ElkCreekTMDL_final

Total Maximum Daily Load for Fecal
Coliform for Elk Creek in North Carolina

Final Report
February 2008

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
[phone]
Yadkin-Pee Dee River Basin
Photo by Bryan Colvard, Wilkes Soil and Water Conservation District
i

TMDL Summary Sheet

303(d) List Information

State: North Carolina
Counties: Wilkes
Basin: Yadkin- Pee Dee River Basin

Waterbody
Name
Description Assessment
Unit (AU):
Class Subbasin Impairment Miles
Elk Creek From Dugger
Creek to
Yadkin River
12-24-(10) B,
ORW
03-07-01 Fecal
Coliform
9.1

Constituents of Concern: Fecal Coliform Bacteria
Reason for Listing: Standard Violations

Applicable Water Quality Standard for Class B Waters:
• 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.

TMDL Development

Analysis/Modeling:
Load duration curves are based on cumulative frequency distribution of flow conditions in the
watershed. Allowable loads are average loads over the recurrence interval between the 95th and
10th percent flow exceeded (excludes extreme drought (>95th percentile) and floods (<10th
percentile). Percent reductions are 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.

ii
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.

TMDL Allocation Summary

Pollutants/Watershed
Existing
Exceeding
Load
WLA LA MOS TMDL
Fecal Coliform (colony forming units (cfu)/day)
Elk Creek 1.08E+12 0 5.58E+11 6.20E+10 6.20E+11

Notes:
WLA = Wasteload Allocation, LA = Load Allocation, MOS = Margin of Safety.
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. Overall reduction is based on the instantaneous standard of 400 cfu/100ml and is
assumed to be more stringent than the geometric mean standard.

Contributing Municipalities: NONE

Public Notice Date: 12/17/2007 – 1/31/2008
Submittal Date: 2/04/2008
Establishment Date: 2/20/2008
EPA Lead on TMDL (EPA or Blank):
DOT a Significant Contribution (Yes or Blank):
Endangered Species (Yes or Blank):
TMDL Considers Point Source, Nonpoint Source, or Both: both

iii
Table of Contents

1.0 Introduction............................................................................................................................... 1
1.1 TMDL Definition.................................................................................................................. 1
1.2 TMDL Components.............................................................................................................. 1
1.3 Water Quality Target: North Carolina Standards and Classifications.................................. 2
1.3.1 Water Quality Standard for Fecal Coliform................................................................... 2
1.3.2 Outstanding Resource Water Classification .................................................................. 3
1.4 Watershed Description.......................................................................................................... 3
1.5 Water Quality Monitoring..................................................................................................... 6
1.5.1 Fecal Coliform Monitoring in Elk Creek....................................................................... 6
2.0 Source Assessment.................................................................................................................... 8
2.1 General Sources of Fecal Coliform....................................................................................... 8
2.1.1 Nonpoint Sources of Fecal Coliform............................................................................. 8
3.0 Elk Creek Impairment............................................................................................................. 10
3.1 Source Assessment.............................................................................................................. 10
3.1.1 NPDES Wastewater Permits........................................................................................ 10
3.1.2 NPDES Stormwater Permits........................................................................................ 10
3.1.3 Livestock Populations.................................................................................................. 10
3.1.4 Septic Tanks................................................................................................................. 11
3.2 Technical Approach............................................................................................................ 11
3.2.1 Endpoint for Fecal Coliform........................................................................................ 12
3.2.2 Flow Duration Curve ................................................................................................... 12
3.2.3 Load Duration Curve ................................................................................................... 13
3.3 Total Maximum Daily Load (TMDL) ................................................................................ 14
3.3.1 Margin of Safety (MOS).............................................................................................. 15
3.3.2 Target Reduction.......................................................................................................... 15
3.3.3 TMDL Allocation ........................................................................................................ 16
3.3.4 Critical Condition and Seasonal Variation .................................................................. 18
4.0 Summary and Future Consideration ....................................................................................... 19
4.1 Stream Monitoring.............................................................................................................. 19
4.2 Implementation Plan........................................................................................................... 19
5.0 Public Participation................................................................................................................. 20
6.0 References............................................................................................................................... 21
APPENDIX A: Elk Creek Data.................................................................................................... 22
APPENDIX B. Wilkes Soil & Water Conservation District Questionnaire................................ 26
APPENDIX C. Public Notification of TMDL for Fecal Coliform for Elk Creek....................... 28

1
1.0 Introduction

1.1 TMDL Definition
This report presents the development of a Fecal Coliform Total Maximum Daily Load (TMDL)
for Elk Creek in the Yadkin-Pee Dee River Basin (Figure 1.1) in North Carolina. As identified
by the North Carolina Division of Water Quality (DWQ), the impaired segment of the waterbody
is described in Table 1.1.

Figure 1.1. Location of Yadkin River Basin within North Carolina.

Table 1.1. Description of Impaired Segments for Elk Creek.
Waterbody
Name Description Assessment
Unit (AU): Class Subbasin Impairment Miles
Elk Creek From Dugger
Creek to
Yadkin River
12-24-(10) B1,
ORW
03-07-01 Fecal
Coliform
9.1
1 Class B waters are freshwaters protected for primary recreation, which includes swimming on a frequent or
organized basis and all Class C uses. Class C waters are protected for secondary recreation, fishing, aquatic life
including propagation and survival, and wildlife.

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.

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, 2000) and the Federal Advisory
Committee (FACA) (USEPA, 1998) are as follows:

2
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).

Critical Conditions. Critical conditions indicate the combination of environmental factors that
result in just meeting the water quality criterion and have an acceptably low frequency of
occurrence.

Section 303(d) of the CWA 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.

1.3 Water Quality Target: North Carolina Standards and Classifications
1.3.1 Water Quality Standard for Fecal Coliform
The North Carolina fresh water quality standard for Class B waters for fecal Coliform (15A
NCAC 02B. 0219) states:

The following water quality standards apply to surface waters that are for primary
recreation, including frequent or organized swimming and are classified as Class B
3
waters. Water quality standards applicable to Class C waters as described in Rule .0211
of this Section also apply to Class B waters.
Organisms of coliform group: fecal coliforms not to exceed geometric mean of
200/100 ml (MF count) based on at least five consecutive samples examined
during any 30-day period and not to exceed 400/100 ml in more than 20 percent
of the samples examined during such period.

The North Carolina fresh water quality standard for Class C waters for fecal Coliform (15a
NCAC 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 shall be used as the reference method.

1.3.2 Outstanding Resource Water Classification
Elk Creek is designated as an Outstanding Resource Water (ORW). Special protection measures
that apply to North Carolina ORWs are set forth in 15A NCAC 2B.0225. At a minimum, no new
discharges or expansions are permitted, and a 30-foot vegetated buffer or stormwater controls for
new developments are required. In some circumstances, the unique characteristics of the waters
and resources that are to be protected require that a specialized (or customized) ORW
management strategy be developed.

1.4 Watershed Description
The watershed area was delineated by using the USGS 14-digit hydrologic units. Elk Creek is
located in the Yadkin-Pee Dee River Basin. The Elk Creek watershed is located within Watauga
and Wilkes Counties, as shown in Figure 1.2. The watershed is located within hydrologic unit
03040101010050.
4

Figure 1.2. Elk 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 2006 are 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.
County Persons per
square mile,
20001
2000
Population
2006
Population
Estimate
Population,
percent change,
April 1, 2000 to
July 1, 20062
Wilkes 86.7 65,632 67,310 2.6%
Watauga 136.4 42,695 42,700 0.0%
1. North Carolina average persons per square mile = 165.2
2. North Carolina average population percent change 4/1/00 – 7/1/06 = 10.1%
Wilkes - http://quickfacts.census.gov/qfd/states/37/37193.html
Watauga - http://quickfacts.census.gov/qfd/states/37/37189.html

Land Use/Land Cover
The land use/land cover characteristics of the watershed were determined using the 2001
National Land Cover Database (http://www.mrlc.gov/mrlc2k_nlcd.asp). Table 1.3 shows the
area in acres for each of these categories. Land use and land cover information is also provided
graphically in Figure 1.3.

5
Table 1.3. Land Use Acreages and their Percent Compositions in the Elk Creek Watershed.
Land Use Area
(acres)
Area
(percent)
Deciduous Forest 27,606.83 85.24%
Pasture/Hay 1,526.71 4.71%
Evergreen Forest 1,115.06 3.44%
Developed, Open Space 884.22 2.73%
Mixed Forest 751.90 2.32%
Shrub/Scrub 336.70 1.04%
Grassland/Herbaceous 88.51 0.27%
Woody Wetlands 30.69 0.09%
Cultivated Crops 21.79 0.07%
Developed, Low/Medium Intensity 11.12 0.03%
Barren Land (Rock/Sand/Clay) 9.79 0.03%
Open Water 2.89 0.01%
Total 32,386 100%

6

Figure 1.3. Land Use and Land Cover distribution in the Elk Creek Watershed.

1.5 Water Quality Monitoring
1.5.1 Fecal Coliform Monitoring in Elk Creek
The DWQ has one monitoring station on Elk Creek: Q0220000 at Elk Creek at NC268 in
Elkville. The location of this station is shown in Figure 1.4. There are numerous qualifiers on
the sampling data, which can be found in Appendix Table A.1. The most common qualifier (Q)
refers to the exceedance of holding times of the water quality samples that were collected.
Holding time refers to holding samples on ice from the time of collection until the samples can
be analyzed in the laboratory. Holding samples on ice slows the metabolism of the organisms
7
resulting in no appreciable growth. DWQ used all the data collected, including those data that
exceeded holding times, in the development of the TMDL. The actual concentration is expected
to be at least as high as the value reported.

In addition to the normal monthly samples, ten additional samples were taken at this station in
June (5 samples) and July (5 samples) of 2002 to determine if fecal coliform concentrations
exceeded the geometric mean portion of the standard (fecal coliforms not to exceed geometric
mean of 200cfu/100 ml based on at least five consecutive samples examined during any 30-day
period). These sampling points are highlighted in Appendix Table A.1. A more detailed
accounting of sampling can be found in Table 1.4.

Table 1.4. Elk Creek Sampling
Station Sampling
Period
Number of
Samples
Collected
Approximate
Sampling
Frequency
Number of Samples
Exceeding Standard
(400 colony forming
units (cfu)/100 ml)
June 2002
Geomean1
July 2002
Geomean1
Q0220000 Jan. 1997 –
Sept. 2006 121 monthly 17 (14%) 408 cfu/100
ml
455 cfu/100
ml
1. Geomean is calculated when there are five consecutive samples examined during any 30-day period.

Figure 1.4. Water Quality Monitoring Station in the Elk Creek Watershed.
8

2.0 Source Assessment

A source assessment is used to identify and characterize the known and suspected sources of
fecal coliforms in the watershed. This section outlines general sources of fecal coliform.
Sources specific to the Elk Creek watershed are discussed in Section 3.1.

2.1 General Sources of Fecal Coliform
Both point sources and nonpoint sources may contribute fecal coliform to water bodies.
However, in Elk Creek, there are no point sources. Potential nonpoint sources of fecal coliform
loading are discussed below.

2.1.1 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). Nonpoint sources of fecal
coliform 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.

9
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).
10
3.0 Elk Creek Impairment

3.1 Source Assessment
3.1.1 NPDES Wastewater Permits
There are no facilities that discharge wastewater to the polluted portion of Elk Creek and its
tributaries.

3.1.2 NPDES Stormwater Permits
The only stormwater permit in the Elk Creek watershed is held by the North Carolina
Department of Transportation (NC DOT), whose NPDES Phase I permit applies statewide. At
the time of development of this TMDL, it does not appear that NC DOT is a significant
contributor of fecal coliform in this watershed. NC DOT is allowed to continue to discharge in
accordance with its approved NPDES stormwater permit (NCS000250). NC DOT will continue
to implement measures required by the permit, including illicit discharge detection and
elimination, post-construction controls, management of hydraulic encroachments, sediment and
erosion control, stormwater pollution prevention for industrial facilities, research, and education
programs. The finding that NCDOT is not a significant contributor of fecal coliform loads may
be subject to change over time if watershed conditions significantly change.

3.1.3 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 3.1 for the counties that contain the Elk Creek watershed.

DWQ requested information specific to the Elk Creek watershed from both Watauga and Wilkes
Soil & Water Conservation Districts. DWQ received a completed questionnaire from the Wilkes
Soil & Water Conservation District. The questionnaire is provided in Appendix B.

As shown in Table 3.1, a very small percentage of cattle and beef cows in Wilkes County are
actually in the Elk Creek watershed. However, even though the percentage is small, 75% of the
cattle in the Elk Creek watershed have direct access to Elk Creek (Appendix B).

The Wilkes Soil & Water Conservation District also estimates that 80% of horses in the
watershed have direct access to streams in the watershed. In addition, manure from various
livestock is applied to agricultural lands in the watershed.

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Table 3.1. Estimated Livestock population in Watauga and Wilkes Counties.
Livestock Date data is
valid from Watauga1 Wilkes1
Estimated livestock in Wilkes
County portion of Elk Creek
Watershed2
Cattle All Jan 1, 2007 10,200 32,000 480 (1.5%)
Beef Cows Jan 1, 2007 3,600 15,100 151 (1%)
Milk Cows Jan 1, 2007 No data 1,300 0%
Broilers Produced 2006 No data 91,700,000 0%
Chickens, excluding
broilers Dec. 1, 2006 No data 1,050,000 0%
1. Source: Wilkes: http://www.ncagr.com/stats/codata/wilkes.htm
Watauga: http://www.ncagr.com/stats/codata/watauga.htm
2. Estimated by Wilkes Soil & Water Conservation District (see Appendix B).

3.1.4 Septic Tanks
Septic tanks and cesspools can contribute to the nonpoint sources of fecal coliform found in Elk
Creek. The Wilkes Soil & Water Conservation District estimates the septic system failure rate to
be 25% in Wilkes County (see Appendix B). More information is provided in Table 3.2.

Table 3.2. Estimated housing units using septic systems in 1990 in Wilkes and Watauga
Counties.
County Number of Housing
Units (1990)
Number of Septic
Tank or Cesspool
Systems
Percentage of
Housing Units with
Septic Tank or
Cesspool Systems
Wilkes 24,960 20,467 82%
Watauga 19,538 11,582 59%
Source for Septic Tank and Cesspool System data:
http://factfinder.census.gov/servlet/QTTable?_bm=y&-context=qt&-qr_name=DEC_1990_STF3_DP5&-
ds_name=DEC_1990_STF3_&-CONTEXT=qt&-tree_id=101&-all_geo_types=N&-redoLog=true&-
_caller=geoselect&-geo_id=05000US37189&-geo_id=05000US37193&-search_results=01000US&-
format=&-_lang=enSource for Housing Unit data:

3.2 Technical Approach
Based on the above information, nonpoint sources contribute fecal coliform to Elk Creek.
Because of the size of Elk 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).

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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 Elk Creek often enough to evaluate the geometric mean standard using
the load duration curve approach, therefore only the instantaneous standard is used as the
endpoint for the fecal coliform TMDL in the creek. An analysis of the effectiveness of the
reduction on meeting the geometric mean standard is provided below in Section 3.3.3.

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. There is
daily flow data available for Elk Creek from USGS Gaging Station #02111180 (see Appendix A,
Figure A.1), Elk Creek at Elkville, which is in the same location that ambient monitoring data is
collected. Flow statistics as generated by the curves from the estimated flow data are presented
in Table 3.3.

Table 3.3. Flow Statistics for estimated Elk Creek at ambient station Q0220000
High Flow
(<10th Percentile)
Transitional Flow
(Between 10th and 30th
Percentile)
Typical Flow
(Between 30th and 90th
Percentile)
Low Flow
(>90th Percentile)
150 – 2950 cfs 88 – 150 cfs 21 – 88 cfs 7 – 21 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 Elk Creek are discussed in the following paragraphs.

13

Flow Duration Curve for Elk Creek at DWQ Station Q0220000
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 Transitional Typical Flow Low
Flow Flow Flow
Figure 3.2. Flow Duration Curve for Elk Creek at Station Q0220000.

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
assumes a fecal coliform concentration of 360 cfu/100ml and 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.

The following paragraphs discuss procedures to estimate endpoints for fecal coliform in Elk
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 cfu/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 Elk 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.
14

Load Duration Curve for Elk Creek @ Sta. Q0220000
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 Load

Figure 3.3. Fecal coliform load duration curve for Elk Creek at station Q0220000, from January
1997 through September 2006.

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 fecal coliform bacteria in the Elk 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 allocations (WLAs), nonpoint source allocations
(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 those loads 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
15
load duration curve approach was utilized to estimate the TMDL for fecal coliform. The
systematic procedures adopted to estimate TMDLs are described below.

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 target can be
seen in Table 3.4.

Table 3.4. Water Quality Standard and Explicit Margin of Safety.
Standard for Fecal
Coliform 400 cfu/100 ml
Target with 10% MOS 360 cfu/100 ml

3.3.2 Target Reduction
The load reduction needed to meet 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.

A power curve equation for the data points violating the water quality criterion was estimated.
The equation is presented in Equation 3.2.

Y = 4.13E11 * X-0.939 R2 = 0.47 (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 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
16
values are given in Appendix Table A.2. The derivation of TMDL components is provided in
Appendix Table A.3.

Load Duration Curve for Elk Creek @ Sta. Q0220000
y = 4.13E+11x-9.39E-01
R2 = 4.66E-01
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 Load Exceedances Power (Exceedances)

Figure 3.4. Load Duration Curve with Allowable and Estimated Exceeding Loads of Fecal
Coliform in Elk Creek at station Q0220000.

3.3.3 TMDL Allocation
As identified by the above load duration curve method, a significant reduction of fecal coliform
is required in Elk Creek. A summary of reductions required is provided in Table 3.5 (also, see
Appendix Table A.2).

Table 3.5. Reduction required for Fecal Coliform.
Pollutant Target with
MOS
Estimated
Exceeding Load
Allowable Load
(TMDL-MOS)
Average Reduction
Required
Fecal
Coliform
(cfu/day)
<360
cfu/100ml 1.08E+12 5.58E+11 48.4%

As mentioned above in Section 3.2.1, 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. This analysis used the instantaneous standard as the endpoint for the
fecal coliform TMDL in the creek. To verify that the required reduction will also meet the
17
geometric mean standard, the reduction was applied to those fecal coliform concentrations
measured during the sampling to calculate the geometric mean (shown in Appendix Table A.1)
and a new geometric mean was calculated. The results of this analysis are shown in Table 3.6
and indicate that the required reduction will meet the geometric mean portion of the fecal
coliform standard.

Table 3.6. Verification of geometric mean portion of fecal coliform standard.
Sampling Period Measured
Geometric Mean
Geometric Mean with
Reduction
June 2002 408 147
July 2002 455 154

3.3.3.1. Waste Load Allocation (WLA)
The waste load allocation for fecal coliform is 0 cfu/day.

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. In Elk Creek watershed, there are only nonpoint sources
contributing fecal coliform to the creek. The estimated contributions of fecal coliform from the
nonpoint sources are presented in Table 3.7. The estimated percent reduction from nonpoint
sources is 48%, as shown in Table 3.8.

Table 3.7. Estimated TMDL and Load Allocation for Fecal Coliform for the Elk Creek
Watershed.
Pollutant Existing
Load
WLA LA MOS TMDL1
Fecal Coliform
(cfu/day) 1.08E+12 0 5.58E+11 6.20E+10 6.20E+11
1. TMDL = WLA + LA + MOS

Table 3.8. Estimated Percent Reduction by Source for Fecal Coliform (shown in cfu/day) for the
Elk Creek Watershed.
WLA LA
Existing Load (cfu/day) 0 1.08E+12
Load Allocation (cfu/day) 0 5.58E+11
Percent Reduction 0% 48.4%

18

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.
19
4.0 Summary and Future Consideration

This report presents the development of the Fecal Coliform Total Maximum Daily Load
(TMDL) for Elk Creek in the Yadkin Pee-Dee River Basin.

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 48 percent reduction in nonpoint source contributions of fecal coliform is required
in order to meet the water quality standard in Elk Creek. Nonpoint sources are
responsible for the exceedance of fecal coliform standards.

4.1 Stream Monitoring
Stream monitoring should continue on a monthly interval at the existing ambient monitoring
stations. The continued monitoring of 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, the schedule for stream monitoring should be reviewed and revised to
eliminate or reduce holding time violations and include evaluation of the geometric mean portion
of the standard (i.e. periodically collect five samples in 30 days to calculate geometric mean).

4.2 Implementation Plan
Reductions for fecal coliform should be sought through controlling animal access to streams,
identification and repair of failing septic systems, and targeting storm-driven sources.

The TMDL analysis was performed using the best data available to specify the fecal coliform
reduction 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. Local stakeholder groups, governments, and agencies are
encouraged to develop a more specific implementation plan.

20

5.0 Public Participation

A draft of the TMDL was publicly noticed through various means. The TMDL was public
noticed in the relevant counties through a local newspaper (Wilkes Journal-Patriot on December
19, 2007, see Appendix C). The TMDL was also public noticed on December 18, 2007 through
the North Carolina Water Resources Research Institute email list-serve (see Appendix C).

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 January 31, 2008.

DWQ received no public comments on the Elk Creek TMDL.

21
6.0 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.

North Carolina Department of Agriculture (NCDA):
Wilkes: http://www.ncagr.com/stats/codata/wilkes.htm
Watauga: http://www.ncagr.com/stats/codata/watauga.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) 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:
Wilkes - http://quickfacts.census.gov/qfd/states/37/37193.html
Watauga - http://quickfacts.census.gov/qfd/states/37/37189.html

U.S. Census Bureau:
http://factfinder.census.gov/servlet/QTTable?_bm=y&-context=qt&-
qr_name=DEC_1990_STF3_DP5&-ds_name=DEC_1990_STF3_&-CONTEXT=qt&-
tree_id=101&-all_geo_types=N&-redoLog=true&-_caller=geoselect&-
geo_id=05000US37189&-geo_id=05000US37193&-search_results=01000US&-
format=&-_lang=enSource for Housing Unit data:

22
APPENDIX A: Elk Creek Data

Table A.1. Water Quality Data for Elk Creek at Station Q0220000 (highlighted rows indicate
data was collected for 5/30 testing).

Date
Instream Fecal
Coliform
Concentration
(cfu/100mL)
Remark1

Date
Instream Fecal
Coliform
Concentration
(cfu/100mL)
Remark1

01/16/97 10 K 04/11/02 41 Q1
02/18/97 10 K 05/14/02 1300 Q1
03/11/97 10 K 6/4/2002 300
04/08/97 10 K 6/11/2002 200
05/08/97 10 K 6/13/2002 250
06/10/97 140 6/18/2002 500
07/09/97 130 6/20/2002 1500
Geometric
Mean = 408
08/11/97 100 07/09/02 240 B4,Q1
09/10/97 220 7/9/2002 320
10/09/97 18 7/17/2002 346
11/13/97 45 7/18/2002 400
12/15/97 10 K 7/24/2002 1050
01/12/98 10 K 7/25/2002 420
Geometric
Mean = 455
02/12/98 10 K 08/01/02 210 Q1,B4
03/19/98 91 09/09/02 140 Q1
04/30/98 23 10/01/02 180 Q1
05/18/98 90 11/14/02 17 B5,Q1
06/11/98 190 12/09/02 12 Q1
07/15/98 140 01/15/03 5 Q1
08/10/98 280 02/04/03 670 Q1
09/15/98 140 03/12/03 7 Q1
10/21/98 45 04/24/03 48 Q1
11/18/98 76 05/19/03 150 Q1
12/10/98 160 06/04/03 930 Q1
01/11/99 10 K 07/09/03 120 Q1
02/08/99 27 08/12/03 190 Q1
03/23/99 10 K 09/25/03 100 Q1
04/27/99 150 10/30/03 50 Q1
06/10/99 120 11/12/03 52 Q1
07/08/99 100 12/01/03 18 Q1
08/05/99 20 J 01/14/04 4 Q1
09/07/99 60 J 03/15/04 18 Q1
10/14/99 150 J 04/19/04 14 Q1
11/04/99 100 J 05/13/04 440 B4,Q1
12/14/99 630 L 06/22/04 1500 Q1
02/07/00 27 07/26/04 200 Q1
03/23/00 45 08/26/04 310 B4,Q1
23
Date
Instream Fecal
Coliform
Concentration
(cfu/100mL)
Remark1

Date
Instream Fecal
Coliform
Concentration
(cfu/100mL)
Remark1

04/12/00 100 09/27/04 160 Q1
05/09/00 230 10/28/04 410 Q1,B4
06/12/00 210 11/03/04 220 B4,Q1
07/19/00 150 12/14/04 6 Q1
08/15/00 340 A 02/01/05 17 Q1
09/12/00 240 03/03/05 57 Q1
10/10/00 450 A 03/31/05 22 Q1
11/08/00 800 04/20/05 95 Q1
12/27/00 82 06/01/05 300 B4,Q1
01/09/01 190 06/29/05 180 Q1
02/08/01 130 07/14/05 280 B4,Q1
04/23/01 400 08/02/05 120 Q1
05/07/01 130 B1,J2,Q 08/31/05 1200 Q1
06/12/01 200 B1,Q 11/01/05 67 Q1
07/12/01 140 B1,Q 11/30/05 200 Q1
08/14/01 2000 Q 02/01/06 1 Q1
09/06/01 310 Q 03/22/06 5 Q1
10/09/01 120 B4,Q 05/02/06 47 Q1
11/07/01 39 Q 6/1/2006 190 Q1
12/11/01 560 Q 6/27/2006 1900 Q1
01/10/02 8 Q1 7/13/2006 190 Q1
02/20/02 40 Q1 8/10/2006 90 Q1
03/07/02 1 B2,Q1 9/12/2006 180 Q1

1. Fecal Coliform Remark Codes:
A Value reported is the mean (average) of two or more determinations. This code is to be used if the results of
two or more discrete and separate samples are averaged. These samples shall have been processed and
analyzed independently (e.g. field duplicates, different dilutions of the same sample).
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.
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.
B5 Too many colonies were present; too numerous to count (TNTC), the numeric value represents the
maximum number of counts typically accepted on a filter membrane (60 for fecal and 80 for total),
multiplied by 100 and then divided by the smallest filtration volume analyzed. This number is reported as a
greater than value.
J Estimated value; value may not be accurate.
J2 Estimated value; value may not be accurate. The reported value failed to meet the established quality
control criteria for either precision or accuracy.
K Actual value is known to be less than value given
L Actual value is known to be greater than value given
Q Holding time exceeded.
Q1 Holding time exceeded. Holding time exceeded prior to receipt by lab.
24
USGS Gage 02111180 Daily Mean Flow (cfs)
0
500
1000
1500
2000
2500
3000
01
/
9
7
07
/
9
7
01
/
9
8
07
/
9
8
01
/
9
9
07
/
9
9
01
/
0
0
07
/
0
0
01
/
0
1
07
/
0
1
01
/
0
2
07
/
0
2
01
/
0
3
07
/
0
3
01
/
0
4
07
/
0
4
01
/
0
5
07
/
0
5
01
/
0
6
07
/
0
6
Date
Me
a
n

F
l
o
w

(
c
f
s
)
Figure A.1. Daily average flow (cfs) measured at USGS Gage 02111180.

Table A.2. Estimation of Load Reduction Required in Fecal Coliform for Elk Creek at Station
Q0220000.
% Flow
Exceeded
Flow
(cfs)
Estimated
Exceedance Load
(cfu/day)
TMDL not
including MOS
(cfu/day)
10% 150.0 3.59E+12 1.32E+12
15% 124.0 2.45E+12 1.09E+12
20% 109.0 1.87E+12 9.60E+11
25% 97.0 1.52E+12 8.54E+11
30% 88.0 1.28E+12 7.75E+11
35% 80.0 1.11E+12 7.05E+11
40% 71.0 9.76E+11 6.25E+11
45% 65.0 8.74E+11 5.72E+11
50% 60.0 7.92E+11 5.28E+11
55% 53.0 7.24E+11 4.67E+11
60% 46.0 6.67E+11 4.05E+11
65% 41.0 6.19E+11 3.61E+11
70% 36.0 5.77E+11 3.17E+11
75% 31.0 5.41E+11 2.73E+11
80% 27.0 5.09E+11 2.38E+11
85% 24.0 4.81E+11 2.11E+11
90% 21.0 4.56E+11 1.85E+11
95% 16.9 4.33E+11 1.49E+11
Average 1.08E+12 5.58E+11
Avg. Reduction Required 48.4%
25
Table A.3. Derivation of TMDL Components

% Flow
Exceeded MOS WLA LA
TMDL
(including
MOS)
10.0% 1.47E+11 0 1.32E+12 1.47E+12
15.0% 1.21E+11 0 1.09E+12 1.21E+12
20.0% 1.07E+11 0 9.60E+11 1.07E+12
25.0% 9.49E+10 0 8.54E+11 9.49E+11
30.0% 8.61E+10 0 7.75E+11 8.61E+11
35.0% 7.83E+10 0 7.05E+11 7.83E+11
40.0% 6.95E+10 0 6.25E+11 6.95E+11
45.0% 6.36E+10 0 5.72E+11 6.36E+11
50.0% 5.87E+10 0 5.28E+11 5.87E+11
55.0% 5.19E+10 0 4.67E+11 5.19E+11
60.0% 4.50E+10 0 4.05E+11 4.50E+11
65.0% 4.01E+10 0 3.61E+11 4.01E+11
70.0% 3.52E+10 0 3.17E+11 3.52E+11
75.0% 3.03E+10 0 2.73E+11 3.03E+11
80.0% 2.64E+10 0 2.38E+11 2.64E+11
85.0% 2.35E+10 0 2.11E+11 2.35E+11
90.0% 2.06E+10 0 1.85E+11 2.06E+11
95.0% 1.66E+10 0 1.49E+11 1.66E+11
Average 6.20E+10 0 5.58E+11 6.20E+11

26
APPENDIX B. Wilkes Soil & Water Conservation District
Questionnaire

TMDL QUESTIONAIRE –Wilkes County (Elk Creek Watershed)

Estimated Livestock Population
The North Carolina Department of Agriculture (NCDA) regularly performs an agricultural
census for each county of the state. Can you estimate what percentage of the county population
is found within the Elk Creek watershed? Please enter any available estimates in the table
below.

Livestock Date data is
valid from
Wilkes % in Elk
Creek
watershed
Cattle All Jan 1, 2007 32,000 1.5%
Beef Cows Jan 1, 2007 15,100 1%
Milk Cows Jan 1, 2007 1,300 0%
Broilers Produced 2006 91,700,000 0%
Chickens, excluding broilers Dec. 1, 2006 1,050,000 0%
Source: Wilkes: http://www.ncagr.com/stats/codata/wilkes.htm

Stream Access
1. Do beef cattle have access to streams? Yes or No (circle correct answer)
a. Could you approximate the percentage beef cattle having stream access within the
watershed? __75%________

2. Do horses have access to streams? Yes or No (circle correct answer)
a. Could you approximate the percentage horses having stream access within the
watershed? ___80%_______

3. Are hogs confined or do they have limited stream access? _____N/A__________

4. Percent of beef cows with access to forested areas __30%_____

5. Do you have any estimate on the deer population? ___35______ per square mile

Manure Application
6. Is manure from beef cattle, dairy cattle, swine, poultry, sheep, or horses collected and
applied to agricultural lands? Yes or No (circle correct answer)

Manure occurs in the field. Chicken litter from other areas of Wilkes Co. is most likely applied
to the majority of the fields, at unknown application rates.
27

7. If answer to #6 is yes, can you approximate the percentage of livestock manure that is
collected and applied to agricultural land? Example: 30 percent swine, 100 percent dairy
cattle, and 100 percent poultry are collected and applied.

Animal Type Percent Collected and
applied
Beef Cattle
Dairy Cattle
Swine
Poultry
Sheep
Horses

8. Is manure imported into the county? Yes or No (circle correct answer)

9. Are there any confined poultry operations? Yes or No (circle correct answer)
a. How do they manage their poultry litter?

b. Where (and how, and when) do they land apply?

Land application of chicken litter probably occurs. It most likely originates from
other areas of Wilkes.

c. If so, is data available to calculate the loading rates? Yes or No (circle correct answer)
What are the rates if known? __________________

10. Dairy cattle are assumed to be confined 40 percent of the time and grazing 60 percent.
Dairy cattle are assumed not to have access to streams. Is this a correct assumption?
Yes or No (circle correct answer)
N/A
a. How is the liquid residual from cleaning barns after milking disposed of?

b. It could be assumed that the majority of the operation’s parlor waste is collected
with the waste system. If this is a significant amount available for runoff, please
indicate.

Septic System Contribution

11. What do you estimate the septic system failure rate in your county to be? __25%_____
EPA assumes 20 percent.
28
APPENDIX C. Public Notification of TMDL for Fecal
Coliform for Elk Creek

Subject: [wrri-news] PUBLIC NOTICE: Elk Creek TMDL for Fecal Coliform
From: "Kelly Porter" <[e-mail]>
Date: Tue, 18 Dec 2007 12:42:32 -0500
To: <[e-mail]>

PUBLIC NOTICE: Elk Creek TMDL for Fecal Coliform

Now Available Upon Request –
Total Maximum Daily Load (TMDL) for Fecal Coliform for Elk Creek (Yadkin-Pee
Dee River Basin) 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 the pollutants, determines allowable loads to
surface waters, and suggests fecal coliform allocations for Elk Creek.

TO OBTAIN A FREE COPY OF THE TMDL REPORT:
Please contact Ms. Linda Chavis [phone], 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 January
31, 2008. 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.

29