottom Up” – Part II: Using load
duration curves to connect the pieces. Proceedings from the WEF National TMDL
Science and Policy 2002 Conference.
Earth Satellite Corporation (EarthSat), 19980612, Statewide Land Cover - 1996:
EarthSat, Raleigh, North Carolina
Kansas Department of Health and Environment, 2002. Data Analysis: Methodology Used
in Kansas Lake TMDLs: Explanation of Bacteria TMDL Curves (PDF): Kansas
TMDL Curve Methodology. Online: http://www.kdhe.state.ks.us/tmdl/Data.htm.
LeGrand, H.E. 1954. Geology and Ground Water in the Statesville Area, North Carolina.
North Carolina Department of Conservation and Development. Prepared
Cooperatively by the Geological Survey, US Department of the Interior. Bulletin
Number 68.
North Carolina Department of Environment and Natural Resources, Division of Water
Quality, 2001, Final Total Maximum Daily Load for Fecal Coliform, Fourth
Creek (Sub-basin 03-07-06). Online at:
http://h2o.enr.state.nc.us/tmdl/TMDL_list.htm
North Carolina Department of Environment and Natural Resources, Division of Water
Quality, 2002, Water Quality Assessment and Impaired Waters List (2002
Integrated 305(b) and 303(d) Report (Final), North Carolina Department of
Environment and Natural Resources, Division of Water Quality, Raleigh, North
Carolina.
North Carolina Division of Water Quality. 2003. Total Maximum Daily Loads for
Turbidity and Fecal Coliform for East Fork Deep River, North Carolina. Draft
11/05/03. Prepared by: NC Department of Environment and Natural Resources,
Division of Water Quality with support from TetraTech, Inc., Research Triangle
Park, NC 27709
Rosgen. D.L., A Practical Method of Computing Streambank Erosion Rate. Wildland
Hydrology, Inc. Pagosa Springs, Colorado. Online at:
http://www.wildlandhydrology.com/assets/Streambank_erosion_paper.pdf
Sheely, L. H. July 2002. Load Duration Curves: Development and Application to Data
Analysis for Streams in the Yazoo River Basin, MS. Special Project – Summer
2002. Jackson Engineering Graduate Program.
Fourth Creek Turbidity TMDL November 2003
28
Soil and Water Conservation District, Iredell County. 1999. District Ag Sediment
Survey/Action Plan. Fourth Creek – Iredell County. Statesville, NC
Stiles, T.C. 2002. Incorporating hydrology in determining TMDL endpoints and
allocations. Proceedings from the WEF National TMDL Science and Policy 2002
Conference.
United States Department of Agriculture. 1964. Soil survey of Iredell County, North
Carolina.
United States Department of Agriculture, Natural Resources Conservation Service. 1995.
Soil survey of Rowan County.
Online at: http://www.mo14.nc.nrcs.usda.gov/technical/soilsurveys.html
United States Department of Agriculture. Agreement between The State of North
Carolina and The U.S. Department of Agriculture Commodity Credit Corporation
concerning the implementation of the North Carolina Conservation Reserve
Enhancement Program Online at: http://www.fsa.usda.gov/dafp/cepd/crep/NCok.htm
United States. Environmental Protection Agency (USEPA). 1991. Guidance for Water
Quality-Based Decisions: The TMDL Process. Assessment and Watershed
Protection Division, Washington, DC.
United States. Environmental Protection Agency (USEPA). 1993. Guidance Specifying
Management Measures for Sources of Nonpoint Pollution in Coastal Waters.
EPA-840-B-92-002. Washington, DC.
United States Environmental Protection Agency (USEPA). 2000. Revisions to the Water
Quality Planning and Management Regulation and Revisions to the National
Pollutant Discharge Elimination System Program in Support of Revisions to the
Water Quality Planning and management Regulation; Final Rule. Fed. Reg.
65:43586-43670 (July 13, 2000).
United States. Environmental Protection Agency (USEPA). Federal Advisory Committee
(FACA). 1998. Draft Final TMDL Federal Advisory Committee Report. April.
United States. Environmental Protection Agency (USEPA). October 1999. Protocols for
Developing Sediment TMDLs – First Edition. EPA 841-B-99-004. Washington,
DC.
USGS. 1999. Relation of Land Use to Streamflow and Water Quality at Selected Sites in
the City of Charlotte and Mecklenburg County, North Carolina, 1993-98. Water
Resources Investigations Report 99-4180. Raleigh, NC.
Wayland, R. 2002. November 22, 2002 Memo from Robert Wayland of the U.S.
Environmental Protection Agency to Water Division Directors. Subject:
Fourth Creek Turbidity TMDL November 2003
29
Establishing TMDL Waste Load Allocations for stormwater sources and NDPES
permit requirements based on those allocations.
Fourth Creek Turbidity TMDL November 2003
30
Appendix A. DWQ Ambient Monitoring and Discharger Coalition Data
Ambient Monitoring Results for TSS and Turbidity at Station Q3735000
DATE
RESIDUE TOTAL
NONFILTRABLE
(MG/L) (method 00530)
TURBIDITY LAB
NEPHELOME
UNITS NTU (method 82079)
01/29/97 31 32
02/24/97 24 17
03/20/97 98 80
04/22/97 87
05/12/97 20 14
07/15/97 32 18
08/12/97 20 14
09/10/97 38 36
10/20/97 10 23
11/05/97 5 6.4
12/19/97 9 3.7
01/15/98 400 240
02/23/98 200 22
03/30/98 21 9.2
04/21/98 70 37
05/28/98 46 28
06/11/98 73 50
07/20/98 20 17
08/31/98 1 6.2
09/10/98 9 11
10/06/98 11 10
11/17/98 13 13
12/10/98 8 10
01/13/99 9 8.5
02/17/99 11 7.6
03/16/99 16 15
04/26/99 13
05/18/99 15 13
06/14/99 7 12
07/12/99 140 70
08/09/99 60 48
09/09/99 12 10
10/12/99 38 36
11/08/99 4 3.9
12/15/99 12 20
01/04/00 17 13
02/14/00 360 290
03/14/00 9 7.9
04/19/00 54 37
05/16/00 13 4.3
06/15/00 18 9.4
07/17/00 19 24
08/09/00 10 9.6
Fourth Creek Turbidity TMDL November 2003
31
DATE
RESIDUE TOTAL
NONFILTRABLE
(MG/L) (method 00530)
TURBIDITY LAB
NEPHELOME
UNITS NTU (method 82079)
09/07/00 12
10/16/00 4.2
11/16/00 6 6.2
12/06/00 4.8
01/08/01 38
02/05/01 8 8
04/19/01 8.2
05/10/01 8 8.1
06/11/01 14
08/14/01 56 70
09/10/01 5.7
10/03/01 4.4
11/08/01 2.5 5.3
12/04/01 6.5
01/10/02 12
02/13/02 10 14
03/20/02 29
04/24/02 10
05/14/02 39 60
06/10/02 10
07/08/02 19
08/27/02 12 38
09/18/02 220
10/16/02 390
11/13/02 94 100
12/18/02 19
01/29/03 8.7
02/20/03 150 140
03/20/03 500
04/07/03 260
05/07/03 34 45
Fourth Creek Turbidity TMDL November 2003
32
Discharger Coalition Monitoring Results at Station Q3735000
DATE TURBIDITY (NTU)
06/04/1998 39
07/14/1998 53.6
08/03/1998 14.1
09/02/1998 6.4
10/15/1998 11.8
11/11/1998 15.8
12/11/1998 11.9
01/08/1999 18.8
02/05/1999 20.5
03/10/1999 17.5
04/06/1999 27.8
05/11/1999 25
06/02/1999 27.8
07/06/1999 34.3
08/10/1999 15.3
09/07/1999 33
10/13/1999 33.6
11/08/1999 8.1
12/10/1999 15
01/12/2000 58
02/03/2000 24
03/23/2000 62.6
04/21/2000 69.4
05/09/2000 58.9
06/13/2000 35.2
07/11/2000 22.8
08/31/2000 34.7
09/07/2000 26.2
10/26/2000 6.2
11/30/2000 5.8
12/21/2000 5.6
01/17/2001 5.5
02/15/2001 6.4
03/05/2001 21
04/12/2001 12
05/15/2001 6.7
06/12/2001 10
07/16/2001 11
08/06/2001 5.2
09/10/2001 9.6
10/08/2001 6.6
11/12/2001 4
12/03/2001 5.8
01/14/2002 9
02/11/2002 15
03/04/2002 12
04/08/2002 8.2
05/06/2002 14
Fourth Creek Turbidity TMDL November 2003
33
DATE TURBIDITY (NTU)
06/10/2002 8.3
07/08/2002 18
08/05/2002 8.4
09/23/2002 36
10/07/2002 6.6
11/04/2002 8.6
12/02/2002 7.3
01/06/2003 167
02/10/2003 125
03/17/2003 600
04/07/2003 600
05/12/2003 290
06/09/2003 230
Fourth Creek Turbidity TMDL November 2003
34
Discharger Coalition Monitoring Results at Station Q3720000 (this information was
not used in calculating the TMDL).
DATE Turbidity (NTU)
06/04/1998 37
07/14/1998 49.2
08/03/1998 14.7
09/02/1998 7.9
10/15/1998 12.9
11/11/1998 18.4
12/11/1998 10.8
01/08/1999 18.1
02/05/1999 18.3
03/10/1999 15.1
04/06/1999 21.5
05/11/1999 26
06/02/1999 51.2
07/06/1999 37
08/10/1999 15
09/07/1999 28
10/13/1999 54.3
11/08/1999 8.4
12/10/1999 13.8
01/12/2000 47
02/03/2000 15.3
03/23/2000 46.6
04/21/2000 65.6
05/09/2000 46.5
06/13/2000 34.5
07/11/2000 23.7
08/31/2000 136
09/07/2000 26.7
10/26/2000 4.85
11/30/2000 5.8
12/21/2000 5.6
01/17/2001 6.2
02/15/2001 12
03/05/2001 24
04/12/2001 7.1
05/15/2001 7
06/12/2001 12
07/16/2001 11
08/06/2001 5.4
09/10/2001 8.7
10/08/2001 6.4
11/12/2001 4.3
12/03/2001 5.3
01/14/2002 14
02/11/2002 17
03/04/2002 14
04/08/2002 5.1
Fourth Creek Turbidity TMDL November 2003
35
DATE Turbidity (NTU)
05/06/2002 8.1
06/10/2002 7.5
07/08/2002 10
08/05/2002 17
09/23/2002 29
10/07/2002 7.2
11/04/2002 4.3
12/02/2002 5.8
01/06/2003 230
02/10/2003 84
03/17/2003 880
04/07/2003 420
05/12/2003 350
06/09/2003 165
Fourth Creek Turbidity TMDL November 2003
36
Appendix B. Monthly average effluent TSS concentrations (mg/L) at the Statesville
WWTP (NC0031836) and Southern States Cooperative Facility (NC0082821) during
years 1998-2003.
Statesville WWTP (NC0031836)
1998 1999 2000 2001 2002 2003
January 13.1 10.7 15.2 9.1 8.2 7.1
February 18.4 10.3 12.7 9.3 10.7 8.2
March 15.1 12.0 11.0 13.8 10.5 12.8
April 7.4 15.1 15.3 12.9 10.7 8.6
May 8.1 14.2 8.4 15.3 15.7 6.4
June 4.8 8.8 7.5 12.4 8.8 18.1
July 7.7 11.8 7.1 13.8 < 5.0 4.3
August 8.3 10.4 7.2 19.4 2.3 3.8
September 7.5 7.7 7.3 8.1 3.6 4.9
October 6.4 9.7 7.4 9.0 4.9
November 7.7 11.0 5.7 9.7 6.4
December 8.8 14.0 7.5 6.6 5.4
Southern States Cooperative facility (NC0082821)
1998 1999 2000 2001 2002
January 26.0 23.7 15.2
February 23.6 23.9 21.7 18.5
March 24.2 17.8 17.5 0.03
April 20.7 14.1
May 18.0
June 18.1
July 26.2
August 20.9
September 18.5
October 18.8
November 22.5 23.5
December 22.3 27.1 7.0
Fourth Creek Turbidity TMDL November 2003
37
Appendix C. General Permitees located within the Fourth Creek watershed.
Permit
Number
Coc
Number Facility Name Receiving Waterbody DWQ Description
NCS000018 N/A J. C. Steele & Sons; Inc. UT Fourth Ck No description available
NCG020000 NCG020109 Martin Marietta - Statesville SW-Mining
NCG030000 NCG030052 Hunt Manufacturing Company Gregory Ck SW-Metal processing
NCG030000 NCG030255 JC Steele & Sons Inc. UT To Fourth Ck SW-Metal processing
NCG030000 NCG030256 Wheeling Corrugating Company UT To Fourth Ck SW-Metal processing
NCG030000 NCG030379 MMI Products; Inc.-Merchants Metals UT Fourth Ck SW-Metal processing
NCG030000 NCG030442 Commscope, Inc. Gregory Ck SW-Metal processing
NCG030000 NCG030445 Dana Spicer Clark - Hurth UT fourth Ck SW-Metal processing
NCG040000 NCG040120 Bruce Hardwood Flooring LP Third Ck & Fourth Ck SW-Chip mill
NCG040000 NCG040237 Shaver Wood Products; Inc. UT To Fourth Ck SW-Chip mill
NCG050000 NCG050029 UNIWOOD Morrison Ck SW-Textile, paperboard, rubber (not tires) processing
NCG050000 NCG050098 International Paper; Container Div. Gregory Ck SW-Textile, paperboard, rubber (not tires) processing
NCG050000 NCG050108 Rubbermaid-Statesville; Inc. Gregory Ck SW-Textile, paperboard, rubber (not tires) processing
NCG050000 NCG050265 Jet Corr Statesville MS4 to UT
Gregory Ck
SW-Textile, paperboard, rubber (not tires) processing
NCG050000 NCG050272 Iredell Fiber; Inc. UT Fourth Ck SW-Textile, paperboard, rubber (not tires) processing
NCG060000 NCG060156 Bartlett & Co. D/B/A Bartlett Milling Co. Fourth Ck SW-Food, tobacco, cosmetics processing
NCG080000 NCG080016 Ruan Leasing Company UT To Fourth Ck SW-Vehicle maintenance areas, fuel storage sites
NCG080000 NCG080360 Ruan Leasing Company- Statesville UT Fourth Ck SW-Vehicle maintenance areas, fuel storage sites
NCG080000 NCG080568 NC Army National Guard-Statesville NG
Armory
UT Gregory Ck SW-Vehicle maintenance areas, fuel storage sites
NCG090000 NCG090023 Engineered Polymer Solutions; Inc. D/b/a
Valspar Corporation
UT Fourth Ck SW-Paint processing
NCG100000 NCG100030 Matlocks Used Cars UT Fourth Ck SW-Auto junk yards
NCG120000 NCG120042 Iredell County Sanitary Landfill Fourth Ck SW-Landfills
NCG140000 NCG140172 Union Concrete UT of Fourth Ck SW-Ready-Mix concrete
NCG160000 NCG160067 APAC-Carolina Inc.-North Side Drive Plant Morrison Ck SW-Asphalt paving and block processing
NCG170000 NCG170017 John Boyle & Co.; Inc. UT of Fourth Ck SW-Textile Mill
NCG170000 NCG170127 Carolina Mills; Inc.-Plant 12 Fourth Ck SW-Textile Mill
NCG210000 NCG210003 Intercraft Industries; L. P. Fourth Ck SW-Wood processing
Fourth Creek Turbidity TMDL November 2003
39
Appendix D. Methodology for developing the Load Duration Curve
The load duration curve method is based on comparison of the frequency of a given flow
event with its associated water quality load. In the case of applying the NTU criteria, a
correlation is necessary between NTU and TSS to allow for calculation of a load in mass
per time units. Data from the Fourth Creek ambient station (Station Q3735000) was used
in this this TMDL resulted in the below equation:
TSS concentration (mg/L) = (1.341* Turbidity (NTU)) – 1.008
R2 = 0.8435
A LDC can be developed using the following steps:
1. Plot the Flow Duration Curve, Flow vs. % of days flow exceeded.
2. Develop TSS-turbidity correlation.
3. Translate turbidity values to equivalent TSS values using the linear regression
equation from the correlation.
4. Translate the flow-duration curve into a LDC by multiplying the water quality
standard (as equivalent TSS concentration), the flow and a units conversion factor;
the result of this multiplication is the maximum allowable load associated with each
flow.
5. Graph the LDC, maximum allowable load vs. percent of time flow is equaled or
exceeded.
6. Water quality samples, expressed as estimated TSS values, are converted to loads
(sample water quality data multiplied by daily flow on the date of sample).
7. Plot the measured loads on the LDC
Fourth Creek Turbidity TMDL November 2003
40
Appendix E. Load Reduction Estimates for Turbidity in Fourth Creek.
Percent of Days flow is
exceeded
TSS Load based on
Regression Line
(mg TSS/L)
TSS Load based on
SWQS with MOS
(mg TSS/L)
Load Reduction
Required at each flow
(mg TSS/L)
10% 55,217 25,492 29,725
11% 53,546 24,006 29,540
12% 51,925 22,817 29,108
13% 50,353 22,371 27,983
14% 48,829 21,033 27,796
15% 47,351 20,439 26,913
16% 45,918 19,993 25,925
17% 44,528 19,547 24,981
18% 43,180 18,506 24,674
19% 41,873 18,209 23,664
20% 40,606 17,615 22,991
21% 39,377 17,466 21,911
22% 38,185 16,723 21,462
23% 37,029 16,574 20,455
24% 35,908 16,277 19,631
25% 34,821 15,831 18,990
26% 33,767 15,385 18,382
27% 32,745 15,088 17,657
28% 31,754 14,790 16,963
29% 30,793 14,345 16,448
30% 29,861 14,196 15,665
31% 28,957 13,899 15,058
32% 28,080 13,750 14,330
33% 27,230 13,453 13,777
34% 26,406 13,155 13,250
35% 25,607 13,007 12,600
36% 24,832 12,710 12,122
37% 24,080 12,561 11,519
38% 23,351 12,412 10,939
39% 22,644 12,115 10,529
40% 21,959 11,818 10,141
41% 21,294 11,669 9,625
42% 20,650 11,520 9,129
43% 20,024 11,223 8,801
44% 19,418 11,075 8,344
45% 18,831 10,777 8,053
46% 18,261 10,629 7,632
47% 17,708 10,331 7,376
48% 17,172 10,183 6,989
49% 16,652 10,034 6,618
50% 16,148 9,886 6,263
51% 15,659 9,737 5,922
52% 15,185 9,588 5,597
53% 14,726 9,440 5,286
54% 14,280 9,291 4,989
55% 13,848 9,142 4,705
56% 13,428 8,994 4,435
57% 13,022 8,845 4,177
58% 12,628 8,696 3,931
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Percent of Days flow is
exceeded
TSS Load based on
Regression Line
(mg TSS/L)
TSS Load based on
SWQS with MOS
(mg TSS/L)
Load Reduction
Required at each flow
(mg TSS/L)
59% 12,246 8,548 3,698
60% 11,875 8,399 3,476
61% 11,515 8,251 3,265
62% 11,167 8,102 3,065
63% 10,829 7,953 2,876
64% 10,501 7,805 2,696
65% 10,183 7,656 2,527
66% 9,875 7,507 2,368
67% 9,576 7,359 2,217
68% 9,286 7,210 2,076
69% 9,005 7,061 1,944
70% 8,733 6,913 1,820
71% 8,468 6,764 1,704
72% 8,212 6,467 1,745
73% 7,963 6,318 1,645
74% 7,722 6,170 1,553
75% 7,489 6,021 1,468
76% 7,262 5,872 1,389
77% 7,042 5,724 1,318
78% 6,829 5,575 1,254
79% 6,622 5,426 1,196
80% 6,422 5,129 1,293
81% 6,227 4,981 1,247
82% 6,039 4,832 1,207
83% 5,856 4,683 1,173
84% 5,679 4,535 1,144
85% 5,507 4,386 1,121
86% 5,340 4,089 1,251
87% 5,179 3,940 1,238
88% 5,022 3,792 1,230
89% 4,870 3,643 1,227
90% 4,722 3,346 1,377
91% 4,579 3,048 1,531
92% 4,441 2,900 1,541
93% 4,306 2,751 1,555
94% 4,176 2,602 1,574
95% 4,050 2,261 1,789
Averages: 19,703 10,519 9,184
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Appendix F. Relative Pollutant Contributions from the USGS report “Relation of
Land Use to Streamflow and Water Quality at Selected Sites in the City of Charlotte
and Mecklenburg County, North Carolina, 1993-98” (USGS, 1999).
Landuse Type
TSS Concentration
(ton/mi2/yr)
Mixed forest/pasture/ low density residential 2,400
Mixed forest, pasture, medium-and low-density residential 2,100
Mixed forest, pasture, medium-and low-density residential 564
Average Rural 1,688
Industrial 122
Industrial 300
Medium-density residential 225
Medium-density residential 77
High-density residential 1,000
Developing 4,700
Average Urban 1,071
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Appendix G. Agriculture Sediment Survey/Action Plan for Fourth Creek – Iredell County
conducted by the Soil and Water Conservation District, Iredell County in 1999.
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Appendix H. Public Notification of Public Review Draft of Fourth Creek Turbidity TMDL.
Fourth Creek, Yadkin River Basin
Now Available Upon Request
Fourth Creek Turbidity Total Maximum Daily Load
Is now available upon request from the North Carolina Division of Water Quality. This TMDL study
was prepared as a requirement of the Federal Water Pollution Control Act, Section 303(d). The
study identifies the sources of pollution, determines allowable loads to the surface waters, and
suggests allocations for turbidity.
TO OBTAIN A FREE COPY OF THE TMDL REPORT:
Please contact Mr. Brian Jacobson (919) 733-5083, extension 552 or write to:
Mr. Brian Jacobson
Water Quality Planning Branch
NC Division of Water Quality
1617 Mail Service Center
Raleigh, NC 27699-1617
Interested parties are invited to comment on the draft TMDL study by April 12, 2004. Comments concerning
the reports should be directed to Mr. Brian Jacobson at the above address. The draft TMDL is also located
on the following website: http://h2o.enr.state.nc.us/tmdl
Public Meetings Notice
A public meeting to discuss the
Fourth Creek Turbidity TMDL
will be held on Friday, March 26th at 10:00am
at the following address:
The Old City Hall Building
Council Chambers
301 South Center Street
Statesville, North Carolina
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