HomeMy WebLinkAboutSalem and Grants Creek YadkinTMDLReport_Approved
Total Maximum Daily Load for Fecal
Coliform for Salem Creek and Turbidity for
Grants Creek in North Carolina
Final Report
EPA Approval Date: September 25, 2006
Prepared by:
NC Department of Environmental and Natural Resources
Division of Water Quality
Water Quality Section – Planning Branch
1617 Mail Service Center
Raleigh, NC 27699-1617
(919) 733-5083
Yadkin-Pee Dee River Basin
This page intentionally left blank.
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TMDL Summary Sheet
1. 303(d) List Information
State: North Carolina
Counties: Rowan, Forsyth
Basin: Yadkin- Pee Dee River Basin
Hydrologic Unit Code (HUC): 03040101170 (Salem Creek)
03040103010 (Grants Creek)
Waterbody
Name
Description Assessment
Unit (AU):
Class Subbasin Impairment Miles
Salem Creek
(Middle Fork
Muddy Creek)
From
Winston-
Salem
Water
Supply Dam
(Salem
Lake) to
Muddy
Creek
12-94-12-(4) C 03-07-04 Fecal
Coliform
12.0
Grants Creek From SR
1910 to
Yadkin
River
12-110b C 03-07-04 Turbidity 1.2**
** The impairment length of Grants Creek is incorrectly listed on the 303(d) list as 1.2 miles. The
actual impairment length is 4.2 miles. This will be corrected in the next version of the 303(d) list.
Constituents of Concern: Fecal Coliform Bacteria (Salem Creek) and Turbidity
(Grants Creek)
Reason for Listing: Standard Violations
Applicable Water Quality Standards: For Class C waters:
• Turbidity: not to exceed 50 NTU
• Fecal coliform shall not exceed a geometric mean
of 200/100 ml (membrane filter count) based
upon at least five consecutive samples examined
during any 30 day period, nor exceed 400/100 ml
in more than 20 percent of the samples examined
during such period.
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2. TMDL Development
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
record (excludes extreme drought (>95th percentile) and floods (<10th
percentile). Percent reductions expressed as the average value
between existing loads (typically calculated using an equation to fit a
curve through actual water quality violations) and the allowable load
at each percent flow exceeded.
Critical Conditions: Critical conditions are accounted in the load curve analysis by using
an extended period of stream flow and water quality data, and by
examining at what flow (percent flow exceeded) the existing load
violations occur.
Seasonal Variation: Seasonal variation in hydrology, climatic conditions, and watershed
activities are represented through the use of a continuous flow gage
and the use of all readily available water quality data collected in the
watershed.
3. TMDL Allocation Summary
Pollutants/Watershed Existing
Exceeding
Load
WLA LA MOS TMDL Percent
Reduction1
I. TSS (tons/day)
Grants Creek 8.03 0.683 4.17 0.68 5.54 31.0%
II. Fecal Coliform (colony forming units (cfu)/day)
Salem Creek 5.74E12 7.49E11 7.37E10 9.14E10 9.14E11 84.1%
1. Percent reduction represents overall TMDL reduction - calculated as:
(Existing Load – TMDL)/Existing Load
Notes:
1. LA = TMDL – WLA – MOS.
2. TMDL represents the average allowable load between the 95th and 10th percent recurrence
interval.
3. Explicit (10%) and implicit Margins of Safety are considered.
4. Turbidity is not a concentration and, as a measure, cannot be directly converted into
loadings required for the TMDL. Total suspended solids (TSS) was therefore selected as the
surrogate measure for turbidity and used to develop the TMDL target and limits (USEPA
1999).
5. Overall reduction is based on the instantaneous standard of 400 cfu/100ml and is assumed to
be more stringent than the geometric mean standard.
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4. Contributing Municipalities TMDL Allocation Summary
Watershed Municipalities
Winston-Salem
Kernersville Salem Creek
Walkertown
Salisbury
China Grove Grants Creek
Landis
5. Contributing NPDES Facilities TMDL Allocation Summary
Watershed Permit
Number Owner Facility Name
Salem Creek NC0037834 City of Winston Salem Archie Elledge WWTP
NC0034703 Rowan-Salisbury
Schools Knollwood Elementary School
NC0037184 Lakeside Investment
Properties Oak Haven Mobile Home Park Grants Creek
NC0042439 Westside Swim &
Racquet Club Westside Swim & Racquet Club
6. Public Notice Information
Summary: A draft of the TMDL was publicly noticed
through various means. The TMDL was public
noticed in the relevant counties through two local
newspapers (Salisbury Post on May 3, 2006 and
Winston-Salem Journal on May 4, 2006,
Appendix D). The TMDL was also public
noticed on May 1, 2006 through the North
Carolina Water Resources Research Institute
email list-serve (Appendix D). Finally, the
TMDL was available on DWQ’s website
http://h2o.enr.state.nc.us/tmdl/ during the
comment period. The public comment period
lasted until June 2, 2006. Two written comments
were received, both from NC Department of
Transportation. DWQ’s responses to those
comments are provided in Appendix E of the
TMDL report.
iv
Did notification contain specific mention of
TMDL Proposal?
Yes
Were comments received from the public? Yes
Was a responsiveness summary prepared? Yes, see Appendix E of the TMDL report
7. Public Notice Date: May 1, 2006
8. Submittal Date: July 21, 2006
9. Establishment Date: September 25, 2006
10. EPA Lead on TMDL (EPA or Blank):
11. DOT a Significant Contribution (Yes or Blank):
a. DOT a Significant Contribution in Grants Creek (Yes or Blank):
b. DOT a Significant Contribution in Salem Creek (Yes or Blank):
12. Endangered Species (Yes or Blank):
a. Endangered Species in Grants Creek (Yes or Blank):
b. Endangered Species in Salem Creek (Yes or Blank):
13. TMDL Considers Point Source, Nonpoint Source, or Both: Both
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Table of Contents
1.0 Introduction 1
1.1 TMDL Definition 1
1.2 TMDL Components 2
1.3 Water Quality Target: North Carolina Standards 3
1.3.1 Water Quality Standard for Turbidity 3
1.3.2 Water Quality Standard for Fecal Coliform 3
1.4 Watershed Description 3
1.5 Water Quality Monitoring 7
1.5.1 Fecal Coliform Monitoring in Salem Creek 7
1.5.2 Turbidity and TSS Monitoring in Grants Creek 8
2.0 Source Assessment 10
2.1 General Sources of Turbidity 10
2.1.1 Point Sources of Turbidity 10
2.1.2 Nonpoint Sources of Turbidity 11
2.2 General Sources of Fecal Coliform 12
2.2.1 Point Sources of Fecal Coliform 12
2.2.2 Nonpoint Sources of Fecal Coliform 13
3.0 Salem Creek Impairment 14
3.1 Source Assessment 14
3.1.1 NPDES Wastewater Permits 14
3.1.2 NPDES General Permits 15
3.1.3 NPDES Stormwater MS4s 15
3.1.4 Livestock Populations 15
3.1.5 Septic Tanks 15
3.2 Technical Approach 16
3.2.1 Endpoint for Fecal Coliform 16
3.2.2 Flow Duration Curve 16
3.2.3 Load Duration Curve 18
3.3 Total Maximum Daily Load (TMDL) 19
3.3.1 Margin of Safety (MOS) 20
3.3.2 Target Reduction 20
3.3.3 TMDL Allocation 21
3.3.4 Critical Condition and Seasonal Variation 24
4.0 Grants Creek Impairment 25
4.1 Source Assessment 25
4.1.1 NPDES Wastewater Permits 25
4.1.2 NPDES General Permits 26
4.1.3 NPDES Stormwater MS4s and other Nonpoint Sources 27
4.2 Technical Approach 27
4.2.1 Endpoint for Turbidity 28
4.2.2 Flow Duration Curve 29
4.2.3 Load Duration Curve 29
4.3 Total Maximum Daily Load (TMDL) 32
4.3.1 Margin of Safety (MOS) 32
4.3.2 Target Reduction 32
4.3.3 TMDL Allocation 33
4.3.4 Critical Condition and Seasonal Variation 35
5.0 Summary and Future Consideration 36
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5.1 Stream Monitoring 36
5.2 Implementation Plan 36
6.0 Public Participation 38
7.0 References 39
Appendix A: Salem Creek Data 41
Appendix B: Grants Creek Data 43
Appendix C: Estimates of Relative Loadings for Point and Nonpoint Sources 47
Appendix D. Public Notification of TMDLs for Fecal Coliform for Salem Creek and Turbidity for
Grants Creek 48
Appendix E. Responsiveness Summary for “Total Maximum Daily Load for Fecal Coliform for Salem
Creek and Turbidity for Grants Creek in North Carolina” 51
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1.0 Introduction
1.1 TMDL Definition
This report presents the development of Total Maximum Daily Loads (TMDLs) for two
waterbodies in North Carolina: Salem Creek and Grants Creek. Both waterbodies are located in
the Yadkin-Pee Dee River Basin (Figure 1.1). As identified by the North Carolina Division of
Water Quality (DWQ), the impaired segments of the two waterbodies are described in Table 1.1.
Table 1.1. Description of Impaired Segments for Grants Creek and Salem Creek.
Waterbody
Name
Description Assessment
Unit (AU):
Class Subbasin Impairment Miles
Salem Creek
(Middle
Fork Muddy
Creek)
From Winston-
Salem Water
Supply Dam
(Salem Lake)
to Muddy
Creek
12-94-12-(4) C1 03-07-04 Fecal
Coliform
12.0
Grants
Creek
From SR 1910
to Yadkin
River
12-110b C 03-07-04 Turbidity 4.22
1 Class C waters are protected for secondary recreation, fishing, wildlife, fish and aquatic life propagation and
survival, agriculture and other uses suitable for class C. There are no restrictions on watershed development or
types of discharges.
2 The impairment length of Grants Creek is incorrectly listed in the 303(d) list as 1.2 miles. The actual impairment
length is 4.2 miles.
Section 303(d) of the Clean Water Act (CWA) requires States to develop a list of water bodies
that do not meet water quality standards or have impaired uses. The list, referred to as the 303(d)
list, is submitted biennially to the U.S. Environment Protection Agency (USEPA) for review.
The 303(d) process requires that a Total Maximum Daily Load (TMDL) be developed for each
of the waters appearing on Category 5 of the 303(d) list.
Figure 1.1. Location of Yadkin River Basin within North Carolina.
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1.2 TMDL Components
The objective of a TMDL is to allocate allowable pollutant loads to known sources so that
actions may be taken to restore the water to its intended uses (USEPA, 1991). Generally, the
primary components of a TMDL, as identified by USEPA (1991, 2000a) and the Federal
Advisory Committee (FACA) (USEPA, 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.
Assimilative Capacity. Estimation or level of pollutant reduction needed to achieve water quality
goal. The level of pollution should be characterized for the water body, highlighting how current
conditions deviate from the target end-point. Generally, this component is identified through
water quality modeling.
Allocation of Pollutant Loads. Allocating pollutant control responsibility to the sources of
impairment. The waste load 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 nonpoint sources, storm water, and
natural background.
Margin of Safety. The margin of safety addresses uncertainties associated with pollutant loads,
modeling techniques, and data collection. Per EPA (2000a), 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).
Section 303(d) of the CWA and the Water Quality Planning and Management regulation
(USEPA, 2000a) requires EPA to review all TMDLs for approval. Once EPA approves a
TMDL, the water body may be moved to Category 4a of the 303(d) list. Water bodies remain on
Category 4a of the list until compliance with water quality standards is achieved. Where
conditions are not appropriate for the development of a TMDL, management strategies may be
implemented in an effort to restore water quality.
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1.3 Water Quality Target: North Carolina Standards
1.3.1 Water Quality Standard for Turbidity
The North Carolina fresh water quality standard for Class WS-IV and C waters for turbidity
(T15A: 02B.0211) 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 stream,
lakes or reservoirs designated as trout water; 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)
recommended by the Designated Nonpoint Source Agency. BMPs must be in full
compliance with all specifications governing the proper design, installation,
operation and maintenance of such BMPs.
1.3.2 Water Quality Standard for Fecal Coliform
The North Carolina fresh water quality standard for Class WS-IV and C waters for fecal
Coliform (T15A: 02B.0211) states:
Organisms of the coliform group: Fecal coliforms shall not exceed a geometric
mean of 200/100ml (MF count) based upon at least five consecutive samples
examined during any 30-day period, nor exceed 400/100ml in more than 20
percent of the samples examined during such period; violations of the fecal
coliform standard are expected during rainfall events and, in some cases, this
violation is expected to be caused by uncontrollable nonpoint source pollution;
all coliform concentrations are to be analyzed using the membrane filter
technique unless high turbidity or other adverse conditions necessitate the tube
dilution method; in case of controversy over results, the MPN 5-tube dilution
technique will be used as the reference method.
1.4 Watershed Description
Watershed areas were delineated either by solely using the USGS 14-digit hydrologic units, or
by a combination of the hydrologic units and the automatic delineation tools provided in version
3.0 of the Better Assessment Science Integrating Point and Nonpoint Sources (BASINS) system.
Salem Creek is located in the Yadkin-Pee Dee River Basin. The Salem Creek watershed is
located entirely within Forsyth County, and major parts of the watershed are located within the
incorporated limits of the city of Winston-Salem, Figure 1.2. The watershed is located within
hydrologic unit 03040101170060.
4
Winston-Salem
Kernersville
Walkertown
7 0 7 14 Miles
Municipal Boundaries
Waterbodies
Streams
Salem Creek Impaired Length
Forsyth County Boundary
Salem Creek HUC
N
EW
S
Figure 1.2. Salem Creek Watershed and Surrounding Area.
Grants Creek is located in the Yadkin-Pee Dee River Basin. The Grants Creek watershed is
located entirely within Rowan County, and a part of the watershed is located within the
incorporated limits of the city of Salisbury, Figure 1.3. The watershed is located within
hydrologic unit 03040103010010.
5
{Grants Creek Impaired Length
Grants Creek
Grants Streams
Grants Creek Watershed
Rowan County
Grants Municipalities
0 6 12 18 243
Miles
Figure 1.3. Grants Creek Watershed and Surrounding Area.
Population is measured in census blocks, which do not usually coincide with watershed
boundaries. Therefore, population information is grouped by county, as seen in Table 1.2. The
population totals in each county for 2000 and 2003 given, as well as percent change in these
values. The percent change statistic gives an estimate on the rate of growth in each county.
Table 1.2. Population Information for Relevant Counties.
Population
County Population, Percent
Change, 1990 to
2000
2000
Population
Population,
percent change,
April 1, 2000
to July 1, 2003
2003
Population
Rowan 17.8% 130,340 2.8% 133,931
Forsyth 15.1% 306,067 3.8% 317,810
http://quickfacts.census.gov/qfd/states/37/37025.html
Land Use/Land Cover
The land use/land cover characteristics of the two watersheds were determined using the 1996
land cover data developed from the 1993-1994 LANDSAT satellite imagery. The North
Carolina Center for Geographic Information and Analysis (CGIA), in cooperation with the North
Carolina Department of Transportation (NCDOT) and the Environmental Protection Agency
6
Region IV Wetland Division, contracted Earth Satellite Corporation of Rockville, Maryland to
generate comprehensive land cover data for the entire state of North Carolina. The land use and
land cover (LULC) data used contains more detailed information than is presented in this report.
The original LULC data was grouped into five distinct groups: Forrest/Wetland, Cultivated Crop,
Urban, Water, and Pasture/Herbaceous. This categorization is modeled after the North Carolina
Basin Plans. Table 1.3 shows the area in acres for each of these categories in each watershed.
Table 1.3. Land Use Acreages and their Percent Compositions in the Two Watersheds.
Grants Creek Salem Creek
Land Use
Area
(acres)
Area
(%)
Area
(acres)
Area
(%)
Forrest/Wetland 23,378 54 21,166 47
Cultivated Crop 2,688 6 58 0
Urban 2,298 5 11,352 25
Water 251 1 527 1
Pasture/Herbaceous 14,454 34 11,791 26
Total 43,069 100 44,894 100
Land use and land cover information is also provided graphically in the following figures. Salem
Creek land use land cover information can be found in Figure 1.4. Grants Creek land use land
cover information can be found in Figure 1.5.
4 0 4 8 Miles
Winston-Salem Land Use
Forrest/Wetland
Cultivated Crop
Urban
Water
Pasture/Herbaceous
Streams
Waterbodies
N
EW
S
Figure 1.4. Land Use and Land Cover distribution in the Salem Creek Watershed.
7
Grants Creek Watershed Land Use
Forrest/Wetland
Cultivated Crop
Urban
Waterbodies
Pasture/Herbaceous
Waterbodies.shp
Streams.shp
0 6 12 Miles
N
EW
S
Figure 1.5. Land Use and Land Cover distribution in the Grants Creek Watershed.
1.5 Water Quality Monitoring
1.5.1 Fecal Coliform Monitoring in Salem Creek
The DWQ has one monitoring station on Salem Creek: Q2510000 at the Elledge water treatment
plant. The Yadkin Pee-Dee River Basin Association (YPDRBA) maintains three sampling
stations in Salem Creek: Q2540000 at West Clemmonsville Road, Q2570000 at Fraternity
Church Road, and Q2479455 at SR 2740 Reynolds Park Road. The locations of these stations
are shown in Figure 1.6. There are numerous qualifiers on the sampling data, which can be
found in Appendix Table A.1. In addition to the normal monthly samples, nine additional
samples were taken at two of the sites in the latter half of 2002 as a part of a special study. A
more detailed accounting of sampling can be found in Table 1.4. The samples that were
collected as part of the special study were further analyzed using Antibiotic Resistance Analysis
(ARA). Further details of this analysis can be found in Maptech-HDR (2005).
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Table 1.4. Salem Creek Sampling
Station Sampling
Period
Number of
Samples
Collected
Approximate
Sampling
Frequency
Number of Samples
Exceeding Standard (400
colony forming units
(cfu)/100 ml)
Q2479455 8/98-2/04 81 Monthly 22
Q2540000 8/98-2/04 67 Monthly 21
Q2570000 8/98-2/04 81 Monthly 29
Q2510000 8/98-3/04 61 Monthly 31
Figure 1.6. Water Quality Monitoring Stations in the Salem Creek Watershed.
1.5.2 Turbidity and TSS Monitoring in Grants Creek
There are two monitoring stations on Grants Creek: Q4540000 (maintained by YPDRBA at SR
1915 near Salisbury) and Q4600000 (maintained by the DWQ below Salisbury and Spencer
wastewater treatment plant). Locations of the stations are shown in Figure 1.7. A more detailed
accounting of sampling can be found in Table 1.5.
Q2570000
Q2479455
Q2510000
Q2540000
9
Table 1.5. Grants Creek Sampling.
Station
Turbidity
Sampling
Period
Turbidity
Number of
Samples
Collected
TSS
Sampling
Period
TSS
Number of
Samples
Collected
Approximate
Sampling
Frequency
Number of
Samples
Exceeding
Standard
(50 NTU)
Q4600000 1/97-12/04 91 1/97-7/04 57 Monthly/Every
Two Months
10
Q4540000 6/98-2/04 69 No
Samples
0 Monthly 6
!(!(
{
Grants Creek
Grants Creek Impaired Length
Streams
Grants Creek Watershed
Monitoring Stations
AGENCY
!(NCAMBNT
!(YPDRBA
0 2.5 5 7.5 101.25
Miles
Figure 1.7. Water Quality Monitoring Stations in the Grants Creek Watershed.
Q4600000
Q4540000
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2.0 Source Assessment
A source assessment is used to identify and characterize the known and suspected sources of
turbidity and fecal coliforms in the two watersheds. This section outlines the assessment
completed for the purpose of developing this TMDL. The NC Department of Environment and
Natural Resources (DENR) Geographic Information System (GIS) was used extensively for
these watershed characterizations.
2.1 General Sources of Turbidity
Turbidity is a measure of the cloudiness of water. In a water body, the cloudiness can be
enhanced due to silt and clay from watershed and stream erosion, organic detritus from streams
and wastewater, and phytoplankton growth. In this study, turbidity is measured in the
Nephelometric Turbidity Unit (NTU) and is significantly correlated with total suspended solid
(TSS).
2.1.1 Point Sources of Turbidity
Point sources are distinguished from nonpoint sources in that they discharge directly into streams
at a discrete point. Point sources of turbidity consist primarily of large and small industries,
wastewater-treatment plants, and Municipal Separate Storm Sewer System (MS4). As
authorized by the Clean Water Act, the DWQ regulates the National Pollutant Discharge
Elimination System (NPDES) permit program to control water pollution due to point sources.
Individual homes that are connected to a municipal system, use a septic system, or do not have a
surface discharge do not need an NPDES permit; however, industrial, municipal, and other
facilities must obtain permits if their discharges go directly to surface waters.
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. When effluent
turbidity 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.
NPDES general permitted facilities, while not subject to effluent TSS or turbidity limitations, are
required to develop a storm water pollution prevention plan, and conduct qualitative and/or
quantitative measurements at each storm water discharge outfall and vehicle maintenance area.
Sampling methodology and constituents to be measured are characteristic of the volume and
nature of the permitted discharge. For example, general permits for mining operations require
the permittee to measure settleable solids, total suspended solids, turbidity, rainfall, event
duration, and flow in storm water discharge areas. Measurements of pH, oil and grease, total
suspended solids, rainfall, and flow are required in on-site vehicle maintenance areas. Similarly,
monitoring is required in mine dewatering areas, wastewater associated with sand/gravel mining,
and in overflow from other process recycle wastewater systems.
11
A recent EPA mandate (Wayland, 2002) requires NPDES permitted storm water to be placed in
the waste load allocation (WLA), which was previously reserved for continuous point source
waste loads. In 1990, EPA promulgated rules establishing Phase I of the NPDES storm water
program. The Phase I program for Municipal Separate Storm Sewer System (MS4) requires
operators of medium and large MS4s, which generally serve populations of 100,000 or greater,
to implement a storm water management program as a means to control polluted discharges from
these MS4s. The new Phase II program is applied to populations of between 10,000 and 100,000
people.
2.1.2 Nonpoint Sources of Turbidity
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 from 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 leave
areas of ground with little vegetative cover. Unconfined animals with direct access to
streams can cause streambank damage and erosion.
• 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.
12
2.2 General Sources of Fecal Coliform
Both point sources and nonpoint sources may contribute fecal coliform to the water bodies.
Potential sources of fecal coliform loading are discussed below.
2.2.1 Point Sources of Fecal Coliform
Point sources of fecal coliform consist primarily of large and small industries, wastewater
treatment plants, and MS4s. As authorized by the Clean Water Act, the DWQ regulates the
NPDES permit program to control water pollution due to point sources. Individual homes that
are connected to a municipal system, use a septic system, or do not have a surface discharge do
not need an NPDES permit; however, industrial, municipal, and other facilities must obtain
permits if their discharges go directly to surface waters.
NPDES-Regulated Municipal and Industrial Wastewater Treatment Facilities Discharges from
wastewater treatment facilities may contribute fecal coliform to receiving waters. Municipal
treatment plants and industrial treatment plants are required to meet surface water quality criteria
for fecal coliform in their effluent. When effluent coliform 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.
NPDES general permitted facilities are required to develop pollution prevention plans to
discharge domestic wastewaters from single-family residences and other domestic discharges.
The permitted flow of these facilities may not in any case exceed 1,000 gallons per day. The
facilities are required to measure BOD5, total suspended residue, fecal coliform, and total
residual chlorine. The facilities must monitor the pollutants every year and document the
following maintenance activities:
• Septic tanks shall be maintained at all times to prevent seepage of sewage to the ground.
• Septic tanks will be checked at least yearly to determine if solids must be removed or if
other maintenance is necessary.
• Septic tanks shall be pumped out within three to five years of the issuance date on the
Certificate of Coverage.
• Contents removed from septic tanks shall be disposed at a location and in a manner
compliant with all local and state regulations.
• Surface sand filters, disinfection apparatus, and (if applicable) dechlorination apparatus
shall be inspected weekly to confirm proper operation.
13
2.2.2 Nonpoint Sources of Fecal Coliform
Fecal coliform from nonpoint sources include those sources that cannot be identified as entering
the water body at a specific location. Nonpoint source pollution can include both urban and
agricultural sources and human and non-human sources (Table 2.1). The nonpoint sources of
fecal coliform in the water bodies include wildlife, livestock (land application of agricultural
manure and grazing), urban development (stormwater runoff, including sources from domestic
animals), failing septic systems, and sewer line systems (illicit connections, leaky sewer lines
and sewer system overflows).
Table 2.1. Potential Source of Fecal Coliform Bacteria in Urban and Rural Watersheds.
(Source: Center for Watershed Protection, 1999)
Source Origin Type Source
Combined sewer overflows
Sanitary sewer overflows
Illegal sanitary connections to
storm drains
Sewered watershed
Illegal disposal to storm drains
Failing septic systems
Poorly operated package plant
Landfills
Human Sources
Non-sewered watershed
Marinas
Domestic animals and urban
wildlife
Dogs, cats, rats, raccoons,
pigeons, gulls, ducks, geese
Livestock and rural wildlife Cattle, horse, poultry, beaver,
muskrats, deer, waterfowl
Non-human Sources
Others Hobby farms
Land use can contribute to fecal coliform runoff. Agricultural land alongside a stream would
contribute fecal coliform from livestock and manure applications. In addition, when cattle have
direct access to streams, feces may be deposited directly into a stream.
Runoff from urban surface is also a potentially significant source of fecal coliform loadings.
Urban lands may contribute fecal coliform from pets such as dog and cats. In a study conducted
by Hyer et al., 2001, the bacterial loads due to dog waste accounted for nearly 10 percent of the
total bacterial load in three creeks of Virginia: Accotink Creek, Blacks Run, and Christians
Creek. Furthermore, wildlife feces in runoff may be a frequent source of fecal coliform loading
where forest dominates the streamside.
Fecal coliform can originate from various urban sources. These sources include pet waste,
runoff through stormwater, sewers, illicit discharges/connections of sanitary waste, leaky sewer
systems, and sewer system overflows.
Fecal coliform contamination can be profound when sewer pipes are clogged or flooded by
stormwater. Infiltration of rainfall can enter the sewer system through cracks and leaks in pipes.
This additional flow volume, in combination with the existing sewer flow, can exceed the
capacity of the system resulting in a sanitary-sewer-overflow (SSO).
14
3.0 Salem Creek Impairment
3.1 Source Assessment
3.1.1 NPDES Wastewater Permits
There are four facilities that discharge wastewater to the polluted portion of Salem Creek and
tributaries and are permitted individually under the NPDES program (Table 3.1). One of the
four permitted facilities has a limit for fecal coliform discharge, as can be found in the
BasinWide Information Management System (BIMS) database. Locations of the NPDES
facilities are shown in Figure 3.1.
Table 3.1. Individual NPDES Permittees in the Salem Creek Watershed.
Permit Owner Facility Permitted Flow
(MGD)
Fecal Coliform
(cfu/100ml)
NC0080853 Lucent
Technologies, Inc.
Salem Business Park
Remediation site 0.302 No Limit
NC0079821 City of Winston-
Salem R.A. Thomas WTP No Limit No Limit
NC0085871 Flakt Products Inc Flakt Products Incorporated No Limit No Limit
NC0037834 City of Winston-
Salem Archie Elledge WWTP 30 Weekly average 400;
monthly average 200
%[
%[%[
%[
4 0 4 8 Miles
Waterbodies
Streams
Salem Creek Impaired Length
%[NPDES Dischargers
Salem Creek HUC
N
EW
S
Figure 3.1. NPDES Facility Locations in the Salem Creek Watershed.
NC0085871
NC0079821
NC0080853
NC0037834
15
3.1.2 NPDES General Permits
All single family residences or domestic treatment facilities that discharge wastewaters not
exceeding 1,000 gallons per day in the Salem Creek watershed are subject to NC general permit
NCG550000 and as such are required to not cause or contribute to violations of water quality
standards. Monitoring requirements for these facilities are outlined in Part I (page 2) of
NCG550000 (http://h2o.enr.state.nc.us/NPDES/documents/NCG55_Permit_2002.pdf). A brief
statement of maintenance activities is presented in Section 2.2.2.
3.1.3 NPDES Stormwater MS4s
Winston-Salem is under the Phase I MS4 stormwater permit. Walkertown and Kernersville are
both identified under the second phase of the federal stormwater regulations. Therefore, all the
nonpoint source loading from the watershed area that is inside the incorporated boundaries of the
cities of Winston-Salem, Walkertown, and Kernersville, as well as all urban areas inside the zone
of influence, are included in the WLA section of the TMDL.
3.1.4 Livestock Populations
The North Carolina Department of Agriculture (NCDA) regularly performs an agricultural
census for each county of the state. This census includes estimated livestock populations in each
county, as shown in Table 3.2 for the Salem Creek watershed.
Table 3.2. Estimated Livestock population in the Salem Creek watershed.
Livestock Date data is valid
from
Number
Hogs and Pigs Dec. 1, 2003 No Data
Cattle Jan 1, 2004 5,100
Beef Cows Jan 1, 2004 2,800
Milk Cows Jan 1, 2004 No Data
Broilers Produced 2003 No Data
Turkeys Raised 2003 No Data
All Chickens Dec. 1, 2003 No Data
Source: http://www.ncagr.com/stats/cntysumm/forsyth.htm
3.1.5 Septic Tanks
Septic tanks and cesspools can contribute to the nonpoint sources of fecal coliform found in
Salem Creek. More information is provided in Table 3.3.
16
Table 3.3. Estimated Housing Units Using Septic Systems in the Salem Creek Watershed.
County Number of Housing
Units
Number of Septic
Tank or Cesspool
Systems
Percentage of
Housing Units with
Septic Tank or
Cesspool Systems
Forsyth 138,573; 2002 37,913 27%
Source for Septic Tank and Cesspool System data:
http://factfinder.census.gov/servlet/QTTable?_bm=n&_lang=en&qr_name=DEC_1990_STF3_DP5&ds_
name=DEC_1990_STF3_&geo_id=05000US37067
Source for Housing Unit data:
http://quickfacts.census.gov/qfd/states/37/37067.html
3.2 Technical Approach
Based on the above information, both point and nonpoint sources contribute fecal coliform to
Salem Creek. Because of the size of Salem Creek, the amount of fecal coliform data, and the
type of flow data available, a load duration approach has been adopted for this study. This
approach determines impaired loads under different flow conditions – high flow, transition flow,
typical flow, and low flow – to identify source types, specify assimilative capacity of a stream,
and to estimate magnitude of load reduction required to meet the water quality standard. The
methodology used to develop a load duration curve was based on Cleland (2002).
3.2.1 Endpoint for Fecal Coliform
The TMDL objectives require the instream fecal coliform concentrations to meet both the
instantaneous standard of 400 cfu/100ml and the geometric mean standard of 200 cfu/100ml.
Data is not collected in Salem Creek often enough for the geometric mean standard to apply,
therefore only the instantaneous standard is used as the endpoint for the fecal coliform TMDL in
the creek. It is assumed that if the instantaneous standard is met, it will follow that the geometric
mean standard will also be met.
3.2.2 Flow Duration Curve
Development of a flow duration curve is the first step of the load duration approach. A flow
duration curve employs a cumulative frequency distribution of measured daily stream flow over
the period of record. The curve relates flow values measured at the monitoring station to the
percent of time the flow values were equaled or exceeded. Flows are ranked from lowest, which
exceed nearly 100 percent of the time, to highest, which exceed less than 1 percent of the time.
Reliability of the flow duration curve depends on the period of record available at monitoring
stations. Predictability of the curve increases when longer periods of record are used.
Unfortunately, there is no currently operating flow gage in Salem Creek. Thus, daily flow data
from USGS Gaging Station #02095000, on South Buffalo Creek near Greensboro, North
Carolina, was used to establish the historic flow regimes and define ranges for the high, typical,
and low flow conditions, from measured flow data from August 1998 to September 2004.
17
Flows at the downstream Salem Creek ambient station were estimated based on the drainage area
ratio (2.085) between USGS station #02095000 and the watershed area upstream of the Salem
Creek ambient station (i.e. Salem Creek drainage area is 2.085 times larger than South Buffalo
Creek drainage area). Flows were also adjusted to account for point sources in each watershed
by subtracting all reported NPDES point source flows discharging in the South Buffalo Creek
watershed before calculating the estimated flow in Salem Creek. After the drainage area ratio for
the flows was calculated, the NPDES point source flows in Salem Creek were added on.
The following method was used to estimate NPDES point source flows in Salem Creek. Because
TMDL allocations are based on permitted flows, the permitted flow for Archie Elledge WWTP
(30 million gallons per day (MGD)) was used as a constant flow for this facility. This is the only
facility with a permitted flow limit in this watershed. The reported monthly average flows for
the other three NPDES facilities were used to complete the total NPDES flow addition for Salem
Creek.
Flow statistics as generated by the curves from the estimated flow data are presented in Table
3.4.
Table 3.4. Flow Statistics for estimated Salem Creek at ambient station Q2570000
High Flow (<10th
Percentile)
Transitional Flow
(Between 10th and 30th
Percentile)
Typical Flow
(Between 30th and 90th
Percentile)
Low Flow (>90th
Percentile)
278 – 4786 cfs 99 – 278 cfs 54 – 99 cfs 48 – 54 cfs
The flow duration curve, shown in Figure 3.2, was used to determine the seasonality and flow
regimes during which the exceedances of the pollutants occurred. It was also used to determine
maximum daily pollutant load based on the flow duration and applicable standard. The
applications of the flow duration curve for Salem Creek are discussed in the following
paragraphs.
Flow Duration Curve for Salem Creek at Station Q2570000
1
10
100
1000
10000
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Percent of Days Flow Exceeded
Da
i
l
y
S
t
r
e
a
m
f
l
o
w
(
c
f
s
)
)
High Trans Flow Typical Flow Low
Flow Flow
Figure 3.2. Flow Duration Curve for Salem Creek at Station Q2570000.
18
3.2.3 Load Duration Curve
A load duration curve is developed by multiplying the flow values along the flow duration curve
by the pollutant concentrations and the appropriate conversion factors. As seen in Figure 3.3,
allowable and existing loads are plotted against the flow recurrence interval. The allowable load
is based on the water quality numerical criteria, margin of safety, and flow duration curve. The
target line is represented by the line drawn through the allowable load data points and hence, it
determines the assimilative capacity of a stream or river under different flow conditions. Any
values above the line are exceeded loads and the values below the line are acceptable loads.
Therefore, a load duration curve can help define the flow regime during which exceedances
occur. Exceedances that occur during low-flow events are likely caused by continuous or point
source discharges, which are generally diluted during storm events. Exceedances that occur
during high-flow events are generally driven by storm-event runoff. A combination of point and
nonpoint sources may cause exceedances during normal flows.
The following paragraphs discuss procedures to estimate endpoints for fecal coliform in Salem
Creek in order to identify assimilative capacity of the river in each flow condition and to identify
the flow regime during which exceedances occur.
The fecal coliform assessment also used the load duration curve approach to determine existing
load and assimilative capacity. As stated in Section 3.2.1, analysis was performed for the
instantaneous standard of 400 counts / 100ml to determine the most conservative measure of
impairment. Figure 3.3 presents the calculated loads and the TMDL target loadings for fecal
coliform.
In Salem Creek, the criteria violations seem to have occurred at all ranges of flows, suggesting
that contamination due to fecal coliform occurred during both wet and dry weather conditions.
The combined wet and dry contamination suggests sources from both point and nonpoint, as in
sewer pipe leakage, failing septic systems, direct pipelines, and sanitary sewer overflows, for
example. In the report, (Maptech-HDR 2005) analysis indicates that humans, pets, livestock, and
wildlife all contribute fecal coliform to Salem Creek.
19
Load Duration Curve for Salem Creek @ Sta. Q2570000
1.00E+08
1.00E+09
1.00E+10
1.00E+11
1.00E+12
1.00E+13
1.00E+14
1.00E+15
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Percent of Days Flow Exceeded
Lo
a
d
(
c
f
u
/
d
a
y
)
:
Allowable Load w/ MOS Measured Load
Figure 3.3. Fecal coliform load duration curve for Salem Creek at station Q2570000, from
August 1998 through September 2004.
3.3 Total Maximum Daily Load (TMDL)
Section 3.2 described the processes and rationale to identify the endpoints, assimilative capacity,
potential sources, and target loadings for each pollutant in the Salem Creek watershed. These
efforts formed the basis for the TMDL process. The following sections describe the key
components required by the TMDL guidelines to set the final TMDL allocation for the
watershed.
Total Maximum Daily Load (TMDL) can be defined as the total amount of pollutant that can be
assimilated by the receiving water body while achieving water quality standards. A TMDL can
be expressed as the sum of all point source loads (WLAs), nonpoint source loads (LAs), and an
appropriate margin of safety (MOS), which takes into account any uncertainty concerning the
relationship between effluence limitations and water quality. This definition can be expressed by
equation 3.1:
∑∑++=MOSLAsWLAsTMDL (3.1)
The objective of the TMDL is to estimate allowable pollutant loads and to allocate the known
pollutant source in the watershed in order to implement control measures and to achieve water
quality standards. 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. For fecal
coliform contamination, TMDLs are expressed as counts, or colony forming units (cfu), per 100
milliliters. TMDLs represent the maximum one-day load the stream can assimilate and maintain
the water quality criterion. A load duration curve approach was utilized to estimate the TMDL
for fecal coliform. The systematic procedures adopted to estimate TMDLs are described below.
20
3.3.1 Margin of Safety (MOS)
The MOS is included in the TMDL estimation to account for the uncertainty in the simulated
relationship between the pollutants and the water quality standard. In this study, the MOS was
explicitly included in following TMDL analysis by setting the TMDL target at 10 percent lower
than the water quality target for fecal coliform. The water quality standard and the explicit
margin of safety can be seen in Table 3.5.
Table 3.5. Water Quality Standard and Explicit Margin of Safety.
Standard for Fecal
Coliform 400 cfu/100 ml
Standard for Fecal
Coliform with 10% MOS 360 cfu/100 ml
3.3.2 Target Reduction
The reduction for the instantaneous fecal coliform standard was estimated with the observed data
that exceeded the applicable water quality standard (400 cfu/100 ml) within the 10th to 95th
percentile flow recurrence range. The reduction for the geometric mean was not estimated,
because fecal coliform violation at the water quality standard, 200 cfu/100 ml, was not observed
(see §3.2.1).
A power curve equation for the data points violating the water quality criterion was estimated.
The equation is presented in Equation 3.2. The coefficient of determination, R2, for the equation
is 0.72; thus suggesting a reasonable fit of the equation.
Y = 7.69E11 * X-1.66 R2 = 0.72 (3.2)
Where, Y = fecal coliform (cfu/100ml) and X = Percent Flow Exceeded.
To present the TMDLs as a single value, the existing load was calculated from the power curve
equation as the average of the load violations occurring when the flow (or load) exceeded at a
frequency greater than 10 percent and less than 95 percent. Additionally, the average load was
calculated by using percent flow exceedances in multiples of 5 percent. The allowable loadings
for each exceedance were calculated from the TMDL target value, which includes the 10 percent
MOS. The target curve based on the allowable load and the power curve based on the
exceedances are shown in Figure 3.4.
The necessary percent reduction was calculated by taking the difference between the average of
the power curve load estimates and the average of the allowable load estimates. For example, at
each recurrence interval between 10 and 95 (again using recurrence intervals in multiple of 5),
the equation of the power curve was used to estimate the existing load. The allowable load was
then calculated in a similar fashion by substituting the allowable load curve. The estimated
values are given in Appendix Table A.2.
21
Load Duration Curve for Salem Creek @ Sta. Q2570000
1.00E+08
1.00E+09
1.00E+10
1.00E+11
1.00E+12
1.00E+13
1.00E+14
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Percent of Days Flow Exceeded
Lo
a
d
(
c
f
u
/
d
a
y
)
:
Allowable Load w/MOS Measured Exceeding Load Power (Measured Exceeding Load)
Figure 3.4. Load Duration Curve with Allowable and Estimated Exceeding Loads of Fecal
Coliform in Salem Creek at station Q2570000.
3.3.3 TMDL Allocation
As identified by the above load duration curve method, a significant reduction of fecal coliform
is required in Salem Creek. A summary of reductions required is provided in Table 3.6 (also, see
Appendix Table A.2), where the # symbol represents colony forming units (cfu) or counts.
Table 3.6. Reduction required for Fecal Coliform.
Pollutant Target with MOS Estimated
Exceeding
Load
TMDL
(Allowable Load + MOS)
Reduction
Required
Fecal Coliform1 <360 cfu/100ml 5.74E12 #/day 9.14E11 #/day 84.1%
1Instantaneous measurement of fecal coliform is used.
In order to meet the TMDL objectives, the reduction should be distributed over both MS4 and
nonpoint sources. Bacteria Source Tracking (BST) indicates a variety of sources are contributing
fecal coliform to Salem Creek, including humans, pets, wildlife, and livestock (MapTech-HDR.
2005). However, BST provides information regarding sources and not the mode of delivery (i.e.
point or nonpoint). A further analysis is therefore required to determine the breakdown between
point and nonpoint source loadings. To accomplish this, data from the MapTech-HDR study was
plotted with a load duration curve for station Q2510000, as shown in Figure 3.5. It is important
to note that the TMDL is not established at this station, as this is not the most downstream
station. Rather, this analysis is used for informational purposes only. The MapTech-HDR study
did not sample at station Q2570000.
The MapTech-HDR study took place at DWQ station Q2510000 on Salem Creek (see Figure
1.6). Station Q2510000 is upstream of station Q2570000; therefore a new load duration curve
22
was established for station Q2510000 using the same method described in Section 3.2.2. For this
study, fecal coliform was analyzed to determine the relative contribution from four sources:
livestock, wildlife, human, or pets. In Figure 3.5, each data point was then assigned to one of the
four sources based on the source with the highest percentage contribution. So, those points
shown as livestock in Figure 3.5 indicate that livestock was the primary contributor, not the sole
contributor.
Load Duration Curve for Salem Creek @ Sta. Q2510000
1.00E+08
1.00E+09
1.00E+10
1.00E+11
1.00E+12
1.00E+13
1.00E+14
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Percent of Days Flow Exceeded
Lo
a
d
(
c
f
u
/
d
a
y
)
.
Allowable Load w/ MOS Human
Livestock Pets
Wildlife
Figure 3.5. Load Duration Curve for data collected during MapTech-HDR study at station
Q2510000.
The results of this analysis, as shown in Figure 3.5, indicate that pets are the least common
source of fecal coliform in Salem Creek. Livestock tends to be the higher contributor during
high flow events, while wildlife and humans are the dominant source during the typical flow
period.
3.3.3.1. Waste Load Allocation (WLA)
All fecal coliform transported from the wastewater facilities and the MS4 areas were assigned to
the WLA components. The relative loading rates from the facilities are listed in Table 3.1. The
relative loading rates from the MS4 areas were determined based on the report by USGS, 1999.
The report describes fecal coliform transports under different land use conditions in the City of
Charlotte and Mecklenburg County, North Carolina. A summary of the report and a description
of the method that was used to estimate relative percent contribution of fecal coliform from the
urban and rural sources for this study are presented in Appendix C.1. The estimated relative
percent contribution from the MS4 and other areas (nonpoint sources including non-MS4 area)
are presented in Table 3.7.
23
Table 3.7. Relative Fecal Coliform Contribution Rates for Salem Creek Watershed.
Pollutant Load from MS4 areas (%) Load from other areas (%)
Fecal Coliform 80 20
The assimilative capacity determined in Section 3.3.2 was split based on the relative
contributions presented in Table 3.7 to determine the allocation for the MS4 areas. The results of
these calculations are summarized in Table 3.8. The resulting percent reduction in fecal coliform
loading from MS4 areas is 93%, as shown in Table 3.9.
3.3.3.2. Load Allocation (LA)
All fecal coliform loadings from nonpoint sources such as non-MS4 urban land, agriculture land,
and forestlands are reported as LAs. The relative loading rates from these areas were determined
using the similar procedures as described in Section 3.3.3.1 (See also Appendix Table C.2). The
estimated relative contributions of fecal coliform from the nonpoint sources are presented in
Table 3.8. The estimated percent reduction from nonpoint sources is 93%, as shown in Table
3.9.
Table 3.8. Estimated TMDL and Load Allocation for Fecal Coliform for the Salem Creek
Watershed.
Pollutant Existing
Load
WLA
NPDES
WLA
MS4
WLA1 LA MOS TMDL2
Fecal
Coliform
(cfu/day)
5.74E12 4.54E11 2.95E11 7.49E11 7.37E10 9.14E10 9.14E11
1. WLA = WLA NPDES + WLA MS4
2. TMDL = WLA + LA + MOS
Table 3.9. Estimated Percent Reduction by Source for Fecal Coliform (shown in cfu/day) for the
Salem Creek Watershed.
WLA
NPDES
WLA MS4 LA MOS TOTAL
Existing Load
(cfu/day)
4.54E11 4.22E12 1.07E12 x 5.74E12
Load Allocation
(cfu/day)
4.54E11 2.95E11 7.37E10 9.14E10 9.14E11
Percent Reduction 0% 93.0% 93.1% x 84.1%
3.3.3.3. Study Limitation
The available land use and land cover data for this study is outdated and does not accurately
represent current land use conditions. Therefore, the estimation of WLA in Table 3.7 is not
authoritative. The estimation helps to provide understanding of the relative loads and should be
viewed in light of the limited data available to quantify the actual contributions from each
individual source. The primary focus of efforts to minimize future impairment should focus on
the percent reductions and control of sources identified in the Source Assessment (see §2).
24
3.3.4 Critical Condition and Seasonal Variation
Critical conditions are considered in the load curve analysis by using an extended period of
stream flow and water quality data, and by examining the flows (percent flow exceeded) where
the existing loads exceed the target line.
Seasonal variation is considered in the development of the TMDLs, because allocation applies to
all seasons. According to the load duration curve (Figure 3.3), the existing load violation for
fecal coliform occurred at all flow conditions throughout the year (Figure 3.4). Therefore, both
dry and wet weathers are critical for fecal coliform.
25
4.0 Grants Creek Impairment
4.1 Source Assessment
A source assessment is used to identify and characterize the known and suspected sources of
turbidity in the Grants Creek watershed. This section outlines the assessment completed for the
purpose of developing this TMDL.
4.1.1 NPDES Wastewater Permits
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 publicly owned
treatment plants (POTPs) and industrial treatment plants. When effluent turbidity 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 five individual NPDES permitted facilities in the Grants Creek watershed.
Information on each facility can be found in Table 4.1. Permit NC0004286 is inactive as of
6/30/2005. The permit was active for the time period used to estimate the flow duration curve,
so flows from this facility are included in the flow estimation for Grants Creek. However, this
facility will not receive a load allocation. Locations of the facilities can be seen in Figure 4.1.
Table 4.1. NPDES Wastewater Permits in the Grants Creek Watershed.
Permit Owner Facility Permitted Flow
(MGD)
TSS (mg/L)
Daily Max
TSS (mg/L)
Monthly Ave
NC0027502 Town of Landis Landis WTP No Limit 45 30
NC0034703 Rowan-Salisbury
Schools
Knollwood
Elementary
School
0.011 45 30
NC0037184 Lakeside Investment
Properties
Oak Haven
Mobile Home
Park
0.006 45 30
NC0042439 Westside Swim &
Racquet Club
Westside Swim &
Racquet Club 0.003 45 30
NC0049905 Inman Asphalt Inman Asphalt-
Salisbury No Limit 67.5 45
NC0004286* Fieldcrest Cannon,
Inc. Plant 16 0.05 135 39
* Permit NC0004286 is inactive as of 6/30/2005 and will not be included in final NPDES load allocations.
26
% [
% [
%
% [
%
% [
W a t e r b o i e s S t r e a s G r a n t s C r e e k % N P D E S D i s c h a r g e r s G r a n t s C r e k W t e r s e d B o u d a r
1 i l e
[
[
d m
[ e a h n y
0 6 2 M s
N
E W
S
Figure 4.1. Locations NPDES Wastewater Permitted Facilities in the Grants Creek Watershed.
4.1.2 NPDES General Permits
All construction activities in the watershed that disturb one or more acres of land are subject to
obtaining a North Carolina NPDES general permit, and as such are required to not cause or
contribute to violations of water quality standards. As stated in Permit NCG010000, page 2,
“The discharges allowed by this General Permit shall not cause or contribute to violations of
Water Quality Standards. Discharges allowed by this permit must meet applicable wetland
standards as outlined in 15A NCAC 2B .0230 and .0231 and water quality certification
requirements as outlined in 15A NCAC 2H .0500”. Monitoring requirements for these
construction activities are outlined in Section B (page 5) of NCG010000. As stated, “All erosion
and sedimentation control facilities shall be inspected by or under the direction of the permittee
at least once every seven calendar days (at least twice every seven days for those facilities
discharging to waters of the State listed on the latest EPA approved 303(d) list for construction
related indicators of impairment such as turbidity or sedimentation) and within 24 hours after any
storm event of greater than 0.5 inches of rain per 24 hour period.” (NCG010000, Section B)
As per 40 CFR § 122.44(d)(1)(vii)(B), where a TMDL has been approved, NPDES permits must
contain effluent limits and conditions consistent with the requirements and assumptions of the
WLA in the TMDL. While effluent limitations are generally expressed numerically, EPA
guidance on NPDES-regulated municipal and small construction storm water discharges is that
NC0049905
NC0042439
NC0037184
NC0027502
NC0004286
NC0034703
27
these effluent limits be expressed as best management practices (BMPs) or other similar
requirements, rather than numeric effluent limits (Wayland, 2002). Compliance with the
turbidity standard in Grants Creek is expected to be met when construction and other land
management activities in the Grants Creek watershed employ adequate BMPs. Upon approval of
this TMDL, DWQ will notify the NC Division of Land Resources (DLR) and other relevant
agencies, including county and local offices in the Grants Creek watershed (Rowan County)
responsible for overseeing construction activities, as to the impaired status of Grants Creek and
the need for a high degree of review in the construction permit review process.
4.1.3 NPDES Stormwater MS4s and other Nonpoint 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). This is further discussed in Section
2.1.2.
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 cities or counties that 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.
The cities of Salisbury, China Grove, and Landis are considered to be under Phase II of the
federal stormwater regulations. Therefore, all the nonpoint source loading from the watershed
area that is inside the incorporated boundaries of these cities, as well as all urban areas not inside
those city boundaries, but still inside the zone of influence are included in the WLA section of
the TMDL.
4.2 Technical Approach
Based on the above information, it is most likely that both point sources and nonpoint sources
contribute turbidity to Grants Creek. Because of the size of Grants Creek, the amount of
turbidity and TSS data, and the type of flow data available, a load duration approach has been
adopted for this study. This approach determines impairment loads under different flow
conditions – high flow, transition flow, typical flow, and low flow – to identify source types,
specify assimilative capacity of a stream, and to estimate the magnitude of load reduction
required to meet the water quality standard. The methodology used to develop a load duration
curve is based on Cleland (2002).
28
4.2.1 Endpoint for Turbidity
As discussed in Section 2.1, turbidity is a measure of cloudiness and is reported in
Nephelometric Turbidity Units (NTU). Therefore, turbidity is not measured in terms of
concentrations and cannot be directly converted into loadings required for developing a load
duration curve. For this reason, total suspended solids (TSS) were selected as a surrogate
measure for this study.
In order to observe the relationship between TSS and turbidity in Grants Creek, a regression
equation between the two parameters was developed using the observed data collected from
January 1997 through December 2004 at ambient stations Q4600000. The coefficient of
determination (R-Square) between the two parameters was 0.8433; therefore, a significant
relationship between the two parameters was experienced. The relationship is shown in Equation
4.1 and Figure 4.2.
TSS (mg/L) = 1.7666 * Turbidity(NTU) – 16.692 R2 = 0.9002 (4.1)
TSS and Turbidity Data for Grants Creek
0
150
300
450
600
750
900
0 50 100 150 200 250 300 350 400
Turbidity (NTU)
TS
S
(
m
g
/
L
)
Figure 4.2. TSS-Turbidity Relationship for Grants Creek.
The standard for turbidity is 50 NTU, which using this equation translates to 71.64 mg/L of TSS.
Using an explicit MOS of ten percent yields a TSS endpoint of 62.81 mg/L, as shown in Table
4.2.
Table 4.2. Endpoint for Turbidity Translated to TSS.
Standard for Turbidity Standard for Turbidity
with 10% MOS
Related Standard for
TSS
Related Standard for
TSS with 10% MOS
50 NTU 45 NTU 71.64 mg/L 62.81 mg/L
29
4.2.2 Flow Duration Curve
A flow duration curve was developed for Grants Creek using a similar procedure as described in
section 3.2.2. Reliability of the flow duration curve depends on the period of record available at
monitoring stations. Predictability of the curve increases when longer periods of record are used.
Unfortunately, there is no currently operating flow gage in Grants Creek. Thus, daily flow data
from USGS Gaging Station #02120780, on Second Creek near Barber, North Carolina, was used
to establish the historic flow regimes and define ranges for the high, typical, and low flow
conditions, from measured flow data from January 1997 to September 2004.
Flows at the downstream Grants Creek ambient station were estimated based on a drainage area
ratio between USGS station #02120780 and the watershed area upstream of the Grants Creek
ambient station. The drainage area ratio between Grants Creek and Second Creek is 0.57;
meaning Grants Creek drainage area is 0.57 times the size of Second Creek. Flows were also
adjusted to account for point sources in each watershed by subtracting all NPDES point source
flows discharging in the Second Creek watershed before calculating the estimated flow in Grants
Creek. After the drainage area ratio for the flows was calculated, the NPDES point sources
flows in Grants Creek were added on using the same method as described in Section 3.2.2. In
this case, permitted flows were used for all NPDES facilities except for NC0027502 because
there is no permitted flow limit for this facility. Flow statistics as generated by the curves from
the estimated flow data are presented in Table 4.3.
Table 4.3. Flow Statistics for estimated Grants Creek at ambient station Q4600000
High Flow (<10th
Percentile)
Transitional Flow
(Between 10th and 30th
Percentile)
Typical Flow
(Between 30th and 90th
Percentile)
Low Flow (>90th
Percentile)
88-2337 cfs 40 – 88 cfs 4 – 40 cfs 0.4 – 4 cfs
The flow duration curve, shown in Figure 4.3, was used to determine the seasonality and flow
regimes during which the exceedances of the pollutants occurred. It was also used to determine
maximum daily pollutant load based on the flow duration and applicable standard. The
applications of the flow duration curve for Grants Creek are discussed in the following
paragraphs.
4.2.3 Load Duration Curve
As discussed in Section 3.2.3, a load duration curve is developed by multiplying the flow values
along the flow duration curve by the pollutant concentrations and the appropriate conversion
factors. As seen in Figure 4.4, allowable and existing loads are plotted against the flow
recurrence interval. The allowable load is based on the water quality numerical criteria, margin
of safety, and flow duration curve.
The following paragraphs discuss procedures to estimate endpoints for turbidity in Grants Creek
in order to identify assimilative capacity of the creek in each flow condition and to identify the
flow regime during which exceedances occur.
30
Flow-Duration Curve for Grants Creek
0.1
1.0
10.0
100.0
1,000.0
10,000.0
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Percent of Days Flow Exceeded
Da
i
l
y
S
t
r
e
a
m
f
l
o
w
(
c
f
s
)
.
High Trans Typical Low
Flow Flow Flow Flow
Figure 4.3. Flow Duration Curve for the Grants Creek Watershed. Flows from Second Creek at
USGS Station #02120780 were used to estimate flows for Grants Creek.
Turbidity Assimilative Capacity
Existing TSS loads to Grants Creek were determined by multiplying the observed TSS
concentration by the flow observed on the date of observation and converting the result to daily
loading values. The assimilative capacities of the water bodies were determined by multiplying
the TSS concentration that is equivalent to a turbidity value of 45 NTU by the full range of
measured flow values. Figure 4.4 presents the TMDL target loading and observed TSS and
turbidity for the creek.
Figure 4.5 shows the same information with the extreme high and low flow loads are cut out.
The bottom five percent and the highest ten percent are cut from the load duration curve.
31
Load-Duration Curve for Grants Creek
1
10
100
1,000
10,000
100,000
1,000,000
10,000,000
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Percent of Days Flow Exceeded
TS
S
L
o
a
d
(
P
o
u
n
d
s
/
D
a
y
)
.
Allowable Load at the Standard (MOS) (#/day)TSS Loads (lbs/day)
Turbidity to TSS loads (lbs/day) Q4600000 Turbidity to TSS loads (lbs/day) Q4540000
Figure 4.4. TSS Load duration curve for Grants Creek stations Q4600000 and Q4540000, from
January 1997 through September 2004.
Load Duration Curve for Grants Creek - Less Extreme Flows
1
10
100
1,000
10,000
100,000
10% 20% 30% 40% 50% 60% 70% 80% 90%
Percent of Days Flow Exceeded
TS
S
L
o
a
d
(
P
o
u
n
d
s
/
d
a
y
)
.
Allowable Load at the Standard (MOS) (#/day)TSS Loads (lbs/day) Q4600000
Turbidity to TSS loads (lbs/day) Q4600000 Turbidity to TSS loads (lbs/day) Q4540000
Figure 4.5. TSS Load duration curve for Grants Creek stations Q4600000 and Q4540000, from
January 1997 through September 2004, less extreme flows.
32
Once the highest ten percent and the lowest five percent flows are removed from the calculation,
there are only five instances of observed load exceeding the target value. The five instances are
spread throughout the curve, in the higher flows, typical flows, and low flows.
4.3 Total Maximum Daily Load (TMDL)
Section 4.2 described the processes and rationale to identify the endpoints, assimilative capacity,
potential sources, and target loadings for TSS and turbidity in the Grants Creek watershed.
These efforts formed the basis for the TMDL process. The key components required by the
TMDL guidelines to set the final TMDL allocation for the watershed are defined by the Equation
4.2.
∑∑++=MOSLAsWLAsTMDL (4.2)
Where, WLA is waste load allocation (point source), LA is load allocation (nonpoint source),
and MOS is margin of safety. A detailed explanation of the equation is given in Section 3.3.
The following sections describe the key components required by the TMDL guidelines to set the
final TMDL allocation for the Watershed.
4.3.1 Margin of Safety (MOS)
The Margin of Safety was explicitly included in following TMDL analysis by setting the TMDL
target at 10 percent lower than the water quality target for turbidity. Details of the MOS can be
found in Table 4.2.
4.3.2 Target Reduction
To determine the amount of turbidity reduction necessary to comply with the water quality
criteria, exceedances of the estimated standard (71.64 mg TSS/L) were identified within the 10th
to 95th percentile flow recurrence range. A power curve through the data point violating the
water quality criterion was overlaid on the graph (Figure 4.6). The power curve equation is
presented in Equation 4.3. The correlation coefficient, R-Square, for the power curve is 0.61;
thus suggesting a reasonable fit of the curve.
Y = 3857 * X-1.28 R2 = 0.607 (4.3)
33
Load Duration Curve for Grants Creek - Exceedences
1
10
100
1,000
10,000
100,000
10% 20% 30% 40% 50% 60% 70% 80% 90%
Percent of Days Flow Exceeded
TS
S
L
o
a
d
(
P
o
u
n
d
s
/
d
a
y
)
.
Allowable Load at the Standard (MOS) (#/day)
Exceeding Load
Power (Exceeding Load)
Figure 4.6. Load duration curve showing allowable, existing loads violation, and the power
curve of exceeding loads in Grants Creek.
The criteria violations occurred throughout the typical flow regime (Figure 4.4). As described in
Section 3.3, the loading estimates based on the power curve are presented in Appendix Table
B.2. Approximately 31 percent reduction in TSS is required in order to meet the water quality
standard and to account for the 10 percent of MOS. A summary of reductions required is
provided in Table 4.4.
Table 4.4. Reduction Required for TSS in Grants Creek.
Pollutant Target with MOS Estimated
Exceeding Load
TMDL
(Allowable Load
+ MOS)
Reduction
Required
TSS1 <71.64 mg/L 8.03 tons/day 5.54 tons/day 31.0%
1TSS is used as a surrogate variable for turbidity.
4.3.3 TMDL Allocation
As identified by the above load duration curve method, significant amounts of TSS are required
to be reduced in Grants Creek. In order to meet the TMDL objectives, the reduction should be
targeted towards nonpoint sources and MS4 areas.
4.3.3.1. Waste Load Allocation (WLA)
All TSS transported from the MS4 areas and NPDES permitted facilities were assigned to the
WLA components. The loading rates from the NPDES facilities are listed in Table 4.1. The
total allocation for NPDES permitted facilities is 0.0038 tons/day, as shown in Table 4.6. There
are no load allocations for permits NC0049905 or NC0027502 because there is no permitted
34
flow limit. There is also no load allocation for permit NC0004286 because this permit is no
longer active (as of 6/30/2005).
The relative loading rates from the MS4 areas were determined based on the report by USGS,
1999. The report describes TSS and sediment transport under different land use conditions in the
City of Charlotte and Mecklenburg County, North Carolina. A summary of the report and a
description of the method used to estimate the relative percent contribution of TSS from the
urban and rural sources for this study are presented in Appendix Table C.1. The estimated
relative percent contribution from the MS4 and other areas (nonpoint sources including non-MS4
area) are presented in Table 4.5. Section 4.1.3 describes which areas of the Grants Creek
watershed are considered MS4.
Table 4.5. Relative TSS contributions Rates for the Grants Creek watershed.
Pollutant Load from MS4 areas (%) Load from other areas (%)
TSS 14 86
The assimilative capacity determined in Section 4.2.3 was split based on the relative
contributions presented in Table 4.5 to determine the allocation for the MS4 areas. The results of
these calculations are summarized in Table 4.6. As shown in Table 4.7, the load allocation for
MS4 areas represents a 39.5% reduction in TSS loading.
The WLA associated with construction and other land management activities, as discussed in
Section 4.1.2, is equivalent to the surface water quality standard for turbidity in that any
construction activity cannot cause or contribute to a violation of the water quality standard. As
discussed, these WLAs are and will be expressed as BMPs in the general or individual
construction permits rather than as numeric effluent limits.
4.3.3.2. Load Allocation (LA)
All TSS loadings from nonpoint sources such as non-MS4 urban land, agriculture land, and
forested land were reported as LAs. The relative loading rates from these areas were determined
using the similar procedures as described in Section 3.3.2. (See also Appendix Table C.3.) The
estimated allocation of TSS from the nonpoint sources is presented in Table 4.6. As shown in
Table 4.7, the allocation for nonpoint sources requires a 39.5% reduction in nonpoint source
loading.
Table 4.6. Estimated TMDL and Load Allocation for TSS for the Grants Creek Watershed.
Pollutant Existing
Load
WLA
NPDES
WLA
MS4
WLA1 LA MOS TMDL2
TSS
(tons/day)
8.03 0.0038 0.68 0.68 4.17 0.68 5.54
1. WLA = WLA NPDES + WLA MS4
2. TMDL = WLA + LA + MOS
35
Table 4.7. Estimated Percent Reduction by Source for TSS in the Grants Creek Watershed.
WLA
NPDES
WLA MS4 LA MOS TOTAL
Existing Load
(tons/day)
0.0038 1.12 6.90 x 8.03
Load Allocation
(tons/day)
0.0038 0.68 4.17 0.68 5.54
Percent Reduction 0% 39.5% 39.5% x 31.0%
4.3.3.3. Study Limitation
The available land cover for this study is outdated and fails to represent current land use
conditions. Therefore, the estimation of WLA in Table 4.7 is not authoritative. The primary
focus of efforts to minimize future impairment should be on the percent reductions and control of
sources identified in the Source Assessment (see § 4.1).
4.3.4 Critical Condition and Seasonal Variation
According to the load duration curve (Figure 4.4), the greatest frequency of exceedances of
turbidity occurred during both high-flow and low-flow periods throughout the season. The
results show that the few exceedances that did occur happened at both high and low flow,
therefore the entire spectrum of flows are critical.
36
5.0 Summary and Future Consideration
This report presents the development of Total Maximum Daily Loads (TMDLs) for two
waterbodies in North Carolina: Salem Creek and Grants Creek both of which are located in the
Yadkin Pee-Dee River Basin. Salem Creek is impaired for fecal coliform and Grants Creek is
impaired for turbidity.
Available water quality data were reviewed to determine the critical periods and the sources that
lead to exceedances of the standard. The necessary percent reduction to meet the TMDL
requirement was then calculated by taking a difference between the average of the power curve
load estimates and the average of the allowable load estimates. The summary of the results is as
follows:
• About 84 percent reduction in fecal coliform is required in order to meet the water quality
standard in Salem Creek. Both point and nonpoint sources from a variety of origins are
responsible for the exceedance of fecal coliform.
• About 31 percent reduction in TSS is required in order to meet the water quality standard
for turbidity in Grants Creek. Both point and nonpoint sources are responsible for the
exceedance of TSS.
5.1 Stream Monitoring
Stream monitoring should continue on a monthly interval at the existing ambient monitoring
stations. The continued monitoring of TSS and fecal coliform will allow for the evaluation of
progress towards the goal of reaching water quality standards by comparing the instream data to
the TMDL target. In addition, every monitoring station should monitor both turbidity and TSS
so a relationship between the two can be determined at every station.
Furthermore, to comply with EPA guidance, North Carolina may adopt new bacteria standards
utilizing Escherichia coli (E. coli) or enterococci in the near future. Thus, in the future,
monitoring efforts to measure compliance with this TMDL should include using E. coli or
enterococci. Per EPA recommendations (EPA, 2000b), if future monitoring for E.
coli/enterococci indicates the standard has not been exceeded, these monitoring data may be used
to support delisting the water body from the 303(d) list. If a continuing problem is identified
using E. coli/enterococci, the TMDL may be revised.
5.2 Implementation Plan
Reductions for fecal coliform should be sought through identification and repair of aging sewer
infrastructure as well as targeting other storm-driven sources. Enforcement of stormwater BMP
requirements for construction sites, additional education related to farming practices and other
37
land disturbing activities, and additional urban stormwater controls for sediment are potential
management options for improving turbidity levels.
For turbidity, much of the impairment is likely due to erosion from land uses during conversion
from rural to urban uses. While stormwater controls are typically required during development
activities, significant loadings can occur due to initial periods of land disturbance before controls
are in place or during high rainfall periods during which the controls are inadequate. Additional
turbidity impairment may be due to runoff from agricultural areas and from erosion of soils due
to increased imperviousness in urbanizing areas.
The TMDL analysis was performed using the best data available to specify the fecal coliform
and total suspended solids reductions necessary to achieve water quality criteria. The intent of
meeting the criteria is to support the designated use classifications in the watershed. A detailed
implementation plan is not included in this TMDL. The involvement of local governments and
agencies will be needed in order to develop an implementation plan.
38
6.0 Public Participation
A draft of the TMDL was publicly noticed through various means. The TMDL was public
noticed in the relevant counties through two local newspapers (Salisbury Post on May 3, 2006
and Winston-Salem Journal on May 4, 2006, Appendix D). The TMDL was also public noticed
on May 1, 2006 through the North Carolina Water Resources Research Institute email list-serve
(Appendix D). Finally, the TMDL was available on DWQ’s website
http://h2o.enr.state.nc.us/tmdl/ during the comment period. The public comment period lasted
until June 2, 2006. Two written comments were received, both from NC Department of
Transportation. DWQ’s responses to those comments are provided in Appendix E.
39
7.0 References
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.
Hyer, Kenneth, Doughlas Moyer, and Trisha Baldwin. 2001. Bacteria Source Tracking to
Improve TMDL Development in Bacteria. U.S. Geological Survey, WRD, 1730 East Parham
Rd., Richmond, VA 23228. In va.water.usgs.gov/GLOBAL/posters/BST.pdf.
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
MapTech-HDR. (2005). Pathogen Source Assessment for TMDL Development and
Implementation in Salem and Muddy Creek Watersheds Winston-Salem, North Carolina.
Prepared for North Carolina Division of Water Quality.
North Carolina Division of Water Quality. (2005). Total Maximum Daily Load for Turbidity and
Fecal Coliform for Haw River, Deep River, Third Fork Creek, and Dan River in North Carolina.
Final Report.
North Carolina Division of Water Quality. (2004). Total Maximum Daily Load for Turbidity for
Fourth Creek (Subbasin 03-07-06) and Yadkin River Basin. Final Report.
North Carolina Division of Water Quality. 2004. Stormwater Permitting Unit. Online:
http://h2o.enr.state.nc.us/su/PDF_Files/SW_General_Permits/NCG010000.pdf
North Carolina Division of Water Quality. 2004. Stormwater Permitting Unit. Online:
(http://h2o.enr.state.nc.us/NPDES/documents/NCG55_Permit_2002.pdf).
North Carolina Department of Agriculture (NCDA):
http://www.ncagr.com/stats/cntysumm/forsyth.htm
U.S. Environmental Protection Agency (USEPA). 1991. Guidance for Water Quality-Based
Decisions: The TMDL Process. Assessment and Watershed Protection Division, Washington,
DC.
U.S. Environmental Protection Agency (USEPA) 1998. Draft Final TMDL Federal Advisory
Committee Report. U.S. Environmental Protection Agency, Federal Advisory Committee
(FACA). Draft final TMDL Federal Advisory Committee Report. 4/28/98.
U.S. Environmental Protection Agency (USEPA) 1999. Protocol for Developing Sediment
TMDLs. First Edition. EPA 841-B-99-044. U.S. EPA, Office of Water, Washington D.C.
40
U.S. Environmental Protection Agency (USEPA) 2000a. 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). 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).
U.S. Census Bureau: http://quickfacts.census.gov/qfd/states/
U.S. Census Bureau:
http://factfinder.census.gov/servlet/QTTable?_bm=n&_lang=en&qr_name=DEC_1990_STF3_D
P5&ds_name=DEC_1990_STF3_&geo_id=05000US37067
U.S. Census Bureau: http://quickfacts.census.gov/qfd/states/37/37067.html
U. S. Geological Survey (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. November 22, 2002. Memorandum from Rober Wayland of the U. S.
Environmental Protection Agency to Water Division Directors. Subject: Establishing TMDL
Waste Load Allocation for stormwater sources and NPDES permit requirements based on those
allocations.
41
Appendix A: Salem Creek Data
Table A.1. Water Quality Data for Salem Creek at Station Q2570000.
11/13/2001 130 B
12/4/2001 530 Date
Fecal
Coliform
(cfu/100ml)
Fecal
Coliform
Remarks1 1/15/2002 340
8/4/1998 420 B 2/12/2002 190
9/2/1998 6000 L 3/5/2002 61
10/21/1998 390 4/9/2002 210
11/12/1998 600 5/7/2002 520
12/4/1998 506 6/11/2002 76 B
1/7/1999 170 7/9/2002 63
2/10/1999 77 B 8/6/2002 88 B4
3/11/1999 35 B 9/10/2002 180
4/8/1999 110 B 9/12/2002 230 B4
5/6/1999 500 B 9/17/2002 1100
6/9/1999 770 B 9/19/2002 1700 B6
7/15/1999 300 9/24/2002 300 B4
8/4/1999 160 9/24/2002 410
9/15/1999 2500 10/1/2002 260 B4
10/14/1999 4200 10/8/2002 280 B4
11/4/1999 600 10/8/2002 390
12/9/1999 160 10/15/2002 330 B4
1/13/2000 320 10/22/2002 4900 B3
2/14/2000 3800 11/5/2002 120
3/20/2000 5000 12/3/2002 230
4/27/2000 320 1/7/2003 125 B4
5/3/2000 240 1/16/2003 110
6/15/2000 6000 P 1/28/2003 57
7/19/2000 330 1/30/2003 1600
8/31/2000 5000 2/6/2003 3600 B3
9/12/2000 360 2/11/2003 137 B4
10/23/2000 100 B 2/12/2003 1900
11/13/2000 110 3/18/2003 440
12/26/2000 150 B 4/8/2003 240
1/22/2001 71 B 5/13/2003 260
2/12/2001 72 B 6/10/2003 230
3/21/2001 1400 B 7/15/2003 62
4/9/2001 50 8/26/2003 310
5/14/2001 500 9/23/2003 1600 B1
6/6/2001 370 10/28/2003 1900 B1
7/17/2001 43 11/18/2003 74
8/7/2001 470 12/9/2003 140 B4
9/11/2001 68 1/13/2004 123 B4
10/9/2001 1800 2/10/2004 270
42
1. Fecal Coliform Remark Codes:
B Results based upon colony counts outside the acceptable range.
B1 Countable membranes with less than 20 colonies. Reported value is estimated or is a total of the counts on
all filters reported per 100 ml.
B3 Countable membranes with more than 60 or 80 colonies. The value reported is calculated using the count
from the smallest volume filtered and reported as a greater than ">" value.
B4 Filters have counts of both >60 or 80 and <20. Reported value is a total of the counts from all countable
filters reported per 100 ml.
B6 Estimated Value. Blank contamination evident.
L Actual value is known to be greater than value given.
P Too numerous to count.
Table A.2. Estimation of Load Reduction Required in Fecal Coliform for Salem Creek at Station
Q2570000
% Flow
Exceeded Flow (cfs)
Estimated
Exceedance
Load (cfu/day)
TMDL
(cfu/day)
10% 278.39 3.54E+13 2.72E+12
15% 180.91 1.80E+13 1.77E+12
20% 136.81 1.12E+13 1.34E+12
25% 111.96 7.72E+12 1.1E+12
30% 99.24 5.70E+12 9.71E+11
35% 89.53 4.41E+12 8.76E+11
40% 83.20 3.53E+12 8.14E+11
45% 78.65 2.90E+12 7.7E+11
50% 74.61 2.44E+12 7.3E+11
55% 70.79 2.08E+12 6.93E+11
60% 67.82 1.80E+12 6.64E+11
65% 65.80 1.58E+12 6.44E+11
70% 62.67 1.39E+12 6.13E+11
75% 60.80 1.24E+12 5.95E+11
80% 58.83 1.12E+12 5.76E+11
85% 55.94 1.01E+12 5.47E+11
90% 53.71 9.17E+11 5.26E+11
95% 51.47 8.38E+11 5.04E+11
Average 5.74E+12 9.14E+11
Avg. Reduction Required 84.1%
43
Appendix B: Grants Creek Data
Table B.1. Water Quality Data for Grants Creek at Stations Q4600000 andQ4540000
Station Q4600000 Station Q4540000
Date
Residue total
nonfilterable
(mg/L)
Turbidity lab
(NTU) Date Turbidity lab
(NTU)
1/16/1997 250 210 6/3/1998 21.00
2/19/1997 24 22 7/16/1998 5.40
3/18/1997 18 17 8/4/1998 3.40
4/14/1997 9/2/1998 4.50
5/21/1997 8 9.9 10/21/1998 6.70
6/19/1997 2 15 11/12/1998 3.20
7/28/1997 13 12 12/4/1998 4.60
8/19/1997 8.9 1/7/1999 20.20
9/17/1997 6 5.6 2/10/1999 13.50
10/22/1997 7 9.1 3/11/1999 8.80
11/17/1997 6 8.7 4/8/1999 6.20
12/11/1997 4 10 5/6/1999 12.80
1/13/1998 13 24 6/9/1999 11.70
2/12/1998 9 24 7/15/1999 8.70
3/10/1998 29 60 8/4/1999 8.30
4/7/1998 8 8.7 9/15/1999 9.60
5/6/1998 20 65 10/14/1999 17.30
6/8/1998 9 7.6 11/4/1999 7.50
7/9/1998 4 7.3 12/9/1999 8.20
8/5/1998 6 5.6 1/13/2000 38.00
9/17/1998 5 4.5 2/14/2000 407.00
10/8/1998 8 6 3/20/2000 474.00
11/2/1998 1 2.1 4/27/2000 15.50
12/15/1998 8 12 5/4/2000 24.20
1/7/1999 8 19 6/15/2000 94.50
2/15/1999 2 11 7/19/2000 20.50
3/11/1999 5 7.2 8/29/2000 20.30
4/13/1999 4 5.5 9/12/2000 16.30
5/10/1999 12 12 10/23/2000 4.21
6/21/1999 4 13 11/13/2000 2.50
8/2/1999 7 11 12/26/2000 8.50
8/24/1999 3 10 1/22/2001 22.00
9/27/1999 14 12 2/12/2001 12.00
10/25/1999 4 4 3/21/2001 190.00
11/15/1999 4 5.3 4/9/2001 12.00
12/16/1999 4 18 5/14/2001 6.60
44
Station Q4600000 Station Q4540000
Date
Residue total
nonfilterable
(mg/L)
Turbidity lab
(NTU) Date Turbidity lab
(NTU)
2/15/2000 39 65 6/6/2001 6.10
3/13/2000 4 7.8 7/17/2001 7.80
4/17/2000 15 19 8/7/2001 6.50
5/15/2000 6 7 9/11/2001 7.20
6/7/2000 8 10 10/9/2001 20.00
7/24/2000 130 130 11/13/2001 2.70
8/15/2000 64 29 12/4/2001 3.50
9/12/2000 6.6 1/15/2002 7.00
10/5/2000 1 5 2/12/2002 13.00
11/6/2000 4.3 3/5/2002 26.00
12/11/2000 5.8 4/9/2002 7.00
1/17/2001 1 5.8 5/7/2002 6.90
2/12/2001 15 6/11/2002 26.00
4/17/2001 14 7/9/2002 8.00
5/23/2001 110 8/6/2002 17.00
6/25/2001 33 9/24/2002 4.50
7/25/2001 10 12 10/8/2002 5.40
8/13/2001 32 11/5/2002 4.30
9/13/2001 6.3 12/3/2002 6.10
10/9/2001 3 2.6 1/7/2003 12.00
11/28/2001 8.3 2/11/2003 6.10
12/27/2001 9.4 3/18/2003 36.00
1/23/2002 820 380 4/8/2003 70.00
2/27/2002 6.8 5/13/2003 10.00
3/20/2002 28 6/10/2003 32.00
4/24/2002 13 16 7/15/2003 8.20
5/23/2002 10 8/26/2003 11.00
6/17/2002 9 9/23/2003 120.00
7/30/2002 4 6.5 10/28/2003 13.00
8/26/2002 13 11/18/2003 5.20
9/16/2002 22 12/9/2003 6.60
10/23/2002 4 9 1/13/2004 13.00
11/19/2002 24 2/10/2004 31.00
12/16/2002 50
1/27/2003 4 7.5
2/20/2003 17
3/17/2003 75
4/7/2003 250 210
5/6/2003 110
6/19/2003 29
7/14/2003 14 17
45
Station Q4600000
Date
Residue total
nonfilterable
(mg/L)
Turbidity lab
(NTU)
8/18/2003 19
9/23/2003
10/7/2003 4 8.5
11/5/2003 6.2
12/2/2003 7.6
1/7/2004 8 13
2/5/2004 16
3/23/2004 9
4/14/2004 120 50
5/18/2004 22
6/30/2004 14
7/12/2004 4 7.6
8/9/2004 12
9/13/2004 12
11/2/2004 9.6
12/6/2004 7.1
46
Table B.2. Estimation of Load Reduction Required in TSS for Grants Creek.
% Flow
Exceeded Flow (cfs)
Estimated
Exceedance Load
(lb/day)
TMDL (lb/day) =
allowable + MOS
10% 88.01 73,841.5 34,020.61
15% 66.67 43,908.8 25,774.33
20% 55.09 30,365.5 21,295.25
25% 47.37 22,810.8 18,312.63
30% 40.21 18,056.4 15,544.69
35% 35.65 14,818.5 13,779.49
40% 32.64 12,487.0 12,618.33
45% 28.99 10,737.0 11,205.50
50% 24.76 9,380.4 9,571.71
55% 20.70 8,301.5 8,003.35
60% 17.18 7,425.2 6,640.42
65% 14.78 6,701.1 5,715.31
70% 12.24 6,093.7 4,730.58
75% 10.36 5,577.9 4,003.25
80% 8.38 5,135.0 3,240.78
85% 6.22 4,751.0 2,404.51
90% 4.42 4,415.3 1,709.55
95% 2.36 4,119.6 912.08
Average 16,051.5 11,082.4
Avg. Reduction Required 30.96%
47
Appendix C: Estimates of Relative Loadings for Point and
Nonpoint Sources
Appendix Table C.1. Estimates of TSS and Fecal Coliform Runoff Loading Rates for Urban and Rural
Lands (USGS, 1999).
Land Use Type TSS Conc.
(tons/sq. mi)
FC Conc.
(cfu/L)
Mixed forrest/pasture/low density residential 2400 15
Mixed forrest/pasture/medium & low density residential 2100 20
Mixed forrest/pasture/medium & low density residential 564 24.5
Rural Average 1688 20
Industrial 122 27.5
Industrial 300 14.6
Medium-density residential 225 29
Medium-density residential 77 26.5
High-density residential 1000 15
Developing 4700 13
Urban Average 1071 21
Appendix Table C.2. Relative Fecal Coliform Concentration from Urban and Rural areas for Salem
Creek Watershed.
Land Use Land % Relative Fecal
Rate (#/100ml)
Normalized Fecal
Coliform Conc.
Rates (#/100ml)
Fecal Coliform
Conc. Ratio
Rural 21.02 20 4.20 20.23%
MS4 78.98 21 16.58 79.77%
Note: Fecal coliform data estimated in Appendix Table D.1 was utilized to estimate average fecal
coliform concentrations in stormwater runoff. The relative percent contributions of fecal coliform were
multiplied by the land use distribution and normalized to estimate the relative loading ratio for urban
(MS4) and rural (non-MS4) areas.
Appendix Table C.3. Relative TSS Loading from Urban and Rural Areas.
Watershed Land
Use Land %
Relative TSS
Rate
(tons sq mi/yr)
Normalized TSS
Loading Rates
(tons/sq mi/yr)
TSS Loading Ratio
Rural 79.30% 1688 1338.52 85.79% Grants
Creek MS4 20.70% 1071 221.74 14.21%
Note: TSS data estimated in Appendix Table C.3 was utilized to estimate average sediment loading in
stormwater runoff. The relative percent contributions of TSS were multiplied by the land use distribution
and normalized to estimate the relative loading percentage for urban (MS4) and rural (non-MS4) areas.
48
Appendix D. Public Notification of TMDLs for Fecal
Coliform for Salem Creek and Turbidity for Grants Creek
-------- Original Message --------
Subject: [wrri-news] Comment on Draft TMDL to DWQ by June 2nd
Date: Mon, 01 May 2006 12:48:17 -0400
From: Kelly Porter <kaporter@gw.fis.ncsu.edu>
Reply-To: Kelly Porter <kaporter@gw.fis.ncsu.edu>
To: <wrri-news@lists.ncsu.edu>
TMDLs for Fecal Coliform for Salem Creek and Turbidity for Grants Creek
Yadkin-Pee Dee River Basin
Now Available Upon Request
Total Maximum Daily Load for Fecal Coliform for Salem Creek and
Turbidity for Grants Creek in North Carolina 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
allocation for turbidity for Grants Creek and fecal coliform for Salem
Creek.
TO OBTAIN A FREE COPY OF THE TMDL REPORT:
Please contact Ms. Linda Chavis (919) 733-5083, extension 558 or write
to:
Ms. Linda Chavis
Water Quality Planning Section
1617 Mail Service Center
Raleigh, NC 27699
Interested parties are invited to comment on the draft TMDL study by
June 2, 2006. Comments concerning the report should be directed to Pam
Behm at the above address. The draft TMDL is also located on the
following website: http://h2o.enr.state.nc.us/tmdl
49
50
51
Appendix E. Responsiveness Summary for “Total Maximum
Daily Load for Fecal Coliform for Salem Creek and
Turbidity for Grants Creek in North Carolina”
DWQ received two written responses to the draft TMDL. Comments from specified
organizations are in italics as they appear in the delivered documents. DWQ’s response follows
in plain text.
The following comments were submitted to DWQ from D.R. Henderson, P.E., NC Department
of Transportation (NCDOT).
COMMENT: In response to DWQ’s public notice of the April 2006 draft turbidity TMDL for
Grants Creek, the NCDOT would like to offer the following comments for your consideration:
• We support DWQ’s decision not to identify the NCDOT as a significant contributor to
the impairment of Grants Creek from turbidity. In addition to the information
presented in the TMDL report, we believe DWQ’s decision is further supported by the
following facts:
- The NCDOT’s road right-of-way occupies the smallest percentage (~3%) of any
developed land cover category in the Grants Creek watershed. By way of comparison
the percentage of the watershed within the corporate boundaries of other NPDES
Phase II stormwater entities include Salisbury (~30%), Rowan County (100%), and
Kannapolis (~6%).
- The NCDOT has very few unpaved secondary roads in the watershed which might be
considered as a source of TSS. Over 98% of the state maintained roads in the
watershed are paved, thereby minimizing sediment loads from the road surface.
- Finally, and most significantly, the NCDOT did not receive any notices of violation
(NOVs) for failure to comply with applicable sediment and erosion control
regulations within the watershed during the TMDL analysis period (1997 – 2004).
This record of compliance also applies to the NCDOT’s sediment and erosion control
activities throughout Rowan County for the period.
RESPONSE: DWQ did not expressly evaluate the NC DOT as a potential contributor. DWQ is
currently working with the NCDOT to develop methodology to evaluate the role of NCDOT
managed roads in contributing pollutants to impaired waterbodies.
COMMENT: Per the guidance outlined in Section 11.4 TMDL Involvement of DWQ’s Fact
Sheet (dated November 2004) which accompanies the NCDOT’s current NPDES permit
(NCS000250), we respectfully request that the following statement be included in Section 5.2
Implementation Plan of the TMDL report:
52
“Based on the TMDL analysis presented in this report for Grants Creek, the
NCDOT was not identified as a significant contributor to the impairment.
Compliance with those NPDES permit (NCS000250) requirements applicable
within the TMDL area, excluding Part III – Section C, is expected to be sufficient
to meet the NCDOT’s WLA.”
RESPONSE: See response above. DWQ did not expressly evaluate the NC DOT as a
contributor to the impairment of Grants Creek. As such, DWQ cannot add the requested text to
the implementation plan of this TMDL document.
COMMENT: Please provide clarification as to the geographic extent of the segment of Grants
Creek impaired for turbidity. The description provided in Table 1.1 of the TMDL report, “From
SR 1910 to Yadkin River”, appears to be inconsistent with the stated length of the impaired
segment (1.2 miles). Using the NCDOT’s county road map for Rowan County we measured a
distance of approximately 4 miles from where SR 1910 crosses Grants Creek downstream to the
confluence with the Yadkin River. A similar distance measurement was obtained from the
Salisbury USGS 7.5 minute topographic map. Additionally, Figures 1.3 and 1.7 in the TMDL
report appear to be inconsistent with the information in Table 1.1, as these maps imply that the
entire length (~18 miles) of the Grants Creek mainstem is impaired for turbidity.
RESPONSE: The impairment length of Grants Creek is incorrectly listed on the 303(d) list as
1.2 miles. The correct impairment length of Grants Creek for turbidity is 4.2 miles. This will be
corrected in the next 303(d) report. Additionally, Figures 1.3 and 1.7 were corrected
accordingly.
The following comments were submitted to DWQ from A. McDaniel, NC Department of
Transportation.
COMMENT: In Table 1.3 the area units should be acres instead of square miles.
RESPONSE: This has been corrected in the final TMDL document.
COMMENT: On p. iv there is a short list of information items, one of which includes "DOT a
Significant Contribution (Yes or Blank)". We believe this listing is a convenient quick reference
and hope you all continue to include it in future TMDL reports. We would like to request
however, that you include separate references to the DOT for each TMDL. In other words you
might want to say "DOT a Significant Contribution in Grants Creek (Yes or Blank)" and on the
next line include "DOT a Significant Contribution in Salem Creek (Yes or Blank)".
RESPONSE: DWQ has added this distinction to the final TMDL document.
53
COMMENT: Additionally, we respectfully request that if the modeler's decision regarding
DOT as a significant contributor is something other than Yes (i.e. Blank), then the word "Blank"
be typed in. By typing in the word "Blank" then the reader has positive confirmation that a
decision was made as opposed to a situation where the modeler may have inadvertently omitted
information.
RESPONSE: DWQ follows EPA’s recommended format in which the space is left blank and
the word blank is not included. This format is geared towards expressly identifying when a
situation occurs, not when it does not occur or was not evaluated. For both Salem and Grants
Creek TMDLs, DWQ did not expressly evaluate the NCDOT as a potential contributor. DWQ is
currently working with the NCDOT to develop methodology to evaluate the role of NCDOT
managed roads in contributing pollutants to impaired waterbodies.