Lockwoods_FC_TMDL_20100907_Final_to_EPA_Approved

Total Maximum Daily Loads of Fecal Coliform for the
Shellfish Harvesting Areas in the Lockwoods
Folly River, Lumber River Basin, Brunswick
County, North Carolina
[Waterbody ID 15-25-1-(16)a, Waterbody ID 15-25-1-(16)b, Waterbody ID 15-25-1-(16)c,
Waterbody ID 15-25-1-(16)d, Waterbody ID 15-25-1-18-(2), Waterbody ID 15-25-1-19,
Waterbody ID 15-25-1-20, Waterbody ID 15-25-1-21]

September 2010
(EPA Approved)

White Oak River Basin

Prepared by:
North Carolina Department of Environment and Natural Resources
Division of Water Quality 1617 Mail Service Center
Raleigh, NC 27699-1617
With support from:
North Carolina Coastal Federation 3609 Highway 24 Newport, NC 28570
Stantec Consulting Services, Inc. 801 Jones Franklin Road
Suite 300 Raleigh, NC 27606

Lumber River Basin
Lockwoods Folly River Fecal Coliform TMDL
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Table of Contents
Table of Contents ........................................................................................................................... i List of Abbreviations ...................................................................................................................... ii 
List of Tables ................................................................................................................................ iii 
List of Figures .............................................................................................................................. iii Summary Page ............................................................................................................................ iv 
Executive Summary .................................................................................................................... viii 1.0 Introduction ............................................................................................................................ 1 
1.1 TMDL Components ........................................................................................................ 2 
1.2 Documentation of Impairment ........................................................................................ 3 1.3 Watershed Description ................................................................................................... 4 
1.3.1 Land Use/Land Cover ............................................................................................. 6 1.3.2 Soils ......................................................................................................................... 8 
1.4 Water Quality Characterization ....................................................................................... 8 2.0 Source Assessment ............................................................................................................. 12 2.1 Point Source Assessment ............................................................................................ 12 
2.1.1 NPDES Wastewater Permits ................................................................................. 12 2.1.2 NPDES Stormwater Permits .................................................................................. 12 
2.2 Nonpoint Source Assessment ...................................................................................... 13 3.0 Total Maximum Daily Loads and Load Allocation ................................................................ 14 
3.1 Modeling Approach ....................................................................................................... 14 
3.1.1 Watershed Model Description ............................................................................... 14 3.1.2 Tidal Prism Description ......................................................................................... 14 
3.1.3 Model Setup .......................................................................................................... 15 3.1.4 Meteorological Data .............................................................................................. 17 
3.2 Model Calibration and Validation .................................................................................. 18 
3.2.1 Watershed Model Calibration ................................................................................ 18 3.2.2 Tidal Prism Model Calibration ............................................................................... 21 
3.3 TMDL Calculation ......................................................................................................... 25 
3.4 Critical Condition .......................................................................................................... 26 3.5 Seasonality ................................................................................................................... 26 
3.6 TMDL Loading Cap ...................................................................................................... 28 3.7 Wasteload Allocation .................................................................................................... 28 
3.8 Load Allocation ............................................................................................................. 29 
3.9 Margin of Safety ........................................................................................................... 29 3.10 Summary of Total Maximum Daily Load ....................................................................... 29 
4.0 TMDL Implementation Plan ................................................................................................. 30 5.0 Stream Monitoring ................................................................................................................ 31 
6.0 Future Efforts ....................................................................................................................... 31 7.0 Public Participation .............................................................................................................. 31 8.0 Further Information .............................................................................................................. 33 
References .................................................................................................................................. 34 Appendix A. Observed Time Series Plots and Water Quality Data............................................. 37 
Appendix B. Tidal Prism Model Segmentation ............................................................................ 57 Appendix C. Nonpoint Source Assessment ................................................................................ 58 
Appendix D. Model Results of Median and 90th Percentile ......................................................... 64 
Appendix E. TMDL Model Documentation ................................................................................ E-1 Appendix F. Public Notice ......................................................................................................... F-1 
Appendix G: Public Comment ................................................................................................... G-1 
Appendix H. Public Education and Outreach Materials ............................................................ H-1 
Lockwoods Folly River Fecal Coliform TMDL
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List of Abbreviations
BMP Best Management Practice
CFR Code of Federal Regulations
CWA Clean Water Act
DEHSS Division of Environmental Health Shellfish Sanitation
DEM Digital Elevation Model
EMC Event Mean Concentration
EPA Environmental Protection Agency
FA Future Allocation
GIS Geographic Information System
GUI Graphic User Interface
HEC-HMS Hydrologic Engineering Center-Hydrologic Modeling System
HUC Hydrologic Unit Code
ICWW Intracoastal Waterway
LA Load Allocation
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
NCAC North Carolina Administrative Code
NCCF North Carolina Coastal Federation
NCDEH North Carolina Department of Environmental Health
NCDENR North Carolina Department of Environment and Natural Resources
NCDOT North Carolina Department of Transportation
NCDWQ North Carolina Division of Water Quality
NOAA National Oceanic and Atmospheric Administration
NPDES National Pollutant Discharge Elimination System
NSSP National Shellfish Sanitation Program
SA Class SA waterbody suitable for commercial shellfishing and all other tidal
saltwater use
TMDL Total Maximum Daily Load
TPWQM Tidal Prism Water Quality Model
USGS United States Geological Survey
WLA Wasteload Allocation
WQLS Water Quality Limited Segment
WRRI Water Resources Research Institute
Lockwoods Folly River Fecal Coliform TMDL
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List of Tables
Table 1. Land use distribution in the Lockwoods Folly River watershed ...................................... 6 Table 2. Summary statistics of observation data (2004 to October 2009) .................................... 9 
Table 3. Summary statistics of observation data (2004 to December 2007) .............................. 10 
Table 4. Active NPDES industrial stormwater permits in the watershed .................................... 12 Table 5. Estimated distribution of direct fecal coliform nonpoint source loads to the watershed 13 
Table 6. Comparison of observed and modeled runoff ............................................................... 19 Table 7. Comparison of total seasonal discharge (inches) ......................................................... 20 
Table 8. Selected EMC Values (cfu/100ml) ................................................................................ 21 
Table 9. TMDL summary ............................................................................................................ 26 Table 10. Wasteload allocation summary ................................................................................... 28 
Table A1. Observed data at all monitoring stations in the Lockwoods Folly estuary (2004-2009)42 Table B1. Geometry information of the Lockwoods Folly Estuary used for the TPWQM ............ 57 
Table C1. Wildlife habitat and densities ...................................................................................... 59 Table C2. Wildlife fecal coliform production rates ....................................................................... 59 Table C3. Livestock fecal coliform production rates ................................................................... 60 

List of Figures Figure 1. Vicinity and watershed map ........................................................................................... 5 
Figure 2. Current land use ............................................................................................................ 7 
Figure 3. Shellfish Sanitation monitoring station locations and TPWQM model segments ........ 11 Figure 4. Watershed model subwatersheds ............................................................................... 16 
Figure 5. Average monthly precipitation (2004-2009) for the three precipitation gages ............. 17 Figure 6. Hydrology model calibration ........................................................................................ 18 
Figure 7. Hydrology model validation .......................................................................................... 19 
Figure 8. Modeled fecal coliform concentration for model segment M0S2 and observed fecal coliform concentration at Site 7A ......................................................................................... 23 
Figure 9. Modeled 90th percentile fecal coliform concentration for model segment M0S2 and observed 90th percentile fecal coliform concentration at Site 7A ......................................... 23 
Figure 10. Modeled fecal coliform concentration for model segment M0S2 and observed fecal
coliform concentration at Site 8 ........................................................................................... 24 Figure 11. Modeled 90th percentile fecal coliform concentration for model segment M0S2 and
observed 90th percentile fecal coliform concentration at Site 8 ........................................... 24 Figure 12. Distribution of monthly average fecal coliform concentration at Site 7A (log scale) .. 27 
Figure 13. Distribution of monthly average fecal coliform concentration at Site 8 (log scale) ..... 27 
Figure A1. Time series plot of fecal coliform observations at Site 5A ......................................... 37 Figure A2. Time series plot of fecal coliform observations at Site 6A ......................................... 38 
Figure A3. Time series plot of fecal coliform observations at Site 7 ........................................... 38 Figure A4. Time series plot of fecal coliform observations at Site 7A ......................................... 39 
Figure A5. Time series plot of fecal coliform observations at Site 8 ........................................... 39 
Figure A6. Time series plot of fecal coliform observations at Site 10 ......................................... 40 Figure A7. Time series plot of fecal coliform observations at Site 13 ......................................... 40 
Figure A8. Time series plot of fecal coliform observations at Site 14A ....................................... 41 Figure A9. Time series plot of fecal coliform observations at Site 14B ....................................... 41 
Figure D1. Modeled current and TMDL 90th percentile ............................................................... 64 
Figure D2. Modeled current and TMDL median .......................................................................... 65 

Lockwoods Folly River Fecal Coliform TMDL
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Summary Page
1. 303 (d) Listed Waterbody Information
State: North Carolina
County: Brunswick
Major River Basin: Lumber River Basin
Watershed: Lockwoods Folly River (030402070200)
Impaired Waterbody (2008 303(d) List):
Waterbody Name - (ID) Description Water Quality Classification Acres
Lockwoods Folly River -
(15-25-1-(16)a)
From Brunswick County SR 1200 to a line crossing Lockwood
Folly River 520 meters north of Myrtle Point of the east shore to a point of the west shore 704 meters north of Mullet Creek SA, HQW 123.6
Lockwoods Folly River - (15-25-1-(16)b)
From a line crossing Lockwood Folly River 520 meters north of
Myrtle Point of the east shore to a point of the west shore 704 meters north of Mullet Creek to a line crossing Lockwood Folly River 146 meters north of Genoes Point on the east shore to a point on the west shore 777 meters south of Mullet Creek SA, HQW 275.6
Lockwoods Folly River -
(15-25-1-(16)c)
From a line crossing Lockwood Folly River 146 meters north of Genoes Point on the east shore to a point on the west shore
777 meters south of Mullet Creek to a line crossing Lockwoods Folly River 628 meters south of Genoes point on the east shore SA, HQW 207.0
Lockwoods Folly River - (15-25-1-(16)d)
From a line crossing Lockwood Folly River 628 meters south of Genoes Point on the east shore to Gores Landing on the east shore to ICWW SA, HQW 53.1
Mill Creek - (15-25-1-18-(2)) From Brunswick County SR 1112 to Lockwoods Folly River SA, HQW 2.0
Montgomery Slough - (15-25v) From ICWW west of Lockwoods Folly Inlet extending eastward (2.4 Miles) SA, HQW 2.3
Mullet Creek - (15-25-1-19) From source to Lockwoods Folly River SA, HQW 5.7
Intracoastal Waterway - (15-25u) From a line crossing ICWW south of SR 1112 to Cape Fear River Basin SA, HQW 403.5
Intracoastal Waterway - (15-25t1) From a line across the ICWW 2030 meters west of NC 130 bridge to a line crossing ICWW south of SR1112 SA, HQW 292.8
Spring Creek - (15-25-1-21) From source to Lockwoods Folly River SA, HQW 2.4
Lockwoods Creek - (15-25-1-20) From source to Lockwoods Folly River SA, HQW 0.2

Constituent(s) of Concern: Fecal Coliform Bacteria
Designated Uses: aquatic life, shellfish harvesting

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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.”
2. TMDL Development
Development Tools (Analysis/Modeling):
The linked watershed and Tidal Prism modeling approach was used to estimate current fecal coliform load from the watershed and to simulate fecal coliform concentrations in the estuary. The
long-term model results were used to establish allowable loads for the restricted shellfish harvesting areas. Since long-term model simulation is used to establish TMDLs, it accounts for the seasonal
variability and critical conditions, which thereby represents the hydrology, hydrodynamics, and
water quality condition of the estuary. The selected watershed model calculated the watershed load to the Lockwoods Folly estuary which includes loads from Mullet Creek, Spring Creek, Mill Creek,
Lockwoods Creek, and the Lockwoods Folly River up to Brunswick County SR 1200. Therefore, the load reduction calculated for the estuary is applied to all of the aforementioned segments. A TMDL
was not developed for the Intracoastal Waterway (ICWW) and Montgomery Slough because the
hydrodynamics are not conducive to using the linked watershed and Tidal Prism modeling approach. The TMDL load reduction does not apply to the ICWW or Montgomery Slough. These
areas will instead be addressed in the TMDL implementation strategies.
Critical Conditions:
The 90th percentile concentration is the concentration exceeded only 10% of the time. Since the
model simulation period spans five years (2004-2009), the critical condition is implicitly included in
the value of the 90th percentile of model results. Given the length of the monitoring record and model simulation 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 continuous simulation. In general, high fecal coliform levels occur throughout the year in the estuary. The average monthly concentrations are relatively similar between months. The
highest concentrations occur in April while the lowest concentrations occur in February and the late
spring months. The model simulation spans five years. As a result, the seasonal variability is directly included in the model simulation.
3. TMDL Allocation Summary
Model results show that the 90th percentile component of the standard, rather than the median component, requires the highest reduction. The allocation is established based on the 90th
percentile load.
Lockwoods Folly River Fecal Coliform TMDL
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Waterbody Pollutant Existing Load WLA LA MOS TMDL Reduction Needed*
Lockwoods
Folly River (15-
25-1-(16)c) Lockwoods Folly River (15-25-1-
(16)a), Lockwoods Folly River (15-25-1-(16)b), Lockwoods Folly River (15-25-1-(16)d), Mill Creek,
Mullet Creek, Spring Creek, Lockwoods Creek
Fecal coliform (counts/day) 6.910E+12 2.097E+11 7.855E+11 1.106E+11 1.106E+12 84%
*MOS not included. A reduction of 86% is required when the MOS is taken into account. WLA = wasteload allocation, LA = load allocation, MOS = margin of safety (10%) LA = TMDL - WLA - MOS

4. Contributing Municipalities TMDL Allocation Summary: N/A
5. Contributing NPDES Facilities TMDL Allocation Summary: NCDOT stormwater
Pollutant NCDOT Existing Load WLA Reduction Needed
Fecal coliform (counts/day) 4.462E+11 2.097E+11 53%

6. Public Notice Information:
Summary: A draft of the TMDL was publicly noticed through various
means. The TMDL was public noticed in the local newspaper (City of Wilmington Star News) on July 14. The
TMDL was also public noticed on July 14, 2010 through the North Carolina Water Resources Research Institute (WRRI)
email listserve, to the DWQ mailing list of interested parties,
and on the DWQ TMDL website. A press release was sent out on July 13 and an article was published in the Star
News on July 21, 2010 (Appendix F). Finally, the TMDL was available on DWQ’s website
http://h2o.enr.state.nc.us/tmdl/ during the comment period. The public comment period lasted from July 13, 2010 until August 13, 2010.
Did notification contain specific
mention of TMDL Proposal?
Yes
Were comments received from the public? Yes
Lockwoods Folly River Fecal Coliform TMDL
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Was a responsiveness summary
prepared?
Yes, see Appendix G of the TMDL report
7. Public Notice Date: July 13, 2010
8. Submittal Date: August 20, 2010
9. Establishment Date:
10. EPA Lead on TMDL (EPA or blank):
11. DOT a Significant Contribution (Yes or blank):
12. Endangered Species (Yes or blank):
13. MS4s Contributions to Impairment (Yes or blank):
14. TMDL Considers Point Source, Nonpoint Source, or both: Point Source (NCDOT
stormwater) and Nonpoint Source
Lockwoods Folly River Fecal Coliform TMDL
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Executive Summary
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 identify and list waters, known as
water quality limited segments (WQLSs), in which current required controls of a specified substance
are inadequate to achieve water quality standards. For each WQLS, the State is to either establish a Total Maximum Daily Load (TMDL) of the specified substance that the waterbody can receive
without violating water quality standards, or demonstrate that water quality standards are being met.
The Lockwoods Folly River is located in south central Brunswick County, south of Wilmington, NC
within the Lumber River Basin (NC subbasin 03-07-59, HUC 030402070200). The River, estuary
and their tributaries are located within the A-3 shellfish harvesting area, as designated by the North Carolina Division of Environmental Health (NCDEH). The Lockwoods Folly River and the upriver
portion of the estuary are Prohibited for shellfish harvesting due to excessive levels of fecal coliform bacteria. The two downstream portions of the estuary are Conditionally Approved Open and
Conditionally Approved Closed. The tributaries of Mill Creek, Mullet Creek, Lockwoods Creek and portions of Montgomery Slough and the Intracoastal Waterway are also Prohibited. Spring Creek is Conditionally Approved Open for shellfish harvesting. All of these segments are listed on the 2008
303(d) list as impaired due to fecal coliform. This document addresses the fecal coliform impairment of these restricted shellfish harvesting areas within the Lockwoods Folly River watershed as listed
in the following table.
Waterbody Name - (ID) Description Water Quality Classification Acres
Lockwoods Folly River -
(15-25-1-(16)a)
From Brunswick County SR 1200 to a line crossing Lockwood Folly River 520 meters north of Myrtle Point of the east shore to
a point of the west shore 704 meters north of Mullet Creek SA, HQW 123.6
Lockwoods Folly River - (15-25-1-(16)b)
From a line crossing Lockwood Folly River 520 meters north of Myrtle Point of the east shore to a point of the west shore 704 meters north of Mullet Creek to a line crossing Lockwood Folly River 146 meters north of Genoes Point on the east shore to a point on the west shore 777 meters south of Mullet Creek SA, HQW 275.6
Lockwoods Folly River - (15-25-1-(16)c)
From a line crossing Lockwood Folly River 146 meters north of Genoes Point on the east shore to a point on the west shore 777 meters south of Mullet Creek to a line crossing Lockwoods Folly River 628 meters south of Genoes point on the east shore SA, HQW 207.0
Lockwoods Folly River - (15-25-1-(16)d)
From a line crossing Lockwood Folly River 628 meters south of Genoes Point on the east shore to Gores Landing on the east shore to ICWW SA, HQW 53.1
Mill Creek - (15-25-1-18-(2)) From Brunswick County SR 1112 to Lockwoods Folly River SA, HQW 2.0
Montgomery Slough - (15-25v) From ICWW west of Lockwoods Folly Inlet extending eastward (2.4 Miles) SA, HQW 2.3
Mullet Creek - (15-25-1-19) From source to Lockwoods Folly River SA, HQW 5.7
Intracoastal Waterway - (15-25u) From a line crossing ICWW south of SR 1112 to Cape Fear River Basin SA, HQW 403.5
Intracoastal Waterway - (15-25t1) From a line across the ICWW 2030 meters west of NC 130 bridge to a line crossing ICWW south of SR1112 SA, HQW 292.8
Spring Creek - (15-25-1-21) From source to Lockwoods Folly River SA, HQW 2.4
Lockwoods Creek - (15-25-1-20) From source to Lockwoods Folly River SA, HQW 0.2
Lockwoods Folly River Fecal Coliform TMDL
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This document proposes to establish a TMDL for the Lockwoods Folly River and its tributaries. The selected watershed model calculated the watershed load to the Lockwoods Folly estuary which
includes loads from Mullet Creek, Spring Creek, Mill Creek, Lockwoods Creek, and the Lockwoods Folly River up to Brunswick County SR 1200. Therefore, the load reduction calculated for the
estuary is applied to all of the aforementioned segments. A TMDL was not developed for the
Intracoastal Waterway (ICWW) and Montgomery Slough because the hydrodynamics are not conducive to using the linked watershed and Tidal Prism modeling approach. The TMDL load
reduction does not apply to the ICWW or Montgomery Slough. These areas will instead be addressed in the TMDL implementation strategies.
Fecal coliform is an indicator organism used in water quality monitoring in shellfish waters to
indicate sources of waste from warm-blooded animals. When the water quality standard for fecal coliform in shellfish waters is exceeded, waters are closed for shellfish harvesting to protect human
health due to the potential risk from consuming raw molluscan shellfish from contaminated waters. The water quality goal of this TMDL is to reduce high fecal coliform concentrations to levels
whereby the designated uses for these waterbodies will be met.
A variety of data at the watershed scale were used to identify potential fecal coliform contributions. This data included land use, soils, septic distribution, shoreline sanitary survey data, and County
census data. Much of the potential fecal coliform contributions were analyzed using Geographic Information Systems (GIS) techniques. There are several stormwater permittees in the watershed
including the North Carolina Department of Transportation (NCDOT), the Town of Oak Island, and
several industrial stormwater permittees. The Town of Oak Island is located along the ICWW and falls outside of the modeled portion of the watershed. As such, its wasteload allocation could not be
estimated. The industrial stormwater permittees include sand pits, and concrete and asphalt facilities that are not of concern with regards to fecal coliform. Therefore, NCDOT is the only
permitted source included in the WLA and is addressed in this TMDL by separating their land use
contribution from other land uses. Taken collectively, the data indicates that the major contributions of fecal coliform loads are nonpoint source runoff, including bacteria from wildlife and pets.
A linked watershed and Tidal Prism modeling approach was utilized to estimate the fecal coliform load from the watershed to the estuary and to simulate fecal coliform concentrations in the estuary
from 2004 to 2009. This approach has been used in similar TMDLs in Maryland, Virginia, and North Carolina, though this TMDL uses a more simplified watershed model approach. Long-term model simulation is used to establish the TMDL, thereby accounting for the seasonal variability and critical
conditions, which represent the hydrology, hydrodynamics, and water quality condition of the shellfish harvesting areas. The load is then allocated to point and nonpoint sources.
One of the critical tasks for these TMDLs is to determine current loads from all potential sources in the watershed. The procedure needs to account for temporal variability caused by the seasonal variation and the wet-dry hydrological conditions. Long-term model simulation was conducted to
simulate fecal coliform concentration in the waterbodies. The long-term daily mean load is estimated for each watershed based on the watershed model results. These results were then used
to estimate the current load condition. The allowable loads for the restricted shellfish harvesting areas were then computed using both the median water quality standard for shellfish harvesting of
14 Most Probable Number (MPN)/100ml and the 90th percentile standard of 43 MPN/100ml. An
explicit Margin of Safety (MOS) of 10% was incorporated into the analysis to account for uncertainty. The TMDL developed for the Lockwoods Folly River restricted shellfish harvesting
areas was estimated to be 1.106 x 1012 counts of fecal coliform per day.
Lockwoods Folly River Fecal Coliform TMDL
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The goal of load allocation is to determine the estimated load for the drainage area while ensuring that the water quality standard can be attained. For restricted shellfish harvesting areas, the 90th
percentile criterion requires the greatest reduction. Therefore, the load reduction scenario is estimated based on the 90th percentile water quality standard. The load reduction needed in the
watershed of the restricted shellfish harvesting areas to meet the shellfish criteria and the load
allocations required to meet the TMDLs is 86%, including the MOS.
Once the EPA has approved a TMDL, and it is known what measures must be taken to reduce
pollution levels, the implementation of best management practices (BMPs) is expected to take place. An implementation plan is being developed as a separate document from this TMDL. The
North Carolina Department of Environment and Natural Resources (NCDENR) intends for the
required reductions to be implemented in an iterative process that first addresses those sources with the largest impact on water quality, with consideration given to ease of implementation and
cost.

Lockwoods Folly River Fecal Coliform TMDL
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1.0 Introduction
All states are required by Section 303(d) of the 1972 Federal Clean Water Act (CWA) to develop
Total Maximum Daily Loads (TMDL) for waterbodies that are impaired and cannot meet their
designated use. Designated uses include activities such as swimming, drinking water supply, and shellfish propagation and harvest. Water quality standards have been developed as both narrative
statements and numeric values which are designed to protect the designated uses of waterbodies. When water quality standards are not met, TMDLs are developed to calculate the total loading of a
pollutant which a waterbody can receive and still achieve their designated use. These TMDLs take
into account both seasonal variations and a protective margin of safety (MOS) to account for uncertainty. Water quality criteria may differ among waters with different designated uses.
A common pollutant in waters designated for shellfish propagation and harvesting is fecal coliform. While few fecal coliform are pathogenic, their detection indicates the presence of other
bacteriological contaminants such as E. coli. Some waterborne diseases associated with the consumption of raw shellfish include viral and bacterial gastroenteritis and hepatitis A. Fecal coliform are found in the intestinal tract of humans and other warm-blooded animals and are often
introduced to waterbodies through point source discharges of wastewater, or via nonpoint source contributions from runoff and failing septic systems.
The Lockwoods Folly River and its tributaries are located in the Lumber River Basin (NC Subbasin 03-07-59, HUC 030402070200). The River, estuary and their tributaries are located within the A-3 shellfish harvesting area, as designated by the North Carolina Division of Environmental Health
(NCDEH). The Lockwoods Folly River and the upriver portion of the estuary are Prohibited for shellfish harvesting due to excessive levels of fecal coliform bacteria. The two downstream portions
of the estuary are Conditionally Approved Open and Conditionally Approved Closed. The tributaries of Mill Creek, Mullet Creek, Lockwoods Creek and portions of Montgomery Slough and the
Intracoastal Waterway are also Prohibited. Spring Creek is Conditionally Approved Open for
shellfish harvesting. All of the previously mentioned segments are listed on the 2008 303(d) list as impaired due to fecal coliform.
The water quality goal of this TMDL is to reduce high fecal coliform concentrations in the impaired segments to levels such that the designated use for the restricted shellfish harvesting areas will be
met. The selected watershed model calculated the watershed load to the Lockwoods Folly estuary
which includes loads from Mullet Creek, Spring Creek, Mill Creek, Lockwoods Creek, and the Lockwoods Folly River up to Brunswick County SR 1200. Therefore, the load reduction calculated
for the estuary is applied to all of the aforementioned segments. A TMDL was not developed for the Intracoastal Waterway (ICWW) and Montgomery Slough because the hydrodynamics are not
conducive to using the linked watershed and Tidal Prism modeling approach. The TMDL load
reduction does not apply to the ICWW or Montgomery Slough. These areas will instead be addressed in the TMDL implementation strategies.

Lockwoods Folly River Fecal Coliform TMDL
2
1.1 TMDL Components
The 303(d) process requires that a TMDL be developed for each of the waters appearing in
Category 5 of the Surface Water Integrated 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). A 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 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 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 (30-month) window of data, assuming one sample per month. Generally, the primary components of a TMDL, as identified by the USEPA
(1991) 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. The margin of safety may be expressed explicitly as
unallocated assimilative capacity or implicitly due to conservative assumptions.
Seasonal Variation. The TMDL should consider seasonal variation in the pollutant loads and end-
point. Variability can arise due to stream flows, temperatures, and exceptional events (e.g.,
droughts, hurricanes).
Critical Conditions. Critical conditions indicate the combination of environmental factors that result
in just meeting the water quality criterion and have an acceptably low frequency of occurrence.
Section 303(d) of the CWA requires EPA to review all TMDLs for approval or disapproval. Once
Lockwoods Folly River Fecal Coliform TMDL
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EPA approves a TMDL, then the waterbody may be moved to Category 4a of the Integrated Report.
Waterbodies remain on Category 4a of the list until compliance with water quality standards is achieved. Where conditions are not appropriate for the development of a TMDL, management
strategies may still result in the restoration of water quality.
A 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. In addition, the TMDL may include
a future allocation (FA) when necessary. Conceptually, this definition is denoted by the equation:
TMDL = WLAs + LAs + MOS + (FA, where applicable)
This TMDL does not include future allocations.
1.2 Documentation of Impairment
All surface waters in the state are assigned a primary classification that is appropriate to the best
uses of that water. In addition to primary classifications, surface waters may be assigned a supplemental classification to provide special protection. The North Carolina Division of Water Quality (DWQ) Surface Water and Wetlands classification for the restricted shellfish harvesting
areas in the watershed is Class SA Waters – Shellfish Harvesting Waters (15A NCAC 02B.0221 Tidal Salt Water Quality Standards for Class SA Waters). A Class SA water is a waterbody that is
suitable for commercial shellfishing and all other tidal saltwater use (NCAC 2003). Additionally, these waterbodies have been assigned a supplemental classification of Class HQW – High Quality Waters. All Class SA waters are required to carry a supplemental designation of HQW or ORW
(Outstanding Resource Waters) by rule.
Eleven segments in the Lockwoods Folly River watershed have been included on 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.0021 (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.”
For this report, the monitoring data-averaging period was based on monitoring procedures for classifying SA water, i.e. the 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. For this report, the monitoring data analysis period was based on data
from 2004 to 2009. The water quality impairment was assessed using the geometric mean, median
Lockwoods Folly River Fecal Coliform TMDL
4
and 90th percentile concentrations.
1.3 Watershed Description
The Lockwoods Folly River is located in south central Brunswick County, within the Lumber River Basin south of Wilmington, NC (NC subbasin 03-07-59). Although part of the Lumber River Basin,
the river originates near the Town of Bolivia, flows westerly and then southwesterly and empties into
the Atlantic Ocean through the Lockwoods Folly River Inlet. The barrier islands of Oak Island and Holden Beach protect the inlet, and the Intracoastal Waterway (ICWW) is located landward of the
islands. Montgomery Slough partially bisects Oak Island towards the seaward side of the island, and is connected to the ICWW in two locations. The Lockwoods Folly estuary drains to the ICWW
before reaching the outlet to the Atlantic Ocean (Figure 1). The ICWW and Montgomery Slough do
not drain to the Lockwoods Folly estuary. Given their connection, and the open-ended nature of the ICWW, the hydrodynamics of these two waterbodies are not conducive to using the linked
watershed and Tidal Prism modeling approach. These areas will instead be addressed in the TMDL Implementation Plan strategies.
The watershed encompasses five 14-digit HUCS: 03040207020010, 03040207020020, 03040207020030, 03040207020040, and 03040207020050. The drainage area of the watershed is approximately 153 square miles (Figure 1).The Lockwoods Folly Estuary is approximately 3.2 miles
in length from the ICWW and moving landward, with an average depth of about 1.2 feet (mean low water). The dominant tide in this region is the lunar semi-diurnal (M2) tide with a tidal period of
12.42 hours. The assumed mean tidal range is 4.1 feet based on the NOAA station located at the Lockwoods Folly Inlet (NOAA 2009).
Lockwoods Folly River Fecal Coliform TMDL
5

Figure 1. Vicinity and watershed map
Southport-Supply Rd
17
Gilbert Rd
Stone Chimney Rd
Sunset Harbor Rd
Green Swamp Rd
Old Ocean Hwy
Lockwoods Folly River
Intracoastal Waterway
Montgomery Slough
ATLANTIC OCEAN
UT01
River Swamp
Middle Swamp
Royal Oak Swamp
Red Run
Midway Branc
h
Clark Branch
Nucitt Branch
Little Doe Creek
Ford Branch
Fall Swamp
Pinch Gut Creek
Mill Creek
Half Hell Branch
Spring Creek
Bolivia Branch
Ramshead Branch
Mullet Creek
Legend
DEHSS sites
NCCF site
Flow monitoring sites
Lockwoods Folly watershed
Major roads
Minor roads
Streams 0 2 41 Miles
Lumber River Basin LockwoodsFolly RiverWatershed
Lockwoods Folly River Fecal Coliform TMDL
6
1.3.1 Land Use/Land Cover
A land use layer for the watershed was created using the 2004 Brunswick County existing land use map, aerial imagery, and County parcel data. The land uses were assigned to 16 categories as
shown in Table 1. NCDOT was separated from other road surfaces in order to track their
contribution to fecal coliform loadings separately. At approximately 73%, the watershed is primarily comprised of forest land. Of the forested land, approximately 30% is wooded wetland and 20% is
managed pineland. Residential, commercial, industrial, and office land uses combined currently make up about 6% of the watershed. Other major land uses include open space at 7.6%, and row
crop at 4.8%. Current land use in the watershed is depicted in Figure 2.
Table 1. Land use distribution in the Lockwoods Folly River watershed
Land Use Category Area (acres) Percent
High Density Residential (0.07 - 0.22 acres) 807 0.8%
Medium Density Residential (0.23 - 0.33 acres) 617 0.6%
Low Density Residential (0.34 - 0.99 acres) 1519 1.5%
Very Low Density Residential (1 - 5 acres) 1888 1.9%
Commercial/Heavy Industrial 215 0.2%
Office/Institutional/Light Industrial 596 0.6%
Road (w/ ROW) non-NCDOT 1527 1.6%
Road (w/ ROW) NCDOT 1629 1.7%
Barren Land 220 0.2%
Managed Open Space 7456 7.6%
Golf Course 631 0.6%
Pasture 858 0.9%
Row Crop 4660 4.8%
Forest (includes wooded wetland and managed
pineland) 71407 72.9%
Emergent wetland 1860 1.9%
Water 2119 2.2%

Lockwoods Folly River Fecal Coliform TMDL
7

Figure 2. Current land use
St. James
Oak Island
Boiling Spring Lakes
Shallotte
Holden Beach
Bolivia
Varnamtown
Caswell Beach
OCEAN HWY E
OCEAN HWY W
SOUTHPORT-SUPPLY RD SE
GREEN SWAMP RD
OLD OCEAN HWY
MAIN ST
HOLDEN BEACH RD SW
GEORGE II HWY SE
WHITEVILLE RD
BEACH DR SW
GEORGE II HWY
OCEAN ISLE BEAC
H RD SW
BRICKL
ANDING RD SW
LONG BEACH RD
Royal Oak Swamp
River Swamp
Middle Swamp
Red Run
Midway Branch
Nucitt Branch
Scotts Branch
Little Doe Creek
Ford Branch
Fall Swamp
Pinch Gut Creek
Mill Creek
Half Hell Branch
Sarah Hole
Spring Creek
Ram
shead Branch
Atlantic Ocean
Lockwoods Folly River
Intracoastal Waterway
Legend
Streams
Municipalities
Model Subwatersheds
Land Use Categories
Bare Earth
Forest
Open Space
Row Crops
Pasture
Golf Course
Commercial/Heavy Industrial
Office/Institutional/Light Industrial
Residential High Density
Residential Medium Density
Residential Low Density
Residential Very Low Density
Roadway
Water
Wetland ³
2 01 Miles
Lockwoods Folly River Fecal Coliform TMDL
8
1.3.2 Soils
Most of the watershed is located in the Lower Coastal Plain soil region (Daniels et al., 1999). Upland soils adjacent to the floodplain include well drained and moderately well drained soils
(hydrologic soil group A or B) such as the loamy Baymeade (SCS 1986). Sandy, excessively
drained soils of the Kureb-Wando map units are located within the areas of Varnamtown, Sunset Harbor, and Oak Island. In addition, there are large areas of somewhat poorly to very poorly drained
soils such as Leon and Murville, Torhunta, and Croatan. Map units that are completely hydric soils or contain hydric soils make up about 89% of the watershed. Over 92% of the soils in the watershed
are rated as very limited in terms of septic suitability.
1.4 Water Quality Characterization
The Shellfish Sanitation and Recreational Water Quality Branch of the NCDEH 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 (NSSP), with oversight by the U.S. Food and Drug Administration to conduct shoreline surveys and
collect routine bacteria water quality samples in 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. The criteria for the shellfish harvesting areas are based on the 90th percentile, geometric mean, and median of the most recent 30 samples collected at a given
site. The criterion for the 90th percentile is not to exceed 43 cts/100mL. The criterion for the
geometric mean and median is not to exceed 14 cts/100mL. Shellfish growing areas throughout North Carolina are sampled using the systematic random sampling strategy as outlined in the
National Shellfish Sanitation Program’s Model Ordinance and guidance document. Routine bacteriological monitoring involves the sampling of shellfish monitoring sites during favorable
conditions in which the shellfish beds are open for harvesting to verify that fecal coliform levels are
low. In addition to the routine bacteriological monitoring of the areas, at some stations conditional area samples are collected. Conditional samples are collected after an area has been temporarily
closed due to rainfall in order to determine whether the shellfish area can be reopened. These samples may be more representative of fecal coliform levels during unfavorable conditions than
those collected during routine monitoring. However, it is common to wait a day or two after a rain event before conducting conditional sampling to allow the river to return to more normal conditions.
There are nine monitoring sites sampled by Shellfish Sanitation (DEHSS) which are located within
the modeled Lockwoods Folly estuary (Figure 3). As discussed in Section 3.1.3 the estuary was divided into four segments for modeling. All nine monitoring sites lie within the same segment
(M0S2).The summary statistics of the most recent 30 samples collected at these sites as of October 2009 are presented in Table 2. Also included in Table 2 are the total number of samples taken at each site between 2004 and 2009, the number of conditional samples in that period, and the date of
the latest sample and conditional sample collected at each site.
Lockwoods Folly River Fecal Coliform TMDL
9
Table 2. Summary statistics of observation data (2004 to October 2009)
Station
Last 30
Sample Geometric
Mean (MPN/100mL)
Last 30 Sample
Median (MPN/100mL)
Last 30 Sample 90th
Percentile (MPN/100mL)
Date of
Last Sample
Date of Last
Conditional Sample
No. of
Conditional Samples
No. of
Total Samples
5A 9 8 29 9/9/2009 11/8/2004 1 49
6A 7 5 41 9/9/2009 4/4/2005 1 37
7 6 4 37 10/7/2009 10/7/2009 94 118
7A 6 4 31 10/7/2009 10/7/2009 93 115
8 7 6 44 9/9/2009 5/1/2006 35 71
10 6 5 36 9/9/2009 4/4/2005 1 38
13 4 4 17 9/9/2009 10/1/2009 21 53
14A 9 8 40 9/9/2009 9/22/2005* 4 54*
14B 6 6 30 9/9/2009 na na 34
*16 samples collected by NCCF. Last sample collected on 12/12/2008.
The inclusion of conditional samples in developing summary statistics for the monitoring stations is
important for assessing water quality in the estuary under all conditions. Sites 7 and 7A have the
most complete monitoring record from 2004 to 2009 with 118 and 115, respectively. The majority of those samples at both sites were conditional samples collected consistently throughout the model
simulation period. Site 8 follows with 71 samples collected between 2004 and 2009 with 35 of them being conditional. However, the last conditional sample collected at Site 8 occurred in May of 2006.
One conditional sample was collected at sites 5A, 6A, and 10, while no conditional samples were
collected at 14B. During the model simulation period (2004-2009) only 4 conditional samples were collected at Site 14A. Additionally, the North Carolina Coastal Federation (NCCF) collected 16
samples at Site 14A for the development of the TMDL report. These additional samples were included in the computation of the summary statistics at this station (Table 2).
From the observed data, water quality standards are currently being violated at only one site. Site 8
is violating the 90th percentile standard for fecal coliform with a value of 44 cts/100mL (Table 2). Observed fecal coliform levels at the remaining sites are currently below the water quality
standards. However, prior to 2008, five of the monitoring sites were violating the 90th percentile water quality standard, with the highest fecal coliform levels occurring at sites 7 and 7A (Table 3).
The drop in the 30-month 90th percentiles at monitoring sites in the estuary began to occur in early
2008, possibly as a result of statewide drought which began in 2007. However, in addition to rainfall, land use, hydrology, and loading from various sources and pathways among other things
affect water quality in the estuary. This trend is particularly evident at sites 7 and 7A, where the most conditional samples have been collected of the nine monitoring sites. Graphs of the observed
data, 30-month median, and 30-month 90th percentile for each site are included in Appendix A along
with tables of the observed data. The graphs show that fecal coliform levels are currently increasing at Sites 7 and 7A as precipitation levels have increased.
Lockwoods Folly River Fecal Coliform TMDL
10
Table 3. Summary statistics of observation data (2004 to December 2007)
Station
Last 30
Sample Geometric
Mean (MPN/100mL)
Last 30 Sample
Median (MPN/100mL)
Last 30 Sample 90th
Percentile (MPN/100mL)
5A 10 8 53
6A na na na
7 11 8 85
7A 10 4 125
8 9 5 71
10 7 5 45
13 5 4 30
14A na na na
14B na na na
na = not available, <30 samples collected and summary statistics could not be calculated.

Lockwoods Folly River Fecal Coliform TMDL
11

Figure 3. Shellfish Sanitation monitoring station locations and TPWQM model segments
Spring Creek
Mullet Creek
Lockwoods Folly River
Mill Creek
Lockwoods
Creek
M0 S2
M0 S3
M0 S4
8
7
9A
11
10
13
7A
6A
5A
14B
14A
TPWQM segments
DEHSS monitoring stations
NCCFmonitoring station 0 1,000 2,000500Feet
Lockwoods Folly River Fecal Coliform TMDL
12
2.0 Source Assessment
2.1 Point Source Assessment
2.1.1 NPDES Wastewater Permits
There are currently no NPDES wastewater permitees in the watershed.
2.1.2 NPDES Stormwater Permits
Stormwater has previously been considered a nonpoint source; however, current EPA guidance and policy requires that NPDES-permitted stormwater sources be included in the wasteload
allocation (WLA) of the TMDL as opposed to the load allocation (LA). Many of the roadways in the watershed are maintained by the North Carolina Department of Transportation (NCDOT), including
US 17, Old Ocean Highway, Green Swamp Road, and Stone Chimney Road. These NCDOT roads fall under the NCDOT statewide NPDES stormwater permit. NCDOT’s contribution to fecal coliform
loading in the watershed was tracked separately in the model from other land use types in order to
calculate their wasteload allocation and load reduction requirements.
The Town of Oak Island is a Phase II stormwater community. A portion of the Town lies within the
Lockwoods Folly River watershed; however, surface runoff from the Town drains to both the Intracoastal Waterway and Montgomery Slough. These two waterbodies do not flow into the
Lockwoods Folly estuary. The hydrodynamics of the ICWW and Montgomery Slough are not
conducive to using the linked watershed and Tidal Prism modeling approach due to the open boundary of the ICWW and the connectivity of Montgomery Slough. Therefore, a TMDL was not
developed for these waterbody segments and the TMDL load reduction does not apply. As such a wasteload allocation could not be calculated separately for the Town of Oak Island. However, the
Town will be addressed in the TMDL Implementation Plan. Additionally, the Town’s future
stormwater permits will incorporate strategies for reductions in fecal coliform loads outlined in the plan. Strategies will include both structural and non-structural best management practices (BMPs)
as well as programs to assess the effectiveness of these strategies in reducing fecal coliform loads from the Town.
There are also four active NPDES industrial stormwater permits in the watershed for sand pit,
concrete, and asphalt facilities (Table 4). Fecal coliform loading from these types of facilities are not of concern. Therefore, a separate WLA was not calculated for these stormwater permits.
Table 4. Active NPDES industrial stormwater permits in the watershed
Permit No. Name
NCG020618 Holden Beach Sandpit #2
NCG020630 Tripp’s Construction Company LLC
NCG140277 S & W Ready Mix Concrete - Bolivia
NCG160037 Barnhill Contracting Company

Lockwoods Folly River Fecal Coliform TMDL
13
2.2 Nonpoint Source Assessment
Nonpoint sources of fecal coliform bacteria do not have one discharge point but occur over the entire length of a stream or waterbody. There are many types of nonpoint sources in the watershed
discharging to the restricted shellfish harvesting areas. Fecal coliform bacteria from non-human sources originate from excretions from livestock, wildlife, and pets. 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. A more direct path to the restricted areas occurs when wildlife defecates in the drainage network, including stream and wetland
channels, and stormwater conveyance pipes. 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. 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.
The purpose of the source assessment was to estimate the populations of pets, livestock, and wildlife and the number of septic systems in the project area. These numbers were derived based
on data from various sources including Brunswick County Census data, pet and wildlife statistical data, personal communications with property owners, Shellfish Sanitation Shoreline Survey data, and land use data. A description of these parameters and the development of the nonpoint source
assessment are described in detail in Appendix C. The distribution of nonpoint source loads for the watershed is presented in Table 5. These values are direct inputs to the watershed, not the estuary,
from various sources and do not take into account decay and transport, on land or in-stream.
Table 5. Estimated distribution of direct fecal coliform nonpoint source loads to the watershed
Source Fecal coliform (cts/day) % contribution
Livestock 9.05E+12 15.3%
Wildlife 3.10E+13 52.3%
Pets 1.75E+13 29.6%
Human 1.67E+12 2.8%
Total 5.92E+13
*The values included in this table are inputs to the watershed, not the estuary (or waterbody),
from various sources and do not take into account decay and transport, on land or in-stream.
Lockwoods Folly River Fecal Coliform TMDL
14
3.0 Total Maximum Daily Loads and Load Allocation
This section documents fecal coliform TMDL development and allocations for the Lockwoods Folly River watershed. In order to estimate the existing load and allowable load for the watershed, a
watershed model was used to simulate fecal coliform loads from the watershed to the estuary. Once
the fecal coliform is discharged to the receiving water, it will be transported to the different areas in the estuary due to the interaction of tide and freshwater discharge and decay. Therefore, a tidal
model was used to simulate fecal coliform concentrations within the estuary. The required load reduction was determined over the model simulation period (2004 to 2009) based on modeling
results. The TMDL is presented as counts per day. The following sections present the detailed
TMDL development and load allocations for the project area. The first section describes the watershed and tidal models used for the TMDL study, as well as model set up. The second section
presents the model calibration and validation procedures. The third section describes the TMDL calculation. The fourth and fifth sections address the critical period and seasonal variability. The
sixth section discusses TMDL loading caps. The seventh and eighth section presents the load allocation and waste load allocation, respectively. The ninth section presents the margin of safety. Finally, the variables of the equation are combined in a summary accounting of the TMDL.
3.1 Modeling Approach
Based on the considerations of the influence of nonpoint sources and tidal-induced transport in the estuary, analysis of the monitoring data, review of the literature, and past pathogens modeling
applications, a linked watershed and tidal modeling approach was used to simulate fecal coliform loading from the watershed and fecal coliform concentration in the estuary. A description of the
modeling approach is provided in the following section. Detailed documentation of the modeling
methods is provided in Stantec, 2010.
3.1.1 Watershed Model Description
A simplified watershed model was developed utilizing HEC-HMS (v. 3.3) to estimate flow for the Lockwoods Folly River watershed given land use, soils, and precipitation data. A fecal coliform
loading model from the watershed to the estuary was then developed using literature values for
event mean concentrations (EMC) for each land use category in conjunction with the runoff calculated from the various soil-land use combinations in the watershed. HEC-HMS is a Graphical
User Interface (GUI) based program designed to simulate the precipitation-runoff processes of dendritic watershed systems. It is able to incorporate storm flow, base flow, and evapotranspiration
in a continuous simulation of hydrologic processes.
3.1.2 Tidal Prism Description
The Tidal Prism Water Quality Model was selected as the receiving water quality model. TPWQM
simulates tidal transport in terms of the concept of tidal flushing (Ketchum, 1951). The tidal prism, or inter-tidal volume, is the amount of water entering and leaving a coastal basin during each tidal
cycle. During flood tide, a large amount of water (i.e., the tidal prism) floods into the coastal basin.
This amount of water mixes with the lower tidal water within the basin. A portion of pollutant inside the basin will be transported out of the basin during ebb tide as water is transported out of the
basin. The TPWQM can simulate pollutant transport in an estuary both temporally and spatially
Lockwoods Folly River Fecal Coliform TMDL
15
(Kuo and Neilson, 1988; Kuo et al., 1998). The input data required to run the model includes tidal range, surface area, and depth of the waterbody. Thus, the tidal prism for the modeling area can be
estimated based on the volume of the basins and the tidal range in the area.
3.1.3 Model Setup
The Lockwoods Folly River watershed was delineated into 28 subwatersheds for the watershed
loading model using available topography data (DEM grid), aerial photography, and field reconnaissance data. Figure 4 depicts the watershed delineation. It should be noted that the 28th
subwatershed drains to the ICWW and was not modeled as contributing flow and fecal coliform load to the Lockwoods Folly estuary. A unique land use layer was developed for the watershed as
described in Section 1.3.1.
The project estuary was divided into 4 segments based on the Tidal Prism theory (Kuo and Park 1994), with the first segment being the seaward boundary. The segmentation is depicted in Figure
3. The volume of the estuary was derived using bathymetry data from the US Army Corps of Engineers for the Lockwoods Folly channel through the estuary, in addition to field bathymetry data
points collected in November 2009 by the NCCF throughout the estuary. The dominant tide in this
region is the semi-diurnal (M2) tide with a tidal range of 4.2 feet based on the NOAA tidal station at the Lockwoods Folly Inlet (NOAA 2009). The surface area of each segment together with tidal
range was used to compute the high tide water volume and tidal prisms. Using mean tidal range and mean volume, the model provides the daily mean results, but not the instantaneous condition,
which is consistent with the standard. The geometry information of the TPWQM is listed in Appendix
B. Given the relatively low level of contribution of land use immediately surrounding the estuary, all flows and loads were modeled as entering the estuary through the Lockwoods Folly River, in the
3rd segment of the TPWQM (M0S3). All monitoring sites are located in Segment M0S2 (Figure 3). Since the TPWQM is on the scale of a tidal cycle (i.e., about 12.42 hours), the load per tidal cycle
was calculated by aggregating the hourly loads generated from the watershed loading model. The
simulation period of the TPWQM is the same as that of the watershed model.

Lockwoods Folly River Fecal Coliform TMDL
16

Figure 4. Watershed model subwatersheds
Southport-Supply Rd
17
Gilbert Rd
Stone Chimney Rd
Sunset Harbor Rd
Green Swamp Rd
Old Ocean Hwy
River Swamp
Middle Swamp
Royal Oak Swamp
Red Run
Midway Branch
Clark Branch
Nucitt Branch
Little Doe Creek
Ford Branch
Fall Swamp
Pinch Gu
t Creek
Mill Creek
Half Hell Branch
Spring Creek
Bolivia Branch
Ram
shead Branch
Mullet Creek
Atlantic Ocean
Lockwoods Folly River
Intracoastal Waterway
Legend
Flow monitoring sites
Model subbwatersheds
Lockwoods Folly watershed
Major roads
Minor roads
Streams 0 2 41 Miles
Lockwoods Folly River Fecal Coliform TMDL
17
3.1.4 Meteorological Data
One of the major inputs for the watershed hydrology and loading models is precipitation. The nature
of rainfall in the Lockwoods Folly River watershed is very non-uniform. As such, precipitation data from three separate precipitation gages was collected in order to model the variability in flow across
the watershed.
The first precipitation gage is the Nature Conservancy RAWS station (NNAC), located within the northern portion of the watershed along Green Swamp Road. Comprehensive precipitation records
for other rain gages within the watershed were not available. As such, the other two stations from which precipitation data was gathered are located outside of the watershed: Sunny Point RAWS
station (NSUN) and Grand Strand Airport Station (NCRE). Data was retrieved for January 1, 2004
until September 30, 2009 from the State Climate Office of North Carolina for the three gages (NC CRONOS 2009). It should be noted that although two of the precipitation gages are not located
directly within the watershed, their data demonstrated that the occurrence of rainfall events at these stations matched well with events detected at the NNAC station, i.e. large storms of long duration
were found to occur concurrently at all gages. Precipitation data from each station was attributed to
the model subwatersheds, based on their proximity. The average monthly precipitation for each gage over the model simulation period is presented in Figure 5.
Average monthly precipitation
0
1
2
3
4
5
6
7
8
9
Ja
n
u
a
r
y
Fe
b
r
u
a
r
y
Ma
r
c
h
Ap
r
i
l
Ma
y
Ju
n
e
Ju
l
y
Au
g
u
s
t
Se
p
t
e
m
b
e
r
Oc
t
o
b
e
r
No
v
e
m
b
e
r
De
c
e
m
b
e
r
Month
Pr
e
c
i
p
i
t
a
t
i
o
n

(
i
n
c
h
e
s
)
NNAC
NSUN
KCRE

Figure 5. Average monthly precipitation (2004-2009) for the three precipitation gages
Lockwoods Folly River Fecal Coliform TMDL
18
3.2 Model Calibration and Validation
Both the watershed and Tidal Prism models were calibrated and verified based on observed data. A description of the model calibration and validation is presented in the following sections.
3.2.1 Watershed Model Calibration
The hydrology of the HEC-HMS watershed model was calibrated and verified for water years 2008
to 2009. There is no long-term USGS gage in the drainage basin; however, a stream gage was
installed for the development of the TMDL model. This gage is located on the Lockwoods Folly River off of Old Ocean Highway (Figure 1). The stream gage was installed in August 2008 and
recorded data through July 2009. The hydrology calibration involved the adjustment of model parameters such that agreement was achieved between simulated flows and stream flow data
measured at the stream gage. The model parameters adjusted included initial deficit, maximum
storage, constant loss rate, and initial storage. Calibration of the hydrology model was conducted from October 2008 to February 2009. The model was then verified against stream gage data from
February 2009 to July 2009. Graphs of the model calibration and validation are shown in Figures 6 and 7, respectively.
0
10
20
30
40
50
60
70
80
90
100
10/11/2008 10/31/2008 11/20/2008 12/10/2008 12/30/2008 1/19/2009 2/8/2009
Fl
o
w
 (c
f
s
)
Date
Hydrology Calibration (10/2008 ‐2/2009)
Modeled
Observed

Figure 6. Hydrology model calibration

Lockwoods Folly River Fecal Coliform TMDL
19
0
20
40
60
80
100
120
140
160
180
2/11/2009 3/3/2009 3/23/2009 4/12/2009 5/2/2009 5/22/2009 6/11/2009 7/1/2009
Fl
o
w
 (c
f
s
)
Date
Hydrology Validation(2/2009 ‐7/2009)
Modeled
Observed

Figure 7. Hydrology model validation
The model was also calibrated such that the quantity of runoff between observed and modeled
results were similar. This comparison was made at the seasonal level and for the calibration period as a whole (Table 6). Additionally, model results for total discharge, relative to drainage area, was
compared to discharge from a USGS gage to show that model results were within the same range of values. This comparison was made over both the calibration and validation period (Table 7). The
USGS gage is located on Hood Creek near Leland, North Carolina (USGS 02105900) with a
drainage area of 21.6 square miles.
Table 6. Comparison of observed and modeled runoff

Modeled
Runoff
(inches)
Observed
Runoff
(inches)
Percent
Difference
Fall 2008 1.53 1.20 27%
Winter 2008-2009 1.90 2.09 -9%
Spring 2009 2.83 2.50 13%
Total 6.26 5.80 8%
Lockwoods Folly River Fecal Coliform TMDL
20
Table 7. Comparison of total seasonal discharge (inches)

Observed Discharge at USGS Gage Hood
Creek (inches)
Model Discharge at Calibration Site (Old
Ocean Hwy) (inches)
Modeled Discharge to Lockwoods Folly
Estuary (inches)
Fall 2008 2.50 1.69 1.69
Winter 2008-2009 1.95 1.78 1.86
Spring 2009 1.74 2.59 2.24
Total 6.19 6.06 5.79
Percent difference criteria for modeled runoff vary at the annual and seasonal scale. According to
Lumb et. al (1994) ±10% is preferred at the annual scale, whereas ±30% is acceptable at the
seasonal scale. These criteria have been met by the calibrated hydrology model. There is high variability in rainfall in the watershed which leads to greater differences between observed and
modeled runoff than might be observed in watersheds with more uniform rainfall distribution patterns. Additionally, the difference between modeled and observed runoff were enhanced by two
instances of extreme peak flows.
During the model calibration/validation periods, the model showed significant differences from the observed data during two events. The first event occurred during the calibration period on
November 13, 2008 (Figure 6). The closest precipitation gage (NNAC) to the stream gage was used for the precipitation input to subwatersheds upstream of the stream gage. The NNAC precipitation
gage is located approximately 6 miles west of the stream gage. The NNAC gage showed a total rainfall of 1.08 inches on November 13 with 1.05 inches occurring in one hour. The model over predicted flow during this event by approximately 250%. Analysis of this event and the remainder of
the record indicate that the model may over predict discharge for high rainfall intensities. However, the model did accurately approximate peak flow values and discharge volume for a storm occurring
on May 17, 2009. This storm consisted of 2.28 inches of rainfall with a peak intensity of 0.83 inches in one hour. In general, the model more accurately predicts flows for storms with intensities less
than 1 inch per hour. Storm events with intensities greater than 1 inch per hour happen rarely in this
area. Reviewing the rainfall record for the watershed, such events occur approximately five times a year.
The second event in which a significant difference between the model and observed data occurred took place during the validation period on June 14, 2009 (Figure 7). The NNAC precipitation gage
recorded a total rainfall of 1.51 inches, with 1.46 inches occurring in the first hour of rainfall. With
only a slight increase in discharge recorded at the stream gage, this storm event was likely a summer thunderstorm and high intensity rainfall did not occur in the watershed upstream of the
stream gage.
After flow rates from each land use type were determined, fecal coliform loads were calculated
using EMC (event mean concentration) values from pertinent research (Table 8). A description of
EMC selection can be found in Appendix E. These loads were further modified to account for the “first flush” effect by applying a multiplying factor early in storms and a dividing factor as flows
decrease. As discharge values were modeled to increase by a certain percentage from the previous time step, the multiplying factor was applied. Otherwise, a dividing factor was applied to the fecal
coliform concentration. The percent increase, multiplying, and dividing factors were adjusted during
the Tidal Prism Water Quality Model (TPWQM) calibration where fecal coliform loads to the estuary
Lockwoods Folly River Fecal Coliform TMDL
21
were calibrated against observed data collected by DEHSS (Section 3.2.2).
Table 8. Selected EMC Values (cfu/100ml)
Land Use
EMC Value
(cfu/100ml)
Low Density Residential 5150
Medium Density Residential 5150
High Density Residential 5150
Office and Light Industrial 1389
Commercial and Heavy Industrial 2125
Road 1400
Forest 500
Golf and Managed Open Space 500
Pasture 1000
Row Crop 500

3.2.2 Tidal Prism Model Calibration
Calibration point selection
The TPWQM calibration was conducted based on the comparison of model simulated and observed fecal coliform concentrations in the estuary. Several factors were considered in selecting from the
monitoring sites for the model calibration. These factors included current water quality violations, past water quality violations, robustness of the data record, and location of the site in the estuary.
Site 8 is the only monitoring site currently violating water quality standards (as of October 2009).
However, this site is located along the shoreline in the southeastern portion of model segment M0S2 in the estuary and is less influenced by tidal mixing than sites located in the center of the
estuary. Sites 7 and 7A are centrally located in model segment M0S2 of the estuary (Figure 3). Both sites have the most complete data records of the monitoring sites, including the most extensive
conditional monitoring records. While these sites are not currently violating water quality standards they did demonstrate the highest fecal coliform levels prior to the 2007 drought.
Model results for model segment M0S2 were compared to observed data at sites 7A and 8 during
the calibration. Site 7A was selected as a calibration point for the TPWQM due to its central location in the estuary and its extensive data record. Additionally, the calibration was optimized by
comparing model results to observed data at Site 8 to ensure that the calibrated model accurately represents both past and current water quality violations.
Calibration
The two parameters that can be adjusted within the TPWQM during calibration are the return ratio and the fecal coliform decay rate. The return ratio is the fraction of water leaving the estuary during
Lockwoods Folly River Fecal Coliform TMDL
22
the ebb tide that will be transported back to the estuary during the next flood tide. The return ratio ranges from 0 to 1. Past studies of the TPWQM have demonstrated that the calculated salinity is
relatively insensitive to the value of return ratio between 0.1 to 0.5 and the value of 0.3 works well for small creeks in Virginia (Kuo, et al. 1998). Return ratio was adjusted during model calibration for
the Lockwoods Folly estuary. It was found that the Lockwoods Folly estuary is also insensitive to
adjustments in return ratio. The final return ratio selected for the Lockwoods Folly TPWQM was 0.3. The first order decay is used in the model to represent the fecal coliform die-off due to temperature,
salinity, solar radiation, and loss due to settling and other factors. A system with a higher decay rate has a higher assimilative capacity than a system with a lower decay rate. The value of decay rate
varies from 0.7 to 3.0 per day in salt water (Mancini 1978; Thomann and Mueller 1987). A decay
rate of 0.7 per day was used for the Lockwoods Folly estuary as a conservative estimate in the TMDL model.
Fecal coliform loads to the estuary were also adjusted during the TPWQM model calibration. The calibration procedure involved adjusting the multiplier and divisor values described in Section 3.2.1
which adjust the fecal coliform concentrations in runoff over a storm event. The final values for the
multiplying and dividing factors were selected such that the modeled fecal coliform concentrations in Segment M0S2 of the estuary fell within the range of observed values at Site 7A and Site 8
during the model simulation period. Additionally, it was verified that the model results approximated the observed 30-sample 90th percentile over the 5-year model simulation period. The 90th percentile
is a criterion used by DEHSS as a standard for shellfish use ratings. Model results and observed
values for Site 7A are presented in Figure 8. The comparison of the model 30-month 90th percentile and Site 7A observed 90th percentile are presented in Figure 9. Note that in Figure 9, each point
represents the 90th percentile of the previous 30 months. Therefore, from 2004 to 2009 the first modeled point appears in July of 2006. Figure 10 depicts the comparison of model results to
observed fecal coliform levels at Site 8. The comparison of the modeled and Site 8 observed 30-
month 90th percentiles is presented in Figure 11.
The observed measurements show the lowest concentration is always 1.7 MPN/100ml. This is due
to the laboratory methods used for determining the fecal coliform counts. The model was not able to consistently capture these low concentration events. The model may not have captured these lower
baseline values due to the length and shallow geometry of the estuary and an inability to model
sufficient tidal flushing. However, the high concentration is more critical for determining the bacteria capacity of the estuary. The 5-year model simulation period demonstrated seasonal variability and
captured peak fecal coliform concentrations compared to observed data. Given the long-term simulation results, the overall model performance is satisfactory.
Lockwoods Folly River Fecal Coliform TMDL
23
1
10
100
1000
01/01/04 05/15/05 09/27/06 02/09/08 06/23/09
Fe
c
a
l

c
o
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f
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r
m

(
c
o
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n
t
s
/
1
0
0
m
L
)
Date
Observed FC (7A)
Modeled FC

Figure 8. Modeled fecal coliform concentration for model segment M0S2 and observed fecal coliform concentration at Site 7A

0
20
40
60
80
100
120
140
160
180
6/22/2006 1/8/2007 7/27/2007 2/12/2008 8/30/2008 3/18/2009 10/4/2009
Fe
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f
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(
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Date
90th percentile standard
7A 90th percentile
Modeled 90th percentile

Figure 9. Modeled 90th percentile fecal coliform concentration for model segment M0S2 and
observed 90th percentile fecal coliform concentration at Site 7A
Lockwoods Folly River Fecal Coliform TMDL
24

1
10
100
1000
1/1/2004 5/15/2005 9/27/2006 2/9/2008 6/23/2009
Fe
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(
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m
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)
Date
Observed FC (Site 8)
Modeled FC

Figure 10. Modeled fecal coliform concentration for model segment M0S2 and observed fecal
coliform concentration at Site 8

0
20
40
60
80
100
120
140
160
180
200
6/22/2006 1/8/2007 7/27/2007 2/12/2008 8/30/2008 3/18/2009 10/4/2009
Fe
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Date
90th percentile standard
Site 8 90th percentile
Modeled 90th percentile

Figure 11. Modeled 90th percentile fecal coliform concentration for model segment M0S2 and
observed 90th percentile fecal coliform concentration at Site 8
Lockwoods Folly River Fecal Coliform TMDL
25
3.3 TMDL Calculation
The existing load (or current condition) is estimated as the sum of all the loads from subwatersheds discharging into the estuary. The loading is expressed as counts per day. The TMDL calculation is
based on the water quality criteria; in this case it is the median and 90th percentile for the most recent 30 samples. Since the samples are taken on an approximately monthly basis (i.e., samples
can be taken in any month), the running 30-month median and 30-month 90th percentile were
calculated for the model segment containing the TPWQM calibration points (Segment M0S2). The watershed loading was reduced until both water quality standards were met in Segment M0S2 at all
times during the TMDL period. This segment contains all water quality monitoring stations in the estuary therefore load reductions determined for the segment are applicable to all stations.
The final load is the maximum allowed daily load, or TMDL. The load reduction is calculated as the
difference between the current condition and the TMDL loading. A summary of existing load and TMDL loading is presented in Table 9. The model time series plots of both the running 30-month
median and 90th percentile for Segment M0S2 of the estuary under existing conditions and with the TMDL loading are presented in Appendix D.
Lockwoods Folly River Fecal Coliform TMDL
26
Table 9. TMDL summary
Waterbody Pollutant
Existing
Load WLA LA MOS TMDL
Reduction
Needed*
Lockwoods
Folly River (15-
25-1-(16)c)
Lockwoods Folly River (15-25-1-(16)a), Lockwoods Folly River (15-25-1-(16)b), Lockwoods Folly River (15-25-1-(16)d), Mill Creek, Mullet Creek, Spring Creek, Lockwoods Creek
Fecal coliform (counts/day) 6.910E+12 2.097E+11 7.855E+11 1.106E+11 1.106E+12 84%
WLA = wasteload allocation; LA = load allocation, MOS = margin of safety
*When the MOS is included, the total required reduction is 86%
3.4 Critical Condition
The EPA Code of Federal Regulations (40 CFR 130.7 (c) (1)) requires TMDLs to take into account critical conditions for stream flow, loading, and water quality parameters. The intent of this
requirement is to ensure that the water quality of the waterbody is protected during times when it is most vulnerable. The critical condition accounts for the hydrologic variation in the watershed over many sampling years whereas the critical period is the condition under which a waterbody is the
most likely to violate the water quality standard(s).
The 90th percentile concentration is the concentration exceeded only 10% of the time. Since the
model simulation period spans 5 years, the critical condition is implicitly included in the value of the
90th percentile of model results. Given the length of the monitoring record and model simulation and the standard’s recognition of unusual and infrequent events, the 90th percentile is used instead of
the absolute maximum.
3.5 Seasonality
Fecal coliform distributions often show high seasonal variability, which is required to be considered
in TMDL determinations. The seasonal fecal coliform distributions of observed data at Sites 7A and 8 are presented in Figures 12 and 13. The results show that high fecal coliform levels occur
throughout the year in the estuary. The average monthly concentrations are relatively similar
between months at both sites, though Site 7A shows slightly more variation. The highest concentrations occur in April at both monitoring sites. The lowest concentrations occur in February
and the late spring months.
The largest standard deviation corresponds to the highest concentration for each station. These
high concentrations result in a high 90th percentile concentration. Given the length of the model
simulation, the seasonal variability is directly included in the model simulation.

Lockwoods Folly River Fecal Coliform TMDL
27
1
10
100
1000
1 2 3 4 5 6 7 8 9 10 11 12
Fe
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f
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m

(
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1
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m
L
)
Month
Site 7A

Figure 12. Distribution of monthly average fecal coliform concentration at Site 7A (log scale)

1
10
100
1000
1 2 3 4 5 6 7 8 9 10 11 12
Fe
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)
Month
Site 8

Figure 13. Distribution of monthly average fecal coliform concentration at Site 8 (log scale)
Lockwoods Folly River Fecal Coliform TMDL
28
3.6 TMDL Loading Cap
This section presents the TMDL for the median and 90th percentile conditions for the Lockwoods Folly estuary and tidal creeks. The TMDL was calculated based on the model simulation results.
The TMDL for the estuary was calculated to be 1.106 x 1012, with the TMDL calculation period from 7/1/2004 to 1/1/2007. The greater reduction required when comparing the median and the 90th
percentile results was used for the TMDL. Based on model results, the 90th percentile is the stricter
standard which requires the greatest reduction.
The TMDL calculation period is the 30 months preceding the last daily prediction to meet the
standard. Thus, the averaging period for the development of the TMDL used daily predictions from the TMDL model runs for the 30 months preceding the highest 90th percentile concentration over
the model simulation period. Over this calculation period, daily bacteria loading predictions were
taken from each model subwatershed and subsequently summed across the watershed. The daily average load was then calculated over the 30-month period. As seen in Figure D1 (Appendix D) the
highest 90th percentile during the model simulation period occurred on 1/1/2007. Thus, the TMDL was calculated for the 30 months from 7/1/2004 to 1/1/2007.
Load reductions required to meet the TMDL are 84% (excluding the MOS). The reduction
established based on the 90th percentile criterion indicates that the waterbody 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.
3.7 Wasteload Allocation
As described in Section 2.1.2, NCDOT is the only NPDES-permitted discharge in the watershed
included in the WLA. Bacteria loading coming from NCDOT land was isolated from other sources
using the delineated land use and calibrated model as a base. The model was rerun setting the EMC on NCDOT land to zero. The difference between the calibrated model run and the model run
without NCDOT represents NCDOT’s existing fecal coliform load to the Lockwoods Folly estuary. The existing NCDOT load was calculated over the same time period as the TMDL calculation
(7/1/2004 – 1/1/2007) (Section 3.6), with a result of 4.46 x 1011 counts per day (Table 10). NCDOT’s
contribution is 6% of the total fecal coliform load from the watershed to the estuary. The required reduction from NCDOT land was calculated to be 53% of their existing load. This reduction is based
on NCDOTs relative contribution to fecal loads using its EMC values compared to a developed land area weighted EMC value that was calculated using land use area (Table 1) and corresponding
EMC values (Table 8). The resulting WLA is 2.097 x 1011 counts per day. This value and the margin
of safety (Section 3.9) were then subtracted from the TMDL loading cap to determine the final LA (Section 3.8).
Table 10. Wasteload allocation summary
Pollutant NCDOT Existing Load WLA Reduction Needed
Fecal coliform (counts/day) 4.462E+11 2.097E+11 53%

Lockwoods Folly River Fecal Coliform TMDL
29
3.8 Load Allocation
The load allocations were determined using the same period as the TMDL calculation (Section 3.6). Thus, the averaging period for the development of the TMDLs used daily predictions from the TMDL
model runs for the 30 months preceding the highest 90th percentile concentration. Over this period, daily bacteria loading predictions were taken from each model subwatershed and subsequently
summed across the watershed. The daily average was then calculated which serves as the basis
for the load allocation. The wasteload allocation (WLA) and the margin of safety (MOS) were subtracted from the TMDL to determine the final load allocation (LA).
3.9 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
waterbodies. The MOS is intended to account for such uncertainties in a manner that is
conservative from the standpoint of environmental protection.
For TMDL development, the MOS needs to be incorporated to account for uncertainty due to model
parameter selection. Based on previous model sensitivity analysis, it has been determined that the most sensitive parameter is the decay rate. The value of the decay rate varies from 0.7 to 3.0 per
day in salt water (Mancini, 1978; Thomann and Mueller, 1987, EPA 1985). A decay rate of 0.7 per
day in the estuary was used as a conservative estimate in the TMDL model. An explicit MOS was also included in the TMDL calculation as a conservative estimate. The explicit MOS was achieved
by applying a 10% load reduction from the calculated TMDL.
3.10 Summary of Total Maximum Daily Load
As explained in the previous sections, the TMDL was calculated based on model runs that had a
maximum 30-month 90th percentile concentration of 43 MPN/100 ml. The load reductions calculated
for the TMDL addresses the reduction required for all monitoring stations in the estuary. Additionally an explicit margin of safety of 10% was applied to the TMDL load.
NCDOT is the only NPDES-permitted source included in the WLA column. The Town of Oak Island is a Phase II stormwater community. However, it lies in a portion of the watershed that could not be
modeled due to the hydrodynamics of the ICWW on Montgomery Slough and a WLA could not be
determined for the Town (Section 2.1.2). The Town will be addressed in the TMDL Implementation Plan. Additionally, the Town’s future stormwater permits will incorporate strategies for reductions in
fecal coliform loads outlined in the Implementation Plan. Strategies will include both structural and non-structural best management practices (BMPs) as well as programs to assess the effectiveness
of these strategies in reducing fecal coliform loads from the Town. Four active industrial stormwater permittees are also present in the watershed; however, these are sand pit, concrete, and asphalt facilities and fecal coliform loading from these facilities are not of concern. Therefore, a separate
WLA was not calculated for these stormwater permits.
Lockwoods Folly River Fecal Coliform TMDL
30
The TMDL calculated based on the 30 months preceding the last highest 90th percentile concentration during the 5-year model simulation period is summarized as follows:
Waterbody Pollutant Existing Load WLA LA MOS TMDL Reduction Needed*
Lockwoods
Folly River (15-
25-1-(16)c)
Lockwoods Folly River (15-25-1-(16)a), Lockwoods Folly River (15-25-
1-(16)b), Lockwoods Folly River (15-25-1-(16)d), Mill Creek, Mullet Creek, Spring Creek,
Lockwoods Creek
Fecal coliform (counts/day) 6.910E+12 2.097E+11 7.855E+11 1.106E+11 1.106E+12 84%
Where:
TMDL = Total Maximum Daily Load
LA = Load Allocation (Nonpoint Source)
WLA = Waste Load Allocation (Point Source)
MOS = Margin of Safety
*When the MOS is included, the total required reduction is 86%
4.0 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 TMDL Implementation Plan will be developed as a separate document to this TMDL report. The Plan will be developed based on this TMDL,
strategies put forth by the Lockwoods Folly Roundtable project, and with input from the North
Carolina Coastal Federation, the North Carolina Division of Water Quality and other stakeholders. While the TMDL load reduction does not apply to the ICWW or Montgomery Slough, these waters
will be included in the implementation plan. Potential funding sources for implementation include Section 319 funds and 205(j) funds, as well as the Clean Water Management Trust Fund, EPA
Environmental Education Grants and EPA Water Quality Agreement Grants, among others.
At a minimum the Implementation Plan will follow the Nine Key Elements for implementing watershed plans outlined by the EPA. These nine elements include:
1. Identify the cause of impairment and pollutant sources. 2. Estimate the load reductions expected from management measures.
3. Describe the nonpoint source management measures that will need to be implemented
to achieve the load reductions in 2 and the critical areas in which those measures will be needed to implement this plan.
4. Estimate the amount of technical and financial assistance needed, associated costs, and/or the sources and authorities that will be relied upon to implement this plan.
Lockwoods Folly River Fecal Coliform TMDL
31
5. Include an information and educational component to enhance public understanding of the project and encourage their early and continued participation in selecting, designing,
and implementing the nonpoint source management measure that will be implemented. 6. Provide a schedule for implementing the nonpoint source management measures
identified in this plan that is reasonably expeditious.
7. Describe the interim milestones for determining whether nonpoint source management measures or other control actions are being implemented.
8. Provide a set of criteria that can be used to determine whether loading reductions are being achieved over time and substantial progress is being made toward attaining water
quality standards.
9. Monitor to evaluate the effectiveness of the implementation efforts over time, measured against criteria established under item 8 above.
5.0 Stream Monitoring
The Shellfish Sanitation Section of DEH should continue the systematic random sampling strategy
in the TMDL waters, even if the waters are eventually permanently closed to shellfish harvesting. This system is well-suited for monitoring and classifying shellfish waters and it can serve to track
the effectiveness of TMDL implementation and water quality improvements. DEHSS will continue to close the areas if levels of fecal coliform indicate that harvesting shellfish from those waters could
cause a public health risk. Additionally, there will be a program to assess fecal coliform load
reductions from the Town of Oak Island, a Phase II stormwater community, in its future stormwater permits.
6.0 Future Efforts
The North Carolina Coastal Federation will take the primary lead in developing the TMDL Implementation Plan. Actual TMDL implementation will be dependent upon funding sources. The
NCCF has completed several projects to date which will contribute to reducing fecal coliform loads
in the watershed, including education and outreach programs and the installation of stormwater BMPs. Possible grant funding sources for TMDL implementation strategies include the Section 319
fund administered by DWQ and the Clean Water Management Trust Fund among others.
7.0 Public Participation
A draft of the TMDL was publicly noticed through various means. The TMDL was public noticed in the local newspaper (City of Wilmington Star News) on July 14. The TMDL was also public noticed
on July 14, 2010 through the North Carolina Water Resources Research Institute (WRRI) email listserve, the DWQ mailing list of interested parties, and on the DWQ TMDL website. In addition a
press release was given by NCCF on July 13. An article entitled “Pollution report first step in
reclaiming Lockwood Folly” was also published in the City of Wilmington StarNews Online newspaper on July 21, 2010 (Appendix F). Finally, the TMDL was available on DWQ’s website
http://h2o.enr.state.nc.us/tmdl/ during the comment period. The public comment period lasted from July 13, 2010 until August 13, 2010.
The DWQ received written Comments during the comment period. Summaries of the comments
and DWQ’s response are presented in Appendix G.
Lockwoods Folly River Fecal Coliform TMDL
32
A stakeholder process has been conducted as a part of this project. To date, four presentations have been made to the County Commission and its planning board, as well as citizens. Public
education and outreach has also been conducted, including a media campaign, public education brochures, a tabloid summarizing the Lockwood Folly Roundtable Strategies, and local volunteer
involvement in water quality monitoring. Examples of materials used for public education and
outreach are included in Appendix H. Additionally a technical working group consisting of project partners, local decision makers, and representatives of the various interest groups and agencies
has provided guidance and oversight of the project. This group has met four times to date to review progress of the TMDL development and Implementation Plan strategies.
Lockwoods Folly River Fecal Coliform TMDL
33
8.0 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:
Adugna Kebede, Modeler
e-mail: [e-mail]
Kathy Stecker
e-mail: [e-mail]
Lockwoods Folly River Fecal Coliform TMDL
34
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USACE 2008. Hydrologic Modeling System HEC-HMS User’s Manual Version 3.3. US Army Corps
of Engineers. Hydrologic Engineering Center. Davis, California.
USEPA 1991. Guidance for Water Quality-Based Decisions: The TMDL Process. EPA 440/4-91-
001. United States Environmental Protection Agency. Washington, DC.
USEPA 1998. Report of the Federal Advisory Committee on the Total Maximum Daily Load (TMDL)
Program. EPA 100-R-98-006. United States Environmental Protection Agency. Washington, DC.
USEPA 2000. Bacteria Indicator Tool User's Guide. EPA823B01003. United States Environmental Protection Agency. Washington, DC.
Lockwoods Folly River Fecal Coliform TMDL
36
VA DEQ 2002. Fecal Coliform TMDL for Dodd Creek Watershed, Virginia, June 2002.
VIMS, 2004: Technical Memorandum for Fecal Coliform TMDL of Shellfish Harvesting areas.
Lockwoods Folly River Fecal Coliform TMDL
37
Appendix A. Observed Time Series Plots and Water Quality Data
The most recent fecal coliform observation data (2004-2009) for all monitoring sites within the Lockwoods Folly estuary along with their 30-month median and 90th percentiles are presented in
Figure A1 to Figure A9. Table A1 following the graphs presents the observed fecal coliform data for
samples collected at the nine sites from 2004 to 2009.
1
10
100
1000
1/1/2004 10/27/2004 8/23/2005 6/19/2006 4/15/2007 2/9/2008 12/5/2008 10/1/2009
Fe
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Date
Site 5A
90th percentile standard Median standard Measured
30-sample 90th 30-sample median

Figure A1. Time series plot of fecal coliform observations at Site 5A

Lockwoods Folly River Fecal Coliform TMDL
38
1
10
100
1000
1/1/2004 10/27/2004 8/23/2005 6/19/2006 4/15/2007 2/9/2008 12/5/2008 10/1/2009
Fe
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Date
Site 6A
90th percentile standard Median standard Measured
30-sample 90th 30-sample median

Figure A2. Time series plot of fecal coliform observations at Site 6A
1
10
100
1000
1/1/2004 10/27/2004 8/23/2005 6/19/2006 4/15/2007 2/9/2008 12/5/2008 10/1/2009
Fe
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Date
Site 7
90th percentile standard Median standard Measured
30-sample 90th 30-sample median

Figure A3. Time series plot of fecal coliform observations at Site 7
Lockwoods Folly River Fecal Coliform TMDL
39
1
10
100
1000
10000
1/1/2004 10/27/2004 8/23/2005 6/19/2006 4/15/2007 2/9/2008 12/5/2008 10/1/2009
Fe
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Date
Site 7A
90th percentile standard Median standard Measured
30-sample 90th 30-sample median

Figure A4. Time series plot of fecal coliform observations at Site 7A
1
10
100
1000
1/1/2004 10/27/2004 8/23/2005 6/19/2006 4/15/2007 2/9/2008 12/5/2008 10/1/2009
Fe
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Date
Site 8
90th percentile standard Median standard Measured
30-sample 90th 30-sample median

Figure A5. Time series plot of fecal coliform observations at Site 8
Lockwoods Folly River Fecal Coliform TMDL
40
1
10
100
1000
1/1/2004 10/27/2004 8/23/2005 6/19/2006 4/15/2007 2/9/2008 12/5/2008 10/1/2009
Fe
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Date
Site 10
90th percentile standard Median standard Measured
30-sample 90th 30-sample median

Figure A6. Time series plot of fecal coliform observations at Site 10
1
10
100
1000
1/1/2004 10/27/2004 8/23/2005 6/19/2006 4/15/2007 2/9/2008 12/5/2008 10/1/2009
Fe
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Date
Site 13
90th percentile standard Median standard Measured
30-sample 90th 30-sample median

Figure A7. Time series plot of fecal coliform observations at Site 13
Lockwoods Folly River Fecal Coliform TMDL
41
1
10
100
1000
1/1/2004 10/27/2004 8/23/2005 6/19/2006 4/15/2007 2/9/2008 12/5/2008 10/1/2009
Fe
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Date
Site 14A
90th percentile standard Median standard Measured
30-sample 90th 30-sample median

Figure A8. Time series plot of fecal coliform observations at Site 14A
1
10
100
1000
1/1/2004 10/27/2004 8/23/2005 6/19/2006 4/15/2007 2/9/2008 12/5/2008 10/1/2009
Fe
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Date
Site 14B
90th percentile standard Median standard Measured
30-sample 90th 30-sample median

Figure A9. Time series plot of fecal coliform observations at Site 14B
Lockwoods Folly River Fecal Coliform TMDL
42
Table A1. Observed data at all monitoring stations in the Lockwoods Folly estuary (2004-2009)
DATE Station no. TIDE Salinity (ppt) FC (cts/100mL)
1/7/2002 5A Early FLD 31 350.0
4/2/2002 5A 1/3 EBB 35 1.7
6/17/2002 5A 1/2 FLD BROKEN 49.0
7/18/2002 5A Late EBB 32 130.0
9/19/2002 5A 1/2 EBB 26 130.0
10/30/2002 5A 1/3 FLD 21 240.0
1/7/2003 5A 1/2 FLD 36 49.0
2/26/2003 5A 2/3 EBB 28 33.0
5/5/2003 5A 2/3 FLD 29 110.0
7/8/2003 5A Early FLD 20 79.0
8/19/2003 5A 1/3 FLD 15 13.0
10/22/2003 5A 1/2 EBB 32 23.0
2/9/2004 5A Early EBB 34 2.0
4/27/2004 5A Late EBB>Early FLD 28 33.0
7/16/2004 5A 1/3 EBB 35 1.7
8/9/2004 5A 1/4 FLD 22 23.0
10/13/2004 5A 1/4 EBB 32 6.8
10/26/2004 5A 1/3 EBB 35 2.0
11/8/2004 5A 130.0
1/3/2005 5A 1/2 FLD 31 7.8
2/14/2005 5A 2/3 FLD 32 2.0
4/28/2005 5A 2/3 FLD 33 4.5
5/3/2005 5A Late EBB 31 13.0
6/13/2005 5A 1/3 FLD 30 6.1
6/28/2005 5A 1/3 FLD 35 7.8
1/23/2006 5A 1/3 FLD 30 79.0
2/16/2006 5A 1/3 EBB 32 7.8
3/20/2006 5A 2/3 FLD 35 1.7
4/25/2006 5A 2/3 EBB 35 33.0
7/10/2006 5A 1/2 EBB 35 33.0
7/31/2006 5A 1/3 FLD 35 14.0
2/28/2007 5A 1/2 EBB 30 7.8
4/9/2007 5A 1/2 FLD 34 4.5
5/16/2007 5A 1/3 EBB 35 4.0
6/14/2007 5A 1/3 EBB 36 2.0
8/13/2007 5A LATE FLOOD 36 4.5
9/4/2007 5A 1/4 FLOOD 35 7.8
2/6/2008 5A 1/2 ebb 35 13.0
5/27/2008 5A 1/4 flood 35 7.8
7/8/2008 5A 1/4 FLOOD 37 13.0
8/5/2008 5A 3/4 flood 36 7.8
9/24/2008 5A late ebb 34 22.0
10/22/2008 5A late ebb 32 23.0
2/5/2009 5A late ebb 24 17.0
4/7/2009 5A 1/4 EBB 31 33.0
Lockwoods Folly River Fecal Coliform TMDL
43
DATE Station no. TIDE
Salinity
(ppt)
FC
(cts/100mL)
5/13/2009 5A 3/4 EBB 35 13.0
7/15/2009 5A EARLY FLD 34 17.0
8/10/2009 5A 3/4 FLD 36 2.0
9/9/2009 5A LATE FLD 35 4.5
3/14/2002 6A 540.0
3/18/2002 6A 6.8
7/16/2004 6A 1/3 EBB 35 1.7
8/9/2004 6A 1/4 FLD 26 79.0
10/13/2004 6A 1/4 EBB 32 2.0
10/26/2004 6A 1/3 EBB 35 4.5
1/3/2005 6A 1/2 FLD 32 7.8
2/14/2005 6A 2/3 FLD 34 4.0
4/4/2005 6A 920.0
4/28/2005 6A 2/3 FLD 34 4.5
5/3/2005 6A Late EBB 32 33.0
6/13/2005 6A 1/3 FLD 32 4.0
6/28/2005 6A 1/3 FLD 35 6.8
1/23/2006 6A 1/3 FLD 32 14.0
2/16/2006 6A 1/3 EBB 35 4.0
3/20/2006 6A 2/3 FLD 35 1.7
4/25/2006 6A 2/3 EBB 34 33.0
7/10/2006 6A 1/2 EBB 35 4.5
7/31/2006 6A 1/3 FLD 35 4.5
2/28/2007 6A 1/2 EBB 32 6.8
4/9/2007 6A 1/2 FLD 34 4.5
5/16/2007 6A 1/3 EBB 36 1.7
6/14/2007 6A 1/3 EBB 36 2.0
8/13/2007 6A LATE FLOOD 36 2.0
9/4/2007 6A 1/4 FLOOD 36 13.0
2/6/2008 6A 1/2 ebb 35 1.7
5/27/2008 6A 1/4 flood 35 2.0
7/8/2008 6A 1/4 FLOOD 38 2.0
8/5/2008 6A 3/4 flood 36 1.7
9/24/2008 6A late ebb 34 79.0
10/22/2008 6A late ebb 34 49.0
2/5/2009 6A late ebb 28 22.0
4/7/2009 6A 1/4 EBB 33 7.8
5/13/2009 6A 3/4 EBB 35 6.8
7/15/2009 6A EARLY FLD 35 6.8
8/10/2009 6A 3/4 FLD 36 1.7
9/9/2009 6A LATE FLD 36 4.5
6/9/2004 7A 46.0
6/11/2004 7A 7.8
6/14/2004 7A 4.5
6/16/2004 7A 1.7
7/6/2004 7A 2.0
7/16/2004 7A 1/3 EBB 35 2.0
Lockwoods Folly River Fecal Coliform TMDL
44
DATE Station no. TIDE
Salinity
(ppt)
FC
(cts/100mL)
8/9/2004 7A 1/4 FLD 28 23.0
10/13/2004 7A 1/4 EBB 32 1.7
10/26/2004 7A 1/3 EBB 35 4.5
11/16/2004 7A 1.7
11/30/2004 7A 1.7
1/3/2005 7A 1/2 FLD 33 2.0
2/14/2005 7A 2/3 FLD 34 1.7
3/2/2005 7A 2.0
4/4/2005 7A 1600.0
4/6/2005 7A 14.0
4/10/2005 7A 2.0
4/28/2005 7A 2/3 FLD 34 1.7
5/3/2005 7A Late EBB 32 7.8
6/13/2005 7A 1/3 FLD 33 4.5
6/28/2005 7A 1/3 FLD 35 1.8
7/1/2005 7A 130.0
7/5/2005 7A 49.0
7/7/2005 7A 1.7
8/4/2005 7A 79.0
8/9/2005 7A 1.8
8/11/2005 7A 1.7
8/29/2005 7A 79.0
9/1/2005 7A 33.0
9/6/2005 7A 2.0
9/26/2005 7A 110.0
9/29/2005 7A 49.0
10/3/2005 7A 1.7
10/8/2005 7A 2.0
11/29/2005 7A 130.0
12/1/2005 7A 33.0
12/5/2005 7A 2.0
12/21/2005 7A 1.7
1/23/2006 7A 1/3 FLD 33 22.0
2/16/2006 7A 1/3 EBB 35 1.7
3/1/2006 7A 1.8
3/20/2006 7A 2/3 FLD 35 1.7
4/25/2006 7A 2/3 EBB 34 17.0
5/1/2006 7A 2.0
7/10/2006 7A 1/2 EBB 36 2.0
7/27/2006 7A 1.7
7/31/2006 7A 1/3 FLD 35 4.0
8/10/2006 7A 7.8
9/12/2006 7A 46.0
9/15/2006 7A 540.0
9/18/2006 7A 170.0
9/21/2006 7A 2.0
10/12/2006 7A 2.0
Lockwoods Folly River Fecal Coliform TMDL
45
DATE Station no. TIDE
Salinity
(ppt)
FC
(cts/100mL)
10/31/2006 7A 130.0
11/3/2006 7A 7.8
11/13/2006 7A 70.0
11/15/2006 7A 110.0
11/19/2006 7A 1.7
11/27/2006 7A 33.0
11/29/2006 7A 920.0
12/5/2006 7A 7.5
1/2/2007 7A 79.0
1/4/2007 7A 1.7
2/5/2007 7A 1.7
2/28/2007 7A 1/2 EBB 32 1.7
4/9/2007 7A 1/2 FLD 35 4.5
5/16/2007 7A 1/3 EBB 35 1.7
6/6/2007 7A 2.0
6/14/2007 7A 1/3 EBB 36 2.0
8/13/2007 7A LATE FLOOD 36 1.7
9/4/2007 7A 1/4 FLOOD 37 17.0
10/30/2007 7A 1.7
12/18/2007 7A 79.0
12/20/2007 7A 1.8
1/22/2008 7A 2.0
2/6/2008 7A 1/2 ebb 35 1.7
2/21/2008 7A 1.7
2/25/2008 7A 2.0
3/19/2008 7A 1.7
4/9/2008 7A 1.7
4/23/2008 7A 1.7
5/15/2008 7A 17.0
5/19/2008 7A 1.7
5/27/2008 7A 1/4 flood 35 1.8
6/24/2008 7A 2.0
7/8/2008 7A 1/4 FLOOD 38 4.0
8/5/2008 7A 3/4 flood 36 1.7
8/18/2008 7A 4.5
9/9/2008 7A 23.0
9/11/2008 7A 23.0
9/16/2008 7A 1.7
9/24/2008 7A late ebb 34 13.0
9/30/2008 7A 1.7
10/22/2008 7A late ebb 34 22.0
10/28/2008 7A 2.0
11/6/2008 7A 49.0
11/9/2008 7A 23.0
11/12/2008 7A 1.8
11/17/2008 7A 1.7
12/2/2008 7A 1.7
Lockwoods Folly River Fecal Coliform TMDL
46
DATE Station no. TIDE
Salinity
(ppt)
FC
(cts/100mL)
2/5/2009 7A late ebb 30 11.0
2/23/2009 7A 6.8
3/4/2009 7A 46.0
3/6/2009 7A 240.0
3/9/2009 7A 1.7
4/7/2009 7A 1/4 EBB 32 4.5
5/11/2009 7A 1.7
5/13/2009 7A 3/4 EBB 35 2.0
5/22/2009 7A 1.7
6/18/2009 7A 17.0
7/15/2009 7A EARLY FLD 35 4.5
8/10/2009 7A 3/4 FLD 36 1.7
9/9/2009 7A LATE FLD 36 1.7
10/1/2009 7A 7.8
10/7/2009 7A 1.7
1/7/2002 7 Early FLD 37 170.0
4/2/2002 7 1/3 EBB 37 1.7
6/17/2002 7 1/2 FLD BROKEN 2.0
7/18/2002 7 Late EBB 35 23.0
9/19/2002 7 1/2 EBB 31 70.0
10/30/2002 7 1/3 FLD 32 33.0
1/7/2003 7 1/2 FLD 36 7.8
2/26/2003 7 2/3 EBB 32 17.0
5/5/2003 7 2/3 FLD 34 1.7
7/8/2003 7 Early FLD 30 33.0
8/19/2003 7 1/3 FLD 25 23.0
10/22/2003 7 1/2 EBB 35 22.0
2/9/2004 7 Early EBB 36 1.7
4/27/2004 7 Late EBB>Early FLD 30 70.0
6/9/2004 7 33.0
6/11/2004 7 1.8
6/14/2004 7 1.8
6/16/2004 7 1.7
7/6/2004 7 1.7
7/16/2004 7 1/3 EBB 35 2.0
8/9/2004 7 1/4 FLD 30 6.8
10/13/2004 7 1/4 EBB 32 17.0
10/26/2004 7 1/3 EBB 35 2.0
11/16/2004 7 4.5
11/30/2004 7 1.7
1/3/2005 7 1/2 FLD 32 1.7
2/14/2005 7 2/3 FLD 34 2.0
3/2/2005 7 2.0
4/6/2005 7 49.0
4/10/2005 7 4.0
4/28/2005 7 2/3 FLD 34 1.8
Lockwoods Folly River Fecal Coliform TMDL
47
DATE Station no. TIDE
Salinity
(ppt)
FC
(cts/100mL)
5/3/2005 7 Late EBB 32 9.2
5/9/2005 7 79.0
5/11/2005 7 1.7
6/13/2005 7 1/3 FLD 33 1.8
6/28/2005 7 1/3 FLD 35 2.0
7/1/2005 7 79.0
7/5/2005 7 49.0
7/7/2005 7 4.5
8/4/2005 7 49.0
8/9/2005 7 1.7
8/11/2005 7 1.7
8/29/2005 7 140.0
9/1/2005 7 49.0
9/6/2005 7 2.0
9/26/2005 7 140.0
9/29/2005 7 33.0
10/3/2005 7 4.5
10/8/2005 7 4.0
11/29/2005 7 130.0
12/1/2005 7 23.0
12/5/2005 7 1.7
12/21/2005 7 2.0
1/23/2006 7 1/3 FLD 33 79.0
2/16/2006 7 1/3 EBB 35 1.7
3/1/2006 7 2.0
3/20/2006 7 2/3 FLD 35 1.7
4/25/2006 7 2/3 EBB 35 6.8
5/1/2006 7 1.0
7/10/2006 7 1/2 EBB 35 7.8
7/27/2006 7 1.7
7/31/2006 7 1/3 FLD 35 6.8
8/10/2006 7 6.8
9/12/2006 7 49.0
9/15/2006 7 240.0
9/18/2006 7 49.0
9/21/2006 7 6.8
10/12/2006 7 2.0
10/31/2006 7 350.0
11/3/2006 7 7.8
11/13/2006 7 49.0
11/15/2006 7 79.0
11/19/2006 7 4.0
11/27/2006 7 79.0
11/29/2006 7 130.0
12/5/2006 7 4.5
1/2/2007 7 33.0
1/4/2007 7 7.8
Lockwoods Folly River Fecal Coliform TMDL
48
DATE Station no. TIDE
Salinity
(ppt)
FC
(cts/100mL)
2/5/2007 7 1.7
2/28/2007 7 1/2 EBB 30 7.8
4/9/2007 7 1/2 FLD 35 2.0
5/16/2007 7 1/3 EBB 35 2.0
6/6/2007 7 4.5
6/14/2007 7 1/3 EBB 36 2.0
8/13/2007 7 LATE FLOOD 36 1.7
9/4/2007 7 1/4 FLOOD 36 33.0
10/30/2007 7 2.0
12/18/2007 7 21.0
12/20/2007 7 7.8
1/22/2008 7 1.7
2/6/2008 7 1/2 ebb 35 1.8
2/21/2008 7 1.7
2/25/2008 7 1.7
3/19/2008 7 1.7
4/9/2008 7 1.8
4/23/2008 7 1.7
5/15/2008 7 34.0
5/19/2008 7 1.7
5/27/2008 7 1/4 flood 35 2.0
6/24/2008 7 2.0
7/8/2008 7 1/4 FLOOD 38 2.0
8/5/2008 7 3/4 flood 36 1.7
8/18/2008 7 4.5
9/9/2008 7 49.0
9/11/2008 7 33.0
9/16/2008 7 1.7
9/24/2008 7 late ebb 34 13.0
9/30/2008 7 2.0
10/22/2008 7 late ebb 35 49.0
10/28/2008 7 1.7
11/6/2008 7 33.0
11/9/2008 7 13.0
11/12/2008 7 4.0
11/17/2008 7 2.0
12/2/2008 7 1.7
2/5/2009 7 late ebb 30 7.8
2/23/2009 7 7.8
3/4/2009 7 79.0
3/6/2009 7 170.0
3/9/2009 7 4.5
4/7/2009 7 1/4 EBB 34 4.5
5/11/2009 7 1.7
5/13/2009 7 3/4 EBB 35 1.7
5/22/2009 7 1.7
6/18/2009 7 17.0
Lockwoods Folly River Fecal Coliform TMDL
49
DATE Station no. TIDE
Salinity
(ppt)
FC
(cts/100mL)
7/15/2009 7 EARLY FLD 38 2.0
8/10/2009 7 3/4 FLD 36 1.7
9/9/2009 7 LATE FLD 36 1.7
10/1/2009 7 33.0
10/7/2009 7 1.7
1/7/2002 8 Early FLD 37 79.0
2/13/2002 8 2.0
3/14/2002 8 33.0
3/18/2002 8 2.0
4/2/2002 8 1/3 EBB 37 1.7
6/17/2002 8 1/2 FLD BROKEN 23.0
7/18/2002 8 Late EBB 37 17.0
9/19/2002 8 1/2 EBB 37 22.0
9/26/2002 8 4.5
10/14/2002 8 49.0
10/17/2002 8 79.0
10/21/2002 8 33.0
10/30/2002 8 1/3 FLD 33 46.0
1/7/2003 8 1/2 FLD 36 7.8
2/19/2003 8 1.7
2/26/2003 8 2/3 EBB 34 23.0
3/26/2003 8 33.0
3/28/2003 8 46.0
4/1/2003 8 1.8
4/15/2003 8 23.0
4/16/2003 8 33.0
5/5/2003 8 2/3 FLD 33 11.0
5/28/2003 8 79.0
5/30/2003 8 27.0
7/8/2003 8 Early FLD 36 11.0
8/19/2003 8 1/3 FLD 24 13.0
9/22/2003 8 7.8
9/25/2003 8 1.7
10/14/2003 8 7.8
10/22/2003 8 1/2 EBB 35 110.0
10/31/2003 8 79.0
11/3/2003 8 49.0
11/4/2003 8 110.0
11/7/2003 8 79.0
11/10/2003 8 2.0
12/16/2003 8 240.0
12/18/2003 8 350.0
12/21/2003 8 17.0
1/29/2004 8 79.0
2/2/2004 8 11.0
2/9/2004 8 Early EBB 36 1.7
3/1/2004 8 170.0
Lockwoods Folly River Fecal Coliform TMDL
50
DATE Station no. TIDE
Salinity
(ppt)
FC
(cts/100mL)
3/3/2004 8 27.0
3/5/2004 8 49.0
3/8/2004 8 17.0
4/27/2004 8
Late EBB>Early
FLD 30 170.0
4/30/2004 8 49.0
5/6/2004 8 23.0
6/9/2004 8 33.0
6/11/2004 8 49.0
6/14/2004 8 79.0
6/16/2004 8 13.0
7/6/2004 8 1.7
7/16/2004 8 1/3 EBB 36 11.0
8/9/2004 8 1/4 FLD 35 33.0
8/19/2004 8 4.5
10/13/2004 8 1/4 EBB 32 4.5
10/26/2004 8 1/3 EBB 32 2.0
11/16/2004 8 2.0
11/30/2004 8 2.0
1/3/2005 8 1/2 FLD 31 4.5
2/14/2005 8 2/3 FLD 33 4.5
3/2/2005 8 2.0
4/4/2005 8 920.0
4/6/2005 8 14.0
4/10/2005 8 2.0
4/28/2005 8 2/3 FLD 34 2.0
5/3/2005 8 Late EBB 34 4.5
6/13/2005 8 1/3 FLD 29 4.0
6/28/2005 8 1/3 FLD 35 3.7
7/1/2005 8 130.0
7/5/2005 8 22.0
7/7/2005 8 4.5
8/4/2005 8 49.0
8/9/2005 8 4.8
8/11/2005 8 4.5
8/29/2005 8 240.0
9/1/2005 8 79.0
9/6/2005 8 2.0
9/26/2005 8 170.0
9/29/2005 8 130.0
10/3/2005 8 1.7
10/8/2005 8 4.5
1/23/2006 8 1/3 FLD 32 22.0
2/16/2006 8 1/3 EBB 35 1.7
3/1/2006 8 4.5
3/20/2006 8 2/3 FLD 35 1.7
4/25/2006 8 2/3 EBB 34 49.0
Lockwoods Folly River Fecal Coliform TMDL
51
DATE Station no. TIDE
Salinity
(ppt)
FC
(cts/100mL)
5/1/2006 8 1.0
7/10/2006 8 1/2 EBB 35 14.0
7/31/2006 8 1/3 FLD 34 11.0
2/28/2007 8 1/2 EBB 32 6.8
4/9/2007 8 1/2 FLD 35 2.0
5/16/2007 8 1/3 EBB 35 1.7
6/14/2007 8 1/3 EBB 36 1.7
8/13/2007 8 LATE FLOOD 36 1.7
9/4/2007 8 1/4 FLOOD 36 27.0
2/6/2008 8 1/2 ebb 35 1.7
5/27/2008 8 1/4 flood 35 6.8
7/8/2008 8 1/4 FLOOD 37 7.8
8/5/2008 8 3/4 flood 36 2.0
9/24/2008 8 late ebb 35 7.8
10/22/2008 8 late ebb 35 49.0
2/5/2009 8 late ebb 32 11.0
4/7/2009 8 1/4 EBB 35 79.0
5/13/2009 8 3/4 EBB 36 1.7
7/15/2009 8 EARLY FLD 35 17.0
8/10/2009 8 3/4 FLD 38 1.7
9/9/2009 8 LATE FLD 38 1.7
1/7/2002 10 Early FLD 37 130.0
4/2/2002 10 1/3 EBB 37 4.5
6/17/2002 10 1/2 FLD BROKEN 2.0
7/18/2002 10 Late EBB 36 17.0
9/19/2002 10 1/2 EBB 34 23.0
10/30/2002 10 1/3 FLD 33 49.0
1/7/2003 10 1/2 FLD 35 33.0
2/26/2003 10 2/3 EBB 30 4.5
5/5/2003 10 2/3 FLD 33 13.0
7/8/2003 10 Early FLD 30 33.0
8/19/2003 10 1/3 FLD 23 17.0
10/22/2003 10 1/2 EBB 35 46.0
2/9/2004 10 Early EBB 36 2.0
4/27/2004 10
Late EBB>Early
FLD 30 13.0
7/16/2004 10 1/3 EBB 35 2.0
8/9/2004 10 1/4 FLD 30 17.0
10/13/2004 10 1/4 EBB 32 2.0
10/26/2004 10 1/3 EBB 35 2.0
1/3/2005 10 1/2 FLD 34 4.5
2/14/2005 10 2/3 FLD 34 1.7
4/4/2005 10 540.0
4/28/2005 10 2/3 FLD 33 1.7
5/3/2005 10 Late EBB 34 4.5
6/13/2005 10 1/3 FLD 33 4.5
6/28/2005 10 1/3 FLD 35 2.0
Lockwoods Folly River Fecal Coliform TMDL
52
DATE Station no. TIDE
Salinity
(ppt)
FC
(cts/100mL)
1/23/2006 10 1/3 FLD 32 49.0
2/16/2006 10 1/3 EBB 35 4.5
3/20/2006 10 2/3 FLD 34 1.7
4/25/2006 10 2/3 EBB 34 70.0
7/10/2006 10 1/2 EBB 35 46.0
7/31/2006 10 1/3 FLD 35 4.0
2/28/2007 10 1/2 EBB 26 4.0
4/9/2007 10 1/2 FLD 35 4.5
5/16/2007 10 1/3 EBB 35 1.8
6/14/2007 10 1/3 EBB 36 2.0
8/13/2007 10 LATE FLOOD 36 4.5
9/4/2007 10 1/4 FLOOD 36 22.0
2/6/2008 10 1/2 ebb 35 1.7
5/27/2008 10 1/4 flood 35 1.8
7/8/2008 10 1/4 FLOOD 38 4.5
8/5/2008 10 3/4 flood 36 1.7
9/24/2008 10 late ebb 34 13.0
10/22/2008 10 late ebb 35 11.0
2/5/2009 10 late ebb 31 11.0
2/5/2009 10 LATE EBB 31 11.0
4/7/2009 10 1/4 EBB 32 14.0
5/13/2009 10 3/4 EBB 35 11.0
7/15/2009 10 EARLY FLD 37 4.0
8/10/2009 10 3/4 FLD 37 1.7
9/9/2009 10 LATE FLD 37 1.7
1/7/2002 13 Early FLD 37 49.0
4/2/2002 13 1/3 EBB 37 1.7
6/17/2002 13 1/2 FLD BROKEN 4.5
7/18/2002 13 Late EBB 36 79.0
9/4/2002 13 13.0
9/19/2002 13 1/2 EBB 35 17.0
9/26/2002 13 2.0
10/14/2002 13 33.0
10/17/2002 13 23.0
10/30/2002 13 1/3 FLD 35 49.0
1/7/2003 13 1/2 FLD 36 2.0
2/19/2003 13 2.0
2/26/2003 13 2/3 EBB 31 11.0
3/26/2003 13 350.0
3/28/2003 13 23.0
4/1/2003 13 2.0
4/15/2003 13 23.0
4/16/2003 13 17.0
5/5/2003 13 2/3 FLD 34 2.0
5/28/2003 13 33.0
5/30/2003 13 46.0
7/8/2003 13 Early FLD 34 17.0
Lockwoods Folly River Fecal Coliform TMDL
53
DATE Station no. TIDE
Salinity
(ppt)
FC
(cts/100mL)
8/19/2003 13 1/3 FLD 27 22.0
9/22/2003 13 17.0
9/25/2003 13 2.0
10/14/2003 13 2.0
10/22/2003 13 1/2 EBB 35 21.0
10/31/2003 13 11.0
11/3/2003 13 110.0
11/4/2003 13 13.0
11/7/2003 13 26.0
11/10/2003 13 7.8
12/16/2003 13 2.0
12/18/2003 13 110.0
12/21/2003 13 13.0
2/9/2004 13 Early EBB 36 1.7
4/27/2004 13
Late EBB>Early
FLD 30 7.8
5/6/2004 13 6.8
7/16/2004 13 1/3 EBB 35 2.0
8/9/2004 13 1/4 FLD 32 11.0
8/19/2004 13 2.0
10/13/2004 13 1/4 EBB 32 13.0
10/26/2004 13 1/3 EBB 34 4.5
1/3/2005 13 1/2 FLD 32 2.0
2/14/2005 13 2/3 FLD 32 4.5
4/28/2005 13 2/3 FLD 33 1.7
5/3/2005 13 Late EBB 32 6.1
6/13/2005 13 1/3 FLD 34 1.7
6/28/2005 13 1/3 FLD 35 1.7
9/29/2005 13 4.5
10/8/2005 13 1.7
11/29/2005 13 33.0
12/1/2005 13 350.0
12/5/2005 13 1.7
1/23/2006 13 1/3 FLD 35 6.8
2/16/2006 13 1/3 EBB 35 1.7
3/20/2006 13 2/3 FLD 35 1.7
4/25/2006 13 2/3 EBB 35 23.0
7/10/2006 13 1/2 EBB 36 4.0
7/31/2006 13 1/3 FLD 35 6.1
9/12/2006 13 2.0
10/12/2006 13 2.0
10/31/2006 13 130.0
11/3/2006 13 22.0
11/6/2006 13 1.8
11/13/2006 13 13.0
1/2/2007 13 33.0
1/4/2007 13 4.0
Lockwoods Folly River Fecal Coliform TMDL
54
DATE Station no. TIDE
Salinity
(ppt)
FC
(cts/100mL)
2/28/2007 13 1/2 EBB 32 4.5
4/9/2007 13 1/2 FLD 34 1.7
5/16/2007 13 1/3 EBB 35 2.0
6/14/2007 13 1/3 EBB 36 4.5
8/13/2007 13 LATE FLOOD 36 1.7
9/4/2007 13 1/4 FLOOD 35 2.0
2/6/2008 13 1/2 ebb 35 4.5
5/27/2008 13 1/4 flood 35 2.0
7/8/2008 13 1/4 FLOOD 38 1.7
8/5/2008 13 3/4 flood 36 1.7
9/24/2008 13 late ebb 34 11.0
10/22/2008 13 late ebb 34 7.8
10/28/2008 13 7.8
2/5/2009 13 late ebb 32 4.0
4/7/2009 13 1/4 EBB 33 2.0
5/13/2009 13 3/4 EBB 34 6.8
7/15/2009 13 EARLY FLD 35 1.7
8/10/2009 13 3/4 FLD 37 1.7
9/9/2009 13 LATE FLD 35 1.7
10/1/2009 13 17.0
7/16/2004 14A 1/3 EBB 35 4.5
8/9/2004 14A 1/4 FLD 26 17.0
8/19/2004 14A 4.5
10/13/2004 14A 1/4 EBB 32 1.7
10/26/2004 14A 1/3 EBB 35 2.0
1/3/2005 14A 1/2 FLD 32 1.7
2/14/2005 14A 2/3 FLD 34 1.7
4/28/2005 14A 2/3 FLD 34 1.7
5/3/2005 14A Late EBB 32 17.0
5/9/2005 14A 110.0
5/11/2005 14A 13.0
6/13/2005 14A 1/3 FLD 32 6.8
6/28/2005 14A 1/3 FLD 35 4.5
9/22/2005 14A 23.0
1/23/2006 14A 1/3 FLD 32 130.0
2/16/2006 14A 1/3 EBB 35 2.0
3/20/2006 14A 2/3 FLD 35 4.5
4/25/2006 14A 2/3 EBB 35 6.8
7/10/2006 14A 1/2 EBB 36 4.5
7/31/2006 14A 1/3 FLD 35 7.8
2/28/2007 14A 1/2 EBB 32 4.5
4/9/2007 14A 1/2 FLD 35 2.0
5/16/2007 14A 1/3 EBB 35 1.7
6/14/2007 14A 1/3 EBB 36 2.0
8/13/2007 14A LATE FLOOD 36 2.0
9/4/2007 14A 1/4 FLOOD 36 7.8
12/20/2007 14A 17
Lockwoods Folly River Fecal Coliform TMDL
55
DATE Station no. TIDE
Salinity
(ppt)
FC
(cts/100mL)
12/21/2007 14A 10
1/14/2008 14A 2
2/1/2008 14A 5
2/6/2008 14A 1/2 ebb 35 1.7
3/5/2008 14A 7
3/20/2008 14A 6
5/15/2008 14A 20
5/27/2008 14A 1/4 flood 35 6.1
5/29/2008 14A 73
6/24/2008 14A 10
7/8/2008 14A 1/4 FLOOD 38 6.8
7/21/2008 14A 10
7/29/2008 14A 10
8/5/2008 14A 3/4 flood 36 4.5
8/14/2008 14A 73
8/28/2008 14A 19
9/24/2008 14A late ebb 34 17.0
9/26/2008 14A 37
10/22/2008 14A late ebb 35 95.0
11/4/2008 14A 2
12/12/2008 14A 10
2/5/2009 14A late ebb 28 79.0
4/7/2009 14A 1/4 EBB 34 7.8
5/13/2009 14A 3/4 EBB 35 6.8
7/15/2009 14A EARLY FLD 35 2.0
8/10/2009 14A 3/4 FLD 37 1.7
9/9/2009 14A LATE FLD 37 2.0
7/16/2004 14B 1/3 EBB 35 1.7
8/9/2004 14B 1/4 FLD 30 7.8
10/13/2004 14B 1/4 EBB 32 2.0
10/26/2004 14B 1/3 EBB 34 1.7
1/3/2005 14B 1/2 FLD 31 4.5
2/14/2005 14B 2/3 FLD 32 1.7
4/28/2005 14B 2/3 FLD 33 11.0
5/3/2005 14B Late EBB 32 7.8
6/13/2005 14B 1/3 FLD 31 1.8
6/28/2005 14B 1/3 FLD 35 17.0
1/23/2006 14B 1/3 FLD 35 11.0
2/16/2006 14B 1/3 EBB 35 1.7
3/20/2006 14B 2/3 FLD 35 1.7
4/25/2006 14B 2/3 EBB 34 33.0
7/10/2006 14B 1/2 EBB 35 33.0
7/31/2006 14B 1/3 FLD 35 17.0
2/28/2007 14B 1/2 EBB 31 14.0
4/9/2007 14B 1/2 FLD 35 4.5
5/16/2007 14B 1/3 EBB 35 2.0
6/14/2007 14B 1/3 EBB 36 1.7
Lockwoods Folly River Fecal Coliform TMDL
56
DATE Station no. TIDE
Salinity
(ppt)
FC
(cts/100mL)
8/13/2007 14B LATE FLOOD 36 1.7
9/4/2007 14B 1/4 FLOOD 35 6.8
2/6/2008 14B 1/2 ebb 35 2.0
5/27/2008 14B 1/4 flood 35 7.8
7/8/2008 14B 1/4 FLOOD 38 11.0
8/5/2008 14B 3/4 flood 36 2.0
9/24/2008 14B late ebb 34 17.0
10/22/2008 14B late ebb 33 130.0
2/5/2009 14B late ebb 31 23.0
4/7/2009 14B 1/4 EBB 34 2.0
5/13/2009 14B 3/4 EBB 35 4.5
7/15/2009 14B EARLY FLD 34 2.0
8/10/2009 14B 3/4 FLD 36 1.7
9/9/2009 14B LATE FLD 36 4.5

Lockwoods Folly River Fecal Coliform TMDL
57
Appendix B. Tidal Prism Model Segmentation
Table B1. Geometry information of the Lockwoods Folly Estuary used for the TPWQM
Segment
Distance from mouth
(km)
High water volume
(m3 x 106)
Tidal prism
(m3 x 106) Depth (m)
M0_1 0.000 0.000 3.171 0.000
M0_2 1.830 3.179 0.783 1.062
M0_3 2.490 0.774 0.239 1.188
M0_4 3.100 0.271 0.000 0.828

Lockwoods Folly River Fecal Coliform TMDL
58
Appendix C. Nonpoint Source Assessment
Nonpoint sources of fecal coliform bacteria do not have one discharge point but occur over the entire length of a stream or waterbody. There are many types of nonpoint sources in watersheds
discharging to the restricted shellfish harvesting areas. The possible introductions of fecal coliform
bacteria to the land surface are through the manure spreading process, direct deposition from livestock during the grazing season, and excretions from pets and wildlife. As the runoff occurs
during rain events, surface runoff transports water and fecal coliform over the land surface and discharges to the restricted shellfish harvesting area. The deposition of nonhuman fecal coliform
directly to the restricted shellfish area occurs when livestock or wildlife have direct access to the
waterbody. Nonpoint source contributions to the bacterial levels from human activities generally arise from failing septic systems and their associated drain fields. The transport of fecal coliform
from land surface to the restricted shellfish harvesting area is dictated by the hydrology, soil type, land use, and topography of the watershed.
In order to determine the sources of fecal coliform contribution and reduction needed to achieve water quality criteria, and to allocate fecal coliform load among these sources, it is necessary to identify all existing sources. The nonpoint source assessment was conducted using available data
collected in the watershed. Multiple data sources were used to determine the potential sources of the fecal coliform load from the watershed. The data used for the source assessment are:
Land use data developed for the Lockwoods Folly LWP Detailed Assessment (2007) U.S. Census Data for Brunswick County Shoreline sanitary survey data
Wildlife population data Household pet statistics
Literature data on septic failure rates Stream coverage

Due to insufficient data sources, the source assessment method does not account for boat discharge, resuspension from bottom sediment, and the potential for regrowth of fecal coliform in
the estuary. It should be noted that the source loads calculated for this source assessment are an estimation of the fecal coliform loads available for runoff in the watershed, and do not estimate
direct loading from each source type to the Lockwoods Folly estuary.
Wildlife Contributions
It is generally assumed that wildlife in the watershed include the following: beaver, deer, birds and ducks, muskrat, raccoons, and wild turkey. Fecal coliform loading from wildlife occurs from either
excretion on land and subsequent runoff, or through direct deposition into waterbodies. Wildlife densities in the watershed were estimated based on data from sources such as the North Carolina
Wildlife Resources Commission, the North Carolina Department of Environment and Natural
Resources, the Virginia Department of Environmental Quality, and the Maryland Department of Natural Resources. Population densities and habitat requirements are summarized by species in
Table C1. These densities were applied to available habitat in the Lockwoods Folly watershed in order to estimate wildlife populations present. Habitat for each wildlife type in the watershed was
determined utilizing available land use data and GIS analysis techniques. Fecal coliform contributions were then estimated based on the number of wildlife and fecal coliform production rates, listed in Table C2. The analysis resulted in a total wildlife fecal coliform contribution of 3.10 x
Lockwoods Folly River Fecal Coliform TMDL
59
1013 counts per day.
Table C1. Wildlife habitat and densities
Wildlife Type Population Density Habitat Requirements
Beaver1
4.8 animals/mile of
stream Tidal and non-tidal regions
Deer3 0.035 animals/acre Entire watershed
Birds4 0.07 animals/acre Entire watershed
Duck2 0.039 animals/acre Entire watershed
Muskrat1 2.75 animals/acre Within 66 feet of streams and ponds
Raccoon1 0.07 animals/acre Within 600 feet of streams and ponds
Wild Turkey3 0.005 animals/acre Entire watershed excluding farmsteads and urban
1VA DEQ 2002, 2MD DNR 2003, 3NC WRC 2008, 4NC DENR 2007a

Table C2. Wildlife fecal coliform production rates
Source
Fecal Coliform
Production (cts/animal/day)
Beaver1 2.50E+08
Deer1 5.00E+08
Birds1 2.43E+09
Duck1 2.43E+09
Muskrat2 3.40E+07
Raccoon2 1.00E+09
Wild Turkey3 9.30E+07
1EPA 2000, 2Kator & Rhodes 1996, 3ASAE 1998

Livestock Contributions
Fecal coliform contributions from livestock occur through manure spreading processes and direct deposition during grazing. One larger livestock establishment is present in the watershed. This
farm, located on Galloway Road, currently houses approximately 100 head of beef cattle, 7200
hogs, and 6 donkeys (personal communication, Dale Clemmons). There are also several other small farms scattered throughout the watershed with a small number of cattle, horses, and poultry.
In the Shoreline Survey conducted by NCDEH Shellfish Sanitation, these smaller farms were reported to house approximately 25 horses, 25 hens, and 20 head of cattle total (NC DENR 2007b).
The hog farm in the watershed is a state-permitted facility and, as such, is not required to be
included in the wasteload allocation of the TMDL. The waste from the facility is pre-treated in two
Lockwoods Folly River Fecal Coliform TMDL
60
anaerobic waste lagoons and is subsequently treated using land application. According to the permits and the nutrient management plans for this farm, it is a no-discharge facility and the waste
is required to be applied at agronomic rates without direct runoff to streams. The facility has had no violations in its history. Given the permit requirements and nutrient management plans, this facility
is likely not a significant source of fecal coliform. The fecal coliform loads calculated for this facility,
and all sources, in this nonpoint source assessment are an estimate of the fecal coliform available for runoff in the watershed and are not a representation of direct loading to streams.
In order to calculate available loads from livestock to the watershed, literature values were collected for fecal coliform production rates of livestock, the confinement of livestock, and the percent of
manure available for runoff. Fecal coliform production rates for various types of livestock are listed
in Table C3. The amount of manure available for runoff is based on the confinement of the livestock and also on the stockpiling of the manure that is produced and distributed to agricultural land (MDE
2005). It was assumed that 100% of the direct deposit contribution was available for runoff. The estimated percentage of manure application available for wash off is about 40% (VIMS 2004). For
poultry, however, about 10% is available for wash off (MDE 2005) (Table C4). Therefore, fecal
coliform decay is considered in the estimation of fecal coliform loading. Characteristics of the operation were also taken into account. In large permitted hog farms, the waste from the hogs is
stored in lagoons for anaerobic treatment and applied to agricultural fields according to strict regulation. The availability of fecal coliform for runoff is highly variable between sites and depends
upon factors such as soils, vegetated buffer condition, slope, and setbacks. The estimated
percentage of manure application from hogs available for runoff may be less than 10% (personal communication, Otto Simmons). A conservative estimate of 10% was assumed for this source
assessment.
Table C3. Livestock fecal coliform production rates
Source
FC Production
(counts/animal/day)
Dairy 1.01E+11
Beef 1.20E+10
Horses 4.20E+08
Sheep 1.20E+10
Broilers 1.36E+08
Turkeys 9.30E+07
Chickens 1.36E+08
Layers 1.36E+08
Hogs 1.08E+10
Source: VIMS 2004
Lockwoods Folly River Fecal Coliform TMDL
61
Table C4. Livestock percent confinement and manure runoff
Livestock Percent of Time Confined Percent Manure Available for Runoff
Dairy 80% 40%
Beef 20% 40%
Horses 50% 40%
Sheep 50% 40%
Broilers 85% 10%
Turkeys 85% 10%
Chickens 85% 10%
Layers 85% 10%
Hogs1 100% 10%
1Hogs are confined 100% of the time in large permitted hog farms
Based on the number and type of livestock in the watershed, their fecal coliform production rates,
and percent of manure available for runoff, it was calculated that the daily load of fecal coliform from livestock is 9.05 x 1012 counts per day.
Pet Contribution
Pet contributions to fecal coliform loading usually occur through runoff from urban and residential areas. In order to quantify the density of domestic animals in the Lockwoods Folly watershed, the
number of household pets was calculated based on market research statistics from the American
Veterinary Medical Association (AVMA, 2007). It was assumed that dogs would be the only household pet contributing to fecal coliform loading. National statistics show that 36.1% of
households own dogs with an average of 1.6 dogs per household. The number of households in the watershed was calculated from tax parcel data, resulting in approximately 11,240 households and
6490 dogs.
No current data exists on the pet waste disposal habits of the residents of the Lockwoods Folly watershed. However, an extensive citizen survey, which included data on pet waste removal, was
conducted across the state in 2005 by the North Carolina Department of the Environment and Natural Resources. The results showed that 47% of urban pet walkers, 49% of suburban pet
walkers, and 59% of rural pet walkers ‘rarely’ or ‘never’ picked up pet waste (Holman 2007). EPA studies estimate that the fecal coliform production rate of dogs can amount to 5 x 109 counts/dog/day (EPA 2000). Based on these statistics, and the assumption that pet waste habits
would lie somewhere between the suburban and rural habits, a total fecal coliform loading rate from pets was calculated to be 1.75 x 1013 counts per day over the entire watershed using the following
equation:
Lockwoods Folly River Fecal Coliform TMDL
62
Loading = NR1PRdog
Where:
N = the number of dogs in the area
R1 = percentage of dogs contributing fecal matter (54%)
PRdog = average fecal coliform production rate for dogs
Human Contributions
Human contributions to fecal coliform loading can occur due to wastewater facility discharges, the
failure of septic systems, or through the pollution of recreational vehicles discharging directly into
waterbodies in the watershed. There is limited sewer service provided by the West Brunswick Wastewater Treatment Facility. This is a no-discharge facility which provides a high level of
pretreatment before utilizing land application as a final treatment. Effluent limits for fecal coliform are a monthly geometric mean of 14 counts/100mL. The main land application site in the watershed
is located on a forested parcel on Smith Road. Given the level of pretreatment, the slow application
rates, the vegetative cover at the site, and the well established vegetative buffers of streams on site, this is not a likely source of fecal coliform in the watershed. Instead, due to limited sewer
service in the area, the failing of septic systems is the main contributor of fecal coliform sources from humans.
The number of septic systems in the watershed was calculated using GIS techniques and available
tax parcel and sewer system spatial data. All developed parcels in the watershed without sewer were assumed to have septic systems. The analysis resulted in an estimated 11,060 septic systems
in the watershed, with 5,890 septics in the watershed area draining to the estuary (the remainder are within areas that drain to the ICWW). The calculation for estimating the daily loading of fecal
coliform from septic systems involves the number of septic systems, the average number of
persons per septic system (or household), septic failure rates, and an average pollutant loading value associated with each person.
Septic systems exhibit variable failure rates depending on the type of system, maintenance regime, and environmental factors such as soil type and groundwater level. In a study of septic systems in
Brunswick County, Uebler et al. (1983) found that systems on poorly drained Leon soils had a 13%
higher rate of failure (20.5% versus 7.5%) compared to other systems. A statewide survey conducted in 1982 and cited in NCDEH (2000) found an average 11.4% failure rate. Data collected
by Brunswick County shows 1,091 unique repairs in the watershed based on data from 1980 to mid-2006. Staff with the County Department of Health suggested that the tracking system has evolved
over time and that this number may not be representative of an exact accounting of the number of
repairs conducted. In addition, there may be some systems with failure that were never reported. Using GIS analysis, it was calculated that approximately 30% of soils within developed parcels with
septic fall into the following drainage classes: excessively drained, poorly drained, or very poorly drained. Some of the remaining soils have limited suitability for septic tanks as well. The failure rate
used for this study is based on a weighted average of data from Uebler et al. (1983) and county soils data. A final failure rate of 12% was estimated. This rate is inclusive of a variety of failure types.
Lockwoods Folly River Fecal Coliform TMDL
63
The pollutant loading per person was calculated based on an estimated wastewater production of 70 gallons/person/day (Horsely & Whitten 1996) and an average fecal coliform concentration of 2 x
105 MPN/100 ml (EPA 2002). US 2006 Census data for Brunswick County shows an average of 2.38 persons per household. Given these statistics and the estimated septic system failure rate,
fecal coliform loading due to human contributions in the watershed area draining to the estuary was
calculated to be 8.91 x 1011 counts per day using the following equation:
Load = PSFrCQCv
Where
P = number of people per septic system (or household)
S = number of septic systems
Fr = septic failure rate
C = fecal coliform concentration in wastewater
Q = wastewater production per person
Cv = conversion factor (37.854)

Lockwoods Folly River Fecal Coliform TMDL
64
Appendix D. Model Results of Median and 90th Percentile
The 30-month median and 90th percentile were calculated for the model segment M0S2 of the TPWQM in which the calibration points Site 7A and Site 8 are located. The time series plot for the
TMDL period of the existing condition and load reduction scenario for the 90th percentile and
median are presented in Figures D1 and D2. Given that each point represents a statistic of the previous 30 months, the first point appears in July of 2006.
0
20
40
60
80
100
120
6/7/2006 12/24/2006 7/12/2007 1/28/2008 8/15/2008 3/3/2009 9/19/2009
Fe
c
a
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c
o
l
i
f
o
r
m

(
c
o
u
n
t
s
/
1
0
0
m
L
)
Date
90th percentile
90th percentile standard Modeled Current 90th percentile Modeled TMDL 90th percentile
Figure D1. Modeled current and TMDL 90th percentile

Lockwoods Folly River Fecal Coliform TMDL
65
0
5
10
15
20
6/7/2006 12/24/2006 7/12/2007 1/28/2008 8/15/2008 3/3/2009 9/19/2009
Fe
c
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c
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o
r
m

(
c
o
u
n
t
s
/
1
0
0
m
L
)
Date
Median
Median standard Modeled Current Median Modeled TMDL Median
Figure D2. Modeled current and TMDL median

Appendix E
Lockwoods Folly River TMDL
Model Documentation

Prepared for the
North Carolina Division of Water Quality
August 2010

Prepared by

Stantec Consulting Services Inc.
801 Jones Franklin Road
Raleigh, North Carolina 27606
Ph: 919/ 865-6866
Fax: [phone]
www.stantec.com

Stantec Project No.: 171300183

E-i

1.0 Introduction ............................................................................................. E-1
2.0 Watershed Description ............................................................................ E-1
2.1.1 Hydrology ...................................................................................... E-1
2.1.2 Geology and Soils ......................................................................... E-3
2.1.3 Land Use and Land Cover ............................................................ E-4
3.0 Watershed Model .................................................................................... E-7
3.1 Watershed Hydrology Model ................................................................ E-7
3.1.1 Subbasin Delineation .................................................................... E-7
3.1.2 HEC-HMS Model Subroutines ....................................................... E-9
3.1.3 Final Discharge Calculation (the Routing Model) ........................ E-11
3.1.4 Precipitation Data ........................................................................ E-14
3.1.5 Hydrology Model Calibration ....................................................... E-14
3.2 Watershed Loading Model ................................................................. E-18
3.2.1 EMC Value Selection .................................................................. E-19
3.2.2 Watershed Loading Model Calibration ........................................ E-22
3.2.3 Watershed Loading Model Assumptions ..................................... E-24
3.3 Watershed Model Limitations and Sources of Uncertainty................. E-24
4.0 Tidal Prisms Water Quality Model ......................................................... E-25
4.1 Segmentation ..................................................................................... E-25
4.2 Watershed Loading Model – TPWQM Linkage .................................. E-27
4.3 TPWQM Model Calibration ................................................................ E-27
4.4 TPWQM Model Assumptions ............................................................. E-31
4.5 TPWQM Model Limitations and Sources of Uncertainty .................... E-31
4.6 TMDL Calculation .............................................................................. E-31
4.7 Critical Condition ................................................................................ E-32
4.8 Seasonality ........................................................................................ E-32
4.9 TMDL Loading Cap ............................................................................ E-33
4.10 Wasteload Allocation ...................................................................... E-34
4.11 Load Allocation ............................................................................... E-35
4.12 Margin of Safety ............................................................................. E-35
4.13 Summary of Total Maximum Daily Loads ....................................... E-35
5.0 References ............................................................................................ E-37
Appendix A. Instructions for Navigating the Watershed Loading Excel
Spreadsheets and Generating the TPWQM Input File CAL-NPS.IN ............... E-40
Appendix B. TPWQM Input Files .................................................................... E-42
Appendix C. Watershed-TPWQM Linkage VBA Scripts .................................. E-49
Appendix D. Model Results of Median and 90th Percentile ............................. E-55
E-1

1.0 Introduction
A linked watershed and tidal modeling approach was used to simulate fecal coliform
loading from the Lockwoods Folly River watershed and fecal coliform concentration in
the Lockwoods Folly estuary. Freshwater flows for the watershed were estimated
through simplified hydrologic modeling and pathogen loads were generated through the
application of event mean concentrations. The Tidal Prism Water Quality Model
(TPWQM) was used as the receiving-water quality model to predict fecal coliform
concentrations in the estuary. A description of the watershed, the modeling approach for
the watershed loading model, and the receiving-water quality model are provided in the
following sections.
The water quality goal of this TMDL is to reduce high fecal coliform concentrations in the
impaired segments to levels such that the designated use for the restricted shellfish
harvesting areas will be met. The selected watershed model calculated the watershed
load to the Lockwoods Folly estuary which includes loads from Mullet Creek, Spring
Creek, Mill Creek, Lockwoods Creek, and the Lockwoods Folly River up to Brunswick
County SR 1200. Therefore, the load reduction calculated for the estuary is applied to all
of the aforementioned segments. A TMDL was not developed for the Intracoastal
Waterway (ICWW) and Montgomery Slough because the hydrodynamics are not
conducive to using the linked watershed and Tidal Prism modeling approach. These
areas will instead be addressed in the TMDL implementation strategies.
2.0 Watershed Description
2.1.1 Hydrology
The Lockwoods Folly River study area is situated in south central Brunswick County and
covers approximately 153 square miles. Although Lockwoods Folly River is part of the
Lumber River Basin, it originates near the Town of Bolivia, flows westerly and then
southwesterly, and empties into the Atlantic Ocean through the Lockwoods Folly River
Inlet. The barrier islands of Oak Island and Holden Beach protect the river inlet. The
Atlantic Intracoastal Waterway (ICWW), constructed in the 1930’s, is located landward of
the islands connecting to a small estuary formed by the river near the Town of
Varnamtown (Figure 1). In addition to the ICWW and the inlet, the Lockwoods Folly
River from the ocean to the Highway 211 bridge (~12.5 miles) is maintained for
navigation by the US Army Corps of Engineers (Corps). Montgomery Slough partially
bisects Oak Island towards the seaward side of the island, and is connected to the
ICWW in two locations. The Lockwoods Folly estuary drains to the ICWW before
reaching the outlet to the Atlantic Ocean (Figure 1). The ICWW and Montgomery Slough
do not drain to the Lockwoods Folly estuary. Given their connection, and the open-
ended nature of the ICWW, the hydrodynamics of these two waterbodies are not
conducive to using the linked watershed and Tidal Prism modeling approach. These
areas will instead be addressed in the TMDL implementation plan strategies.
While it does not drain to the Lumber River, the Lockwoods Folly River watershed is
considered to be within the Lumber River Basin, which is composed of four separate
river systems. The Lockwoods Folly River is located within the basin’s Coastal Area
Watershed, which also includes the Shallotte River to the west. The study area, which
includes portions draining directly to the ICWW, encompasses five 14-digit hydrologic
units: 03040207020010, 03040207020020, 03040207020030, 03040207020040, and
E-2

03040207020050. Major tributaries to the Lockwoods Folly River are River Swamp,
Royal Oak Swamp, and Mill Creek. The ICWW and Mongtomery Slough do not drain to
the Lockwoods Folly estuary (Figure 1).
The watershed contains two hydrologic areas as identified by the US Geological Survey
(Giese and Mason, 1993): HA2 (sandy soils) and HA1 (clayey soils). Local relief is
commonly 1 to 2 feet per mile and the median 7Q10 (the lowest stream flow for seven
consecutive days that would be expected to occur once in ten years) approaches zero.
Average annual precipitation in Southport, Brunswick County based on 49 years of
record is 56.6 inches (Fine and Cunningham, 2001). There are no USGS stream gages
located within the watershed. Stream gages in nearby watersheds are at Hood Creek
near Leland (USGS 02105900) and Waccamaw River at Freeland (USGS 02109500),
located in the northeast and northwest Brunswick County, respectively.
E-3

Atlantic Ocean
Lockwoods Folly River
Intracoastal Waterway
Lockwoods F
olly River
Royal Oak Swamp
River Swamp
Middle Swamp
Red Run
Midway Branch
Clark Branch
Beaverdam Swamp
Nucitt Branch
Scotts Branch
Little Doe Creek
Ford Branch
Fall Swamp
Pinch Gut Creek
Mill Creek
Half Hell Branch
Boggy Branch
Bolivia Branch
Ramshead Branch
Mullet Creek
Boiling Spring Lakes
Oak Island
Shallotte
Caswell BeachHolden Beach
Southport
Bolivia
Varnamtown St. James
OCEAN HWY E
RIVE
R RD SE
GREEN SWAMP RD
OCEAN HWY W
SOUTHPORT-SUPPLY RD SE
OLD OCEAN HWY
HOLDEN BEACH RD SW
MAIN ST
GEORGE II HWY
STONE CHIMNEY RD SW
N. HOWE ST
GEOR
GE II HWY SE
LONG BEACH RD
FERRY RD
RIVER
RD SE
/
0 2 Miles
Lumber River Basin LockwoodsFolly RiverWatershed
Legend
Watershed
Streams
Waterbodies
Brunswick County
Major Roads
Municipalities
Figure 1. Location map

2.1.2 Geology and Soils
Topography of the study area is mostly characterized by gently undulating to nearly flat
plains. Natural subsurface drainage is sluggish except near streams. Elevation ranges
from 83 feet down to sea level. The mean elevation for the watershed study area is
approximately 36 feet above sea level.
The dominant geologic formation of the Lockwoods Folly River watershed is the tertiary
Waccamaw Formation, characterized by fossiliferoas sand with silt and clay. Brunswick
County is underlain by more than 1,300 ft of mostly unconsolidated sediments,
consisting of surficial deposits, and the Castle Hayne (in the southeastern part of the
County), Peedee, Black Creek, Middendorf, and Cape Fear Formations (Fine and
Cunningham, 2001).
Most of the watershed is located in the Lower Coastal Plain soil region (Daniels et al.,
1999). Upland soils adjacent to the floodplain include well drained and moderately well
drained soils (hydrologic soil group A or B) such as the loamy Baymeade (SCS 1986).
Sandy, excessively drained soils of the Kureb-Wando map units are located within the
areas of Varnamtown, Sunset Harbor, and Oak Island. In addition, there are large areas
of somewhat poorly to very poorly drained soils such as Leon and Murville, Torhunta,
E-4

and Croatan. Map units that are completely hydric soils or contain hydric soils make up
about 89% of the watershed. Over 92% of the soils in the watershed are rated as very
limited in terms of septic suitability.
2.1.3 Land Use and Land Cover
An existing land use/land cover map was created for modeling purposes using the 2004
Brunswick County existing land use map and aerial photography. The resulting map is
comprised of 16 different land use classes including Office/Institutional,
Commercial/Heavy Industrial, Golf Course, Roads, Pasture, Row Crop, Water, Wetland,
Bare Earth, Forest, Open Space, and four residential land uses of various densities.
North Carolina Department of Transportation (NCDOT) roads were separated from non-
NCDOT roads in order to track their individual contribution of fecal coliform loads to the
watershed. The density of residential land use was assigned based on lot size (Table 1).
Table 1. Residential land use categories
Lot Size (acres) Residential Category Residential Category Code
0.07 – 0.2249 Residential high density RHD
0.2250 – 0.3349 Residential medium density RMD
0.3350 – 0.9950 Residential low density RLD
0.995 – 5.0 Residential very low density RVL
All residential parcels over five acres were reviewed using 2004 aerial imagery (obtained
from Brunswick County) and were then assigned a land use of Forest, Row Crop,
Pasture, Bare Earth or Open Space based on land cover. The land cover is the
dominant land use in these situations as a house on these large parcels does not
contribute a significant amount of impervious surface. All other categories were assigned
based on the 2004 Brunswick County existing land use map.
The resulting land use distribution in the Lockwoods Folly River watershed is included in
Table 2 and depicted in Figure 2. At approximately 73%, the watershed is primarily
comprised of forest land. Of the forested land, approximately 30% is wooded wetland
and 20% is managed pineland. Residential, commercial, industrial, and office land uses
combined currently make up about 6% of the watershed. Other major land uses include
Open Space at 7.6% and Row Crop at 4.8%.
E-5

Table 2. Land use distribution in the Lockwoods Folly River watershed
Land Use Category
Area
(acres) Percent
High Density Residential (0.07 - 0.22 acres) 807 0.8%
Medium Density Residential (0.23 - 0.33 acres) 617 0.6%
Low Density Residential (0.34 - 0.99 acres) 1519 1.5%
Very Low Density Residential (1 - 5 acres) 1888 1.9%
Commercial/Heavy Industrial 215 0.2%
Office/Institutional/Light Industrial 596 0.6%
Road (w/ ROW) non-NCDOT 1527 1.6%
Road (w/ ROW) NCDOT 1629 1.7%
Bare Earth 220 0.2%
Open Space 7456 7.6%
Golf Course 631 0.6%
Pasture 858 0.9%
Row Crop 4660 4.8%
Forest (includes wooded wetland and managed
pineland) 71407 72.9%
Emergent wetland 1860 1.9%
Water 2119 2.2%

E-6

Figure 2. Current land use
St. James
Oak Island
Boiling Spring Lakes
Shallotte
Holden Beach
Bolivia
Varnamtown
Caswell Beach
OCEAN HWY E
OCEAN HWY W
SOUTHPORT-SUPPLY RD SE
GREEN SWAMP RD
OLD OCEAN HWY
MAIN ST
HOLDEN BEACH RD SW
GEORGE II HWY SE
WHITEVILLE RD
BEACH DR SW
GEORGE II HWY
OCEAN ISLE BEACH RD SW
BRICKLANDING RD SW
LONG
BEACH RD
Royal Oak Swamp
River Swamp
Middle Swamp
Red Run
Midway Branch
Nucitt Branch
Scotts Branch
Little Doe Creek
Ford Branch
Fall Swamp
Pinch Gu
t Creek
Mill Creek
Half Hell Branch
Sarah Hole
Spring Creek
Ramshead Branch
Atlantic Ocean
Lockwoods Folly River
Intracoastal Waterway
Legend
Streams
Municipalities
Model Subwatersheds
Land Use Categories
Bare Earth
Forest
Open Space
Row Crops
Pasture
Golf Course
Commercial/Heavy Industrial
Office/Institutional/Light Industrial
Residential High Density
Residential Medium Density
Residential Low Density
Residential Very Low Density
Roadway
Water
Wetland ³
2 01 Miles
E-7

3.0 Watershed Model
A simplified watershed model was developed utilizing HEC-HMS (v. 3.3) to estimate flow
for the Lockwoods Folly River watershed given land use, soils, and precipitation data.
The fecal coliform loading model was developed using literature values for event mean
concentrations (EMC) in conjunction with the runoff calculated from the various soil-land
use combinations in the watershed. The fecal coliform loading model was generated
using a series of Excel spreadsheets. Instructions for using and navigating these
spreadsheets are included in Appendix A.
3.1 Watershed Hydrology Model
HEC-HMS is a GUI based program designed to simulate the precipitation-runoff
processes of dendritic watershed systems. It is able to incorporate storm flow, base flow,
and evapotranspiration in a continuous simulation of hydrologic processes. Data
collection requirements for HEC-HMS are less intensive than more complex models like
HSPF.
3.1.1 Subbasin Delineation
The Lockwoods Folly River watershed was delineated into 27 subbasins contributing
flow to the Lockwoods Folly estuary (Figure 3). It should be noted that contribution of
flow and fecal coliform loading from a 28th subbasin was not included in this model. The
28th basin drains to the Intracoastal Waterway and Montgomery Slough, and not to the
Lockwoods Folly estuary. Subbasin delineation was performed using ArcGIS tools and
was based on elevation data. The delineation was further refined based on roadways,
field reconnaissance, and the location of monitoring stations.
Weighted curve numbers (CN) for each subbasin were developed using guidance
published by the Soil Conservation Service (SCS 1975) based on the relative areas of
land use and soil combinations in each subbasin. The curve numbers were used to
assign values for various input parameters in the watershed hydrology model as
described in Section 3.1.2.

E-8

Figure 3. Watershed model subbasins and flow and water quality monitoring stations
Southport-Supply Rd
17
Gilbert Rd
Stone Chimney Rd
Sunset Harbor Rd
Green Swamp Rd
Old Ocean Hwy
UT01
MC01
LFR01
ICW03
ROS01
LFR19
LFR11
LFR06
LFR03
LFR02
River Swamp
Middle Swamp
Royal Oak Swamp
Red Run
Midway Branch
Clark Branch
Nucitt Branch
Little Doe Creek
Ford Branch
Fall Swamp
Pinch Gut Creek
Half Hell Branch
Spring Creek
Bolivia Branch
Ramshead

Branch
Mullet Creek
Atlantic Ocean
Lockwoods Folly River
Intracoastal Waterway
Legend
SSS sites
NCCF estuary sites
NCCF tributary sites
Flow monitoring sites
Model subbasins
Lockwoods Folly watershed
Major roads
Minor roads
Streams 0 2 41 Miles
E-9

3.1.2 HEC-HMS Model Subroutines
HEC-HMS uses a series of subroutines to model flow in a dendritic system. These
subroutines include the Loss Model, Transform Model, and Baseflow Model. Values
derived for the input parameters of these subroutines are summarized in Table 3 and
Table 4. Results from these subroutines were used in final discharge calculations to the
estuary as described in Section 3.1.3. The model was developed using an hourly time
step. A more detailed description of the HEC-HMS model is provided in the user’s
manual (USACE 2008).
Loss Model
The Deficit and Constant Loss Model was selected to model runoff quantity from the 27
delineated subbasins. This model was selected because it allows for the drying of soil
via evapotranspiration, and is therefore more suitable for running a long-term,
continuous simulation of runoff. Inputs for this subroutine include initial deficit (in),
maximum storage (in), constant rate (in/hr), and percent imperviousness. Percent
imperviousness for each subbasin was derived from land use data and literature values
for imperviousness using GIS techniques. Initial deficit, maximum storage, and constant
rate were derived based on curve number for each subbasin as follows. Weighted curve
numbers were assigned to each subbasin as described in Section 3.1.1, providing a
range of curve numbers across the entire watershed. A range of values was then
established for each input variable (i.e. maximum storage or constant rate). A value of
each input variable was assigned to each subbasin based on the relative position of their
curve number along the watershed-wide curve number range (e.g. if a subbasin’s curve
number was in the 10th percentile of the curve number range, a value for the input
variable was assigned such that it was the 10th percentile value of the variable’s range).
The range of each input variable was adjusted for the calibration of the flow model
described in Section 3.1.5.
Assumptions for the Loss Model include the following:
• Depth to groundwater is sufficient such that it does not influence infiltration rates.
• Input variable values remain constant for storm events of different magnitudes.
The governing equations of the Loss Model relate to the underlying concept that the
maximum potential rate of precipitation loss, fc, is constant throughout an event. Thus, if
pt is the average precipitation depth during a time interval to t+dt, the excess, pet, during
the interval is given by:
⎭⎬⎫
⎩⎨⎧≥−≡otherwise
fpiffppectct
t 0
An initial loss, Ia, is added to the model to represent interception and depression storage.
Interception storage is a consequence of absorption by surface cover. Depression
storage is a result of depressions in the watershed; water in these depressions is stored
and eventually infiltrates or evaporates. This loss occurs prior to the onset of runoff.
Until the accumulated precipitation amount on the pervious area exceeds the initial loss
volume, no runoff occurs. Thus the excess is given by:
E-10

⎪⎭
⎪⎬
⎫
⎪⎩
⎪⎨
⎧
≤≥
≥≥−
≤
≡
∑∑∑
cti
ctict
i
t
fpandIapif
fpandIapiffp
Iapif
pe
0
0

Transform Model
The transform model generates the discharge at a given point in the watershed based
on the runoff calculated in the Loss Model. The Clark Unit Hydrograph was selected for
this subroutine. Input parameters for this model include time of concentration (hours)
and a storage coefficient (hours). Time of concentration within each subbasin was
calculated using topographic data and stream length data. The storage coefficient
represents the time over which the discharge is distributed for a given point in the
watershed. The initial storage coefficient value was assigned based on research which
demonstrated that a constant ratio relationship between storage coefficient and time of
concentration exists at regional levels (USGS 2000). This ratio was altered during the
calibration process as described in Section 3.1.5. A single ratio (R) of storage coefficient
to time of concentration value was used for the entire watershed. Governing equations
include the following, where R is the ratio, S is the storage coefficient, and Tc is the time
of concentration:
ST
SR
c +≡
Assumptions for the Transform model include the following:
• The ratio between storage coefficient and time of concentration is constant across a
region.
• The Lockwoods Folly River watershed is a single region.
For the governing equations, the Clark method requires three parameters to calculate a
unit hydrograph: Tc, the time of concentration for the basin, R, a storage coefficient, and
a time-area curve. A time-area curve defines the cumulative area of the watershed
contributing runoff to the subbasin outlet as a function of time (expressed as a proportion
of Tc).
The dimensionless time area curve is derived by:
AI = 1.414 T ^1.5 for 0 <= T < 0.5
1 – AI = 1.414 (1 – T) ^1.5 for 0.5 < T <1
where:
AI = cumulative area as a fraction of total subbasin area and
T = fraction of time of concentration.
The ordinates of the time-area curve are converted to volume of runoff per second for
unit excess and interpolated to the given time interval. The resulting translation
hydrograph is then routed through a linear reservoir to simulate the storage effects of the
E-11

basin; and the resulting unit hydrograph for instantaneous excess is averaged to
produce the hydrograph for unit excess occurring in the given time interval.
The linear reservoir routing is accomplished using the general equation:
Q(2) = CA × I × CB × Q(1)
The routing coefficients are calculated from:
CA = Delta T / (R + 0.5 × Delta T)
CB = 1 - CA
Qungr = 0.5 [Q(1) + Q(2)]

where:
Q(2) = instantaneous flow at end of period,
Q(1) = instantaneous flow at the beginning of period,
I = ordinate of the translation hydrograph,
Delta T = computation time interval in hours (also duration of unit excess),
R = basin storage factor in hours, and
Qungr = the unit hydrograph ordinate at end of computation interval.
The computation of unit hydrograph ordinates is terminated when its volume exceeds
0.995 inch (mm) or 150 ordinates, whichever occurs first.
Baseflow
There are several possible methods for modeling baseflow within HEC-HMS. For this
watershed model, a constant monthly baseflow was estimated based on observed data
from discharge gages installed in the watershed (Section 3.1.5) versus relative drainage
areas. Monthly baseflow values for each subbasin are presented in Table 4.
Assumptions for the Baseflow Model include the following:
• Baseflow remains constant throughout a given month.
• Baseflow is related to drainage area for any given point in the watershed.
• Baseflow is relatively constant from year to year.
3.1.3 Final Discharge Calculation (the Routing Model)
To calculate the discharge from the entire watershed entering into the estuary, flow from
each subbasin was extracted from the HEC-HMS model and brought into Excel. Routing
from each subbasin to the estuary was then derived based on flood wave velocity and
lag time. Average flood wave velocities for each subbasin were estimated using field
reconnaissance and data from the discharge gage. Flood wave velocities were
subsequently used to calculate lag time for each subbasin. The final discharge to the
estuary was then calculated as a function of each subbasin’s lag time and modeled
discharge at any given time step.
E-12

Assumptions for the Final Discharge Calculation (Routing Model) include the following:
• Lag time remains constant for a given subbasin across various discharge
magnitudes.
• Flood wave velocity is not influenced by tidal effects.
Governing equations include the following:
Velocity
thStreamLengLagtime≡
Table 3. Watershed hydrology input parameters by subbasin
Loss Model Transform Model Lag Time
Subbasin
to
Estuary
(hr)
Subbasin Initial
Deficit
(in)
Maximum
Storage
(in)
Constant
Rate
(in/hr)
Impervious
%
Time of
Concentration
(hr)
Storage
Coefficient
(hr)
Subbasin-1 0.248 0.4950 0.671 2.7 12.22 51.9 47
Subbasin-2 0.31 0.6200 0.813 2.9 9.56 40.6 47
Subbasin-3 0.353 0.7060 0.896 3.5 6.65 28.3 59
Subbasin-4 0.349 0.6980 0.889 3.3 5.86 24.9 53
Subbasin-5 0.404 0.8090 0.985 4.4 8.24 35.0 39
Subbasin-6 0.289 0.5780 0.768 3.6 13.31 56.5 40
Subbasin-7 0.286 0.5730 0.762 6.6 12.29 52.2 40
Subbasin-8 0.274 0.5480 0.734 7.6 5.77 24.5 30
Subbasin-9 0.248 0.4960 0.672 8.0 6.98 29.7 23
Subbasin-10 0.333 0.6660 0.859 7.0 7.43 31.6 12
Subbasin-11 0.363 0.7260 0.915 4.8 2.03 8.6 20
Subbasin-12 0.337 0.6730 0.866 9.8 5.13 21.8 15
Subbasin-13 0.479 0.9580 1.095 7.1 3.31 14.0 4
Subbasin-14 0.315 0.6300 0.823 11.2 8.99 38.2 4
Subbasin-15 0.386 0.7710 0.954 3.3 10.67 45.3 5
Subbasin-16 0.319 0.6380 0.831 4.1 5.54 23.5 38
Subbasin-17 0.25 0.5010 0.678 3.1 7.34 31.2 41
Subbasin-18 0.327 0.6530 0.846 3.3 10.26 43.6 61
Subbasin-19 0.39 0.7790 0.961 3.5 9.39 39.9 61
Subbasin-20 0.256 0.5130 0.693 4.5 10.33 43.9 51
Subbasin-21 0.216 0.4320 0.589 5.3 14.06 59.7 51
Subbasin-22 0.26 0.5200 0.701 5.9 11.23 47.7 44
Subbasin-23 0.213 0.4250 0.579 2.5 15.71 66.7 61
Subbasin-24 0.217 0.4340 0.591 2.0 9.32 39.6 61
Subbasin-25 0.236 0.4710 0.641 2.2 7.15 30.3 61
Subbasin-26 0.249 0.4970 0.674 6.3 11.22 47.6 55
Subbasin-27 0.309 0.6190 0.811 9.3 2.55 10.8 0

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Table 4. Estimated constant monthly baseflows (cfs) by subbasin
January February March April May June July August September October November December
Subbasin-1 3.6588 3.6588 3.8051 3.4392 3.0734 2.3416 1.9757 1.6099 1.3172 1.244 2.1953 2.927
Subbasin-2 2.5364 2.5364 2.6379 2.3842 2.1306 1.6233 1.3697 1.116 0.91311 0.86238 1.5219 2.0291
Subbasin-3 2.2499 2.2499 2.3399 2.1149 1.8899 1.4399 1.215 0.98996 0.80997 0.76497 1.35 1.7999
Subbasin-4 1.3528 1.3528 1.4069 1.2716 1.1363 0.86579 0.73051 0.59523 0.48701 0.45995 0.81168 1.0822
Subbasin-5 2.0137 2.0137 2.0943 1.8929 1.6915 1.2888 1.0874 0.88603 0.72494 0.68466 1.2082 1.611
Subbasin-6 2.7078 2.7078 2.8161 2.5453 2.2745 1.733 1.4622 1.1914 0.97481 0.92065 1.6247 2.1662
Subbasin-7 2.0671 2.0671 2.1498 1.9431 1.7364 1.323 1.1162 0.90954 0.74417 0.70282 1.2403 1.6537
Subbasin-8 2.9533 2.9533 3.0714 2.7761 2.4808 1.8901 1.5948 1.2995 1.0632 1.0041 1.772 2.3626
Subbasin-9 2.424 2.424 2.521 2.2786 2.0362 1.5514 1.309 1.0666 0.87265 0.82417 1.4544 1.9392
Subbasin-10 2.1557 2.1557 2.2419 2.0263 1.8108 1.3796 1.1641 0.9485 0.77605 0.73293 1.2934 1.7245
Subbasin-11 1.1646 1.1646 1.2112 1.0947 0.97827 0.74535 0.62889 0.51243 0.41926 0.39596 0.69876 0.93168
Subbasin-12 0.99158 0.99158 1.0312 0.93209 0.83293 0.63461 0.53546 0.4363 0.35697 0.33714 0.59495 0.79327
Subbasin-13 0.64082 0.64082 0.66645 0.60237 0.53829 0.41012 0.34604 0.28196 0.23069 0.21788 0.38449 0.51265
Subbasin-14 3.1402 3.1402 3.2658 2.9518 2.6378 2.0097 1.6957 1.3817 1.1305 1.0677 1.8841 2.5122
Subbasin-15 5.1004 5.1004 5.3044 4.7944 4.2844 3.2643 2.7542 2.2442 1.8362 1.7341 3.0603 4.0803
Subbasin-16 2.2205 2.2205 2.3093 2.0872 1.8652 1.4211 1.1991 0.97701 0.79937 0.75496 1.3323 1.7764
Subbasin-17 2.107 2.107 2.1913 1.9806 1.7699 1.3485 1.1378 0.9271 0.75853 0.71639 1.2642 1.6856
Subbasin-18 4.2214 4.2214 4.3902 3.9681 3.546 2.7017 2.2795 1.8574 1.5197 1.4353 2.5328 3.3771
Subbasin-19 2.5036 2.5036 2.6038 2.3534 2.103 1.6023 1.352 1.1016 0.9013 0.85123 1.5022 2.0029
Subbasin-20 2.9189 2.9189 3.0357 2.7438 2.4519 1.8681 1.5762 1.2843 1.0508 0.99244 1.7514 2.3352
Subbasin-21 5.0782 5.0782 5.2813 4.7735 4.2657 3.25 2.7422 2.2344 1.8281 1.7266 3.0469 4.0626
Subbasin-22 3.9708 3.9708 4.1297 3.7326 3.3355 2.5413 2.1443 1.7472 1.4295 1.3501 2.3825 3.1767
Subbasin-23 1.556 1.556 1.6183 1.4627 1.3071 0.99587 0.84026 0.68466 0.56018 0.52906 0.93363 1.2448
Subbasin-24 1.8168 1.8168 1.8894 1.7078 1.5261 1.1627 0.98105 0.79938 0.65403 0.6177 1.0901 1.4534
Subbasin-25 1.3483 1.3483 1.4022 1.2674 1.1325 0.86288 0.72806 0.59323 0.48537 0.45841 0.80895 1.0786
Subbasin-26 3.2708 3.2708 3.4016 3.0745 2.7475 2.0933 1.7662 1.4391 1.1775 1.1121 1.9625 2.6166
Subbasin-27 2.6124 2.6124 2.7169 2.4556 2.1944 1.6719 1.4107 1.1495 0.94046 0.88821 1.5674 2.0899

E-14

3.1.4 Precipitation Data
One of the major inputs for the hydrology model is precipitation. The nature of rainfall in
the Lockwoods Folly Watershed is highly non-uniform. As such, rainfall data from three
separate precipitation gages was collected in order to model the variability in flow across
the watershed.
The first precipitation gage is the Nature Conservancy RAWS station (NNAC), located
within the northern portion of the watershed, along Green Swamp Road. Comprehensive
precipitation records for other rain gages within the watershed were not available. As
such, the other two stations from which precipitation data was gathered are located
outside of the watershed. The Sunny Point RAWS station (NSUN) is located in Kure
Beach, NC while the Grand Strand Airport Station (KCRE) is located in North Myrtle
Beach, SC. Precipitation data from January 1, 2004 until September 30, 2009 was
retrieved from the State Climate Office of North Carolina for the three gages (NC
CRONOS 2009). It should be noted that although two of the precipitation gages are not
located directly within the watershed, their data demonstrated that occurrence of rainfall
events at these stations matched well with events detected at the NNAC station, i.e.
large storms of long duration were found to occur concurrently at all three gages.
Average monthly precipitation during the modeling period for the three gages is
presented in Figure 4.
 Average monthly precipitation
0
1
2
3
4
5
6
7
8
9
Ja
n
u
a
r
y
Fe
b
r
u
a
r
y
Ma
r
c
h
Ap
r
i
l
Ma
y
Ju
n
e
Ju
l
y
Au
g
u
s
t
Se
p
t
e
m
b
e
r
Oc
t
o
b
e
r
No
v
e
m
b
e
r
De
c
e
m
b
e
r
Month
Pr
e
c
i
p
i
t
a
t
i
o
n

(
i
n
c
h
e
s
)
NNAC
NSUN
KCRE

Figure 4. Average monthly precipitation (2004-2009) for the three precipitation gages

3.1.5 Hydrology Model Calibration
Stream height gages were installed in the watershed specifically for this TMDL project in
order to calibrate the hydrology model. The most complete record was collected at the
gage installed off of Old Ocean Hwy at monitoring station LFR01 (see Figure 3) from
August 2008 to July 2009. Stream height was translated into a discharge record based
on the rating curve calculated for the site from data collected on cross-sectional area
E-15

and flow. The rating curve for the gage is presented in Figure 5. The resulting discharge
record was used to calibrate and validate the hydrology model.
The hydrology model was calibrated by adjusting the range of values used for the
variables within the Deficit and Constant Rate Model. As described in Section 3.1.2, a
value of each input variable was assigned to each subbasin based on the relative
position of their curve number along the watershed curve number range (e.g. if a
subbasin’s curve number was in the 10th percentile of the curve number range across
the watershed, a value for the input variable was assigned such that it was the 10th
percentile value of the variable’s range). The range of values for each input variable was
adjusted during the calibration procedure to calibrate stormflow volumes. Additionally,
the storage coefficient was adjusted during the calibration procedure. Essentially the
‘regional’ relationship/ratio between storage coefficient and time of concentration (see
the Transform Model in Section 3.1.2) was derived by altering the storage coefficient
until the shape of the unit hydrograph for modeled data reasonably approximated the
observed unit hydrograph at the watershed stream gage.
Calibration criteria for the hydrology model involved reasonable matching between the
modeled discharge and observed discharge at the stream height gage. ‘Reasonable’
matching was considered to consist of accurately approximating peak discharges as well
as the total volume of water passing through the measurement point across the
calibration period. Calibration was conducted from October 10, 2008 to February 10,
2009. The calibrated model was then validated against observed discharge data from
February 11 to July 1, 2009. Figures 6 & 7 plot modeled and observed discharge at
LFR01 where the stream gage was located, for the calibration and validation periods.
The model was also calibrated such that the quantity of runoff between observed and
modeled results were similar. This comparison was made at the seasonal level and for
the calibration period as a whole (Table 5). Additionally, simulated total discharge,
adjusted using the drainage area ratio method, was compared to discharge from a
USGS gage at a nearby watershed to demonstrate that model results were within the
same range of values. This comparison was made over both the calibration and
validation period (Table 6). The USGS gage is located on Hood Creek near Leland,
North Carolina, with a drainage area of 21.6 sq mi (USGS 02105900). The drainage
area upstream of the stream gage on the Lockwoods Folly River is 16.0 sq mi.
Table 5. Comparison of observed and modeled runoff

Modeled
Runoff
(inches)
Observed
Runoff
(inches)
Percent
Difference
Fall 2008 1.53 1.20 27%
Winter 2008-2009 1.90 2.09 -9%
Spring 2009 2.83 2.50 13%
Total 6.26 5.80 8%

E-16

Table 6. Comparison of total seasonal discharge relative to drainage area

USGS Gage
Hood Creek
(inches)
Model Calibration
Site (Old Ocean Hwy)
(inches)
Discharge to Lockwoods
Folly Estuary
(inches)
Fall 2008 2.50 1.69 1.69
Winter 2008-2009 1.95 1.78 1.86
Spring 2009 1.74 2.59 2.24
Total 6.19 6.06 5.79
*Values in table are total seasonal discharge (cubic feet) divided by drainage area
(square feet) and converted from feet to inches.

Percent difference criteria varies between the seasonal and annual scale. The criteria
according to Lumb et. al (1994) are presented in Table 7. These criteria have been met
by the calibrated hydrology model. There is high variability in rainfall in the watershed
which leads to greater differences between observed and modeled runoff than might be
observed in watershed with more uniform rainfall distribution patterns. Additionally, the
differences between modeled and observed runoff were enhanced by two instances of
extreme peak flows, which are described below.

Table 7. Percent difference criteria for modeled and observed discharge
Prediction Error Percent Difference Criteria
Error in total volume ±10%
Error in volume of 50% lowest flows ±10%
Error in volume of 10% highest flows ±15%
Seasonal volume error ±30%

Rating Curve LFR01
y = 9.006x2 - 19.424x + 12.916
R2 = 0.9874
0
5
10
15
20
25
30
35
0 1 2 3 4
Staff gage height (ft)
Di
s
c
h
a
r
g
e

(
c
f
s
)

Figure 5. Rating curve for stream discharge at LFR01
E-17

0
10
20
30
40
50
60
70
80
90
100
10/11/2008 10/31/2008 11/20/2008 12/10/2008 12/30/2008 1/19/2009 2/8/2009
Fl
o
w
 (c
f
s
)
Date
Hydrology Calibration (10/2008 ‐2/2009)
Modeled
Observed

Figure 6. Watershed hydrology model calibration (October 2008 to February 2009)

0
20
40
60
80
100
120
140
160
180
2/11/2009 3/3/2009 3/23/2009 4/12/2009 5/2/2009 5/22/2009 6/11/2009 7/1/2009
Fl
o
w
 (c
f
s
)
Date
Hydrology Validation(2/2009 ‐7/2009)
Modeled
Observed

Figure 7. Watershed hydrology model validation (February 2009 to July 2009).

E-18

During the model calibration/validation periods, the model showed significant differences
from the observed data during two events. The first event occurred during the calibration
period on November 13, 2008. The closest precipitation gage (NNAC) to the stream
gage was used for the precipitation input to subbasins upstream of the stream gage. The
NNAC precipitation gage is located approximately 6 miles west of the stream gage. The
NNAC gage showed a total rainfall of 1.08 inches on November 13 with 1.05 inches
occurring in one hour. The model over predicted flow during this event by approximately
250%. Analysis of this event and the remainder of the record indicate that the model
may over predict discharge for high rainfall intensities. However, the model did
accurately approximate peak flow values and discharge volume for a storm occurring on
May 17, 2009. This storm consisted of 2.28 inches of rainfall with a peak intensity of 0.83
inches in one hour. In general, the model more accurately predicts flows for storms with
intensities less than 1 inch per hour. Storm events with intensities greater than 1 inch per
hour happen rarely in this area. Reviewing the rainfall record for the watershed, such
events occur approximately five times a year.
The second event in which a significant difference between the model and observed
data occurred took place during the validation period on June 14, 2009. The NNAC
precipitation gage recorded a total rainfall of 1.51 inches, with 1.46 inches occurring in
the first hour of rainfall. With only a slight increase in discharge recorded at the stream
gage, this storm event was likely a summer thunderstorm and high intensity rainfall did
not occur in the watershed upstream of the stream gage.
3.2 Watershed Loading Model
In order to calculate fecal coliform loads from the watershed to the estuary, the Rational
Method was used to compute the fraction of stormflow coming from each land use type
within each subbasin. The governing equation for the Rational Method is:
∑≡
LUiLUi
LULUtot
LU AC
ACQQ
Where, QLU is discharge (cfs) from each land use within the subbasin, Qtot is the total
discharge from the subbasin, CLU is the rational method runoff coefficient for each land
use type, ALU is the area of each land use type. A constant monthly baseflow for each
subbasin was assumed, as described in Section 3.1.2. The baseflow associated with
each land use within each subbasin was calculated based on the following:
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛
⎟⎟
⎠
⎞⎜⎜
⎝
⎛
≡
avg
tot
LU
LU
tot
b
C
A
C
AQ
Q
Where, Qb is the baseflow discharge, Qtot is the total discharge from the subbasin, ALU
and CLU are the same as above, Atot is the total subbasin area, and Cavg is the average
rational method runoff coefficient for the subbasin.
After flow rates from each land use type were determined in Excel, fecal coliform loads
were calculated using EMC (event mean concentration) values for each land use
category from pertinent research. These loads were further modified to account for the
E-19

“first flush” effect by applying a multiplying factor early in storms and a dividing factor as
flows decrease. As discharge values were modeled to increase by a certain percentage
from the previous time step, the multiplying factor was applied. Otherwise, a dividing
factor was applied to the fecal coliform concentration. The percent increase, multiplying,
and dividing factors were adjusted during the Tidal Prism Water Quality Model (TPWQM)
calibration (Section 4.3). The flows and fecal coliform loads from each land use type in
the subbasin were summed and routed to the estuary on the basis of the lag time
(routing) method (Section 3.1.3).
A decay rate of fecal coliform was also incorporated into the watershed loading model.
Fecal coliform decay rate is a highly variable parameter affected by salinity, temperature,
turbidity, and light exposure. Decay rates in freshwater are noted to be significantly lower
in freshwater than saltwater (Eleria 2005). In freshwater, the effective die-off of fecal
coliform has been shown to vary from 40 to 70% per day (Elshorbagy & Ormsbee 2005,
Yagow et al. 2001). A system with a higher decay rate has a higher assimilative capacity
than a system with a lower decay rate. A decay rate of 30% per day was selected for the
watershed model as a conservative estimate. The lag times for the subbasins in the
watershed vary from 0.17 to 2.5 days.
3.2.1 EMC Value Selection
EMCs represent the average concentration of a pollutant in stormwater runoff and are
usually reported in mass per unit volume (mg/l). Many factors may affect EMC values
including land use, annual rainfall, percent imperviousness, season, watershed size, and
storm event size. Regional differences in EMCs are largely determined by the amount
and frequency of rainfall. Pitt et al. (2005) reporting on findings from the National
Stormwater Quality Database (NSQD) found that residential areas located in the wettest
parts of the country such as the Southeast appear to have lower EMCs for many
stormwater pollutants. The result most likely stems from the reduced time between
rainfall events allowing for less accumulation of pollutants on impervious surfaces which
then become available for washoff during the next storm event. Regression analyses by
Driver (1988) and Maestre and Pitt (2005) have supported similar conclusions. Driver
(1988) found that annual rainfall depth was the best overall predictor of stormwater
EMCs.
The relative impact of land use and imperviousness is less clear. The National Urban
Runoff Program (NURP) findings showed no significant differences in urban runoff
concentrations as a function of common urban land uses (USEPA, 1983). Maestre and
Pitt (2005) conducted a statistical analysis of data from the NSQD focusing on EPA Rain
Zone 2, which includes North Carolina, Virginia, Maryland, Tennessee, Kentucky, and
West Virginia. No significant regression relationship (negative) was found for fecal
coliform with percent imperviousness in residential land use categories. A lack of data in
the study prevented a full analysis for commercial and industrial land uses.
Several studies have suggested a positive linear relationship between fecal coliform
concentrations and impervious cover (Young and Thackston, 1999; Mallin et al., 2000,
Tufford and Marshall, 2002). Schueler suggested an indirect relationship between
bacteria and imperviousness (CWP 2003). Pitt found that median concentrations of fecal
coliform were higher in residential and open space categories compared to commercial
and industrial land uses (Pitt et al., 2005). The study also found that the first flush
phenomenon is more prevalent in high impervious land uses of commercial
development.
E-20

The stormflow EMC values selected for the watershed loading model are derived based
on a number of literature sources (Table 8). Final fecal coliform EMC values for the
model were based on Zone 2 data in Pitt et al. (2005) and EPA (2001).

E-21

Table 8. Literature review of fecal coliform EMC values (cfu/100ml)
Source Location Low Density
Residential
Medium
Density
Residential
High
Density
Residential
Office and
Light
Industrial
Commercial
and Heavy
Industrial
Road Forest Golf and
Managed
Open
Space
Pasture Row
Crop
Pitt et al. (2005) US 8345 8345 8345 2500 4300
USEPA - NURP
(1983)
US 101 101 101 21000
Pitt et al. (2005) EPA
Rain
Zone 2
1600 1600 1600 1377 2400
Pitt et al. (2005) EPA
Rain
Zone 3
2800 2800 2800 210 2000
Tetra Tech (2004)1 NC 1540 1540 252 100 12500 414
Young and
Thackston (1999)2, 3
TN 12182
USEPA (2001)1 GA 8700 8700 8700 1400 1850 1400 500 500
Newell et al. (1992)1 TX 22000 22000 22000 22000 22000 1600 2500 2500 2500
Baird et al. (1996) TX 20000 20000 20000 9700 6900 53000
Bales et al. (1999) NC 29000 27500 14600
Selected Value 5150 5150 5150 1389 2125 1400 500 500 1000 500
All values are medians unless otherwise noted. 1 Literature review 2 Mean value 3 Average of winter and summer storms
E-22

3.2.2 Watershed Loading Model Calibration
Fecal coliform loads to the estuary were calibrated against observed data collected by
the North Carolina Shellfish Sanitation Program (DEHSS). The calibration was
performed by applying a multiplier and divisors to the EMC values outlined in Table 8.
Bacteria is a highly variable stormwater pollutant, with concentrations varying by factors
of 10 to 100 during a single storm event (Zariello et al. 2002; CWP 1999). In order to
account for the varying concentration of fecal coliform over individual storm events in the
watershed loading model, the series of factors were applied to the EMC values for fecal
coliform. A multiplier was applied at the beginning of storm to account for the ‘first flush’
effect, followed by two subsequent divisors applied toward the end of the storm to
account for decreasing concentrations at the end of storm events. The multiplier and
divisors were adjusted during the calibration of the receiving-water TPWQM in order to
adjust loads to the estuary such that modeled fecal coliform concentrations were
representative of observed fecal coliform concentrations in the estuary. A final multiplier
of 82 and final divisors of 100 and 20000 were selected during the calibration. The
factors were applied in the following manner:

If Qt > 1.07 *Qt-1 FCcount *82
If Qt < [AVG(Qt-1 Æ Qt-12)]*1.04 FCcount /20000
If Qt > [AVG(Qt-1 Æ Qt-12)]*1.04 AND Qt < 1.07 *Qt-1 FCcount /100

A schematic of a unit hydrograph and the relative time-frame over which these factors
were applied is depicted in Figure 8.
E-23

Figure 8. Schematic of a unit hydrograph and the relative time period of multiplier and
divisor application to EMC values in the watershed loading model.

The intent was to show increased loading at the beginning of a storm using the
multiplier, then transition to the divisor of 100 after the first flush, and towards the end of
the storm transition to the second divisor of 20000, which would further decrease loads.
Multiple calibration runs were performed varying these timestep, multiplying, and dividing
factors. It should be noted that the application of the divisor in Line B (20000) was
applied at the tail end of storms and during baseflow to simulate an effective
concentration of nearly 0 for fecal coliform during these conditions. The relative time
over which each of the multiplier or divisors were applied was dependent upon the
intensity of rainfall during the preceding 12 hours.
To verify that the loads generated by the application of these factors was reasonable,
the existing daily load to the Lockwoods Folly estuary was compared to fecal coliform
loads calculated for other coastal watersheds in North Carolina, relative to area. The
existing load for the Lockwoods Folly estuary was calculated to be 6.91E+12 counts per
day. Relative to area, the load is 5.04E+10 counts per day per square mile. Loads into
Jarret Bay, NC were calculated to be 7.82E+10 counts per day per square mile
(NCDENR 2007) and loads in the White Oak embayment were calculated to be 4.2E+11
counts per day per square mile (NCDENR 2009). It should be noted that the White Oak
embayment watershed is more developed than the Lockwoods, accounting for a greater
loading per square mile.
E-24

3.2.3 Watershed Loading Model Assumptions
Several assumptions were made for the watershed fecal coliform loading model and
include the following:
• The septic contribution to the watershed is captured in the baseflow and stormflow
EMC values.
• Assumed a decay rate of 30% per day in freshwater.

3.3 Watershed Model Limitations and Sources of Uncertainty
As with any model, this modeling approach is subject to limitations and sources of
uncertainty. One limitation of the model pertains to the time step. The model was
performed on an hourly time step, and as such it is not sensitive to changes in rainfall
intensities over time steps of less than an hour. Another limitation of the model is its
inability to account for increased fecal coliform accumulation on land surfaces with
increased durations between rainfall events. A third limitation is the model’s inability to
account for antecedent soil moisture conditions. However, over a five-year modeling
period, the effect of antecedent conditions is negligible.
There are also several sources of uncertainty in the model. The most significant source
of uncertainty is the precipitation data. Precipitation data gathered by volunteers for the
NCCF demonstrate the variability in rainfall intensity across the watershed. For example,
values were found to range from 1 to 3.5 inches for a single storm on September 26,
2008. Only one complete data record was available for a precipitation gage within the
watershed, and data from 2 gages outside of the watershed were included in order to
account for this variability in precipitation across the watershed. Additionally, the lack of
a precipitation gage near the stream gage presents a source of uncertainty. With no
precipitation gage nearby, model results predict stormflows where the gage shows none
and vice versa. For example, as seen in Figure 7 the model predicted a large storm
event on June 14, 2009, though none was observed at the stream gage, and similarly on
November 2008 as seen in Figure 6. Over 1.5 inches of precipitation was recorded at
the NNAC gage on that date (an input to the model), but given the variability of
precipitation in the watershed, it is possible that a storm event did not occur in the
drainage area of the stream gage. The resulting discrepancies between modeled and
observed flow are discussed previously in Section 3.1.5.

E-25

4.0 Tidal Prisms Water Quality Model
The receiving-water quality model used was the Tidal Prism Water Quality Model
(TPWQM) developed by Kuo and Park (1994). The tidal prism model simulates physical
transport processes in terms of the concept of tidal flushing. Detailed documentation of
the model theory and input files is provided in A PC-Based Tidal Prism Water Quality
Model for Small Coastal Basins and Tidal Creeks (Kuo & Park 1994). Steps in
developing the TPWQM for the Lockwoods Folly River included segmenting the estuary,
creating a linkage between the watershed loading model and the estuary receiving-water
quality model through VBA scripting, calibrating the model to water quality data, and
calculating the TMDL.
4.1 Segmentation
The TPWQM segmentation scheme requires data on the geometry and tidal range of the
estuary. Bathymetry data for the Lockwoods Folly channel through the estuary was
obtained from the US Army Corps of Engineers. In addition, field bathymetry data points
were collected by the NC Coastal Federation throughout the estuary. An inverse-
distance-weighted interpolation of the bathymetry data points was generated in GIS to
represent a Mean Tide Level depth surface for the estuary. Tidal range data was
collected from the NOAA Tide monitoring station at the Lockwoods Folly Inlet. The mean
tidal range was reported to be 4.2 feet (NOAA, 2009). GIS techniques were used to
calculate low tide volume and intertidal volume at any given point along the estuary from
the interpolated depth and tidal range data. These volumes along with freshwater flows
were used to develop the model segmentation as described below.
The first transect of the segmentation is situated across the mouth of the estuary. The
location of the second transect is selected such that a water particle will move from the
first to the second transect over the flood tide. Therefore, the intertidal volume (i.e. the
tidal prism) upriver of the second transect must be large enough to accommodate the
low tide volume in the second segment and the volume of freshwater flows upriver of the
second segment over flood tide. The theory and equations of this segmentation scheme
are described in detail in Kuo & Park (1994).
A segmentation program (Geo-TPM) was developed by the Virginia Institute of Marine
Science for a separate tidal prism model developed for permitting purposes. This
program does not incorporate the contribution of freshwater flows to an estuary. The
freshwater volume to the Lockwoods Folly estuary was found to be negligible in
comparison to the tidal volume. Therefore, the Geo-TPM program was used in
conjunction with the tidal volume data to calculate the segments of the estuary. The
segmentation resulted in four segments with the first segment being the seaward
boundary. The second, third, and fourth segments move upriver into the estuary. In the
TPWQM, all freshwater flows and fecal coliform loads are modeled as entering into the
third segment (M0S3) of the estuary via the Lockwoods Folly River. The TPWQM
calibration point (Site 7A) is located in Segment M0S2 (Figure 9). The segmentation
data is also used to develop the geometry input file of the TPWQM (Appendix B – GEO-
HYD.IN).
E-26

Figure 9. Estuary model segmentation
Spring Creek
Mullet Creek
Lockwoods Folly River
Mill Creek
Lockwoods
Creek
M0 S2
M0 S3
M0 S4
8
7
9A
11
10
13
7A
6A
5A
14B
14A
TPWQM segments
DEHSS monitoring stations
NCCFmonitoring station 0 1,000 2,000500Feet
E-27

4.2 Watershed Loading Model – TPWQM Linkage
The TPWQM model utilizes a series of text files which are pulled in by an executable file
for the model. Only three text input files were manipulated in modeling fecal coliform in
the Lockwoods Folly River with the TPWQM: 1) test_lb.in (the toggle file which indicates
which parameters and conditions are utilized); 2) GEO-HYD.IN (includes geometry
parameters and the return ratio for each model segment); and 3) CAL-NPS.IN (the file
which houses the spatially and temporally varying flow and load values generated from
the watershed model). Final files of the test_lb.in and GEO-HYD.in, and an excerpt from
the CAL-NPS.IN file are included in Appendix B.
While the first two files can be manipulated easily and directly in a simple text reader
program, the CAL-NPS.IN file had to contain four years of flow and fecal coliform load
data on a time step of tidal cycles. Therefore, a Visual Basic Script was created to
generate an appropriately formatted text file from the final flow and fecal coliform loading
generated from the watershed model (Section 3.2 and Appendix A). The VBA script
includes three subroutines. The three subroutine scripts are included in Appendix C. The
VBA script aggregates hourly flow and loads generated by the watershed loading model
up to the tidal cycle for input into the TPWQM.
4.3 TPWQM Model Calibration
Calibration point selection 
The TPWQM calibration was conducted based on the comparison of model simulated
and observed fecal coliform concentrations in the estuary. Several factors were
considered in selecting monitoring sites for the model calibration. These factors included
current water quality violations, past water quality violations, robustness of the data
record, and location of the site in the estuary. Site 8 is the only monitoring site currently
violating water quality standards (as of October 2009). However, this site is located
along the shoreline in the southeastern portion of model segment M0S2 in the estuary
and is less influenced by tidal mixing than sites located in the center of the estuary. Sites
7 and 7A are centrally located in model segment M0S2 of the estuary (Figure 9). Both
sites have the most complete data records of the monitoring sites, including the most
extensive conditional monitoring records. While these sites are not currently violating
water quality standards they did demonstrate the highest fecal coliform levels prior to the
2007 drought.
Model results for model segment M0S2 were compared to observed data at sites 7A and
8 during the calibration. Site 7A was selected as a calibration point for the TPWQM due
to its central location in the estuary and its extensive data record. Additionally, the
calibration was optimized by comparing model results to observed data at Site 8 to
ensure that the calibrated model accurately represents both past and current water
quality violations.
Calibration 
The two parameters that can be adjusted within the TPWQM during calibration are the
return ratio and the fecal coliform decay rate. The return ratio is the fraction of water
leaving the estuary during the ebb tide that will be transported back to the estuary during
the next flood tide. The return ratio ranges from 0 to 1. Past studies of the TPWQM have
demonstrated that the calculated salinity is relatively insensitive to the value of return
E-28

ratio between 0.1 to 0.5 and the value of 0.3 works well for small creeks in Virginia (Kuo,
et al. 1998). Return ratio was adjusted during model calibration for the Lockwoods Folly
estuary. It was found that the Lockwoods Folly estuary is also insensitive to adjustments
in return ratio. The final return ratio selected for the Lockwoods Folly TPWQM was 0.3.
The first order decay is used in the model to represent the fecal coliform die-off due to
temperature, salinity, solar radiation, and loss due to settling and other factors. A system
with a higher decay rate has a higher assimilative capacity than a system with a lower
decay rate. The value of decay rate varies from 0.7 to 3.0 per day in salt water (Mancini
1978; Thomann and Mueller 1987). A decay rate of 0.7 per day was used for the
Lockwoods Folly estuary as a conservative estimate in the TMDL model.
Fecal coliform loads to the estuary were also adjusted during the TPWQM model
calibration. The calibration procedure involved adjusting the multiplier and divisor values
described in Section 3.2.1 which adjust the fecal coliform concentrations in runoff over a
storm event. The final values for the multiplying and dividing factors were selected such
that the modeled fecal coliform concentrations in Segment M0S2 of the estuary fell
within the range of observed values at Site 7A and Site 8 during the model simulation
period. Additionally, it was verified that the model results approximated the observed 30-
sample 90th percentile over the 5-year model simulation period . The 90th percentile is a
criterion used by DEHSS as a standard for shellfish use ratings. Model results and
observed values for Site 7A are presented in Figure 10. The comparison of the model
30-month 90th percentile and Site 7A observed 90th percentile are presented in Figure
11. Note that in Figure 11, each point represents the 90th percentile of the previous 30
months. Therefore, from 2004 to 2009 the first modeled point appears in July of 2006.
Figure 12 depicts the comparison of model results to observed fecal coliform levels at
Site 8. The comparison of the modeled and Site 8 observed 30-month 90th percentiles is
presented in Figure 13.
The observed measurements show the lowest concentration is always 1.7 MPN/100ml.
This is due to the laboratory methods used for determining the fecal coliform counts. The
model was not able to consistently capture these low concentration events. The model
may not have captured these lower baseline values due to the length and shallow
geometry of the estuary and an inability to model sufficient tidal flushing. However, the
high concentration is more critical for determining the bacteria capacity of the estuary.
The 5-year model simulation period demonstrated seasonal variability and captured
peak fecal coliform concentrations compared to observed data. Given the long-term
simulation results, the overall model performance is satisfactory.
E-29

1
10
100
1000
01/01/04 05/15/05 09/27/06 02/09/08 06/23/09
Fe
c
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(
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/
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Date
Observed FC (7A)
Modeled FC

Figure 10. Modeled fecal coliform concentration for model segment M0S2 and observed
fecal coliform concentration at Site 7A

0
20
40
60
80
100
120
140
160
180
6/22/2006 1/8/2007 7/27/2007 2/12/2008 8/30/2008 3/18/2009 10/4/2009
Fe
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(
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/
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)
Date
90th percentile standard
7A 90th percentile
Modeled 90th percentile

Figure 11. Modeled 90th percentile fecal coliform concentration for model segment M0S2
and observed 90th percentile fecal coliform concentration at Site 7A

E-30

1
10
100
1000
1/1/2004 5/15/2005 9/27/2006 2/9/2008 6/23/2009
Fe
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(
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m
L
)
Date
Observed FC (Site 8)
Modeled FC

Figure 12. Modeled fecal coliform concentration for model segment M0S2 and observed
fecal coliform concentration at Site 8

0
20
40
60
80
100
120
140
160
180
200
6/22/2006 1/8/2007 7/27/2007 2/12/2008 8/30/2008 3/18/2009 10/4/2009
Fe
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(
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/
1
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)
Date
90th percentile standard
Site 8 90th percentile
Modeled 90th percentile

Figure 13. Modeled 90th percentile fecal coliform concentration for model segment M0S2
and observed 90th percentile fecal coliform concentration at Site 8

E-31

4.4 TPWQM Model Assumptions
Several assumptions were made in running the tidal prism model and include the
following:
• Downstream (seaward) boundary conditions remain constant. The TPWQM requires
input data regarding of boundary conditions regarding pollutant concentration. A
constant boundary condition for fecal coliform was set to 0. This is a conservative
assumption which thereby models all fecal coliform loads as coming from the estuary
and not from outside the mouth of the estuary.
• The contribution of septic systems to fecal coliform loading is included in the
baseflow loads of the watershed model. A separate input to the estuary for septic loads
was not modeled.
• There are no point sources contributing fecal coliform loads to the estuary.
• A daily record of temperature was not available at different points in the estuary.
Therefore, a constant temperature of 20 °C was utilized. Temporally varying
temperatures can be simulated; however, the use of constant temperature was selected
in order to improve modeled baseline concentration results.
4.5 TPWQM Model Limitations and Sources of Uncertainty
The TPWQM is subject to limitations and sources of uncertainty. One limitation pertains
to segmentation. Segmentation is performed on the basis of the geometry of the estuary.
Several monitoring sites are present across an individual model segment in the
Lockwoods Folly estuary. While variability exists between these monitoring sites, the
model is not able to capture variability within a model segment.
The TPWQM is a receiving-water quality model and the results therein are affected by
the uncertainties associated with the loading model. These uncertainties are discussed
in Section 3.3. The most sensitive calibration parameter in the TPWQM is the decay rate
of fecal coliform. Decay is a variable parameter affected by temperature and salinity. A
conservative value of 0.7 was selected for the decay rate in order to minimize the
possibility of under predicting fecal coliform concentrations in the estuary. Due to the
high variability of the nature of fecal coliform, it is understandable that the model may fail
to simulate some isolated events.
4.6 TMDL Calculation
The existing load (or current condition) is estimated as the sum of all the loads from
subwatersheds discharging into the estuary. The loading is expressed as counts per
day. The TMDL calculation is based on the water quality criteria; in this case it is the
median and 90th percentile for the most recent 30 samples. Since the samples are taken
on an approximately monthly basis (i.e., samples can be taken in any month), the
running 30-month median and 30-month 90th percentile were calculated for the model
segment containing the TPWQM calibration point (Segment M0S2). The watershed
loading was reduced until both water quality standards were met at all times during the
model simulation period. The final load is the maximum allowed daily load, or TMDL.
The load reduction is calculated as the difference between the current condition and the
TMDL loading. A summary of existing load and TMDL loading is presented in Table 9.
The model time series plots of both the running 30-month median and 90th percentile for
Segment M0S2 of the estuary under existing conditions and with the TMDL loading are
presented in Appendix D.
E-32

Table 9. TMDL summary
Waterbody Pollutant
Existing
Load WLA LA MOS TMDL
Reduction
Needed
Lockwoods Folly
River (15-25-1-
(16)c) Lockwoods
Folly River (15-25-1-
(16)a), Lockwoods
Folly River (15-25-1-
(16)b), Lockwoods
Folly River (15-25-1-
(16)d), Mill Creek,
Mullet Creek, Spring
Creek, Lockwoods
Creek
Fecal
coliform
(counts/day)
6.910E+12 2.097E+11 7.855E+11 1.106E+11 1.106E+12 84%
WLA = wasteload allocation; LA = load allocation, MOS = margin of safety
4.7 Critical Condition
The EPA Code of Federal Regulations (40 CFR 130.7 (c)(1)) requires TMDLs to take
into account critical conditions for stream flow, loading, and water quality parameters.
The intent of this requirement is to ensure that the water quality of the waterbody is
protected during times when it is most vulnerable. The critical condition accounts for the
hydrologic variation in the watershed over many sampling years whereas the critical
period is the condition under which a waterbody is the most likely to violate the water
quality standard(s).
The 90th percentile concentration is the concentration exceeded only 10% of the time.
Since the model simulation period spans 5 years, the critical condition is implicitly
included in the value of the 90th percentile of model results. Given the length of the
monitoring record and model simulation and the standard’s recognition of unusual and
infrequent events, the 90th percentile is used instead of the absolute maximum.
4.8 Seasonality
Fecal coliform distributions often show high seasonal variability, which is required to be
considered in TMDL determinations. The seasonal fecal coliform distributions of
observed data at Sites 7A and 8 are presented in Figures 14 and 15. The results show
that high fecal coliform levels occur throughout the year in the estuary. The average
monthly concentrations are relatively similar between months at both sites, though Site
7A shows slightly more variation. The highest concentrations occur in April at both
monitoring sites. The lowest concentrations occur in February and the late spring
months.
The largest standard deviation corresponds to the highest concentration for each station.
These high concentrations result in a high 90th percentile concentration. Given the length
of the model simulation, the seasonal variability is directly included in the model
simulation.

E-33

1
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1 2 3 4 5 6 7 8 9 10 11 12
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Site 7A

Figure 14. Seasonal distribution of fecal coliform concentration at Site 7A (log scale)

1
10
100
1000
1 2 3 4 5 6 7 8 9 10 11 12
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Site 8

Figure 15. Seasonal distribution of fecal coliform concentration at Site 8 (log scale)

4.9 TMDL Loading Cap
This section presents the TMDL for the median and 90th percentile conditions for the
E-34

Lockwoods Folly estuary and tidal creeks. The TMDL was calculated based on the
model simulation results. The TMDL for the estuary was calculated to be 1.106 x 1012,
with the TMDL calculation period from 7/1/2004 to 1/1/2007. The greater reduction
required when comparing the median and the 90th percentile results was used for the
TMDL. Based on model results, the 90th percentile is the stricter standard which requires
the greatest reduction.
The TMDL calculation period is the 30 months preceding the last daily prediction to meet
the standard. Thus, the averaging period for the development of the TMDL used daily
predictions from the TMDL model runs for the 30 months preceding the highest 90th
percentile concentration over the model simulation period. Over this calculation period,
daily bacteria loading predictions were taken from each model subwatershed and
subsequently summed across the watershed. The daily average load was then
calculated over the 30-month period. As seen in Figure D1 (Appendix D) the highest 90th
percentile during the model simulation period occurred on 1/1/2007. Thus, the TMDL
was calculated for the 30 months from 7/1/2004 to 1/1/2007.
Load reductions required to meet the TMDL are 84% (excluding the MOS). The
reduction established based on the 90th percentile criterion indicates that the waterbody
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.
4.10 Wasteload Allocation
The wasteload allocation pertains to NPDES-permitted point sources. There are no
wastewater discharges in the watershed. There are two main NPDES stormwater
permitees in the watershed: NCDOT and the Town of Oak Island, a Phase II community.
Surface and ground water from the Town of Oak Island drains to the ICWW and
Mongtomery Slough. As mentioned in Section 2.1.1, these two waterbodies do not drain
to the Lockwoods Folly estuary and the hydrodynamics of these waterways are not
conducive to using the linked watershed and Tidal Prism modeling approach. Therefore,
a WLA could not be calculated for the Town. The Town will be addressed in the TMDL
Implementation Plan as well as future stormwater permits. There are also four industrial
stormwater permittees which include sand pits, and concrete and asphalt facilities which
are not of concern with regards to fecal coliform. Therefore, NCDOT is the only bacteria
source accounted for in the WLA.
Bacteria loading coming from NCDOT land was isolated from other sources using the
delineated land use and calibrated model as a base. The model was rerun setting the
EMC on NCDOT land to zero. The difference between the calibrated model run and the
model run without NCDOT represents NCDOT’s existing fecal coliform load to the
Lockwoods Folly estuary. The existing NCDOT load was calculated over the same time
period as the TMDL calculation (7/1/2004 – 1/1/2007), with a result of 4.46 x 1011 counts
per day. NCDOT’s contribution is 6% of the total fecal coliform load from the watershed
to the estuary. The required reduction from NCDOT land was calculated to be 53% % of
their existing load. This reduction is based on NCDOTs relative contribution to fecal
loads using its EMC values compared to a developed land area weighted EMC value
that was calculated using land use area (Table 2) and corresponding EMC values (Table
8). The resulting WLA is 2.097 x 1011 counts per day. This value and the margin of
safety are subtracted from the TMDL loading cap to determine the final LA.
E-35

4.11 Load Allocation
The load allocations were determined using the same period as the TMDL calculation.
Thus, the averaging period for the development of the TMDLs used daily predictions
from the TMDL model runs for the 30 months preceding the highest 90th percentile
concentration over the TMDL period. Over this period, daily bacteria loading predictions
were taken from each model subwatershed and subsequently summed across the
watershed. The daily average load was then calculated which serves as the basis for the
load allocation. The wasteload allocation (WLA) and the margin of safety (MOS) were
subtracted from the TMDL to determine the final load allocation (LA).
4.12 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 waterbodies. The MOS is intended to account
for such uncertainties in a manner that is conservative from the standpoint of
environmental protection.
For TMDL development, the MOS needs to be incorporated to account for uncertainty
due to model parameter selection. Based on previous model sensitivity analysis, it has
been determined that the most sensitive parameter is the decay rate. The value of the
decay rate varies from 0.7 to 3.0 per day in salt water (Mancini, 1978; Thomann and
Mueller, 1987, EPA 1985). A decay rate of 0.7 per day in the estuary was used as a
conservative estimate in the TMDL model. An explicit MOS was also included in the
TMDL calculation as a conservative estimate. The explicit MOS was achieved by
applying a 10% load reduction from the calculated TMDL.
With the MOS included, the total required reduction in load is 86%.
4.13 Summary of Total Maximum Daily Loads
As explained in the previous sections, the TMDL was calculated based on model runs
that had a maximum 30-month 90th percentile concentration of 43 MPN/100 ml.
Additionally an explicit margin of safety of 10% was applied to the TMDL load. NCDOT is
the only NPDES-permitted source in the area so its allocation is in the WLA column. The
TMDL is calculated based on the 30 months preceding the last highest 90th percentile
concentration in the TMDL model runs and is summarized as follows:

E-36

Waterbody Pollutant
Existing
Load WLA LA MOS TMDL
Reduction
Needed*
Lockwoods Folly
River (15-25-1-
(16)c) Lockwoods
Folly River (15-25-
1-(16)a),
Lockwoods Folly
River (15-25-1-
(16)b), Lockwoods
Folly River (15-25-
1-(16)d), Mill
Creek, Mullet
Creek, Spring
Creek, Lockwoods
Creek
Fecal
coliform
(counts/day)
6.910E+12 2.097E+11 7.855E+11 1.106E+11 1.106E+12 84%
Where:
TMDL = Total Maximum Daily Load
LA = Load Allocation (Nonpoint Source)
WLA = Waste Load Allocation (Point Source)
MOS = Margin of Safety
*When the MOS is included, the total required reduction is 86%
E-37

5.0 References
Baird, C.F., Dybala, T.J., Jennings, Marshall, and Ockerman, D.J., 1996,
Characterization of nonpoint sources and loadings to the Corpus Christi Bay National
Estuary Program study area: Corpus Christi Bay National Estuary Program, CCBNEP–
05, 226 p
Bales, J.D., J.C. Weaver, and J.B. Robinson. 1999. Relation of land use to streamflow
and water quality at selected sites in the City of Charlotte and Mecklenburg County,
North Carolina, 1993-1998. USGS Water Resources Investigations Report 99-4180.
Raleigh, NC.
Center for Watershed Protection (CWP) 2003. Impacts of impervious cover on aquatic
systems. Watershed Protection Research Monograph No. 1.
CWP 1999. Microbes and Urban Watersheds – Concentrations, Sources and Pathways.
Watershed Protection Techniques 3(1): 554 – 565. Center for Watershed Protection.
Daniels, RB, SW Buol, HJ Kleiss, and CA Ditzler 1999. Soil systems in North Carolina.
Technical Bulletin 314. North Carolina State University Soil Science Department.
Driver, N 1988. National summary and regression models of storm-runoff loads and
volumes in urban watersheds in the United States. Thesis. Colorado School of Mines.
Golden, Colorado
Eleria, A. and R.M. Vogel 2005. Predicting fecal coliform bacteria levels in the Charles
River, Massachusetts, USA. Journal of the American Water Resources Association 41
(5):1195-1209.
Elshorbagy A., L. Ormsbee (2005). Object-oriented modeling approach to surface water
quality management. Environmental Modelling & Software 21 (2006): 689-698.
Fine, J.M. and W.L. Cunningham. 2001. Compilation of water-resources data and
hydrogeologic setting for Brunswick County, North Carolina, 1933–2000. U.S. Geological
Survey Open-File Report 01–240.
Kuo, A.Y., K. Park 1994. A PC-based Tidal Prism Water Quality Model for small coastal
basins and tidal creeks. Special Report No. 324. Virginia Institute of Marine Science,
The College of William and Mary. Gloucester Point, VA.
Kuo, A.Y., A. Butt, S. Kim, and J. Ling (1998). Application of a Tidal Prism water quality
model to Virginia Small Coastal Basins. SRAMSOE No. 348.
Lumb, A.M., McCammon, R.B., and Kittle, J.L., Jr. 1994. User’s manual for an expert
system (HSPEXP) for calibration of the Hydrologic Simulation Program-FORTRAN. U.S.
Geological Surve Water-Resources Investigations Report 94-4168. U.S. Geological
Survey.
Mallin, M.A., K.E. Williams, E.C. Esham, and R.P. Lowe 2000. Effect of human
development on bacteriological water quality in coastal watersheds. Ecological
Applications 10(4): 1047-1056.
Maestre, A. and R. Pitt 2005. Identification of significant factors affecting stormwater
quality using the NSQD. Computational Hydraulics International (CHI) Draft Monograph.
E-38

Mancini, J. L. (1978). Numerical estimates of coliform mortality rates under various
conditions. Journal Water Pollution Control Federation 50(11): 2477-2484.
NC CRONOS 2009. NC CRONOS Database. The State Climate Office of North
Carolina. http://www.nc-climate.ncsu.edu/cronos/.
NCDENR 2007. Total Maximum Daily Loads for Fecal Coliform for Jarrett Bay and Its
Embayment, North Carolina. North Carolina Department of Environment and Natural
Resources, Division of Water Quality.
NCDENR 2009. Total Maximum Daily Loads for Fecal Coliform for Embayments in
Southeast White Oak River, North Carolina. North Carolina Department of Environment
and Natural Resources, Division of Water Quality.
Newell, C.J., H.S. Rifai, P.B. Bedient (1992). Characterization of non-point sources and
loadings to Galveston Bay. GBNEP-15. Prepared for the Northern Virginia Regional
Commission.
NOAA 2009. Tidal Station Locations and Ranges. National Oceanic and Atmospheric
Administration. http://tidesandcurrents.noaa.gov/tides07/tab2ec3a.html
Pitt, R., A. Maestre, and R. Morquecho 2005. The National Stormwater Quality Database
(NSQD, version 1.1). 3/04/2005
http://unix.eng.ua.edu/~rpitt/Research/ms4/mainms4.shtml
SCS 1975. Urban hydrology for small watersheds, Technical Release No. 55. Soil
Conservation Service. United States Department of Agriculture. Washington, D.C.
SCS 1988. Soil Survey of Brunswick County, North Carolina. Soil Conservation Service.
US Department of Agriculture.
Tetra Tech. 2004. Technical Memorandum – Task 1: Impact Analysis Town Center
Stormwater. Management Plan. Prepared for the Town of Cary.
Thomann, R. V. and J. Mueller (1987). Principles of surface water quality modeling and
control. Harper Collins Publishers.
Tufford, D.L. and W.D. Marshall 2002. Fecal coliform source assessment in a small,
mixed land use watershed. Journal of the America Water Resources Association 38(6):
1625-1635.
USACE 2008. Hydrologic Modeling System HEC-HMS User’s Manual Version 3.3. US
Army Corps of Engineers. Hydrologic Engineering Center. Davis, California.
USEPA 1983. Nationwide Urban Runoff Program. United States Environmental
Protection Agency, Washington, D.C. December 1983.
USEPA 2001. PLOAD version 3.0, An ArcView GIS tool to calculate nonpoint sources of
pollution in watershed and stormwater projects. United States Environmental Protection
Agency, Washington, D.C. January 2001.
USGS 2000. Equations for estimating Clark unit-hydrograph parameters for small rural
watersheds in Illinois. Water Resources Investigations Report 00-4184. United States
Geological Survey. Urbana, Illinois.
E-39

Yagow, G., T. Dillaha, S. Mostaghimi, K. Brannan, C. Heatwole, M.L. Wolfe 2001. TMDL
modeling of fecal coliform bacteria with HSPF. Written for presentation at the 2001
ASAE Annual International Meeting. Sacramento, California.
Young, K.D. and E.L. Thackston. 1999. Housing density and bacterial loading to urban
streams. Journal of Environmental Engineering 125(12): 1177-1180.
Zarriello, PJ, LK Barlow, and US EPA, and Massachussetts Department of Environmntal
Protection and US Geological Survey 2002. Measured and simulated runoff to the lower
Charles River, Massachussetts.

E-40

Appendix A. Instructions for Navigating the Watershed Loading Excel
Spreadsheets and Generating the TPWQM Input File CAL-NPS.IN
1. Run HEC-HMS model.
2. Select the results tab.
3. Select Subbasin-1, then Time-Series Table. Copy columns labeled Direct Flow
and Baseflow. Paste these columns into the MS Excel file “Subbasin_1.xls” in
column “BX” (highlighted yellow) at the proper row corresponding to the lag time
between this Subbasin-1 and the Estuary. (Lag times are included in MS Excel
File “Lag Time per subbasin to Estuary.xls”). For convenience, the lag time has
been highlighted in column “BT”. Column “BT” is labeled for hourly offsets.
4. Repeat step three (3) for each of the 27 subbasins, in their respective MS Excel
files.
5. Copy columns “C” and “D” from Subbasin_1.xls.
6. Paste the columns into “Lockwoods Final Watershed Results_multistep-
loading_with_losses.xls” MS Excel file in the worksheet named “by_subbasin”,
under the appropriate subbasin heading, Subbasin-1 at columns “BG” and “BH”.
7. Repeat steps 5 and 6 for each of the 27 subbasin files, pasting data in the
appropriate columns, beginning at “BG” and “BH” for Subbasin-1 and ending at
columns “DG” and “DH” for Subbasin-27. (Note: This may require an
intermediate spreadsheet due to demands on RAM).
8. After all subbasin data is entered in the “Lockwoods Final Watershed
Results_multistep-loading_with_losses.xls”, in the “by_subbasin” worksheet,
calibration of fecal coliform loading can be conducted. Calibration parameters are
located in cells “D1” (% increase to trigger flushing effect), “F1” (multiplier for first
flush), “J1” and “H1” (divisors for post-flush). They change the proportional
adjustment of bacterial load for the first flush and afterwards, as well as
determining the increase in flow required to trigger “first flush” conditions.
9. The “Watershed_total” worksheet automatically calculates total Q and counts
entering the estuary on an hourly basis, for the duration of the simulation. In this
sheet, Column G shows the concentration of fecal coliform in the flow entering
the estuary. As a note, the simulation is not fully accurate until the beginning of
day 6 when the entire watershed is represented.
10. Copy Columns A through D in the “Watershed_total” worksheet. Paste them into
Columns A through D in the “Lockwoods Final Watershed Results MACRO.xls”
MS Excel file in worksheet “Sheet 1”. (Note, click ‘Enable Macros’ when opening
this MS Excel File). Follow instructions in the worksheet to generate the
CAL_NPS.IN loading file for the tidal prisms model.

To Change Event Mean Concentrations (EMC)
1. EMC values may be changed in the MS Excel file “Lockwoods Output.xls” in the
worksheet titled “Load Factor Data Sheet”. Columns A through P in Row 5 list
base EMC values used which apply to direct runoff. They may be adjusted
directly in this file. Columns R through AG list EMC values attributed to baseflow.
The current model assumed baseflow EMC’s to be 25% of runoff EMC’s as a
starting point. This may be adjusted, for each land use type, by changing the
decimal value in Row 1. Recall that divisors were applied to these values as
described in Section 4.3 of the model documentation.
2. After changing the values in “Lockwoods Output.xls”, each subbasin sheet must
be reopened to allow it to calculate new loadings using the altered data. Pasting
E-41

data from HEC-HMS may be omitted as flow values have not changed. (Resume
from step 5 above.)
E-42

Appendix B. TPWQM Input Files
GEO-HYD.IN

LOCKWOODS FOLLY
: updated geometry - 20100311
: Hydrodynamics and geometry input

4 0 Lockwoods Folly Estuary
0

$$$ geometry and hydrodynamic input $$$
(km) (10^6 m^3) (m)
CH S# DIST VH P AL HA
M 0 1 0.000 0.0 3.171 0.3 0.000
M 0 2 1.830 3.179 0.783 0.3 1.062
M 0 3 2.490 0.774 0.239 0.3 1.188
M 0 4 3.100 0.271 0.000 0.3 0.828
E-43

Test_lb.IN

LOCKWOODS FOLLY TMDL:
: control input file
: for control parameters and constant WQ parameters

$$$ I/O control variables $$$
iPLT iWQV iTMP iBEN iSi iTSS iSRP iFCB
0 1 0 0 0 0 0 1
iUKin iBcS iZK iNR iNC
1 0 1 1 1
Lsal LBc LBd Lpo4 Lnh4 Lno3 Lsa Lo2 Ltmp
1 0 0 0 0 0 0 0 1
iICI iAGR iSTL iSUN iPSL iNPL
0 0 0 0 0 1
iBCS iBCB iBCCO iBCPO iBCPI iBCNO iBCNI iBCSUP iBCSA
0 0 0 0 0 0 0 0 0
iBCCOD iBCO2 iBCTSS iBCTAM iBCFCB iBCT
0 0 0 0 0 0
Tstrt COV
2.0000 1.0E-6
iTmax Nprn iTimeS iSTS iETS
4087 4 1 0 4087
iTSCH iTSSEG
0 2
Tout(j)
2 3 7 8

$$$ constant parameters for ALGAE (see Table 3-1) $$$
KHNc KHNd KHNg KHPc KHPd KHPg KHS STOX
0.01 0.01 0.01 0.001 0.001 0.001 0.05 1.0
KeTSS KeChl CChlc CChld CChlg DOPTc DOPTd DOPTg
0.018 0.060 0.06 0.06 0.06 0.1 0.1 0.1
I0 IsMIN FD CIa CIb CIc
400.0 40.0 0.5 0.7 0.2 0.1
TMc TMd TMg KTG1c KTG2c KTG1d KTG2d KTG1g KTG2g
20.0 20.0 25.0 0.005 0.005 0.004 0.006 0.008 0.010
TRc TRd TRg KTBc KTBd KTBg
20.0 20.0 20.0 0.069 0.069 0.069

$$$ constant parameters for CARBON (see Table 3-2) $$$
FCRP FCLP FCDP FCDc FCDd FCDg KHRc KHRd KHRg
0.35 0.55 0.10 0.0 0.0 0.0 0.5 0.5 0.5
KRC KLC KDC KRCalg KLCalg KDCalg
0.005 0.075 0.01 0.0 0.0 0.0
TRHDR TRMNL KTHDR KTMNL KHORDO KHDNN AANOX
20.0 20.0 0.069 0.069 0.5 0.1 0.5

$$$ constant parameters for PHOSPHORUS (see Table 3-3) $$$
FPRP FPLP FPDP FPIP FPRc FPRd FPRg FPLc FPLd FPLg
0.1 0.2 0.5 0.2 0.0 0.0 0.0 0.0 0.0 0.0
E-44

FPDc FPDd FPDg FPIc FPId FPIg KPO4p
1.0 1.0 1.0 0.0 0.0 0.0 0.066
KRP KLP KDP KRPalg KLPalg KDPalg CPprm1 CPprm2 CPprm3
0.005 0.075 0.1 0.0 0.0 0.2 41.1 40.0 200.0

$$$ constant parameters for NITROGEN (see Table 3-4) $$$
FNRP FNLP FNDP FNIP FNRc FNRd FNRg FNLc FNLd FNLg
0.35 0.55 0.10 0.0 0.0 0.0 0.0 0.0 0.0 0.0
FNDc FNDd FNDg FNIc FNId FNIg ANCc ANCd ANCg
1.0 1.0 1.0 0.0 0.0 0.0 0.167 0.167 0.167
ANDC rNitM KHNitDO KHNitN TNit KNit1 KNit2
0.933 0.07 1.0 1.0 27.0 0.0045 0.0045
KRN KLN KDN KRNalg KLNalg KDNalg
0.005 0.075 0.015 0.0 0.0 0.0

$$$ constant parameters for SILICA (see Table 3-5) $$$
FSPP FSIP FSPd FSId ASCd KSAp KSU TRSUA KTSUA
1.0 0.0 1.0 0.0 0.5 6.0 0.03 20.0 0.092

$$$ constant parameters for COD & DO (see Table 3-6) $$$
AOCR AONT KRO KTR KHCOD KCD TRCOD KTCOD
2.67 4.33 3.933 1.024 1.5 20.0 20.0 0.041

$$$ constant parameters for TSS, TAM, FCB & TEMPERATURE (see Table 3-7) $$$
RDTSS KHbmf BFTAM Ttam Ktam TAMdmx Kdotam KFCB TFCB
5.00 0.5 0.01 20.0 0.2 0.015 1.0 -0.7 1.07
TmpMax TmpMin DTmax Cp Rho KT Te
28.3 8.89 197.0 4186.0 1000.0 17.6 32.5

$$$ spatially/temporally constant INITIAL CONDITIONS $$$
Sal Bc Bd Bg RPOC LPOC DOC APCi
24.95 0.75 0.00 0.00 0.1469 0.2937 1.0280 0.024
RPOP LPOP DOP PO4t RPON LPON DON NH4 NO3
0.0084 0.0168 0.0590 0.0282 0.0573 0.1145 0.4009 0.0630 0.0100
SU SA COD DO TSS TAM FCB T
0.5 0.5 0.00 6.20 10.0 10.0 22.91 20.00

$$$ spatially/temporally constant ALGAL PARAMETERS (/d except Keb in /m) $$$
PMc PMd PMg BMRc BMRd BMRg PRRc PRRd PRRg Keb
2.0 0.0 0.0 0.06 0.0 0.0 0.1 0.0 0.0 0.735

$$$ spatially/temporally constant SETTLING VELOCITIES (m/d) $$$
WSc WSd WSg WSrp WSlp WSs WStss
0.10 0.0 0.0 0.1 0.1 1.00 0.10

$$$ const/sin. varying DBC(g/m^3): S(ppt),TAM(mol/m^3),FCB(MPN/100mL),T(oC) $$$
c0S c1S c2S c0T c1T c2T APCd
21.4352 -4.56044-.25682714.452 -4.79258-8.666240.024
c0Bc c1Bc c2Bc c0Bd c1Bd c2Bd c0Bg c1Bg c2Bg
0.58925 0.11442 0.28081 0.0 0.0 0.0 0.0 0.0 0.0
c0C1 c1C1 c2C1 c0C2 c1C2 c2C2 c0C3 c1C3 c2C3
E-45

0.58972 0.07577 -0.017341.17943 0.15155 -0.121354.12802 0.53041 -0.12135
c0P1 c1P1 c2P1 c0P2 c1P2 c2P2 c0P3 c1P3 c2P3
0.0044 0.0 0.0 0.088 0.0 0.0 0.0308 0.0 0.0
c0PO4t c1PO4t c2PO4t
0.016 0.0 0.0
c0N1 c1N1 c2N1 c0N2 c1N2 c2N2 c0N3 c1N3 c2N3
0.0347 0.0 0.0 0.0693 0.0 0.0 0.2426 0.0 0.0
c0NH4 c1NH4 c2NH4 c0NO3 c1NO3 c2NO3
0.06 0.0 0.0 0.0187 0.0 0.0
c0SU c1SU c2SU c0SA c1SA c2SA
0.0 0.0 0.0 0.0 0.0 0.0
c0COD c1COD c2COD c0O2 c1O2 c2O2
0.0 0.0 0.0 8.94949 1.54105 1.4146
c0TSS c1TSS c2TSS c0TAM c1TAM c2TAM c0FCB c1FCB c2FCB
0.0 0.0 0.0 0.0 0.0 0.0 15.3671 -2.128435.79289

$$$ constant benthic flux (g/m^2/d) $$$
PO4 NH4 NO3 SA COD DO
0.006 0.012 0.005 0.00 0.00 -1.8

$$$ const PS(kg/TC):
PSQ(m^3/s),S(ppt),DO(g/m^3),TAM(kmol/TC),FCB(MPN/100mL),T(C) $$$
MC 0
BR 0
ST 0
CH S# PSQ Sal Bc Bd Bg RPOC LPOC DOC
RPOP LPOP DOP PO4t RPON LPON DON NH4 NO3
SU SA COD DO TSS TAM FCB T

$$$ const NPS(kg/TC):
DSQ(m^3/s),S(ppt),DO(g/m^3),TAM(kmol/TC),FCB(10^9MPN/TC),T(C) $$$
DSQ Sal Bc Bd Bg RPOC LPOC DOC
0.0000 0.00 0.00 0.00 0.00 0.000 0.000 0.000
RPOP LPOP DOP PO4t RPON LPON DON NH4 NO3
0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
SU SA COD DO TSS TAM FCB T
0.00 0.00 0.00 0.00 0.00 0.00 0.0 0.00

$$$ File names for spatially/temporally varying parameters: lower case only $$$
Input file for initial conditions = none
Input file for algal growth, resp, pred = none
Input file for settling vel of algae, part= none
Input file for Io, FD, KT, Te = none
Input file for downstream boundary condi. = none
Input file for benthic fluxes = none
Input file for temperature = none
Input file for point source input = none
Input file for NPS input inc/ atm input = cal-nps.in
Input file for sediment model input coeff = none
Diagnostic file-zero K(inetics) = cal-k.log
Diagnostic file-negative R(esiduals) = cal-r.log
E-46

Diagnostic file-negative concentration = cal-nc.log
Diagnostic file-salinity = cal-sal.log
Diagnostic file-cyanobacteris = none
Diagnostic file-diatoms = none
Diagnostic file-PO4 = none
Diagnostic file-NH4 = none
Diagnostic file-NO3 = none
Diagnostic file-SA = none
Diagnostic file-O2 = none
Diagnostic file-temperature = none
Output file for longitudinal distribution = mld.dat
Output file for 1st time series output = mts-m0s2.out
Output file for 2nd time series output = none

E-47

CAL-NPS.IN (Excerpt – Tide Cycles 1 to 4)

C LOCKWOODS FOLLY
C Run 16a
C Hydrodynamics and geometry input

CH S# DSQ Sal Bc Bd Bg RPOC LPOC DOC
M 0 2 0.00000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
M 0 3 19.46 0.000 0.000 0.000 0.000 0.000 0.000 0.000
M 0 4 0.00000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
CH S# RPOP LPOP DOP PO4t RPON LPON DON NH4 NO3
M 0 2 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
M 0 3 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
M 0 4 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
CH S# SU SA COD DO TSS TAM FCB T
M 0 2 0.000 0.000 0.000 0.000 0.00 0.000 0.0 0.000
M 0 3 0.000 0.000 0.000 0.000 0.00 0.000 76.84 0.000
M 0 4 0.000 0.000 0.000 0.000 0.00 0.000 0.0 0.000
202 CON : 4/ 1/ 1 12.42

CH S# DSQ Sal Bc Bd Bg RPOC LPOC DOC
M 0 2 0.00000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
M 0 3 19.71 0.000 0.000 0.000 0.000 0.000 0.000 0.000
M 0 4 0.00000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
CH S# RPOP LPOP DOP PO4t RPON LPON DON NH4 NO3
M 0 2 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
M 0 3 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
M 0 4 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
CH S# SU SA COD DO TSS TAM FCB T
M 0 2 0.000 0.000 0.000 0.000 0.00 0.000 0.0 0.000
M 0 3 0.000 0.000 0.000 0.000 0.00 0.000 87.92 0.000
M 0 4 0.000 0.000 0.000 0.000 0.00 0.000 0.0 0.000
203 CON : 4/ 1/ 1 0.84

CH S# DSQ Sal Bc Bd Bg RPOC LPOC DOC
M 0 2 0.00000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
M 0 3 20.08 0.000 0.000 0.000 0.000 0.000 0.000 0.000
M 0 4 0.00000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
CH S# RPOP LPOP DOP PO4t RPON LPON DON NH4 NO3
M 0 2 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
M 0 3 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
M 0 4 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
CH S# SU SA COD DO TSS TAM FCB T
M 0 2 0.000 0.000 0.000 0.000 0.00 0.000 0.0 0.000
M 0 3 0.000 0.000 0.000 0.000 0.00 0.000 39.99 0.000
M 0 4 0.000 0.000 0.000 0.000 0.00 0.000 0.0 0.000
204 CON : 4/ 1/ 2 13.26

CH S# DSQ Sal Bc Bd Bg RPOC LPOC DOC
M 0 2 0.00000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
M 0 3 20.89 0.000 0.000 0.000 0.000 0.000 0.000 0.000
E-48

M 0 4 0.00000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
CH S# RPOP LPOP DOP PO4t RPON LPON DON NH4 NO3
M 0 2 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
M 0 3 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
M 0 4 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
CH S# SU SA COD DO TSS TAM FCB T
M 0 2 0.000 0.000 0.000 0.000 0.00 0.000 0.0 0.000
M 0 3 0.000 0.000 0.000 0.000 0.00 0.000 144.99 0.000
M 0 4 0.000 0.000 0.000 0.000 0.00 0.000 0.0 0.000
205 CON : 4/ 1/ 2 1.68

E-49

Appendix C. Watershed-TPWQM Linkage VBA Scripts
Subroutine 1

Sub RUN_ME_FIRST_TidalData_Summation()
'routine to display daily time in hours with decimal hours
'Clear Range that is written to
Columns("E:M").Select
Selection.ClearContents
Range("M1").Select
'End of Clear Range

Dim StartTime As Double
Dim hrsCounter As Double
Dim Counter As Double
Dim gonzoOld As Double
Dim StartRowFrac As Double 'variable used to count fraction of first row in rolling
calculations
StartRowFrac = 1
Dim FinishRowFrac As Double 'variable used to count fraction of last row in rolling
calculations
Dim TidalStepSize As Double 'time step in hours - set constant
TidalStepSize = 12.42 'hrs
Dim StartRowFracOld As Double
Dim FinishRowFracOld As Double
Cells(1, 11) = "FRF"
Cells(1, 10) = "SRF"
Cells(1, 13) = "Finish Row"
StartTime = 0
hrsCounter = 24
blabla = 2
gonzoOld = 1
Counter = 1
Cells(2, 10) = StartRowFrac
For i = 2 To 5000
'CELLS WRITING TO CONTINUOUS
Cells(Counter + 1, 12) = StartTime
'following line added
startRownum = Int(StartTime + 1)
Cells(Counter + 1, 13) = startRownum
'MsgBox ("SRF = " & Round(StartRowFrac, 6))
'END OF CONTINUOUS WRITING CELLS
'INSERTED ROUTINE TO CALC LOAD AND FLOW

'END OF INSERTED ROUTINE
Cells(1, 5) = "StartHr"
Cells(Int(StartTime + blabla), 5) = Int(StartTime + 1) '- 1 'elapsed hr of start
Cells(Int(StartTime + blabla), 6) = StartTime 'elapsed hrs decimal
Cells(Int(StartTime + blabla), 7) = (0.5175 * hrsCounter * Counter) - Int((0.5175 *
hrsCounter * Counter) / 24) * 24
E-50

Cells(Int(StartTime + blabla), 8) = Cells(Int(StartTime + 2), 1) - Cells(2, 1) 'elapsed days
Cells(Int(StartTime + blabla), 9) = (Cells(Int(StartTime + 2), 1) - Cells(2, 1)) * 24 'elapsed
days in hrs

FinishRowFrac = ((0.5175 * hrsCounter * Counter) - Int((0.5175 * hrsCounter * Counter) /
24) * 24) - Int((0.5175 * hrsCounter * Counter) - Int((0.5175 * hrsCounter * Counter) / 24)
* 24)
Cells(Int(StartTime + blabla), 11) = FinishRowFrac
'MsgBox ("FRF = " & Round(FinishRowFrac, 6))

StartTime = (0.5175 * hrsCounter * Counter)
StartRowFrac = 1 - FinishRowFrac
Cells(Int(StartTime + blabla), 10) = StartRowFrac
Counter = Counter + 1
'INSERTED ROUTINE TO CALC LOAD AND FLOW
'StartRowFracOld = StartRowFrac
'FinishRowFracOld = FinishRowFrac
'MsgBox ("FRF= " & Round(FinishRowFrac, 4))

'END OF INSERTED ROUTINE
Next i
End Sub
E-51

Subroutine 2

Sub RUN_ME_SECOND_sumtidal_data()
'subroutine to sum 1-hr tide step data over 12.24 hr cycle

'Clear Range that is written to
Columns("O:R").Select
Selection.ClearContents
Range("M1").Select
'End of Clear Range

Dim firstDataRow As Long
Dim startRownum As Long
Dim endRowNum As Long
Dim counter2 As Long
Dim sumQ As Double
Dim sumLoad As Double
Dim FRF As Double
Dim SRF As Double
firstDataRow = 1
counter2 = 1

Cells(1, 15) = "Date"
Cells(1, 16) = "Time"
Cells(1, 17) = "Flow"
Cells(1, 18) = "Load"

For i = 1 To 4000
'initialize sum variables
sumQ = 0
sumLoad = 0

startRownum = Cells(counter2 + firstDataRow, 13) + firstDataRow
endRowNum = Cells(counter2 + firstDataRow + 1, 13) + firstDataRow
SRF = Cells(startRownum, 10)
FRF = Cells(startRownum, 11)
sumQ = SRF * Cells(startRownum, 3) + FRF * Cells(endRowNum, 3)
sumLoad = SRF * Cells(startRownum, 4) + FRF * Cells(endRowNum, 4)
For j = (startRownum + 1) To (endRowNum - 1)
sumQ = sumQ + Cells(j, 3)
sumLoad = sumLoad + Cells(j, 4)
Next j
Cells(counter2 + 1, 15) = Cells(startRownum, 1)
Cells(counter2 + 1, 16) = Cells(startRownum, 7)
Cells(counter2 + 1, 17) = Round(sumQ, 2)
Cells(counter2 + 1, 18) = Round(sumLoad, 2)
counter2 = counter2 + 1

Next i
End Sub
E-52

Subroutine 3

Sub RUN_ME_THIRD_TPWQM_WriteCAL_NPS_InputFile()
'first set a string which contains the path to the file you want to create.
'this example creates one and stores it in the root directory
Dim botRow As Single
botRow = InputBox("Input the row number for the last row of data in Column O")
Dim Qtemp As Double
Dim QOut As String
Dim FCBtemp As Double
Dim FCBOut As String
Dim taggerOut As String
Dim taggerVal As String
'*******
Dim StartDate As Variant
Dim yy2 As String
Dim mm2 As String
Dim dd2 As String
Dim StartTimer As Single
Dim StartTimerOut As String
'*******
'Time Step Increment Formatting
Dim tStepInc As Integer
Dim tStepOut As String
'*************THE VALUE BELOW (SET BY MRC AT 202) IS THE START OF THE TIME
STAMP - USE NOT DOCUMENTS
'*************VALUE CAN BE EDITED
tStepInc = 202
'*************END OF COMMENT
tStepOut = Format(tStepInc, "@@@@@@@")
taggerVal = "0.000"
taggerOut = Format(taggerVal, "@@@@@@@@")
'*****EDIT THE LINE BELOW TO REDIRECT LOCATION AND NAME OF FILE.
SAMPLE LINE INCLUDED AFTER - REMOVE LEADING
'*****SINGLE " ' " TO ACTIVATE LINE AND PUT ONE IN FRONT OF THE LINE
BELOW
MyFile = "c:\TPWQM\" & "RENAME ME CAL-NPS.IN.txt"
'*****SAMPLE
'MyFile = "c:\TPWQM\" & "KRISTENS CALNIPS FILE.IN"
'set and open file for output

MsgBox "Writing RENAME ME CAL-NPS.IN.txt file to C:\TPWQM\"
fnum = FreeFile()
Open MyFile For Output As fnum
'***********
'This section writes file header
Print #fnum, "C LOCKWOODS FOLLY" '************EDIT TEXT IN QUOTES HERE FOR
FIRST LINE OF TITLE
Print #fnum, "C Test Run" '***************EDIT TEXT IN QUOTES HERE FOR RUN
DESCRIPTION
Print #fnum, "C Hydrodynamics and geometry input"
E-53

Print #fnum,
'Start Looping Procedure
'***********KRISTEN - EDIT THE SECOND VALUE IN THE LOOP BELOW TO
INCREASE OR DECREASE LENGTH OF WRITTEN FILE
'***********SUGGESTED VALUE IS ROW NUMBER OF LAST LINE OF DATA IN
COLUMN "O" AS IN OLIVER IN THE SPREADSHEET
For i = 2 To botRow ' ******CHANGE SECTION VALUE HERE TO CHANGE HOW
MANY LINES ARE READ**********
'*************
'This section reads from the spreadsheet
'*****READ AND FORMAT FLOW AND LOAD DATA
Qtemp = Cells(i, 17)
QOut = Format(Qtemp, "@@@@@@@@")
FCBtemp = Cells(i, 18)
FCBOut = Format(FCBtemp, "@@@@@@@@")
'*****READ AND FORMAT DATE AND TIME DATA
StartDate = Cells(i, 15)
'YEAR DATA
yr2 = Format(StartDate, "yy")
If Left(yr2, 1) = "0" Then
yr2 = " " & Right(yr2, 1)
End If
'MONTH DATA
mm2 = Format(StartDate, "mm")
If Left(mm2, 1) = "0" Then
mm2 = " " & Right(mm2, 1)
End If
'DAY DATA
dd2 = Format(StartDate, "dd")
If Left(dd2, 1) = "0" Then
dd2 = " " & Right(dd2, 1)
End If
'TIME DATA
StartTimer = Cells(i, 16)
StartTimerOut = Round(StartTimer, 5)
StartTimerOut = Format(StartTimer, "@@@@@@")

'write project info and then a blank line
Print #fnum, "CH S# DSQ Sal Bc Bd Bg RPOC LPOC DOC"
Print #fnum, "M 0 2 0.00000 0.000 0.000 0.000 0.000 0.000 0.000 0.000"
Print #fnum, "M 0 3 "; QOut; " 0.000 0.000 0.000 0.000 0.000 0.000 0.000"
Print #fnum, "M 0 4 0.00000 0.000 0.000 0.000 0.000 0.000 0.000 0.000"

Print #fnum, "CH S# RPOP LPOP DOP PO4t RPON LPON DON NH4
NO3"
Print #fnum, "M 0 2 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
0.000"
Print #fnum, "M 0 3 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
0.000"
Print #fnum, "M 0 4 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
0.000"
E-54

Print #fnum, "CH S# SU SA COD DO TSS TAM FCB T"
Print #fnum, "M 0 2 0.000 0.000 0.000 0.000 0.00 0.000 0.0 0.000"
Print #fnum, "M 0 3 0.000 0.000 0.000 0.000 0.00 0.000"; FCBOut; taggerOut
Print #fnum, "M 0 4 0.000 0.000 0.000 0.000 0.00 0.000 0.0 0.000"

Print #fnum, tStepOut; " CON : "; yr2 & "/"; mm2 & "/" & dd2 & " " & StartTimerOut
'************* END OF DATE TEXT
Print #fnum,
tStepInc = 1 + tStepInc
tStepOut = Format(tStepInc, "@@@@@@@")

Next i
Print #fnum,
Close #fnum
MsgBox "RENAME ME CAL-NPS.IN.txt file written to C:\TPWQM\"
End Sub
E-55

Appendix D. Model Results of Median and 90th Percentile
The 30-month median and 90th percentile were calculated for the model segment M0S2
of the TPWQM in which the calibration points Site 7A and Site 8 are located. The time
series plot for the TMDL period of the existing condition and load reduction scenario for
the 90th percentile and median are presented in Figures D1 and D2. Given that each
point represents a statistic of the previous 30 months, the first point appears in July of
2006.
0
20
40
60
80
100
120
6/7/2006 12/24/2006 7/12/2007 1/28/2008 8/15/2008 3/3/2009 9/19/2009
Fe
c
a
l

c
o
l
i
f
o
r
m

(
c
o
u
n
t
s
/
1
0
0
m
L
)
Date
90th percentile
90th percentile standard Modeled Current 90th percentile Modeled TMDL 90th percentile

Figure D1. Modeled current and TMDL 90th percentile

E-56

0
5
10
15
20
6/7/2006 12/24/2006 7/12/2007 1/28/2008 8/15/2008 3/3/2009 9/19/2009
Fe
c
a
l

c
o
l
i
f
o
r
m

(
c
o
u
n
t
s
/
1
0
0
m
L
)
Date
Median
Median standard Modeled Current Median Modeled TMDL Median

Figure D2. Modeled current and TMDL median

Lockwoods Folly River Fecal Coliform TMDL
F-1
Appendix F. Public Notice
A public notice was posted to the DWQ TMDL website and notice was sent to a mailing list of interested parties and the WRRI listserv.
Notice was also posted in the City of Wilmington STAR-NEWS newspaper. In addition a press
release was given by NCCF. An article entitled “Pollution report first step in reclaiming Lockwood Folly” was also published in the City of Wilmington StarNews Online newspaper.
Attachments:
1. Affidavit of Publication of the legal notice from the City of Wilmington STAR-NEWS
newspaper.
2. Public announcement document for the draft Total Maximum Daily Loads for the Shellfish Harvesting Areas in the Lockwoods Folly River.
3. Press Release
4. StarNews Online article (“Pollution report first step in reclaiming Lockwood Folly”)

F-2
1617 Mail Service Center, Raleigh, North Carolina 27699-1617 Location: 512 N. Salisbury St. Raleigh, North Carolina 27604 Phone: [phone] \ FAX: [phone] \ Customer Service: 1-877-623-6748 Internet: www.ncwaterquality.org
An Equal Opportunity \ Affirmative Action Employer

DRAFT Total Maximum Daily Loads for the Shellfish Harvesting Areas
in the Lockwoods Folly River, Lumber River Basin, Brunswick County,
North Carolina
July 2010 North Carolina Department of Environment and Natural Resources
Division of Water Quality

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 13, 2010. Comments concerning the report should be directed to Adugna Kebede at [e-mail] or write to:
Adugna Kebede
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 (919)
807-6305 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

North Carolina Department of Environment and Natural Resources Division of Water Quality
Beverly Eaves Perdue Coleen H. Sullins Governor Director Dee Freeman Secretary
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N.C. Coastal Federation Southeast Regional Office | 530 Causeway Dr., Suit F1| Wilmington, NC 28480
Phone: [phone] | Email: [e-mail] | Web: www.nccoast.org

FOR IMMEDIATE RELEASE July 13, 2010 Contact: Mike Giles
Phone: [phone] Email: [e-mail]

Stormwater Polluting Lockwoods Folly River

WILMINGTON – Polluted runoff is closing shellfish beds in the Lockwoods Folly River
in Brunswick County, according to new study done by the N.C. Coastal Federation, the state
and others. The report finds that bacteria entering the river with each rain must be reduced as
much as 84 percent if the river is to once again meet state water standards for shellfishing.
The study addresses the causes of bacterial contamination of the river and the
continued closures of shellfish beds in what was once an important commercial oyster
fishery. More than 55 percent of the river is now closed permanently or temporarily to
shellfishing because of high bacteria levels. That represents a three-fold increase since 1980.
Runoff after rainfalls accounts for most of the bacteria entering the river, the study found
The federation joined Brunswick County, the N.C. Division of Water Quality, the N.C.
Ecosystem Enhancement Program and the N.C. Department of Transportation on the three-
year study of the river. A grant from the U.S. Environmental Protection Agency paid for the
study.
The N.C. Division of Water Quality has posted the study report on its Web site to
allow for public comment and input. To review the study and make comments visit
http://portal.ncdenr.org/web/wq/ps/mtu/tmdl/tmdls or call 919-807-6305. Written comments
will be accepted until Aug. 13. Send comments to Adugna Kebede at
[e-mail] or by mail to him at NCDWQ Planning Section, 1617 Mail
Service Center, Raleigh 27699.
For more than two years volunteers collected water samples, measured stream flow
and water heights both in the lower river and in the swampy streams and creeks of this
88,000-acre watershed. That information was fed into a computer model, which identified the
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Page 2 N.C. Coastal Federation
N.C. Coastal Federation Southeast Regional Office | 131 Racine Dr., Suite 101| Wilmington, NC 28403
Phone: [phone] | Email: [e-mail] | Web: www.nccoast.org

sources of the bacteria and the ways they were entering the river. The model also
established a limit to the amount of bacteria that can enter the river without polluting shellfish
beds.
For further information on the project and how to make comments please contact
Mike Giles at 910-509-2838 or [e-mail]. Information on the project is also
available on the federation Web site at www.nccoast.org. Click on the SE page link and follow
the link to the advocacy page.

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Pollution report first step in reclaiming
Lockwood Folly

By Shelby Sebens
[e-mail]
Published: Wednesday, July 21, 2010 at 5:37 p.m.

Photo by Matt Born
A boater heads past the fishing boats docked in Varnamtown along the Lockwood Folly River on July 21, 2010. The
river is contaminated with excessive levels of fecal coliform bacteria.
Among the marshes and scenic landscape of the Lockwood Folly River, pipes and small
trickles of water carry pollutants that has impaired the Brunswick County waterway to
the point that more than half of the river and tributaries are often closed to shellfishing.
And bringing that water back to state standards will take an 84 percent reduction in the
bacteria entering the river when it rains, according to a recent study of the Brunswick
County watershed.
The three-year study, funded by the Environmental Protection Agency, found that the
source of the pollution is fecal coliform, a waste source from warm-blooded animals.
Public comments on the study are being accepted through Aug. 13 before it goes to the
Environmental Protection Agency for final approval.
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After spending two years collecting data in the hot sun, rain and muddy waters,
volunteers and members of the N.C. Coastal Federationhope this is the first step toward
a cleaner river.
"If we screw this one up, shame on us," Coastal Federation volunteer Rich Peruggi said.
Peruggi started volunteering for the advocacy group four years ago after the federation
advertised a call for citizens' help. Living in Winding River Plantation, Peruggi knows
first hand the beauty of the river and the effects of the pollution.
And he's already taking matters into his own hands. After learning that the parking lot
near a marina in his neighborhood was contributing to runoff pollution in the river, he
spearheaded a rain garden project to head off some of it.
Peruggi joined two other volunteers and Mike Giles, the Cape Fear Coastkeeper with the
N.C. Coastal Federation, on a media tour of the river Wednesday.
"The shellfish are the canaries in the coal mine, so to speak," Peruggi said, pointing to
yellow signs along the way that prohibit shellfishing.
Once fecal coliform levels exceed state standards, it becomes hazardous to human health
to eat the shellfish living there.
Data collected by Peruggi and other volunteers found levels of fecal coliform ranging
from more than 200 colonies per 100 milliliters to an excess of 1,000. The state
standard for shellfish waters is 14 colonies.
The data has been compiled into a mathematical computer model that shows how much
pollution needs to be reduced to restore the river and meet water quality standards.
Some areas had levels so high it was hazardous for people to swim, Giles said.
Once the EPA approves the study, Giles said, the plan is to implement best management
practices to reduce the pollution entering the river.
He said the N.C. Coastal Federation, along with its partners – Brunswick County, N.C.
Division of Water Quality, N.C. Ecosystem Enhancement Program and the N.C.
Department of Transportation – plan to work with developers and individual property
owners on ways to reduce stormwater runoff.
For example, a property owner could stop using fertilizer or clean up after pets, Giles
said.
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He is also hoping that new developers will follow the county's low-impact development
ordinance, and that current developments can retrofit boat ramps, bulkheads and
parking lots to reduce their environmental impact.
Peruggi said the group looks at New Hanover County's creeks as the poster child of what
not to do. The creeks are closed to shellfishing because of high pollution, Giles said.
Shelby Sebens: 343-2076
On Twitter.com: @ShelbySebens
Copyright © 2010 StarNewsOnline.com — All rights reserved. Restricted use only.
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Lockwoods Folly River Fecal Coliform TMDL

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Appendix G: Public Comment
The public comment period extended from July 13, 2010 through August 13, 2010. Comments
were received from North Carolina Coastal Federetion (NCCF) and North Carolina Department
of Transportation. These comments with the NC Division of Water Quality responses are
provided in the Responsiveness Summary presented below.
Lockwood Folly River Fecal Coliform Bacteria TMDL Responsiveness Summary
August 2010
1) One comment stated that the Lockwood’s Folly River TMDL report is an excellent example of a comprehensive collaborative effort involving partnerships with a wide variety of agency
personnel, a diverse group of citizen volunteers to achieve a common goal. The project is
also a result of extensive data and research over a five year period that provided an intensive
review of the water quality issues and impacts on the watershed in order to fully evaluate the
impacts upon the watershed and the requirements for the TMDL. The report represents extensive work both within the watershed and an exhaustive review of information collected
from a variety of sources which has been incorporated into the TMDL report which is very
well written and concise. The comment highlighted the collaborative process and listed the
partners who participated in this project. The commenter appreciated the DWQ and EPA for
their efforts in encouraging the collaborative work to impaired waterbodies in coastal areas.
Response: Thank you for your support and for being part of the collaborative process that
resulted in the development of this TMDL. As stated in your comment, this TMDL is the
result of a joint effort by NC Division of Water Quality, NC Shellfish Sanitation, Brunswick County, the Lockwood Folly Roundtable, the NC Coastal Federation and over 100 volunteers in a variety of capacities. DWQ encourages a collaborative approach and works with local
governments and stakeholders to improve water quality in North Carolina.

2) One comment stated that the Lockwoods Folly TMDL model documentation provides
valuable information related to the bacteria modeling performed for the TMDLs and requested that the model documentation be included in the Appendix to the TMDL report, as
opposed to being maintained as a separate document.

Response: The DWQ agrees that the model report provides valuable information on the Lockwoods Folly TMDL modeling framework. The model documentation is included as Appendix E in the revised TMDL report.

3) One comment stated that on page 9 the TMDL report speculates that improvement in water
quality is attributed to the statewide drought that began in 2007. The commenter suggested
that if data exists to support this claim figures be added to the report illustrating the relationship between the rainfall deficit and the improving trend in water quality. The comment also stated that it is notable in Figure 9 that the model-predicted 90th percentile
fecal coliform value does not drop off beginning in 2008 as the observed values do for Site
7A. Figure 11 also doesn’t suggest a precipitation driven improvement in water quality.
Lockwoods Folly River Fecal Coliform TMDL

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Rather, the figures suggest that factors other than rainfall deficit may be affecting water
quality. It is important to understand these relationships in order to support the effective
implementation plan. Response: In Section 1.4 ‘Water Quality Characterization’ of the TMDL report, the 2007
state wide drought was suggested as one possible factor for the low levels of observed fecal
coliform concentrations in the estuary. The main focus of this discussion is description of the
monitoring data in the estuary. There is no site-specific rainfall data to conduct a detailed analysis of the rainfall-water quality relationship in the area. While low rainfall levels were suggested as a reason for low levels of fecal coliform after 2007, we understand that a
number of factors including rainfall, land use, hydrology, loading from various sources and
pathways, and etc. affect water quality in the estuary. The text is revised to reflect this point
(Section 1.4). The TMDL analysis includes a detailed assessment of the major sources of fecal coliform loading in the watershed which will be targeted in the implementation plan. Figures 9 and 11 show model-predicted 90th percentile fecal coliform values. While these
values are calculated from daily predictions of the model over a thirty-month period, the
observed 90th percentile is calculated from only thirty samples over a thirty month period.
This could be one of the main reasons for the discrepancy between the model-predicted 90th percentile values and the observed 90th percentile values. The model predictions take into account the daily variation in fecal coliform levels whereas the monitored data included
water quality measurements taken every month or every other month.

4) One comment stated that portions of the Intercoastal Waterway and Montgomery Slough are
listed on the cover page and page iv of the TMDL document which strongly implies that the TMDL reductions apply to these waters. Since the TMDL is not developed for these waterbodies the commenter recommends removing references to these waterbodies from the
TMDL document. The commenter supports the inclusion of fecal coliform reducing
recommendation in the implementation plan for the ICWW and Montgomery Slough, but it
needs to be clear that the TMDL does not apply to these waterbodies. Response: The Intercoastal Waterway and the Montgomery Slough are part of the Lockwood
Folly River watershed and these areas will be addressed in the TMDL implementation
strategy. The TMDL document clearly states that a TMDL is not developed for the Intercoastal Waterway and the Montgomery Slough and these areas will be addressed in the TMDL implementation strategy which the commenter fully supports. The text is revised to clearly indicate that the TMDL load reduction will not apply to these two waterbodies (pages
vi, ix, 1, 12, and 30).

5) One comment stated that Section 3.7 of the TMDL report describes the approach used to quantify existing and allowable bacteria loads from NCDOT areas. This section states that “The required load reduction from NCDOT land was calculated to be 53% of their existing
load based on area and its relative contribution to fecal coliform loads compared to other
developed land use types, using EMC as a proxy.” Based on this general description, we
have not been able to duplicate the results presented in the TMDL because insufficient detail is provided. The commenter requested to include a detailed description of the method along with supporting information used in the calculation, such as EMC values and a description of
Lockwoods Folly River Fecal Coliform TMDL

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the land use categories categorized as ‘developed.”

Response: The NCDOT load was calculated using the model as described in Section 3.7 of the TMDL report and Section 4.9 of the model documentation which is attached as Appendix E. In addition, the model documentation presents a detailed description of the EMC value
selection in section 3.2.1 and Table 8. A table summarizing the EMC values used for the
different land use types is included in the TMDL report (See Section 3.2.1, Table 8 of the
revised TMDL document). The text is revised to include more details on the approach used to quantify bacteria loading from DOT areas (Section 3.7). The models used for the TMDL calculations are available to interested parties.

6) One comment stated that Section 3.2.1 of the TMDL report states that the EMC values used
were adjusted during model calibration to account for a “first flush” effect by applying a
multiplying factor early during a storm event and a dividing factor as flows decrease during and after a storm event. Section 3.2.2 of the “Lockwoods Folly River TMDL Model Documentation” draft report, states the multiplying factor to be eighty-two and dividing
factor to be twenty-thousand and one-hundred, depending on flow. The multiplier value is
very important because it sets the maximum or peak concentration simulated during a storm
and thus it defines the existing condition by which the 90th percentiles concentration and required percent reduction in the TMDL are determined. Given the importance of this variable, additional explanation on the selection of these values should be provided in the
text along with a supporting analysis that demonstrates that an adjusted EMC approach, when
compared to the use of a single EMC value, will result in a similar total bacteria load
delivered or exported for a given land use type and storm event. Response: Appendix E Sections 3.2.1 and 3.2.2 of the Lockwoods Folly River TMDL model
documentation present a detailed description of EMC value selection and the watershed
model calibration with particular emphasis on the selection of the multiplying and dividing factors used in the model. These factors are used as calibration parameters and are adjusted based on flow and observed fecal coliform levels in the estuary. Ranges of literature EMC values are given in Table 8 of Appendix E.

7)
A. One comment stated that Figures 9 and 11 in the report present calculated 30-month, 90th percentile values based on water quality observations and model results at Sites 7A and 8, respectively. Based on these figures, the model appears to be simulating a very similar
trend in bacteria concentration at both locations even though water quality measurements
indicate that more localized factors are driving water quality conditions.
Response: It should be noted that both Sites 7A and 8 are located in the same model segment and as such the predicted concentrations are the same for both sites. Given the
complex hydrology and model limitations, care was taken to balance adjustment of model
parameters to represent both sites during calibration. As stated in the TMDL document site 7 and 7A are located in the center of the estuary while Site 8 is located along the shoreline in the southeastern portion of the model segment MOS2 and is less influenced by tidal mixing. For this reason, the water quality measurements at these sites are different.
Lockwoods Folly River Fecal Coliform TMDL

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B. The comment further stated that the model also appears to over-predict during 2006-2009
period and remain high when measurements drop well below the 43 cfu/100 ml threshold
at Site 7A. Model over-prediction is of concern because the water quality measurements at these locations are already biased high due to the nature of Shellfish Sanitation’s
Conditional Sampling Program. Over two-thirds of the bacteria measurements at Site 7A
and 8 are conditional samples. Since conditional samples are more representative of fecal
coliform levels during unfavorable conditions, we would expect them to be higher than
conditions present under routine ambient monitoring. These factors, in combination with a very low bacteria decay rate for saline waters may suggest that the model is either too
conservative or is not capturing the events that lead to lower bacteria concentrations.
Additional figures showing cumulative flows and loads over time (observed and simulated)
and monthly flow volumes and loads (observed and simulated) may be useful in order to
better understand potential uncertainty and biases in the modeling and confirm that the existing calibration is adequately representing conditions present in the waterbody.

Response: As shown in Figure 9, the model generally under-predicts high levels of fecal
coliform and over-predicts low levels of fecal coliform. In Figure 11, while the model predicts high levels of fecal coliform well, it over-predicts low levels of fecal coliform. It should be noted that Figures 9 and 11 show model-predicted 90th percentile fecal coliform
values. While these values are calculated from daily predictions of the model over a thirty-
month period, the observed 90th percentile is calculated from only thirty samples over a
thirty month period. This could be one of the main reasons for the discrepancy between the model-predicted 90th percentile values and the observed 90th percentile values. In most case the variability in fecal coliform levels is very high. The model predictions take into
account the daily variation in fecal coliform levels whereas the monitored data include
fecal coliform data measured every month or every other month. In addition, similar to
other watershed and water quality models, the Lockwoods Folly River TMDL modeling framework has limitations. We acknowledge that there are data limitations, inherent model limitations, and uncertainty associated with these factors. It is expected to have such limitations and uncertainty when dealing with complex systems such as the Lockwoods
Folly River watershed. Conservative assumptions were made in the model to account for
uncertainty and to provide margin of safety. The models were calibrated based on the best available data for the given period and the model results should be interpreted in light of the model limitations. The watershed and water quality model limitations and sources of uncertainty are discussed in Section 3.3 and Section 4.5 of Appendix E, respectively.

The purpose of conditional sampling is to take samples after an area has been temporarily closed in an attempt to show that the river has returned to normal and that it can be reopened to shellfish harvest. As such, Shellfish Sanitation staff may wait a day or two after a rain event before conducting conditional sampling in order to increase the
likelihood of reopening the waters. Therefore these samples are not always more
representative of unfavorable conditions. The text in is revised to reflect this point (Section 1.4).
Lockwoods Folly River Fecal Coliform TMDL

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8) One comment appreciates the cooperative efforts to find fair, reasonable and cost effective
solutions to the bacteria contamination problems within NC’s shellfish harvesting waters.
Response: Thank you for being part of the collaborative process in developing this TMDL. This TMDL is the result of a joint effort by NC Division of Water Quality, NC Shellfish
Sanitation, Brunswick County, the Lockwood Folly Roundtable, the NC Coastal Federation
and over 100 volunteers in a variety of capacities. DWQ encourages a collaborative
approach and works with local governments and stakeholders to improve water quality in
North Carolina.
Lockwoods Folly River Fecal Coliform TMDL
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Appendix H. Public Education and Outreach Materials
1. Brunswick County Lockwood Folly Boat Tour
2. Press Release: The Lockwood Folly River Needs a Few Good People
3. Press Release: Volunteers Needed to Pinpoint Problems on the Lockwood Folly
4. Lockwood Folly River Study Fact Sheet
5. Press Release: Study Aims to Find Solutions
6. Press Release: Development Planners Keep Environment in Mind
7. Press Release: Coastal Federation, Brunswick County, NCDOT to Examine Low Impact
Development for Road Projects
8. Press Release: Runoff a Likely Culprit for Lockwood Folly Bacterial Woes
9. Press Release: Community Wetland Planting and Clean Water Event
10. Press Release: Water Quality Projects to Restore the Lockwood Folly River Installed at the Brunswick County Government Center
11. Tabloid: Lockwood Folly River Water Quality Strategy

Brunswick County Lockwood Folly Boat Tour
Wednesday, March 14, 2007

Agenda
8:30 am Board bus at Wilmington Hilton (Facing the river, bus will be
parked on the right side of the hotel)
8:45 am Bus Departs Hotel
9:45 am Bus Arrives at Holden Beach Marina, just before the bridge to
Holden Beach on the left. (exit road to the right of bridge, park
under bridge and meet at the front of marina at docks.)
9:45 am Welcome and Tour Introduction
10:15 am Board Boat
10:30 am Boat departs for River Cruise
Presentations and guided tour
Noon lunch break/ free discussion on the boat
12:30 pm Presentations and guided tour continues
2:00 pm Boat docks at Holden Beach Marina
2:15 pm Bus departs Marina
3:00 pm Bus arrives at Wilmington Hilton

This is an enclosed boat (with an open air top deck) but we suggest you bring foul
weather gear and appropriate clothing for inclement and/or cold/cool weather.
Please do not forget your camera! Space is limited and requires advanced
registration.
Questions? Call Lauren Kolodij [phone] or Mike Giles [phone].

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North Carolina Coastal Federation | 131 Racine Drive Suite 101 | Wilmington, NC 28403
Phone: [phone] | Fax: [phone] | Email: [e-mail] | Web: http://www.nccoast.org
PPrreessss RReelleeaassee
FOR IMMEDIATE RELEASE
September 20, 2007

Contact: Mike Giles, Cape Fear COASTKEEPER®
Phone: [phone]: 910-231-6687 (cell)
Email: [e-mail]

The Lockwood Folly River Needs a Few Good People

Wilmington, NC- In 2005 the N. C. Coastal Federation joined Brunswick County, the
Environmental Protection Agency and the State Ecosystem Enhancement Program in a multi-
year project to identify sources of pollution on the Lockwood Folly River. This study will assist
the agencies in development of an overall watershed management plan for the river. The plan is
intended as a model to properly guide growth and development to halt the current trend of
increasingly polluted and impaired water. Since 1980 the percent of the river closed to shell
fishing has more that tripled from 15% to over 55% and all indications are that downward trend
will continue, unless citizens work together to stem the negative effects of increasing storm
water and pollution sources along the river.

But the partners cannot do it alone. They are recruiting volunteers who will collect water
samples and other information at over 11 locations for over a year beginning this November.
The water sample information will be used for the development of strategies to reduce the
sources of pollution and identify the maximum pollution load the river can sustain without
degrading the water quality.

In 2005 the N. C. Division of Water Quality, the N.C. Department of Transportation, the N.C.
Ecosystem Enhancement program, and Brunswick County joined the Federation to study the
Lockwood Folly River watershed from the intra coastal waterway to the headwaters of the River.
Grants from the U.S. Environmental Protection Agency have paid for the study with guidance
from the State Division of Water Quality. Residents only have to look north to New Hanover
County, where all but one of the tidal creeks are permanently closed to shellfishing, to see what
unchecked growth can do to water quality. In 2005 the county established, with the Coastal
Federation and other partners, the Lockwood Folly Roundtable, an eight member group who,
over the course of the past two years, developed a set of 10 proposed strategies to help cure
the problems on the ailing river. These strategies are meant not to hinder growth and
development but to compliment growth and protection of the resources as an overall goal.
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Storm water runoff is the number one source of pollution in our coastal rivers, streams, creeks
and wetlands and the effects of that pollution continues to grow. The surging development
within the 150-square-mile watershed has had a severe effect on the health of the river. “The
main goal of the water sampling project, called a TMDL study, is to find out what is causing the
pollution in the river,” explained Mike Giles, the federation’s Cape Fear COASTKEEPER® and
the project leader. “We want to identify the sources of the bacteria coming down the river, and
then develop a model, developed by Stantec consulting, to control and eventually reduce the
bacterial pollution by implementing the roundtable land use strategies”.

While Stantec and its computer specialists will do the analytical work, volunteers will assist in
the field work by sampling the river at selected sites and under selected conditions to providing
the baseline data for the model development. The samples, taken after heavy rain events, will
be tested for bacteria by a certified Laboratory in Wilmington.

“We are looking for folks in Varnamtown, Sunset Harbor and communities like Winding River,
who are willing to get their hands and feet wet and want to make a difference in the future of the
river” Giles said. “These community minded people will be helping not only a river but a way of
life and culture that is fast disappearing along our coast”.

Boats aren’t required since most of the samples can be taken from land or a dock. The
volunteers will be trained in early November and sampling will begin later that month. Anyone
interested in volunteering should call Mike Giles @ [phone] or email him
@[e-mail].

There will be other opportunities for people to get involved as fisherman, landowners, business
people and others who call the river home will be invited to join a small stakeholders’ group that
will offer advice and guidance to the volunteer team. Interested persons are invited to the
first meeting on Monday, October 22, 2007 at the Varnamtown Hall at 6:30 PM. The public
is invited to attend the meeting to learn more about the project. Other opportunities will
include: a public presentation to the Brunswick County Board of Commissioners on
Monday November 5, 2007. Giles said he invites any interested party or person to come to one
of the meetings and follow the progress of the sampling project and the Lockwood Folly
strategies.

Reporters/Media note: Boat tours of the project area and interviews of the project team
and volunteer samplers can be arranged after November 1 by calling Mike Giles at
[phone]

###

About the North Carolina Coastal Federation:
“Citizens Working Together for a Healthy Coast”

The North Carolina Coastal Federation (NCCF) is the state's largest nonprofit organization
Working to restore and protect the coast. NCCF headquarters are located at 3609 Highway 24 in Ocean
between Morehead City and Swansboro and are open Monday through Friday from 8:30 am to 5 pm.
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The NCCF also operates field offices in Wilmington and Manteo. For more information call 252-393-8185
or check out NCCF's website at www.nccoast.org
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North Carolina Coastal Federation | 131 Racine Drive Suite 101 | Wilmington, NC 28403
Phone: [phone] | Fax: [phone] | Email: [e-mail] | Web: http://www.nccoast.org
PPrreessss RReelleeaassee
FOR IMMEDIATE RELEASE
September 25, 2007

Contact: Mike Giles, Cape Fear COASTKEEPER®
Phone: [phone]: 910-231-6687 (cell) Email: [e-mail]

Volunteers needed to pinpoint problems on the
Lockwood Folly

Wilmington, N.C.-The North Carolina Coastal Federation is looking for a few good men and women.

The Federation needs help to tackle pollution problems on the Lockwood Folly River and is calling for
willing and able volunteers. The effort is part of an ongoing partnership that includes Brunswick
County and state and federal agencies and seeks to identify and fix the sources of pollution entering
and degrading the river’s water quality. The partnership formed in 2005 to work on these issues, and
this new work represents a follow-up on the successful Lockwood Folly Roundtable project.

Storm water runoff is the number one source of pollution in our coastal rivers, streams, creeks and
wetlands and the effects of that pollution continue to grow with the area’s surging development.

“The main goal of the water sampling project is to find out what’s causing the pollution in the river,”
explained Mike Giles, the Federation’s Cape Fear COASTKEEPER® and the project leader. “We
want to identify the sources of the bacteria coming down the river, and then develop ways to control
and eventually reduce the bacterial pollution”.

The volunteers will collect water samples and other information at locations on the Lockwood Folly
River, beginning in November. The water sample information will be used find ways to reduce the
sources of pollution and to identify the maximum amount of pollution the river can handle without
degrading the water quality.

“We are looking for folks in Varnamtown, Sunset Harbor and communities like Winding River who are
willing to get their hands and feet wet and want to make a difference in the future of the river,” Giles
said. “These community-minded people will be helping not only a river but a way of life and culture
that is fast disappearing along our coast”.

Results from the initial project and those generated by the volunteers samples will be used to guide
growth and development and to prioritize retrofit opportunities to fix existing pollution problems.

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Boats aren’t required since most of the samples can be taken from land or a dock. The volunteers will
be trained in early November and sampling will begin later that month. Prospective volunteers are
invited to attend a kickoff public meeting on Monday, October 22 at the Varnamtown Town Hall at
6:30 p.m. Those interested in volunteering should call Mike Giles @ [phone] or email him
at [e-mail].
###

The North Carolina Coastal Federation:
“Citizens Working Together for a Healthy Coast”

The North Carolina Coastal Federation (NCCF) is the state’s only non-profit organization focused exclusively on protecting
and restoring the coast of North Carolina through education, advocacy and habitat restoration and preservation. For more
information call 252-393-8185 or check out NCCF's website at www.nccoast.org

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Lockwood Folly River Study
Fact Sheet

The Partners
The N.C. Coastal Federation,
Brunswick County, the N.C.
Division of Water Quality, NC
Ecosystem Enhancement Program,
and the N.C. Department of
Transportation

More than 55% of the waters in the Lockwood Folly River are closed either permanently
or temporarily to shellfishing because of bacterial pollution. Stormwater runoff, wildlife
and failing septic tanks are thought to be the sources of the bacteria. Under the federal
Clean Water Act, these waters are considered “impaired” because they can’t meet their
intended use for harvesting clams and oysters. North Carolina is obligated under the law
to clean up these waters.

The Study
Using money from the U.S. Environmental Protection Agency, the partners will study the
river from the Intracoastal water way up through the estuaries and tributaries. Volunteers
will collect more than 300 water samples from 11 locations in the river. The samples will
be tested for bacteria and the results used in computer models that will determine the
likely sources of pollution. The study, which will end in 2010, will devise plans for the
watershed to control the bacteria, suggest remedies and management strategies.

How You Can Help
v Consider volunteering to take water samples. No boat is required, and volunteers
will be trained.
v Attend public meetings about the project. They will be help periodically while the
study is ongoing, usually at Varmumtown Hall or the Brunswick County Fishing
Club in Sunset Harbor. The dates will be publicized well in advance.
To learn more or to volunteer, call Mike Giles at [phone] or email
him at [e-mail].
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3-20-08 Star News Article
Lockwood Folly River

Study aims to find solutions
By Shannan Bowen,
Staff Writer
Published: Saturday, March 22, 2008 at 6:01 a.m.

Mike Giles, N.C. Coastal Federation , collects water samples from the Lockwood Folly River
Thursday, March 20, 2008. The N.C. Coastal Federation and its volunteers are collecting the
samples to determine sources of pollution in the river. Staff Photo By Mike Spencer/STAR-
NEWS
Sunset Harbor | Thursday morning, just after a light rain, was prime
time to collect samples of polluted water in the Lockwood Folly River.
Mike Giles, Cape Fear Coastkeeper for the N.C. Coastal Federation,
and a group of volunteers set out about twice a month on the river to
collect samples that are tested to ferret out the sources of the
pollution.
So far, tests have found high levels of fecal coliform bacteria, which
can come from sewage, animal feces and fertilizer.
The sampling should be completed in October. A consultant will then
gather the test results and use a computerized model to show likely
sources of the pollution.
The sources can include stormwater runoff from developments along
the river, wildlife and failing septic tanks, said Tracy Skrabal, a coastal
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restoration specialist for the N.C. Coastal Federation, who helped Giles
collect samples Thursday.
More than 55 percent of the Lockwood Folly River is closed either
permanently or temporarily to shellfishing because of bacterial
pollution.
The river once was a popular spot for oyster harvesting.
This has prompted years of studies and roundtable meetings by
Brunswick County officials and environmental agencies who hope to
find ways to reduce the river's pollution and restore its shellfishing
areas.
Giles' study, which began in fall of last year and is expected to be
completed in 2009, will suggest remedies and strategies for controlling
the bacteria.
One strategy, called low-impact development, is the topic of discussion
for a committee of county officials, builders and environmentalists.
The committee, which will meet sometime in the next few weeks, will
review a resolution and manual that gives builders alternatives to
conventional curb-and-gutter stormwater runoff techniques.
A low-impact development design captures stormwater runoff, treats it
and uses it in the landscape.
Rain gardens, for example, include plants that soak up the runoff
water and its nutrients.
Giles said the biggest issue with stormwater is the way developers and
county officials allow it to reach bodies of water like the Lockwood
Folly River.
"If we don't do something, we're going to lose our shellfish waters," he
said.
"It's going to take a lot of willpower and working together."
A volunteer's job
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Volunteers for the N.C. Coastal Federation's study have met since
October. They collect samples mostly after a rainy night, but the lack
of rain this year has made that challenging.
Phyllis Evans is one volunteer who collects water samples from a creek
that flows into the Lockwood Folly River.
To collect the samples, she first lowers a bucket into the river. After
pouring the water into two plastic test bottles, she places them into a
cooler and then measures the water's temperature and salinity.
Other details, such as the time of the day, weather and noticeable
conditions in the river are recorded.
Evans lives in River Run Plantation, one of the developments touching
the river, and volunteered because she wanted to be part of a project
that will change the river.
"I want this river cleaned up," she said.
Shannan Bowen: 755-6307
[e-mail]
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Lockwood Folly River News

Development planners keep environment
in mind

By Shannan Bowen
Staff Writer
Published: Wednesday, October 1, 2008 at 6:52 p.m.
Last Modified: Wednesday, October 1, 2008 at 7:01 p.m.
Supply | Even before the county’s new guidelines are in place, a residential development
planned near Holden Beach is being designed with the environment in mind.

Staff Photo | Paul Stephen
Senior planner Stephen Carpenter (from left) and Heather Burkert, president of H.
Burkert & Co. landscape architecture firm, talk with landowner Michael Hobbs about
waterfront homes that will be built along the banks of an old mine site lake at the
Lakeside at Holden Beach development site Wednesday Oct.1, 2008. The development is
the first in Brunswick County to abide by new low-impact development rules.
Lakeside at Holden Beach will be built on 100 acres once used as a sand and marl mine,
and the developers say a 16-acre lake on the property and Lockwood Folly River
tributaries will be protected from runoff pollution by using low-impact development
techniques.
The stormwater controls, such as rain gardens instead of traditional curbs and gutters, are
at the heart of a push to encourage building that’s more environmentally friendly. .
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The Lockwood Folly River has been the focus of more than a year’s worth of studies and
roundtables where representatives from county departments, the state’s Division of Water
Quality and the N.C. Coastal Federation gathered to discuss ways to retrofit development
and restore the river’s health through low-impact development and other guidelines that
will be outlined in a county resolution.
The city of Wilmington recently passed a similar resolution, and New Hanover County
will consider one Monday night.
Brunswick County officials are tweaking a draft of the resolution, and Assistant County
Commissioner Steve Stone said it might be on the county commissioners’ Oct. 20
agenda.
Officials say the Lockwood Folly River is polluted because of the way developers have
allowed stormwater to flow into the river after collecting chemicals and waste from the
land.
A low-impact development stormwater design would capture runoff, treat it and use it in
the landscape. Rain gardens, for example, include native plants that soak up the runoff
water and use it for nutrients.
Members of the committee that studied the river and discussed the low-impact
development resolution hope the proposed resolution’s guidelines, though voluntary, will
encourage developers to think of new ways to maintain stormwater runoff.
Heather Burkert, the landscape architect for Lakeside at Holden Beach, said low-impact
development designs will be incorporated by using covenants and deed restrictions to
require each house to use elements such as cisterns, or devices that capture rain and feed
the lot’s irrigation system.
Each of the planned 221 homesites in the community will have rain gardens to collect
stormwater runoff and cisterns to collect roof water.
In addition, most streets will allow stormwater runoff to flow into vegetative swales that
will transport stormwater to infiltration areas to remove pollutants.
“We became cognizant by studying what the land was already doing and trying to respect
that and work with the land instead of trying to control it,” Burkert said.
The master plan for Lakeside has been approved by the county, and the community’s
developer, Stone Chimney Development LLC, plans to break ground on the site
sometime next year.
Burkert said she believed the developer would be the first to turn in a stormwater permit
application using low-impact development techniques outlined in the county’s proposed
resolution.
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“We have been interested in this a long time, and now they’re allowing us to do it,” she
said.
Shannan Bowen: 264-8345
[e-mail]
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3609 Highway 24 (Ocean) Newport NC 28570
North Carolina Coastal Federation | 3609 Hwy 24 (Ocean) | Newport, NC 28570
Phone: [phone] | Fax: [phone] | Email: [e-mail] | Web: http://www.nccoast.org
PPrreessss RReelleeaassee
November 25, 2008
NCCF contact: Lauren Kolodij
Phone: [phone] Cell: 910-262-5178
E-mail: [e-mail]
N.C. DOT contact: Lisa Craley
Phone: [phone]

Coastal Federation, Brunswick County, N.C. DOT to examine
low impact development for road projects

Wilmington, N.C.—Thanks to the N.C. Clean Water Management Trust Fund
(CWMTF), a non-profit, a local government and a state agency will be able to
collaborate on ways to incorporate low impact development (LID) practices into state
highway and development construction by reducing stormwater flows. And reducing
polluted stormwater will help clean up local waters.

The North Carolina Coastal Federation (NCCF) has received a $75,650 grant from the
CWMTF to initiate a cooperative LID planning process with Brunswick County and the
N.C. Department of Transportation’s Highway Stormwater Program (NCDOT). The
project will identify cost-effective options for the use of LID design practices into
highway infrastructure projects that may help protect and restore the water quality in the
Lockwood Folly River watershed. It will also provide LID tools to developers working in
the area as part of a holistic approach to tackling water quality problems.

Stormwater is rain water that falls upon hardened, or impervious, surfaces, picking up
pollutants on the ground and flushing them into our creeks, rivers and sounds. LID
practices seek to use planning, design features and other techniques to capture and
treat polluted stormwater and protect water quality.

In the project, NCDOT, LID experts and engineers from the Maryland and Florida DOTs
will examine LID practices as cost-saving measures in real-world highway and road
projects. The discussion will provide information for NCDOT engineers as they move
forward with planning other road projects.

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Dave Henderson, NCDOT’s State Hydraulics Engineer, said, “The project comes at an
opportune time for our interagency planning process. The information we develop will
have long-term implications for future DOT practices.”

The project expands upon previous work and the momentum generated by ongoing
efforts to protect and restore valuable shellfishing and recreational waters of the
Lockwood Folly River. NCCF and the county brought together major stakeholders in a
group called the Lockwood Folly Roundtable. In 2007, this group recommended a
blueprint of nine actions to protect and restore water quality in the Lockwood Folly
River. Brunswick County commissioners subsequently accepted the blueprint, and this
project represents another step in implementing three of the recommendations: (1)
promoting better coordination of the dozens of federal, state and local government
programs and agencies involved in environmental management; (2) promoting
widespread use of LID practices in new land developments and (3) encouraging
projects that reduce existing levels of stormwater pollution by facilitating the
identification, design, construction and maintenance of retrofit projects.

NCDOT owns and operates the county’s largest stormwater drainage system, and the
agency wants to see how LID might be used to improve the county’s water quality
issues in a cost-effective way.
The CWMTF was established 1996 to help finance projects that enhance or restore
degraded waters, protect unpolluted waters, and/or contribute toward a network of
riparian buffers and greenways for environmental, educational and recreational benefits.
###
The North Carolina Coastal Federation is the state’s only non-profit organization focused exclusively on
protecting and restoring the coast of North Carolina through education, advocacy and habitat restoration and
preservation. Its headquarters and central regional office are located at 3609 Highway 24 in Ocean between
Morehead City and Swansboro. The Federation also has a northeast regional office in Manteo and a southeast
regional office in Wilmington. For more information call 252-393-8185 or check out NCCF's website at
www.nccoast.org

H-16

Runoff a likely culprit for Lockwood
Folly bacterial woes

Staff photo | Shannan Bowen
Consultant Jason Doll (left) and Mike Giles of the N.C. Coastal Federation discuss a
project that attempts to pin-point sources of pollution in the Lockwood Folly River.

By Shannan Bowen
Staff Writer
Published: Sunday, April 12, 2009 at 5:50 p.m.
Last Modified: Sunday, April 12, 2009 at 5:50 p.m.
Sunset Harbor | Rainfall and stormwater runoff are most likely to blame for the
Lockwood Folly River’s troubled waters.
A preliminary analysis of water samples, taken from the Brunswick County river over the
course of a year, showed the highest levels of bacteria and other pollutants flowed to the
river with stormwater runoff from paved surfaces and other areas, said Mike Giles, the
Cape Fear Coastkeeper with the N.C. Coastal Federation.
Many landscapes, developed or not, allow rain to run off into the river, carrying bacteria
from animal waste, chemicals from vehicles and fertilizers from yards, for example, into
the water.
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More than half of the river is already closed to shellfishing because of bacterial pollution
long suspected from stormwater runoff, failed septic tanks and other causes.
This prompted years of study by county officials and environmental agencies in search of
ways to reduce the river’s pollution and restore its shellfishing areas.
Collecting samples from the river was the first step in a project funded by the U.S.
Environmental Protection Agency to attempt to pinpoint pollution sources in the river.
More than a dozen volunteers helped Giles collect water samples over the past year,
which were then sent to a lab and tested for fecal coliform and other bacteria.
Jason Doll, a consultant for Stantec Consulting in Raleigh, will take the sample results
and create a mathematical computer model showing how much pollution needs to be
reduced to restore the river and meet water quality standards.
Giles said test results averaged 350 to more than 1,000 fecal coliform colonies per 100
milliliters of water. The state’s water quality standards for safe consumption of shellfish
is just 14 colonies per 100 milliliters of water, he said.
Doll said it wasn’t surprising that the highest contamination levels were found after
rainfall, but where they found those high levels was interesting.
Doll said he thought water samples showing the highest levels of fecal coliform bacteria
would be taken from areas in the river near developed land.
“But people have developed near the estuary, where there is more saltwater,” he said,
adding that saltwater kills some of that harmful bacteria.
Doll said most of the higher levels of pollution were found in tributaries, where there was
less salinity and flushing of the river.
But many people are starting to purchase and develop land along the river’s tributaries
since most of the land along the estuary has already been purchased and developed, Giles
said.
“It will just increase the problem if we don’t develop it correctly,” he said. “More and
more people want to be on the river.”
Doll, Giles and the team of volunteers gathered at an oyster roast April 3 to celebrate the
completion of the sampling project.
Doll said he hoped to have the computer model completed by late summer.
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A list of strategies to keep the river clean, including low-impact development techniques
and retrofitting drainage systems, will then be created and presented to county officials
for implementation.
Shannan Bowen: 343-2016
[e-mail]

All rights reserved. This copyrighted material may not be re-published without
permission. Links are encouraged.

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North Carolina Coastal Federation | 3609 Hwy 24 (Ocean) | Newport, NC 28570
Phone: [phone] | Fax: [phone] | Email: [e-mail] | Web: http://www.nccoast.org

PPrreessss RReelleeaassee
FOR IMMEDIATE RELEASE

June 2, 2009

Contact: Tracy Skrabal
Phone: [phone]x201
Email: [e-mail]

Community Wetland Planting and Clean Water Event
Scheduled in Bolivia, June 9

Wilmington, N.C. – The partnership of the North Carolina Coastal Federation,
Brunswick County, the N.C. Cooperative Extension Service and the Brunswick Soil and Water
Conservation District invite all area residents and visitors to a community wetland planting and
clean water educational event. The event will take place at the Brunswick County Government
Complex Cooperative Extension Offices (Building N) in Bolivia on Tuesday, June 9, from 10:00
a.m. to 12:30 p.m.

Participants will learn about the health of their local creeks and simple things they can do in their
back yards to protect area water quality. Information on back yard rain gardens and rain barrels
and other steps people can take to reduce stormwater runoff and nuisance flooding will be
available. Visitors can visit a backyard rain-garden and a stormwater treatment wetland.

For those who want to get their hands dirty, there will be a volunteer wetland planting on-site at
the Government Complex. Once complete, this created wetland will capture and treat polluted
rainwater before it has a chance to become polluted runoff. It is the first of many stormwater
retrofits that N.C. Coastal Federation, Brunswick County and Stantec Engineering will be
constructing within the Lockwood Folly watershed as part of a water quality demonstration
project. This project is an important component of the Lockwood Folly Watershed Strategy and
builds upon the work of many volunteer hours spent monitoring the river.

Volunteer planters are welcome and needed, and the public is invited to attend the clean water
event, and/or help to plant the wetland. Those interested in planting should contact Tracy
Skrabal at the N.C. Coastal Federation at 910-790-3275 for more information and to sign up to
plant.
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###

The N.C. Coastal Federation is the state’s only non-profit organization focused exclusively on protecting
and restoring the coast of North Carolina through education, advocacy and habitat restoration and preservation. Its
headquarters and central regional office are at 3609 N.C. 24 in Ocean between Morehead City and Swansboro. The
federation also has a Northeast Regional Office in Manteo and a Southeast Regional Office in Wilmington. For
more information or to join call 252-393-8185 or visit the federation’s website at www.nccoast.org
H-21

North Carolina Coastal Federation | 3609 Hwy 24 (Ocean) | Newport, NC 28570
Phone: [phone] | Fax: [phone] | Email: [e-mail] | Web: http://www.nccoast.org

PPrreessss RReelleeaassee
FOR IMMEDIATE RELEASE
September 18, 2009
Contact: Ted Wilgis
Phone: [phone] x 202
Email: [e-mail]

Water Quality Projects to Restore the Lockwood Folly River Installed at the
Brunswick County Government Center—Tour Available Sept. 24

Bolivia, N.C. – The partnership of the North Carolina Coastal Federation (NCCF), Brunswick County, the
N.C. Cooperative Extension Service, Brunswick Soil and Water Conservation District, with engineering support
from Stantec Consulting, has completed the installation of a rain garden and stormwater wetland at the Brunswick
County Government Center in Bolivia. NCCF will give a tour of the stormwater wetland and rain garden to the
public and media on Thursday, September 24 at 12:30 pm.

NCCF and the project partners are installing a series of measures at the government complex to capture
and treat polluted stormwater from the site before it enters local creeks and the Lockwood Folly. Earlier this
summer, volunteers and staff from project partners spent two days installing over 1,500 wetland plants in the
wetland and rain garden.

The stormwater project not only improves water quality in the Lockwood Folly River but also educates
and encourages others to implement low-impact development (LID) measures in the watershed. LID's goal is to
use a natural landscape to absorb and treat stormwater close to its source before it can degrade water quality in
local creeks and rivers.

Stormwater runoff, the primary source of surface water pollution, is water from rain or irrigation that flows
over land and into local creeks, streams and waterways. Runoff carries pollutants such as pet waste, auto fluids,
fertilizers, pesticides and litter through the drainage system and directly into our waterways.

The N.C. Attorney General’s Environmental Enhancement Grant Program funded the project. This
project site was identified as an ideal candidate for a water quality demonstration and education project during a
two-year watershed planning and monitoring project for the Lockwood Folly watershed and is part of the
Lockwood Folly Watershed Strategy. The project is also a component of the Cape Fear Arch Conservation
Collaboration, which consists of a diverse group of organizations, including NCCF, interested in conserving
natural resources and enhancing water quality in Brunswick, Columbus, New Hanover, Sampson, Pender and
Bladen Counties in North Carolina and Horry and Georgetown Counties, South Carolina.

The tour will start at the Brunswick County Government Complex Cooperative Extension Offices (Building
N) in Bolivia. Those interested in the tour should contact Ted Wilgis at the N.C. Coastal Federation at 910-790-
3275 or [e-mail] for more information.
###
The N.C. Coastal Federation is the state’s only non-profit organization focused exclusively on protecting and restoring the coast of
North Carolina through education, advocacy and habitat restoration and preservation. Its headquarters and central regional office are at 3609
N.C. 24 in Ocean between Morehead City and Swansboro. The federation also has a Northeast Regional Office in Manteo and a Southeast
Regional Office in Wilmington. For more information or to join call 252-393-8185 or visit the federation’s website at www.nccoast.org.
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