ChicodCreekTMDLFinalReport_000

Total Maximum Daily Load for
Fecal Coliform Bacteria in
Chicod Creek,
North Carolina
[Waterbody ID 28-101]

Final Report
August 2004

Prepared by:
NC Department of Environment and Natural Resources
Division of Water Quality
1617 Mail Service Center
Raleigh, NC 27699-1617

With support from:
Tetra Tech, Inc.
Cape Fear Bldg., Suite 105
3200 Chapel Hill-Nelson Highway
PO Box 14409
Research Triangle Park, NC 27709

Tar-Pamlico River Basin

Chicod Creek Coliform TMDL April 2004

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Table of Contents
List of Tables ..................................................................................................................iii
List of Figures ..................................................................................................................iv
1 Introduction..................................................................................................................1
1.1 Problem Definition........................................................................................................................ 1
1.1.1 TMDL Components.............................................................................................................. 1
1.1.2 Chicod Creek Fecal Coliform Impairment ........................................................................... 2
1.2 Watershed Description .................................................................................................................. 2
1.2.1 Landuse/Land Cover.............................................................................................................3
1.2.2 Population and Onsite Wastewater Disposal........................................................................ 5
1.2.3 Agriculture............................................................................................................................ 7
1.2.4 Swine Operations.................................................................................................................. 7
1.2.5 Other Livestock Operations................................................................................................ 13
1.3 Flow Gaging................................................................................................................................ 13
1.4 Water Quality Monitoring........................................................................................................... 14
1.4.1 Monitoring Sites ................................................................................................................. 14
1.4.2 Primary Chicod Creek Monitoring Site.............................................................................. 15
1.4.3 Control Sites in the Creeping Swamp Watershed............................................................... 17
1.4.4 Reference Sites in Van Swamp and Durham Creek Watersheds........................................ 18
1.4.5 Chicod Creek Upstream Site at Boyd’s Crossroads............................................................ 19
1.4.6 Comparison of Fecal Coliform Statistics at Monitoring Stations....................................... 21
2 Source Assessment.....................................................................................................23
2.1 Point Source Fecal Coliform Contributions ................................................................................ 23
2.2 Nonpoint Source Fecal Coliform Contributions.......................................................................... 23
2.2.1 Interpretation of Monitoring Data for Nonpoint Sources ................................................... 23
2.2.2 Agriculture.......................................................................................................................... 25
2.2.3 Animal Operations..............................................................................................................25
2.2.4 Onsite Wastewater Disposal............................................................................................... 25
2.2.5 Impacts of Silviculture........................................................................................................26
2.3 Analysis of Existing Management Measures .............................................................................. 27
2.4 Conceptual Model of Fecal Coliform in Chicod Creek............................................................... 27
3 Technical Approach to TMDL...................................................................................29
3.1 TMDL Endpoints ........................................................................................................................ 29
3.2 Load-Duration Curves for Fecal Coliform.................................................................................. 29
3.3 Determination of Existing Fecal Coliform Load and Assimilative Capacity.............................. 33
3.3.1 Instantaneous (20 Percent) Criterion .................................................................................. 34
3.3.2 Geometric Mean Criterion.................................................................................................. 36
4 TMDL Development..................................................................................................39
4.1 TMDL Definition ........................................................................................................................ 39
4.2 TMDL Endpoints ........................................................................................................................ 39
4.3 Critical Conditions ...................................................................................................................... 39
4.4 Seasonal Variation....................................................................................................................... 40
4.5 Margin of Safety.......................................................................................................................... 40
4.6 Wasteload Allocations................................................................................................................. 40
4.7 Load Allocations ......................................................................................................................... 41
4.8 TMDL Summary......................................................................................................................... 42
Chicod Creek Coliform TMDL April 2004

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5 Report Summary ........................................................................................................43
6 TMDL Implementation Plan......................................................................................45
7 Stream Monitoring.....................................................................................................47
8 Future Efforts .............................................................................................................49
9 Public Participation....................................................................................................51
10 Further Information....................................................................................................53
11 References .................................................................................................................55
12 Appendices .................................................................................................................57
Appendix A. Fecal Coliform Data for Chicod Creek..................................................A-1
Appendix B. Assimilative Capacity and Load Reduction Calculations .....................B-1
Appendix C. Public Notification of Public Review Draft of Chicod Creek TMDL...C-1

Chicod Creek Coliform TMDL April 2004

iii
List of Tables
Table 1. Landuse Tabulation for the Chicod Creek Watershed .............................................................. 5
Table 2. Swine Operations Located in the Chicod Creek Watershed ..................................................... 8
Table 3. Daily Average Stream Flow Statistics for USGS Station 02084160 Chicod Creek
at SR1760 Near Simpson, NC, Oct. 1975 – Dec. 2003........................................................... 13
Table 4. Fecal Coliform Monitoring Stations for the Chicod Creek Analysis...................................... 15
Table 5. Comparison of Excursions of Fecal Coliform Criteria in the Chicod Creek Watershed
and the Reference and Control Sites (period of record).......................................................... 22
Table 6. Number of Excursions of the Instantaneous Fecal Coliform Criterion of 400
per 100 mL. Classified by Flow Regime................................................................................. 24
Table 7. Fecal Coliform Target Load and Reduction Requirements Calculated using the Load-
Duration Curve Approach....................................................................................................... 36
Table 8. Fecal Coliform Bacteria Load Allocations for Chicod Creek................................................. 42
Table 9. TMDL Summary for Fecal Coliform in Chicod Creek........................................................... 42

Chicod Creek Coliform TMDL April 2004

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List of Figures
Figure 1. Location of Chicod Creek Watershed in the Tar/Pamlico Basin, NC.................................... 3
Figure 2. NLCD Landuse Data for the Chicod Creek Watershed (1992) ............................................. 4
Figure 3. Septic System Densities by Census Block (2000) in the Chicod Creek Watershed.............. 6
Figure 4. Locations of Swine Operations within the Chicod Creek Watershed.................................. 10
Figure 5. Growth in Swine Production Capacity in Chicod Creek Watershed ................................... 11
Figure 6. Cumulative Daily Average Flow Frequency Histogram for USGS Station 02084160........ 14
Figure 7. Daily Fecal Coliform Observations in Chicod Creek at State Road 1760........................... 16
Figure 8. Fecal Coliform Thirty-Day Geometric Means in Chicod Creek at State Road 1760
(based on at least five samples in a 30-day period) ............................................................. 17
Figure 9. Daily Fecal Coliform Observations in the Creeping Swamp Watershed............................. 18
Figure 10. Daily Fecal Coliform Observations in the Van Swamp and Durham Creek Watersheds.... 19
Figure 11. Daily Fecal Coliform Observations at the Upstream Chicod Creek Site............................. 19
Figure 12. Thirty-Day Geometric Means at the Upstream Chicod Creek Site...................................... 20
Figure 13. Comparison of Fecal Coliform Observations at the Upstream and
Primary Monitoring Sites..................................................................................................... 21
Figure 14. Instantaneous Fecal Coliform Load-Duration Curve (400/100 mL) for
Chicod Creek at State Road 1760 Near Simpson, NC......................................................... 30
Figure 15. Geometric-Mean Fecal Coliform Load-Duration Curve for Chicod Creek at
State Road 1760 Near Simpson, NC.................................................................................... 31
Figure 16. Graphical Method for Determining Baseflow Recession in Chicod Creek......................... 32
Figure 17. Load-Duration Characterization of Post-1997 Instantaneous Fecal Coliform
Concentration Data in Chicod Creek................................................................................... 33
Figure 18. Regression Analysis of the Instantaneous Fecal Coliform Load-Duration Curve,
Chicod Creek Data for 1997-2003....................................................................................... 35

Chicod Creek Coliform TMDL April 2004

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SUMMARY SHEET
Total Maximum Daily Load (TMDL)

1. 303(d) Listed Waterbody Information
State: North Carolina
Counties: Pitt, Beaufort
Major River Basin: Tar-Pamlico River Basin
Watershed: Chicod Creek in Tar River Watershed HUC 03020103080010, Waterbody ID 28-101

Impaired Waterbody (2002 303(d) List):
Waterbody Name - (ID) Water Quality Classification Impairment Length (mi)
Chicod Creek (28-101) Class C (aquatic life, secondary
contact recreation), NSW
Fecal Coliform
Bacteria 13.0

Constituent(s) of Concern: Fecal Coliform Bacteria
Designated Uses: Biological integrity, propagation of aquatic life, and secondary contact recreation.
Applicable Water Quality Standards for Class C Waters:
Fecal coliforms shall not exceed a geometric mean of 200/100mL (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.
2. TMDL Development
Analysis/Modeling:
Load duration curves for fecal coliform bacteria were based on cumulative frequency distribution of
flow conditions in the watershed. A predictive upper confidence limit about the regression line on
load versus flow is compared to a criterion limit curve, calculated as the load that would occur at 90
percent of the water quality criterion (thus incorporating a margin of safety). Necessary reductions
in load are calculated as the maximum distance between the confidence bound on the regression
line and the limit curve.
Critical Conditions:
Critical conditions are accounted for in the load curve analysis by determining the difference
between the existing load violation trend line and the allowable load line. This approach was
chosen because existing load violations occur at all flow levels. Maximum reduction requirements
occur at a flow of approximately 100 cfs, which serves as a critical condition for the development
of allocations.
Chicod Creek Coliform TMDL April 2004

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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. Allocation Watershed/Stream Reach
Segment (ID) Existing
Load WLA1 LA MOS2 Reduction
Required TMDL
Chicod Creek
(28-101)
1.05 x 1012
CFU/d
1.35 x 1010
CFU/d
8.67 x 1011
CFU/d
9.79 x 1010
CFU/d 15.9% 9.79 x 1011
CFU/d
Notes:
Loading rates are estimated at the critical flow of 100 cfs.
WLA = wasteload allocation, LA = load allocation, MOS = margin of safety
1WLA = TMDL – LA - MOS; where TMDL is the average allowable load between the 95th
and 10th percent flow exceeded.
2Margin of safety (MOS) equivalent to 10 percent of the target concentration for fecal coliform and turbidity.

4. Public Notice Date: May 8, 2004
5. Submittal Date: July 20, 2004
6. Establishment Date: August 13, 2004
7. Endangered Species (yes or blank):
8. EPA Lead on TMDL (EPA or blank):
9. TMDL Considers Point Source, Nonpoint Source, or both: Nonpoint Source

Chicod Creek Coliform TMDL April 2004
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1 Introduction
1.1 PROBLEM DEFINITION
Section 303(d) of the Clean Water Act (CWA) requires states to develop a list of waters not meeting
water quality standards or which have impaired uses. This list, referred to as the 303(d) list, is submitted
biennially to the U.S. Environmental Protection Agency (EPA) for review. Development of a TMDL
requires an assessment of the assimilative capacity of the stream, assessment of the sources within the
watershed contributing to the total instream load, and a recommendation of the reductions required from
each source.
1.1.1 TMDL Components
The 303(d) process requires that a TMDL be developed for each of the waters appearing on Part I of the
303(d) list. The objective of a TMDL is to estimate allowable pollutant loads and allocate 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 EPA (1991, 2000) and the Federal Advisory
Committee (FACA, 1998) are as follows:
Target identification or selection of pollutant(s) and end-point(s) for consideration. The pollutant and
end-point are generally associated with measurable water quality related characteristics that indicate
compliance with water quality standards. North Carolina indicates known pollutants on the 303(d) list.
Source assessment. All sources that contribute to the impairment should be identified and loads
quantified, where sufficient data exist.
Reduction target. Estimation or level of pollutant reduction needed to achieve water quality goal. The
level of pollution should be characterized for the waterbody, highlighting how current conditions deviate
from the target end-point. Generally, this component is identified through water quality modeling.
Allocation of pollutant loads. Allocating pollutant control responsibility to the sources of impairment.
The wasteload allocation portion of the TMDL accounts for the loads associated with existing and future
point sources. Similarly, the load allocation portion of the TMDL accounts for the loads associated with
existing and future nonpoint sources, stormwater, and natural background.
Margin of Safety. The margin of safety addresses uncertainties associated with pollutant loads, modeling
techniques, and data collection. Per EPA (2000), the margin of safety may be expressed explicitly as
unallocated assimilative capacity or implicitly due to conservative assumptions.
Seasonal variation. The TMDL should consider seasonal variation in the pollutant loads and end-point.
Variability can arise due to stream flows, temperatures, and exceptional events (e.g., droughts,
hurricanes).
Critical Conditions. Critical conditions indicate the combination of environmental factors that result in
just meeting the water quality criterion and have an acceptably low frequency of occurrence.
Section 303(d) of the CWA and the Water Quality Planning and Management regulation (USEPA, 2000)
require EPA to review all TMDLs for approval or disapproval. Once EPA approves a TMDL, then the
waterbody may be moved to Category 4a of the Integrated Report. Waterbodies remain in Category 4a
until compliance with water quality standards is achieved. Where conditions are not appropriate for the
development of a TMDL, management strategies may still result in the restoration of water quality.
Chicod Creek Coliform TMDL April 2004
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1.1.2 Chicod Creek Fecal Coliform Impairment
1.1.2.1 Chicod Creek 303(d) Listing
The Chicod Creek listing of impairment is contained in the North Carolina Water Quality Assessment and
Impaired Waters List (2002 Integrated 305(b) and 303(d) Report). The segment of Chicod Creek
considered impaired due to fecal coliform [Waterbody ID 28-101] extends 13.0 miles from the source to
the Tar River. This segment is listed as partially supporting with agriculture as the potential source of the
impairment.
Chicod Creek is designated a Class C, Nutrient Sensitive Water. The Class C designation requires
protection of aquatic life and secondary contact recreation (NCDENR, 2003). The North Carolina fresh
water quality standard for fecal coliform in Class C waters (T15A:02B.0211) states:
Organisms of the coliform group: fecal coliforms 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; 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.
1.1.2.2 Assessment of Impairment
Monitoring data for Chicod Creek are summarized in Section 1.4. North Carolina bases impairment
status on both the 20-percent criterion of 400 per 100 mL and the geometric mean criterion of 200 per 100
mL (Section 1.1.2.1). For comparison to the instantaneous standard, North Carolina assesses use support
only when at least five samples are available from a 30-day period, in accordance with the water quality
standard. In 1992, sets of five samples from June, July, and August all had more than 20 percent of
individual samples well above the 400 colonies per 100 mL criterion. During the 2003 sampling, two
samples from a five-sample set collected in September had concentrations in excess of 400 colonies per
100 mL, demonstrating continued impairment. Nine percent of individual samples from 1992 to present
are greater than 400 colonies/100 mL; from 1997 to present nine individual samples (7 percent) exceeded
the criterion.
In the case of the geometric mean criterion, only sets of data that include at least five samples
within a 30-day period can be compared to the criterion (200 colonies/100 mL). For the Chicod
Creek analysis, a set was defined as a sample plus all observations occurring in the previous 30
days. All eight geometric means calculated in 1992 were well above the 200 colonies/100mL
criterion (Section 1.4.2). No 30-day geometric means greater than 200 colonies/100 mL have been
documented since 1992, although geometric means at the end of September through beginning of
October 2003 were just below 200. While Chicod Creek was clearly impaired relative to the
geometric mean criterion for fecal coliform in the past, this no longer appears to be the case –
likely due to the installation of BMPs at animal operations.
1.2 WATERSHED DESCRIPTION
Chicod Creek is located in the lower Tar River basin (NC Subbasin 03-03-05) and flows from Beaufort
into Pitt County, joining the Tar River near Grimesland, NC (Figure 1). The watershed drains 40,670
acres of the North Carolina Coastal Plain.
Chicod Creek Coliform TMDL April 2004
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PITT
BEAUFORT
30 0 30 60 90 Miles
Tar/Pamlico Hydrologic Unit
Chicod Creek Watershed
County Boundaries
N

Figure 1. Location of Chicod Creek Watershed in the Tar/Pamlico Basin, NC
1.2.1 Landuse/Land Cover
Landuse data for the Chicod Creek Watershed was tabulated from the USGS National Land Cover
Database (NLCD) compiled in 1992. This is the most recent available comprehensive land cover data set
for the watershed. Changes since this time are expected to have been small, as the watershed has
remained rural and agricultural in nature, with minimal development pressure and no known continuation
of wetland drainage.
The primary drainage area is the portion of the watershed upstream of the flow gage and primary water
quality monitoring site. An additional area in the Roanoke River floodplain drains to the Roanoke
through the lower portion of Chicod Creek (secondary drainage area). The HUC also contains area that
drains directly to the Roanoke, not through Chicod Creek. A landuse map of the HUCs containing the
Chicod Creek Watershed is presented in Figure 2 and data are tabulated in Table 1 for the Chicod Creek
drainage areas only. According to the landuse data, 97.8 percent of the watershed is either forested or
agricultural land: 55.8 percent may be classified as forest or forested wetlands; 33.1 percent as row crop
agriculture; and 8.6 percent as pasture or grass. In the period since 1992, residential land use has likely
increased somewhat, but constitutes only a small portion of the area. The increase in swine operations
since 1992 has likely resulted in some conversion of row crop to grassed sprayfields, which would occur
in the “Pasture/Grass” classification.
Chicod Creek Coliform TMDL April 2004
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N
3 0 3 Miles
NLCD Landuse (1992)
Barren or Mining
Transitional
Agriculture - Cropland
Agriculture - Pasture
Forest
Upland Shrub Land
Grass Land
Water
Wetlands
Low Intensity Residential
Other Grasses (parks, lawns, etc.)
High Intensity Residential
High Intensity Commercial/Industrial
Chicod Creek Subbasins
Chicod Creek

Primary Drainage Area

Secondary Drainage
Area (Floodplain)

Area Drains Directly
To The Tar River

Note: HUCs 03020103080010 and 03020103060030
Figure 2. NLCD Landuse Data for the Chicod Creek Watershed (1992)
Chicod Creek Coliform TMDL April 2004
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Table 1. Landuse Tabulation for the Chicod Creek Watershed
Landuse
Primary
Drainage
Area (ac)
Primary
Drainage
Percentage
Secondary
Drainage
Area (ac)
Secondary
Drainage
Percentage
Entire
Watershed
Area (ac)
Entire
Watershed
Percentage
Residential 400 1.1% 31 0.8% 431 1.1%
Row Crop
11,896
32.5% 1,553 37.9% 13,449 33.1%
Pasture/Grass 3,324 9.1% 193 4.7% 3,517 8.6%
Forest/ Forested Wetlands

20,400 55.8% 2,188 53.5% 22,588 55.5%
Emergent Wetlands/ Water 82 0.2% 128 3.1% 209 0.5%
Commercial/Industrial/Transportation 76 0.2% 0.5 0.0% 77 0.2%
Other1 398 1.1% 0.5 0.0% 398 1.0%
Total 36,576 100.0% 4,094 100.0% 40,670 100.0%
1Other landuses include bare rock, sand, or clay, and transitional areas.
1.2.2 Population and Onsite Wastewater Disposal
Poorly maintained and/or failing septic systems are a common source of fecal coliform contamination in
rural watersheds. In coastal plain watersheds, where the water table is relatively high and has a greater
chance of intersecting the septic drain field, the frequency of contamination may be much higher. During
the period for which monitoring data area available for Chicod Creek, all households in the watershed
were served only by onsite wastewater disposal. In 2004, the Town of Grimesland (population 440 in
2000) completed hooking up to the City of Greenville sewer system. Approximately half of Grimesland’s
Corporate Limits (121 acres) lies within the Chicod Creek watershed. The Village of Simpson
(population 464 in 2000) is also partially within the watershed (149 acres), but does not provide public
sewer service.
Septic tanks are generally associated with low flow exceedances of the fecal coliform standard because
they represent continuous discharges that may be diluted and have less impact during high-flow events.
Other sources of low flow fecal coliform loading are illicit discharges and other direct inputs of raw
sewage. However, in low-lying watersheds, septic tanks may contribute excessive loads during moderate
to high-flow events as water tables rise and meet septic drain fields. If the recharge path to nearby
streams is relatively short, the contaminated groundwater may reach the surface before bacterial die-off
has occurred.
A GIS analysis was performed to determine the total population and number of septic systems within the
Chicod Creek Watershed as well as the relative distributions. Census blocks provided in the BasinPro
GIS data package distributed by the N.C. Center for Geographic Information and Analysis (NCCGIA,
2002) were processed in ArcView to isolate blocks within the watershed. Information on household
sanitary waste disposal methods is no longer available from census data, but given that no sanitary sewers
extend into the Chicod Creek Watershed area from surrounding communities, it was assumed that the
number of septic systems within the watershed could be approximated by the number of households. The
number of households and total population per census block are attributes available within the BasinPro
2000 Census data coverage. All coinciding census blocks that partially intersected the watershed
boundaries were clipped to the extent of the watershed and area-weighted average numbers of households
and total population were calculated within those blocks.
Chicod Creek Coliform TMDL April 2004
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Mills
Ivy
Sis Mills
Beddard
NC Highway 33
Mobleys Bridge
Galloway
Gladson
Hudsons Crossroads
Tucker
Fox Pen
Foster
Lumbuck
Heber Hudson
SmithtownJ C Galloway
Lester Mills
Robert Little
Voa Site B
Blackjack Grimesland
Boyds
Dixon
Blackjack-S
impson Grimesland Bridge
Boyds
Brick Kiln
Ivy
Hudsons Crossroads
Avon
Carrow
Wells
Barr
Barr
Cayton
PITT
BEAUFORT
Simpson
Grimesland
Chicod Creek
Juniper Branch
Cow Swamp
Cabin Branch
Island Swamp
Bates Branch
Cross Swamp
Horseway Swamp
Chicod Creek
Juniper Swamp
Harding Swamp
Municipal Boundaries
Open Water
Wetlands
USGS 1:24,000 Hydrography
Perennial
Intermittent
303(d) Listed Stream Segments
TIGER Roads
County Boundaries
USGS Water Quality Monitoring Station
NCDWQ Ambient Water Quality Monitoring Station

USGS Stream Gaging Stations
Chicod Creek Watershed Boundary
LEGEND
Septic Systems per Square Mile
0 - 25
25 - 50
50 - 100
101 - 250
251 - 500
501 - 1000
1001 - 2500
1 0 1 2 Miles
SCALE
N
EW
S

Figure 3. Septic System Densities by Census Block (2000) in the Chicod Creek Watershed
Chicod Creek Coliform TMDL April 2004
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The GIS analysis indicated that the Chicod Creek Watershed contains approximately 2,400 households
and 6,500 residents. The average septic system density across the 57 square mile Chicod Creek
Watershed (as defined by the USGS 14-digit hydrologic unit 03020103080010) is approximately 42
septic systems per square mile. However, when the densities are mapped by census block (as shown in
Figure 3) it becomes apparent that the systems are by no means distributed evenly throughout the
watershed. Many of the census blocks in the most rural, eastern portion of the watershed have densities
less than 25 systems per square mile. In the western portion of the watershed, nearer to the City of
Greenville, densities exceed 100 systems per square mile and are even higher in small areas within and
around the towns of Simpson and Grimesland. Population within the newly sewered area of Grimesland
accounts for less than 5 percent of the watershed total.
1.2.3 Agriculture
The primary agricultural activities in the Chicod Creek Watershed are row cropping and livestock
production. Most of the row cropland within the watershed is cultivated in the corn-wheat-soybean
rotation that is prevalent across the North Carolina coastal plain. As indicated in Table 1, cultivated row
crops occupy approximately 33 percent of the land area in the primary watershed. Information such as
levels of production, farm characteristics, and best management practices are tracked by the local USDA
Natural Resource Conservation Service (NRCS) office, but records are typically compiled by county so
data is difficult to characterize by watershed. However, in a recent interview, the Pitt County NRCS
District Conservationist, Tim Etheridge, estimated that 25-40 percent of the cultivated cropland within the
Chicod Creek Watershed is associated with tiled drainage systems. Tiled drain systems use drain pipes
buried beneath the surface of fields to convey rainfall away from crops during wet periods and maintain
artificially high water table levels during drought periods (Etheridge, 2004).
In terms of BMP applications, Mr. Etheridge estimated that 10-15 acres of grassed field borders and
grassed drainage swales have been planted in the Chicod Creek Watershed within the last 10 years. Using
the standard 10:1 ratio of affected land area per practice acre installed, only 100-150 acres, or
approximately 1 percent of the cropland in the primary watershed, would be affected by such BMPs. It
was also estimated that 30 percent of the cropland in the watershed is subject to no-till practices during at
least one crop rotation in each annual planting cycle. Application of BMPs to row cropland is limited in
the watershed because the local resource conservation agency staff have focused their efforts in recent
years on improving management practices and BMP applications at large scale livestock facilities
(Etheridge, 2004).
1.2.4 Swine Operations
Most of the livestock production operations in the Chicod Creek Watershed are swine facilities. A
detailed review of the permitting and enforcement files for concentrated animal feeding operations
(CAFOs) in the Washington Regional Office of NCDENR confirm that there are 17 permitted CAFOs in
the Chicod Creek Watershed. The individual swine operations and some of their pertinent characteristics
are listed in Table 2 and their locations within the watershed are shown in Figure 4. As shown in Table 2,
the total design capacity for all facilities in the watershed is slightly over 68,000. Records indicate that
most facilities operate at or above 95 percent of design capacity and that two of the 17 operations are
currently inactive. Accounting for these two factors, the standing population of swine in the watershed is
likely to be in the range of 60,000 – 65,000 animals.
Chicod Creek Coliform TMDL April 2004
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Table 2. Swine Operations Located in the Chicod Creek Watershed
Facility
ID Name
Type of
Operation
Year
Estab.
Design
Population
(animals)
Steady State
Live Weight
(pounds)
Number of
Lagoons
Spray
Acreage
(acres)
Required
Acreage
(acres)
Number of
Illicit
Discharges* Status
74a16 Cloverdale
Farm
Feeder to
Finish 1986 6,000 810,000 1 75.9 75.9 Active
74a18 Rosewood #3 Feeder to
Finish 1994 8,640 1,166,400 1 80 75.4 1 Active
74a19 T&R Sow
Farm
Farrow to
Wean 1985 1,500 649,500 2 30.9 30.9 Active
74a28 Rosewood #2 Feeder to
Finish 1990 3,672 495,720 1 47.1 47.1 Active
74a29 Rosewood
#1A
Feeder to
Finish 1992 3,672 495,720 2 42.9 42.9 1 Active
74a33 Robin Hudson
Farm
Feeder to
Finish 1986 3,280 442,800 2 42.6 42.6 1 Active
74a39 High Ridge
Farms
Farrow to
Feeder 1993 2,400 1,252,800 1 58.4 48.6 Active
74a41 Fairwinds Farrow to
Finish 1993 2,400 1,252,800 1 91.4 91.4 2 Active
74a52 Woodcliff
Farm
Farrow to
Wean 1990 1,600 626,400 1 35 54.4 1 Active
74a57
Peggy
Roberson
Farm
Feeder to
Finish 1981 1,050 141,750 2 74.8 56.8 Active
74a84 Gaskins Pork
Producers
Farrow to
Wean 1978 980 424,340 1 43 34.6 Inactive
74a106 Phillip Page
Farm
Feeder to
Finish 1995 3,672 495,720 1 87.8 69 Active
74a111 Southwoods Farrow to
Feeder 1994 3,600 1,879,200 1 119.5 119.5 Active
Chicod Creek Coliform TMDL April 2004
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Facility
ID Name
Type of
Operation
Year
Estab.
Design
Population
(animals)
Steady State
Live Weight
(pounds)
Number of
Lagoons
Spray
Acreage
(acres)
Required
Acreage
(acres)
Number of
Illicit
Discharges* Status
74a118 Rosewood #4 Feeder to
Finish 1995 7,920 1,069,200 1 168 53.2 2 Active
74a119 Rosewood #5 Feeder to
Finish 1995 5760 777,600 1 50 37.8 Active
74a122 Rosewood
#1B
Feeder to
Finish 1992 3672 495,720 1 39.5 39.5 2 Inactive
7a2 Mills Farm Feeder to
Finish 1993 8640 1,166,400 2 92.7 39.7 2 Active
Total 68,458 13,642,070 22 1179.5 959.3 12
* Illicit discharges varied by facility. For the period 1992-2003, instances included a leaking lagoon, spraying to an oversaturated field, spraying to a tile-drained
field, and direct routing to a stream.
Chicod Creek Coliform TMDL April 2004
10
















Mills
Ivy
Sis Mills
Beddard
NC Highway 33
Mobleys Bridge
Galloway
Gladson
Tucker
Foster Grimes Farm
Lumb
uck
Elks
Heber Hudson
SmithtownJ C Galloway
Lester Mills
Robert Little
VOA Site B
Blackjack Grimesland
Boyds
Dixon
Blackjack-Simpson
Grimesland Bridge
Boyds
Brick Kiln
Ivy
Hudsons Crossroads
Avon
Carrow
Wells
Barr
Barr
Cayton
Hodges
Chicod Creek
Juniper Branch
Cow Sw
a
mp
Cabin Branch
Island Swamp
Bates Branch
Cross Swamp
Horseway Swamp
Chicod Creek
Juniper Swamp
Harding Swamp
TAR RIVER
Chocowinity
Grimesland
Simpson
Greenville
PITT
BEAUFORT
7a2
74a39
74a84
74a19
74a16
74a52
74a41
74a57
74a28
74a18
74a33
74a29
74a106
74a111
74a118
74a119
74a122
Tar-Pamlico River Basin
Chicod Creek Watershed
Municipalities
Open Water
Wetlands
County Boundaries
USGS 1:24,000 Hydrography
Perennial
Intermittent
303(d) Listed Stream Segments
TIGER Roads
USGS Water Quality Monitoring Stations
NCDWQ Ambient Water Quality Monitoring Stations

USGS Stream Gages
LEGEND
N
EW
S
1 0 1 2 Miles
SCALE
Concentrated Swine Operations
Design Capacity (Number of Animals)
0 - 2000
2001 - 4000
4001 - 6000
6001 - 8000
8001 - 10000

Figure 4. Locations of Swine Operations within the Chicod Creek Watershed
Chicod Creek Coliform TMDL April 2004

11
The growth in swine populations in the Chicod Creek Watershed, as well as in the rest of eastern North
Carolina, has been a recent phenomenon. Change over time in design production capacity of swine
operations in the watershed is shown in Figure 5. While some semi-large operations (with capacities of
1000-1500 animals) have been present in the watershed for 20 years or more, Figure 5 shows that up until
1990 the swine population was still around 10,000. In the four years from 1992 through 1995 the
population, in terms of production capacity, grew by approximately 12,500 animals per year. In contrast
to the facilities present prior to 1990, the operations started in the 1992-1995 period tended to be much
larger in scale. There have been no increases in capacity since 1995. In 1997, as a direct result of
problems with the Neuse River estuary and out of broader concerns over potential water quality impacts,
the N.C. Legislature enacted a statewide moratorium on new swine operations with capacities over 250
animals. The moratorium was reauthorized in 2003 for four more years.
0
10,000
20,000
30,000
40,000
50,000
60,000
70,000
80,000
1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995
Swine Population

Note: There has been no increase in swine production capacity since 1995.
Figure 5. Growth in Swine Production Capacity in Chicod Creek Watershed
In all of these operations, large numbers of animals are housed in small quarters, and feces are typically
washed off through the floor into one or two storage lagoons located outside. After some digestion,
wastewater from the lagoons is then sprayed onto grass fields. Each facility is required to develop a
waste utilization plan in conjunction with local resource conservation agency staff and have that plan on
file with NCDWQ. The plans determine sufficient spray field acreage such that wastes can be applied at
agronomic loading rates for nitrogen and phosphorus and liquid will remain on site until removed by
evapotranspiration. However, if spraying occurs just before a heavy rainfall, it is possible that runoff
from the spray fields may reach nearby streams prior to nutrient uptake and/or fecal coliform die off. As
shown in Table 2, the swine operations in the Chicod Creek Watershed utilize 22 waste lagoons and
almost 1,200 acres of spray irrigation fields. Collectively, the waste utilization plans for the facilities
only call for approximately 950 acres of spray fields, but some facilities have a larger acreage than
required to provide a margin of safety.
Chicod Creek Coliform TMDL April 2004

12
1.2.4.1 Regulation of Swine Operations and Enforcement Efforts
In 1997, legislation was enacted requiring the formal permitting of CAFOs along with development of
waste utilization plans and biannual inspections. Prior to that legislation, few records are available to
characterize management efforts at swine operations. Review of the permitting and enforcement files
indicated that many operations were seldom or never inspected prior to 1997 unless reports of illicit
discharges or other severe problems caused regulators to visit a given facility. Once a discharge or other
problem was observed at a facility, that operation was typically designated as a CAFO and a formal letter
was transmitted to the owner notifying them of the designation. After designation, facilities appeared to
be tracked more closely and inspected on occasion.
In general, the problems reported at swine facilities were more severe in the years prior to the requirement
for regular inspections with events such as straight pipes or other direct flows from hog houses or lagoons
to nearby streams. After 1997, the most common type of recorded illicit “discharge” resulted from
irrigating on saturated spray fields. A comprehensive review of the CAFO files showed that at least 12
illicit discharge events from 1987 through 2002 which resulted in swine waste entering surface waters
from facilities in the Chicod Creek Watershed. The NCDWQ enforcement files reflected that all but one
or two of these events were referred for enforcement action which resulted in monetary fines paid by the
owners.
Lagoon failure may also cause fecal coliform loading by discharging large volumes of waste to the
surrounding area. These events can occur during wet or dry conditions and happen less frequently than
waste runoff from spray fields. No catastrophic lagoon failures have been reported in the Chicod Creek
Watershed.
It is likely that some discharge events go unnoticed by regulatory staff. In many cases, discharges were
reported because citizens within the watershed saw waste draining off fields or across roadways. Many of
the swine operations within the watershed, and across the eastern portion of the state, are in very remote
locations nowhere near housing or public roadways. The legislation passed in 1997 to establish the
process for permitting and inspection of CAFOs in North Carolina stipulated that regulatory staff from
NCDWQ inspect each facility for compliance once per year and that resource agency staff visit each
facility once a year for evaluation and consultation to maintain and improve waste management efforts.
While the resource agency staff are not intended to have a regulatory role, they do have the authority to
refer problems they encounter to the regulatory agency for follow-up inspection and enforcement. As a
result, when sufficient staff resources are available within the two agencies, each swine operation is
visited twice per year. However, it should be noted that during the time of Tetra Tech’s review of the
permitting and enforcement files, only three staff were assigned to inspecting CAFOs within the
Washington Regional Office territory for NCDWQ. That territory consists of 21 northeastern counties,
which contain over 500 CAFOs that are almost all swine operations. Considering the administrative
demands and travel time associated with carrying out such an effort, the current staffing level may not be
sufficient to ensure the desired frequency of inspections of these facilities.
1.2.4.2 Best Management Practices at Swine Operations
Interviews with the Pitt County NRCS District Conservationist, Tim Etheridge, have indicated that no
database or tracking system exists that would have a formal record of the BMPs that have been instituted
at swine facilities within the Chicod Creek Watershed. However, the interviews also revealed that Mr.
Etheridge worked in conjunction with NCDWQ staff and staff from the Division of Soil and Water
Conservation during a period from approximately 1991-1994 to identify problem swine facilities and
implement best management practices at those facilities. He and field staff from the NCDWQ Regional
office systematically visited all swine operations within the watershed and developed a list of high
priority facilities exhibiting the greatest levels of operational deficiencies and targeted them for
improvement. Operations at each swine facility were reviewed and opportunities for management and
Chicod Creek Coliform TMDL April 2004

13
structural improvement were identified. Through the use of Clean Water Act Section 319 grant monies,
BMPs such as increased vegetated buffers between spray areas and waterways, increased spray acreage to
minimize overloading of wastes, and improved cover crops for spray fields were implemented at each
facility as necessary (Etheridge, 2004). While no formal report is available from which to quantify these
efforts, it should be noted that a significant decrease in the measured levels of fecal coliform in Chicod
Creek coincides with this time period (see Section 1.4).
1.2.5 Other Livestock Operations
A 1995 USGS publication evaluating land use and nutrient concentrations in the Albemarle – Pamlico
drainage area reported that, as of 1994, poultry growing facilities containing approximately 470,000 birds
were located in the Chicod Creek Watershed (Woodside and Simerl, 1995). Interviews with the Pitt
County District Conservationist have indicated that, at that time, at least two layer operations and two
broiler operations were present in the watershed. The layer operations were depopulated around 1999 to
2001. It should be noted that the layer operations employed wet waste management systems with lagoons
and spray fields not unlike swine production facilities. In addition, reduced demand prompted a reduction
in the geographic range of suppliers for the primary broiler chicken processing facility in the region, and
the two broiler operations in Chicod Creek were depopulated in 2003. As a result, no active poultry
growing facilities are present in the Chicod Creek Watershed at this time (Etheridge, 2004). However,
the structural facilities to support these operations are still in existence and future increases in poultry
demand could cause them to be restarted.
Applications for CAFO permits require that the applicant list all other livestock present on the farm in
question other than the subject CAFO. Review of the NCDWQ CAFO permit files indicated that
approximately 75 head of beef cattle and 9 goats are kept on farms within the Chicod Creek Watershed.
Interviews with the Pitt County District Conservationist confirmed these low numbers of livestock other
than swine in the watershed (Etheridge, 2004).
1.3 FLOW GAGING
USGS has monitored stream flow at Station 02084160 (Chicod Creek at SR1760 near Simpson, NC)
since 1975, with a gap from 4/15/1987 to 4/30/1992. Data were obtained from the USGS NWIS system,
including provisional data updated through February 12, 2004. The station is located in Pitt County at
35°33'47" latitude and 77°13'43" longitude NAD27 and has a reported drainage area of 45 square miles.
Summary statistics for this station through December 2003 are listed in Table 3. A cumulative frequency
histogram for the monitoring period is presented in Figure 6. Low flows are frequent in this system, with
22 percent of recorded flows at 2 cfs or less.
Table 3. Daily Average Stream Flow Statistics for USGS Station 02084160
Chicod Creek at SR1760 Near Simpson, NC, Oct. 1975 – Dec. 2003
Count (days) 8474
Minimum (cfs) 0
Maximum (cfs) 4560
Average (cfs) 55.1
Median (cfs) 12

Chicod Creek Coliform TMDL April 2004

14
Histogram
0
100
200
300
400
500
600
700
0.
1
0.
3
0.
5
0.
7
0.
9
2 4 6 8 10 20 30 50 70 90
15
0
50
0
15
0
0
30
0
0
50
0
0
Flow Ranges
0%
20%
40%
60%
80%
100%
120%
Frequency Cumulative %

Figure 6. Cumulative Daily Average Flow Frequency Histogram for USGS Station 02084160
1.4 WATER QUALITY MONITORING
1.4.1 Monitoring Sites
Fecal coliform data have been collected in the Chicod Creek Watershed at State Road 1760 by USGS and
NC DWQ from November 1977 to the present (USGS Station 02084160; DWQ Station O6450000). This
station is part of the USGS Albemarle-Pamlico National Water Quality Assessment (NAWQA) study.
The Chicod Creek Watershed underwent drainage modifications from November 1978 to December
1981, and USGS monitored hydrologic conditions and water quality before, during, and after
modification as part of their environmental impact assessment (Mason, 1988; Watkins and Simmons,
1984; Mason et al., 1990). The station at SR 1760 is referred to as the “primary site” because it
represents the majority of data collected in the watershed and is near the outlet of the listed reach.
USGS also monitored water quality and ground water levels at two sites in the Creeping Swamp
Watershed (USGS Stations 02091960 and 02091970), which is just south of the Chicod Creek watershed.
The Creeping Swamp stations were used as control sites to compare the impacts of hydrologic
modifications in the Chicod Creek Watershed. The Creeping Swamp Watershed has similar soils, stream
characteristics, and landuses as the Chicod Creek Watershed. Both contain animal operations, though
Chicod Creek has a higher density based on visual interpretation of 1998 1-meter resolution aerial
photography. These sites are referred to as “control sites” in this document.
Tetra Tech selected two additional USGS NAWQA sites to compare water quality conditions in Chicod
Creek to undisturbed bottomlands with no agriculture or animal operations. These sites are located on
Durham Creek near Edward, NC (USGS Station 02084540) and Van Swamp near Hoke, NC (USGS
Station 02084557) and are referred to as “reference sites” in this document.
Chicod Creek Coliform TMDL April 2004

15
Fecal coliform data were also collected by NCDWQ for a brief time along Chicod Creek at Boyd’s
Crossroads (NCDWQ Site ChC1). This site is referred to as the “upstream site” because it is upstream of
the primary site as well as most of the swine facilities in the watershed. One facility was identified just
upstream of Boyd’s Crossroads.
Table 4 summarizes the monitoring sites used in this study.
Table 4. Fecal Coliform Monitoring Stations for the Chicod Creek Analysis
Site Number Site Name Type Monitoring Period
02084160 Chicod Creek at SR1760 near Simpson, NC Primary Nov-77 to Oct-03
02091960 Creeping Swamp near Calico, NC Control Oct-74 to May-75
02091970 Creeping Swamp near Vanceboro, NC Control Oct-74 to May-86
02084540 Durham Creek at Edward, NC Reference Mar-93 to Aug-93
02084557 Van Swamp near Hoke, NC Reference Mar-78 to Feb-94
ChC1 Chicod Creek at Boyd’s Crossroads Upstream Sep-03 to Oct-03

1.4.2 Primary Chicod Creek Monitoring Site
Fecal coliform data are generally discussed in terms of daily observations or 30-day geometric means of
at least five samples. At the primary monitoring site along Chicod Creek, 206 daily observations were
collected from November 1977 to October 2003 ranging from 9 to 31,000 colonies/100 mL. Daily
observations at this site are shown in Figure 7 along with the 20-percent of individual samples in a 30-day
period or “instantaneous” criterion of 400 colonies/100 mL. The magnitude of concentrations has
decreased substantially over the past two decades. Concentrations greater than 30,000 occurred in the
1980s, but concentrations greater than 3,500 have not been observed since 1992. The frequency of
excursions of the instantaneous criterion also decreased from 42 percent prior to the end 1992 to 9 percent
after 1992.
Chicod Creek Coliform TMDL April 2004

16
1
10
100
1,000
10,000
100,000
1/1/77 6/24/82 12/15/87 6/6/93 11/27/98 5/19/04
Fe
c
a
l

C
o
l
i
f
o
r
m

(
#
/
1
0
0

m
L
)
Daily Observations Instantaneous Standard

Figure 7. Daily Fecal Coliform Observations in Chicod Creek at State Road 1760

Thirty-day geometric means may be calculated for 19 sets of fecal coliform observations that have at least
five samples. Geometric means were calculated for all samples within 30-days of the last sampling date if
at least five samples were taken. This translates to a rolling average for the prior 30 days for all
applicable samples within the window. Analysis of 30-day windows centered on each sampling point
yields similar results. The geometric means are plotted in Figure 8. Eight geometric means are calculated
during the summer of 1992 ranging from 763 to 1,401 colonies/100 mL. Two geometric means are
calculated during 1997 having values of 32 and 103 colonies/100 mL. Nine geometric means are
calculated during 2003 ranging from 42 to 199 colonies/100 mL. All geometric means calculated during
1992 exceeded the geometric mean criterion of 200 colonies/100 mL; none exceeded the criterion after
1992.
Chicod Creek Coliform TMDL April 2004

17
-
200
400
600
800
1,000
1,200
1,400
1,600
1/1/92 5/15/93 9/27/94 2/9/96 6/23/97 11/5/98 3/19/00 8/1/01 12/14/02
Ge
o
m
e
t
r
i
c

M
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a
n

(
#
/
1
0
0

m
L
)
Geometric Mean Geometric Mean Standard

Figure 8. Fecal Coliform Thirty-Day Geometric Means in Chicod Creek at State Road 1760 (based
on at least five samples in a 30-day period)

Water quality BMPs funded through Section 104 (b) (3) of the Clean Water Act were installed throughout
the Chicod Creek Watershed between 1994 and 1997. Animal waste controls included anaerobic waste
lagoons, stormwater management controls, dry manure storage facilities, waste application systems, and
the closure of abandoned swine waste lagoons (NCDENR, 1999). It appears that these BMPs were
effective in reducing fecal coliform concentrations and geometric means. The frequency of excursions of
the instantaneous standard decreased from 42 percent to 9 percent, and the frequency of excursions of the
geometric mean standard decreased from 100 percent to 0 percent.
1.4.3 Control Sites in the Creeping Swamp Watershed
Fecal coliform data were collected by USGS at two sites in the Creeping Swamp Watershed. The
watershed is 70 percent forest, 25 percent agriculture, and 5 percent rural development (Mason, 1988),
and some animal operations are present. Figure 9 shows daily observations at the two Creeping Swamp
sites combined. No five-samples occur within a 30-day period to calculate a geometric mean.
Daily observations of fecal coliform are generally lower at Creeping Swamp compared to the primary site
on Chicod Creek for the period prior to 1997. No observation exceeds 1,000 colonies/100 mL. Four of
twenty-four observations are greater than the instantaneous standard of 400 colonies/100 mL. However,
concentrations are in the same range as more recent observations in Chicod Creek. Agriculture and
animal operations present in this watershed may elevate fecal coliform concentrations above background
concentrations seen in sites without anthropogenic disturbance.
Chicod Creek Coliform TMDL April 2004

18
-
200
400
600
800
1,000
1,200
8/1/1974 8/20/1976 9/9/1978 9/28/1980 10/18/1982 11/6/1984 11/26/1986
Fe
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C
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i
f
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m

(
#
/
1
0
0

m
L
)
Daily Observations Instantaneous Standard

Figure 9. Daily Fecal Coliform Observations in the Creeping Swamp Watershed
1.4.4 Reference Sites in Van Swamp and Durham Creek Watersheds
Fecal coliform data collected at the reference sites at Van Swamp and Durham Creek were combined for
comparison to the Chicod Creek data. These sites are located in relatively undisturbed, swampy
watersheds with no animal operations and limited agriculture. As expected, fecal coliform concentrations
are relatively low. Daily observations are shown in Figure 10; none exceed the instantaneous standard of
400 colonies/100 mL. No five-sample 30-day geometric means can be calculated from the available data
at the reference sites.
Results from these sites suggest that the water quality criteria are likely to be achieved in this topography
when agriculture, animal operations, and human sources, such as septic tanks, are not present in
significant numbers.
Chicod Creek Coliform TMDL April 2004

19
-
200
400
600
800
1,000
1,200
6/1/1977 2/26/1980 11/22/1982 8/18/1985 5/14/1988 2/8/1991 11/4/1993
Fe
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C
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i
f
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m

(
#
/
1
0
0

m
L
)
Daily Observations Instantaneous Standard

Figure 10. Daily Fecal Coliform Observations in the Van Swamp and Durham Creek Watersheds
1.4.5 Chicod Creek Upstream Site at Boyd’s Crossroads
Fecal coliform data were collected at Chicod Creek at Boyd’s Crossroads during the late summer/early
fall of 2003. Two of eleven samples exceeded the instantaneous fecal coliform standard of 400
colonies/100 mL (Figure 11).
-
200
400
600
800
1,000
1,200
8/17/03 8/27/03 9/6/03 9/16/03 9/26/03 10/6/03 10/16/03 10/26/03 11/5/03
Fe
c
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C
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i
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(
#
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1
0
0

m
L
)
Daily Observations Instantaneous Standard

Figure 11. Daily Fecal Coliform Observations at the Upstream Chicod Creek Site
Chicod Creek Coliform TMDL April 2004

20
The 11 paired upstream-downstream samples include a wide range of flow conditions, ranging from
~0 cfs (10/9 and 10/28) to 88 and 215 cfs (9/23 and 9/30). The latter two flows fall near the 15th and 5th
percentiles of the flow distribution. The majority of the other points are in the range of 35-45th percentile
flows.
Seven 30-day geometric means are calculated for the upstream site. None exceed the geometric mean
standard of 200 colonies/100 mL (Figure 12).
-
200
400
600
800
1,000
1,200
8/17/03 8/27/03 9/6/03 9/16/03 9/26/03 10/6/03 10/16/03 10/26/03 11/5/03
Ge
o
m
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M
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(
#
/
1
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0

m
L
)
Geometric Mean Geometric Mean Standard

Figure 12. Thirty-Day Geometric Means at the Upstream Chicod Creek Site
It is of interest to compare daily observations at the upstream site to the primary site. Given the number
of swine operations draining to creek between the primary site and the upstream site, which has only one
swine operation in its drainage area, an increase in concentration would be expected if the swine
operations were a significant source of coliform load. The concentrations are quite similar, however, and
on some days, the concentration at the upstream site is greater than at the primary site (Figure 13). Each
site has two excursions of the instantaneous standard. This suggests that, at least under 2003 conditions,
there is little evidence for an increase in loading rate associated with swine operations in the Chicod
Creek watershed. Instead, loading rates appear to be fairly consistent across the watershed.
Chicod Creek Coliform TMDL April 2004

21
-
200
400
600
800
1,000
1,200
8/27/03 9/6/03 9/16/03 9/26/03 10/6/03 10/16/03 10/26/03 11/5/03
Fe
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)
Upstream Site Primary Site Instantaneous Standard

Figure 13. Comparison of Fecal Coliform Observations at the Upstream and Primary Monitoring
Sites
1.4.6 Comparison of Fecal Coliform Statistics at Monitoring Stations
Table 5 compares the frequency of excursions of both the instantaneous and geometric mean criteria for
each site type. The primary site has the greatest number of excursions of both the instantaneous criterion
(21 percent) and the geometric mean criterion (42 percent). This site also drains the greatest area of
agricultural land and all of the swine operations in the Chicod Creek Watershed. The upstream site on
Chicod Creek has no excursions of the geometric mean criterion, but exceeds the instantaneous criterion
in 18 percent of observations. This site drains one known swine operation (Mills Farm, with a design
capacity of 8,640 animals (see Table 2), but which has an animal density much less than does the
downstream station (436 vs. 1,197 swine/mi2). The reference site has no excursions of the instantaneous
criterion and drains no agricultural land or animal operations; a geometric mean could not be calculated
with the available data, but no individual observations exceeded 200 colonies/100 mL. The control sites,
which drain less agricultural land and animal operations compared to the primary site, exceed the
instantaneous criterion in 17 percent of the observations. Data were not available at the control sites to
calculate geometric means.
Chicod Creek Coliform TMDL April 2004

22
Table 5. Comparison of Excursions of Fecal Coliform Criteria in the Chicod Creek Watershed
and the Reference and Control Sites (period of record)
Sites
Number of
Observations
Frequency of Excursions of
the Instantaneous Criterion
Frequency of Excursions of the
Geometric Mean Criterion
Primary 206 21% 42%
Control 24 17% na1
Reference 23 0% na1
Upstream 11 18% 0%
1 No 30-day sets of at least five samples were present in the data set.
Chicod Creek Coliform TMDL April 2004

23
2 Source Assessment
A critical step in developing a useful and defensible TMDL is the assessment of potential sources. Tetra
Tech performed a watershed-wide review of sources that potentially contribute to fecal coliform loading.
Geographical information systems and digital orthophotos were used to gain an understanding of the
sources within the watershed. Discussion with local jurisdictions and field personnel were also used to
identify and quantify potential sources.
Both point and nonpoint sources may contribute fecal coliform to the waterbodies. Potential sources of
fecal coliform loading are numerous and often occur in combination. In rural areas, runoff can transport
significant loads of fecal coliform from sources such as agricultural activities and wildlife contributions.
Septic systems, illicit discharges, broken sewer pipes, and stormwater runoff can be potential sources in
urban areas.
Potential sources of fecal coliform loading in the watershed were identified based on an evaluation of
current landuse/cover, animal operations, and septic systems. The source assessment was used as the
basis of development of the model and ultimate analysis of the TMDL allocations.
2.1 POINT SOURCE FECAL COLIFORM CONTRIBUTIONS
There are no permitted point sources in the Chicod Creek Watershed.
2.2 NONPOINT SOURCE FECAL COLIFORM CONTRIBUTIONS
Runoff from landuses in the watershed can contribute significant fecal coliform loading to streams. The
Chicod Creek Watershed is primarily rural, so stormwater runoff most likely carries fecal coliform from
wildlife, domestic animals, pasture lands, animal operations, and other agricultural lands to nearby
streams.
Research was performed to assess the most probable nonpoint sources of fecal coliform. Information on
sources was gathered from GIS information, census data, and personal communication with local and
state officials. The principal sources investigated were landuse distribution, septic systems, swine and
poultry operations, and the populations of wildlife and domestic animals.
Based on the landuse distribution, the flow-duration analysis, and the parameter correlation, it appears
that swine operations were the most significant contributor to fecal coliform loading prior to BMP
installation. After BMP installation swine operations, agriculture fields, and wildlife are each likely
sources of contamination, though the frequency of instantaneous excursions has decreased significantly.
Timber harvesting likely exacerbates fecal coliform loading for a few years following harvesting.
2.2.1 Interpretation of Monitoring Data for Nonpoint Sources
A flow-duration curve analysis was performed to identify the flow regimes during which excursions of
the water quality criteria occur (see Section 3.1). Excursions that occur only during low-flow events
(flows that are frequently exceeded) are likely caused by continuous or point source discharges, which are
generally diluted during storm events. Excursions that occur during high-flow events (flows that are not
frequently exceeded) are generally driven by storm-event runoff. A mixture of point and nonpoint
sources may cause excursions during normal flows.
The flow-duration analysis was presented by monitoring period relative to 1997, which was when most of
the water quality BMPs were functioning in the watershed. The majority of excursions of the
instantaneous fecal coliform criterion (400 colonies/100 mL), before and after BMP implementation,
Chicod Creek Coliform TMDL April 2004

24
occurred during higher flows. Only one excursion (observed load 4 percent over standard load) coincided
with a flow exceeded 80 percent of the time. Excursions by flow regime are summarized in Table 6.
Fifty-six percent of all excursions occur during the highest 20 percent of flows, 42 percent occur during
moderate flows, and 2 percent occur during the lowest 20 percent of flows. This distribution suggests that
storm event washoff is the likely source of most excursions of the fecal coliform criterion. Storm event
loads may include washoff of freshly applied animal waste from sprayfields in this watershed; however,
the comparison of upstream and downstream stations in 2003 (Section 1.4.5) suggests that fecal coliform
concentrations are not strongly correlated with position in the watershed relative to animal operations.
Table 6. Number of Excursions of the Instantaneous Fecal Coliform Criterion of 400 per 100 mL.
Classified by Flow Regime
Flow Regime (Percent of Time Flows
Exceeded)
Pre-1/97
Monitoring
Post-1/97
Monitoring
Complete Monitoring
Period
0% - 20% (high flows) 19 5 24
20% - 80% (moderate flows) 15 3 18
80% - 100% (low flows) 0 1 1
All flows 34 9 43

To assess the sources of fecal coliform contamination in the Chicod Creek Watershed, a correlation of
ammonia, dissolved phosphorus, turbidity, and organic carbon to fecal coliform was performed for the
USGS Station at Chicod Creek at SR 1760. A strong correlation between ammonia and dissolved
phosphorus with fecal coliform concentration would suggest the swine operations as a major source in the
watershed because sprayed lagoon waste contains high concentrations of these dissolved nutrients (Mallin
et al., 1997). A strong correlation between ammonia and organic carbon with fecal coliform
concentration would suggest malfunctioning septic systems as a potential source. A strong correlation of
turbidity with fecal coliform concentration would point to other sources in the watershed such as wildlife
whose waste would be washed off during storm events along with upland sediment. High turbidity can
also result from lagoon failure, but it is not considered a continuous source of fecal coliform loading and
would not result in a correlation with long-term monitoring data.
Parameter correlation was performed for two monitoring periods to assess the impacts of BMPs that were
installed in the watershed between 1994 and 1997. Prior to January 1997, the ammonia to fecal coliform
correlation was 0.91; after January 1997 it dropped to 0.09. The correlation of dissolved phosphorus to
fecal coliform was 0.15 prior to 1997; no dissolved phosphorus measurements were collected after
January 1997. Turbidity was not collected prior to January 1997, but correlation to fecal coliform after
January 1997 was 0.33. Organic carbon was not collected after January 1997, but has a correlation of
0.29 prior to that date. Together, these results suggest that swine waste was a major source of coliform
loading prior to 1997, but has decreased in importance since that time.
Fecal streptococci generally occur in the digestive systems of humans and other warm-blooded animals.
In the past, fecal streptococci were monitored together with fecal coliforms and a ratio of fecal coliforms
to streptococci was calculated: this ratio was used to determine whether the contamination was of human
or nonhuman origin. However, this is no longer recommended as a reliable test (US EPA, 1986).
One common rule of thumb was that fecal coliform to fecal streptococci ratios from human waste would
have ratios greater than 4, and from animal waste less than 4. Only 1 of 23 samples at the water quality
reference sites had a ratio greater than 4 (4.5); only 1 of 21 samples at the hydraulic control sites had a
ratio greater than 4 (4.8); no fecal streptococci data was available at the upstream Chicod site; at the
Chicod Creek Coliform TMDL April 2004

25
downstream Chicod site, 4 of 92 ratios are greater than 4 with values of 4.3, 5.1, 10.0, and 18.4. Though
the method is now considered questionable, it would have suggested that contamination in the Chicod
Creek Watershed was due to animal sources rather than human sources.
2.2.2 Agriculture
Fecal coliform loads from agriculture derive from domestic animals, wildlife, and wildfowl. Row crop
fields have high runoff volumes compared to most other rural landuses. Concentrated food stores often
attract wildlife to fields. Pastureland used for cattle grazing can contribute high concentrations of fecal
coliform bacteria, especially if BMPs are not utilized.
According to the 1992 USGS NLCD landuse data, 33.1 percent of the Chicod Creek Watershed is used
for row crop agriculture and 8.6 percent is used for pasture land. Row crops are a likely source of past
and present fecal coliform loading because (1) row crop fields are known sources of fecal coliform and
sediment loading during rainfall/runoff events, (2) most excursions occurred during rainfall events, and
(3) fecal coliform was correlated to turbidity (0.33) after BMP implementation (turbidity was not
monitored prior to BMP implementation).
Pastureland is not as significant in the Chicod Creek Watershed based on relative area. Although the
NLCD landuse/land cover data shows approximately 3,300 acres of pasture in the primary watershed
(Table 1), review of the CAFO permitting files has indicated that only 75 head of beef cattle are present in
the watershed (Section 1.2.5). Note that some of the land classified as pasture in the satellite-based
NLCD data is actually grassed spray irrigation fields associated with swine operations.
2.2.3 Animal Operations
The high correlation between ammonia and fecal coliform prior to January 1997 suggests that liquid
wastes, such as swine lagoon effluent or septic system effluent, were a major contributor to fecal coliform
loading. Neither dissolved phosphorus nor organic carbon correlate strongly with fecal coliform, but the
high number of swine relative to the number of septic systems does suggest that swine operations were a
more likely source. The fact that the correlation dropped 10-fold after animal waste BMP implementation
also supports this conclusion because the loads from septic systems would not have been affected by the
BMPs. The animal waste BMPs appear to be functioning well in this watershed though there may be
some room for improvement. However, after 1997, there is no evidence that isolates swine operations as
the major source of loading.
2.2.4 Onsite Wastewater Disposal
Failing septic tanks are generally associated with low-flow excursions of the fecal coliform standard
because they represent continuous discharges that impact baseflows, but that are often diluted and less
apparent during high rainfall periods. Other sources of low flow fecal coliform loading are illicit
discharges and other direct inputs of raw sewage. According to the flow duration analysis, only one
excursion of the fecal coliform criterion occurred during low flows, suggesting that failing septic systems
are not the major source of fecal coliform load in the watershed.
In low-lying watersheds such as Chicod Creek, septic tanks may contribute excessive loads during
moderate to high-flow events as water tables rise and meet septic drain fields. If the recharge path to
nearby streams is relatively short, the contaminated groundwater may reach the surface before bacterial
die-off has occurred.
With a properly functioning septic system, effluent is typically characterized by high nitrate
concentrations and low organic carbon concentrations because ammonia and organic carbon are oxidized
Chicod Creek Coliform TMDL April 2004

26
to nitrate and CO2, respectively, in the unsaturated drainfield. If the water table rises into the drain field,
these processes are less likely to occur and ammonia and organic carbon concentrations remain high.
Though ammonia is strongly correlated to fecal coliform concentrations prior to 1997 (0.91), organic
carbon is poorly correlated (0.27). Given the other likely sources of ammonia and fecal coliform in the
watershed and the small number of septic systems, septic systems are not indicated as a major source of
fecal coliform excursions in the watershed.
2.2.5 Impacts of Silviculture
Much of the forested land in the Chicod Creek Watershed is used for silviculture, though it is not apparent
from the NLCD database what fraction of the forest is managed. Fecal coliform loads in forestland derive
primarily from wildlife. Timber harvesting has been correlated with elevated fecal coliform loads due to
the altered hydrology of the forest system after harvest (Ensign and Mallin, 2001; Mallin et al., 2001).
Contaminated runoff that flows through an intact forest is typically infiltrated before reaching a stream.
Clearcutting and harvesting practices shorten runoff pathways and reduce infiltration, allowing more
runoff to reach the stream more quickly. Clearcutting also reduces evapotranspiration, which results in
higher water tables and runoff volumes.
A water quality study in the coastal plains of North Carolina showed that clearcutting resulted in
significantly higher concentrations of suspended solids, nutrients, and fecal coliform bacteria. Ensign and
Mallin (2001) compared water quality at two adjacent watersheds with similar hydrology, landuse
patterns, and density of animal operations. The Goshen Swamp Watershed is 52.5 percent forest, 46.0
percent agriculture, 1.0 percent urban, and has a swine density of 705/km2. The Six Runs Creek
Watershed is 62.6 percent forest, 36.4 percent agriculture, 1.1 percent urban, and has a swine density of
665/km2. One hundred thirty acres (outside of a 10-m stream buffer) of the Goshen Swamp Watershed
were clear-cut during May through September of 1998; Six Runs Creek was used as the control watershed
and no clearcutting occurred. All North Carolina best management practices were observed during the
study and no violations were found.
Water quality was monitored before, during, and after the clearcutting period in both watersheds. The
mean fecal coliform concentration in the Goshen Swamp Watershed increased from 116 colonies/100 mL
to 1,993 colonies/100 mL after clearcutting with a maximum concentration of 23,400 colonies/100 mL.
Prior to clearcutting, concentrations above 330 were not observed. Fecal coliform concentrations
remained elevated well into 1999 (last reported monitoring) with 3,510 colonies/100 mL observed in July.
During the pre- and post-clearcutting monitoring periods at the Six Runs Creek reference site, mean fecal
coliform concentrations were 143 and 244 colonies/100 mL, respectively. Though the mean increased by
70 percent, the concentrations remained relatively low compared to Goshen Swamp Creek. During the
pre-clearcutting monitoring period, the maximum fecal coliform concentration observed at Six Runs
Creek was 1,100 colonies/100 mL; in the period after clearcutting at Goshen Swamp the maximum
concentration was 3,020 colonies/100 mL. Again, the magnitude of increase is low relative to that seen in
Goshen Swamp.
Both watersheds experienced excursions of the North Carolina instantaneous fecal coliform standard (400
colonies/100 mL) prior to the clearcutting that occurred in the Goshen Swamp watershed. Excursions
were likely due to swine operations. Once clearcutting occurred, increases in fecal coliform
concentrations in the control watershed were minor compared to the clearcut watershed. Though timber
harvesting is not a direct source of fecal coliform loading, altered hydrology does appear to impact water
quality and increase fecal coliform loading to streams.
Another study reported the impacts of timber harvesting on a coastal watershed. Mallin et al. (2001) used
closure of shell-fish waters to identify fecal coliform impacts. Mallin et al. report that 1,100 acres of
Chicod Creek Coliform TMDL April 2004

27
harvesting waters in Carteret County were closed for three years following a forest clearcut. The direct
sources of fecal coliform were not identified.
Public data on the acreage of managed forest in the Chicod Creek Watershed is not available. In addition,
the forest industry is not required to notify the Division of Forest Resources when clearcutting or timber
harvesting occur, but the forest service does track reforestation by county (Raval, 2004). Pitt County
currently has 208,306 acres of forestland. During the period January 1, 1997 through December 31, 2002,
12,000 acres were reforested (approximately 5.8 percent of total forest).
1998 DOQQs for the Chicod Creek watershed show extensive managed pine plantations, particularly in
the southern part of the watershed. On the land use coverage (Table 1) there are a total of 20,400 acres in
forest and forested wetland. Assuming that all of this land is in silviculture and is predominantly loblolly
pine with a rotation period of 30 years, on average only 680 acres per year would be harvested. Even if
increased coliform loads persisted for three years, the average area affected (2,040 acres or less) would be
much smaller than the amount of active agricultural land (greater than 15,000 acres).
From available information, we are not able to match timber harvesting with particular water quality
excursions in Chicod Creek. It is likely that harvesting has occurred since 1997 and may have led to
some increase in fecal coliform concentrations in streams near harvesting sites. However, given the
expected rotation period for timber harvest, it appears unlikely that silviculture is a major source of
bacterial load above natural background relative to agricultural land uses.
2.3 ANALYSIS OF EXISTING MANAGEMENT MEASURES
As discussed in Section 1.4.2, there was a significant decrease in fecal coliform concentrations in Chicod
Creek in the early 1990s. Based on NC DENR’s “Final Report on BMP Implementation in the Tar-
Pamlico River Basin” (1999), the majority of installed animal waste management BMPs were operational
by early 1997. Discussion with local NRCS staff suggests that farmer education was increased and better
operating practices were encouraged from 1992 to 1993. The sharp decline in fecal coliform observations
after 1992 leads to the conclusion that education, improved operating procedures, and water quality BMPs
have significantly improved water quality in the Chicod Creek Watershed. Prior to January 1993, 42
percent of fecal coliform observations exceeded the instantaneous criterion of 400 colonies/100 mL.
After January 1993, the frequency decreased to 9 percent. The frequency of exceeding the geometric
mean standard decreased from 100 percent in 1992 to 0 percent in 1997 and 2003.
2.4 CONCEPTUAL MODEL OF FECAL COLIFORM IN CHICOD CREEK
Runoff from animal waste management dominated bacteriological conditions in the Chicod Creek
watershed in the early 1990s. Installation of BMPs and development of waste management plans in the
mid-1990s appears to have drastically reduced the significance of this source. For the period since 1997,
fecal coliform concentrations in Chicod Creek have continued to occasionally exceed water quality
criteria, but not by a large amount.
Under current conditions, the major source of bacterial load to Chicod Creek appears to be storm washoff
from agricultural land (including, but not limited to sprayfields), with some additional input in excess of
natural conditions from clearcut forest and other land uses. Loading during washoff events is likely
exacerbated by the extensive use of artificial drainage in the watershed and relatively low level of efforts
to implement cropland BMPs.
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3 Technical Approach to TMDL
Given the results of the initial data analysis and time and budget constraints, an approach focusing on the
magnitude of water quality standard exceedances and potential sources contributing to the stream during
the exceedances was used. This approach used a flow-duration curve analysis to determine the flow
conditions under which impairment occurs. In addition, the approach was used to identify source types,
specify the assimilative capacity of the stream, and estimate the magnitude of load reduction required to
meet the water quality standards. The potential sources determined from the load-duration curve were
inventoried and assessed for their relative contributions to allocate reductions among sources. The results
of this assessment were used to derive the allocations required by the TMDL.
This section describes the process used to specify the endpoints and calculate the existing loading and
assimilative capacity. The determination of the TMDL reductions and loads is presented in Section 4.
3.1 TMDL ENDPOINTS
The achievement of the TMDL objectives requires the instream concentrations to meet both the 20-
percent standard of 400 CFU/100 mL and the geometric mean standard of 200 CFU/100 mL. Both
standards are considered to be the endpoints for the determination of the fecal coliform TMDL for Chicod
Creek.
3.2 LOAD-DURATION CURVES FOR FECAL COLIFORM
The analysis of pollutant levels in conjunction with water quality standards and measured flow is a useful
tool for assessing critical conditions, as well as existing and target loads. The Load-Duration Curve
Method (Stiles, 2001, 2002; Cleland, 2002, 2003) was used to assess fecal coliform impairment. This
method plots flow and observed data to analyze the flow conditions under which impairment occurs and
water quality deviates from the standard.
A flow-duration curve analysis was performed to identify the flow regimes during which excursions of
the water quality criteria occur. This method determines the relative ranking of a given flow based on the
percent of time that historic flows exceed that value. Flow data have been collected by USGS at the
primary site (USGS Gage 02084160) from October 1, 1975 to the present, as summarized in Section 1.3.
Once the relative rankings were calculated for flow, monitoring data were matched by date to compare
observed water quality to the flow regime during which it was collected. This type of analysis can help
define the flow regime during which excursions occur and identify the sources of the impairment.
Excursions that occur only during low-flow events (flows that are frequently exceeded) are likely caused
by continuous or point source discharges, which are generally diluted during storm events. Excursions
that occur during high-flow events (flows that are not frequently exceeded) are generally driven by storm-
event runoff. A mixture of point and nonpoint sources may cause excursions during normal flows,
although there are no point sources in this application.
The fecal coliform assessment uses the Load-Duration Curve approach for determination of the existing
load and assimilative capacity. The analysis was performed for both the instantaneous and geometric
mean criteria to determine the most conservative measure of impairment. Figure 14 and Figure 15
present the results of the instantaneous and geometric mean load-duration analyses, respectively, based on
USGS data collected for Chicod Creek at State Road 1760 near Simpson, NC. Loads, as CFU (colony
forming units) per day, are presented by collection period relative to 1997, which was when most of the
water quality BMPs were functioning in the watershed. The average of the flow observations
corresponding to the fecal coliform sample dates was used as the flow for each geometric mean load.
Chicod Creek Coliform TMDL April 2004

30
Figure 14. Instantaneous Fecal Coliform Load-Duration Curve (400/100 mL) for Chicod Creek at
State Road 1760 Near Simpson, NC

The majority of excursions of the instantaneous criterion from both periods occurred during higher flows
(toward the left side of Figure 14). Only one excursion (observed load 4 percent over standard load)
coincided with a flow exceeded 80 percent or more of the time. Prior to 1997, 38 percent of observed
daily fecal coliform loads exceeded the instantaneous-target load based on the criterion of 400/100 mL.
After 1997, 8 percent of daily loads exceeded the target.
Comparison to the geometric mean standard requires at least five samples within a 30-day period.
Geometric means were calculated for all trailing 30-day windows (30-days prior to a given sample) with
at least five observations. A total of 19 valid geometric mean samples can be calculated, including
overlapping sets. Eight of these are from 1992, one from 1997, and ten from 2003. The geometric mean
load-duration curve is shown in Figure 15.
1E+00
1E+01
1E+02
1E+03
1E+04
1E+05
1E+06
1E+07
1E+08
1E+09
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Percent of Days Flow is Exceeded
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FC Inst Limit Curve FC Load before 1997 FC Load, 1997 to 2003
Chicod Creek Coliform TMDL April 2004

31

Figure 15. Geometric-Mean Fecal Coliform Load-Duration Curve for Chicod Creek at State Road
1760 Near Simpson, NC
One hundred percent of the geometric mean loads calculated prior to 1997 exceed the geometric mean
criterion of 200 colonies/100 mL. In order to meet the criterion, reductions of 74 to 86 percent would be
required. After 1997, no geometric mean loads exceed the criterion, although several fall close to the
criterion limit. Because no excursions of the geometric mean criterion are documented within the most
recent 5-year assessment period, direct reductions in the geometric mean are not required as a part of this
TMDL. However, reductions in instantaneous concentrations will be required, which should in turn result
in a decrease in the geometric mean concentration.
It is difficult to assign flow patterns to excursions of the geometric mean criterion with this data set
because no geometric means can be calculated during dry weather conditions. All of the geometric means
calculated prior to 1997 exceed the criterion, but they were all observed during flows exceeded less than
40 percent of the time.
The load-duration curves developed in this section provide guidance in the determination of the pollutant
sources that are likely to be the primary contributors to elevated levels of fecal coliform. Because most
excursions (of the instantaneous standard) occurred during high flows, it is likely that nonpoint sources
are the major contributor to fecal coliform loading in this watershed.
Further advances in the application of load-duration curve techniques are provided in Cleland (2003).
This approach involves separating the load duration results into different intervals characteristic of flow-
regimes. In addition, samples are marked to distinguish baseflow from surface flow conditions.
To apply this method in full, it is first necessary to distinguish surface from baseflow conditions. The
TSPROC utility (Watermark Computing, 2002) performs automated baseflow separation using a digital
filter after specification of the baseflow decay rate or recession coefficient. The recession coefficient can
be estimated by plotting flow on a given day (q1) versus flow on the preceding day (q0). Flows
1E+00
1E+01
1E+02
1E+03
1E+04
1E+05
1E+06
1E+07
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Percent of Days Flow is Exceeded
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FC GM Limit Curve FC GM Load before 1997 FC GM Load, 1997 to 2003
Chicod Creek Coliform TMDL April 2004

32
representative of true baseflow conditions should exhibit a linear relationship with slope equal to the
recession coefficient and fall just below the 1:1 line on such a plot, while flows influenced by surface
runoff will diverge non-linearly further to the right. 0 shows candidate baseflow recession data from dry
weather periods in the summers of 2001 and 2002. From the plot it is evident that flows below about 2
cfs exhibit baseflow behavior. The recession coefficient calculated through these points is 0.86, which is
lower than the typical range of 0.90 – 0.95, reflecting the significant role of artificial drainage in the
watershed.
0
1
2
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4
5
0 1 2 3 4 5
q0 (cfs)
q1 (
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Note: Symbols distinguish different dry weather recession periods.
Figure 16. Graphical Method for Determining Baseflow Recession in Chicod Creek

Due to the artificial drainage and fast recession of flows in Chicod Creek, hydrograph peaks are brief, and
few observations coincide with conditions that are dominated by surface runoff. Rather than use the
criterion of surface flows (SF) greater than 50 percent recommended by Cleland (2003) to distinguish
surface versus non-surface washoff loading, a criterion of 10 percent SF was adopted. Because surface
washoff concentrations are typically an order of magnitude or more greater than groundwater
concentrations, this low cutoff should still provide useful information on the dominance of observed
concentrations by surface loading pathways.
Figure 17 provides a load-duration characterization of the post-1997 instantaneous coliform data, using
the methods recommended by Cleland (2003). Observations above the criterion line occur primarily in
the high flow and moist condition sections of the plot, with the area of greatest concern denoted by the red
circle. A number of the observations at lower flows that fall on or near the criterion line are also
associated with surface washoff events (SF > 10 percent). This further suggests that remaining
bacteriological problems in Chicod Creek are mostly associated with surface washoff events. Three
Chicod Creek Coliform TMDL April 2004

33
observations that fall just above the criterion line are associated with a lower fraction of surface runoff
and could reflect a non-precipitation driven source, such as a lagoon spill or improper spray application.
Notes: SF = Surface runoff fraction. Circle indicates conditions at which the criterion is most likely to be
exceeded.
Figure 17. Load-Duration Characterization of Post-1997 Instantaneous Fecal Coliform
Concentration Data in Chicod Creek
The nine observations that fall above the criterion line occur throughout the year (two in January, two in
April, one in July, three in September, and one in October). Therefore, there does not appear to be a
seasonal pattern to criterion excursions.
3.3 DETERMINATION OF EXISTING FECAL COLIFORM LOAD AND
ASSIMILATIVE CAPACITY
NC DWQ’s 305(b) assessment methodology relies on data collected during the previous seven years.
Significant work on installing BMPs in the watershed was completed in 1997, leading to a change in
observed fecal coliform concentrations. Therefore, only the data since 1997 are relevant to estimating
load reductions.
In the recent data, there are no documented excursions of the geometric mean criterion, and no reductions
are required to achieve water quality standards. However, there are a limited number of excursions of the
instantaneous criterion (Figure 14) indicating the need for an incremental amount of further reductions.
1E+00
1E+01
1E+02
1E+03
1E+04
1E+05
1E+06
1E+07
1E+08
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Mid-range
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Dry Conditions Low
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Chicod Creek Coliform TMDL April 2004

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3.3.1 Instantaneous (20 Percent) Criterion
The load-duration curve for instantaneous fecal coliform concentrations presented in Figure 17 for post-
1997 data is used as the basis for estimating the TMDL.
The water quality criterion for instantaneous fecal coliform concentrations allows up to 20 percent of
samples within a 30-day period to exceed the target. The regulations clearly recognize that some
excursions of the 200 CFU/100 mL target are expected to occur during washoff events. This frequency
component needs to be taken into account when determining the assimilative capacity.
In some past applications, NC DWQ has used an ad hoc approach to the analysis of the difference
between existing load and assimilative capacity. This approach involved fitting a regression line through
those observations that were above the criterion limit curve and associated with the 10th through 95th
percentile of the flow distribution. Based on guidance from EPA Region 4 and NCDENR, data collected
during extreme drought conditions ( > 95th percentile) and floods (< 10th percentile) were excluded from
the reduction analysis. Then, the natural log of the coliform loads exceeding the criterion was regressed
on the natural log of the flow interval, and this regression curve was used to estimate the existing loading
at every 5th percentile flow recurrence. The existing loading was then compared to the allowable loading
(with a margin of safety), and the difference used to establish needed reductions. Because the regression
line goes through the center of the distribution of points above the criterion limit curve, it allows a
fraction of the observations to exceed the criterion; however, this fraction is not explicitly tied to the 20
percent frequency of allowable excursions specified in the criterion.
For this TMDL, a more rigorous quantitative approach is used. The essence of this approach is follows:
• Establish a regression model to predict existing load as a function of flow percentage.
• Develop a prediction confidence interval on the regression line, with the confidence interval set at
a level that reflects the allowed 20 percent frequency of excursions.
• Calculate a reduced criterion limit curve at 90 percent of the criterion concentration, thus
incorporating a 10 percent margin of safety.
• Evaluate needed reductions based on the maximum difference between the prediction confidence
interval and the reduced criterion limit curve, incorporating a margin of safety, between the 10th
and 95th percentile flows.
The confidence interval is based on the point prediction interval about the regression line. That is, it
reflects the range of expected values for individual observations at a given flow frequency, and
incorporates both the uncertainty in the regression line and the natural variability of individual points
about the regression line. In theory, the upper 60th percentile confidence interval is just sufficient to meet
the criterion (20 percent of observations are expected to fall in both the high and low tails of the
distribution). However, the TMDL also requires a Margin of Safety. This is achieved by evaluating
needed reductions in relation to the criterion limit curve reduced by 10 percent (that is, evaluated at 360
rather than 400 CFU/100 mL). The Margin of Safety is thus assigned explicitly through a 10 percent
reduction in the criterion.
Complete details of the methodology for establishing the regression line and prediction confidence
interval are presented in Appendix B. A comparison of regression methods showed that the best fit was
obtained with a log-linear regression (adjusted R2 = 70 percent), yielding a model of the following form:
( )FractionFlowdCFUinLoadColiformLn⋅−=123.757.13/106 ,
where flow fraction is the percentile of the flow expressed as a fraction.
Application of the regression equation and its upper 60th percentile prediction interval (see Appendix B) is
shown in Figure 18. As expected, the majority, but not all of the observed data fall below the upper
Chicod Creek Coliform TMDL April 2004

35
prediction interval. For instance, in the 10-40 percent flow frequency range, 3 points or 10 percent of the
observations fall above the line, consistent with the water quality criterion that allows up to 20 percent of
observations within a 30-day period to exceed the target concentration.

1E+00
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Note: Reduced limit curve represents allowed load at 90 percent of the water quality criterion of 400 CFU/100 mL.
Figure 18. Regression Analysis of the Instantaneous Fecal Coliform Load-Duration Curve,
Chicod Creek Data for 1997-2003

The upper 60 %le Prediction Interval lies above the reduced instantaneous Limit Curve in two areas of the
graph – between flow frequencies of 5 and 32 percent, and for flow frequencies above 95 percent. These
are the two areas in which reductions may be needed. The amount of these reductions, based on the
maximum difference between the 90 percent Prediction Interval and the Limit Curve for each of the flow
intervals as defined by Cleland (2003), but omitting flows with greater than 95 percent is summarized in
Table 7. Reductions of about 16 percent (including the Margin of Safety incorporated through use of the
reduced limit curve) are required for the moist condition regime. High flows (0-10 percent frequency of
excursion) are usually not addressed in North Carolina fecal coliform TMDLs; but do not require any
greater reduction than is needed for the “moist” conditions and are included in the table for information
purposes. These reductions are consistent with the existing data, as most reported excursions of the water
quality criterion (since 1997) have occurred in these flow ranges. The regression model also predicts a
potential need for a small (< 1 percent) load reduction in the low flow range (90-95 percent flow
frequency). However, the linear nature of the model fit may be suspect in this tail range.

Chicod Creek Coliform TMDL April 2004

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Table 7. Fecal Coliform Target Load and Reduction Requirements Calculated using the Load-
Duration Curve Approach
Flow Range
Critical
Percentile Flow (cfs)
Target Load
(CFU/d)
60le Prediction
Limit (CFU/d)
Reduction
Required
0-10%
(High Flows) 9.38% 134 1.18 x 1012 1.33 x 1012 11.0%
10-40% (Moist
Conditions) 12.73% 100 8.81 x 1011 1.05 x 1012 15.9%
40-60% (Mid-
Range Flows) 40.40% 22 1.94 x 1011 1.53 x 1011 NA
60-90% (Dry
Conditions) 89.24% 1 8.81 x 109 5.56 x 109 NA
90-95%
(Low Flows) 94.83% 0.43 3.79 x 109 3.82 x 109 0.9%
Notes:
Critical Percentiles are the values within the flow range at which the ratio of the 6th percentile prediction limit to target
load is greatest. These are evaluated from the set of flows on all days on which fecal coliform data were collected,
excluding days with zero flow.
Flow column gives the flow corresponding to the critical percentile.
Target Load is the value of 90 percent of the instantaneous criterion limit curve at the specified flow and percentile,
thus incorporating a 10 percent Margin of Safety.
60le Prediction Limit is the upper prediction interval about the regression line at the 60 percent confidence level.
Reduction Required is calculated as (60le Prediction Limit – Target Load)/(60le Prediction Limit)
3.3.2 Geometric Mean Criterion
As noted above, no reductions are required in the geometric mean concentration to achieve water quality
standards, based on monitoring from 1997 to present. However, reductions in the geometric mean can
reasonably be expected to occur as a result of required reductions in the instantaneous concentration.
The 5-day geometric mean is calculated as
515
1



=∏
=i
ixGM ,
where the xi are the individual observations. If each of the individual xi are reduced by a factor β , then the
new geometric mean, GMnew, would also be reduced:
( )GMxxGM
i
i
i
inew ⋅=


⋅=


=∏∏
==
βββ
515
1
515
515
1
.
The actual reduction in the geometric mean depends on whether reductions apply to all or some of the
individual observations. For instance, if only the highest concentration in a set of five is reduced (for
instance, because implementation measures address large event runoff only), then the change would be
equivalent to β 1/5.
Chicod Creek Coliform TMDL April 2004

37
The Chicod Creek coliform TMDL proposes a reduction of 16 percent in instantaneous concentrations,
specifically targeted toward flow with a recurrence interval of 40 percent or less. If the reduction applied
to all fecal coliform concentrations, then the geometric mean would also be expected to decline, on
average, by 16 percent (to 84 percent of the existing value). If, however, the reduction applies only to the
upper 40 percent of the flow distribution, the geometric mean would decline by 6.7 percent (to 93.3
percent of the existing geometric mean). While no reduction is required in the observed geometric mean
concentration, this expected reduction will provide a further margin of safety relative to existing
conditions.
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4 TMDL Development
Sections 1 through 3 described the processes and rationale required to identify the endpoints, critical
conditions, potential sources, and target loadings for each pollutant. These efforts formed the basis for
the TMDL process. This section describes the key components required by the TMDL guidelines and
synthesizes the project efforts to set the final TMDL allocations.
4.1 TMDL DEFINITION
A TMDL is the total amount of a pollutant that can be assimilated by the receiving water while still
achieving water quality criteria (in this case a target for warm water aquatic habitat). TMDLs can be
expressed in terms of mass per time or by other appropriate measures such as concentration. TMDLs are
comprised of the sum of individual wasteload allocations (WLAs) for point sources, load allocations
(LAs) for nonpoint sources, and natural background levels. In addition, the TMDL must include a margin
of safety (MOS), either implicitly or explicitly, that accounts for the uncertainty in the relationship
between pollutant loads and the quality of the receiving waterbody. Conceptually, this definition is
denoted by the equation:

TMDL = Σ WLAs + Σ LAs + MOS

The TMDL is equivalent to the assimilative capacity or loading capacity of the waterbody, which varies
according to flow, as shown in Section 3.3.
4.2 TMDL ENDPOINTS
TMDL endpoints represent the instream water quality targets used in quantifying TMDLs and their
individual components. As discussed in Section 3, there are two endpoints that can be used to determine
the fecal coliform TMDL, as specified in the North Carolina water quality standards. Both the 20 percent
or “instantaneous” limit of 400 CFU/100 mL and the geometric mean limit of 200 CFU/100 mL were
considered. However, based on analysis of monitoring data since 1997, the existing documented
impairment is based only on excursions of the instantaneous criterion. Therefore, the instantaneous
criterion serves as the endpoint for this TMDL. However, as noted in Section 3.3.2, implementing
reductions to meet the instantaneous criterion will also result in a reduction in geometric mean
concentrations.
4.3 CRITICAL CONDITIONS
The Load-Duration-Curve approach addresses the load reductions required during all flow regimes.
Unlike a steady state analysis, it does not depend on the identification of critical conditions to determine
allocations. The load-duration analysis in Section 3.2, however, indicates that excursions of the criterion
are primarily associated with higher flows with significant surface runoff. Therefore, implementation of
the TMDL should focus on storm washoff events as a critical condition.
As shown in Table 7 in Section 3.3.1, the maximum reduction in existing loads is required at a flow of
100 cfs. At a flow of 100 cfs, the assimilative capacity (the maximum load that just meets the
instantaneous limit of 400 CFU/100 mL) is 4.79 x 1011 CFU/d.
Chicod Creek Coliform TMDL April 2004

40
4.4 SEASONAL VARIATION
The load-duration approach automatically accounts for seasonal variations in flows. No seasonal pattern
was detected in excursions of the criterion (Section 3.2), which occur throughout the year. Thus, no
additional seasonal component is needed in the TMDL, and the reductions should be sought over all
seasons.
4.5 MARGIN OF SAFETY
There are two methods for incorporating a MOS in the analysis: 1) by implicitly incorporating the MOS
using conservative model assumptions to develop allocations; or 2) by explicitly specifying a portion of
the TMDLs as the MOS and using the remainder for allocations. For the purposes of this TMDL
analysis, an explicit 10 percent margin of safety was specified by calculating reductions relative to the
load limit curve estimated at 90 percent of the instantaneous criterion.
At the critical flow condition of 100 cfs, the assimilative capacity is 9.79 x 1011 CFU/d, while the target
load is 8.81 x 1011 CFU/d – a 10 percent reduction. Therefore, the explicit MOS is 9.79 x 1010 CFU/d at
the critical flow of 100 cfs.
An additional implicit margin of safety is provided because the proposed reductions are also likely to
result in achieving standards during those high flow conditions (flow recurrence less than 10 percent), as
they are not typically addressed in North Carolina coliform TMDLs.
4.6 WASTELOAD ALLOCATIONS
There are no currently permitted point sources in the watershed. The entire county of Pitt is, however,
designated under the NPDES Phase II Stormwater Program and will be subject to a general permit for
Municipal Separate Storm Sewers (MS4s). The MS4 designation, pursuant to 40 CFR § 122.26(b)(8),
means a conveyance or system of conveyances (including roads with drainage systems, municipal streets,
catch basins, curbs, gutters, ditches, manmade channels, or storm drains) that are owned by a public entity
and designed or used for collecting or conveying stormwater. The proposed permanent rule language for
15A NCAC 2H .0126 (1)(k) clarifies that “The term does not include separate storm sewer systems in
very discrete areas, such as individual buildings.” Within the sparsely populated Chicod Creek
watershed, the MS4 designation is assumed to apply to the land area in the watershed that is within the
corporate limits of Grimesland and Simpson, or which falls within the
commercial/industrial/transportation land use category and is outside Grimesland or Simpson but within
Pitt County.
The Town of Grimesland had a population of 440 at the time of the 2000 Census, and the Village of
Simpson a population of 464 – both within 10 percent of their 1990 populations (Pitt Co., 2002). Total
land area within both the watershed and the corporate boundaries of these two entities is 269.9 acres.
Additional land in the commercial/industrial/transportation category within Pitt County but outside of
these two entities amounts to 47.7 ac, for a total MS4 area of 317.6 ac (0.87 percent of the watershed).
A wasteload allocation is assigned to these land areas consistent with the NPDES Phase II Stormwater
program. Because the area represents a small fraction of the total watershed area and potential fecal
coliform loading, the assignment of the wasteload allocation is made on an areal basis by the same
methods used to develop load allocations in Section 4.7. The total MS4 wasteload allocation is 1.35 · 1010
CFU/d at 100 cfs critical flow (refer to Table 8).
Future urban/suburban development within the watershed may also fall under the MS4 NPDES permit.
Such cases, however, will represent a shift from a load allocation to a wasteload allocation, rather than a
change in the total allocations.
Chicod Creek Coliform TMDL April 2004

41
4.7 LOAD ALLOCATIONS
Load allocations account for the portion of the TMDL assigned to nonpoint sources. Federal regulations
at 40 CFR § 130.2(g) state that “Load allocations are best estimates of the loading, which may range from
reasonably accurate estimates to gross allotments, depending on the availability of data and appropriate
techniques for predicting the loading. Wherever possible, natural and nonpoint source loads should be
distinguished.”
The total of the wasteload allocation and load allocations for Chicod Creek is equivalent to the target load
at critical conditions of 100 cfs flow, or 8.81 x 1011 CFU/d (Table 7). The wasteload allocation and load
allocations are estimated by similar methods and combined into one table below.
Quantitative estimates of coliform loading rates from individual land uses have not been established for
the Chicod Creek watershed. However, “gross allotment” load allocations plus a wasteload allocation for
the MS4 area may be estimated for individual land uses, based on the following assumptions:
• Natural background loading rates are applied equally to all land areas and are assigned based
on the percentage of land in the watershed in each land use.
• The natural background loading may be estimated from the ratio of the long-term geometric
mean loading observed at the reference sites of Durham Creek and Van Swamp to the 1997-
2002 long-term geometric mean loading observed in Chicod Creek (where the long-term
geometric mean refers to the geometric mean of all individual observations), or 19/70.
• The remainder of the load allocation is assigned to those land uses that are likely to contribute
fecal coliform load at rates above natural background, specifically cropland, pasture,
residential land, and the fraction of forest that has been cut within the last two years,
estimated at 1360 acres (on average), or 6.7 percent of the total forest area.
• The portion of the load allocation in excess of natural background is allocated to individual
land uses according to their proportion of the total area of land expected to generate load in
excess of natural background.
Using these assumptions, the wasteload allocation and load allocations may be partitioned as summarized
in Table 8.
Chicod Creek Coliform TMDL April 2004

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Table 8. Fecal Coliform Bacteria Wasteload Allocation and Load Allocations for Chicod Creek
Allocations (CFU/d at 100 cfs flow)
Source
Area
Percent of
Total Land
Area
the Non-background
Coliform Load
Natural
Background
Additional
Allocation Total
Wasteload Allocation (WLA)
MS4 area 0.9% 1.85% 2.47 x 109 1.10 x 1010 1.35 x 1010
Load Allocations (LAs)
Agriculture 41.4% 88.36% 1.18 x 1011 5.27 x 1011 6.45 x 1011
Forest 55.6% 7.94% 1.58 x 1011 4.73 x 1010 2.06 x 1011
Residential 0.8% 1.75% 2.34 x 109 1.04 x 1010 1.28 x 1010
Other 1.3% 0.00% 3.74 x 109 0 3.74 x 109
Total LAs 99.1% 98.15% 2.83 x 1011 5.85 x 1011 8.67 x 1011
Grand Total 100.0% 100.0% 2.85 x 1011 5.96 x 1011 8.81 x 1011

Note: In this table, “Other” includes bare rock, sand or clay, transitional areas, emergent wetlands, and water outside
the MS4 area.
4.8 TMDL SUMMARY
The load-duration curves for the existing and target conditions were evaluated to determine the reductions
needed to meet the TMDL endpoints. To achieve the specified TMDL targets, a reduction of about 16
percent in the wet-weather loading of fecal coliform bacteria will be required, and is specified in the Load
Allocations for nonpoint sources and the Wasteload Allocation for MS4 stormwater runoff. The
components of the TMDL are summarized in Table 9.
Table 9. TMDL Summary for Fecal Coliform in Chicod Creek
Criterion Fecal coliform concentration shall not exceed 400
CFU/100 mL in more than 20 percent of samples in a 30-
day period
Criterion Load (TMDL; at 100 cfs) 9.79 x 1011 CFU/d
Existing Load 1.05 x 1012 CFU/d
Wasteload Allocation 1.35 x 1010 CFU/d0
Load Allocations 8.67 x 1011 CFU/d
Margin of Safety 9.79 x 1010 CFU/d
Reduction Required 15.9 %

Note: All loading rates are calculated at the critical flow of 100 cfs.

Chicod Creek Coliform TMDL April 2004

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5 Report Summary
This report presents the development of Total Maximum Daily Loads (TMDLs) for fecal coliform
impairment of Chicod Creek, a tributary to the Tar River, in Pitt and Beaufort Counties, North Carolina.
This waterbody was placed on the North Carolina 2002 list of impaired waters (the 303(d) list) for fecal
coliform bacteria. Available water quality data were reviewed to determine the frequency of excursions.
The load-duration curve method was applied to determine the critical periods and the sources that lead to
criteria excursions, along with the reductions needed to achieve water quality standards.
While the watershed has many swine and poultry operations, extensive efforts to improve animal waste
management appear to have largely mitigated confined animal operations as a source of bacterial loading.
Since the mid-1990s, fecal coliform loading has been greatly reduced; however, the remaining loading is
sufficient to result in an unacceptably high rate of excursions of the 20-percent standard of 400 CFU/100
mL. There are no point sources in the watershed. Continued excess loading appears to be due primarily
to stormwater washoff from agriculture lands and, potentially, clearcut forest lands.
The TMDL analysis, which uses a load-duration curve approach, indicates that a reduction of about 16
percent in the wet-weather loading of fecal coliform bacteria to Chicod Creek is needed to achieve water
quality standards. The majority of these reductions can be achieved through additional efforts to install
BMPs that limit surface transport of pollutants from agricultural and forest lands, such as the use of
vegetative filter strips and enhanced riparian buffers. In addition, inspection and enforcement activities
should be continued to ensure that confined animal feeding operations remain in compliance with their
waste management plans. Reductions in loading can also likely be obtained by better management of
stormwater runoff from residential and developed land; however, these sources appear to constitute only a
small portion of the total fecal coliform loading to Chicod Creek.
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6 TMDL Implementation Plan
The TMDL analysis was performed using the best data available to specify the fecal coliform 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 land owners and agencies will be needed in order to develop an implementation
plan.
In general, reductions in fecal coliform loads should be sought through identification and installation of
additional agricultural and post-cutting silvicultural BMPs to reduce loads during runoff events.
Implementation should also ensure proper operation of animal waste sprayfields in accordance with waste
management plans. Additional information on potential next steps is included in Section 8.
A small portion of the total fecal coliform load is attributed to sources that will be regulated under the
NPDES Phase II stormwater permit for Pitt County. Some reduction in this loading component was
likely already achieved when Grimesland connected to the Greenville sewer system. Additional
opportunities to reduce the MS4 load component are anticipated as Pitt County develops its Phase II
stormwater plan.
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7 Stream Monitoring
Monitoring will continue on a monthly interval at the ambient monitoring site on Chicod Creek. The
continued monitoring of fecal coliform will allow for the evaluation of progress towards the goal of
achieving water quality standards and intended best uses.
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8 Future Efforts
Bacteriological water quality in Chicod Creek appears to have improved significantly over the last
decade. This improvement appears to have been the result of improved adoption of agricultural BMPs,
particularly those related to hog waste sprayfield applications. The TMDL estimates, however, that a
further incremental reduction in fecal coliform loading is needed.
The most important current sources of fecal coliform loading appear to be stormwater runoff from
agricultural and, perhaps, cut-over silvicultural land. Addressing these sources will require further
voluntary adoption of BMPs, facilitated by existing cost-share programs and educational efforts.
Improper operation of sprayfields may also be an occasional source of coliform excursions. If present,
such sources are in violation of the no-discharge general permit and should be addressed through
enforcement.
As described in Section 1.2.4.2 extensive efforts were conducted in the early 1990s to implement BMPs
at targeted swine operations in order to improve the operation and performance of lagoon-spray irrigation
waste systems. Much room for improvement existed at swine operations during that time period because
such facilities were not subject to regular inspections or regulatory requirements. After the N.C. General
Assembly enacted legislation in 1997 requiring regular inspections of swine operations and development
and implementation of waste utilization plans, most of the BMPs applied to targeted facilities in previous
years were subsequently applied at most, if not all, facilities through the implementation of the waste
plans. As a result, little opportunity now exists for achieving further reductions in fecal coliform loading
through the application of structural BMPs at swine operations.
As discussed in Section 1.2.4.1, after the enactment of legislation regulating concentrated animal feeding
operations (CAFOs), the most common type of recorded illicit “discharge” at swine operations in the
Chicod Creek watershed resulted from irrigating on saturated spray fields. Occurrences of this nature are
most likely prevented or reduced through increased enforcement efforts. At the time of Tetra Tech’s
review of the CAFO permitting and enforcement files, only three NCDWQ staff members were assigned
to inspecting operations within the Washington Regional Office territory for NCDWQ. That territory
consists of 21 northeastern counties, which contain over 500 CAFOs that are almost all swine operations.
Considering the administrative demands and travel time associated with carrying out such an effort, the
current staffing level may not be sufficient to ensure the desired frequency of inspections of these
facilities. An increase in the level of program resources devoted to inspection and enforcement may
result in a reduction in the occurrence of episodic illicit discharges from spray irrigation systems at swine
operations. Review of the permitting and enforcement files also indicated that some of the enforcement
cases related to illicit discharges originated with citizen complaints. Increased enforcement efforts to
address these problems could be augmented by efforts to better educate citizens in the area on how to
recognize and report illicit discharges. Establishment and promotion of a dedicated phone “hotline” for
such citizen reports, such as the Sediment Hotline operated by the N.C. Division of Soil and Water
Conservation, might also increase the effectiveness of enforcement efforts.
The future effort offering the largest opportunity for reduction in fecal coliform loads is that of
application of BMPs to row crop agricultural lands. As discussed in Section 0, estimates are that only
100 – 150 acres, or approximately one percent of the row cropland within the Chicod Creek watershed
use grassed field borders and drainage swales. A concerted effort to increase the application of such
BMPs could result in significant reductions in coliform loads stemming from wildlife attracted to row
crops as a food source. BMPs of this type would also help achieve reductions in nutrient export to
Pamlico Sound.
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9 Public Participation
A draft of the TMDL will be publicly noticed through various means, including notification in the local
newspapers. DWQ will electronically distribute the draft TMDL and public comment information to
known interested parties. The TMDL will also be available from the Division of Water Quality’s website
at http://h2o.enr.state.nc.us/tmdl/ during the comment period. A public meeting will be held in mid-2004
to present the TMDL and answer questions. The public comment period will last for a minimum of 30-
days.
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10 Further Information
Further information concerning North Carolina’s TMDL program can be found on the Internet at the
Division of Water Quality website:
http://h2o.enr.state.nc.us/tmdl/
Technical questions regarding this TMDL should be directed to the following members of the DWQ
Modeling/TMDL Unit:
Brian Jacobson, Modeler
e-mail: [e-mail]
Michelle Woolfolk, Supervisor
e-mail: [e-mail]
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11 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.
Cleland, B.R. 2003. TMDL development from the “bottom up” – Part III: Duration curves and wet-
weather assessments. America’s Clean Water Foundation, Washington, DC. Available online at
http://www.tmdls.com/tipstools/docs/TMDLsCleland.pdf (accessed 2/11/04).
Ensign, S.H. and M.A. Mallin. 2001. Stream water quality changes following timber harvest in a coastal
plain swamp forest, Wat. Res. Vol. 35, No. 14, pp. 3381-3390.
Etheridge, Tim. 2004. Personal Communication by phone interview, January 10, 2004 and February 2,
2004. District Conservationist, USDA – Natural Resources Conservation Service, Pitt County, N.C.
FACA. 1998. Federal Advisory Committee (FACA). Draft final TMDL Federal Advisory Committee
Report.
Gilbert, R.O. 1987. Statistical Methods for Environmental Pollution Monitoring. Van Nostrand
Reinhold, New York.
Mallin, M.A., J.M. Burkholder, M.R. McIver, G.C. Shank, H.B. Glasgow, Jr., B.W. Touchette, J.
Springer. 1997. Comparative effects of poultry and swine waste lagoon spills on the quality of receiving
streamwaters, Journal of Environmental Quality 26:1622-1631.
Mallin, M.A., S.H. Ensign, M.R. McIver, G.C. Shank, P.K. Fowler. 2001. Demographic, landscape, and
meteorological factors controlling the microbial pollution of coastal waters, Hydrobiologia 460: 185-193.
Mason, R.R., Jr. 1988. Ground-water and surface-water conditions in the Chicod Creek Basin, North
Carolina, before, during, and after channel modifications. Proceedings of the AWRA Symposium on
Coastal Water Resources, Wilmington, NC, May 22-25, 1988, American Water Resources Association, p.
419-427.
Mason, R.R, Jr., C.E. Simmons, S.A. Watkins. 1990. Effects of Channel Modifications on the Hydrology
of Chicod Creek Basin, North Carolina, 1975-87. U.S. Geological Survey Water-Resources Investigations
Report 90-4031, 83 p.
NCCGIA. 2002. BasinPro GIS data system Version 2.1. N.C. Center for Geographic Information and
Analysis. Raleigh, N.C. 4 CD set.
NCDENR. 1999. Final Report on BMP Implementation in the Tar-Pamlico River Basin: Results of a
Cooperative Agreement Funded Through Section 104 (b) (3) of the Clean Water Act. Prepared by J. Todd
Kennedy, Division of Soil and Water Conservation, December 1999.
NCDENR. 2003. North Carolina Water Quality Assessment and Impaired Waters List (2002 Integrated
305(b) and 303(d) Report) Final, February 2003. Prepared by the North Carolina Department of
Environment and Natural Resources, Division of Water Quality.
Pitt Co. 2002. Pitt County Comprehensive Land Use Plan, 2002. Adopted April 15, 2002. Pitt County,
North Carolina.
Raval, Chardul. 2004. Personal communication via phone on January 21, 2004 concerning managed
forests in Pitt County, North Carolina.
Stiles, T.C. 2002. Incorporating hydrology in determining TMDL endpoints and allocations.
Proceedings from the WEF National TMDL Science and Policy 2002 Conference, Phoenix, AZ.
Chicod Creek Coliform TMDL April 2004

56
Stiles, T.C. 2001. A simple method to define bacteria TMDLs in Kansas. ASIWPCA/ACWR/WEF
TMDL Science Issues Confrence: On-site Program, St. Louis, MO, pp. 375-378.
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. Federal Register, 65:43586-43670.
USEPA. 1991. Guidance for Water Quality-Based Decisions: The TMDL Process. U. S. Environmental
Protection Agency, Assessment and Watershed Protection Division, Washington, DC.
USEPA. 1986. Bacteriological Ambient Water Quality Criteria for Marine and Fresh Recreational
Waters. EPA 440/5-84-002. U.S. Environmental Protection Agency, Office of Research and
Development, Cincinnati, OH.
Watermark Computing. 2002. PEST Surface Water Utilities. Watermark Numerical Computing,
Brisbane, Australia.
Watkins, S.A. and C.E. Simmons. 1984. Hydrologic Conditions in the Chicod Creek Basin, North
Carolina, Before and During Channel Modification, 1975-81. Water-Resources Investigations Report 84-
4025. U.S. Geological Survey, Raleigh, NC.
Woodside, Michael D. and Simerl, Benjamin R., 1995, Land use and nutrient concentrations and yields in
selected streams in the Albemarle-Pamlico Drainage Basin, North Carolina and Virginia. Open-File
Report 95-457. U.S. Geological Survey, Raleigh, NC.

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12 Appendices

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Chicod Creek Coliform TMDL April 2004
A
A-1
Appendix A. Fecal Coliform Data for Chicod Creek
Fecal coliform data were collected at two sites in Chicod Creek. The primary site used for TMDL
allocations is coincident with USGS Station 02084160 at State Road 1760 near Simpson, NC and is
equivalent to NC DWQ site O6450000. This station is referred to as the “primary site” because it
represents the majority of data collected in the watershed and is near the outlet of the listed reach. USGS
flow gaging is also available at this station.
Fecal coliform data were also collected by NC DWQ for a brief time as part of a special study from
Chicod Creek at Boyd’s Crossroads (NCDWQ Site ChC1). This site is referred to as the “upstream site”
because it is upstream of the primary site as well as most of the swine facilities in the watershed. No flow
gage is present at this site.
Table A-1 lists fecal coliform and flow data at the primary site. Table A-2 lists fecal coliform data
collected at the upstream site. Table A-3 lists the valid 30-day geometric mean fecal coliform
concentrations and representative flows at the primary site.
Table A-1. Fecal Coliform and Flow Data at the Primary Site in Chicod Creek
(USGS 02084160, NC DWQ O6450000)
Date Flow (cfs) FC Observation (#/100 mL)
11/8/77 1020 160
11/10/77 268 120
4/27/78 1480 8600
11/29/78 5.1 660
11/5/79 3.5 160
1/2/80 14 120
11/17/80 3.7 72
1/12/81 13 150
1/13/81 12 150
5/12/81 70 700
6/7/81 854 4200
6/7/81 854 4900
8/5/81 0.16 96
8/31/81 7.3 180
10/13/81 0.03 20
12/1/81 0.36 196
1/4/82 227 3400
1/5/82 215 410
1/18/82 20 180
2/24/82 45 380
4/20/82 4.8 120
8/12/82 456 10
8/23/82 4.9 390
12/21/82 87 120
2/22/83 78 200
3/1/83 394 6100
7/5/83 85 30000
8/15/83 0.14 84
9/19/83 2.6 1200
11/14/83 1 84
1/3/84 24 240
1/11/84 353 31000
3/26/84 345 720
5/8/84 109 1500
5/21/84 4.1 88
Chicod Creek Coliform TMDL April 2004
A
A-2
Date Flow (cfs) FC Observation (#/100 mL)
9/13/84 927 2100
9/14/84 1980 3200
11/14/84 2.5 40
12/17/84 5.7 32
2/6/85 416 1200
3/26/85 29 68
4/12/85 4.6 100
5/29/85 0 160
7/15/85 3.8 110
9/4/85 2.2 96
10/23/85 28 560
12/18/85 44 180
1/29/86 55 390
5/8/86 0.94 96
12/17/86 4 180
1/23/87 942 3320
6/8/92 2.3 80
6/10/92 150 5400
6/12/92 50 5400
6/24/92 24 490
7/2/92 6.5 960
7/8/92 7.8 350
7/17/92 0.36 210
7/20/92 154 9000
7/27/92 5.9 330
7/28/92 21 22000
7/29/92 12 1570
8/3/92 12 5800
8/3/92 12 3770
8/5/92 7.8 190
8/7/92 4.7 160
8/10/92 4.5 3400
8/12/92 9.9 210
8/14/92 355 5600
8/17/92 1320 210
8/19/92 572 230
8/21/92 243 2160
8/26/92 35 1400
9/2/92 7.6 100
3/30/93 116 317
4/15/93 52 310
5/18/93 8.4 527
6/15/93 91 250
7/21/93 3.9 240
8/11/93 0.39 105
10/19/93 6.9 207
11/17/93 8.5 38
1/20/94 100 126
2/16/94 42 108
3/25/94 29 113
4/13/94 8.2 628
5/17/94 0.5 200
9/20/94 0.28 24
10/20/94 9.1 430
12/14/94 101 31
1/8/97 54 315
2/17/97 146 10
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Date Flow (cfs) FC Observation (#/100 mL)
2/19/97 78 10
3/5/97 30 54
3/11/97 22 27
3/19/97 67 240
4/2/97 24 27
4/10/97 12 36
4/16/97 12 10
5/1/97 84 270
5/14/97 20 63
5/15/97 20 260
5/29/97 9.4 64
6/10/97 8.1 240
6/11/97 7.4 45
6/25/97 3.9 27
7/7/97 6.3 130
7/17/97 4.5 630
7/21/97 17 370
8/4/97 3 100
8/18/97 1.6 45
8/19/97 3.6 380
9/2/97 5 10
9/16/97 6.5 10
9/29/97 6 170
10/6/97 0.1 230
10/27/97 0.43 420
11/17/97 3.8 54
11/24/97 2.3 36
12/8/97 10 64
12/9/97 12 36
1/5/98 9.5 20
1/7/98 9.9 55
2/9/98 119 18
2/12/98 145 300
2/26/98 23 10
3/5/98 5.7 205
4/2/98 79 1799
5/12/98 17 109
6/3/98 4 27
7/7/98 0.31 190
8/3/98 0 10
8/31/98 112 120
9/3/98 10 55
10/6/98 12 73
11/2/98 7.7 18
1/6/99 31 18
2/1/99 33 118
3/3/99 31 45
4/6/99 15 9
5/4/99 2.6 9
6/15/99 9.7 155
7/7/99 1.7 100
8/5/99 3.1 227
9/9/99 126 109
9/27/99 350 30
10/4/99 23 33
10/12/99 10 18
11/15/99 8.4 9
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Date Flow (cfs) FC Observation (#/100 mL)
1/11/00 142 672
2/3/00 113 64
3/7/00 1.1 27
4/4/00 4.2 27
5/2/00 134 36
6/8/00 2.7 73
7/10/00 1.2 63
8/22/00 1.2 182
9/19/00 74 3500
10/3/00 2.4 18
11/2/00 1 36
12/21/00 19 45
1/9/01 9.5 9
2/7/01 18 18
4/11/01 7.5 32
5/17/01 2 49
8/20/01 19 137
9/19/01 4.9 41
10/17/01 2.8 47
11/8/01 1.6 19
12/12/01 5.4 210
1/8/02 45 600
2/11/02 53 125
3/6/02 98 54
4/4/02 244 1200
5/9/02 3.1 20
6/25/02 0.48 30
7/9/02 0.97 34
8/8/02 0 50
9/19/02 0 210
10/15/02 8.3 108
11/21/02 30 88
12/12/02 36 39
1/7/03 8.9 27
1/16/03 5.3 30
1/28/03 3.7 23
1/30/03 4.3 73
2/6/03 4.8 100
2/12/03 14 100
2/13/03 9.4 25
3/10/03 83 36
4/14/03 77 132
5/13/03 4.8 21
6/23/03 4.3 280
7/14/03 13 124
8/19/03 74 220
9/3/03 7.4 96
9/9/03 26 230
9/11/03 21 460
9/23/03 88 440
9/25/03 57 70
9/30/03 215 120
10/7/03 17 130
10/9/03 19 160
10/14/03 29 150
10/22/03 21 100
10/28/03 25 340
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Table A-2. Fecal Coliform Data at the Upstream Site in Chicod Creek (NCDWQ Site ChC1)
Date FC Observation (#/100 mL)
9/3/03 170
9/9/03 270
9/11/03 130
9/23/03 520
9/25/03 83
9/30/03 73
10/7/03 51
10/9/03 76
10/14/03 210
10/23/03 140
10/28/03 540

Table A-3. 30-day Fecal Coliform Geometric Mean Concentrations and Representative Flows at
the Primary Site in Chicod Creek (USGS 02084160, NC DWQ O6450000)
End Date Representative Flow (cfs) Fecal Coliform Geometric Mean (#/100 mL)
7/8/92 40.1 853
7/20/92 38.5 792
7/29/92 29.7 1327
8/7/92 23.8 1175
8/14/92 49.9 1401
8/19/92 191.6 1219
8/26/92 186.8 1112
9/2/92 215.3 763
3/19/97 68.6 32
6/11/97 13.0 103
2/6/03 5.4 42
2/13/03 6.9 48
9/25/03 39.9 199
9/30/03 69.1 183
10/7/03 70.7 192
10/9/03 70.7 187
10/14/03 81.2 150
10/22/03 71.2 142
10/28/03 70.5 153

Note: Valid 30-day geometric means require at least 5 samples within a 30-day period. Results are reported for
every 30-day period, by end date, with 5 or more samples. “Representative flows” are the averages of the flows
associated with each of the individual observations within the 30-day period.

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Chicod Creek Coliform TMDL April 2004
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B-1
Appendix B. Assimilative Capacity and Load Reduction
Calculations
B.1 DEVELOPMENT OF REGRESSION EQUATION
Regression equations were developed to predict fecal coliform load in Chicod Creek (CFU/d) as a
function of flow frequency. The two regression relationships considered were a log-linear relationship
(natural log of load as a function of flow frequency) and a log-log relationship (natural log of load as a
function of the natural log of flow frequency). Based on visual inspection (Figure B-1), the log-linear
regression is appropriate for the analysis, exhibiting a linear relationship with an approximately constant
distribution of residuals.
1E+00
1E+01
1E+02
1E+03
1E+04
1E+05
1E+06
1E+07
1E+08
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Percent of Days Flow is Exceeded
Fe
c
a
l

C
o
l
i
f
o
r
m

L
o
a
d

(
m
i
l
l
i
o
n
s

C
F
U
s
/
d
)
FC Inst Limit Curve Observed LogLinear Regression LogLog Regression

Figure B-1. Regression Equations for Fecal Coliform Load versus Flow Frequency,
Chicod Creek, 1997-2003
Results of the regression analysis are summarized in Table B-1.
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Table B-1. Regression of Natural Logarithm of Fecal Coliform Load on Flow Frequency, Chicod
Creek Fecal Coliform Data, 1997-2003
Regression Statistics
Multiple R 0.839171
R Square 0.704208
Adjusted R Square 0.701543
Standard Error 1.175686
Observations 113

ANOVA
df SS MS F
Regression 1 365.2746 264.2631 3.91E-31
Residual 111 1.382239
Total 112

Coefficients t Stat P-value Lower 95% Upper 95%Lower 95.0%
Intercept 13.57047 54.49662 6.03E-82 13.07703 14.0639 13.07703
Flow %le -7.12253 -16.2562 3.91E-31 -7.99074 -6.25432 -7.99074

B.2 ESTIMATION OF PREDICTION INTERVALS
The method requires the estimation of a prediction interval about the regression line. In addition, because
the regression is in log space, the bias inherent in conversion from log space to arithmetic space must be
addressed.
The regression equation yields a minimum variance unbiased estimate of the local mean value, µ0 of the
natural logarithms of load, conditional on a corresponding value of the independent variable, x0,
(expressed as the deviation from the mean of all observed x values), in this case representing the flow
fraction:
εββµ+⋅+=0100x ,
where is a random disturbance term. The desired confidence limit (in log space) is given by the
prediction interval estimate for an individual realization y0 with mean µ0. This interval addresses both the
uncertainty in estimating the mean and the variability of individual observations about the mean and is
given by
11
2
2
0
2,00 ++⋅⋅±=∑−
i
yn x
x
nstyαµ,
where sy is the sample standard deviation of the y values, and t
-2 is the Student’s t statistic with tail area


n-2 degrees of freedom. For a two-tailed 90 perce
 








Conversion from logarithmic to arithmetic space introduces a bias, as the transform is not symmetrical.
The exact minimum variance unbiased estimator of the arithmetic mean from the logarithmic mean does
not have a closed-form solution, but, for large samples, is closely approximated by (Gilbert, 1987):
Chicod Creek Coliform TMDL April 2004
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B-3





+
=2
0
2
00ysy
ew ,
where w0 is the estimator in arithmetic space and sy0
2 is the local variance about the mean line, or
∑+⋅=2
2
0
0
1
i
yy x
x
nss .

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Chicod Creek Coliform TMDL April 2004
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Appendix C. Public Notification of Public Review Draft of
Chicod Creek TMDL.

Chicod Creek, Tar-Pamlico River Basin

Now Available Upon Request

Chicod Creek Fecal Coliform Total Maximum Daily Load
Public Review Draft – May 2004

Is now available upon request from the North Carolina Division of Water Quality. This TMDL
study was prepared as a requirement of the Federal Water Pollution Control Act, Section
303(d). The study identifies the sources of pollution, determines allowable loads to the
surface waters, and suggests allocations.

TO OBTAIN A FREE COPY OF THE TMDL REPORT:

Please contact Mr. Brian Jacobson [phone], extension 552 or write to:

Mr. Brian Jacobson
Water Quality Planning Branch
NC Division of Water Quality
1617 Mail Service Center
Raleigh, NC 27699-1617

The draft TMDL is also located on the following website: http://h2o.enr.state.nc.us/tmdl. Interested
parties are invited to comment on the draft TMDL study by June 30, 2004. Comments concerning
the report should be directed to Mr. Brian Jacobson at the above address.

Public Meetings Notice

A public meeting to discuss the Chicod Creek Fecal Coliform TMDL
will be held on Monday, June 14th at 10:00am at the following address:

Pitt County Agricultural Center
403 Government Circle
Greenville, NC 27834
Phone: [phone]
Chicod Creek Coliform TMDL April 2004
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