White Oak River TMDL Final

Total Maximum Daily Loads for Fecal Coliform
for the White Oak River,
North Carolina
[Waterbody IDs 20-(18)a1, 20-(18)a2, 20-(18)b, 20-(18)c1, 20-(18)c3, 20-(18)c5, 20-(18)c6, 20-
(18)c7, 20-(18)c8, 20-(18)d, 20-(18)e2, 20-(18)e3]

Final Report
September, 2010

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

White Oak River Basin
White Oak River Fecal Coliform TMDL
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Table of Contents
List of Abbreviations .............................................................................................................. 3
SUMMARY SHEET .................................................................................................................. 4
1 INTRODUCTION .............................................................................................................. 8
1.1 TMDL Components ......................................................................................................... 8
1.2 Documentation of Impairment ..................................................................................... 11
1.3 Watershed Description ................................................................................................. 12
1.4 Water Quality Characterization .................................................................................... 15
2 SOURCE ASSESSMENT .................................................................................................. 16
2.1 Nonpoint Source Assessment ....................................................................................... 16
2.2 Point Source Assessment .............................................................................................. 17
3 TOTAL MAXIMUM DAILY LOADS AND LOAD ALLOCATION ............................................. 19
3.1 TMDL Objective ............................................................................................................. 19
3.2 Previous Studies ............................................................................................................ 19
3.3 Methodology ................................................................................................................. 20
3.3.1 Flow Duration Curve ................................................................................................. 21
3.3.2 Load Duration Curve ................................................................................................. 22
3.4 Total Maximum Daily Load ........................................................................................... 24
3.4.1 Margin of Safety (MOS) ............................................................................................ 25
3.4.2 Target Reduction ....................................................................................................... 25
3.5 TMDL Allocation ............................................................................................................ 27
3.5.1 Waste Load Allocation (WLA) ................................................................................... 27
3.5.2 Load Allocation (LA) .................................................................................................. 28
3.6 Critical Condition and Seasonal Variation .................................................................... 29
3.7 Margin of Safety ............................................................................................................ 29
3.8 Monitoring .................................................................................................................... 29
4 TMDL IMPLEMENTATION PLAN .................................................................................... 29
5 PUBLIC PARTICIPATION ................................................................................................ 30
6 FURTHER INFORMATION .............................................................................................. 30
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7 REFERENCES ................................................................................................................. 31
Appendix A: 2005-2009 Division of Environmental Health Fecal Coliform Data ..................... 32
Appendix B: TMDL Data ....................................................................................................... 34
Appendix C: Public Notification of TMDL for Fecal Coliform for the White Oak River ............ 38
Appendix D: Public Comments ............................................................................................. 40

List of Abbreviations

BMP Best Management Practice
CAFO Confined Animal Feeding Operations
cfs Cubic Feet per Second
CFR Code of Federal Regulations
CWA Clean Water Act
CWP Center for Watershed Protection
DEH Division of Environmental Health
EPA Environmental Protection Agency
FA Future Allocation
GPD Gallons Per Day
HUC Hydrologic Unit Code
LA Load Allocation
LDC Load Duration Curve
MF MF is an abbreviation for the membrane filter procedure for bacteriological
analysis.
ml Milliliter(s)
MLW Mean Low Water
MOS Margin of Safety
MPN Most Probable Number
MRLC Multi-Resolution Land Cover
NOAA National Oceanic and Atmospheric Administration
NCAC NC Administration Code
NCDWQ North Carolina Division of Water Quality
NCDENR North Carolina Department of Environment and Natural Resources
NSSP National Shellfish Sanitation Program
SA Class SA water body: suitable for commercial shellfishing and all other tidal
saltwater use
SSO Sanitary Sewer Overflows
TMDL Total Maximum Daily Load
USDA U.S. Department of Agriculture
USGS United States Geological Survey
WLA Waste Load Allocation
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WWTF Waste Water Treatment Facility

SUMMARY SHEET
Total Maximum Daily Load (TMDL)

1. 303(d) Listed Waterbody Information

State: North Carolina

County: Carteret, Craven, Jones, Onslow

Major River Basin: White Oak River Basin

Watershed: Headwaters White Oak River, Outlet White Oak River (USGS HUC 0302030101,
0302030102)

Impaired Waterbody (2008 303(d) List):

Waterbody Name – [ID] Description
Water
Quality
Classification
Acres
White Oak River – [20-(18)a1] DEH closed area from Hunters
Creek to DEH closure line SA HQW 792.6
White Oak River – [20-(18)a2] DEH closed area from Hunters
Creek to DEH closure line SA HQW 1177.6

White Oak River – [20-(18)b]
From DEH Conditionally Approved
Closed Line to DEH Conditionally
Approved Open Line

SA HQW 230.5
White Oak River – [20-(18)c1] From DEH Conditionally Approved
Closed line to the DEH
Conditionally Approved Open line
SA HQW 183.0
White Oak River – [20-(18)c3] From DEH Conditionally Approved
Closed line to the DEH
Conditionally Approved Open line
SA HQW 1849.8
White Oak River – [20-(18)c5] From DEH Conditionally Approved
Closed line to the DEH
Conditionally Approved Open line
SA HQW 28.1
White Oak River – [20-(18)c6] From DEH Conditionally Approved
Closed line to the DEH
Conditionally Approved Open line
SA HQW 31.3
White Oak River – [20-(18)c7] From DEH Conditionally Approved
Closed line to the DEH
Conditionally Approved Open line.
Prohibited area at Hwy 24 bridge
SA HQW 21.4
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White Oak River – [20-(18)c8] From DEH Conditionally Approved
Closed line to the DEH
Conditionally Approved Open line.
Prohibited area Dolphin Bay Estates
and Canal
SA HQW 6.9
White Oak River – [20-(18)d] DEH closed area adjacent to the
east side of the White Oak River
restricted area
SA HQW 7.7
White Oak River – [20-(18)e2] From the DEH Conditionally
Approved Open line to the Atlantic
Ocean excluding the ICWW
SA HQW 31.9
White Oak River – [20-(18)e3] From the DEH Conditionally
Approved Open line to the Atlantic
Ocean excluding the ICWW.
Dudleys Marina and Boataminiums
SA HQW 5.5

Constituent(s) of Concern: Fecal Coliform Bacteria

Designated Uses: Shellfish harvesting, biological integrity, propagation of aquatic life, and
recreation.

Applicable Tidal Salt Water Quality Standards for Class SA Waters:

“Organisms of coliform group: fecal coliform group not to exceed a median MF of 14/100 ml
and not more than 10 percent of the samples shall exceed an MF count of 43/100 ml in
those areas most probably exposed to fecal contamination during the most unfavorable
hydrographic and pollution conditions.”

For the approval of shellfish growing areas “the median fecal coliform Most Probable
Number (MPN) or the geometric mean MPN of water shall not exceed 14 per 100 milliliters,
and not more than 10 percent of the samples shall exceed a fecal coliform MPN of 43 per
100 milliliters (per five tube decimal dilution) in those portions of areas most probably
exposed to fecal contamination during most unfavorable hydrographic conditions”(15A
NCAC 18A .0431 Standards for an Approved Shellfish Growing Area). In addition “a minimum
of the 30 most recent randomly collected samples from each sample station shall be used to
calculate the median or geometric mean and 90th percentile to determine compliance with
this standard” (NSSP, 2007).

2. TMDL Development

Development Tools (Analysis/Modeling):
Load duration curves are based on cumulative frequency distribution of flow conditions in
the watershed. Allowable loads are average loads over the recurrence interval between
the 95th and 10th percent flow exceeded (excludes extreme drought (>95th percentile)
and floods (<10th percentile). Percent reductions are expressed as the average value
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between existing loads (typically calculated using an equation to fit a curve through actual
water quality violations) and the allowable load at each percent flow exceeded.

Critical Conditions:
The 90th percentile concentration of 43 MPN/100 ml is the concentration exceeded only
10% of the time. Since the data used in the load duration curve spans ten years (2000-
2009), the critical condition is implicitly included in the value of the 90th percentile of the
load duration curve results. Given the length of the monitoring record and load duration
curve calculation and the standard’s recognition of unusual and infrequent events, the
90th percentile is used instead of the absolute maximum.

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 water quality
data collected in the watershed.

3. TMDL Allocation Summary

The load duration curve results show that the 90th percentile component of the
standard, rather than the median component, requires the highest reduction; therefore
to be protective, the allocation is established based on 90th percentile load.

Waterbody Pollutant Existing
Load WLA LA Explicit
MOS1 TMDL
White Oak River 20-
(18)a1, 20-(18)a2, 20-
(18)b, 20-(18)c1, 20-
(18)c3,, 20-(18)c5, 20-
(18)c6, 20-(18)c7, 20-
(18)c8, 20-(18)d, 20-
(18)e2, 20-(18)e3
Fecal
Coliform
(cfu/day)
5.40E+11 7.32E+9 1.09E+11 1.77E+10 1.34E+11
1. The Margin of safety is included in the TMDL by lowering the fecal coliform standard from 43 to 38 cfu/100 ml. The MOS shown here is
the difference between the TMDL calculated at the 43 and 38 cfu/100 ml standards.

4. Contributing Municipalities TMDL Allocation Summary: N/A
5. Contributing NPDES Facilities TMDL Allocation Summary:
NPDES Permittee Existing Load
(cfu/day) WLA (cfu/day) Percent Reduction
Required
Maysville WWTP 2.73E+09 2.73E+09 0%
Silverdale Elementary
School WWTP 4.5E+07 4.5E+07 0%
Webb Creek WWTP 4.54E+09 4.54E+09 0%
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NC DOT N/A N/A 75.2%

6. Public Notice Information
Summary: The TMDL public comment period was announced on the
NC Modeling and TMDL website on 7/12/10, on the WRRI
listserv on 7/14/10, and the Carteret County News-Times
on 7/16/10.
Did notification contain specific
mention of TMDL Proposal?
Yes
Were comments received from
the public?
Yes
Was a responsiveness summary
prepared?
Yes

7. Public Notice Date: 7/12/10
8. Submittal Date: 8/20/10
9. Establishment Date: 9/7/10
10. EPA Lead on TMDL (EPA or blank):
11. DOT a Significant Contribution (Yes or Blank): Yes
12. Endangered Species (yes or blank):
13. MS4s Contributions to Impairment (Yes or Blank):
14. TMDL Considers Point Source, Nonpoint Source, or both: Both
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1 INTRODUCTION

Section 303(d) of the federal Clean Water Act (CWA) and the U.S. Environmental Protection
Agency’s (EPA) implementing regulations direct each State to develop a Total Maximum Daily
Load (TMDL) for each impaired water quality limited segment on the Section 303(d) list, taking
into account seasonal variations and a protective margin of safety (MOS) to account for
uncertainty. A TMDL reflects the total pollutant loading that a waterbody can receive and still
meet water quality standards.
TMDLs are established to achieve and maintain water quality standards. A water quality
standard is the combination of a designated use for a particular body of water and the water
quality criteria designed to protect that use. Designated uses include activities such as
swimming, drinking water supply, and shellfish propagation and harvest. Water quality criteria
consist of narrative statements and numeric values designed to protect the designated uses.
Criteria may differ among waters with different designated uses.
The White Oak River is located in the White Oak River Basin (NC Subbasin 30501 – HUCs
0302030101 and 0302030102) along the North Carolina coast in Carteret, Craven, Jones, and
Onslow Counties. The river is located within the shellfish area designated D-3 by the North
Carolina Division of Environmental Health (NCDEH). Over two-thirds of the shellfish growing
areas are conditionally open or closed, or are prohibited (Figure 1.1). Conditionally Approved
Closed waters are closed except after extended dry periods when the areas may be opened for
shellfish harvesting. Rainfall of 0.5 inches or greater within a 24-hour period or 0.75 inches
within a 48-hour period immediately closes the waters to shellfish harvesting.

When shellfish harvesting is the designated use, the problem parameter that might impair this
use is fecal coliform bacteria. Fecal coliform bacteria are found in the intestinal tract of humans
and other warm-blooded animals. Few fecal coliform bacteria are pathogenic; however, the
presence of elevated levels of fecal coliform in shellfish waters indicates recent sources of
pollution. Some common waterborne diseases associated with the consumption of raw clams
and oysters harvested from polluted water include viral and bacterial gastroenteritis and
hepatitis A. Fecal coliform in surface waters may come from point sources (e.g., NPDES
stormwater conveyances) and nonpoint sources.

1.1 TMDL Components

The 303(d) process requires that a TMDL be developed for each of the waters appearing in
Category 5 of a state’s Integrated Report. 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). This TMDL is the total amount of a pollutant that can
be assimilated by the receiving water while still achieving North Carolina’s water quality criteria
for shellfish waters. Currently, TMDLs are expressed as a “mass per unit time, toxicity, or other
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appropriate measure” (40 CFR 130.2(i)). It is also important to note that the TMDLs presented
herein are not literal daily limits. These loads are based on an averaging period that

Figure 1.1: White Oak River Shellfish Growing Area (D-3) Classifications
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is defined by the water quality criteria (i.e., 30 samples per station). The averaging period used
for development of these TMDLs requires at least 30 samples and uses the most recent 2.5-year
window of data, assuming one sample per month. Generally, the primary components of a
TMDL, as identified by EPA (1991, 1999) and the Federal Advisory Committee (USEPA, 1998) are
as follows:

Target Identification or selection of pollutant(s) and end-point(s) for consideration. The
pollutant and end-point are generally associated with measurable water quality related
characteristics that indicate compliance with water quality standards. North Carolina indicates
known pollutants on the 303(d) list.

Source Assessment. All sources that contribute to the impairment should be identified and
loads quantified, where sufficient data exist.

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 non-point sources, stormwater, and
natural background.

Margin of Safety. The margin of safety addresses uncertainties associated with pollutant loads,
modeling techniques, and data collection. Per EPA (2000a), the margin of safety may be
expressed explicitly as unallocated assimilative capacity or implicitly due to conservative
assumptions.

Seasonal Variation. The TMDL should consider seasonal variation in the pollutant loads and
end-point. Variability can arise due to stream flows, temperatures, and exceptional events
(e.g., droughts, hurricanes).

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

Section 303(d) of the CWA and the Water Quality Planning and Management regulation
(USEPA, 2000a) 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.
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Where conditions are not appropriate for the development of a TMDL, management strategies
may still result in the restoration of water quality.

TMDL is comprised of the sum of individual wasteload allocations (WLAs) for point sources, load
allocations (LAs) for nonpoint sources, and natural background levels. 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, and in the
scientific and technical understanding of water quality in natural systems.

TMDL = WLAs + LAs + MOS

1.2 Documentation of Impairment

The North Carolina Division of Water Quality (DWQ) Surface Water and Wetlands classification
for these impaired waters is Class SA, HQW Waters – Shellfish Harvesting Waters (15A NCAC
02B.0221 Tidal Salt Water Quality Standards for Class SA Waters). Class SA waters are
waterbodies suitable for commercial shellfishing and all other tidal saltwater use (NCAD 2003).

Thirteen segments, or assessment units, of the Southeast White Oak River have been included
in Category 5 the 2008 North Carolina Integrated Report. These restricted shellfish harvesting
areas are identified as areas in this basin that do not meet their designated uses. Waters within
this classification, according to 15A NCAC 02B.0221 (Tidal Salt Water Quality Standards for Class
SA Waters), must meet the following water quality standard in order to meet their designated
use: “Organisms of coliform group: fecal coliform group not to exceed a median MF of
14/100 ml and not more than 10 percent of the samples shall exceed an MF count of 43/100
ml in those areas most probably exposed to fecal contamination during the most unfavorable
hydrographic and pollution conditions.” In addition, for the approval of shellfish growing areas
“the median fecal coliform Most Probable Number (MPN) or the geometric mean MPN of
water shall not exceed 14 per 100 milliliters, and not more than 10 percent of the samples
shall exceed a fecal coliform MPN of 43 per 100 milliliters (per five tube decimal dilution) in
those portions of areas most probably exposed to fecal contamination during most
unfavorable hydrographic conditions”(15A NCAC 18A .0431 Standards for an Approved
Shellfish Growing Area). In addition “a minimum of the 30 most recent randomly collected
samples from each sample station shall be used to calculate the median or geometric mean
and 90th percentile to determine compliance with this standard” (NSSP, 2010).

For this report, the monitoring data-averaging period was based on monitoring procedures
from the National Shellfish Sanitation Program, i.e. fecal coliform concentration cannot exceed
a median or a geometric mean of an MPN of 14 per 100 ml and the 90th percentile of an MPN of
43 per 100 ml, for six samples per year and 30 samples per station. The averaging period for
the monitoring data required at least 30 samples. The water quality impairment was assessed
using the median and 90th percentile concentrations.
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1.3 Watershed Description

The White Oak River is a 42-mile long blackwater river located along the central North Carolina
coast. The watershed encompasses portions of Jones, Carteret, Craven, and Onslow counties
and covers 273 square miles. Figure 1.2 shows the location of the river and watershed. The
headwaters are located within 35 square miles of Hoffman Forest, a forestry research
laboratory, and Croatan National Forest covers the majority (105 sqmi) of the eastern portion
of the watershed. Agriculture and forest are dominant land uses in the upper watershed. The
river begins to widen approximately nine miles before flowing into Bouge Sound; here the river
classification changes from class C,HQW to class SA,HQW. This point marks the northern
boundary of the Division of Environmental Health Shellfish Growing area D-3 which extends
south to Bogue Sound. Uncharacteristic steep slopes and grades characterize upland portions of
the growing area. This area has seen rapid residential development in recent years. Oyster and
clam production are good throughout the area, however approximately two-thirds of the
shellfish beds areas are prohibited, or conditionally closed or open, due to high fecal coliform
pollution. The dominant tide in this region is the lunar semi-diurnal (M2) tide with a mean tidal
range of 3.11 ft based on the NOAA station at Beaufort, NC (NOAA, 2010).

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Figure 1.2 Location Map of the White Oak River
The 2001 National Land Cover Database (NLCD) was used to obtain land cover characteristics of
the watershed. Land cover distribution is shown in Figure 1.3 and land cover statistics are
shown in Table 1.1. It is likely that some crop land along the southern portion of the river has
been converted to residential developments since 2001. The next planned land cover database
(2006 NLCD) is currently under development.

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Figure 1.3 2001 NLCD Land Cover of the White Oak River Watershed

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Table 1.1 Land Cover Distribution of the WOR Watershed

1.4 Water Quality Characterization

The NC Division of Water Quality Ambient Monitoring System (AMS) is a network of stream,
lake, and estuarine stations strategically located for the collection of physical and chemical
water quality data. AMS station P6400000 is located on the White Oak River near Stella, NC
(shown in Figure 3.2). This station was established in 1969 and monthly routine sample
collection here provided long term data on fecal coliform concentrations for this project. A
statistical summary of data from this station is included in Table 1.2.

Table 1.2. White Oak River Sampling
Station Sampling
Period
Number of
Samples
Collected
Approximate
Sampling
Frequency
Sample
Median
Sample
90th
Percentile
P6400000 1/13/2000–
4/15/2009 101 Monthly 42 cfu/100
mL
150
cfu/100 mL

The Shellfish Sanitation and Recreational Water Quality Section of the Division of Environ-
mental Health (DEH) is responsible for classifying shellfish harvesting waters to ensure oysters
and clams are safe for human consumption. NCDEH adheres to the requirements of the
National Shellfish Sanitation Program, with oversight by the U.S. Food and Drug Administra-
tion. NCDEH conducts shoreline surveys and collects routine bacteria water quality samples in
Land Cover Description Percent Square Miles
Woody Wetlands 36.3% 99.24
Evergreen Forest 25.9% 70.72
Cultivated Crops 11.0% 30.17
Grassland/Herbaceous 6.8% 18.66
Mixed Forest 5.2% 14.25
Open water 5.1% 13.82
Developed, Open Space 2.8% 7.56
Scrub/Shrub 2.4% 6.53
Emergent Herbaceous Wetland 1.6% 4.25
Deciduous Forest 1.3% 3.50
Developed, Low Intensity 0.7% 1.93
Pasture/Hay 0.7% 1.85
Developed, Medium Intensity 0.2% 0.48
Barren Land 0.1% 0.34
Developed, High Intensity 0.0% 0.07
Total 100% 273.37
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the shellfish-growing areas of North Carolina. The data are used to determine if the water
quality criteria are being met. If the water quality criteria are exceeded, the shellfish areas are
closed to harvest, at least temporarily, and consequently the designated use is not being
achieved. DEH data from 2005-2009 are summarized in Appendix A.

NCDEH has monitored shellfish growing regions throughout North Carolina for the past several
decades. The White Oak River is sampled using the systematic random sampling strategy as
outlined in the National Shellfish Sanitation Program’s Model Ordinance and guidance
document. In addition to the routine bacteriological monitoring of the areas, conditional area
samples are collected after rainfall events for some stations. There are 37 fecal coliform
monitoring stations sampled by the NC DEH; during the 2006 Sanitary Survey 6 stations did not
meet standards for growing area criteria. In general, a decline in water quality was observed
between the 2003 and 2006 Sanitary Survey Reports (DEH, 2006). The next Sanitary Survey of
the D-3 growing area is scheduled for summer 2010.

2 SOURCE ASSESSMENT

2.1 Nonpoint Source Assessment

Non-point sources are diffuse sources that typically cannot be identified as entering a water
body at a single location. Nonpoint source loading typically occurs during rain events when
surface runoff transports water carrying fecal coliform over the land surface and discharges it
into the stream network. The transport of fecal coliform from the land to the restricted shellfish
harvesting area is dictated by the hydrology, soil type, land use, and topography of the
watershed.

There are many types of nonpoint sources in watersheds that contribute to the restricted
shellfish harvesting areas. Fecal coliform bacteria from non-human sources originate from
excretions from wildlife, livestock and pets. Wildlife in the watershed are considered to make
up background concentrations of fecal coliform. For Dubling Creek, Boathouse Creek, and Hills
Bay watersheds (embayments on the WOR), wildlife source loads were estimated to make up
an average of 94.3% of daily fecal coliform counts, followed by pet and failing septic sources at
5.6% and 0.3% respectively (NCDENR, 2009). A more direct path to the shellfish areas occurs
when wildlife defecate in, or even inhabit, the drainage network, including stream and wetland
channels, and stormwater conveyance pipes.

Grazing animals contribute fecal coliform through either direct access to streams or runoff from
deposition or manure spreading. Land cover data for the watershed indicates that pasture/hay
land area (grazing land) represents less than 1 percent of the watershed. The cultivated crops
land cover is concentrated near the river (Figure 1.3) and runoff could be a contributing factor if
manure is improperly applied, particularly if just before a storm event. Table 2.1 represents the
number of county wide farms and animals for counties in the White Oak River drainage area.
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Table 2.1. Number of Farms and Animals by County (2007 Agricultural Census)
County Cattle and calves Horses and Ponies Sheep and Lambs Goats
Farms Animals Farms Animals Farms Animals Farms Animals
Carteret 8 159 47 306 no data no data 13 63
Craven 31 932 40 278 10 11 34 423
Jones 38 3538 29 172 12 239 15 256
Onslow 89 1986 109 765 11 116 47 643

Nonpoint source contributions to the bacterial levels from human activities generally arise from
malfunctioning or improperly-sited septic systems and their associated drain fields, or illicit
connections of sanitary sewage to the stormwater conveyance system. However the human
contribution is not expected to be significant. Two possible illicit connections and two potential
septic systems failures were identified in the 2006 sanitary survey and were reported to the
Onslow County Health Department (NCDEH, 2006). In addition, as part of the North Carolina
Coastal Federation’s White Oak Restoration Project, 220 bacteria samples were collected from
the three embayment watersheds. DNA from 15 of the highest samples were analyzed by the
University of North Carolina’s Institute of Marine Sciences and all samples were from natural
sources (non human) (NCCF, 2009).

2.2 Point Source Assessment

All wastewater discharges to surface water in the State of North Carolina must receive a permit
to control water pollution. The Clean Water Act of 1972 initiated strict control of wastewater
discharges with responsibility of enforcement given to the Environmental Protection Agency
(EPA). The EPA then created the National Pollutant Discharge Elimination System (NPDES) to
track and control point sources of pollution. The primary method of control is by issuing
permits to discharge with limitations on wastewater flow and constituents. The EPA delegated
permitting authority to the State of North Carolina in 1975. Table 2.2 shows dischargers in the
White Oak River. Locations of dischargers are shown in Figure 2.1.

Table 2.2 NPDES Waste Water Dischargers in the White Oak River Watershed
Facility Permit Type
Permitted
Flow
(GPD)
Monthly
Average
Limit
Weekly
Average
Limit
Daily
Max
Limit
Maysville
WWTP NC0021482 Municipal
<1 MGD 180,000 200#/100ml 400#/100ml
Silverdale
Elementary
School WWTP
NC0050849
100%
Domestic
<1 MGD
3,000 200#/100ml 400#/100ml
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Facility Permit Type
Permitted
Flow
(GPD)
Monthly
Average
Limit
Weekly
Average
Limit
Daily
Max
Limit
Webb Creek
WWTP
NC0062624
100%
Domestic
<1 MGD
300,000 200#/100ml 400#/100ml

Human sewage can be discharged to surface waters during sanitary sewer overflow (SSO)
events due to a failure at a pump station or storm water infiltration. Five SSOs were recorded in
the watershed during years 2000-2010. At this frequency it is unlikely that SSOs are a significant
source fecal coliform concentrations. In addition Swansboro has slip lined some of the sewer
lines in recent years to decrease groundwater infiltration. (NC DEH 2006 – Sanitary survey)

Figure 2.1- Potential Fecal Coliform Sources in the White Oak River Watershed.
Note: The subdivisions and stormwater conveyance locations are from the 2006 shoreline survey conducted by the NC DEH, data is limited to
the vicinity of the shellfish growing areas.

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The NC Department of Transportation (NCDOT) has a number of roads in the project area,
including Highways 24 and 58, which are covered under their statewide Phase I NPDES
stormwater permit (NCS000250). Stormwater has previously been considered to be a nonpoint
source; however, NPDES-permitted sources are to be included in the wasteload allocation
(WLA) per EPA guidance (USEPA, 2002).

Six swine operations hold North Carolina animal operation permits in the watershed (NC DWQ
2003). Two permit violations were found, one for over-application of land applied waste and a
freeboard violation for a waste lagoon. If operating according to the permit requirements,
these facilities should not be a source of fecal coliform in the White Oak River.

3 TOTAL MAXIMUM DAILY LOADS AND LOAD ALLOCATION

3.1 TMDL Objective

The TMDL objective is to meet North Carolina water quality fecal coliform standards of a
median MF of 14/100 ml and not more than 10 percent of the samples shall exceed an MF
count of 43/100 ml. In addition, the National Shellfish Sanitation Program (NSSP) standard for
the approved classification of growing areas requires that fecal coliform concentrations not
exceed a median or geometric mean of a MPN of 14 per 100 ml and the 90th percentile of a
MPN of 43 per 100 ml, with a minimum of the 30 most recent samples used to calculate
compliance.

Both standards have the same numeric targets but the NSSP standard uses a minimum 30-
sample averaging period. For the purpose of this TMDL, data collected from 2000 through 2009
were used. The longer period of data accounts for the variation in precipitation and flow from
year to year.

3.2 Previous Studies

Several Studies on the White Oak River have been conducted recently. In March, 2008, Tetra
Tech, Inc. (Tetra Tech) was contracted by the US EPA to develop a TMDL development protocol
for shellfish waters in the White Oak River. In this report, three tiers of TMDL approaches were
developed: the load duration curve methodology (tier 1), spreadsheet tidal prism (tier 2), and a
3-dimensional, hydrodynamic, fate, and transport model (tier 3). The river was segmented into
3 different sections, A, B and C, based on how the Ambient Station and DEH stations were
grouped. Results and reductions required by segment and tier are provided in Table 3.1.

White Oak River Fecal Coliform TMDL
________________________________________________________________________

20

Table 3.1 – Excerpt of Results and Reductions from the Fecal Coliform TMDL 3 Tiered Approach (Tetra Tech, 2008)

In March 2009, a TMDL was approved by the US EPA for fecal coliform in several embayments
on the southeast White Oak River. This TMDL serves as a valuable source of watershed specific
information including aerial orthophotography based land cover, landowner surveys, and
additional bacteria monitoring. The fecal coliform load was estimated by using the linked
watershed and Tidal Prism modeling approach and was used to simulate fecal coliform
concentrations in embayments. The model results showed that the 90th percentile portion of
the standard required the most reduction. Table 3.2 shows the TMDL allocation and reductions
required based on the 90th percentile load. This TMDL can be viewed on the internet at
http://portal.ncdenr.org/web/wq/ps/mtu/tmdl/tmdls#white_oak.

Table 3.2- Excerpt of reductions required for the WOR Embayment TMDL
Waterbody Pollutant Existing WLA LA MOS1
Reduction
Required2 TMDL

Boathouse Creek -
(20-31)
Fecal coliform
(counts/day) 6.17××××1011 9.91××××109 1.75××××1011 2.41××××1010 66% 2.09××××1011

Dubling Creek - (20-
30)
Fecal coliform
(counts/day) 1.77××××1011 0.00 1.53××××1011 5.00××××109 11% 1.58××××1011

White Oak River – (20-
(18)c4)
Fecal coliform
(counts/day) 2.88××××1010 6.60××××108 1.24××××1010 1.44××××109 50% 1.45××××1010
Notes: WLA = wasteload allocation, LA = load allocation, MOS = margin of safety
1 Margin of safety (MOS) equivalent 11.6 percent of the target concentration in all embayments. Used a target of 38
instead of 43. MOS load in table represents the difference between total loading using those targets.
2 The reduction required in this table includes the margin of safety. The actual reduction required should not count the
margin of safety so the overall reductions required would be 70%, 14%, and 55%, respectively.

3.3 Methodology

The load duration curve method is intended to be a simplistic method to calculate pollutant
reductions. This method was chosen for the White Oak River because of the availability of long-
term data and is an efficient method to calculate a percent load reduction from non-point
White Oak River Fecal Coliform TMDL
________________________________________________________________________

21

sources. The required load reduction was determined based on water quality monitoring and
stream flow data from January 2000 through April 2009.

3.3.1 Flow Duration Curve

Development of a flow duration curve is the first step of the load duration approach. A flow
duration curve employs a cumulative frequency distribution of measured daily stream flow over
the period of record. The curve relates flow values measured at the monitoring station for the
percent of time the flow values were equaled or exceeded. Flows are ranked from lowest,
which are exceeded nearly 100 percent of the time, to highest, which are exceeded less than 1
percent of the time. Reliability of the flow duration curve depends on the period of record
available at monitoring stations. Accuracy of the curve increases when longer periods of record
are used. The flow duration curve, shown in Figure 3.1, was used to determine the seasonality
and flow regimes during which the exceedances of the pollutants occurred.

Figure 3.1 – Flow Duration Curve for the White Oak River at DWQ Station P6400000
Daily flow data was used from USGS New River gauging station 2093000, located adjacent to
the west of the White Oak River. The drainage area ratio of 2.5 was applied to the daily flows to
compensate the larger drainage area of the White Oak River at the ambient monitoring station.

1
10
100
1000
10000
100000
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Da
i
l
y

S
t
r
e
a
m

F
l
o
w

(
c
f
s
)
Percent of Days Flow Exceeded
Flow Duration Curve for the White Oak River at DWQ Station
P6400000
White Oak River Fecal Coliform TMDL
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22

Figure 3.2 – Comparison of Drainage Areas on the New and White Oak Rivers
3.3.2 Load Duration Curve

A load duration curve is developed by multiplying the flow values along the flow duration curve
by the pollutant concentration and the appropriate conversion factors. The allowable load
assumes a fecal coliform concentration based on water quality numeric criteria and margin of
safety. The target, or allowable load line, resembles the flow duration curve; hence it
determines the assimilative capacity of a stream or river under different flow conditions. Values
above the line are exceeded loads and values below the line are acceptable loads. Therefore, a
load duration curve can help define the flow regime during which exceedances occur. Four
variations of the load duration curve were developed for this TMDL to account for different
numeric targets and averaging periods (Table 3.3).

White Oak River Fecal Coliform TMDL
________________________________________________________________________

23

Table 3.3 – Variations of the Load Duration Curve based on different targets within the standards.
Pollutant Target with
MOS
Statistical
Parameter
Data
Averaging
Period
Number of
Observations
Data Points
used in LDC
Fecal
Coliform
(cfu/day)
12cfu/100ml Median All data 101 101
38cfu/100ml 90th %ile All data 101 101
12cfu/100ml Median 30
samples 101 72
38cfu/100ml 90th %ile 30
samples 101 72

Figure 3.3 shows existing loads plotted against the allowable load. Figure 3.4 shows a second
flow duration curve using 30-sample 90th percentiles. For the White Oak River, the criteria
violations occurred at all ranges of flows, suggesting that contamination due to fecal coliform
occurred during both wet and dry conditions.

Figure 3.3 – Load Duration Curve for the WOR at DWQ Station P6400000

1E+09
1E+10
1E+11
1E+12
1E+13
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Fe
c
a
l

C
o
l
i
f
o
r
m

L
o
a
d

(
c
f
u
/
d
a
y
)
<--Higher Flows Percent Days Flow Exceeded Lower Flows-->
Load Duration Curve for the WOR at Station P6400000
Allowable Load Actual Load
White Oak River Fecal Coliform TMDL
________________________________________________________________________

24

Figure 3.4 – 30-Sample Averaging Period Load Duration Curve for the WOR at Ambient Station P6400000. The Actual Load is
based on 30-sample 90th percentiles and the median flow and the Allowable Load is based on daily flow and calculated at the
standard of 38 cfu/100ml.

3.4 Total Maximum Daily Load

Total Maximum Daily Load (TMDL) can be defined as the total amount of pollutant that can be
assimilated by the receiving water body while achieving water quality standards. A TMDL can
be expressed as the sum of all point source allocations (WLAs), nonpoint source allocations
(LAs), and an appropriate margin of safety (MOS), which takes into account any uncertainty
concerning the relationship between effluent limitations and water quality. This definition can
be expressed by equation 3.1.

∑∑++=MOSLAsWLAsTMDL (3.1)

The objective of the TMDL is to estimate allowable pollutant loads and to allocate those loads
in order to implement control measures and to achieve water quality standards. The Code of
Federal Regulations (40 CFR § 130.2 (1)) states that TMDLs can be expressed in terms of mass
per time, toxicity, or other appropriate measures. For fecal coliform contamination, TMDLs are
expressed as counts, or colony forming units (cfu), per 100 milliliters. TMDLs represent the
maximum one-day load the river can assimilate and maintain the water quality criterion. A load
duration curve approach was utilized to estimate the TMDL for fecal coliform. The systematic
procedures adopted to estimate TMDLs are described below.

1E+09
1E+10
1E+11
1E+12
1E+13
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Fe
c
a
l

C
o
l
i
f
o
r
m

L
o
a
d

(
c
f
u
/
d
a
y
)
<--Higher Flows Percent Days Flow Exceeded Lower Flows-->
30-Sample Load Duration Curve for the WOR at Station P6400000
Actual Load Allowable Load
White Oak River Fecal Coliform TMDL
________________________________________________________________________

25

3.4.1 Margin of Safety (MOS)

The MOS is included in the TMDL estimation to account for the uncertainty in the simulated
relationship between the pollutants and the water quality standard. In this study, the MOS was
explicitly included in the following TMDL analysis by setting the TMDL target at 10 percent
lower than the water quality target for fecal coliform. The water quality standard and the
target can be seen in Table 3.4.

Table 3.4 - Water Quality Standards and Margin of Safety
Pollutant Standard Standard w/
MOS
Fecal
Coliform
(cfu/day)
<14cfu/100ml <12cfu/100ml
<43cfu/100ml <38cfu/100ml

3.4.2 Target Reduction

The load reduction needed to meet the fecal coliform standards was estimated with the
observed data that exceeded the applicable water quality standard within the 10th to 95th
percentile flow recurrence range. Typically the remaining flow recurrence range is not included
in the TMDL calculation to allow cases of extreme drought or flood to be excluded. The
reductions required are shown in table 3.5

Table 3.5 – Load Reduction Requirements under variations of standard criteria
Pollutant Target with
MOS
Statistical
Parameter
Data
Averaging
Period
Estimated
Exceeding
Load
Allowable
Load
(TMDL-MOS)
Average
Reduction
Required
Fecal
Coliform
(cfu/day)
12cfu/100ml Median None 1.33E+11 4.08E+10 69.5%
38cfu/100ml 90th %ile None 5.53E+11 3.29E+11 40.6%
12cfu/100ml Median 30
samples 1.34E+11 4.24E+10 68.3%
38cfu/100ml 90th %ile 30
samples 5.4E+11 1.34E+11 75.2%

The greatest reduction required was calculated under the NSSP standard of using the 90th
percentile of 38 cfu/100 ml (including explicit MOS). This standard was used to calculate the
TMDL. Figure 3.5 shows the actual load calculated from the thirty sample 90th percentile and
the median flow and the allowable load calculated from the standard and the 30 sample
median flow.

White Oak River Fecal Coliform TMDL
________________________________________________________________________

26

Figure 3.5 – Load Duration Curve with Allowable and Estimated Exceeding Loads of Fecal Coliform in the WOR at Station
P6400000
The exponential curve equation for these data points violating the water quality criterion is
shown in Equation 3.2.

y = 1E+12E-1.277x R² = 0.4351 (3.2)
Where, y = fecal coliform (cfu/100ml) and x = Percent Flow Exceeded.

To present the TMDL as a single value, the existing load was calculated from the exponential
curve equation as the average of the load violations occurring when the flow exceeded at a
frequency greater than 10 percent and less than 95 percent. Additionally, the average load was
calculated by using percent flow exceedances in multiples of 5 percent. The allowable loads for
each exceedance were calculated from the TMDL target value, which includes the 10 percent
MOS.

The required reduction of 75.2 percent was calculated by taking the difference between the
average of the exponential curve load estimates and the average of the allowable load
estimates. For example, at each recurrence interval between 10 and 95 (again using recurrence
intervals in multiple of 5), the equation of the exponential curve was used to estimate the
existing load. The allowable load was then calculated in a similar fashion by substituting the
allowable load curve. The estimated values are given in Appendix Table B.2.

The reduction established based on the 90th percentile criterion indicates that the water body
will meet the water quality standard requiring not more than 10% of the samples to exceed an
MF count of 43/100 ml. Using the 90th percentile in this manner is consistent with the
procedure used by DEHSS on their sample data for determining whether shellfish areas should
be open, conditionally prohibited, or closed.
y = 1E+12e-1.277x
R² = 0.4351
1E+09
1E+10
1E+11
1E+12
1E+13
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Fe
c
a
l

C
o
l
i
f
o
r
m

L
o
a
d

(
c
f
u
/
d
a
y
)
<-- Higher Flows Percent Days Flow Exceeded Lower Flows-->
30 Sample Load Duration Curve for the WOR at Station 640000
Allowable Load Actual Load Expon. (Actual Load)
White Oak River Fecal Coliform TMDL
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27

3.5 TMDL Allocation

3.5.1 Waste Load Allocation (WLA)

Three waste water treatment facilities (WWTF) plus the NC Department of Transportation hold
NPDES permits in the White Oak River watershed. The three WWTF load contributions are
shown in Table 3.6

Table 3.6 – Existing NPDES Load Contributions
Facility Name Permit
Number
Flow
(mgd)
Flow
(cfs) Permit Limit Load
(cfu/day)
% of
Median
Ambient
Station
Load
Stream
Miles to
DWQ
station
Maysville WWTF NC0021482 180000 0.2785 400#/100ml 2.73E+09 2.0% 16
Silverdale
Elementary School
WWTF
NC0050849 3000 0.0046 400#/100ml 4.54E+07 0.03% 8
Webb Creek
WWTF* NC0062642 300000 0.4642 400#/100ml 4.54E+09 3.33%
3 to
White
Oak *
* This facility discharges 1.5 miles below the DWQ station but was assumed to discharge at the DWQ station for this calculation.

In order to estimate contributions from the WWTFs, it was assumed that all discharges were
located at the ambient station, and that all fecal coliform discharged reaches the ambient
station with no attenuation. Based on facility limits of flow and the more stringent daily or
weekly fecal coliform concentrations, the combined WWTF load could contribute 5.36% of the
median load at DWQ station 6400000 based on data from years 2000 through 2009. However,
this load percentage assumes all facilities discharge at the Ambient Station. Factoring actual
distances from the Ambient Station, bacteria die-off, and the relatively small loading
percentage calculated above, it appears that these WWTFs do not present a significant load to
the White Oak River. Therefore it was assumed that the WWTFs are adequately regulated
under existing permits and the waste load allocations in this TMDL were calculated at the
existing permit limits. The waste load allocation for NPDES permittes in the White Oak River
watershed are shown in Table 3.7.

White Oak River Fecal Coliform TMDL
________________________________________________________________________

28

Table 3.7 – NPDES Waste Load Allocations and Required Reductions
NPDES Permittee Existing Load
(cfu/day) WLA (cfu/day) Percent Reduction
Required
Maysville WWTP 2.73E+09 2.73E+09 0%
Silverdale Elementary
School WWTP 4.5E+07 4.5E+07 0%
Webb Creek WWTP 4.54E+09 4.54E+09 0%
NC DOT N/A N/A 75.2%

Because of the non-point source nature of drainage from roads and highways, data is not
available to calculate a WLA load reduction for the NCDOT as a load or concentration.
Therefore, the percent reduction for the NCDOT was assumed to be the same as the non-point
source load reduction.

3.5.2 Load Allocation (LA)

All fecal coliform loadings from nonpoint sources such as non-MS4 urban land, agriculture land,
and forestlands are reported as LAs. The estimated contributions of fecal coliform from the
nonpoint sources are presented in Table 3.8. The estimated percent reduction from nonpoint
sources is 75.2%, as shown in Table 3.9.

Table 3.8 – Estimated TMDL and Load Allocation for Fecal Coliform for the White Oak River
Waterbody Pollutant Existing
Load WLA LA Explicit
MOS1 TMDL
White Oak River 20-
(18)a1, 20-(18)a2,
20-(18)b, 20-(18)c1,
20-(18)c3, 20-(18)c5,
20-(18)c6, 20-(18)c7,
20-(18)c8, 20-(18)d,
20-(18)e2, 20-(18)e3
Fecal
Coliform
(cfu/day)
5.40E+11 7.32E+9 1.09E+11 1.77E+10 1.34E+11
Note: The Margin of safety is included in the TMDL by lowering the Fecal Coliform standard from 43 to 38 cfu/100 ml. The MOS shown here is
the difference between the TMDL calculated at both standards.

Table 3.9 – Estimated Load Reduction by Source for Fecal Coliform (shown in cfu/day) for the White Oak River
WLA LA
Existing Load (cfu/day) 7.32E+9 5.40E+11
Load Allocation (cfu/day) 7.32E+9 1.09E+11
Percent Reduction 0% 75.2%

White Oak River Fecal Coliform TMDL
________________________________________________________________________

29

3.6 Critical Condition and Seasonal Variation

Critical conditions are considered in the load duration curve analysis by using an extended
period of stream flow and water quality data, and by examining the flows (percent flow
exceeded) where the existing loads exceed the target line.

Seasonal variation is considered in the development of the TMDLs, because allocation applies
to all seasons. According to the load duration curve (Figure 3.4), the existing load violation for
fecal coliform occurred at all flow conditions throughout the year. Therefore, both dry and wet
weather is critical for fecal coliform.

3.7 Margin of Safety

A Margin of Safety (MOS) is required as part of a TMDL in recognition of many uncertainties in
the understanding and simulation of water quality in natural systems. For example, knowledge
is incomplete regarding the exact nature and magnitude of pollutant loads from various sources
and the specific impacts of those pollutants on the chemical and biological quality of complex,
natural water bodies. The MOS is intended to account for such uncertainties in a manner that
is conservative from the standpoint of environmental protection.

As a conservative estimate in the TMDL calculation, an explicit MOS was included. The explicit
MOS was achieved by lowering the targeted 90th percentiles to 38 MPN/100 ml. This is an
11.6% reduction from the standard 90th percentile of 43 MPN/100 ml. The MOS, in terms of
load, was calculated by subtracting the TMDL loading needed to meet a 90th percentile target of
38 from the model loading needed to meet a target of 43. These loads are shown in the Table
3.8.

3.8 Monitoring

Monitoring should continue on a monthly interval at the existing ambient monitoring station, as
well as DEH stations. The continued monitoring of fecal coliform will allow for the evaluation of
progress towards the goal of reaching water quality standards by comparing the instream data
to the TMDL target.

4 TMDL IMPLEMENTATION PLAN

An implementation plan is not included in this TMDL. Local stakeholder groups, governments,
and agencies are encouraged to develop an implementation plan and utilize funding sources for
water quality improvement projects targeted at BMP construction and public outreach. Some
potential funding sources include the North Carolina Clean Water Management Trust Fund, and
White Oak River Fecal Coliform TMDL
________________________________________________________________________

30

Section 319 and 205j funds. Individual land owners may apply for the Community Conservation
Assistance Program and Agriculture Cost Share Program to improve the condition of their
property. The upcoming DEH Sanitary Survey for the D-3 shellfish growing area will help further
identify current sources of bacteria and drainage pathways that allow bacteria to enter the
White Oak River.

5 PUBLIC PARTICIPATION

A draft of the TMDL was publicly noticed through various means. The TMDL was public noticed
on the NC Modeling and TMDL website on July 12, 2010. The TMDL was also public noticed on
July 14, 2010 through the North Carolina Water Resources Research Institute email list-serve. In
Addition, the TMDL was public noticed in the relevant counties through a local newspaper
(Carteret County News-Times) on July 16, 2010. Copies of the public notices are included in
Appendix C.

Finally, the TMDL was available on DWQ’s website (http://portal.ncdenr.org/web/wq/ps/mtu)
during the comment period. The public comment period lasted until August 16, 2010.

DWQ received one public comment on the White Oak River TMDL. Summaries of the comments
and DWQ responses are included in Appendix D.

6 FURTHER INFORMATION

Further information concerning North Carolina’s TMDL program can be found on the Internet at
the Division of Water Quality website:
http://portal.ncdenr.org/web/wq/ps/mtu

Technical questions regarding this TMDL should be directed to the following members of the
DWQ Modeling/TMDL Unit:

Andy Painter
e-mail: [e-mail]

Kathy Stecker
e-mail: [e-mail]

White Oak River Fecal Coliform TMDL
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31

7 REFERENCES

NCAD. 2003. NC Administration Code.

NC DEH, 2006. Report of Sanitary Survey, Growing Area D-3, White Oak River Area. NC Division
of Environmental Health Shellfish Sanitation and Recreational Water Quality. November, 2006.

NCDENR, 2009. Total Maximum Daily Loads for Fecal Coliform for Embayments in Southeast
White Oak River, North Carolina. Final Report – March, 2009. Raleigh, NC.

NC DWQ, 2003. Animal Operations – GIS Data Layer. NC Center for
Geographic Information & Analysis, Raleigh, North Carolina. Website:
http://www.nconemap.com/Default.aspx?tabid=286

NCCF, 2009. White Oak River Shellfish Restoration Project. North Carolina Coastal Federation.
March 2009. Retrieved from:
http://www.nccoast.org/central/PDF/White%20Oak%20Final%20Report.pdf

NOAA, 2010. Tides Online. National Ocean Service. Website: http://co-ops.nos.noaa.gov/

NSSP, 2007. National Shellfish Sanitation Program Guide for the control of Molluscan Shellfish
2007, Section IV, Chapter II (Bacteriological Standards). US Food and Drug Administration, 2007.
Website: http://www.fda.gov/Food/FoodSafety/Product-
SpecificInformation/Seafood/FederalStatePrograms/NationalShellfishSanitationProgram/UCM0
53698

Tetra Tech, 2008. Shellfish Bed TMDL Development Protocol for White Oak River, NC - Draft.
Tetra Tech, Inc. March 31, 2008.

USDA (2007). 2002 Census of Agriculture (North Carolina State and County Data). U.S.
Department of Agriculture.

USEPA. 2002. Wayland, Robert, H. and James A. Hanlon. "Establishing Total Maximum Daily
Load (TMDL) Wasteload Allocations (WLAs) for Storm Water Sources and NPDES Permit
Requirements Based on Those WLAs". Memo to Water Division Directors Regions 1-10. United
States Environmental Protection Agency, Washington, D.C. 22 November 2002.

US EPA, Office of Water. 2000. Bacteria Indicator Tool User's Guide. EPA-823-B-01-003.

US Department of Commerce, United States Census. 2000. Washington DC: US Bureau of the
Census.

White Oak River Fecal Coliform TMDL
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32

Appendix A: 2005-2009 Division of Environmental Health Fecal Coliform Data

Station #
Samples Median Geometric
Mean
90th
Percentile
17 32 13.0 15.5 70.0
18 125 7.8 10.1 70.0
19 30 11.0 9.1 33.0
20 30 4.5 5.2 17.6
21 30 5.7 6.8 27.6
24 54 4.5 5.4 30.0
25 30 4.3 3.7 11.1
26 30 4.5 4.6 13.4
36 31 9.3 8.3 33.0
45 30 4.3 4.0 13.0
46 30 4.5 4.2 13.1
47 30 4.3 4.1 13.0
49 30 4.3 4.1 8.3
50 30 3.3 3.7 11.0
51 52 4.5 7.5 47.4
52 30 4.0 3.5 7.9
53 30 2.0 3.1 8.3
56 30 3.3 4.3 11.6
57 30 4.0 3.7 9.6
60 130 12.0 13.2 79.0

A station location map is located on the following page.

White Oak River Fecal Coliform TMDL
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33

White Oak River Fecal Coliform TMDL
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34

Appendix B: TMDL Data

Table B.1. Water Quality and Flow Data for the White Oak River at DWQ Ambient
Station P6400000

Date
Result
(cfu/100
mL)
Flow
(cfs) Remark1
1/13/2000 36 242.5
2/22/2000 10 252.5 K
3/14/2000 36 155
4/13/2000 64 165
5/24/2000 73 365
6/20/2000 500 145
7/27/2000 110 872.5
8/31/2000 490 415
9/14/2000 120 125
10/4/2000 27 202.5
11/28/2000 900 255
12/12/2000 54 267.5
2/26/2001 45 262.5
5/17/2001 55 132.5 Q
6/19/2001 41 410 Q
7/16/2001 16 72.5 Q
8/29/2001 33 95 Q
9/25/2001 92 65 B4,Q
10/31/2001 10 35 Q
11/29/2001 38 47.5 Q
1/8/2002 30 165 Q
2/14/2002 33 160 Q1
4/1/2002 150 717.5 Q1,B1
4/29/2002 110 120 Q1
5/21/2002 40 57.5 Q1
6/20/2002 27 52.5 Q1
7/9/2002 35 40 Q1
8/8/2002 52 37.5 Q1
9/26/2002 87 67.5 Q1
10/30/2002 770 102.5 Q1
11/21/2002 16 172.5 Q1
12/17/2002 26 145 Q1
1/30/2003 5 125 Q1
Date
Result
(cfu/100
mL)
Flow
(cfs) Remark1
2/18/2003 46 702.5 Q1
3/20/2003 140 1127.5 Q1
4/23/2003 35 225 Q1
5/29/2003 140 1550 Q1
6/25/2003 23 335 Q1
8/4/2003 19 225 Q1
8/18/2003 160 1362.5 Q1
9/22/2003 120 182.5 Q1
10/27/2003 110 240 Q1
11/17/2003 38 212.5 Q1
12/17/2003 160 1055 Q1
1/22/2004 28 145 Q1
2/24/2004 44 357.5 Q1
3/17/2004 80 320 Q1
4/21/2004 16 160 Q1
5/24/2004 24 67.5 Q1
6/15/2004 42 155 Q1
7/22/2004 33 47.5 Q1
9/20/2004 210 435 B4,Q1
10/21/2004 23 152.5 Q1
11/16/2004 29 250 Q1
12/15/2004 310 122.5 B4,Q1
1/31/2005 97 370 Q1
2/23/2005 9 120 Q1
3/29/2005 150 775 Q1
4/25/2005 52 75 Q1
5/17/2005 30 252.5 Q1
6/28/2005 42 105 Q1
7/25/2005 71 80 B4,Q1
8/30/2005 93 80 Q1
10/25/2005 110 757.5 Q1
11/17/2005 37 107.5 Q1
3/23/2006 17 142.5 Q1
White Oak River Fecal Coliform TMDL
________________________________________________________________________
35
Date
Result
(cfu/100
mL)
Flow
(cfs) Remark1
4/19/2006 29 90 Q1
5/31/2006 22 57.5 Q1
7/19/2006 32 122.5 Q1
8/29/2006 27 157.5 Q1
9/20/2006 67 1165 Q1
10/18/2006 44 170 Q1
12/5/2006 62 347.5 B4,Q1
1/3/2007 120 475 Q1
1/23/2007 110 952.5 Q1
3/1/2007 52 220 Q1
4/3/2007 27 120 Q1
4/30/2007 34 77.5 Q1
5/31/2007 120 60 Q1
6/28/2007 23 32.5 Q1
7/24/2007 200 25 Q1
8/22/2007 80 70 Q1
9/19/2007 18 52.5 Q1
10/31/2007 46 75 Q1
12/5/2007 10 32.5 Q1
12/18/2007 900 42.5 Q1
1/31/2008 16 65 Q1
3/25/2008 34 90 Q1
5/1/2008 31 180 B1,Q1
5/28/2008 13 62.5 Q1
6/19/2008 97 42.5 Q1
7/31/2008 90 40 B4,Q1
8/26/2008 35 35 Q1
9/24/2008 30 60 Q1
10/23/2008 19 47.5 Q1
11/18/2008 42 80 Q1
12/10/2008 5 72.5 Q1
2/3/2009 29 130 Q1
2/23/2009 40 127.5 Q1
3/18/2009 48 202.5 Q1
4/15/2009 120 1395 Q1
1Fecal Coliform Remark Codes:

B1 Countable membranes with less than
20 colonies. Reported value is estimated
or is a total of the counts on
all filters reported per 100 ml.

B4 Filters have counts of both >60 or 80
and <20. Reported value is a total of the
counts from all countable
filters reported per 100 ml.

K Actual value is known to be less than
value given

L Actual value is known to be greater
than value given

Q Holding time exceeded.

Q1 Holding time exceeded. Holding time
exceeded prior to receipt by lab.

(The TMDL margin of safety should
account for any uncertainty caused by
the holding time exceedance.)
White Oak River Fecal Coliform TMDL
________________________________________________________________________
36

Figure B.1 - Daily average flow (cfs) measured at New River USGS Gage 2093000 with 2.5
drainage area ratio applied.

Table B.2. Estimation of Load Reduction Required for Fecal Coliform in the White Oak
River at DWQ Ambient Station P6400000.

% Flow
Exceeded
Flow (cfs) Actual Load Allowable
Load
(cfu/day)
Reduction
Needed
0.1 218.75 8.80117E+11 2.0346E+11
0.15 197.5 8.25678E+11 1.8369E+11
0.2 177.5 7.74607E+11 1.6509E+11
0.25 168.75 7.26694E+11 1.5695E+11
0.3 166.25 6.81745E+11 1.5463E+11
0.35 156.25 6.39576E+11 1.4533E+11
0.4 153.75 6.00015E+11 1.43E+11
0.45 153.75 5.62902E+11 1.43E+11
0.5 152.5 5.28084E+11 1.4184E+11
0.55 152.5 4.9542E+11 1.4184E+11
0.6 147.5 4.64776E+11 1.3719E+11
0.65 138.75 4.36027E+11 1.2905E+11
0.7 138.75 4.09057E+11 1.2905E+11
0.75 121.25 3.83755E+11 1.1277E+11
0.8 106.25 3.60018E+11 9.8822E+10
0.85 90 3.3775E+11 8.3708E+10
0.9 83.75 3.16858E+11 7.7895E+10
0
2000
4000
6000
8000
10000
12000
1/
1
/
2
0
0
0
7/
1
/
2
0
0
0
1/
1
/
2
0
0
1
7/
1
/
2
0
0
1
1/
1
/
2
0
0
2
7/
1
/
2
0
0
2
1/
1
/
2
0
0
3
7/
1
/
2
0
0
3
1/
1
/
2
0
0
4
7/
1
/
2
0
0
4
1/
1
/
2
0
0
5
7/
1
/
2
0
0
5
1/
1
/
2
0
0
6
7/
1
/
2
0
0
6
1/
1
/
2
0
0
7
7/
1
/
2
0
0
7
1/
1
/
2
0
0
8
7/
1
/
2
0
0
8
1/
1
/
2
0
0
9
Av
e
r
a
g
e

D
a
i
l
y

F
l
o
w

(
c
f
s
)
Date
White Oak River Fecal Coliform TMDL
________________________________________________________________________
37
0.95 73.75 2.97259E+11 6.8594E+10
Numeric
Standard
Statistical
Measure

38 Average 5.40019E+11 1.3422E+11 75.15%
White Oak River Fecal Coliform TMDL
________________________________________________________________________
38
Appendix C: Public Notification of TMDL for Fecal Coliform for the White Oak River

The TMDL public comment period was announced on the NC Modeling and TMDL
website on 7/12/10, on the WRRI listserv on 7/14/10, and the Carteret County News-
Times on 7/16/10.

• Notice on the Modeling and TMDL Website:
http://portal.ncdenr.org/web/wq/ps/mtu

7/12/10 The Lockwood Folly and White Oak River Public Review Draft TMDLs are
available for review. The comment period extends through August 13, and August 16 for
each TMDL respectively. Comment submittal instructions are available with the above
links

• WRRI listserv email received regarding public comment period:

From: [e-mail]
To: <[e-mail]>
Subject: Now available for public review - DRAFT Total Maximum Daily
Loadfor the Shellfish Harvesting Areas in the White Oak River
Message-ID: <[e-mail]>

Now Available for Public Comment

This draft TMDL report was prepared as a requirement of the Federal Water
Pollution Control Act, Section 303(d). Interested parties are invited to
comment on the draft TMDL report by August 16, 2010. Comments concerning
the report should be directed to Andy Painter at [e-mail]
or write to:

Andy Painter
NC Division of Water Quality
Planning Section
1617 Mail Service Center
Raleigh, NC 27699

If you wish to obtain a hard copy of the TMDL, please contact Linda Chavis
at [phone] or email at [e-mail]

The draft TMDL can also be downloaded from the following website:
http://portal.ncdenr.org/web/wq/ps/mtu/tmdl/tmdls

------------------------------

Date: Wed, 14 Jul 2010 13:54:05 -0400
White Oak River Fecal Coliform TMDL
________________________________________________________________________

White Oak River Fecal Coliform TMDL
________________________________________________________________________
39

________________________________________________________________________

White Oak River Fecal Coliform TMDL
________________________________________________________________________
40
Appendix D: Public Comments

Public Comment White Oak River Fecal Coliform Bacteria TMDL Responsiveness
Summary

August 2010

The public comment period extended from July 12, 2010 through August 16, 2010.
Comments were received from the North Carolina Department of Transportation.
These comments with the NC Division of Water Quality responses are provided in the
Responsiveness Summary presented below.

1) One comment stated that waterbody ID 20-(18)c4 was already addressed in the
Southeast White Oak River Fecal Coliform TMDL approved by EPA on April 10, 2009, and
suggested that this waterbody ID should be removed from this TMDL to avoid confusion
and conflicting load reduction calculations.

Response: DWQ will remove waterbody ID 20-(18)c4 from this TMDL document.

2) One comment stated that the drainage area for station P6400000 is 203 mi2 and that
for the New River USGS gauging station 2093000 is 81 mi2 and the ratio for these two
drainage areas should be 2.5.

Response: DWQ has revised the drainage area ratio in the text and TMDL calculations to
2.5. This change resulted in altering the flows at the percent flow exceedance intervals in
the TMDL calculation and caused an increase in the percent reduction needed from 73.5
to 75.2 percent.

3) One comment stated that the report appeared to assign NCDOT a load allocation as
opposed to a wasteload allocation (WLA) which is contrary to EPA guidance regarding
allocations to NPDES permittees.

Response: Because of the nature of drainage from roads and highways, the percent
reduction for the NCDOT was assumed to be the same as the nonpoint source load
allocation. The NCDOT is included in each NPDES table and WLA section in the TMDL,
with the exception of table 3.6 which has been renamed “Existing WWTF Load
Contributions” from “Existing NPDES Load Contributions.”

4)

A) One comment stated that it is unclear which sources DWQ considers as contributing
to the water quality impairment. It does not appear that many of the potential sources
identified by Shellfish Sanitation were analyzed in the report and the commenter
questions why reductions are not called for the sources identified in Figure 2.1.
White Oak River Fecal Coliform TMDL
________________________________________________________________________
41

Response: Reductions for the potential nonpoint sources mentioned in section 2.1 of the
report need a reduction of 75.2 percent as stated in the LA percent reduction. Nonpoint
sources are generally aggregated into one load allocation in TMDLs. The Shellfish
Sanitation report contains information on local sources, and an excellent resource for
where to implement BMPs.

B) The commenter states that grazing farm animals were the only identified potential
source whose numbers were quantified, and that illicit connections, SSOs, and swine
operations are not believed to be significant load contributors. The commenter
questions whether a 73.5 % reduction in loads from grazing farm animals will be
sufficient to restore water to standards.

Response: The required reduction applies to all nonpoint sources as defined in the first
paragraph in section 2.1. Grazing animals are a potential source of bacteria, thus
information on the quantity of animals is included in the nonpoint source assessment.
The text states in Section 2.2 that five SSO violations were found in the watershed during
the years 2000-2009. One permit violation for a swine operation was found, which did
not result in a release of waste. The following information has been included in Section
2.1 of the text: Two potential septic system failures and one illicit connection were
identified in the 2006 sanitary survey.

C) The commenter stated that the report calls for 73.5% reduction from nonpoint source
in the upper watershed (above station P6400000) a 0% reduction from NPDES
permittees and no reduction required for point or nonpoint sources in the lower
watershed.

Response: The percent reduction applies to all listed waterbody IDs identified in the
TMDL.

5) The commenter states that they were not able to replicate the data presented in
Figure 3.4 and 3.5 because it was not clear how the 90th percentile running thirty sample
population were plotted against measured flow values. The commenter also stated it
would be useful to see flow values presented in table A.1 as well as fecal coliform
concentrations presented in table A.2.

Response: DWQ will provide the load duration curve spreadsheet calculations to
interested parties upon request, and text had been added in section 3.4 to clarify the
figures. Table A.1 has been revised to show flow values with each sample date.

6) The commenter requests that the data used to determine the use support rating for
the impaired shellfish waters be summarized in Section 1.4.
White Oak River Fecal Coliform TMDL
________________________________________________________________________
42
Response: Data are not used to determine use support for shellfish waters. Any shellfish
water not fully open for harvesting is considered impaired. The data collected by the NC
DEH have been summarized in Appendix A of the TMDL.