3 pgs 1-99

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
Peletier, North Carolina
July 2022
DirtMreams, LLC
ATM
"44ftim-1,40
A Geosyntec Company
2201 NW 40 TERRACE,
GAINESVILLE, FLORIDA 32605
386-256-1477

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
Table of Contents
1.0
Introduction
1-1
1.1 Study Area and Project Description
1-1
1.2 Objectives
1-6
1.3 Report Outline
1-6
2.0
Field Data Measurements
2-1
2.1 Overview
2-1
2.2 Discrete Sampling
2-2
2.2.1 In -Situ YSI Data
2-2
2.2.2 Laboratory Data
2-18
2.3 Continuous Data
2-18
2.3.1 Water Levels
2-19
2.3.2 Salinity and Temperature
2-22
2.3.3 pH
2-22
2.3.4 Dissolved Oxygen
2-24
2.3.5 Rain
2-25
3.0
Hydrodynamic Model Development and Flushing Assessment
3-1
3.1 Model Description
3-1
3.2 Hydrodynamic and Flushing Model
3-2
3.3 Model Boundary Conditions
3-6
3.4 Model Calibration
3-8
3.5 Flushing Simulations
3-8
3.5.1 Initial Marina Basin Design Flushing Results
3-9
3.5.2 Revised Marina Basin Design Flushing Results
3-12
4.0
Water Quality Model Development and Dissolved Oxygen Assessment
4-1
4.1 Model Description
4-1
4.2 Model Boundary Conditions
4-2
4.3 Model Calibration
4-3
4.4 Dissolved Oxygen Simulations
4-7
5.0
Summary and Conclusions
5-1
6.0
Literature Cited
6-1
Appendix A -- Environmental Monitoring and Hydrodynamic and Water Quality Simulation Plan
Appendix B -- Analytical Results
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ATM

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
List of Tables
Table 2-1. Water Quality Constituents Measured at Discrete Stations: Discrete 01, 02, 03 and 04...... 2-13
Table2-2. Analytical Results...................................................................................................................2-20
Table 2-3. Basic Statistics of Water Quality Constituents and Water Level at Continuous 01 and
Continuous02..........................................................................................................................................2-25
W i R/213667. D 2 D/7/8/2022
ATM
—N%k--
A Geosyntec Company

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
List of Figures
Figure 1-1. Amphitheater Road Marina on White Oak River near Peletier, Carteret County, North
Carolina on U.S. Geological Survey National Map . .................................................................................... 1-1
Figure 1-2. Amphitheater Road Marina on White Oak River near Peletier, Carteret County, North
Carolina (A) on U.S. Geological Survey National Map with Contours of Equal Elevation (brown polylines)
on a 5-foot Contour Interval, and (B) on an April 28, 2020, Aerial Photograph by Maxar with Discrete
(blue diamonds) and Continuous (yellow circles) Constituent Measurement Locations. Stations Discrete-
02 and Continuous-02 are Coincident.......................................................................................................1-2
Figure 1-3. Initial Marina Layout...............................................................................................................1-4
Figure 1-4. Revised Marina Layout............................................................................................................1-5
Figure 2-1. Dissolved Oxygen (mg/L) measurements during a low tide condition A) at the top, B) in the
middle and C) at the bottom of water. DLT-01 in blue circles, DLT-02 in red rectangles, DLT-03 in green
asterisks and DLT-04 in black squares denotes the measurements at Discrete 01, 02, 03 and 04,
respectively during a low tide condition....................................................................................................2-3
Figure 2-2. Salinity (psu) measurements during a low tide condition A) at the top, B) in the middle and C)
at the bottom of water. DLT-01 in blue circles, DLT-02 in red rectangles, DLT-03 in green asterisks and
DLT-04 in black squares denotes the measurements at Discrete 01, 02, 03 and 04, respectively during a
lowtide condition...................................................................................................................................... 2-4
Figure 2-3. Specific Conductivity (µS/cm) measurements during a low tide condition A) at the top, B) in
the middle and C) at the bottom of water. DLT-01 in blue circles, DLT-02 in red rectangles, DLT-03 in
green asterisks and DLT-04 in black squares denotes the measurements at Discrete 01, 02, 03 and 04,
respectively during a low tide condition....................................................................................................2-5
Figure 2-4. PH measurements during a low tide condition A) at the top, B) in the middle and C) at the
bottom of water. DLT-01 in blue circles, DLT-02 in red rectangles, DLT-03 in green asterisks and DLT-04 in
black squares denotes the measurements at Discrete 01, 02, 03 and 04, respectively during a low tide
condition.................................................................................................................................................... 2-6
Figure 2-5. Temperature (°C) measurements during a low tide condition A) at the top, B) in the middle
and C) at the bottom of water. DLT-01 in blue circles, DLT-02 in red rectangles, DLT-03 in green asterisks
and DLT-04 in black squares denotes the measurements at Discrete 01, 02, 03 and 04, respectively
duringa low tide condition........................................................................................................................ 2-7
Figure 2-6. Dissolved Oxygen (mg/L) measurements during a high tide condition A) at the top, B) in the
middle and C) at the bottom of water. DHT-01 in blue circles, DHT-02 in red rectangles, DHT-03 in green
asterisks and DHT-04 in black squares denotes the measurements at Discrete 01, 02, 03 and 04,
respectively during a high tide condition . ................................................................................................. 2-8
Figure 2-7. Salinity (psu) measurements during a high tide condition A) at the top, B) in the middle and
C) at the bottom of water. DHT-01 in blue circles, DHT-02 in red rectangles, DHT-03 in green asterisks
and DHT-04 in black squares denotes the measurements at Discrete 01, 02, 03 and 04, respectively
duringa high tide condition.......................................................................................................................2-9
Figure 2-8. Specific Conductivity (µS/cm) measurements during a high tide condition A) at the top, B) in
the middle and C) at the bottom of water. DHT-01 in blue circles, DHT-02 in red rectangles, DHT-03 in
green asterisks and DHT-04 in black squares denotes the measurements at Discrete 01, 02, 03 and 04,
respectively during a high tide condition . ............................................................................................... 2-10
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ATM

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
Figure 2-9. PH measurements during a high tide condition A) at the top, B) in the middle and C) at the
bottom of water. DHT-01 in blue circles, DHT-02 in red rectangles, DHT-03 in green asterisks and DHT-04
in black squares denotes the measurements at Discrete 01, 02, 03 and 04, respectively during a high tide
condition. ................................................................................................................................................. 2-11
Figure 2-10. Temperature (°C) measurements during a high tide condition A) at the top, B) in the middle
and C) at the bottom of water. DHT-01 in blue circles, DHT-02 in red rectangles, DHT-03 in green
asterisks and DHT-04 in black squares denotes the measurements at Discrete 01, 02, 03 and 04,
respectively during a high tide condition................................................................................................ 2-12
Figure 2-11. Water Surface Elevation (m) above NAVD88 at Continuous 01 in green solid line and
Continuous 02 in red solid line................................................................................................................ 2-19
Figure 2-12. A) Salinity (psu) and B) Temperature (°C) measurements at Continuous 01 in green solid line
and Continuous 02 in red solid line . ........................................................................................................ 2-23
Figure 2-13. pH measurements at Continuous 01 in green solid line and Continuous 02 in red solid line.2-
23
Figure 2-14. Dissolved oxygen (mg/L) at Continuous 01 in green solid line and Continuous 02 in red solid
line............................................................................................................................................................ 2-24
Figure 2-15. Rain (inch/day) Data Onsite.................................................................................................2-25
Figure 3-1. Model Grid and the Proposed Marina (in red rectangle)........................................................3-3
Figure 3-2. Model Grid in the Proposed Final Marina Basin Design..........................................................3-4
Figure 3-3. Overall Model Bathymetry......................................................................................................3-5
Figure 3-4. Model Bathymetry within the Proposed Final Marina Basin Design.......................................3-6
Figure 3-5. Tidal Forcing Utilized on Southern Grid Boundary . ................................................................. 3-7
Figure 3-6. Measured Winds at Beaufort, Duke Marine Lab, NC (August 1, 2021 to September 15, 2021)
................................................................................................................................................................... 3-7
Figure 3-7. Comparison of Simulated and Measured Water Levels at Continuous 01..............................3-8
Figure 3-8. Initial Dye Concentration and Basin Layout for Initial Marina Basin Design ........................3-10
Figure 3-9. Percent Mass Dye Remaining in Initial Marina Basin Design Over Time (spring scenario) ..3-11
Figure 3-10. Percent Mass Dye Remaining in Initial Marina Basin Design Over Time (neap scenario) ... 3-11
Figure 3-11. Initial Dye Concentration and Basin Layout for Revised Marina Basin Design...................3-12
Figure 3-12. Percent Mass Dye Remaining in Revised Marina Basin Design Over Time (Spring Scenario) 3-
13
Figure 3-13. Percent Mass Dye Remaining in Revised Marina Basin Design Over Time (neap scenario)... 3-
13
Figure 4-1. Observed and simulated 15-minute dissolved oxygen at Continuous 01 outside the mouth of
the tributary in White Oak River for 15 August — 13 September 2021..................................................... 4-4
Figure 4-2. Observed and simulated 15-minute dissolved oxygen at Continuous 02 inside the mouth of
the tributary for 15 August — 13 September 2021.....................................................................................4-4
Figure 4-3. Observed and simulated average daily dissolved oxygen at Continuous 01 outside the mouth
of the tributary in White Oak River for 15 August — 13 September 2021.................................................4-5
Figure 4-4. Observed and simulated average daily dissolved oxygen at Continuous 02 inside the mouth
of the tributary for 15 August — 13 September 2021................................................................................4-6
Figure 4-5. Grid Locations in the Model for Output of Dissolved Oxygen Simulation Results.................4-8
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ATM
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Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
Figure 4-6. a) Comparison of Pre- versus Post -Project Simulated Dissolved Oxygen for all Vertical Levels
b) Comparison of Pre- versus Post -Project Simulated Vertically Averaged Dissolved Oxygen (outside of
Creekmouth).............................................................................................................................................4-9
Figure 4-7. a) Comparison of Pre- versus Post -Project Simulated Dissolved Oxygen for all Vertical Levels.
b) Comparison of Pre- versus Post -Project Simulated Vertically Averaged Dissolved Oxygen (in Creek
mouth).....................................................................................................................................................4-10
Figure 4-8. a) Comparison of Pre- versus Post -Project Simulated Dissolved Oxygen for all Vertical Levels
b) Comparison of Pre- versus Post -Project Simulated Vertically Averaged Dissolved Oxygen (In Creek at
SouthEntrance to Basin)..........................................................................................................................4-11
Figure 4-9. a) Comparison of Pre- versus Post -Project Simulated Dissolved Oxygen for all Vertical Levels.
b) Comparison of Pre- versus Post -Project Simulated Vertically Averaged Dissolved Oxygen (In Creek at
NorthEntrance to Basin)..........................................................................................................................4-12
Figure 4-10. a) Comparison of Pre- versus Post -Project Simulated Dissolved Oxygen for all Vertical
Levels. b) Comparison of Pre- versus Post -Project Simulated Vertically Averaged Dissolved Oxygen (In
Creek above Marina Entrances)...............................................................................................................4-13
Figure 4-11. a) Comparison of Pre- versus Post -Project Simulated Dissolved Oxygen for all Vertical
Levels. b) Comparison of Pre- versus Post -Project Simulated Vertically Averaged Dissolved Oxygen (In
Creekin Upstream Fork)..........................................................................................................................4-14
Figure 4-12. a) Post -Project Simulated Dissolved Oxygen for all Vertical Levels. b) Post -Project
Simulated Vertically Averaged Dissolved Oxygen (In Marina Basin — Southern End).............................4-15
Figure 4-13. a) Post -Project Simulated Dissolved Oxygen for all Vertical Levels. b) Post -Project
Simulated Vertically Averaged Dissolved Oxygen (In Marina Basin — Northern End).............................4-16
Figure 4-14. Comparison of Simulated Pre- versus Post -Project Daily Averaged Dissolved Oxygen
Concentrations for Multiple Locations.................................................................................................... 4-17
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ATM
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Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
1.0 Introduction
1.1 Study Area and Project Description
Dirt2Dreams, LLC, hired Applied Technology & Management, Inc. (ATM, a Geosyntec
Company) to develop a hydrodynamic and water quality model to evaluate the flushing and
dissolved oxygen conditions within the proposed Amphitheater Road Marina on a small tidal
creek off the White Oak River near Peletier, in Carteret County, North Carolina (Figure 1-1 and
Figure 1-2). Land Management Group, Inc. (LMG) assisted ATM with this work by collecting
hydrodynamic and water quality data to support the model development and establish baseline
water quality conditions.
Dirt2Dreams proposes to construct a marina in an unnamed tributary to the White Oak River, on
the western side of the river. Dirt2Dreams may also construct marina infrastructure in the White
Oak River, between the unnamed tributary and a point about 300 meters (m) southeast of the
unnamed tributary.
77° 15'W 771101W 77-� W
10 Kilometers
C 7 4 8 Miles
Figure 1-1. Amphitheater Road Marina on White Oak River near Peletier, Carteret County, North
Carolina on U.S. Geological Survey National Map.
a e ..t: , i o 0 0 7. D2 D/7/8/2022
ATM
1-1

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
7'6'50"W 77'6'40"W 77'6'30"W 77'6'20"W 77'6'10"W 7706'W 77'5'50"W
7'6'50"W 77'6'40"W 77"6'30"W 77'6'20"W 77'6'10"W 77'6'W 77'5'50"W
C 500 1.000 Meters
0 1,000 2,000 Feet
Figure 1-2. Amphitheater Road Marina on White Oak River near Peletier, Carteret County, North
Carolina (A) on U.S. Geological Survey National Map with Contours of Equal Elevation (brown
polylines) on a 5-foot Contour Interval, and (B) on an April 28, 2020, Aerial Photograph by Maxar
with Discrete (blue diamonds) and Continuous (yellow circles) Constituent Measurement
Locations. Stations Discrete-02 and Continuous-02 are Coincident.
W i R/213667. D 2 D/7/8/2022
ATM
AGeusyntec Company 1-2

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
To evaluate the flushing and dissolved oxygen conditions, ATM used the Environmental Fluid
Dynamics Code (EFDC) model, which is supported by the U.S. Environmental Protection
Agency (EPA). EFDC simulates water and water quality constituent transport in dynamically
complex water bodies such as rivers, estuaries, lakes, and coastal regions. The hydrodynamic
model estimates the degree of exchange between the proposed marina basin and the adjacent
waters. The water quality model for dissolved oxygen concentration is internally coupled with
the hydrodynamic model, which simulates circulation and physical transport processes.
Prior to initiation of the hydrodynamic and water quality monitoring and development of the
hydrodynamic and water quality models, ATM submitted an Environmental Monitoring and
Hydrodynamic & Water Quality Simulation Plan to the State of North Carolina, Department of
Environmental Quality (DEQ). The objective of the plan was to describe environmental
monitoring and the planned hydrodynamic and water quality simulations to be conducted in
support of the marina permit application. The proposed environmental monitoring included
water level monitoring, water quality constituent monitoring, and atmospheric monitoring.
ATM proposed to use the environmental measurements to establish baseline hydrodynamic and
water quality conditions and to support development of a hydrodynamic and water quality model
in the unnamed tributary to the White Oak River near Hancock Point and in the White Oak
River. The plan identified that the hydrodynamic and water quality simulations will be used to
accomplish the following:
1. Refine the marina design,
2. Ensure that constituents in the proposed marina will be flushed to the White Oak River, and
3. Ensure that the proposed marina will not significantly decrease existing (baseline)
dissolved oxygen concentrations in the unnamed tributary or in the river.
The plan was submitted for review and approval by DEQ staff and is included as Appendix A.
For the flushing analysis, two marina layouts were evaluated (Figure 1-3 and Figure 1-4). The
initial marina layout had a single middle entrance. The second layout had two entrances. The
development of the second layout was based on the flushing determinations made on the initial
marina. These layouts are discussed in more detail later in the report.
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Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
206 300.
.-eet
b
Lw-
- Original Basin Layout
Figure 1-3. Initial Marina Layout
W-FR/213667.D2D/7/8/2022
ATM
AGeosymec Company

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
0 _ 200 300
eet
,R
t-
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A
Updated Basin Layout
Figure 1-4. Revised Marina Layout
W i R/213667. D 2 D/7/8/2022
ATM
-N%k--
A Geosyntec Company

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
1.2 Objectives
To support permitting of the proposed marina, ATM and LMG completed the following tasks.
1. Measure hydrodynamic and water quality data at two continuous stations and four
discrete stations (Figure 1-2). The data included continuous water level and water quality
constituents (pH, dissolved oxygen, temperature, and salinity), as well as discrete in -situ
and grab samples for analysis for nutrients, dissolved oxygen, and other parameters.
Data were collected from August 9, 2021, through September 13, 2021, to coincide with
the critical period for dissolved oxygen levels. The data established baseline
hydrodynamic and dissolved oxygen conditions outside the tidal creek mouth and inside
the creek, in the area of the proposed marina basin.
2. Analyze and present baseline data to define baseline conditions.
3. Collect desktop data to support model setup, including published tide data, bathymetric
conditions, and available local meteorologic data.
4. Generate the EFDC model grid and its bathymetry with National Oceanic and
Atmospheric Administration (NOAA) Navionics and develop a hydrodynamic and water
quality model using the measured data and obtained desktop data.
5. Utilize the model to assess the degree of flushing under post -project conditions within
the marina basin and define alternatives to the marina layout where flushing is not
sufficient.
6. Simulate the pre -project versus post -project dissolved oxygen conditions in the tidal
creek and within the marina basin and evaluate the differences to assess potential for
environmentally significant degradation from baseline (pre -project) conditions.
7. Prepare a technical report that summarized the results of the study.
1.3 Report Outline
This report is presented in four sections following this introduction. Section 2.0 presents the
field data measurements. Section 3.0 presents the development of the hydrodynamic model
and the flushing simulations performed, along with the findings from the analyses. Section 4.0
describes the water quality model development and dissolved oxygen assessment under pre -
and post -project conditions. Section 5.0 summarizes the findings from the study.
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_M
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Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
2.0 Field Data Measurements
2.1 Overview
LMG conducted field studies near the project area as described in Section 1 and as outlined in
detail within the plan in Appendix A. Data collection consisted of both discrete and continuous
data. For the discrete sampling, four stations were identified, as shown in Figure 1-2. These
stations were sampled at weekly intervals from August 9 through September 14, 2021. For
each sampling event, in -situ profiles were collected at the four locations over depth, per DEQ
requirements. Parameters included dissolved oxygen, salinity, temperature, pH, and specific
conductance. Profiles were collected at slack high and low tides. Water quality grab samples
were collected at low and high slack tides and analyzed for the following parameters.
• Total nitrogen concentration
• Ammonia concentration
• Nitrate -nitrite concentration
• Total Kjeldhal nitrogen concentration
• Total phosphorus concentration
• Orthophosphate concentration
• Chlorophyll a concentration
• 5-day biochemical oxygen demand
• Carbon concentration
• Total suspended solids concentration
• Color
Continuous data were collected at two locations shown in Figure 1-2. The continuous
parameters included water level, salinity, temperature, pH, and dissolved oxygen. The
continuous instruments were mounted to represent near -bottom conditions. Continuous data
were collected from August 9 through September 14, 2021. The following presents the data
collected.
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ATM
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Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
2.2 Discrete Sampling
The North Carolina DEQ requires surface and bottom measurements in water depths less than
3 feet, and surface, mid -column and bottom measurements in water depths greater than 3 feet.
LMG measured vertical profiles of dissolved oxygen concentration, temperature, pH and
conductivity from the bed to the water surface during six 1-day trips. The dates of the trips were
August 9, August 16, August 23, August 31, September 9 and September 13, 2021. The water
quality data were measured at slack high and low tides. For the graphs the discrete stations are
identified as DLT or DHT followed by the station number depending on whether the readings
were taken at low tide (LT) or high tide (HT).
2.2.1 In -Situ YSI Data
Figure 2-1 through Figure 2-10 present graphs of the discrete profile data. The measurements
taken at low tide are presented in Figure 2-1 through Figure 2-5. The measurements taken
during high tide are presented in Figure 2-6 through Figure 2-10. Table 2-1 presents the data
collected.
Dissolved oxygen concentrations (Figure 2-1) during the low tide measurements varied from a
low of near 3.0 milligrams per liter (mg/L) to up to 10.0 mg/L for the six sampling events. The
lowest measurements were found during the August 23 and 31 events in the near -bottom
readings at station Discrete 03. This is most upstream station in the creek. The highest reading
(around 10 mg/L) was found at the same station during the August 9 event. Data presented in
later sections will show this coincided with a very high Chlorophyll a (Chl a) reading, indicating
potential supersaturated dissolved oxygen levels due to algal productivity. The data show that
within the creek (and in one reading at 04), some measured concentrations were below the 4.0
mg/L instantaneous criteria. These were more prevalent in the bottom readings, but some were
found in the surface. Salinity (Figure 2-2) and specific conductivity (Figure 2-3) during low tide
conditions increased from near zero up to around 30 parts per thousand (ppt) through the
measurement period. This is due to high White Oak River discharge from August 3 to August 9.
No halocline was seen, that is, salinity was not vertically stratified, as the water was well mixed.
Low tide pH ranged from 7 to 8, which is close to neutral (Figure 2-4). Through the
measurement period, pH increased. Low tide temperature range was from 25 to 35 degree
Celsius (°C), with a general decreasing trend through the period of the measurements (Figure
2-5). No thermocline was noticed in the six measurement events.
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ATM
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Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
Dissolved oxygen concentrations during high tide were consistently higher than that measured
at low tide, reflecting conditions out in the White Oak River, which were higher than in the creek.
The high tide measurements were also more consistent among the different stations other than
Discrete 03. Dissolved oxygen at the bottom (Figure 2-6) was about 2 mg/L lower at Discrete
03 than at the other stations, except for August 16. Salinity and specific conductivity (Figure 2-7
and Figure 2-8) during the high tide conditions were a little greater than during the low tide
conditions, reflecting the higher saline water from the White Oak River. The other water quality
constituents during the high tide were similar with those during the low tide (Figure 2-10).
Dissolved Oxygen (mg/L) : Low Tide
10
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m
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08/09 08/16 08/23 08/31 09/07 09/13
Days of 2021
Figure 2-1. Dissolved Oxygen (mg/L) measurements during a low tide condition A) at the top, B) in
the middle and C) at the bottom of water. DLT-01 in blue circles, DLT-02 in red rectangles, DLT-03
in green asterisks and DLT-04 in black squares denotes the measurements at Discrete 01, 02, 03
and 04, respectively during a low tide condition.
WiR/213667. D2D/7/8/2022
AT_M
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Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
30
25 A)
H 20 El
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10 0
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08/09 08/16 08/23 08/31 09107 09/13
Days of 2021
Figure 2-2. Salinity (psu) measurements during a low tide condition A) at the top, B) in the middle
and C) at the bottom of water. DLT-01 in blue circles, DLT-02 in red rectangles, DLT-03 in green
asterisks and DLT-04 in black squares denotes the measurements at Discrete 01, 02, 03 and 04,
respectively during a low tide condition.
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ATM
2-4

0-
3
2
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Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
X 104 Specific Conductivity (uSlcm) : Low Tide
A) a
0
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8 0 DLT-01 o DLT-02 DLT-03 Ei DLT-04
X 104
B)
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El
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08/09 08/16 08/23 08/31 09107 09/13
Days of 2021
Figure 2-3. Specific Conductivity (pS/cm) measurements during a low tide condition A) at the top,
B) in the middle and C) at the bottom of water. DLT-01 in blue circles, DLT-02 in red rectangles,
DLT-03 in green asterisks and DLT-04 in black squares denotes the measurements at Discrete 01,
02, 03 and 04, respectively during a low tide condition.
W i R/213667. D 2 D/7/8/2022
ATM
-N%k--
A Geusyntec Company 2-5

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
PH: Low Tide
9
A)
o8
7
a DLT-01 o DLT-02 DLT-03 Ei DLT-04
6
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08/09 08/16 08/23 08/31 09107 09/13
Days of 2021
Figure 2-4. PH measurements during a low tide condition A) at the top, B) in the middle and C) at
the bottom of water. DLT-01 in blue circles, DLT-02 in red rectangles, DLT-03 in green asterisks
and DLT-04 in black squares denotes the measurements at Discrete 01, 02, 03 and 04, respectively
during a low tide condition.
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ATM
2-6

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
0
Temperature ( C) : Low Tide
35 A}
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08/09 08/16 08/23 08/31 09107 09/13
Days of 2021
Figure 2-5. Temperature (°C) measurements during a low tide condition A) at the top, B) in the
middle and C) at the bottom of water. DLT-01 in blue circles, DLT-02 in red rectangles, DLT-03 in
green asterisks and DLT-04 in black squares denotes the measurements at Discrete 01, 02, 03 and
04, respectively during a low tide condition.
WiR/213667. D2 D/7/8/2022
ATM
2-7

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
Dissolved Oxygen (mg/L) : High Tide
10 A)
o 8
N n
6 °
4
o DHT-01 o DHT-02 DHT-03 DHT-04
2
10 B)
(D
8
o
a) 6 El
"J A
� 4 v �
2
10 C)
E
0 8
0
m °
° o
a) 6 o o ® o
® o
4
o �
2
08/09 08/16 08/23 08/31 09107 09/13
Days of 2021
Figure 2-6. Dissolved Oxygen (mg/L) measurements during a high tide condition A) at the top, B)
in the middle and C) at the bottom of water. DHT-01 in blue circles, DHT-02 in red rectangles, DHT-
03 in green asterisks and DHT-04 in black squares denotes the measurements at Discrete 01, 02,
03 and 04, respectively during a high tide condition.
WiR/213667. D2 D/7/8/2022
ATM
2-s

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
Salinity (psu) : High Tide
30
25 A) A
0 20 ° o
15
10 g
5 o DHT-01 DHT-02 DHT-03 ° DHT-04
0
30
25 B) o g
o O
20 0
15
m �
c
10
5
0
30
25 C) o N
° 20 0
0 0El
on 15
0 0
10 LI
5
0
08/09 08/16 08/23 08/31 09107 09/13
Days of 2021
Figure 2-7. Salinity (psu) measurements during a high tide condition A) at the top, B) in the middle
and C) at the bottom of water. DHT-01 in blue circles, DHT-02 in red rectangles, DHT-03 in green
asterisks and DHT-04 in black squares denotes the measurements at Discrete 01, 02, 03 and 04,
respectively during a high tide condition.
WiR/213667. D2 D/7/8/2022
ATM
2-9

�0 3
2
.2 3
5
� 2
0
3
m
2
Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
X 104 Specific Conductivity (uS/cm) : High Tide
A)
� o
A
0
0
Q
0
A 0 DHT-01 DHT-02 DHT-03 Ei DHT-04
x 104
B)
o
0
0
0
0
0
0
x 104
C)
0
0
o
El
0
0
08/09 08/16 08/23 08/31 09107 09/13
Days of 2021
Figure 2-8. Specific Conductivity (pS/cm) measurements during a high tide condition A) at the top,
B) in the middle and C) at the bottom of water. DHT-01 in blue circles, DHT-02 in red rectangles,
DHT-03 in green asterisks and DHT-04 in black squares denotes the measurements at Discrete 01,
02, 03 and 04, respectively during a high tide condition.
WiR/213667. D2 D/7/8/2022
ATM
2-10

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
PH: High Tide
9
A}
08
7
o DHT-01 DHT-02 DHT-03 Ei DHT-04
6
9
B}
a)
�8 An
o
am
c
7
6
9
C)
08 R o El
00 �
N
7
c�
6
08/09 08/16 08/23 08/31 09107 09/13
Days of 2021
Figure 2-9. PH measurements during a high tide condition A) at the top, B) in the middle and C) at
the bottom of water. DHT-01 in blue circles, DHT-02 in red rectangles, DHT-03 in green asterisks
and DHT-04 in black squares denotes the measurements at Discrete 01, 02, 03 and 04, respectively
during a high tide condition.
WiR/213667. D2 D/7/8/2022
ATM
2-11

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
0
Temperature ( C) : High Tide
35 A) o
o
0
�-o 30 ❑ Z�
c_ ❑
o
25
o DHT-01 DHT-02 DHT-03 ❑ DHT-04
20
35 B) Q a
m o ❑
-a o
30
El
N ° O
25
20
35 C)
❑ 0
o � o
0 30
25
c�
20
08/09 08/16 08/23 08/31 09107 09/13
Days of 2021
Figure 2-10. Temperature (°C) measurements during a high tide condition A) at the top, B) in the
middle and C) at the bottom of water. DHT-01 in blue circles, DHT-02 in red rectangles, DHT-03 in
green asterisks and DHT-04 in black squares denotes the measurements at Discrete 01, 02, 03 and
04, respectively during a high tide condition.
WiR/213667. D2 D/7/8/2022
ATM
2-12

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
Table-. . 04
DLT and DHT Denotes the Sampling Event which Was Collected during Low Tide and
High .- Condition, Respectively.
Meas. Salinity Spc. Cond DO Temp.
Station Depth (in) Time (psu) (PS/cm) (mg/L) pH (IC)
4 08/09/202114:22
2.02
3850.0
6.70 7.24
1 30.90
DLT-1
16
08/09/202114:21
3.13
5756.0
6.07
7.02
29.30
4
08/09/202115:01
3.79
6858.0
7.42
7.17
31.30
DLT-2
16
08/09/202115:00
6.17
10740.0
5.38
7.02
30.20
4
08/09/202114:45
2.47
4624.0
10.29
7.83
34.10
DLT-3
16
08/09/202114:44
4.34
7769.0
6.54
6.99
31.20
4
08/09/202113:59
4.88
8663.0
6.63
7.18
31.00
DLT-4
12
08/09/202113:58
4.89
8668.0
3.67
7.14
30.90
4
08/09/202109:21
6.35
11020.0
5.61
7.07
27.70
DHT-1
18
08/09/202109:20
6.99
12047.0
5.60
7.10
27.30
4
08/09/202110:21
3.96
7135.0
5.69
6.98
28.60
DHT-2
12
08/09/202110:20
5.27
9295.0
5.54
7.00
28.40
18
08/09/202110:19
5.84
10204.0
5.42
7.00
28.10
4
08/09/202109:56
2.54
4750.0
6.15
7.11
28.50
DHT-3
18
08/09/202109:55
4.45
7946.0
4.62
6.89
27.90
4
08/09/202108:52
4.39
7848.0
5.74
6.98
27.50
DHT-4
18
08/09/202108:51
5.42
9538.0
5.50
6.98
27.40
4
08/16/202108:59
9.88
16954.0
4.76
7.62
31.10
DLT-1
20
08/16/202108:58
10.10
17303.0
4.75
7.61
31.10
36
08/16/202108:57
10.20
17464.0
5.45
7.65
31.10
4
08/16/202109:36
7.44
13045.0
5.27
7.67
30.60
DLT-2
10
08/16/202109:35
14.01
23348.0
4.08
7.51
31.00
20
08/16/202109:34
16.47
27068.0
4.81
7.48
31.00
4
08/16/202109:20
10.13
17350.0
3.93
7.56
31.40
DLT-3
10
08/16/202109:19
14.89
24700.0
3.68
7.47
31.50
20
08/16/202109:18
16.36
26900.0
4.27
7.45
31.30
4
08/16/202108:39
12.70
21340.0
5.64
7.68
30.70
DLT-4
10
08/16/202108:38
12.81
21503.0
5.96
7.69
30.60
4
08/16/202114:45
12.19
20590.0
5.13
7.82
32.20
24
08/16/202114:44
12.15
20525.0
5.26
7.82
32.20
DHT-1
36
08/16/202114:44
12.15
20524.0
5.43
7.82
32.20
48
08/16/202114:43
12.14
20512.0
5.36
7.82
32.20
56
08/16/202114:42
12.17
20559.0
5.67
7.82
32.20
4
1 08/16/202115:14
8.70
15149.0
6.48
8.00
34.50
DHT-2
15
1 08/16/202115:14
11.76
19958.0
4.84
7.79
33.80
W i R/213667. D 2 D/7/8/2022
ATM
-N%k--
A Geosyntec Company 2-1 3

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
Table-. . 04
DLT and DHT Denotes the Sampling Event which Was Collected during Low Tide and
High .- Condition, Respectively.
Meas. Salinity Spc. Cond DO Temp.
Station Depth (in) Time (psu) (PS/cm) (mg/L) pH (IC)
28 08/16/202115:13
16.98
27845.0
3.13
7.57
31.60
4
08/16/202115:01
8.95
15562.0
6.24
8.11
35.30
DHT-3 15
08/16/2021 15:01
9.31
16141.0
6.43
8.03
35.10
28
08/16/202115:00
12.91
21736.0
4.97
7.81
33.30
4
08/16/202114:31
10.00
17193.0
6.09
7.94
33.40
DHT-4 12
08/16/202114:31
10.03
17240.0
6.26
7.93
33.40
20
08/16/202114:30
10.02
17222.0
6.23
7.92
33.40
4
08/23/202107:26
12.82
21476.0
5.13
7.69
28.80
12
08/23/202107:25
12.89
21576.0
5.21
7.70
28.80
DLT-1
24
08/23/202107:24
12.96
21684.0
5.38
7.73
28.80
36
08/23/202107:23
13.86
23077.0
5.53
7.78
29.10
44
08/23/202107:22
16.53
27103.0
5.85
7.76
29.60
4
08/23/202108:00
15.90
26138.0
5.09
7.73
28.70
12
08/23/202107:59
16.03
26331.0
5.08
7.70
28.80
DLT-2
24
08/23/202107:59
17.63
28710.0
4.76
7.65
28.70
34
08/23/202107:58
19.13
30933.0
5.26
7.67
29.00
4
08/23/202107:46
17.48
28522.0
3.69
7.49
29.40
12
08/23/202107:45
17.85
29063.0
3.68
7.55
29.30
DLT-3
24
08/23/202107:44
19.12
30941.0
3.62
7.60
29.70
34
08/23/202107:44
23.10
36738.0
3.12
7.54
30.40
4
08/23/202107:07
14.86
24587.0
5.14
7.72
29.00
DLT-4
12
08/23/202107:06
14.84
24553.0
5.37
7.74
28.90
22
08/23/202107:05
16.17
26549.0
5.61
7.71
28.90
4
08/23/202112:16
16.11
26543.0
5.27
7.94
31.60
12
08/23/202112:15
17.19
28098.0
5.38
7.97
30.00
24
08/23/202112:15
19.24
31123.0
5.25
8.06
29.70
DHT-1
36
08/23/202112:14
23.14
36776.0
4.66
8.08
29.70
48
08/23/202112:13
23.69
37560.0
4.76
8.07
29.50
60
08/23/202112:13
24.21
38287.0
4.79
8.07
29.40
64
08/23/202112:12
24.61
38861.0
4.88
8.06
29.40
4
08/23/202112:50
17.58
28716.0
4.69
7.91
31.20
12
08/23/202112:48
18.07
29414.0
4.79
7.97
30.30
DHT-2
24
08/23/202112:48
19.65
31729.0
4.85
8.05
29.90
36
08/23/202112:47
23.16
36798.0
4.98
8.06
29.60
48
1 08/23/202112:46
23.77
37669.0
5.02
8.02
29.50
W i R/213667. D 2 D/7/8/2022
ATM
-N%k--
A Geosyntec Company 2-14

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
Table-. . 04
DLT and DHT Denotes the Sampling Event which Was Collected during Low Tide and
High .- Condition, Respectively.
Meas. Salinity Spc. Cond DO Temp.
Station Depth (in) Time (psu) (PS/cm) (mg/L) pH (IC)
52 08/23/202112:46
23.86
37793.0
4.95 8.00
1 29.50
4
08/23/202112:35
16.87
27694.0
5.05
7.78
32.20
12
08/23/202112:34
17.01
27888.0
4.79
7.74
31.60
DHT-3 24
08/23/202112:33
17.45
28500.0
4.66
7.70
30.40
36
08/23/202112:33
18.79
30474.0
3.97
7.75
30.00
44
08/23/202112:32
22.85
36379.0
3.03
7.71
30.40
4
08/23/202111:58
20.62
33159.0
5.05
7.98
30.20
12
08/23/202111:57
21.81
34856.0
5.08
7.97
29.60
DHT-4
24
08/23/202111:56
22.49
35829.0
5.26
7.97
29.50
36
08/23/202111:56
25.52
40147.0
5.52
7.92
29.40
4
08/31 /2021 08:36
16.34
26827.0
4.84
7.81
29.70
12
08/31 /2021 08:35
19.62
31695.0
4.38
7.81
30.10
DLT-1
24
08/31/202108:34
21.24
34061.0
4.30
7.78
30.30
36
08/31 /2021 08:33
21.39
34271.0
4.34
7.75
30.30
44
08/31 /2021 08:33
21.63
34611.0
4.53
7.73
30.00
4
08/31 /2021 09:16
18.88
30593.0
3.71
7.67
29.70
12
08/31 /2021 09:14
18.94
30677.0
3.60
7.70
29.70
DLT-2
34
08/31/202109:13
21.27
34082.0
3.43
7.80
29.90
36
08/31 /2021 09:11
24.94
39355.0
3.04
7.76
30.10
40
08/31 /2021 09:11
25.41
40027.0
2.84
7.72
30.10
4
08/31 /2021 08:57
17.97
29235.0
3.74
7.58
29.40
12
08/31/202108:57
18.18
29557.0
3.55
7.63
29.40
DLT-3
24
08/31 /2021 08:55
20.99
33693.0
3.75
7.74
30.20
34
08/31 /2021 08:55
24.53
38780.0
3.35
7.68
30.30
4
08/31 /2021 08:16
20.77
33348.0
4.11
7.64
29.40
DLT-4
14
08/31/202108:15
21.47
34368.0
4.09
7.55
29.50
28
08/31 /2021 08:14
22.41
35732.0
4.19
7.36
29.70
4
08/31 /2021 14:33
21.60
34601.0
5.56
8.05
31.00
12
08/31 /2021 14:32
21.59
34594.0
5.61
8.04
31.00
24
08/31/202114:31
21.71
34764.0
5.63
8.04
31.00
DHT-1
36
08/31 /2021 14:30
21.84
34957.0
5.49
8.02
31.00
48
08/31 /2021 14:30
21.91
35049.0
5.62
8.01
31.00
58
08/31 /2021 14:29
21.90
35031.0
5.65
8.00
31.00
4
1 08/31/202115:11
1 18.18
1 29673.0
5.82
8.12
33.20
DHT-2
12
1 08/31 /2021 15:10
1 18.40
1 30012.0
5.71
8.11
33.40
W i R/213667. D 2 D/7/8/2022
ATM
-N%k--
A Geosyntec Company 2-1 5

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
Table-. . 04
DLT and DHT Denotes the Sampling Event which Was Collected during Low Tide and
High .- Condition, Respectively.
Meas. Salinity Spc. Cond DO Temp.
Station Depth (in) Time (psu) (PS/cm) (mg/L) pH (IC)
24 08/31 /2021 15:09
18.44
30074.0
5.66 8.11
1 33.40
34
08/31 /2021 15:08
19.80
32054.0
4.94
8.04
33.00
4
08/31 /2021 14:55
18.58
30272.0
5.33
8.01
33.40
12
08/31 /2021 14:53
18.58
30279.0
5.22
8.01
33.50
24
08/31/202114:52
18.63
30353.0
4.86
7.98
33.40
DHT-3
36
08/31 /2021 14:50
18.63
30356.0
5.32
7.94
33.40
48
08/31 /2021 14:50
18.97
30838.0
4.72
7.82
32.90
52
08/31 /2021 14:48
22.66
36154.0
2.71
7.61
31.50
4
08/31 /2021 14:15
17.93
29253.0
5.84
7.93
31.80
DHT-4
12
08/31/202114:14
17.81
29076.0
5.71
7.90
31.80
22
08/31 /2021 14:14
17.64
28833.0
5.69
7.85
31.80
4
09/07/202114:09
26.29
41206.0
5.89
8.17
28.60
12
09/07/202114:08
26.60
41638.0
5.76
8.16
28.50
24
09/07/202114:07
26.76
41857.0
5.68
8.16
28.50
DLT-1
36
09/07/202114:07
26.93
42101.0
5.72
8.15
28.40
48
09/07/202114:06
27.14
42390.0
5.70
8.14
28.40
58
09/07/202114:05
27.50
42898.0
5.84
8.12
28.30
4
09/07/202114:44
24.81
39172.0
5.19
8.04
30.20
12
09/07/202114:43
24.91
39323.0
5.07
8.05
30.20
DLT-2
24
09/07/202114:41
25.71
40408.0
5.27
8.12
29.20
34
09/07/202114:39
27.71
43194.0
5.60
8.16
28.30
4
09/07/202114:28
24.38
38607.0
4.32
7.96
31.10
12
09/07/202114:27
24.46
38706.0
4.29
7.99
30.90
DLT-3
24
09/07/202114:26
25.84
40570.0
4.49
8.07
28.40
36
09/07/202114:25
27.81
43314.0
4.44
8.09
28.10
46
09/07/202114:24
29.05
45054.0
3.63
8.02
28.20
4
09/07/202113:51
27.01
42248.0
6.09
8.16
29.40
12
09/07/202113:50
27.01
42256.0
6.09
8.16
29.40
DLT-4
24
09/07/202113:50
27.05
42302.0
5.87
8.15
29.30
30
09/07/202113:49
27.90
43460.0
6.00
8.14
28.50
4
09/07/202108:50
26.31
41186.0
5.21
8.07
27.40
12
09/07/202108:49
26.30
41178.0
5.26
8.07
27.40
DHT-1
24
09/07/202108:48
26.30
41180.0
5.31
8.06
27.40
36
09/07/202108:47
26.30
41179.0
5.27
8.05
27.40
48
09/07/202108:46
26.30
41170.0
1 5.31
8.05
27.40
W i R/213667. D 2 D/7/8/2022
ATM
-N%k--
A Geosyntec Company 2-1 6

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
Table-. . 04
DLT and DHT Denotes the Sampling Event which Was Collected during Low Tide and
High .- Condition, Respectively.
Meas. Salinity Spc. Cond DO Temp.
Station Depth (in) Time (psu) (PS/cm) (mg/L) pH (IC)
52 09/07/202108:45
26.24
41093.0
5.48 8.02
27.30
4
09/07/202109:25
24.28
38315.0
4.37
7.96
27.40
12
09/07/202109:23
24.38
38457.0
4.37
8.01
27.40
DHT-2
24
09/07/202109:22
25.27
39732.0
5.03
8.06
27.50
34
09/07/202109:21
25.87
40580.0
5.23
8.05
27.50
4
09/07/202109:10
24.04
37974.0
3.62
7.87
27.30
12
09/07/202109:09
24.20
38195.0
4.22
7.97
27.20
DHT-3 24
09/07/202109:08
26.12
40925.0
3.83
8.02
27.60
36
09/07/202109:07
29.50
45666.0
3.65
8.01
28.10
46
09/07/202109:07
29.67
45896.0
3.46
7.99
28.10
4
09/07/202108:32
25.00
39328.0
5.34
7.97
27.10
12
09/07/202108:31
26.81
41891.0
5.13
7.92
27.30
DHT-4
24
09/07/202108:30
26.94
42068.0
5.11
7.88
27.30
28
09/07/202108:30
26.94
42076.0
5.15
7.82
27.30
4
09/13/202108:36
24.90
39140.0
5.45
7.96
25.60
12
09/13/202108:35
24.91
39160.0
5.54
7.96
25.60
DLT-1
24
09/13/202108:35
24.93
39190.0
5.56
7.95
25.60
36
09/13/202108:34
24.93
39190.0
5.93
7.93
25.60
4
09/13/202109:06
26.47
41345.0
4.48
7.88
25.40
12
09/13/202109:05
26.47
41345.0
4.92
7.88
25.40
DLT-2
24
09/13/202109:05
26.57
41487.0
5.08
7.88
25.40
32
09/13/202109:04
27.81
43240.0
4.74
7.88
25.80
4
09/13/202108:53
26.46
41345.0
4.36
7.80
25.70
DLT-3
12
09/13/202108:53
26.53
41445.0
4.68
7.80
25.70
26
09/13/202108:52
26.59
41525.0
5.04
7.80
25.70
4
09/13/202108:19
25.63
40148.0
5.55
7.82
24.90
DLT-4
10
09/13/202108:18
25.66
40203.0
6.06
7.79
24.90
4
09/13/202114:42
28.88
44768.0
6.15
8.21
26.90
12
09/13/202114:42
28.89
44775.0
6.29
8.21
26.90
24
09/13/202114:41
28.87
44747.0
6.21
8.20
26.90
DHT-1
36
09/13/202114:41
28.86
44737.0
6.16
8.20
26.90
48
09/13/202114:40
28.81
44665.0
6.25
8.19
26.90
54
09/13/202114:38
28.64
44426.0
6.41
8.14
26.90
12
09/13/202115:10
25.29
39822.0
6.30
8.17
29.30
DHT-2
24
09/13/202115:09
25.49
40098.0
6.15
8.15
29.00
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Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
Table-.
Station
DLT and DHT
High .-
Meas.
Depth (in)
Denotes the Sampling
Condition, Respectively.
Time
Event
Salinity
(psu)
which Was Collected
Spc. Cond
(PS/cm)
during
DO
(mg/L)
Low Tide
pH
. 04
and
Temp.
(IC)
36
48
09/13/202115:08
09/13/202115:07
25.70
40381.0
5.69
8.12
1 28.90
26.53
41528.0
5.75
8.06
28.00
4
09/13/202114:57
25.58
40257.0
6.19
8.15
30.00
12
09/13/202114:57
25.60
40282.0
6.38
8.13
29.90
DHT-3
24
09/13/202114:56
25.95
40759.0
5.33
8.02
29.30
36
09/13/202114:56
26.79
41884.0
4.76
7.96
28.00
48
09/13/202114:55
26.96
42117.0
4.49
7.96
27.60
4
09/13/202114:28
1 26.47
41422.0
6.41
8.12
27.70
DHT-4
12
09/13/202114:27
26.48
41447.0
6.70
8.10
27.70
26
09/13/2021 14:27
26.49
41458.0
6.94
8.06
27.70
2.2.2 Laboratory Data
Table 2-2 presents the laboratory analyses for the discrete high tide and low tide grab samples.
Pace Analytical Services, LLC performed the laboratory analyses for pH, total suspended solids,
biochemical oxygen demand, total nitrogen, ammonia, total Kjeldahl nitrogen (TKN), total
phosphorus, ortho-phosphate, and total organic carbon. The detailed laboratory data and their
quality controls are provided in Appendix B. In general, nutrient levels both outside in White
Oak River and in the creek are low with somewhat higher levels in the creek. Chl a levels in the
first two measurements (August 10 and 17) were higher within the creek with levels in the 70 to
80 ug/L range while the samples in the White Oak River remained around and below 20 ug/L.
Chl a levels through the remaining period dropped down to at or below 20 ug/L for the remaining
samples. BOD levels were generally low in the non -detect (ND) for most of the samples with
some higher levels at the beginning of the measurements as was seen for Chl a.
The laboratory data were used in the development of the water quality model to show that the
simulations have reasonable constituent concentrations.
2.3 Continuous Data
Two YSI Sondes (EX02) were deployed at Continuous 01 and Continuous 02 (Figure 1-2) to
collect water levels, salinity, temperature, pH, dissolved oxygen, etc. from August 9 to
September 13, 2021. Statistics of the measured data at the continuous stations are provided in
Table 2-3. Section 2.3.1 describes the variation in water surface elevation. Salinity and
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Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
temperature are presented in Section 2.3.2. pH measurements are described in Section 2.3.3,
followed by dissolved oxygen in Section 2.3.4.
2.3.1 Water Levels
ATM collected water surface elevations above North American Vertical Datum of 1988
(NAVD88) at the stations Continuous 01 and Continuous 02 from August 9 to September 13 in
2021. Water surface elevation varied from -0.7 m to 0.14 m at both stations. As the distance
between Continuous 01 and 02 is about 350 yards, no difference in phase and amplitude was
observed. Thus, water surface elevations were mostly overlapped as they look like one time -
series (Figure 2-11). The water surface elevations are predominantly semi -diurnal, with
presenting wind -driven effects. The average water surface elevation was about -0.26 m during
the measurement period.
0.2
00
°0 0
Q
Z
ro -0.2
0
n
-0.4
E
W
(n -0.6
08
08/09 08/14 08/19 08124 08/29 09/03 09/08 09/13
Days of 2021
Figure 2-11. Water Surface Elevation (m) above NAVD88 at Continuous Olin green solid line and
Continuous 02 in red solid line.
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Flushing and Dissolved Oxygen Study
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TableResults
True Ortho-
Tide pH Color TSS BOD5 TN Ammonia TKN NO2/NO3 TP phosphate as P TOC Chl a
Station Condition Date Time std units units m /L m /L m /L m /L m /L m /L m /L m /L m /L /L
Discrete 01
Low Tide
8/10/2021
9:25 6.7 300 6.6 5.3 1.3 ND 1.1 0.12 0.070
9:25 6.9 250 6.6 3.4 1.4 ND 1.3 0.083 0.36
ND 21.6 16.2
Discrete 01
High Tide
8/10/2021
ND
18.8
6.7
Discrete 01
Low Tide
8/17/2021
9:45
7.3
250
6.4
ND
1.1
ND
1.1
0.055
0.065
0.21
18.6
9.1
Discrete 01
High Tide
8/17/2021
9:45
6.8
200
32.8
ND
1.3
ND
1.3
0.050
0.092
ND
17.1
12.9
Discrete 01
Low Tide
8/24/2022
10:25
7.6
200
7.2
ND
0.73
ND
0.69
ND
ND
ND
17.9
8.3
Discrete 01
High Tide
8/25/2022
10:25
7.6
150
12.6
ND
1.9
ND
1.8
ND
0.051
ND
16.5
10.0
Discrete 01
Low Tide
9/1/2021
9:45
7.5
150
13.4
ND
1.8
ND
1.8
ND
ND
ND
17.4
9.4
Discrete 01
High Tide
9/1/2021
9:45
7.6
125
29.5
ND
2.2
ND
2.2
ND
ND
ND
13.1
9.6
Discrete 01
Low Tide
9/8/2021
11:45
7.9
100
27.6
ND
1.2
ND
1.2
ND
ND
ND
8.9
9.5
Discrete 01
High Tide
9/8/2021
11:45
7.8
75.0
29.1
ND
1.3
ND
1.3
ND
0.052
ND
8.7
7.0
Discrete 01
Low Tide
9/14/2021
12:50
7.6
80.0
10.6
ND
1.2
ND
1.2
ND
ND
ND
10.0
4.9
Discrete 01
High Tide
9/14/2021
12:50
8.0
70.0
31.7
ND
0.91
ND
0.91
ND
0.060
ND
6.9
8.0
Discrete 02
Low Tide
8/10/2021
9:25
7.0
250
10.2
3.5
1.4
ND
1.3
ND
0.078
ND
20.2
33.8
Discrete 02
High Tide
8/10/2021
9:25
6.9
250
10.8
10.5
1.5
ND
1.4
ND
0.096
ND
21.0
43.8
Discrete 02
Low Tide
8/17/2021
9:45
7.3
300
6.8
2.6
1.7
ND
1.7
ND
0.086
0.058
19.6
75.9
Discrete 02
High Tide
8/17/2021
9:45
7.3
250
14.6
ND
1.3
ND
1.2
ND
0.076
0.051
18.2
20.7
Discrete 02
Low Tide
8/24/2021
10:05
7.4
175
15.1
ND
0.75
ND
0.72
ND
0.050
0.063
15.6
11.1
Discrete 02
High Tide
8/25/2021
10:25
7.7
150
9.9
2.1
0.94
ND
0.93
ND
ND
ND
14.7
14.6
Discrete 02
Low Tide
9/1/2021
9:45
7.5
125
36.0
ND
1.7
ND
1.7
ND
0.081
ND
14.8
15.3
Discrete 02
High Tide
9/1/2021
9:45
7.6
150
47.7
ND
1.9
ND
1.9
ND
0.090
ND
15.6
18.1
Discrete 02
Low Tide
9/8/2021
11:45
7.6
125
33.2
ND
1.4
ND
1.4
ND
0.059
ND
10.0
10.9
Discrete 02
High Tide
9/8/2021
11:45
7.7
100
30.1
ND
0.81
ND
0.81
ND
0.056
ND
10.6
8.8
Discrete 02
Low Tide
9/14/2021
12:50
7.6
80.0
20.5
ND
0.72
0.11
0.72
ND
0.077
ND
9.2
10.5
Discrete 02
High Tide
9/14/2021
12:50
8.0
100
17.1
ND
1.1
ND
1.1
ND
0.054
ND
10.2
7.7
Discrete 03
Low Tide
8/10/2021
9:25
7.1
250
12.7
9.1
1.6
ND
1.6
ND
0.086
ND
20.8
70.2
Discrete 03
High Tide
8/10/2021
9:25
7.0
300
9.5
5.5
1.3
ND
1.3
0.052
0.069
ND
21.1
25.6
Discrete 03
Low Tide
8/17/2022
9:45
7.2
250
12.3
2.7
1.3
ND
1.2
ND
0.079
ND
19.5
34.7
Discrete 03
High Tide
8/17/2021
9:45
7.0
300
14.0
2.3
1.7
ND
1.6
ND
0.092
0.054
19.8
36.3
Discrete 03
Low Tide
8/24/2021
10:05
7.4
150
11.6
ND
0.99
ND
0.99
ND
0.054
ND
13.8
17.1
Discrete 03
High Tide
8/24/2021
10:05
7.8
150
15.2
ND
0.75
ND
0.73
ND
ND
ND
14.8
16.7
Discrete 03
Low Tide
9/1/2021
9:45
7.5
125
13.0
ND
1.3
ND
1.3
ND
0.060
ND
15.2
15.9
Discrete 03
High Tide
9/1/2021
1 9:45
1 7.6
150
34.0
2.0
1.1
ND
1.1
ND
0.080
ND
15.0
16.5
Discrete 03
Low Tide
9/8/2021
11:45
7.7
75.0
14.5
ND
1.8
ND
1.8
ND
0.057
ND
10.7
13.2
Discrete 03
High Tide
9/8/2021
11:45
7.7
100
28.7
ND
0.98
ND
0.98
ND
0.064
ND
10.6
10.6
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ATM
-N%k--
A Geosyntec Company 2 -2 0

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
TableResults
True Ortho-
Tide pH Color TSS BOD5 TN Ammonia TKN NO2/NO3 TIP phosphate as P TOC Chl a
Station Condition Date Time (std units) (units) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (Ng/L)
Discrete 03
Low Tide
9/14/2021
12:50
7.6 100
14.1 ND
1.2
ND 1.2 ND ND
ND 1.2 ND 0.064
ND
9.5
10.1
9.0
8.9
Discrete 03
High Tide
9/14/2021
12:50
7.9
100
29.7
ND
1.2
ND
Discrete 04
Low Tide
8/10/2021
9:25
6.9
250
11.3
2.1
1.2
ND
1.1
0.092
0.071
0.057
20.4
14.5
Discrete 04
High Tide
8/10/2021
9:25
6.7
250
7.5
4.2
1.7
ND
1.6
0.10
0.070
ND
21.3
16.1
Discrete 04
Low Tide
8/17/2021
9:45
7.2
200
7.1
ND
1.2
ND
1.2
ND
0.050
0.063
16.6
9.3
Discrete 04
High Tide
8/17/2021
9:45
6.8
200
11.6
ND
2.1
ND
2.1
ND
0.056
ND
19.2
25.0
Discrete 04
Low Tide
8/24/2021
10:05
7.5
150
11.9
ND
0.67
ND
0.64
ND
ND
0.065
15.9
8.9
Discrete 04
High Tide
8/24/2021
10:05
7.7
125
12.5
ND
1.0
ND
0.97
ND
ND
ND
12.2
9.7
Discrete 04
Low Tide
9/1/2021
9:45
7.5
125
14.1
ND
0.85
ND
0.83
ND
0.051
ND
13.6
6.2
Discrete 04
High Tide
9/1/2021
9:45
7.4
150
34.7
ND
1.6
ND
1.6
ND
0.060
ND
15.2
12.0
Discrete 04
Low Tide
9/8/2021
11:45
7.9
125
19.8
ND
1.3
ND
1.2
ND
ND
ND
8.2
8.0
Discrete 04
High Tide
9/8/2021
11:45
7.8
75.0
21.8
ND
1.2
ND
1.2
ND
ND
ND
9.5
5.1
Discrete 04
Low Tide
9/14/2021
12:50
8.0
100
9.8
ND
0.71
ND
0.71
ND
ND
ND
9.2
4.8
Discrete 04 High Tide 9/14/2021 12:50 7.4
100
21.8
ND
1.0
ND
1.0
ND
0.060
ND
9.9
5.5
ND - Not Detected at or above adjusted reporting limit.
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ATM
-N%k--
A Geosyntec Company 2 -21

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
2.3.2 Salinity and Temperature
Salinity and temperature were collected at the stations Continuous 01 and Continuous 02
(Figure 2-12A and Figure 2-12B). Salinities were higher during flood at Continuous 01 than at
Continuous 02 but were lower during ebb at Continuous 01 than Continuous 02. The
Continuous 01 is located out of the Unnamed tributary (Figure 1-2), where water can be readily
exchanged. The Continuous 02 is in the semi -enclosed basin (Figure 1-2). This led the
difference of salinities between Continuous 01 and Continuous 02. Salinity at Continuous 01
and Continuous 02 mainly present with a semi -diurnal cycle, and the amplitude of salinity
variation at Continuous 01 was larger than at Continuous 02. The semi -diurnal variation is
relatively clear at Continuous 01 since the station is located in the mainstream of the White Oak
River. Temperatures at both stations dominantly present as a diurnal cycle. Unlike salinity,
temperatures in the daytime were higher at Continuous 02 than at Continuous 01, which
indicates the semi -enclosed basin restricts the exchange of water from White Oak River. There
is a stagnation period of water in the Unnamed tributary. This led the water in the Unnamed
tributary to be warmer than in the White Oak River.
2.3.3 pH
pH was collected at Continuous 01 and Continuous 02 from August 09 to September 13 in 2021
using YSI Sonde (EX02) (Figure 2-13). pH has a negative correlation to temperature and
salinity, that is, pH decreases with increase in temperature and salinity, and vice versa. pH at
Continuous 02 is relatively lower than pH at Continuous 01. However, pH is still lower at
Continuous 02 than Continuous 01, even though salinity (Figure 2-12A) is lower, especially
during flood, at Continuous 02 than at Continuous 01. The periodicity of pH oscillations presents
more semi -diurnal at Continuous 01 than at Continuous 02. This indicates pH tends to be more
negatively correlated with temperatures than with salinity. pH is relatively lower at Continuous
02, especially during daytime, than at Continuous 01, because the temperature is higher at
Continuous 02 than at Continuous 01 (Figure 2-12B).
W i R/213667. D 2 D/7/S/2022
ATM
2-22

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
35
A)
30
25
cn 4
,2; 20
cu 15
U
10
5
Continuous 01 Continous 02
0
40
B)
U 35
a)
m 30
a�
a
E
Q)
25
20
08/09 08114 08/19 08124 08129 09/03 09/08 09/13
Days of 2021
Figure 2-12. A) Salinity (psu) and B) Temperature (°C) measurements at Continuous 01 in green
solid line and Continuous 02 in red solid line.
8.5
8
: 7.5
7
6.5
08/09 08114 08/19 08/24 08/29 09/03 09108 09/13
Days of 2021
Figure 2-13. pH measurements at Continuous 01 in green solid line and Continuous 02 in red solid
line.
W i R/213667. D 2 D/7/8/2022
ATM
A Geosymec Company 2-23

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
2.3.4 Dissolved Oxygen
Dissolved oxygen concentrations were collected at Continuous 01 and Continuous 02 (Figure
2-14), from August 9 to September 13 in 2021 using the YSI Sonde (EX02). The dissolved
oxygen was mostly lower at Continuous 02 than Continuous 01, especially in the daytime, as
the water temperatures were higher at Continuous 02 than at Continuous 01. Dissolved oxygen
was negatively correlated with water temperature. The periodicity of dissolved oxygen
dominantly presents as a diurnal cycle. This is evidence that dissolved oxygen is more affected
by water temperature than salinity and also likely represents the algal growth and respiration
cycle. The standard deviation of dissolved oxygen was 1.24 mg/L at Continuous 02, about
twice as high as 0.59 mg/L at Continuous 01, even though the standard deviation of
temperatures was 2.27°C at Continuous 02, not as different as 1.96 °C at Continuous 01.
Examination of the continuous dissolved oxygen measurements shows that the creek at times
does go below the 5.0 mg/L daily average criteria, while the White Oak River does not. As
such, it is important that the introduction of the marina basin will not degrade the dissolved
oxygen conditions in the creek below the present baseline condition. This will be a key goal of
the water quality modeling analyses presented in Section 4.0.
T
Continuous 01 —Continous02
0
08/09 08/14 08119 08/24 08/29 09/03 09/08 09/13
Days of 2021
Figure 2-14. Dissolved oxygen (mg1L) at Continuous 01 in green solid line and Continuous 02 in
red solid line.
W i R/213667. D 2 D/7/S/2022
AT_M
walh
2-24

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
Table of Water Quality
and Continuous 02
Statistics
Station Parameter Max Mean Min STD
WSE (m)
0.14
-0.26
-0.70
0.16
Salinity (psu)
33.00
19.38
1.60
7.56
Continuous 01
Temperature (°C)
33.70
29.47
24.62
1.96
pH
7.94
7.63
6.86
0.18
DO (mg/L) 7.96 5.93
4.08
0.59
WSE (m) 0.15 -0.25
0.16
-0.70
Salinity (psu) 33.05 19.06
3.09
7.47
Continuous 02
Temperature (°C) 36.04 29.76
23.58
2.27
pH 8.13 7.47
6.79 J
0.22
DO (mg/L) 8.36 5.07
0.62
1.24
(• IRM:Me
LMG measured rain depth (inch/day) at the unnamed tributary from August 8 through
September 13, 2021. The measured rainfall is presented in Figure 2-15. ATM utilized the rain-
fall data in the development of the hydrodynamic model as part of the meteorological forcing.
0.20
0.18
0.16
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0.00
08/08
08/13 08/18 08/23 08/28 09/02 09/07
Days of 2021
Figure 2-15. Rain (inch/day) Data Onsite.
09/12
W i R/213667. D 2 D/7/8/2022
ATM
-N%k--
A Geosyntec Company 2-25

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
3.0 Hydrodynamic Model Development and Flushing Assessment
ATM developed a hydrodynamic and flushing model to simulate circulation and the time to flush
a conservative tracer out of the final design of the post -project marina basin as described in
Section 1. The EFDC model is described in Sections 3.1 and 3.2. The model boundary
conditions are described in Section 3.3, along with inputs. The model calibration is presented in
Section 3.4, following with the results of flushing simulations in Section 3.5.
3.1 Model Description
The EFDC is a general-purpose hydrodynamic model, typically used to simulate two-
dimensional and three-dimensional flow, circulation, transport, and biogeochemical processes in
surface water systems, including rivers, lakes, estuaries, reservoirs, wetlands, and nearshore-
scale to continental -shelf -scale coastal systems. EFDC is software currently supported by the
EPA Office of Research and Development (ORD).
EFDC solves the three-dimensional, hydrostatic, free -surface, turbulent -averaged equations of
motions for a variable -density fluid. Dynamically coupled transport equations for turbulent
kinetic energy, turbulent length scale, salinity, and temperature are also solved. Two turbulent
transport equations implement the Mellor -Yamada level 2.5 turbulence closure scheme. EFDC
uses a grid with a stretched or sigma vertical geometry and curvilinear, orthogonal, horizontal
geometry.
EFDC solves the equations of motion with a second -order accurate spatial finite differencing
scheme on a staggered or C grid. The model's time integration employs a second -order
accurate three -time -level, finite difference scheme with an internal -external mode splitting
procedure to separate the internal shear or baroclinic mode from the external free -surface
gravity wave or barotropic mode. The external mode solution is semi -implicit and simultaneously
computes the two-dimensional surface elevation field by a preconditioned conjugate gradient
procedure. The external solution is completed with the calculation of depth -average barotropic
velocities using the new surface elevation field. The model's semi -implicit external solution
allows large time steps constrained by stability criteria of either the explicit central difference
scheme or by a higher -order upwind advection scheme used for nonlinear accelerations.
Horizontal boundary conditions for the external mode solution include options for simultaneously
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Flushing and Dissolved Oxygen Study
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specifying the surface elevation only, the characteristic of an incoming wave, free radiation of an
outgoing wave, or the normal volumetric flux on arbitrary parts of the boundary.
3.2 Hydrodynamic and Flushing Model
ATM developed an EFDC model of White Oak River to evaluate the degree of flushing in the
proposed marina basin. The model extends from the bridge on State Road 24 near Swansboro
up through the bridge on County Road 1442 near Stella (Figure 3-1). The overall grid along with
the project location is presented in Figure 3-1. The model is forced with tides predicted at Bogue
Inlet (NOAA TEC 2837) on the boundary (Figure 3-1) near Swansboro. Other key inputs to the
model include the following:
• Freshwater inflows at the upstream of White Oak River and at the mouth of Hadnot
Creek. No discharge stations exist at the upstream of White Oak River and Hadnot
Creak, so the discharge data were obtained based on the nearest USGS station, New
River near Gum Branch, NC (USGS 02093000). ATM calculated the drainage area in
White Oak River and Headnot watershed. The area ratio of the New River watershed to
the White Oak River and Hadnot Creek watershed was applied to the discharge time -
series at the station, USGS 02093000.
• Wind data were obtained from Beaufort, Duke Marine Lab, NC (NOAA 8656483).
For the purposes of this flushing analysis, the flushing model was run in barotropic mode, which
simulates tide and wind -driven currents and water levels. The barotropic component of the
baseline model was calibrated to varying water level conditions moving upstream through the
system. The model has 1,438 horizontal grid cells and 4 vertical layers running in 3-D mode.
ATM developed an overall model grid (Figure 3-1) that covers White Oak River from Swansboro
up through Stella, NC. The base grid is fit to the shoreline based upon aerial photography. The
base grid includes the proposed marina basin. Figure 3-2 presents a zoomed -in view of the grid
with the proposed marina design.
Bathymetry for the base modeling was taken from NOAA navigation charts. Figure 3-3 shows
the overall model bathymetry, and Figure 3-4 shows a zoomed -in view of the bathymetry in the
vicinity of the proposed marina basin. The datum for the bathymetry and the water levels was
NAVD88.
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Flushing and Dissolved Oxygen Study
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Figure 3-1. Model Grid and the Proposed Marina (in red rectangle)
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Figure 3-2. Model Grid in the Proposed Final Marina Basin Design
W i R/213667. D 2 D/7/8/2022
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Figure 3-3. Overall Model Bathymetry
WiR/213667. D2 D/7/8/2022
ATM
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Flushing and Dissolved Oxygen Study
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3"11 7-1r-
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Figure 3-4. Model Bathymetry within the Proposed Final Marina Basin Design
3.3 Model Boundary Conditions
ATM forced the simulation with tides on the southern boundary of the overall model grid domain.
The tides were obtained from a tidal prediction station at Bogue Inlet, NC (NOAA TEC2837),
which is about 3 miles away from the southern boundary cells (Figure 3-1) near Swansboro.
Figure 3-5 presents a plot of the tidal forcing used on the offshore boundary. The tides from
August 22 through September 1 and from August 31 through September 10 were utilized for
simulation of the spring and neap tide conditions for the flushing evaluation.
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0.4
0.2
OD
on
0 0
Q
Z
> -0.2
0
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-0.4
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-0.6
-0.8
08/17 08/19 08/21 08123 08/25 08/27 08/29 08/31 09/02 09/04 09/06 09/08 09/10 09112 09/14
Days of 2021
Figure 3-5. Tidal Forcing Utilized on Southern Grid Boundary.
In addition to the tidal forcing, wind conditions were utilized to simulate hydrodynamics and
transport of a conservative dye tracer. Wind data for this project came from measured winds at
Beaufort, Duke Marine Lab, NC. The data were downloaded from a NOAA website that
maintains meteorologic information. The data were for the period when the instruments were in
place. Figure 3-6 presents a vector plot showing the wind directions and magnitude from
August 17, 2021, to September 15, 2021. As the data show, winds are primarily from the south.
These data were used to force the model for the validation and the flushing simulations.
15
10
5
E
0
c
-5
-10
15
DATA from NOAA, "Beaufort, Duke Marine Lab, NC - Station ID: 8656483"
08/17 08/19 08/21 08/23 08/25 08/27 08/29 08/31 09/02 09/04 09/06 09/08 09/10 09/12 09/14
Figure 3-6. Measured Winds at Beaufort, Duke Marine Lab, NC (August 1, 2021 to September 15,
2021)
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3.4 Model Calibration
The hydrodynamic model was run with the model grid and inputs as outlined in Sections 3.1
through 3.3. The model -simulated water levels based on the southern boundary forcing (Figure
3-5) were compared with the measurements at Continuous 01 to assure that the simulated
water levels at Continuous 01 were accurately simulated. Figure 3-7 presents a plot showing
comparisons of the simulated and measured water levels at Continuous 01. Spring and neap
simulation is presented in a blue solid line and in a red solid line, respectively. ATM extracted
the tidal harmonics from water level measurements described in Section 2 to compare the
simulated and measured water levels at Continuous 01 using least -square analysis.
Examination of the plots shows that the model is accurately simulating the tides at Continuous
01. This provides confidence in the model's ability to represent the overall circulation and the
driving forces that will impact flushing in the basin and channel.
Sim. Harmonics. S
0.1
00
00
j 0.1
Q
Z
x -0.2
0
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-0.5
-0.6
-0.7
08/23 08/25 08/27 08/29 08/31 09/02 09/04 09106 09/08
Days of 2021
Figure 3-7. Comparison of Simulated and Measured Water Levels at Continuous 01.
Sim. Harmonics, Neap Continuous 01, Harmonics)
09/10
3.5 Flushing Simulations
Using the model described above, ATM performed flushing evaluations through two periods
under spring and neap tide conditions with coincident winds. The time periods for each of the
two simulations (spring and neap scenarios) are shown in Figure 3-5 and Figure 3-6. The spring
and neap scenarios were from August 17 through September 1, 2021, and from August 26
through September 10, respectively. Each scenario consisted of a 5-day spin -up period to get
the model simulation running stable. The dye was then released, and the simulation was run for
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an additional 10 days. As such, the period when the flushing was assessed was from August
22 to September 1, 2021 (spring scenario) and from August 31 to September 10 (neap
scenario). Examination of the tides plotted in Figure 3-5 shows that for the spring scenario, the
system starts at a spring tide condition and moves into a neap tide condition. For the neap
scenario, the system starts at a neap tide condition and moves into a spring tide condition.
ATM simulated the concentration of a synthetic, hypothetical tracer initialized in the planned
marina basin with a dye concentration of 100. As stated previously, the goal is for the planned
marina basin will flush within a reasonable period of time for the -1.7 m NAVD88 depth.
As part of the flushing simulations, ATM evaluated an initial single entrance basin design.
Flushing results from those simulations did not meet DEQ standards for 85 to 90 percent
reduction in dye mass in 24-hours. The basin layout and percent mass of dye for the single
entrance marina design are discussed in Section 3.5.1. Based on the poor flushing of the initial
marina design, the layout of the marina basin was revised in order to more closely match DEQ
recommendations for design of marina basins to maximize flushing. The revised layout
consisted of two connections to the creek, with a main entrance at the southern end of the basin
and a flushing channel at the northern end. The basin layout and flushing results for the revised
marina basin are presented in Section 3.5.2.
3.5.1 Initial Marina Basin Design Flushing Results
Figure 3-8 presents the basin layout for the initial single entrance marina design. Additionally,
the initial mass of dye for the flushing simulation is shown. The flushing time is defined as the
time it takes to reduce the overall mass in the system to 10 to 15 percent of its original mass per
DEQ. Per DEQ guidance on flushing, it is desirable that the dye concentration be dropped
below 10 to 15 percent within a 24-hour period.
Figure 3-9 and Figure 3-10 present time series plots of the percent mass of dye remaining over
time for the spring and neap simulations, respectively. Examination of the plots shows that the
single entrance marina basin reaches the 10 percent dye remaining criteria between around 4 to
5 days, depending upon the spring or neap tide simulation. This is not acceptable under
present DEQ guidelines. Additionally, DEQ recommendations on design layouts for marina
basins look to avoid this type of one entrance condition.
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Figure 3-8. Initial Dye Concentration and Basin Layout for Initial Marina Basin Design
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Flushing and Dissolved Oxygen Study
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Simulation Start: 08/22/2021
70
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20
10
0
0 1 2 3 4 5 6 7 8 9 10
Days
Figure 3-9. Percent Mass Dye Remaining in Initial Marina Basin Design Over Time (spring
scenario)
Simulation Start: 08/31/2021
100
90
80
6' 70
E 60
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ry
ui 50
40
m
U
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a 30
20
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.......................................................
0 1 2 3 4 5 6 7 8 9 10
Days
Figure 3-10. Percent Mass Dye Remaining in Initial Marina Basin Design Over Time (neap
scenario)
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Flushing and Dissolved Oxygen Study
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3.5.2 Revised Marina Basin Design Flushing Results
Figure 3-11 presents the basin layout for the revised dual, flow through, marina design.
Additionally, the initial mass of dye for the flushing simulation is shown. Figure 3-12 and Figure
3-13 present time series plots of the percent mass of dye remaining over time for the spring and
neap simulations, respectively. Examination of the plots shows that the dual opening, flow
through design, flushes within the prescribed 24-hour period. These results demonstrate that
the two openings drive significant flow through, leading to very good flushing. Based on
this level of exchange it would not be envisioned that the interior areas should have poor water
quality.
Figure 3-11. Initial Dye Concentration and Basin Layout for Revised Marina Basin Design
WiR/213667. D2 D/7/8/2022
ATM
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Flushing and Dissolved Oxygen Study
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Simulation Start: 08/22/2021
100
90
80
0' 70
M
E 60
am
50
40
m
U
L
a 30
20
10
0
0 1 2 3 4 5 6 7 8 9 10
Days
Figure 3-12. Percent Mass Dye Remaining in Revised Marina Basin Design Over Time (Spring
Scenario)
Simulation Start: 08/31/2021
100
90
80
70
.E
E 60
am
w
2nn 50
M
40
a�
U
L
a 30
20
10
0
0 1 2 3 4 5 6 7 8 9 10
Days
Figure 3-13. Percent Mass Dye Remaining in Revised Marina Basin Design Over Time (neap
scenario)
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Flushing and Dissolved Oxygen Study
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4.0 Water Quality Model Development and Dissolved Oxygen
Assessment
ATM developed a water quality model driven by the hydrodynamic model (presented in Section
3) to simulate water quality within the model domain as a function of circulation and biological
and chemical processes, for application to both the pre- and post -project scenarios. The
primary goal is to develop a water quality model that reasonably simulates the water quality
constituents that impact dissolved oxygen to provide a reasonable simulation of the pre- versus
post -project differences in dissolved oxygen. Limited data on overall model boundary conditions
for the full model restricts the ability to full model calibration so that the goal is to provide a
baseline model that would reasonably simulate the difference in the pre- versus post -project
conditions.
The EFDC water quality model is described in Section 4.1. The water quality model boundary
conditions are described in Section 4.2, along with inputs. The model reasonableness for the
existing condition scenario is presented in Section 4.3, followed by the results of the pre- versus
post -project scenario in Section 4.4.
4.1 Model Description
The water quality biological and chemical transformation processes in the EFDC water quality
model are based on those in CE-QUAL-ICM, a water quality model developed by Cerco and
Cole (1995) and described in Park et al. (1995). The model computes and reports
concentrations, mass transport, kinetics transformations, and mass balances. The model
computes 21 state variables, including four classes of algae, organic carbon species,
phosphorus and nitrogen species, and dissolved oxygen. Unlike the WASP water quality
model, which uses biochemical oxygen demand to represent oxygen -demanding organic matter,
the EFDC water quality model uses carbon. The three organic carbon state variables in EFDC
play an equivalent role to biochemical oxygen demand. The four algae groups (cyanobacteria,
diatoms, green algae, and stationary algae) are represented in carbon units (Tetra Tech, 2007).
The three main organic nutrients (carbon, nitrogen, and phosphorus) can be represented in
three reactive forms (refractory particulate, labile particulate, and labile dissolved), which allows
for a more realistic distribution of organic material by reactive classes when data are available to
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estimate distribution factors. A detailed description of the role of the individual variables and
their respective kinetic interaction processes is present in Tetra Tech (2007).
Input data requirements for driving the EFDC water quality model, in addition to the
hydrodynamic model state variables (salinity, temperature, water surface elevation, transport)
which is fed directly to the water quality model during runtime, include the following:
• Downstream water quality boundary conditions;
• Upstream water quality boundary conditions/water quality constituent loads;
• Meteorological data (solar radiation, cloud cover, air temperature); and
• Bottom nutrient and dissolved oxygen fluxes.
4.2 Model Boundary Conditions
Upstream and downstream water quality boundary conditions were input as concentrations for
each constituent. Given the limited data available for establishing the boundary conditions at
the two extremes of the model domain, measured data in the White Oak River at Discrete 01 for
August 2021 were used to develop reasonable temporally constant, vertically averaged
boundary conditions for both upstream and downstream boundaries. Upstream boundary
concentrations for carbon species, nitrogen species, and phosphorus species were set at
reasonable values higher than the downstream concentrations derived from the observed data
in the White Oak River, as representative of the runoff characteristics of the upstream
watershed. Both upstream and downstream boundary conditions for dissolved oxygen were set
to 6.8 mg/L, a reasonable value given the available data collected during this project from the
discrete and continuous recorder data collection.
Meteorological data used to drive the water quality model are the same as those used as input
to the hydrodynamic model, including hourly records of incoming solar radiation. For the
purposes of this effort, all bottom nutrient fluxes were set to 0, with sediment oxygen demand
parameterized as 0.2 g/m2/d within the White Oak Creek portions of the model domain (based
on simulations of the exterior DO), and (per DEQ requirements) 1.5 g/m2/d inside the creek and
proposed marina basin.
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4.3 Model Calibration
As described previously, no water quality data were collected at the downstream model domain
boundary or at the upstream input locations, so that assumptions were made to develop
reasonable conditions for upstream and downstream water quality boundary conditions used for
the water quality model. The water quality modeling effort was directed toward simulating
reasonable water quality responses, with a focus on dissolved oxygen, to allow comparison of
pre- and post -development conditions. A check of the reasonableness of the simulation results
was performed by comparing the model output for the existing condition (pre -development) to
data collected near the planned project location in August and September 2021.
Comparisons of simulated and observed 15-minute dissolved oxygen at the two continuous
recorders (Continuous 01 and Continuous 02 in Figure 1-213) are provided in Figure 4-1 and
Figure 4-12, respectively, below. As shown in Figure 4-1, the simulated dissolved oxygen
values in White Oak River outside the mouth of the tributary are very similar to those observed
for the most part. As shown in Figure 4-2, the simulated dissolved oxygen values within the
tributary do not have the same range of values for a given day as do the observed data, but
appear to provide reasonable simulation of conditions averaged over a period longer than the
15-minute frequency of the observations and model output.
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DO(MWW CR01 (28,41): DO {mgfQ
— Ohser+red od
— Pfedicted WC Avg DO
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15 16 17 19 19 20 21 22 23 24 25 26 27 28 29 30 3i 32 33 34 35 36 37 39 39 40 41 '.- 4. .14 45
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Figure 4-1. Observed and simulated 15-minute dissolved oxygen at Continuous 01 outside the
mouth of the tributary in White Oak River for 15 August - 13 September 2021.
Observed data are represented by the blue line, while the simulated water column average values
are indicated by the green line and simulated surface values are indicated by the black line.
�,s a CR02 (34.41): DO (mglL)
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iy 1v 1` is 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 Y6 37 38 39 40 47 a2 43 443
DaaT. I Mug21 - 13Sep21
Figure 4-2. Observed and simulated 15-minute dissolved oxygen at Continuous 02 inside the
mouth of the tributary for 15 August - 13 September 2021
Observed data are represented by the blue line, while the simulated water column average values
are indicated by the green line, simulated surface values are indicated by the black line, and
simulated bottom values are indicated by the orange line.
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To further evaluate the reasonableness of the dissolved oxygen simulation of observed
conditions, the daily average observed and simulated dissolved oxygen values at each of the
continuous recorder locations were evaluated, with time series plots of these daily average
values provided in Figures 4-3 and 4-4 at Continuous 01 and Continuous 02, respectively. It is
notable that at both locations, the simulated surface and water column daily average dissolved
oxygen values are very similar to the observed daily average values and likely presents a more
conservative simulation as the simulations are generally lower. It is important to note that the
prescription of the interior SOD (1.5 g/m2/d) in the model was a factor in the simulations as this
value was not available for modification to create a closer fit. Based on the lower simulated DO
overall, this value may higher than actually exists in the system. Based on these results, it is
concluded that the water quality model is sufficient for simulation of reasonable dissolved
oxygen conditions in the river and in the tributary, so that the model may be utilized to evaluate
expected changes in dissolved oxygen within the area of interest due to the introduction of the
marina basin.
CR01 (28.41): Daily Avg DO (mg1L)
Observed QO
Predicted WC Avg 100
o.a.c. a... nn
5 16 1i 78 1919 20 21 22 23 24 25 28 27 28 29 90 31 9 33 3� 36 35 97 38 39 45 47 d2 43 44 1�
Oay: I Mug2l .138ep21
Figure 4-3. Observed and simulated average daily dissolved oxygen at Continuous 01 outside the
mouth of the tributary in White Oak River for 15 August - 13 September 2021
Observed data are represented by the blue line, while the simulated water column average values
are indicated by the green line and simulated surface values are indicated by the black line.
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r pn,> PAA Al). ni kiiv 8tixr, nr7 rmmi 1
0
15 16 17 t8 19 20 21 22 23 24 25 26 27 2$ 29 30 31 32 33 34 35 36 37 38 39 43 :1 4.2 4: �-5
Day. ISAug21-13Sep21
Figure 4-4. Observed and simulated average daily dissolved oxygen at Continuous 02 inside the
mouth of the tributary for 15 August - 13 September 2021
Observed data are represented by the blue line, while the simulated water column average values
are indicated by the green line, simulated surface values are indicated by the black line, and
simulated bottom values are indicated by the orange line.
Additional water quality data were collected at the four discrete stations shown in Figure 1-213.
Comparisons of total nitrogen and total phosphorus concentrations from these events were
made to those simulated at the four locations. Measured total nitrogen concentrations were 1.1
mg/L to 2.1 mg/L, with a mean of 1.4 mg/L, compared to the simulated mean total nitrogen
concentration of 1.0 mg/L during the same days when the data were collected. Measured total
phosphorus concentrations were 0.050 mg/L to 1.070 mg/L, with a mean of 0.156 mg/L,
compared to the simulated mean total phosphorus concentration of 0.090 mg/L during the same
days when the data were collected. Although the simulated mean values for both total nitrogen
and total phosphorus are somewhat less than the observed mean values, the simulated mean
values are within the range of the observed data for total phosphorus and nearly so for total
nitrogen, and are reasonable for an estuarine river. It is also certain that the differences in
observed and simulated nutrient levels are at least partially the result of uncertain upstream
inputs and downstream boundary conditions.
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Given the findings described here with respect to dissolved oxygen, total nitrogen, and total
phosphorus, the water quality model is considered appropriate for utilization in comparison of
pre- and post -development conditions for this system.
4.4 Dissolved Oxygen Simulations
Utilizing the model described in the previous sections, simulations were made under the pre -
versus post -project conditions within the creek and within the marina basin area under the
revised design scenario. As outlined in Section 4.3, the model calibration was done on the pre -
project condition, i.e., without the marina basin in place and the calibrated model then
represents the pre -project model for the dissolved oxygen analyses. As such, the only change
that was made to the water quality model for the post -project simulations is the inclusion of the
revised marina basin design into the model grid as outlined in Section 3.0 for the post -project
flushing analyses. Sediment oxygen demand levels for all post -project additional grid cells were
set to 1.5 g/m2/d, per DEQ requirements. The simulated pre- and post -project dissolved oxygen
concentrations were then compared at various locations within the creek to identify any
changes. Additionally, the simulated dissolved oxygen conditions within the proposed marina
basin were evaluated to see if the values were outside of the range of values simulated in the
creek. The simulation results are presented for the critical period (following model spin up) from
August 15, 2021, through September 15, 2021.
Pre- and post -project simulated dissolved oxygen concentrations were output from the model at
locations just outside of the creek, within the creek and within the proposed marina basin.
Figure 4-5 presents a map showing the various locations where model output was extracted and
the grid cell ids for each.
Figure 4-6 (a,b) through Figure 4-11 (a,b) present comparison plots of the simulated pre- versus
post -project simulated dissolved oxygen concentrations just outside and within the creek. The
results are plotted for all of the layers (a) and for the vertically integrated concentrations (b).
Comparison plots are provided all along the creek. Examination of the plots shows that there is
very little discernable difference between the pre -versus post -project dissolved oxygen
concentrations. The differences that are seen would be deemed ecologically insignificant in
terms of impacts related to changes in dissolved oxygen. The differences that do exist are
found more at the stations just inside the creek where the entrances to the basin are located.
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Figure 4-12 (a,b) and Figure 4-13 (a,b) present the simulated post -project dissolved oxygen
concentrations within the marina basin. Examination of the time series shows that the dissolved
oxygen conditions within the proposed marina basin are not significantly different than those
simulated within the creek. This shows that the introduction of the marina basin, with the flow
through situation and the good flushing, will not have reduced dissolved oxygen levels
compared to those already found within the creek following construction of the project. This
aspect is further supported by the plots of daily averaged dissolved oxygen presented in Figure
4-14, where the pre -project condition simulations are presented as solid lines and the post -
project and marina simulations are presented as dashed or dashed -dotted lines. Examination of
the plot show that the marina simulations generally fall within the band of the existing
simulations especially during the lower dissolved oxygen periods.
Figure 4-5. Grid Locations in the Model for Output of Dissolved Oxygen Simulation Results
ATM
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b)
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Dissolved Oxygen (mg/L) at 1= 27 & J= 42
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08/15 08117 08119 08/21 08123 08/25 08/27 08/29 08131 09/02 09/04 09106 09/08 09110 09/12 09/14
Days of 2021
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08/15 08/17 08/19 08121 08/23 08/25 08127 08/29 08/31 09/02 09/04 09106 09/08 09/10 09112 09/14
Days of 2021
Figure 4-6. a) Comparison of Pre- versus Post -Project Simulated Dissolved Oxygen for all Vertical
Levels b) Comparison of Pre- versus Post -Project Simulated Vertically Averaged Dissolved
Oxygen (outside of Creek mouth)
ATM
-�--
A Geosyntec Company

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
a) Dissolved Oxygen (mg/L) at 1= 31 & J= 42
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08/15 08/17 08/19 08121 08/23 08125 08127 08129 08131 09102 09/04 09106 09108 09110 09/12 09/14
Days of 2021
Figure 4-7. a) Comparison of Pre- versus Post -Project Simulated Dissolved Oxygen for all Vertical
Levels. b) Comparison of Pre- versus Post -Project Simulated Vertically Averaged Dissolved
Oxygen (in Creek mouth)
ATM
-�--
A Geosyntec Company
4-10

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
a) Dissolved Oxygen (mglL) at 1= 35 & J= 42
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Days of 2021
Figure 4-8. a) Comparison of Pre- versus Post -Project Simulated Dissolved Oxygen for all Vertical
Levels b) Comparison of Pre- versus Post -Project Simulated Vertically Averaged Dissolved
Oxygen (in Creek at South Entrance to Basin)
ATM
-�--
A Geosyntec Company
4-11

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Amphitheater Road Marina
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08/15 08/17 08/19 08/21 08/23 08125 08/27 08/29 08/31 09102 09104 09/06 09/08 09/10 09112 09/14
Days of 2021
Figure 4-9. a) Comparison of Pre- versus Post -Project Simulated Dissolved Oxygen for all Vertical
Levels, b) Comparison of Pre- versus Post -Project Simulated Vertically Averaged Dissolved
Oxygen (in Creek at North Entrance to Basin)
ATM
-�--
A Geosyntec Company
4-12

a)
b)
Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
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08115 08117 08119 08/21 08/23 08125 08127 08129 08131 09102 09104 09106 09108 09110 09112 09/14
Days of 2021
Figure 4-10. a) Comparison of Pre- versus Post -Project Simulated Dissolved Oxygen for all
Vertical Levels. b) Comparison of Pre- versus Post -Project Simulated Vertically Averaged
Dissolved Oxygen (in Creek above Marina Entrances)
ATM
-�--
A Geosyntec Company
4-13

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Amphitheater Road Marina
Dissolved Oxygen (mg1L) at 1= 52 & J= 46
A) Existin -Proposed
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08115 08117 08119 08121 08123 08125 08127 08129 08131 09102 09104 09106 09108 09110 09112 09114
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08/15 08117 08119 08121 08123 08125 08127 08/29 08/31 09102 09/04 09106 09108 09/10 09112 09/14
Days of 2021
Figure 4-11. a) Comparison of Pre- versus Post -Project Simulated Dissolved Oxygen for all
Vertical Levels, b) Comparison of Pre- versus Post -Project Simulated Vertically Averaged
Dissolved Oxygen (in Creek in Upstream Fork)
ATM
-�--
A Geosyntec Company
4-14

a)
b)
Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
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08/15 08/17 08/19 08/21 08/23 08/25 08/27 08/29 08/31 09/02 09/04 09106 09/08 09110 09I12 09/14
Days of 2021
Figure 4-12. a) Post -Project Simulated Dissolved Oxygen for all Vertical Levels. b) Post -Project
Simulated Vertically Averaged Dissolved Oxygen (in Marina Basin - Southern End)
ATM
-�--
A Geosyntec Company
4-15

a)
b)
Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
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8.0 Depth -Averaged Dissolved Oxygen (mglL) at 1= 45 & J= 37
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08/15 08/17 08119 08/21 08123 08125 08127 08129 08131 09102 09/04 09106 09108 09110 09/12 09114
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Figure 4-13. a) Post -Project Simulated Dissolved Oxygen for all Vertical Levels, b) Post -Project
Simulated Vertically Averaged Dissolved Oxygen (in Marina Basin - Northern End)
ATM
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A Geosyntec Company
4-16

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Daily- and Depth -Averaged Dissolved Oxygen (mg/L)
EXST, i=35 j=42
EXST, i=46 j=42
EXST, i=50 j=42
EXST, i=52 j=35
-- PLND, i=35 j=42
-- PLND, i=46 j=42
-- PLND, i=50 j=42
- PLND, i=52 j=35
-- PLND, i=37 037
--- PLND, i=45 j=37
08/15 08/20 08/25 08/30 09/04 09/09 09/14
Days of 2021
Figure 4-14. Comparison of Simulated Pre- versus Post -Project Daily Averaged Dissolved Oxygen
Concentrations for Multiple Locations.
ATM
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A Geosyntec Company
4-17

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
5.0 Summary and Conclusions
In support of a permit application, ATM developed a hydrodynamic and water quality model to
evaluate the flushing and dissolved oxygen conditions within the proposed Amphitheater Road
Marina on a small tidal creek off the White Oak River near Peletier, in Carteret County, North
Carolina. LMG assisted ATM with this work by collecting hydrodynamic and water quality data
to support the model development and establish baseline water quality conditions.
Based on the field data collection and modeling presented previously in this report, the following
summarizes the findings from this work.
• An initial single entrance marina was evaluated using the hydrodynamic model and the
determination was made that this layout would not flush adequately.
• Based on the flushing evaluation of the initial design and recommendations by DEQ on
maximizing circulation and flushing in marina basins, the marina basin was redesigned
to provide for two openings with flow through.
• The revised layout was evaluated and determined to have adequate flushing to maintain
good water quality per DEQ requirements (less than 24 hours).
• Dissolved oxygen measurements in the creek show low dissolved oxygen levels and
times where the system goes below standards (daily average 5.0, instant low 4.0)
• Dissolved oxygen simulation modeling (with and without project comparisons) showed
that the introduction of the marina basin does not create ecologically significant
reductions in dissolved oxygen levels in the creek. This result is consistent with the
determination that a basin that has adequate flushing should not degrade local water
quality conditions.
• Dissolved oxygen simulation modeling showed that in comparison, the dissolved oxygen
levels in the basin are not lower than those already seen in the creek and, therefore,
does not create an area of lower dissolved oxygen than presently exists in the system.
ATM
—R*Ali--
A Ceosyntec Company
5-1

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
6.0 Literature Cited
Cerco, C.F., and T. Cole. 1995. User's Guide to the CE-QUAL-ICM Three -Dimensional
Eutrophication Model. Release Version 1.0. US Army Corps of Engineers, Waterways
Experiment Station, Technical Report EL-95-15.
Park, K., A.Y. Kuo, J. Shen, and J.M. Hamrick. 1995. A three-dimensional hydrodynamic-
eutrophication model (HEM3D): description of water quality and sediment processes
submodels. The College of William and Mary, Virginia Institute of Marine Science.
Special Report 327, 113 pp.
Tetra Tech. 2007. The Environmental Fluid Dynamics Code, Theory and Computation Volume
3: Water Quality Module. June 2007.
ATM
—R*Ali--
A Ceosyntec Company
6-1

Flushing and Dissolved Oxygen Study
Amphitheater Road Marina
Appendix A
Environmental Monitoring and
Hydrodynamic and Water Quality Simulation Plan
WiR/213667 D2D/7/8/2022
ATM
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DIRT2DREAMS, LLC
2021
i

Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
Amphitheater Road Marina July 23, 2021
Copyright and non -disclosure notice
The layout and contents of this plan, associated simulations, and associated materials are subject to copyright
owned by Applied Technology & Management, Inc., to the extent that copyright is legally assigned by us to
another party or is used by us under license. To the extent that Applied Technology & Management, Inc. own
the copyright in this plan, the plan may not be copied or used without our written agreement.
Third -party disclaimer
Any disclosure of this plan to a third party is subject to this disclaimer. The plan was prepared by Applied
Technology & Management, Inc. The plan does not in any way constitute advice to any third party who is able
to access the plan by any means. Applied Technology & Management, Inc. excludes, to the fullest extent
lawfully permitted, all liability whatsoever for any loss or damage howsoever arising from reliance on the
contents of this plan.
,�SICN
ENGINEERING
CONSULTING

Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
Amphitheater Road Marina July 23, 2021
Table of Contents
COPYRIGHT AND NON -DISCLOSURE NOTICE.....................................................................................................................................................................I
THIRD -PARTY DISCLAIMER....................................................................................................................................................................................................I
TABLEOF CONTENTS............................................................................................................................................................................................................. II
LISTOF TABLES...................................................................................................................................................................................................................... II
LISTOF FIGURES..................................................................................................................................................................................................................... II
LISTOF PHOTOGRAPHS....................................................................................................................................................................................................... III
ACRONYMS AND ABBREVIATIONS................................................................................................................................................................................... IV
NOTES...................................................................................................................................................................................................................................... IV
1.0 INTRODUCTION.......................................................................................................................................................................................................1
2.0
ENVIRONMENTAL MEASUREMENTS..................................................................................................................................................................3
2.1
WATER -LEVEL AND WATER -QUALITY MEASUREMENTS.............................................................................................................................................3
2.2
METEOROLOGICAL AND OCEANOGRAPHIC MEASUREMENTS.......................................................................................................................................5
2.3
BATHYMETRIC MEASUREMENTS...............................................................................................................................................................................9
3.0
HYDRODYNAMIC SIMULATIONS........................................................................................................................................................................10
3.1
NUMERICAL MODELS.............................................................................................................................................................................................10
3.1.1 Environmental Fluid Dynamics Code(EFDC) ...........................................................................................................................................11
3.1.2 Water Quality Analysis Simulation Program (WASP) ............................................................................................................................11
3.2
AERIAL PHOTOGRAPHS..........................................................................................................................................................................................11
3.3
GRID AND BATHYMETRY.........................................................................................................................................................................................13
3.4
BOUNDARY CONDITIONS........................................................................................................................................................................................14
3.5
CALIBRATION AND VERIFICATION............................................................................................................................................................................15
3.6
FLUSHING ASSESSMENT........................................................................................................................................................................................15
3.7
DISSOLVED OXYGEN ASSESSMENT.........................................................................................................................................................................16
3.8
ASSUMPTIONS AND LIMITATIONS...........................................................................................................................................................................16
4.0 REFERENCES..........................................................................................................................................................................................................17
APPENDIX: PHOTOGRAPHS.................................................................................................................................................................................................19
.ist of Tables
Table 1. Measured depth at water -level and water -quality measurement stations on July 20, 2021 around 14:00 coordinated universal time
(UTC) near low tide..................................................................................................................................................................................................................4
Table 2. Amplitude, phase, and speed of tidal constituents at Wrightsville Beach [United States National Oceanic and Atmospheric
Administration (NOAA) station 86581631, about 80 kilometers southwest of Bogue Inlet; and at Atlantic Beach (NOAA station 8656590), about
40 kilometers east of Bogue Inlet..........................................................................................................................................................................................6
Table 3. Datum conversions in meters at Wrightsville Beach [United States National Oceanic and Atmospheric Administration (NOAA)
station 86581631, about 80 kilometers southwest of Bogue Inlet; and at Atlantic Beach (NOAA station 8656590), about 40 kilometers east of
BogueInlet................................................................................................................................................................................................................................8
Table 4. Dissolved oxygen, salinity, and temperature statistics at North Carolina ambient water -quality gage on the White Oak River at State
Road 1442 near Stella (station P6400000)............................................................................................................................................................................14
At of Figures
Figure 1. Amphitheater Road Marina on White Oak River near Peletier, Carteret County, North Carolina on United States Geological Survey
NationalMap............................................................................................................................................................................................................................1
Figure 2. Amphitheater Road Marina on White Oak River near Peletier, Carteret County, North Carolina (A) on United States Geological
Survey National Map with contours of equal elevation (brown polylines) on a five-foot contour interval, and (B) on an April 28, 2020 aerial
ATM I CONS EL I

Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
Amphitheater Road Marina July 23, 2021
photograph by Maxar with discrete (blue diamonds) and continuous (yellow circles) constituent measurement locations. Stations discrete-
02 and continuous-02 are coincident...................................................................................................................................................................................2
Figure 3. Proposed Amphitheater Road Marina (red circle), subbasins (green polygons) that constitute the White Oak River watershed (dark
green polygons: United States Geological Survey hydrologic unit code 10; light green polygons: United States Geological Survey hydrologic
unit code 12), Intracoastal Waterway, and Bogue Inlet; Onslow, Jones, Craven, and Carteret Counties North Carolina on the United States
GeologicalSurvey National Map...........................................................................................................................................................................................5
Figure 4. Predicted water -surface elevation time series from the United States National Oceanic and Atmospheric Administration, in meters
above mean lower low water at Bogue Inlet, North Carolina...........................................................................................................................................7
Figure 5. United States National Oceanic and Atmospheric Administration (NOAA) measured wind speed time series and measured wind
direction time series at (A) Wrightsville Beach (NOAA station 8658163), and (B) Beaufort (NOAA station 8656483) ................................................9
Figure 6. Digital elevation models of topographic and bathymetric elevations in meters above the North American Vertical Datum of 1988
(NAVD88) over the United States Geological Survey National Map...............................................................................................................................10
Figure 7. White Oak River at (A) the North Carolina Highway 1442 (Stella Road) bridge between Silverdale and Stella, and North Carolina
Ambient water -quality gage on the White Oak River at North Carolina Highway 1442 near Stella (station P6400000); and (B) the North
Carolina Highway 24 (Corbett Avenue) bridge between Swansboro and Cedar Point, over April 28, 2020 aerial photographs by Maxar.......... 12
Figure 8. Aerial photographs of the confluence of the unnamed tributary to White Oak River and the White Oak River, which show a dredged
channel on (A) February 28, 2006; (B) December 31, 2011; and (C) February 19, 2017. The 2006 photograph is by the United States Department
of Agriculture Farm Service Agency and the United States Geological Survey...........................................................................................................13
List of Photographs
Photograph 1. July 2021 Dirt2Dreams photograph of station continuous-02 in the unnamed tributary to the White Oak River near Hancock
Point, looking southwest toward the confluence of the unnamed tributary with the White Oak River.....................................................................20
Photograph 2. July 2021 Dirt2Dreams photograph of station continuous-01 in the White Oak River near Hancock Point, looking southwest
fromthe eastern riverbank...................................................................................................................................................................................................20
Photograph 3. July 20, 2021 Land Management Group photograph of station continuous-02 in the unnamed tributary to the White Oak River
near Hancock Point, looking southwest toward the confluence of the unnamed tributary with the White Oak River...........................................21
Photograph 4. July 20, 2021 Land Management Group photograph of station discrete-04 in the White Oak River near Hancock Point, looking
southfrom the eastern riverbank........................................................................................................................................................................................21
Photograph 5. July 20, 2021 Land Management Group photograph of station continuous-01 in the White Oak River near Hancock Point,
looking east toward the eastern riverbank.........................................................................................................................................................................22
Photograph 6. July 20, 2021 Land Management Group photograph of station continuous-02 in the unnamed tributary to the White Oak River
near Hancock Point, looking northeast from the confluence of the unnamed tributary to the White Oak River with the White Oak River,
towardthe unnamed tributary..............................................................................................................................................................................................22
Photograph 7. July 20, 2021 Land Management Group photograph near station continuous-02 in the unnamed tributary to the White Oak
River near Hancock Point, looking southeast....................................................................................................................................................................23
Photograph 8. July 20, 2021 Land Management Group photograph near station discrete-02 in the unnamed tributary to the White Oak River
near Hancock Point, looking southeast..............................................................................................................................................................................23
Photograph 9. July 20, 2021 Land Management Group photograph of station continuous-02 in the unnamed tributary to the White Oak River
near Hancock Point, looking southwest toward the confluence of the unnamed tributary with the White Oak River...........................................24
Photograph 10. July 20, 2021 Land Management Group photograph of station discrete-03 in the unnamed tributary to the White Oak River
near Hancock Point, looking northeast...............................................................................................................................................................................24
ATM I ENGINEERING III

Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
Amphitheater Road Marina
Acronyms and Abbreviations
ATM
Applied Technology & Management, Inc.
DEQ
North Carolina Department of Environmental Quality
EDT
eastern daylight time (UTC =EDT +4hours)
EST
eastern standard time (UTC = EST + 5 hours)
EFDC
Environmental Fluid Dynamics Code
Esri
Environmental Systems Research Institute
km
kilometer
km2
square kilometer
LMG
Land Management Group, Inc.
MSL
mean sea level
NAVD88
North American Vertical Datum of 1988
NCDENR
North Carolina Department of Environment and Natural Resources
NOAA
United States National Oceanic and Atmospheric Administration
USEPA
United States Environmental Protection Agency
USGS
United States Geological Survey
UTC
coordinated universal time
UTM
Universal Transverse Mercator
WASP
Water Quality Analysis Simulation Program
Notes
Plan measurement units are metric. Convert from metric units to English units with the following conversion factors:
MeasurementType Multiply
By To Calculate
Length
meter(m)
3.281
foot(ft)
kilometer (km)
0.6214
mile (mi)
Area square kilometer (km2)
0.3861 square mile (mi2)
Cover art is an aerial photograph of White Oak River, North Carolina.
July 23, 2021
Applied Technology & Management, Inc. (ATM) performed the work described in this plan under ATM project number 21-3667; and
a work consent document executed by Brian K. Byrd, Manager, Dirt2Dreams, LLC, on June 16, 2021.
In this plan, ATM may have used standardized text from other ATM publications to describe general concepts, without explicit
attribution to these other ATM publications.
ATM I ENGINEERING iv

Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
Amphitheater Road Marina
1.0 Introduction
Dirt2Dreams, LLC hired Applied Technology &
Management, Inc. (ATM) to monitor the
environment and simulate flushing and dissolved
oxygen concentration near the proposed
Amphitheater Road Marina on the White Oak River
near Peletier, in Carteret County, North Carolina
(figure 1 and figure 2). Land Management Group,
Inc. (LMG) is assisting ATM with this work.
Dirt2Dreams propose to construct a marina in an
unnamed tributary to the White Oak River, on the
eastern side of the river south of Hancock Point.
Dirt2Dreams may also construct marina
infrastructure in the White Oak River, between the
unnamed tributary and a point about 300 meters (m)
southeast of the unnamed tributary.
The State of North Carolina, Department of
Environmental Quality (DEQ) permit marina
construction to address ecosystem concerns related
to environmental quality [North Carolina Department
of Environment and Natural Resources, (NCDENR)
2011]. The State of North Carolina created DEQ from
NCDENR in 2015. DEQ suggest that the permit
process begin with an environmental monitoring
and hydrodynamic simulation plan. The objective of
the plan is to obtain concurrence from the DEQ on
monitoring and simulation approaches.
77"15'W
77°10'W
0 5 10 Kilometers
t I I
0 2 4 6 Miles
77'5'W
July 23, 2021
The objective of this planning document is to
describe planned environmental monitoring (section
2) and describe planned hydrodynamic and water -
quality simulations (section 3). Environmental
monitoring includes water -level monitoring, water -
quality constituent monitoring, and atmospheric
monitoring. ATM proposes to use environmental
measurements to refine and calibrate a
hydrodynamic simulations of circulation, and
constituent transport simulations of dissolved
oxygen concentration and salinity in the unnamed
tributary to the White Oak River near Hancock Point
and in the White Oak River. Dirt2Dreams will use the
hydrodynamic simulation (!) to refine the marina
design, (2) to ensure that constituents in the
proposed marina will be flushed to the White Oak
River, and (3) to ensure that the proposed marina
will not decrease contemporary dissolved oxygen
concentrations in the unnamed tributary or in the
river.
Dirt2Dreams submit this plan —and will submit
environmental monitoring, associated flushing
simulations, and associated water -quality
simulations —in support of a permit request from
the State of North Carolina to construct the
proposed Amphitheater Road Marina.
Figure L Amphitheater Road Marina on White Oak River near Pe%tier, Carteret County, North
Carolina on United States Geological Survey National Map.
oLSIGN
ENGINEERING
CONSULTING

Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
Amphitheater Road Marina
(A)
(B)
77°6'40"W 77°6'30"W 77°6'20"W 77°6'10"W 77°6'W 77°5'50"W
77°6'40"W 77°6'30"W 77"6'20"W 77°6'10"W 77°6'W 77°5'50"W
0 500 1;000 Meters
0 1,000 2,000 Fast
Figure 2. Amphitheater Road Marina on White Oak River near Pe%tier, Carteret County, North Carolina (A) on United
States Geological Survey National Map with contours of equal elevation (brown polylines) on a five-foot contour
interval, and (B) on an April28, 2020 aerial photograph by Maxar with discrete (blue diamonds) and continuous
(yellow circles) constituent measurement locations. Stations discrete-02 and continuous-02 are not coincident.
Station continuous-02 is on a pile and station discrete-02 is in the channel a few meters southeast of the pile.
DESIGN
ENGINEERING
CONSULTING
July 23, 2021

Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
Amphitheater Road Marina
2.0 Environmental Measurements
LMG and a surveyor will measure environmental
parameters. ATM proposes to populate a database
with environmental measurements. The database
will include LMG's measurement of water level in
the unnamed tributary to the White Oak River near
Hancock Point and in the White Oak River (section
2.1); LMG measurement of selected water -quality
constituents in the unnamed tributary and in the
river (section 2.1); measurements of selected
meteorological and oceanographic constituents by
others (section 2.2); and bathymetric measurements
by a surveyor (section 2.3).
2.1 Water -Level and Water -quality
Measurements
DEQ (NCDENR, 2011) require that existing water
quality be assessed, prior to and in support of
numerical simulation of existing and proposed water
quality. DEQ (NCDENR, 2011) do not reference
specific protocols or standard operating procedures
related to water -level or water -quality
measurements. Consequently, ATM and LMG
reasonably assume that DEQ (NCDENR, 2011) is a
full and inclusive description of specific protocols or
standard operating procedures related to water -level
and water -quality measurements associated with
State of North Carolina requirements related to
proposed marina construction. ATM and LMG will
revise this plan in response to additional guidance
from the State of North Carolina related to proposed
marina construction. One objective of the present
plan is to detail LMG protocols and operating
procedures to measure water level and water
quality.
DEQ require the following six measurements:
• Water level
• Dissolved oxygen concentration
• Temperature
• pH
• Conductivity
• Salinity
LMG proposes to measure water level, dissolved
oxygen concentration, temperature, pH, and
conductivity at six locations (figure 2B). ATM
proposes to calculate salinity from temperature and
conductivity measurements. LMG proposes to
measure these constituents continuously at station
continuous-01 in the White Oak River and at station
continuous-02 in the unnamed tributary to the White
FNG I V F FRI I.G
July 23, 2021
Oak River near Hancock Point (figure 213). Station
locations in figure 2B are preliminary and may
change subsequent to additional field investigations
to determine deployment feasibility. Stations
discrete-02 and continuous-02 are not coincident:
station continuous-02 is on a pile and station
discrete-02 is in the channel several meters
southeast of the pile.
LMG proposes to measure constituents with YSI
EXO2 sondes (YSI, 2020) strapped to piles at stations
continuous-01 and continuous-02. LMG measured
depth at continuous and discrete stations at about
14:00 coordinated universal time (UTC) on July 20,
2021 (about 10 AM Eastern Daylight Time on July
20) (table 1). [Time in this report is uniformly
published in 24-hour format, such that 1:00 PM in 12-
hour format is equivalent to 13:00 in 24-hour format,
and AM and PM are not published. Time in this
report is uniformly referenced to UTC. UTC is four
hours ahead of eastern daylight time (EDT) and five
hours ahead of eastern standard time (EST). UTC is
also known as Greenwich mean time.] NOAA
(2021 b) predicted the lowest low tide on July 20 at
14:27 UTC 0.07 m below mean lower -low water
(MLLW) at Bogue Inlet —about nine kilometers south
of Hancock Point. NOAA (2021b) also predicted a low
tide on July 20 at 02:43 UTC 0.06 m above MLLW at
Bogue Inlet. LMG proposes to fix sondes to piles at
continuous stations. LMG proposes to mount the
sonde at station continuous-01, such that the
pressure transducer and other measurement
instruments connected to the sonde are 0.3 m (about
1 foot) below MLLW and always wet. LMG proposes
to measure these constituents 0.5 m above the bed
at low tide, at station continuous-01. LMG proposes
to mount the sonde at station continuous-02, such
that the pressure transducer and other measurement
instruments connected to the sonde are 0.15 m
(about 6 inches) below MLLW and always wet. LMG
proposes to measure these constituents 0.15 m
above the bed at low tide, at station continuous-02.

Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
Amphitheater Road Marina
Table 1. Measured depth at water -
level and water -quality
measurement stations on July20,
2021 around 14:99 coordinated
universal time (UTC) near low tide.
Continuous-01 0.853
Continuous-02
0.366
Discrete-01
_ 1.219
Discrete-02
0.366
Discrete-03
1.067
Discrete-04
0.427
Note: m is meter
In water depths greater than three feet, DEQ require
surface, mid -column, and bottom measurements of
dissolved oxygen concentration, temperature, pH,
and conductivity. LMG proposes to measure vertical
profiles of these constituents with the sonde from
station continuous-01 in the White Oak River at
station continuous-01, or with the sonde from
station continuous-02 in the unnamed tributary to
the White Oak River near Hancock Point at station
continuous-02. While LMG measures these vertical
profiles, the sondes will be used to measure the
profile and will not be used to measure constituents
at the station. After LMG measures these vertical
profiles, LMG will return the sonde to the station, to
measure constituents at a time interval of five to
fifteen minutes. In water depths greater than three
feet, LMG proposes to measure vertical profiles of
these constituents every 0.3 m (about 1 foot), such
that LMG will measure constituents 0.3 m, 0.6 m,
and 0.9 m above the bed in water that is 1 m deep
and 0.3 m, 0.6 m, 0.9 m, 1.2 m, 1.5 m, and 1.8 m
above the bed in water that is 2 m deep.
In water depths less than three feet, DEQ require
surface and bottom measurements of dissolved
oxygen concentration, temperature, pH, and
conductivity. If water depth is less than 0.3 m, LMG
propose to measure constituents in the shallow
water column. If water depth is between 0.3 m and
0.7 m, LMG propose to measure constituents 0.3 m
above the bed and 0.1 m below the water surface. I
water depth is between 0.7 m and 1.0 m, LMG
propose to measure constituents 0.3 m and 0.6 m
above the bed, and 0.1 m below the water surface.
ATM proposes to calculate a vertical salinity profiles
from vertical conductivity and temperature profiles.
DEQ require measurements during the critical,
worst -case season of marina operation —which is
summer between June and September. LMG
proposes to measure constituents for 30 days
July 23, 2021
beginning in August 2021 and concluding before
September 30, 2021.
In tidal systems, DEQ require measurements at slack
tide. Slack tide occurs when velocity in the water
column is zero, at high and low tide. LMG proposes
to measure or calculate constituents at discrete
stations over half a tidal cycle at low tide and at high
tide, from low tide to high tide or from high tide to
low tide. LMG proposes to measure or calculate
constituents at continuous stations, once every five
to fifteen minutes for 30 days, such that LMG will
measure constituents at slack tides, but also during
other parts of the tidal cycle at continuous stations.
LMG proposes to also measure the following 11
constituents discretely at stations discrete-01 and
discrete-04 in the White Oak River, and at stations
discrete-02 and discrete-03 in the unnamed tributary
(figure 213):
• Total nitrogen concentration
• Ammonia concentration
• Nitrate -nitrite concentration
• Total Kjeldhal nitrogen concentration
• Total phosphorus concentration
• Orthophosphate concentration
• Chlorophyll aconcentration
• 5-day biochemical oxygen demand
• Carbon concentration
• Total suspended solids concentration
• Color
LMG proposes to measure these constituents from a
depth of 0.1 m below the water surface, in
conformance with DEQ (2017). LMG propose to draw
water from a depth of 0.1 m below the water surface
into sample bottles. LMG proposes to transport
water samples using defined storage protocols to
Pace Analytical Services, LLC in Wilmington, North
Carolina, 120 km southeast of the proposed
Amphitheater Road Marina. LMG proposes to report
Pace Analytical Services constituent measurements.
DEQ require measurements once every two weeks.
LMG proposes to measure constituents at stations
continuous-01 and continuous-02 every five to
fifteen minutes for 30 days. LMG proposes to
measure constituents at stations discrete-01,
discrete-02, discrete-03, and discrete-04 every 15
days, for a total of two measurements (low -tide and
high -tide) at each discrete station, on each
measurement day. LMG proposes to measure or
calculate 11 constituents, twice, on three
measurement days at four discrete stations for a
total of 264 measurements (11 measurements x 2
❑r i i nn "'.INFFRINc 4

Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
Amphitheater Road Marina
measurements per day x 3 measurement days x 4
discrete stations), over the 30-day environmental
measurement period in August 2021.
LMG visited the proposed Amphitheater Road
Marina site on the unnamed tributary to White Oak
River in early July (see photograph 1 and
photograph 2 in the appendix), and on July 20 ( see
photograph 3 through photograph 10).
Field work may involve revision to protocols or
strategies during field measurement activities. LMG
may revise the proposed measurement activities
described in this section, based on additional
information determined in the field, during
measurement activities. Minor or trivial revisions to
proposed measurement activities that do not
influence DEQ regulatory determinations will be
detailed in the subsequent report. For example, if
LMG move a proposed discrete measurement
station tens of meters, this revision will be detailed
in the subsequent report. LMG will discuss major or
non -trivial revisions with DEQ prior to acting on the
revision. For example, if LMG removes a proposed
measurement station from the set of stations, LMG
will first discuss this with DEQ.
July 23, 2021
2.2 Meteorological and Oceanographic
Measurements
DEQ (NCDENR, 2011) require wind speed
measurement, wind direction measurement, and
rain depth measurement.
ATM proposes to force flushing simulations with
tide, wind, Coriolis force, and freshwater and saline
water inflows. During ebb tide, White Oak River
drains to the Intracoastal Waterway near Bogue Inlet
(figure 3). During ebb tide, the Intracoastal Waterway
discharges to the Atlantic Ocean through Bogue
Inlet. The National Oceanic and Atmospheric
Administration (NOAA) measure water -surface
elevation at Wrightsville Beach (NOAA station
8658163) (NOAA, 2021d), about 80 kilometers (km)
southwest of Bogue Inlet; and at Atlantic Beach
(NOAA station 8656590) (NOAA, 2021 a), about 40 km
east of Bogue Inlet. NOAA calculate tidal harmonics
from measurements at Wrightsville Beach and
Atlantic Beach (table 2). NOAA predict tidal elevation
at Bogue Inlet (NOAA, 2021b) from calculated
harmonics at Wrightsville Beach and Atlantic Beach
(figure 4). The principal lunar semidiurnal M2
constituent dominated the tidal signal with a
0.548-m amplitude at Wrightsville Beach and a
0.593-m amplitude at Atlantic Beach. Amplitudes of
36 additional constituents at each station were less
than 0.15 m each.
77`35IN 77'30'W 77'25'W 77'2C N 77115% 77'10•w 77°5'W 77°0'W 76'55'W 7R150'Vv
0 20 40 Kil—tem
I I I
D 10 20 Miles
Figure 3. Proposed Amphitheater Road Marina (red circle), subbasins (green
polygons) that constitute the White Oak River watershed (dark green polygons:
United States Geological Survey hydrologic unit code 10,• light green polygons:
United States Geological Survey hydrologic unit code 12), Intracoastal Waterway,
and Bogue Inlet- Onslow, Jones, Craven, and Carteret Counties North Carolina on
the United States Geological Survey National Map.
DESIGN
ENGINEERING
CONSULTING

Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
Amphitheater Road Marina
July 23, 2021
Tab/e 2. Amplitude, phase, and speed of tidal constituents at Wrightsville Beach [United States National Oceanic andAtmospheric
Administration (NOAA) station 8658163] about 80 kilometers southwest of Bogue Inlet- and atAdantic Beach (NOAA station 8656590),
about 40 kilometers east of Bogue Inlet.
Wrightsville
NOAA 8658163 NOAA 8656590
CONSTITUENT DESCRIPTION
Principal lunar semidiurnal
CONSTITUENT
MZ
meters degrees per
�m hour
0.548 350.8 1 0.593 353.1 28.9841040
Principal solar semidiurnal
SZ
0.095
10.9
0.103
14.1
30.0000000
Larger lunar elliptic semidiurnal
NZ
0.130
329.5
0.142
333.7
28.4397300
Lunar diurnal
Kr
0.093
185.4
0.096
186.4
15.0410690
Shallow water overtides of
principal lunar
Lunar diurnal
Shallow water overtides of
principal lunar
M4
0.005
236.2
0.011
267.7
57.9682100
Or
0.073
190.8
0.069
192.6
13.9430350
M6
0.006
254.3
0.006
25.4
86.9523200
Shallow water terdiurnal
MK3
0.000
0.0
0.000
0.0
44.0251730
Shallow water overtides of
principal solar
S4
0.010
265.9
0.011
307.4
60.0000000
Shallow water quarter diurnal
MN4
0.000
0.0
0.009
242.1
57.4238320
Larger lunar evectional
NUZ
0.025
330.8
0.027
331.2
28.5125830
Shallow water overtides of
principal solar
S6
0.000
0.0
0.000
0.0
90.0000000
Variational
MUZ
0.020
336.6
0.021
338.6
27.9682080
Lunar elliptical semidiurnal
second -order
2N2
0.016
310.2
0.000
0.0
27.8953550
Lunar diurnal
00,
0.005
201.0
0.000
0.0
16.1391010
Smaller lunar evectional
LAMZ
0.005
15.1
0.005
4.5
29.4556260
Solar diurnal
Sr
0.012
162.0
0.010
136.5
15.0000000
Smaller lunar elliptic diurnal
Mr
0.000
0.0
0.000
0.0
14.4966940
Smaller lunar elliptic diurnal
Jr
0.006
192.1
0.006
177.7
15.5854435
Lunar monthly
MM
0.000
0.0
0.000
0.0
0.5443747
Solar semiannual
SSA
0.036
57.1
0.059
50.3
0.0821373
Solar annual
SA
0.066
166.0
0.108
165.0
0.0410686
Lunisolar synodic fortnightly
MSF
0.000
0.0
0.000
0.0
1.0158958
Lunisolar fortnightly I
MF
0.000
0.0
0.000
0.0
1.0980331
Larger lunar evectional diurnal
RHO
0.003
170.1
0.005
175.3
13.4715150
Larger lunar elliptic diurnal
0.7
0.015
184.2
0.015
186.1
13.3986610
Larger solar elliptic
TZ
0.009
359.5
0.010
355.7
29.9589330
Smaller solar elliptic
RZ
0.004
237.3
0.000
0.0
30.0410670
Larger elliptic diurnal
201
0.000
0.0
0.000
0.0
12.8542860
Solar diurnal
Pr
0.032
187.9
0.033
187.5
14.9589310
Shallow water semidiurnal
2SM2
0.003
6.7
0.000
0.0
31.0158960
Lunarterdiurnal
M3
0.008
14.0
0.011
25.1
43.4761600
Smaller lunar elliptic semidiurnal
LZ
0.014
20.1
0.019
358.3
29.5284790
Shallow water terdiurnal
2MK3
0.004
50.0
0.000
0.0
42.9271400
Lunisolar semidiurnal
KZ
0.024
16.1
0.027
13.2
30.0821380
Shallow water eighth diurnal
M6
0.001
169.3
0.000
0.0
115.9364200
Shallow water quarter diurnal
MS4
0.011
113.2
0.009
154.3
58.9841040
Notes: Phase in degrees is referenced to the prime meridian at longitude 0° through Greenwich, England.
Speed in degrees per hour is the rate of change of the constituent phase.
oLSICN
ENGINEERING
CONSULTING

Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
Amphitheater Road Marina
1.0
VI
LU
W
W
0.8
z U,
- w
za
O
Q ?; 0.6
w
J
W
W W
U �; 0.4
LLo
Z) z
Ln¢
w
W 2E 0.2
Q w
'O
m
o a 0.0
U_
w
a
-0.2 —
07/06 07/13 07120 07/27
MONTH/DAY
08/03
July 23, 2021
Figure 4. Predicted water -surface elevation time series from the United States National Oceanic and Atmospheric Administration, in meters
above mean lowerlow water atBogue Inlet, North Carolina.
NOAA (2013) published datum conversion and tidal
harmonics for the tidal epoch from 1983 to 2001. The
mean tide range at Wrightsville Beach during the
epoch was 1.214 m (table 3); the mean tide range at
Atlantic Beach was 1.113 m. The highest
astronomical tide elevation at Wrightsville Beach
during the epoch was 1.187 m above mean sea level
(MSL) in October 1993; the lowest astronomical tide
I NSATM COT
elevation at Wrightsville Beach was 1.059 m below
MSL in February 1997. If necessary, ATM proposes
to convert between MSL, mean lower -low water, and
the North American Vertical Datum of 1988 by
developing a spatially -average datum conversion
from datum conversions at Wrightsville Beach and
Atlantic Beach to convert elevation information.

Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
Amphitheater Road Marina
July 23, 2021
Table 3. Datum conversions in meters at Wrightsville Beach [United States National 0ceanic andAtmospheric Administration (NOAA)
station 8658163] about80kilometers southwestof Bogue Inlet- and atAtlantic Beach (NOAA station 8656590), about40kilometers eastof
Bogue Inlet.
Description
Depth
Wrightsville
NOAA
NOAA 8656590
Mean Higher -High Water
MHHW
0.709
0.654
Mean High Water
MHW
0.604
0.550
Mean Tide Level
MTL
-0.003
-0.006
Mean Sea Level
MSL
0.000
0.000
Mean Diurnal Tide Level
DTL
0.025
0.022
Mean Low Water
MLW
-0.610
-0.563
Mean Lower -Low Water
MLLW
-0.658
-0.610
North American Vertical Datum of 1988
NAVD88
0.183
0.147
Station Datum
STND
-6.396
-2.215
Great Diurnal Range
6T
1.367
1.263
Mean Range of Tide
MN
1.214
1.113
Mean Diurnal High Water Inequality
DHQ
0.105
0.103
Mean Diurnal Low Water Inequality
DLQ
0.048
0.047
Greenwich High Water Interval (in hours)
HWI
12.32
12.13
Greenwich Low Water Interval (in hours)
LWI
6.160
5.980
Highest Observed Tide
Max Tide
1.943
Highest Observed Tide Date & Time
Max Tide Date & Time
9/14/201814:54
Lowest Observed Tide
Min Tide
-1.464
Lowest Observed Tide Date & Time
Min Tide Date & Time
1/8/2009 3:00
Highest Astronomical Tide
HAT
1.187
HAT Date and Time
HAT Date & Time
10/16/199312:24
Lowest Astronomical Tide
LAT
-1.059
LAT Date and Time
LAT Date & Time
2/8/1997 6:24
Notes: The absolute value of negative depths above MSL are depths below MSL
-- is elevation or time not available
NOAA measure wind speed and wind direction at
Wrightsville Beach (figure 5A) and Beaufort (NOAA
station 8656483) (NOAA, 2021d) (figure 5A)-about
40 km east of Bogue Inlet. ATM proposes to force
the simulation with wind speed and direction at
Wrightsville Beach (similar to figure 5, but for
August 2021 environmental measurement period).
Less reliable wind velocity stations and wind velocity
predictions also exist for Bogue Inlet and the White
Oak River.
oLSIGN
ENGINEERING
CONSULTING
ATM proposes to initially force the simulation with
synthesized wind speed and wind direction from
Wrightsville Beach and Beaufort. If comparison of
measured water -surface elevation and simulated
water -surface elevation suggest that wind speed or
wind direction on the White Oak River differ from the
synthesized speed or direction, ATM proposes to
adjust the synthesis accordingly. If ATM determine
that additional wind speed or wind direction
measurements are necessary, ATM proposes to use
other wind velocity stations.

Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
Amphitheater Road Marina July 23, 2021
(AI z,
I J n ,o,.,� 12 J n HJ ' Ju' s.Ju" .1.24..., 11 J." 20 Ju' 31 Ju ,uI Jul
(B)
Figure 5. United States National Oceanic and Atmospheric Administration (NOAA) measured wind speed time series and measured wind
direction time series at (A) Wrightsville Beach (NOAA station 8658163), and (B) Beaufort (NOAA station 8656483).
The United States Geological Survey (USGS)
to generate synthetic freshwater inflow hydrographs
measure rain depth on the Cape Fear River at Lock 1
at selected locations on the simulation domain
near Kelly (USGS station 02105769), about 110 km
boundary.
southwest of the proposed Amphitheater Road
Marina. ATM did not locate a rain gage with a
2.3 Bathymetric Measurements
published rain depth record closer to the White Oak
USGS (2020) published elevations in Onslow and
River. ATM proposes to continue to attempt to locate
Carteret Counties (figure 6).
a published rain depth record closer to the White
Oak River than the Cape Fear gage. If ATM is not
Dirt2Dreams proposes to hire a subcontractor to The
able to find a closer rain gage, LMG may measure
Cullipher Group, PA to measure bathymetric
rain depth during the August environmental
elevations in the unnamed tributary to White Oak
measurement period, for use in creating freshwater
River.
inflow hydrographs at simulation domain
ATM proposes to inspect transitions between
boundaries.
bathymetry to determine if elevation discontinuities
USGS do not measure flow rate at any location in
exist. If elevation discontinuities exist in bathymetry,
the White Oak River watershed. ATM was not able to
ATM proposes to smooth these discontinuities with
locate a flow rate records published by other
spatial smoothing and spatial interpolation
organizations in the White Oak River watershed.
algorithms.
ATM proposes to use simple rainfall -runoff models
A/ I' M
I ENGINEERING 9

Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
Amphitheater Road Marina
77°15'W
77°10'W
77°5' W
0 5 10 Kilometers Elevation, in meters above NAVD88
I 113.4m
0 3 6 Miles rr
-7.9 m
77°0'W
Figure 6. Digital elevation model of topographic and bathymetric elevations in meters above the North American Vertical
Datum of 1988 (NAVD88) over the United States Geological Survey (2020) National Map.
3.0 Hydrodynamic Simulations
A semi -enclosed water body connected to a larger
water body flushes pollutants or other constituents
to the larger water body when water that flows out
of or through the enclosed body causes the mass of
the pollutant or constituent in the enclosed body to
decrease. For example, a harbour connected to the
ocean flushes a mass of constituent to the ocean
when tide forces the constituent to flow from the
harbour to the ocean. Flushing reduces the potential
for stagnant water in the harbour, decreases the
residence time of constituents in the harbour,
enhances biological productivity in the harbour, and
reduces the accumulation in toxic pollutants in
bottom sediments in the harbour. In constructed
waterbodies—such as a marina— the DEQ
(NCDENR, 2011) cite an EPA (1985) recommendation
that more than 85% of the mass of a constituent in
the water body must flush to the larger, connected
water body within 24 hours.
ATM proposes to simulate flushing, constituent
transport, and dissolved oxygen concentration,
temperature, and salinity. In the present plan
section, ATM describes proposed use of the
following items: numerical models (section 3.1),
July 23, 2021
aerial photographs on which ATM will base
simulations (section 3.2), the simulation grid and
bathymetry (section 3.3), simulation boundary
conditions (section 3.4), calibration and verification
of the simulation (section 3.5), flushing assessment
(section 3.6), dissolved oxygen assessment (section
3.7), and assumptions and limitations (section 3.8).
3.1 Numerical Models
DEQ (NCDENR, 2011) require assessment of the
"flushing characteristics of the proposed marina"
and calculation of "24-hour average dissolved
oxygen concentrations both inside the marina and in
adjacent ambient waters."
ATM proposes to use numerical models to simulate
circulation and the time to flush a conservative
constituent from the proposed Amphitheater Road
Marina to the White Oak River; and to calculate
dissolved oxygen concentration time series inside
the proposed marina and in adjacent, ambient
waters, in the river. ATM will characterize water
circulation in the marina, and flushing of the marina
to the river, forced by tide, wind, and density
gradients.
❑F I ' nn I FNG1'JFFR1NG 10

Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
Amphitheater Road Marina
ATM proposes to use the United States
Environmental Protection Agency (USEPA)
Environmental Fluid Dynamics Code (EFDC) to
simulate hydrodynamics and flushing of a
conservative constituent (USEPA, 2019). ATM also
propose to use USEPA Water Quality Analysis
Simulation Program (WASP) to simulate dissolved
oxygen concentrations (USEPA, 2017).
DEQ require that hydrodynamic, flushing, and water -
quality simulation be done with open source
models. EFDC and WASP are open source models,
published and documented by the USEPA. EFDC and
WASP are industry -standard tools for simulation of
hydrodynamics in estuarine systems, and for
simulation of water -quality transport, respectively.
ATM further describes EFDC in section 3.1.1 and
WASP in section 3.1.2.
3.1.1 Environmental Fluid Dynamics Code
(EFDC)
EFDC is a general-purpose hydrodynamic model,
typically used to simulate two-dimensional and
three-dimensional flow, circulation, transport, and
biogeochemical processes in surface water systems,
including rivers, lakes, estuaries, reservoirs,
wetlands, and nearshore-scale to continental -shelf -
scale coastal systems. EFDC is open -source software
in the public domain, currently supported by the
USEPA Office of Research and Development.
EFDC solves three-dimensional, hydrostatic, free -
surface, turbulent -averaged equations of motion for
a variable -density fluid. Dynamically coupled
transport equations for turbulent kinetic energy,
turbulent length scale, salinity, and temperature are
also solved. Two, turbulent transport equations
implement the Mellor -Yamada level 2.5 turbulence
closure scheme. EFDC uses a grid with a stretched or
sigma vertical geometry; and curvilinear,
orthogonal, horizontal geometry.
EFDC solves the equations of motion with a second -
order accurate spatial finite -difference scheme on a
staggered or C grid. Time integration employs a
second -order accurate three -time -level, finite -
difference scheme with an internal -external mode
splitting procedure to separate the internal shear or
baroclinic mode from the external free -surface
gravity wave or barotropic mode. The external mode
solution is semi -implicit and simultaneously
computes the two-dimensional surface elevation
field by a preconditioned conjugate gradient
procedure. The external solution is completed with
July 23, 2021
the calculation of depth -average barotropic
velocities using the most -recently calculated surface
elevation gradient. The model's semi -implicit
external solution allows large time steps constrained
by stability criteria of either the explicit central -
difference scheme, or by a higher -order upwind
advection scheme used for nonlinear accelerations.
Horizontal boundary conditions for the external
mode solution include options for simultaneously
specifying the surface elevation only, the
characteristic of an incoming wave, free radiation of
an outgoing wave, or the normal volumetric flux on
arbitrary parts of the boundary.
3.1.2 Water Quality Analysis Simulation
Program (WASP)
WASP is a general purpose water -quality model,
typically used to simulate concentrations of
constituents in waterbodies. WASP can simulate
water -quality in one-dimensional, two-dimensional,
and three-dimensional frameworks. WASP is open -
source software in the public domain, currently
supported by the USEPA Office of Research and
Development.
3.2 Aerial Photographs
ATM obtained an April 28, 2020 aerial photograph by
Maxar of White Oak River from the Environmental
Systems Research Institute (Esri) Worldlmagery
archive (for example, see base maps on figure 213,
figure 7, and figure 8). ATM will use shoreline
geometry from the April 2020 aerial photograph to
conform the curvilinear simulation grid to the
shoreline.
Aerial photographs show key physical features,
relevant to simulation. Specifically, the North
Carolina Highway 1442 (Stella Road) bridge over the
White Oak River between Silverdale and Stella
(figure 7A) constrains flow from the riverine part of
the White Oak River into the estuarine part of the
river. The North Carolina Highway 24 (Corbett
Avenue) bridge over the White Oak River between
Swansboro and Cedar Point (figure 713) constrains
flow from the estuarine part of the White Oak River
to the Intracoastal Waterway, near Bogue Inlet.
Dirt2Dreams proposes to construct Amphitheater
Road Marina in an unnamed tributary to the White
Oak River near Hancock Point. A channel existed in
this tributary in 2006 and 2011 (figure 8A and figure
813). The channel was less evident in 2017 (figure
8C).
❑Flinn FNGI'AFFRIhc 11

Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
Amphitheater Road Marina
(A)
(B)
77°9'30"W 77°9'0"W 77"8'30"W 77'8'0"W
0 500 1,000M.L—
I I I
0 1,000 2,000 Feet
77'8'0"W 77°7'30"W 77°7'Q'W 77 o'30"W 77'6'0'v! 77°5'30"W
0 500 1,000Metere
I I I
rrrrrT----1
0 1,000 2000 Feet
July 23, 2021
Figure 7. White Oak River at (A) the North Carolina Highway 1442 (Stella Road) bridge between Silverdale and Stella, and North Carolina
Ambient water -quality gage on the White Oak River at North Carolina Highway 1442 near Stella (station P6400000),• and (B) the North
Carolina Highway24 (Corbett Avenue) bridge between Swansboro and Cedar Point, overApril28, 2020 aerial photographs by Maxar.
A/I'M ICONSULTINGO 12

Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
Amphitheater Road Marina
(A)
(C)
(B)
July 23, 2021
Figure 8. Aeria/photographs of the confluence of the unnamed tributary to White Oak River and the White Oak River, which show a dredged
channel on (A) February28, 2006-,(B) December 31, 2011; • and (C) February 19, 2017 The 2006 photograph is by the United States Department
of Agriculture Farm Service Agency and the United States Geological Survey.
3.3 Grid and Bathymetry
ATM proposes to conform a curvilinear grid to the
shoreline on the April 2020 aerial photograph, in
zone 18-North of the Universal Transverse Mercator
(UTM) projection . The grid will be more resolved
near the proposed Amphitheater Road Marina, and
less resolved away from the proposed marina.
WASP is more challenged by three dimensional
simulation domains with relatively greater resolution
than with relatively lesser resolution. To manage this
challenge, ATM proposes to use a relatively coarse
grid away from the proposed marina ATM's
approach will not affect qualitative findings.
❑Flinn FNGd'AFFRIhc 13

Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
Amphitheater Road Marina
ATM proposes to interpolate bathymetric elevations
on the grid using elevations on NOAA digital
elevation models (NOAA, 2016; NOAA, 2019) (figure
6). A subcontractor to The Cullipher Group, PA
proposes to measure bathymetry in the unnamed
tributary to White Oak River. ATM proposes to use
this measured bathymetry in parts of the simulation
domain.
3.4 Boundary Conditions
ATM proposes to decompose NOAA's transient,
predicted water -surface elevation time series at
Bogue Inlet (similar to figure 4, but for August 2021
environmental measurement period) into harmonic
constituents. ATM then proposes to translate the
phase and amplitude of the Bogue Inlet signal to the
simulation domain boundary at North Carolina
Highway 24 by adjusting phase and amplitude of
constituents at Highway 24 until measured water -
surface elevations at the unnamed tributary to White
Oak River (figure 2B) match simulated water -surface
elevations. Highway 24 is four kilometers north of
Bogue Inlet (figure 3). ATM proposes to use a
facsimile of decomposed harmonics at Bogue Inlet
as an initial guess at Highway 24.
ATM proposes to use measured dissolved oxygen
concentration, salinity, and temperature at North
Carolina Ambient water -quality gage on the White
Oak River at North Carolina Highway 1442 near
Stella (station P6400000) (table 4 and figure 7A) to
generalize an initial water -quality boundary
conditions at Highway 1442. ATM has not found
dissolved oxygen concentration, salinity, or
temperature measurements at North Carolina
Highway 24, on the southern simulation domain
boundary. ATM will continue to search for dissolved
oxygen concentration, salinity, or temperature
measurements at or near Highway 24, in Bogue
Sound, or in the Intracoastal Waterway near Bogue
Inlet. If ATM are not able to find dissolved oxygen
concentration, salinity, or temperature
measurements, ATM proposes to use typical values
for coastal systems in North Carolina as an initial
boundary condition.
ATM proposes to adjust initial boundary conditions
until simulated dissolved oxygen concentration,
salinity, and temperature match measured dissolved
oxygen concentration, salinity, and temperature at
environmental measurement stations in and near
the unnamed tributary to White Oak Creek (figure
2B).
July 23, 2021
Table 4. Dissolved oxygen, salinity, and temperature statistics
at North Carolina ambient water-qualitygage on the White Oak
River at State Road 1442 near Stella (station P6400000).
Statistic
Number of
measurements
Dissolved
Oxygenp•
[mg/L1
52
pp
54
54
Exceedance Limit
less than
5
Exceedances
5
Minimum
4.4
0.05
5.5
loth Percentile
5.0 1
0.09 1
9.2
25th Percentile
5.7
1.26
13.2
50th Percentile
6.8
7.9
9.1
10.1
11.5
3.87
10.12
14.58
15.42
21.66
20.3
27.1
28.6
30.2
31.9
75th Percentile
85th Percentile
90th Percentile
Maximum
Note: mg/L is milligram per liter
-- is unit not applicable
At the upstream end of the proposed simulation
domain, about 520 square kilometers (km2) drain to
the White Oak River (figure 3) at the North Carolina
Highway 1442 (Stella Road) bridge over the river,
between Silverdale and Stella (figure 7A). At the
downstream end of the proposed simulation
domain, 708.15 kmz drain to the White Oak River
(figure 3) at North Carolina Highway 24 (Corbett
Avenue) bridge over the river, between Swansboro
and Cedar Point (figure 7B).
About three quarters of the freshwater inflow to the
proposed simulation domain is at the North Carolina
Highway 1442 bridge. ATM proposes to force the
simulation with freshwater inflow at the upstream
end of the simulation domain, at North Carolina
Highway 1442 bridge. About one quarter of the
freshwater inflow to the proposed simulation
domain is downstream of the highway 1442 bridge,
at the following tributaries to the White Oak River
(roughly arranged from upstream to downstream):
• Cales Creek
• Webb Creek
• Had not Creek
• Caleb Branch
• Hargetts Creek
• Godfry Branch
• Unnamed tributary near Rolling Hill Drive
• Holland Mill Creek
• Unnamed tributary at the proposed
Amphitheater Road Marina
• Stevens Creek
• Starkey Creek
ATM CONS T, 14

Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
Amphitheater Road Marina July 23, 2021
• Petttiford Creek simulated with calibrated simulations may not
• Dubling Creek
• Boathouse Creek
Webb Creek (about 15 km2), Cales Creek (about 5
km2), Hadnot Creek (46.24 km2), Holland Mill Creek
(about 17 km2), and Pettiford Creek (48.9 km2) drain
the largest areas of this remaining quarter of the
White Oak River watershed.
ATM proposes to estimate freshwater inflow with
the United States Department of Agriculture Natural
Resource Conservation Service (1986) runoff curve
number, in which a streamflow hydrograph is
generated as a function of land use, soil type, rainfall
depth, drainage area, and a time of concentration
that describes the duration between the peak of
rainfall and the peak of runoff.
DEQ require an assumed 1.5 grams sediment
oxygen demand per square meter per day unless
evidence supports a greater or lesser demand. ATM
proposes to assume 1.5 grams sediment oxygen
demand per square meter per day, or provide
evidence to support a different demand.
3.5 Calibration and Verification
ATM proposes to calibrate simulations by adjusting
simulation parameters and boundary conditions to
minimize the difference between simulated water -
surface elevation, velocity, salinity, temperature, and
dissolved oxygen concentration; and measured
water -surface elevation, velocity, salinity, and
dissolved oxygen concentration, respectively.
Calibrated simulations are generally preferred to
uncalibrated simulations because simulated water -
surface elevation, velocity, salinity, temperature, and
dissolved oxygen concentration that matches
measured water -surface elevation, velocity, salinity,
temperature, and dissolved oxygen concentration
are more reliable than simulated water -surface
elevation, velocity, salinity, temperature, and
dissolved oxygen concentration that have not been
compared with measured water -surface elevation,
velocity, salinity, temperature, and dissolved oxygen
concentration.
ATM proposes to verify simulations by comparing
water -surface elevation, velocity, salinity,
temperature, and dissolved oxygen concentration
with measured water -surface elevation, velocity,
salinity, temperature, and dissolved oxygen
concentration that were not used in calibration.
Water -surface elevation, velocity, salinity,
temperature, and dissolved oxygen concentration
compare well with measured water -surface
elevation, velocity, salinity, temperature, and
dissolved oxygen concentration that were not used
in calibration. Comparison of simulated water -
surface elevation, velocity, salinity, temperature, and
dissolved oxygen concentration with measured
water -surface elevation, velocity, salinity,
temperature, and dissolved oxygen concentration
that were not used in calibration verifies the
reliability of the simulation.
3.6 Flushing Assessment
ATM proposes to assess flushing of the proposed
Amphitheater Road Marina by simulating
hydrodynamics and constituent transport ATM
proposes to assess flushing by simulating the
concentration of a conservative tracer, in the
proposed marina, as a function of time. The
concentration of the hypothetical, synthetic
constituent in the marina will nominally be one
milligram per cubic meter at the beginning of the
simulation. This constituent concentration will be
uniformly distributed throughout marina. The
concentration will decrease as constituent in the
marina is transported to the White Oak River, and as
water is the river is transported into the marina and
mixes with water in the marina. To quantify flushing
efficiency, ATM proposes to sum the mass of
constituent in the marina as a function of time, and
will express this sum as a fraction of mass of
constituent in the marina at the beginning of the
transport simulation.
The DEQ (NCDENR, 2011) cite an EPA (1985)
recommendation that more than 85 percent of the
mass of a constituent in the water body must flush
to the larger, connected water body within 24 hours.
ATM proposes to assess the proposed Amphitheater
Road Marina design by calculating the mass of
constituent in the proposed marina that is flushed to
the White Oak River within 24 hours.
ATM proposes to begin the transport simulation
after several days of hydrodynamics are simulated.
This spin -up period reduces or eliminates the
influence of the initial, hydrostatic condition in the
simulation, on the dynamic simulation of constituent
transport; and damps or removes sudden changes in
hydrodynamics that may exist at the beginning of a
hydrodynamic simulation.
ATM proposes to simulate the transport of a
hypothetical, synthetic, conservative constituent in
the proposed Amphitheater Road Marina. At the
❑F l i nn FNGINFFRINc 15

Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
Amphitheater Road Marina
beginning of the transport simulation, ATM
proposes to uniformly distribute one kilogram of
hypothetical constituent throughout the proposed
marina per cubic meter of water in the marina. ATM
proposes to simulate the change in mass in the
marina during the transport simulation, as
constituent in the marina is transported to the White
Oak River. To quantify flushing efficiency, ATM
proposes to sum the mass of constituent in the
marina as a function of time, and express this sum
as a fraction of mass of constituent in the marina at
the beginning of the transport simulation. ATM will
show that the mass of constituent in the marina at
the beginning of the transport simulation will
decrease by 85 percent over 24 hours, to 15 percent
of the initial mass in the marina, at the beginning of
the simulation.
The initial concentration of hypothetical constituent
in the marina of one kilogram per cubic meter is
arbitrary and irrelevant because the regulatory
criteria of 85 percent reduction over 24 hours is a
normalized criteria, expressed as a percentage of
initial mass in the marina.
3.7 Dissolved Oxygen Assessment
DEQ (NCDENR, 2011) stated that "maintaining water
quality within a marina basin depends primarily on
flushing as determined by the water circulation
within the basin. If a marina is not properly flushed,
pollutants will concentrate to unacceptable levels in
the water and/or bottom sediments, resulting in
impacts to biological resources. Dissolved oxygen is
important because aquatic organisms need it to exist
and because oxygen conditions affect water
chemistry. Anaerobic conditions are undesirable
because they increase the toxicity of some
compounds and can enhance the release of nutrients
and some heavy metals from sediments."
DEQ (NCDENR, 2011) require that "North Carolina
water quality standards state that dissolved oxygen
shall not be less than 5.0 milligrams per liter, except
that swamp waters, poorly flushed tidally influenced
stream or embayment, or estuarine bottom waters
may have lower values if caused by natural
conditions." DEQ (NCDENR, 2011) also require that
"the dissolved oxygen standard of 5.0 milligrams
per liter is based on a daily average."
ATM proposes to assess water quality associated
with the proposed Amphitheater Road Marina by
simulating dissolved oxygen concentration forced by
tide, wind, freshwater inflow, and generation and
consumption of dissolved oxygen. ATM proposes to
July 23, 2021
simulate dissolved oxygen concentration in the
White Oak River, and in the unnamed tributary to
White Oak River prior to construction of the
proposed marina. ATM then proposes to simulate
dissolved oxygen concentration in the river,
unnamed tributary, and marina, after construction of
the proposed marina.
ATM proposes to use the pre -project simulation to
determine the following:
1. Are the White Oak River or the unnamed
tributary near Hancock Point tidally
influenced?
2. Are the river or tributary poorly flushed?
3. Is the tributary estuarine? Is the river
estuarine at the confluence with the
tributary?
4. Are dissolved oxygen concentrations in the
bottom waters of the tributary or river less
than 5 milligrams per liter due to natural
conditions unrelated to the proposed
marina?
5. What is the depth -average, daily -average
dissolved oxygen concentration in the river
and tributary?
ATM proposes to use the post -project simulation to
determine the following:
6. What is the depth -average, daily -average
dissolved oxygen concentration in the river,
tributary, and proposed marina?
If depth -average, daily -average dissolved oxygen
concentration in the proposed marina is greater than
or equal to 5.0 milligrams per liter, ATM proposes to
present this information to DEQ in support of a
permit request. If depth -average, daily -average
dissolved oxygen concentration in the proposed
marina is less than 5.0 milligrams per liter, ATM
proposes to discuss information generated in
responses to items 1 through 5 with the DEQ, prior
to formally requesting a permit to construct the
proposed marina.
3.8 Assumptions and Limitations
Models are abstract representations of more
complex systems and processes. Almost all models
involve abstraction, in which systems and processes
are simplified to allow for tractable solution.
Abstraction requires assumptions and causes
limitations.
Al1 nn I FNG1'JFFR1NG 16

Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
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ATM proposes to simulate density gradients
associated with freshwater inflows mixing with
denser sea water. ATM does not propose to simulate
density gradients generated by evaporation of
surface water, or density gradients generated by
temperature differences. If density gradients exist in
the White Oak River, forced by evaporation or
temperature gradients, simulated water -surface
elevations, simulated velocities, and simulated
constituent concentrations may change. However,
qualitative findings will not likely change.
4.0 References
Environmental Systems Research Institute (Esri), 2021. World
imagery: geographic information system base map, accessed
July 9, 2021 at
https://www.arcqis.com/home/item.html?id=10df2279f9684e4a
9f6a7f08febac2a9.
Maxar, undated. April 20, 2020 aerial photograph of White Oak
River, accessed July 9, 2021 at
https://www.arcqis.com/home/item.html?id=10df2279f9684e4a
9f6a7f08febac2a9.
North Carolina Department of Environment and Natural Resources
(NCDENR), 2011 (February). Draft guidelines for planning an
upland marina development: State of North Carolina, North
Carolina Department of Environment and Natural Resources,
Division of Water Quality, guideline, 18 p.
North Carolina Department of Environmental Quality (DEG), 2017
(February). Ambient monitoring system program quality
assurance project plan: North Carolina Department of
Environmental Quality, Division of Water Resources, Water
Sciences Section, Ecosystems Branch document, version 2.0,
475 p., accessed July 13, 2021 at
https://datatools.tamscenter.com/hosted files/Water/Water
NC waterGAPP.pdf.
Natural Resource Conservation Service, 1986 (June). Urban
hydrology for small watersheds: United State Department of
Agriculture Natural Resource Conservation Service,
Conservation Engineering Division, technical release 55, 164
p., accessed July 9, 2021 at
https://www.nres.usda.gov/lnternet/FSE DOCUMENTS/stelpr
db1044171.pdf.
July 23, 2021
United States Environmental Protection Agency (USEPA), 1993
(January). Management measures for marinas and
recreational boating, chapter 5 in "Guidance Specifying
Management Measures for Sources of Nonpoint Pollution in
Coastal Waters": United States Environmental Protection
Agency EPA-840—B-92-002, 838 pages, accessed October 25,
2019 at https://www.epa.gov/nps/guidance-specifying-
management-measures-sources-nonpoint-pollution-coastal-
waters.
United States Environmental Protection Agency (USEPA), 2019.
Environmental modeling community of practice: EFDC
manuals: United States Environmental Protection Agency
website last updated on September 13, 2018, accessed
September 5, 2019 at https://www.epa.gov/ceam/efdc-
manuals.
United States Environmental Protection Agency (USEPA), 2017
(June 8). WASP8 Stream Transport —Model Theory and
User's Guide: United States Environmental Protection Agency
unnumbered report, 76 p., accessed July 8, 2021 at
https://www.epa.gov/sites/production/files/2018-
05/documents/stream-transport-user-quide.pdf.
U.S. Geological Survey (USGS), 2020. The National Map: National
Boundaries Dataset, 3DEP Elevation Program, Geographic
Names Information System, National Hydrography Dataset,
National Land Cover Database, National Structures Dataset,
and National Transportation Dataset; USGS Global
Ecosystems; U.S. Census Bureau TIGER/Line data; USFS Road
Data; Natural Earth Data; U.S. Department of State
Humanitarian Information Unit; and NOAA National Centers
for Environmental Information, U.S. Coastal Relief Model. Data
refreshed May, 2020, accessed August 29, 2020 at
https://www.usgs.gov/core-science-systems/national-
geospatial-program/national-map.
United States National Oceanic and Atmospheric Administration
(NOAA), 2021 a. Atlantic Beach, North Carolina tides and
currents station: National Oceanic and Atmospheric
Administration station identification 8656566, accessed July 9,
2021 at
https://ti desa ndcurrents. noaa.Qov/stati onhome.html? id=8656566.
United States National Oceanic and Atmospheric Administration
(NOAA), 2021b. Bogue Inlet, North Carolina tides and currents
station: National Oceanic and Atmospheric Administration
station identification TEC2837, accessed July 9, 2021 at
https://tidesandcurrents.noaa.gov/stationhome.html?id=TEC2837.
United States National Oceanic and Atmospheric Administration
(NOAA), 2021c. Beaufort, North Carolina tides and currents
station: National Oceanic and Atmospheric Administration
station identification 8656483, accessed July 9, 2021 at
https://ti desa ndcurrents. noaa.Qov/stati onhome.html? id=8656483.
A: I' M
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Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
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United States National Oceanic and Atmospheric Administration
(NOAA), 2021d. Wrightsville Beach, North Carolina tides and
currents station: National Oceanic and Atmospheric
Administration station identification 8658163, accessed July 9,
2021 at
https://tidesandcurrents.noaa.gov/stationhome.html?id=8658163.
United States National Oceanic and Atmospheric Administration
(NOAA), 2016 (July 4). North Carolina Statewide Lidar DEM
2014 Phase 1: accessed July 8, 2021 at
https://chs.coast.noaa.gov/htdata/raster2/elevation/NorthCaro
lina DEM 2014P1 5005/.
United States National Oceanic and Atmospheric Administration
(NOAA), 2019 (September 3). Continuously updated digital
elevation model (CUDEM), 1/9 arc -second resolution
bathymetric-topographic tiles: National Oceanic and
Atmospheric Administration DEM the
ncei19_n34x75_w077x25_2019v1.tif, described at
https://chs.coast.noaa.gov/htdata/raster2/elevation/NCEI nint
h Topobathv 2014 8483/, accessed July 8, 2021 at
https://chs.coast.noaa.gov/htdata/raster2/elevation/NCEI nint
h Topobathv 2014 8483/southeast/ncei19 n34x75 w077x25
2019v1.tif.
YSI (2020). EXO user manual: Xylem item 603789REF, revision K,
244 p., accessed July 23, 2021 at
https://www.vsi.com/file%201ibrary/documents/manuals/exo-
user-manual-web.pdf.
July 23, 2021
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Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
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Appendix: Photographs
July 23, 2021
ATMS1 19
ENGINNEEERING
CONSU L7ING

Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
Amphitheater Road Marina July 23, 2021
Photograph 1. July 2021 Dirt2Dreams photograph of station continuous-02 in the unnamed tributary to the White Oak River near Hancock
Point, looking southwest toward the confluence of the unnamed tributary with the White Oak River.
Photograph Z July 2021 Dirt2Dreams photograph of station continuous-01 in the White Oak River near Hancock Point, looking southwest
from the eastern riverbank.
ATM' MCONSULTINGGINE20
ENGINEERING

Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
Amphitheater Road Marina
W
s�
Photograph 3. July 20, 2021 Land Management Group photograph of station continuous-02 in the unnamed tributary to the
White Oak River near Hancock Point, looking southwest toward the confluence of the unnamed tributary with the White
Oak River.
July 23, 2021
Photograph 4. July 20, 2021 Land Management Group photograph of station discrete-04 in the White Oak River near Hancock Point, looking
south from the eastern riverbank.
ATM CONS T, 21

Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
Amphitheater Road Marina July 23, 2021
Photograph g July 20, 2021 Land Management Group photograph of station continuous-01 in the White Oak River near Hancock Point,
looking east toward the eastern riverbank.
IPW
Photograph 6. July 20, 2021 Land Management Group photograph of station continuous-02 in the unnamed tributary to
the White Oak River near Hancock Point, looking northeast from the confluence of the unnamed tributary to the White
Oak River with the White Oak River, toward the unnamed tributary.
I CE 22NS,N1M OT

Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
Amphitheater Road Marina
Photograph 7. July 20, 2021 Land Management Group photograph near station continuous-02 in the unnamed
tributary to the White Oak River near Hancock Point, looking southeast.
July 23, 2021
Photograph B. July 20, 2021 Land Management Group photograph near station discrete-02 in the unnamed tributary to the White Oak River
near Hancock Point, looking southeast.
ATM CONSU T, 23

Task 1: Environmental Monitoring and Hydrodynamic Simulation Plan
Amphitheater Road Marina
Photograph 9. July 20, 2021 Land Management Group photograph of station continuous-02 in the unnamed tributary to the
White Oak River near Hancock Point, looking southwest toward the confluence of the unnamed tributary with the White
Oak River.
Photograph 10. July20, 2021 Land Management Group photograph of station discrete-03
in the unnamed tributary to the White Oak River near Hancock Point, looking northeast.
July 23, 2021
ATM CONS T, 24