Appendix C Geotech Report_082615

Comprehensive Marine Sand Search and Borrow Area Design Report:
Towns of Duck, Kitty Hawk, and Kill Devil Hills, North Carolina

COMPREHENSIVE MARINE SAND SEARCH AND BORROW AREA DESIGN REPORT:
TOWNS OF DUCK, KITTY HAWK, and KILL DEVIL HILLS
DARE COUNTY, NORTH CAROLINA

Prepared by:

Coastal Planning & Engineering of North Carolina, Inc.

Prepared for:

Towns of Duck, Kitty Hawk, and Kill Devil Kills, North Carolina

Recommended Citation: Coastal Planning & Engineering of North Carolina, Inc., 2015.
Comprehensive Marine Sand Search and Borrow Area Design Report: Towns of Duck, Kitty
Hawk, and Kill Devil Hills, North Carolina. 49p. (Prepared for the Towns of Duck, Kitty Hawk,
and Kill Devil Hills, North Carolina).

August 2015

Comprehensive Marine Sand Search and Borrow Area Design Report:
Towns of Duck, Kitty Hawk, and Kill Devil Hills, North Carolina

Executive Summary

In 2013, Coastal Planning & Engineering of North Carolina, Inc. (CPE-NC) was authorized to
provide services in support of the effort by the Towns of Duck, Kitty Hawk, and Kill Devil Hills
to obtain the necessary permits and authorizations required for beach nourishment along
portions of the three Towns. As part of these efforts, CPE-NC was tasked with conducting a
comprehensie marine sand search investigation and borrow area design.

During the comprehensive marine sand search investigation, CPE-NC researchers conducted
geophysical (sidescan sonar, magnetometer, sub-bottom and bathymetric) and geotechnical
(beach characterization) surveys and compiled these data with existing information supplied
by the U.S. Army Corps of Engineers (USACE), the Bureau of Ocean Energy Management
(BOEM) and other Federal and non-federal entities. Approximately 230 nautical miles of
geophysical survey data were acquired in June and October of 2014. Geophysical data were
correlated with 100 vibracores collected by CPE-NC in July 2014 to characterize sediments.
From these data, two (2) proposed borrow areas were designed. Sediment samples were
collected along the shorelines of Duck, Kitty Hawk, and Kill Devil Hills by CPE-NC and
combined with samples taken by the USACE in 1993.

The compatibility of the proposed borrow areas with the existing beaches was evaluated
according to wet Munsell color, percent fine-size sediment, percent granular-size sediment,
percent gravel-size sediment, carbonate content and grain size. For the proposed borrow
areas all values meet the allowable limits defined by Rule 15A NCAC 07H .0312.

Quantum of work summary.

Reconnaissance level total nautical miles surveyed
(bathymetric and magnetometer)
60.0
Number of CPE-NC vibracores collected 100
Design level total nautical miles surveyed
(bathymetric, magnetometer, sub-bottom and sidescan sonar)
170.2
Number of proposed borrow areas identified 2

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Comprehensive Marine Sand Search and Borrow Area Design Report:
Towns of Duck, Kitty Hawk, and Kill Devil Hills, North Carolina

TABLE OF CONTENTS
Table of Contents .................................................................................................................... ii
List of Figures .......................................................................................................................... iii
List of Tables ............................................................................................................................ iv
List of Appendices .................................................................................................................... iv
INTRODUCTION ....................................................................................................................... 1
INVESTIGATION SEQUENCING ................................................................................................. 1
PHASE I INVESTIGATION .......................................................................................................... 4
Geological Background ................................................................................................................. 4
Previous Investigations .................................................................................................................. 6
Sand Resource Inventory .............................................................................................................. 8
Beach Characterization ................................................................................................................. 8
Results of Phase I Investigations .................................................................................................. 15
PHASE II INVESTIGATION ....................................................................................................... 16
Investigation Details .................................................................................................................... 16
Equipment and Methods ............................................................................................................. 17
Results and Discussion of Phase II: ............................................................................................ 24
PHASE III INVESTIGATION ...................................................................................................... 28
Equipment and Methods ............................................................................................................. 28
Results and Discussion ................................................................................................................. 33
PROPOSED BORROW AREA DESIGN ....................................................................................... 42
Design Considerations ................................................................................................................. 42
Data Quality ................................................................................................................................. 43
Compatibility Analysis ................................................................................................................... 44
CONCLUSIONS ....................................................................................................................... 47
ACKNOWLEDGEMENTS .......................................................................................................... 48
LITERATURE CITED ................................................................................................................. 48

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Comprehensive Marine Sand Search and Borrow Area Design Report:
Towns of Duck, Kitty Hawk, and Kill Devil Hills, North Carolina

LIST OF FIGURES

Figure 1. Project locations and sand search investigation areas. ................................................... 2
Figure 2. Map of the study area in northeastern North Carolina modified from Thieler et al.
2014. ............................................................................................................................................... 5
Figure 3. Figure showing historic areas of investigation by USACE, the Town of Nags Head, and
BOEM (MMS) and preliminary investigation areas targeted by CPE-NC in this investigation. ...... 7
Figure 4. Map showing the locations of jet probes and reconnaissance geophysical survey
tracklines as well as resulting preliminary areas of investigation. ................................................. 8
Figure 5. Representative cross section showing the location of samples collected along beach
profiles at Duck, Kitty Hawk, and Kill Devil Hills to characterize the existing beach. ................... 10
Figure 6. Map showing locations of sediment samples collected by CPE-NC along the Town of
Duck ocean shoreline. ................................................................................................................... 12
Figure 7. Map showing locations of sediment samples collected by CPE-NC along the Town of
Kitty Hawk ocean shoreline. ......................................................................................................... 13
Figure 8. Map showing locations of sediment samples collected by CPE-NC along the Town of
Kill Devil Hills ocean shoreline. ..................................................................................................... 14
Figure 9. Schematic diagram showing the deployment of a joint sub-bottom reflection profile,
bathymetric, magnetometer and sidescan sonar survey. ............................................................ 17
Figure 10. Photograph of the Geometrics G-882 Digital Cesium Marine Magnetometer used to
investigate magnetic anomalies within the potential sediment source. ..................................... 20
Figure 11. Photographs of the EdgeTech X-STAR SB-512i sub-bottom profiling system. ............ 21
Figure 12. Photographs of the EdgeTech 4200-HFL (left) and EdgeTech 4125 (right) sidescan
sonar systems. .............................................................................................................................. 24
Figure 13. Map showing the locations of tracklines surveyed and bathymetric data collected in
Area A during Phase II reconaissance geophysical survey and vibracores collected during Phase
III... ................................................................................................................................................ 25
Figure 14. Map showing the locations of tracklines surveyed and bathymetric data collected in
Area B during Phase II reconaissance geophysical surveys and vibracores collected during Phase
III. .................................................................................................................................................. 26
Figure 15. Map showing the locations of tracklines surveyed and bathymetric data collected in
Area C during Phase II reconaissance geophysical surveys and vibracores collected during Phase
III. .................................................................................................................................................. 27
Figure 16. Map showing the locations of geophysical tracklines surveyed and vibracores
collected during Phase II and III in preliminary investigation Area A. .......................................... 29
Figure 17 Map showing the locations of geophysical tracklines surveyed and vibracores
collected during Phase II and III in preliminary investigation Area C. .......................................... 30
Figure 18. Photograph of A-frame Deployment of the 271B Alpine Pneumatic vibracore system
from deck of the M/V Thunderforce. ............................................................................................ 31
Figure 19. Photograph showing vibracore field logging being conducted aboard the M/V
Thunderforce by CPE-NC geologists. ............................................................................................. 32
Figure 20. Photograph showing vibracore logging, sub-sample collection and Munsell color
determination being conducted. .................................................................................................. 33
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Figure 21. Map showing Proposed Borrow Area A. ...................................................................... 35
Figure 22. Map showing Proposed Borrow Area B. ...................................................................... 36
Figure 23. Example image of seismograph overlain with digitized reflectors and vibracores to
enable siemic interpretations. ...................................................................................................... 37
Figure 24. Sonargraph, showing large, high relief sand waves ranging in length from
approximately 150 meters to 275 meters in width. ..................................................................... 38
Figure 25. Sonargraph showing small, low relief sand ripples ranging from approximately 13
meter in length to 1 m meters in width........................................................................................ 38
Figure 26. Sonargraph showing potential isolated exposed mud patches with sand/gravel wave.
Isolated patches averaged at 40 meters long and 22 meters wide.............................................. 39
Figure 27. Sidescan sonar mosaic for Proposed Borrow Area A. ................................................. 40
Figure 28. Sidescan sonar mosaic for Proposed Borrow Area C. .................................................. 41

LIST OF TABLES

Table 1. Sieve sizes used for granularmetric analysis. .................................................................. 15
Table 2. Equipment used during the Phase II and III geophyscial investigations. ....................... 18
Table 3. Vibracore color code scheme. ........................................................................................ 34
Table 4. Borrow Area characteristics ........................................................................................... 43
Table 5. Beach and proposed borrow area characteristics .......................................................... 44
Table 6. Allowable fine, granular, gravel, and carbonate limits defined by State rules .............. 46
Table 7. Geophysical and geotechnical investigations conducted in 2014 .................................. 47

LIST OF APPENDICES

Appendix 1 Scope of Services (Digital Copy Only)
Appendix 2 CPE-NC Individual Beach Granularmetric Reports (Digital Copy Only)
Appendix 3 CPE-NC Individual Beach Grain Size Distribution Curves/Histograms (Digital Copy
Only)
Appendix 4 Beach Composite Summary Tables
Appendix 5 Beach Composite Granularmetric Reports (Digital Copy Only)
Appendix 6 Beach Composite Grain Size Curves/Histograms (Digital Copy Only)
Appendix 7 2014 CPE-NC Three Inch Clast Survey Results
Appendix 8 Investigation Permits (Digital Copy Only)
Appendix 9 2014 CPE-NC Seismic (Sub-bottom Data) (Digital Copy Only)
Appendix 10 2014 CPE-NC Sidescan Sonar Contact Sheets (Digital Copy Only)
Appendix 11 2014 CPE-NC Vibracore Logs
Appendix 12 2014 CPE-NC Vibracore Photographs
Appendix 13 2014 CPE-NC Individual Vibracore Granularmetric Reports (Digital Copy Only)
Appendix 14 2014 CPE-NC Individual Vibracore Grain Size Distribution Curves/Histograms
(Digital Copy Only)
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Appendix 15 2014 Tidewater Atlantic Research, Inc. Cultural Resource Report (Digital Copy
Only
Appendix 16 Proposed Borrow Areas Composite Summary Tables
Appendix 17 Proposed Borrow Areas Composite Granularmetric Reports (Digital Copy Only)
Appendix 18 Proposed Borrow Areas Composite Grain Size Curves/Histograms (Digital Copy
Only)
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Comprehensive Marine Sand Search and Borrow Area Design Report:
Towns of Duck, Kitty Hawk, and Kill Devil Hills, North Carolina

INTRODUCTION

Dare County’s beaches are a major economic engine to the tourist based economies of the local
Towns, the County, and the entire northeastern North Carolina region. The Towns of Duck, Kitty
Hawk, and Kill Devil Hills partnered with Dare County to design a combined beach nourishment
project that would reduce storm damage and flood damage to the three communities. In an
effort to realize cost efficiencies, the three Towns and Dare County hired Coastal Planning &
Engineering of North Carolina, Inc. (CPE-NC) to conduct a comprehensie marine sand search
investigation and design borrow areas for the combined project that would meet the State of
North Carolina’s sediment criteria rule (15A NCAC 07H .0312) (See Appendix 1 for Scope of
Work).

The Towns of Duck, Kitty Hawk, and Kill Devil Hills are located in Dare County in northeastern
North Carolina. These beach municipalities are geographically located on a spit of land in the
Outer Banks of North Carolina known as Bodie Island. The northernmost municipality, the Town
of Duck, is bordered to the north by an unincorporated portion of Currituck County and to the
south by the Town of Southern Shores. The Town of Kitty Hawk is bordered to the north by the
Town of Southern Shores and Kill Devil Hills to the south. The Town of Nags Head is located to
the south of Kill Devil Hills. All three towns are bound by the Atlantic Ocean to the east and the
Albemarle Sound to the west (Figure 1).

INVESTIGATION SEQUENCING

A systematic approach to marine sand searches has been developed over the years by our
Coastal Geology and Geomatics team (e.g. Finkl, Khalil and Andrews, 1997; Finkl, Andrews and
Benedet, 2003; Finkl, Benedet and Andrews, 2005; Finkl and Khalil, 2005). In a comprehensive
marine sand search, investigations are typically divided into three (3) sequential phases. This
phased approach can be modified to meet the scope of the investigation and accommodate the
level of work previously performed. Regardless of the phases executed during a sand search,
the CPE-NC investigation sequencing is preserved in order to maintain efficiency and
completeness to provide confident results.

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Figure 1. Project locations and sand search investigation areas.

Phase I investigations typically consist of a comprehensive review of the recipient
beach(s)/project area(s) and sediment resources offshore of the project area. This desktop
study examines previously collected information within the geologic context of the
investigation area in order to identify features having the highest potential of containing
project-compatible sand. The geological background of the area is assessed to identify the
geomorphic features that may contain material suitable for the project. Information related to
previously investigated areas is compiled and related back to the geomorphic features.
Geophysical and geotechnical data previously collected within these areas, as well as any
reports discussing the findings, are then reviewed. Based on this analysis, deposits potentially
containing project-compatible material are identified. The results of Phase I are used to define
the areas that will be surveyed during Phase II investigations.

Phase II investigations usually consist of reconnaissance level geophysical and geotechnical
surveys. A joint geophysical investigation (typically collecting sub-bottom reflection profiles,
sidescan sonar images, magnetometer and bathymetric data) is conducted at reconnaissance
line spacing to assess the thickness of potential sand resources. The wide reconnaissance line
spacing is designed to cover larger expanses of seafloor. Therefore, the data coverage achieved
during Phase II investigations may not be sufficient to develop a detailed sand thickness
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(isopachous) map. Geophysical data collected during this phase are used to design a vibracore
investigation plan. Vibracores may be collected to determine the sediment characteristics
within the areas identified through remote sensing. Typically a limited number of cores are
collected to groundtruth each potential sand resource. Sand resources within the investigation
area are then analyzed using Geographic Information System (GIS) procedures that integrate
the sub-bottom reflection profile and vibracore data to provide an estimate of deposit
thickness and sedimentary characteristics. Samples may also be collected from the project area
during this phase to characterize the project area/existing beach in terms of grain size, color
and composition (i.e. how well the proposed borrow area sediment matches the existing
material in the project area). The Phase II results are reviewed within the context of
beach/project compatibility to identify potential resource areas that will undergo design level
investigations during Phase III.

Phase III typically consists of design level geotechnical and geophysical investigations, a cultural
resource investigation, and borrow area design. A joint sub-bottom, sidescan sonar,
magnetometer and bathymetric survey is conducted within the potential sand resource area(s).
The data collected are used to identify possible cultural or environmental resources for
avoidance and to develop isopach (sediment thickness) maps for proposed borrow area design.
These results are also used to target areas for additional vibracoring. In order to conform to
standard geological and engineering practice, fulfill permitting requirements, and conduct
geophysical and geotechnical surveys in an expeditious manner, vibracores are collected to
provide a maximum spacing of 1000 ft. (industry standard spacing) within the potential
resource area. Whenever possible, the vibracores are opened and evaluated during the
investigation to provide on-the-fly guidance. This provides an opportunity for immediate visual
evaluation of the sediment and real-time optimization of the vibracoring plan (the sampling
program is modified on the basis of what is observed in the recovered materials). This flexibility
in the field allows experienced geologists to refine the investigation plan to focus on potential
sand resources. Proposed borrow area boundaries and excavation depths are developed from
the data collected during the Phase I, II and III investigations.

A final cultural resource investigation is required to permit borrow areas for use. During this
investigation, additional geophysical data are collected within the proposed borrow area to
achieve a total combined line spacing of 30 m (approximately 98 ft.). A qualified marine
archaeologist who meets the standards set forth by the Secretary of the United States
Department of the Interior is required to be on the survey vessel at all times during the cultural
resource investigation. The geophysical data are used to identify any cultural resources,
submerged hazards or any other features that would affect borrow area delineation and
dredging activities. Based on the results of the cultural resource investigation, the marine
archaeologist compiles a report that includes recommendations for buffers around any
potentially significant magnetic anomalies. The final borrow area design is then modified to
take the recommended buffers into account.

During this marine sand search investigation, a Phase I desktop study was conducted. This was
followed by a Phase II reconnaissance geophysical survey. Finally, Phase III of this investigation
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included geotechnical investigations, a concurrent geophysical/cultural resource survey, and
borrow area design.

PHASE I INVESTIGATION

During the Phase I investigation, CPE-NC researchers conducted archival literature studies of
the inner continental shelf area, with a focus on abundant sand resources in proximity to the
project locations within the investigation areas. Past investigation areas, previously identified
sand sources and developed borrow areas, and previously collected geotechnical and
geophysical data was compiled. This information was brought into a GIS framework and was
analyzed within the geologic context of the continental shelf area in order to identify
potentially beach-compatible sand resources for further investigation. Sampling and analysis of
the three recipient beaches was also conducted during this phase of the investigation. The
information and data compiled during the Phase I investigation is discussed below.

Geological Background
Developing an understanding of the geologic setting of the project area is an important part of
the Phase I investigations because it provides contextual information that sets limits to
potential sand resources. A description of the regional geologic setting defines the framework
bedrock seafloor surfaces and the sediments that sit on them. The nature of sedimentary
deposits determines sand quality, distribution, and its potential use for beach nourishment. It is
thus necessary to understand the general continental shelf environments because the
distribution of beach-quality sands on the seabed is not random, but spatially organized.

The northeastern portion of the North Carolina offshore coastal system is referred to as the
Albemarle Embayment. The embayment is bound geologically by the Cape Lookout High to the
south, the Norfolk Arch to the north, the Atlantic Ocean to the east and barrier island structure
to the west that make up the Outer Banks, North Carolina (Thieler et al., 2014) (Figure 2).

The inner continental shelf in the Albemarle Embayment is characterized by abundant sediment
deposition reflected in large shoal structures and shoreface attached ridges as well as sediment
poor portions of sorted bedform outcrop (Thieler et al., 2014). The underlying geologic
framework of the offshore area in the Albemarle Embayment Outer Continental Shelf (OCS) is a
depositional basin characterized by a Quaternary sequence (Riggs et al. 1994).
Morphosedimentary patterns and the geographic location of coastal barriers and inlets along
the North Carolina coast are influenced by the inherited geologic framework (e.g. Macintyre
and Pilkey, 1969; Riggs et al., 1995). Barrier Islands in the northeastern offshore system have
evolved in response to sediments supplied by three primary sources: paleo-fluvial channels,
shoal complexes, and sand-rich Holocene sedimentary deposits.

A notable feature within the project area is a large paleo-fluvial valley system, Albemarle Shelf
Valley, between the Town of Kitty Hawk and Oregon Inlet that influences local seafloor
geomorphology as well as barrier island evolution. Seafloor sediments that are found in the
project area include river gravels, shell/rock fragments, thin layers of Pleistocene sediment as
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well as ridges composed primarily of Holocene (sediments deposited within the past 10,000
years) sand deposits (Thieler et al., 2014).

Oregon Shoal, Platt Shoals, Wimble Shoals, Kinnakeet Shoals, and Diamond Shoals represent a
pattern of large, sediment rich, shoal structures that make up the portion of the Albemarle
Embayment extending south from the Town of Kitty Hawk to Cape Hatteras (Diamond Shoals)
(Thieler et al., 2014) (Figure 2). The shoal structures located within the OCS offshore of the
project areas provide high potential for quality sand resources.

Figure 2. Map of the study area in northeastern North Carolina modified from Thieler et al.
2014. Bathymetry data is from the NOAA NGDC Coastal Relief Model
(www.ngdc.noaa.gov/mgg/coastal/startcrm.htm) and Thieler et al. 2014.

Oregon
Shoal
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Previous Investigations
The following are summaries of several marine surveys and geotechnical studies previously
conducted within the vicinity of the Towns of Duck, Kitty Hawk, and Kill Devil Hills. This
information was compiled during the Phase I investigation and was evaluated within the
context of the geologic framework to formulate the Phase II and III investigations.

The North Carolina Geological Survey (NCGS) and Minerals Management Service (MMS),
presently referred to as the Bureau of Ocean Energy Management (BOEM), collected fifty-six
(56) vibracores offshore of Dare County, North Carolina in 1996. Figure 3 shows the locations
of these vibracores.

The U.S. Army Corps of Engineers (USACE) completed an extensive Environmental Impact
Statement (EIS) on Hurricane Protection and Beach Erosion Control for Dare County Beaches
(USACE, 2000), North Carolina. In the report, the USACE compiled native beach sediment
characteristics as well as identified potential offshore sand resources by geophysical and
geotechnical investigations. Phase I of the USACE investigation collected approximately 535
miles of high resolution seismic reflection and CHIRP sonar followed by 208 vibracores collected
in 1995 and 1998 offshore of the project area(s) that represented Phase II of the investigation.
The USACE vibracores were logged, sampled and analyzed for grain size characteristics in order
to conduct a sand compatibility analysis. As a result of the USACE investigation, five (5)
potential borrow areas were developed approximately one-half mile (0.5) to three miles (3)
offshore of the project locations. Borrow Areas N1 and N2 were located between 0.5 and 2
miles directly offshore of Kitty Hawk and Kill Devil Hills (Figure 3); however, further analysis of
these borrow areas suggested the mean grain size was too fine and had a relatively high
percentage of silt. Based on vibracore data, the largest of these borrow areas, S1 located
offshore of the Town of Nags Head, contained high quality beach sand. This area was pursued
by the Town of Nags Head for their project in 2011. Three sub-areas within borrow area S1
were permitted by the Town and two (2) of them were used for the actual construction (Figure
3).

CPE-NC conducted jet probe investigations of several shoal features offshore Dare County in
2013 as part of a feasibility study for the Town of Kill Devil Hills. A crew of four (4) scientists
and technicians conducted the jet probe (washbore) survey offshore Dare County between
Duck and Nags Head, North Carolina between September 5 and September 9, 2013. Over the
four days of operations, a total of 29 washbore surveys were conducted (Figure 4). At each
location, the proposed methodology was to collect a grab sample of the undisturbed seafloor
surface, a second sample of the spoils that were jetted out of the washbore hole from the
maximum depth penetrated, and a third sample to be taken of the spoils that were jetted out
of the washbore at ½ the depth of maximum penetration. At most locations, all three samples
were obtained; however, depending on the maximum penetrations depth and type of material
encountered at some locations less than three (3) samples were obtained. In total, 80 grab
samples were collected during the survey.

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Figure 3. Figure showing historic areas of investigation by USACE, the Town of Nags Head, and BOEM (MMS) and preliminary investigation areas targeted by CPE-NC in this investigation.
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Figure 4. Map showing the locations of jet probes (September 2013) and reconnaissance
geophysical survey tracklines (June 2014) as well as resulting preliminary areas of investigation.

Sand Resource Inventory
The type of sand resource that is targeted during a sand search investigation largely depends on
the geologic framework in the area of investigation. CPE-NC experience indicates that beach
quality sands offshore of northeastern North Carolina (Outer Banks) are most likely located in
shoal structures. A preliminary inventory of sand resources within the study area has been
developed based on an interpretation of bathymetric Digital Elevation Models (DEMs) (Finkl et
al., 2008) and is presented in Figure 3. Bathymetric data evaluated during the development of
the sand resource inventory analysis were developed from historic NOS bathymetry. The grid
was then converted to a color-shaded relief map so that variations in the bathymetry become
obvious. Locations of bathymetric highes that indicate potential beach quality sand were
identified for further investigation.

Beach Characterization
The suitability of a sand source for beach nourishment is directly linked to the characteristics of
the recipient beach. The State of North Carolina requires that sand resources for nourishment
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be “beach compatible”, that is, “similar” to sand existing in the project area. Qualities such as
grain size, silt content, color, and mineralogical content are taken into account. Therefore, it is
important to accurately characterize existing beach sediments during a sand search
investigation. The quality of material that can be placed on North Carolina’s beaches is
governed by Rule 15A NCAC 07H .0312 which states that:

Placement of sediment along the oceanfront shoreline is referred to in this Rule as “beach fill.”
Sediment used solely to establish or strengthen dunes or to re-establish state-maintained
transportation corridors across a barrier island breach in a disaster area as declared by the
Governor is not considered a beach fill project under this Rule. Beach fill projects including
beach nourishment, dredged material disposal, habitat restoration, storm protection, and erosion
control may be permitted under the following conditions: (3)The Division of Coastal Management shall determine sediment compatibility according to the following criteria: (a) Sediment completely confined to the permitted dredge depth of a maintained navigation channel or associated sediment deposition basins within the active nearshore, beach or inlet shoal system is considered compatible if the average percentage by weight of fine-grained (less than 0.0625 millimeters) sediment is less than 10 percent; (b) The average percentage by weight of fine-grained sediment (less than 0.0625 millimeters) in each borrow site shall not exceed the average percentage by weight of fine-grained sediment of the recipient beach characterization plus five percent; (c) The average percentage by weight of granular sediment (greater than or equal to 2 millimeters and less than 4.76 millimeters) in a borrow site shall not exceed the average percentage by weight of coarse-sand sediment of the recipient beach characterization plus five percent; (d) The average percentage by weight of gravel (greater than or equal to 4.76 millimeters and less than 76 millimeters) in a borrow site shall not exceed the average percentage by weight of gravel-sized sediment for the recipient beach characterization plus five percent; (e) The average percentage by weight of calcium carbonate in a borrow site shall not exceed the average percentage by weight of calcium carbonate of the recipient beach characterization plus 15 percent; and (f) Techniques that take incompatible sediment within a borrow site or combination of sites and make it compatible with that of the recipient beach characterization shall be evaluated on a case-by-case basis by the Division of Coastal Management. (4)Excavation and placement of sediment shall conform to the following criteria:
(a) Sediment excavation depth from a maintained navigation channel shall
not exceed the permitted dredge depth of the channel; (b) Sediment excavation depths for all borrow sites shall not exceed the maximum depth of recovered core at each coring location; (c) In order to protect threatened and endangered species, and to minimize impacts to fish, shellfish and wildlife resources, no excavation or placement of sediment shall occur within the project area during times designated by the Division of Coastal Management in consultation with other State and Federal agencies; and
(d) Sediment and shell material with a diameter greater than or equal to
three inches (76 millimeters) is considered incompatible if it has been placed on the
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beach during the beach fill project, is observed between MLW and the frontal dune
toe, and is in excess of twice the background value of material of the same size along
any 50,000-square-foot (4,645 square meter) section of beach.

During the development of the Federally Authorized Dare County Storm Damage Reduction
Project (Bodie Island Portion), the USACE collected beach samples along shore perpendicular
profiles within the federal project areas. Samples were collected from the dune out to a depth
of -20 ft NAVD88. The state sediment standards dictate a specific number of samples along at
least five (5) profiles within each project area with no more than five thousand (5,000) foot
spacing (15A NCAC 07H.0312)(1)(c)(d). In order to meet state requirements, the initial sampling
plan included the collection and analysis of supplemental samples along those profiles in the
Kitty Hawk and Kill Devil Hills Project Area previously sampled by the USACE. The sampling plan
also included collection of 13 samples along five (5) profiles within the Town of Duck; however,
at the time of initial sampling, the project limits for Duck had not yet been established.

The combined data sets provide a profile of the beach with samples taken from the Dune, Toe
of Dune, Mid-berm, Berm Crest, Mean High Water (MHW), Mean Tide Level (MTL), Mean Low
Water (MLW), Trough, and Bar Crest. Results of mechanical sieve analysis were composited by
transect as well as by elevation. These composites were used in assessing the compatibility of
the proposed borrow areas with the native beach. Figure 5 shows a cross section diagram
illustrating the locations along each profile in which samples were collected.

Figure 5. Representative cross section showing the location of samples collected along beach
profiles at Duck, Kitty Hawk, and Kill Devil Hills to characterize the existing beach.

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Following the initial sampling and analysis of the beach, the North Carolina Division of Coastal
Management (NC DCM) stated that the samples collected by the USACE would not be accepted
and new samples would be required. CPE-NC re-sampled those morphodynamic zones
previously sampled by the USACE based on present day profile conditions. Furthermore, the
NC DCM stated that those profiles sampled along the Town of Duck that were not within the
final project limits could not be used to establish the existing beach characteristics. Therefore,
CPE-NC collected samples along three (3) additional profiles within the project limits.

The following is a chronological description of the collection of beach samples used to develop
existing beach sediment characteristics:

A. On October 15, 2013, CPE-NC collected beach samples and nearshore sediment samples
along five (5) profiles in the Duck project area (D-03, D-08, D-13, D-18, D-24) (Figure 5).
A total of 65 new samples were collected.
B. On April 26, 2014, CPE-NC collected beach samples and nearshore sediment samples
along five (5) profiles (KH0+00, KH50+00, KH75+00, KH110+00, KH160+00) (Figure 6). A
total of 26 new samples were collected to complement existing beach samples collected
by the USACE in 1993.
C. On September 14 and 15, 2014, CPE-NC collected beach samples and nearshore
sediment samples along five (5) profiles in Kill Devil Hills (KDH160+00, KDH210+00,
KDH260+00, KDH290+00, KDH320+00) (Figure 7). A total of 28 new samples were
collected to complement existing beach samples collected by the USACE in 1996
D. On August 4th and 5th, 2015, CPE-NC collected beach samples and nearshore sediment
samples along three (3) profiles in the Duck project area (D-11, D-15, and D-17) (Figure
6). A total of 39 new samples were collected.
E. On August 4th and 5th, 2015, CPE-NC collected beach samples and nearshore sediment
samples along five (5) profiles (KH0+00, KH50+00, KH75+00, KH110+00, KH160+00)
(Figure 7). A total of 39 new samples were collected.
F. On August 4th and 5th, 2015, CPE-NC collected beach samples and nearshore sediment
samples along five (5) profiles in Kill Devil Hills (KDH210+00, KDH235+00, KDH260+00,
KDH290+00, KDH320+00) (Figure 8). A total of 41 new samples were collected.

Sediment Grain Size (Mechanical) Analysis: During sieve analysis, dry and washed Munsell
colors were noted. Sieve analyses were conducted on all sediment samples in accordance with
American Society for Testing and Materials Standard Materials Designation D422-63 for particle
size analysis of soils (ASTM, 2007). This method covered the quantitative determination of the
distribution of sand size particles. For sediment finer than the No. 230 sieve (4.0 phi) the ASTM
Standard Test Method, Designation D1140-00 was followed (ASTM, 2006). Mechanical sieving
was accomplished using calibrated sieves with a gradation of half phi intervals. Table 1 shows
those sieves used in the analysis. Additional sieves representing key ASTM sediment
classification boundaries were included to meet North Carolina technical standards for beach
fill projects (15A NCAC 07H .0312 (d)) Weights retained on each sieve were recorded
cumulatively.
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Figure 6. Map showing locations of sediment samples collected by CPE-NC along the Town
of Duck ocean shoreline.

Grain size data were entered into the gINT® software program, which computes the mean and
median grain size, sorting, and silt/clay percentages for each sample using the moment method
(Folk, 1974). Granularmetric reports and grain size distribution curves were compiled for each
sample.

Carbonate Content Determination: Carbonate content was determined by percent weight
using the acid leaching methodology described in Twenhofel and Tyler (1941). Results were
entered into the gINT® software and are displayed on the granularmetric reports.

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Figure 7. Map showing locations of sediment samples collected by CPE-NC along the Town
of Kitty Hawk ocean shoreline.

Quantifying Clasts > Three Inches: On September 14, 2013, CPE-NC conducted a survey of a
~50,000 square foot portion of the Duck project area along the the beach just south of Skimmer
Way and just north of Flight Drive. The area was staked out using GPS to mark the four (4)
corners of a rectangular section of the beach measuring approximately 325 ft. along the beach
and 154 ft. across the beach from the toe of dune to the MLW Line. The area was staked out
into 10 ft. x 10 ft. blocks to facilitate the counting of clasts > 3 inches in each block.

CPE-NC conducted a survey of a ~50,000 square foot portion of the Kitty Hawk project area
from a point approximately 545 ft. north to 80 ft. south of Bleriot Street, on May 12, 2015 in
order to quantify the number of clasts > 3 inches. The area was staked out using GPS to mark
the four (4) corners of a rectangular section of the beach measuring approximately 625 ft. along
the beach and 80 ft. across the beach from the toe of dune to the MLW Line. The area was
divided into 25 ft. x 20 ft. blocks to facilitate the counting of clasts > 3 inches in each block.
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Figure 8. Map showing locations of sediment samples collected by CPE-NC along the Town
of Kill Devil Hills ocean shoreline.

On September 15, 2013, CPE-NC conducted a survey of a ~50,000 square foot portion of the Kill
Devil Hills project area from a point slightly south of Sea Village Lane and slightly north of
Wilkinson Street in order to quantify the number of clasts > 3 inches. The area was staked out
using GPS to mark the four (4) corners of a rectangular section of the beach measuring
approximately 300 ft. along the beach and 200 ft. across the beach from the toe of dune to the
MLW Line. The area was divided into 10 ft. x 10 ft. blocks to facilitate the counting of clasts > 3
inches in each block.

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Table 1. Sieve sizes used for grain size analysis. Classifications are based on percent retained in
each sieve.
Classification Sieve Size
(number)
Sieve Size
(phi)
Sieve
Size
(mm)
3/4" -4.25 19.00
5/8" -4 16.00
gravel 7/16" -3.5 11.20
5/16" -3 8.00
3 1/2" -2.5 5.60
4 -2.25 4.75
5 -2 4.00
granular 7 -1.5 2.80
10 -1 2.00
14 -0.5 1.40
18 0 1.00
25 0.5 0.71
35 1 0.50
45 1.5 0.36
sand 60 2 0.25
80 2.5 0.18
120 3 0.13
170 3.5 0.09
200 3.75 0.08
230 4 0.06
fine pan - -

Results of Phase I Investigations

Sand Resource Inventory: Data collected during the Phase I investigations was used to develop
a survey plan for the Phase II investigations. Observations made during the jetprobe operations
as well as data generated from processing sediment samples suggest a high probability of
sufficient quantities of beach compatible sand exists within the areas investigated (CPE-NC,
2013). A review of regional bathymetry, historic vibracore logs, historic grab samples , and the
jet probe data obtained by CPE-NC in 2013 resulted in the identification of four (4) primary
investigation areas (Figure 4). These areas were subsequently targeted during Phase II and III
investigations.

Beach Characterization: Beach samples were collected to characterize the existing beach.
Appendices 2 and 3 contain granularmetric reports and grain size curves/histograms.
Composite grain size characteristics were developed for each profile line as well as for each
position along the beach profile. Composites are presented in Appendices 4, 5 and 6.
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The following characteristics represent the existing beach for each project area:

A. Summary composite results (Appendix 4) indicate that sediment within the Town of
Duck project area has a composite mean grain size of 0.33 mm. The composite silt content
throughout the project area is 1.01%. The composite granular and gravel fraction for the
project area is 0.39% and 2.00%, respectively. The composite carbonate content is 2% for the
project area. The composite wet Munsell Color value ranges from 5 to 6, with a typical
composite value of 5. The composite dry Munsell Color value is 6.

B. Summary composite results (Appendix 4) indicate that sediment within the Kitty Hawk
project area has a composite mean grain size of 0.38 mm. The composite silt content
throughout the project area is 0.94%. The composite granular and gravel fraction for the
project area is 6.38% and 1.64%, respectively. The composite carbonate content is 2% for the
project area. The composite wet Munsell Color value ranges from 5 to 7, with a typical
composite value of 5. The composite dry Munsell Color value is 7.

C. Summary composite results (Appendix 4) indicate that sediment within the Kill Devil
Hills project area has a composite mean grain size of 0.36 mm. The composite silt content
throughout the project area is 0.90%. The composite granular and gravel fraction for the
project area is 5.15% and 1.62%, respectively. The composite carbonate content is 2% for the
project area. The composite wet Munsell Color value ranges from 5 to 7, with a typical
composite value of 5. The composite dry Munsell Color value is 7.

Quantifying Clasts > Three Inches
The total number of clasts > 3 inches in diameter identified during the survey of the
representative project area in the Town of Duck was 25. The total number of clasts > 3 inches
in diameter identified during the survey of the representative project area in the Town of Kitty
Hawk was 403. The total number of clasts > 3 inches in diameter identified during the survey of
the representative project area in the Town of Kill Devil Hills was 51. Appendix 7 includes a
table or clast distribution throughout each of the three (3) areas surveyed.

PHASE II INVESTIGATION

Investigation Details
During Phase II investigations, CPE-NC conducted reconnaissance level geophysical surveys
(sub-bottom profile, sidescan, magnetometer, and bathymetric) within the areas identified for
additional investigation during Phase I. For areas located in Federal waters, prior to conducting
the geophysical surveys, CPE-NC was required to apply for authorization from the Bureau of
Ocean Energy Management (BOEM) to conduct Geophysical Prospecting for Mineral Resources
on the Outer Continental Shelf Related to Minerals Other than Oil, Gas, and Sulphur. The
BOEM granted the Authorization (E13-002) on March 26, 2014.

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The geophysical survey was conducted between June 9 and June 15, 2014. The M/V
Thunderforce was used as the platform for conducting the survey. A total of 69.1 nautical line
miles of geophysical data were collected. These data were used to delineate areas for further
investigation. Areas targeted were those believed to contain accumulations of beach quality
sand. Figure 4 shows the location of the geophysical tracklines associated with Phase II. The
geophysical data were groundtruthed using data from the jet probes as well as historic
vibracore and sediment samples. Data obtained from Phase II investigations, were used to
determine areas to be investigated in Phase III investigations via vibracoring and detailed design
level geophysical surveys and cultural resource surveys.

Equipment and Methods
Due to the scope and precision required by modern sand search protocols, a wide range of
geophysical and geotechnical survey methods are required. The Phase II investigations included
bathymetric, sidescan sonar, sub-bottom reflection profiling and magnetometer surveys. The
geophysical and geotechnical data was collected under the responsible charge of a professional
geologist registered in the State of North Carolina. The navigation and hydrographic surveys
were conducted under the direction of a Certified Hydrographic Surveyor. The bathymetric,
sidescan sonar, sub-bottom reflection profiling and magnetometer surveys were conducted
concurrently using the setup illustrated in Figure 9. The collection and processing of this data is
described below. The geophysical equipment used in Phase II as well as Phase III are listed in
Table 2.
Figure 9. Schematic diagram showing the deployment of a joint sub-bottom reflection profile,
bathymetric, magnetometer and sidescan sonar survey.

Navigation Systems: The navigation and positioning system deployed for this survey was a
Trimble real-time kinematic (RTK) global positioning system (GPS) with dual frequency
receivers. RTK GPS relies on a base station and transmitter placed on a survey point with a
Fathometer Magnetometer CHIRP
Seismic
Fish
Survey Vessel
Sidescan
Sonar
Fish
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known elevation and horizontal position. The base station for the survey was set at two
locations, the CPE-NC SEA RANCH in Kill Devil Hills and 1370K TIDAL located on the USACE Duck
Field Research Facility Pier depending on which proposed borrow area was being surveyed.
These locations provide the clear horizon needed to minimize phase-measurement effects
caused by multi-pathing. The base station position for the RTK GPS system was surveyed and
established prior to survey operations. Horizontal and vertical positioning checks were
conducted before and after the survey, within the project area to confirm network and survey
accuracy. The base station transmits carrier phase and Doppler shift corrections via radio link to
a receiver onboard the survey vessel. The receiver on the survey vessel can then apply the
carrier phase and Doppler shift corrections to the position of the vessel as measured by GPS
satellites.

Table 2. Equipment used during the Phase II and III geophysical investigations.

All navigation and survey control for the geophysical surveys and positioning for vibracores was
conducted under the direction of a ACSM Certified Hydrographic Surveyor. The vertical
accuracy of control data meets the requirements set forth in the United States Army Corps of
Engineers manual EM 1110-2-1003. GPS data was collected at 1 Hz or faster to minimize
position interpolation when assigning the position to the various geophysical data.

Hypack Inc.’s Hypack 2013®: Data Collection and Processing Program: Navigational,
magnetometer, and depth sounder systems were interfaced with an onboard computer, and
the data was integrated in real time using Hypack Inc.’s Hypack 2013® software. Hypack 2013® is
a state-of-the-art navigation and hydrographic surveying system. The location of each of the
fish tow-point on the vessel and the length of cable deployed between the tow-point and each
towfish in relation to the RTK GPS was measured, recorded and entered into the Hypack 2013®
survey program. Hypack 2013® then takes these values and monitors the actual position of each
towfish in real time. Online screen graphic displays include the pre-plotted survey lines, the
updated boat track across the survey area, adjustable left/right indicator, as well as other
positioning information such as boat speed, quality of fix measured by Position Dilution of
Precision (PDOP), and line bearing. The digital data is merged with positioning data (RTK GPS),
Equipment Type Description
Navigation
Trimble 5700 Real Time Kinematic (RTK) Global Positioning
System (GPS) interfaced with Hypack Inc.’s Hypack 2013®
software
Sounder (Bathymetry) Odom Hydrographic Systems, Inc. “Hydrotrac” Hydrographic
Echo Sounder
Sub-bottom Profiler (Seismic
Reflection)
EdgeTech X-STAR SB-512i Sub-bottom Profiler
Sidescan Sonar EdgeTech 4200-HFL and EdgeTech 4125
Magnetometer Geometrics G-882 Digital Cesium Marine Magnetometer
interfaced with Hypack Inc.’s Hypack 2013® software
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video displayed and recorded to the acquisition computers hard disk for post processing and/or
replay.

Bathymetric Survey: The Odom Hydrographic Systems, Inc.’s Hydrotrac, a single frequency
portable hydrographic echo sounder, was used to perform the bathymetric survey. The
Hydrotrac can operate with tranducers at frequencies of 24, 33, 40, 200, 210, or 340 kHz and is
a digital, survey-grade sounder. A 210 kHz transducer was used for the bathymetric survey.

Prior to the start of the survey, a reconnaissance survey of the second order monuments was
conducted to confirm that the survey control was in place and undisturbed. RTK GPS was used
to locate and confirm the survey control for this project. To achieve the required accuracy, the
hydrographic survey was controlled using second order monuments.

Horizontal and vertical RTK GPS positioning checks and sounder calibration were performed
periodically throughout the survey (typically at the beginning and end of each survey day). The
sounder was calibrated via bar-checks and a sound velocity probe. The DIGIBAR PRO sound
velocity meter is used to find the average sound velocity needed to calibrate the Hydrotrac
sounder prior to performing the bar-check. Bar checks were performed from a depth of 10 ft. to
30 ft. Analog data showing the results of the bar check calibration is displayed on the sounder
charts at 5 ft. increments during descent of the bar.

Real-time navigation software (Hypack), was used to provide navigation to the helm in order to
minimize deviation from the online azimuth. This software provides horizontal position to the
sounding data allowing real-time review of the data in plan view or cross section format. A
Trimble RTK GPS and a TSS Motion Compensator were used onboard the survey vessel to
provide instantaneous tide corrections as well as heave, pitch and roll corrections. Soundings
were collected at intervals sufficient to provide an accurate depiction of the seafloor. Cross
lines (tie lines) were collected to verify survey accuracies.

A secondary tide data record was obtained from the USACE Duck Field Research Facility, tide
station (ID: 8651370). Water level was recorded every six minutes and was downloaded from
the USACE DUCK Field Research Facility website daily. These data were used as a check to
verify the accuracy of the RTK data collected in real time.

Upon completion of the field work, data was edited and reduced with CPE’s internal software
programs and Hypack 2013®. The RTK tide data was compared to the USACE DUCK Field
Research Facility tide station data for verification purposes. The offshore raw digital data was
viewed and edited in Hypack 2013®. Digitized data was scanned for noise and compared to the
analog record. False soundings were removed and a comma delimited ASCII file was created
and exported.

Magnetometer Survey: High-resolution magnetic remote sensing is needed to identify any
metallic objects that could represent a potential cultural resource or hazard to construction. A
Geometrics G-882 Digital Cesium Marine Magnetometer, capable of a plus or minus 0.1 gamma
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resolution, was used to perform a reconnaissance investigation for magnetic anomalies within
the investigation areas (Figure 10). The purpose of the magnetometer survey was to establish
the presence, and subsequent exclusion zones around any potential underwater wrecks,
submerged hazards, or any other features that would affect Phase III geotechnical
investigations as required by the BOEM Authorizations E13-002 and E13-003 (Appendix 8). The
magnetometer data collected in Phase II were combined with those data collected during Phase
III to identify any potential underwater wrecks, submerged hazards, or any other features that
would affect borrow area delineation and dredging activities.

Figure 10. Photograph of the Geometrics G-882 Digital Cesium Marine Magnetometer used to
investigate magnetic anomalies within the potential sediment source.

To produce a magnetic record of sufficient resolution, the sensor was deployed and maintained
in the water column no more than 6 m off the seafloor (approximately 19.7 ft). A digital
recorder provided a continuous permanent record of the magnetic background and target
signatures. Positioning data generated by the navigation system was tied to magnetometer
records by regular annotations to facilitate target location and anomaly analysis. Annotations
include line number, date and time of start and end of each line, and target identification.

Upon completion of the reconnaissance magnetometer survey, the data were examined by a
marine archaeologist, who provided a position along the survey line of the magnetic anomalies
and avoidance buffer for each of the subsequent geotechnical (vibracore) investigations.

Sub-bottom Reflection Profile Surveys: “Chirp” sub-bottom-reflection data is used to show
sedimentary stratigraphy and identify potential project-compatible sediment resources. The
use of chirp sub-bottom data allows common stratigraphic layers to be mapped throughout the
study area while determining the thickness and extent of potential project compatible
sediment.

An EdgeTech X-STAR SB-512i was used to conduct the seismic sub-bottom reflection profile
surveys (Figure 11).The X-STAR Full Spectrum Sonar is a versatile wideband FM sub-bottom
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profiler that collects digital normal incidence reflection data over many frequency ranges. This
instrumentation generates cross-sectional images of the seabed (to a depth of up to 50 ft. in
this survey). The X-STAR SB-512i transmits an FM pulse that is linearly swept over a full
spectrum frequency range (“chirp pulse”). The tapered waveform spectrum results in images
that have virtually constant resolution with depth. The Chirp systems have an advantage over
3.5 kHz and “boomer” systems in sediment delineation because the reflectors are more
discrete and less susceptible to ringing from both vessel and ambient noise. The full-wave
rectified reflection horizons are cleaner and more distinct than the half-wave rectified
reflections produced by older analog systems.

Figure 11. Photographs of the EdgeTech X-STAR SB-512i sub-bottom profiling system. (left)
shows the sub-bottom profiling system prior to deployment. (righ) shows the system being
deployed.

The X-STAR SB-512i, the newest model in the EdgeTech suite of Chirp Full Spectrum Sub-bottom
towfish, differs from the older X-STAR SB-512 (which had four (4) 6” diameter transducers) by
having a single 13” diameter low frequency transducer and a single 6.5” diameter high
frequency transducer. The new low frequency transducer provides more low frequency energy
at all pulse settings, which allows deeper penetration of seafloor sediments while at the same
time maintaining the high resolution of the original configuration.

In order to minimize noise related to the survey vessel and sea conditions, the sub-bottom
towfish (which operates as both the source and receiver for the sub-bottom system) was
deployed and towed behind the research vessel. The sub-bottom system was interfaced with
RTK via Hypack 2013® navigational software. The sub-bottom system was operated by the
Discover-SB® software program. At the start of the sub-bottom profiling survey, the sweep
frequencies of the outgoing pulse together with the different gain settings available within
Discover-SB® were adjusted to obtain the best possible resolution for the survey. The data was
continuously bottom-tracked to allow for the application of real-time gain functions in order to
have an optimal in-the-field view of the data. Automatic gain control (AGC) was used to
normalize the data by strengthening quiet regions/soft returns while simultaneously
A
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reducing/eliminating overly strong returns by obtaining a local average at a given point. A time-
varying gain (TVG) was used to increase the returning signal over time in order to reduce the
effects of signal attenuation.

All sub-bottom data was recorded on the acquisition computer’s hard disk and transferred to a
USB memory stick and/or portable hard drive at the end of each survey day to back-up raw
survey data. Notes regarding line name, time, event, and direction of collection were recorded
for the beginning and end of each survey trackline. Post collection processing of the sub-
bottom data was completed using Chesapeake Technology, Inc.’s SonarWiz.MAP +SBP®
software. This software allows the user to apply specific gains and settings in order to produce
enhanced sub-bottom imagery that can then be interpreted and digitized for specific
stratigraphic facies relevant to the project goals.

The first data processing step is to calculate the approximate depth of the reflector below the
sound source by converting the two-way travel time (the time in milliseconds that it takes for
the “chirp pulse” to leave the source, hit the reflector and return to the source) to feet by
utilizing an approximate value for the speed of sound through both the water and underlying
geology. For this survey, a detailed hydrographic and geologic sound velocity structure was not
available, so CPE geophysicists used an estimated sound velocity of 1.6 meters per millisecond
(m/ms) in order to convert two-way travel time to feet. This estimate is based on typical speed
of sound in sands and limestone typical of the study area.

CPE geophysicists then processed the imagery to reduce noise effects (commonly due to the
vessel, sea state, or other natural and anthropogenic phenomenon) and enhance stratigraphy.
This was done using the processing features available in SonarWiz.MAP +SBP®; AGC, swell filter,
and a user-defined gain control (UGC). The SonarWiz.MAP +SBP® AGC is similar to the Discover-
SB® AGC feature, where the data are normalized in order to remove the extreme high and low
returns, while enhancing the contrast of the middle returns. In order to appropriately apply the
swell filter and UGC functions, the sub-bottom data was bottom-tracked to produce an
accurate baseline representation of the seafloor. Once this was done through a process of
automatic bottom tracking (based on the high-amplitude signal associated with the seafloor)
and manual digitization, the swell filter and UGC were applied to the data. The swell filter is
based on a ping averaging function that removes vertical changes in the data due to towfish
movement caused by the sea state. The swell filter was increased or decreased depending on
the period and frequency of the sea surface wave conditions, however, special care was taken
during this phase to not remove, or smooth over geologic features that are masked by the sea
state noise. The final step was to apply the UGC. The SonarWiz.MAP +SBP® UGC feature allows
the user to define amplitude gains based on either the depth below the source, or the depth
below the seafloor. For this survey, the UGC was adjusted so that the gain would increase with
depth below the imaged seafloor (and not the source), mimicking a time-varying gain. The user
was able to remove the noise within the water column, increase the contrast within the
stratigraphy, and increase the amplitude of the stratigraphy with depth, accounting for some of
the signal attenuation normally associated with sound penetration over time.

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After data processing, sub-surface data interpretation was performed using SonarWiz.MAP
+SBP® software. Using the SonarWiz.MAP +SBP® platform, processed sub-bottom profile lines
were opened to digitally display the recorded sub-surface stratigraphy. Using the software’s
Sonar File Manager, color coded historic jet probe and vibracore descriptions were added
directly to the sub-bottom profiles. In general, green was used to represent layers with high to
very high potential, yellow was used to represent layers with moderate potential, and red was
used to represent layers of low potential. Shelly or gravelly layers were coded blue and layers
primarily composed of clay were coded dark gray. Using the vibracore descriptions as a guide,
the sub-bottom stratigraphy was interpreted and the depth of the top of marginal to poor
quality material was determined. The stratigraphic reflector that best correlated with this layer
was digitized (Appendix 9).

Sidescan Sonar Survey: Sidescan data is required to verify the location and extent of
unconsolidated sediment and to map ocean bottom features such as benthic habitats, exposed
pipelines, cables, underwater wrecks, potential cultural resources, etc. The sidescan survey was
conducted to identify features that may affect Phase III geotechnical investigations as required
by the BOEM Authourizations E13-002 and E13-003 (Appendix 8). The sidescan data collected
in Phase II were combined with those data collected during Phase III to identify any potential
underwater wrecks, submerged hazards, or any other features that would affect borrow area
delineation, introduce hazards to dredging, or adversely impact the environment.

During Phase II investigation, the EdgeTech 4200-HFL and EdgeTech 4125 sidescan sonar
systems were used (Figure 12). The switch to the 4125 was made after the 4200-HFL was
damaged during the survey. Both systems use full-spectrum chirp technology to deliver wide-
band, high-energy pulses coupled with high resolution and good signal to noise ratio echo data.
The sonar packages included a portable configuration with a laptop computer running
EdgeTech’s Discover® acquisition software. The EdgeTech 4200-HFL towfish is a 300/600 kHz
dual frequency towfish, which was run in high definition mode to collect sonar data at both
frequencies. The EdgeTech 4125 towfish is a 400/900 kHz dual frequency towfish, which was
run in high definition mode to collect sonar data at both frequencies. Dual frequency provides
a more complete sidescan return that aids interpolation at the outer portions of the swath,
which in turn provides a more complete data set.

During the Phase II investigations, the sidescan was towed from the survey vessel at a position
and depth that limited exposure to sources of interference and provided the best possible
record quality. The digital sidescan data was merged with positioning data (RTK GPS via Hypack
2013®). Position data appeared in the video display and was logged to disk for post processing
and/or replay. The acoustic data was recorded digitally.

Post collection processing of the sidescan data was completed using Chesapeake Technology,
Inc’s SonarWiz.MAP software. This software allows the user to apply specific gains and settings
in order to produce enhanced sidescan imagery that can be interpreted and digitized for
specific benthic habitat features and debris throughout the survey area. The first step in
processing was to import the data into the software and bottom track the data.
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Figure 12. Photographs of the EdgeTech 4200-HFL (left) and EdgeTech 4125 (right) sidescan
sonar systems.

Bottom tracking is achieved using an automated bottom tracking routine and in some cases
manual bottom tracking. This step provides the data with an accurate baseline representation
of the seafloor and eliminates the water column from the data.

After bottom tracking, the data was processed to reduce noise effects (commonly due to the
vessel, sea state, or other anthropogenic phenomenon) and enhance the seafloor definition. In
most cases automatic time-varying gain (TVG) is sufficient to provide the best imagery. Time-
varying gain divides the data into parallel swaths and equalizes backscatter of each swath to
create a normalized image highlighting contrast change throughout the image, which creates a
better mosaic and allows the processer to pick out areas with similar acoustic properties. In
areas with high levels of noise in the data it was necessary to apply automatic gain control
(AGC) which normalizes the data by strengthening quiet regions/soft returns while
simultaneously reducing/eliminating overly strong returns by obtaining a local average at a
given point.

Typically, bottom features such as hardbottom outcrops, artificial reefs, coral reefs, etc are
digitized on a line-by-line basis to allow for comparison of features along adjacent lines. In this
case, no such features were identified in the survey areas. Isolated contacts were identified,
and are included in the contact report included in Appendix 10.

Results and Discussion of Phase II:
During the reconnaissance investigation geophysical data (bathymetric, sub-bottom profiler,
sidescan sonar, and magnetometer) were collected along 60.0 nautical miles within Areas A, B,
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C, and S1 (Figure 4). The goal of the reconnaissance investigation was to 1) Define the extent of
sediment layers identified during Phase I evaluation of jet probe data and historic vibracore and
surface sediment data; 2) Develop a vibracore plan to be implemented during Phase III
investigations; and 3) Identify potential environmental or cultural resources for avoidance
during Phase III vibracore investigations as required by BOEM Authorization E13-002 and E13-
003.

Post processed bathymetric data collected during the Phase II investigations were used to
create color shaded relief imagery that were imported into GIS for further evaluation. Figures
13, 14, and 15 show the resulting bathymetric surfaces developed based on the reconnaissance
survey data in Areas A, B, and C, respectively.

Figure 13. Map showing the locations of tracklines surveyed and bathymetric data collected in
Area A during Phase II reconaissance geophysical survey and vibracores collected during Phase
III.

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Figure 14. Map showing the locations of tracklines surveyed and bathymetric data collected in
Area B during Phase II reconaissance geophysical survey and vibracores collected during Phase
III.

As previously mentioned, ground truthing of the sub-bottom profile data was accomplished
using historic jet probe and vibracore descriptions. Interpretations of the sub-bottom profile
seismographs using these historic data suggested the thicker parts of the shoals identified in
the bathymetric data had the highest likelihood of containing sufficient volumes of beach
compatible sand.

Sidescan sonar data collected during Phase II were used to identify any potential underwater
wrecks, submerged hazards, or any other features that would affect borrow area delineation,
introduce hazards to dredging, or adversely impact the environment. The spacing of the survey
tracklines for the Phase II survey did not provide 100% coverage of the survey area, therefore,
these data were used to conduct a preliminary assessment of the presence/absence of hazards
to dredging or environmentally sensitive areas within potential borrow areas.

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Figure 15. Map showing the locations of tracklines surveyed and bathymetric data collected in
Area C during Phase II reconaissance geophysical survey and vibracores collected during Phase
III.

Following the collection and analysis of the geophysical data (sub-bottom reflection,
bathymetry, sidescan sonar, magnetometer), a detailed plan to collect vibracores to target the
most promising sand resources within Areas A, B, and C was developed. Proposed vibracore
locations were developed throughout all three areas at spacings that would satisfy the North
Carolina Sediment Criteria. Priority locations were identified based on the interpretation of the
seismic data, which would be the first vibracores collected during the Phase III investigations.

As a condition of the BOEM Authorization to collect G&G surveys for the project, data collected
during the reconnaissance geophysical survey was used to identify potential environmental or
cultural resources for avoidance during Phase III vibracore investigations. An analysis of the
sidescan sonar data indicated no presence of hardbottom habitats or consolidated rock
exposures outcropping in the vicinity of the proposed vibracore locations. An analysis of both
sidescan sonar and magnetometer data was conducted by a marine archeologist to determine
presence/absence of anomalies with a potential for association with submerged cultural
resources. No such anomalies were identified in areas proposed for coring in Areas A or B. Two
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avoidance areas were identified in Area C based on magnetic and acoustic signatures
confirming a high potential for association with submerged cultural resources (Figure 15).

PHASE III INVESTIGATION

Phase III of the sand search included design level geotechnical and geophysical investigations, a
cultural resource investigation, and borrow area design. Between July 22 and August 4, 2014,
100 vibracores were collected to meet the one (1) core per 23 acres guidelines set forth in 15A
NCAC 07H .0312 (e). Figures 13, 14, and 15 show the locations of the vibracores collected
during Phase III.

Between October 18 and October 29, 2014, a concurrent sub-bottom profiling, sidescan sonar,
magnetometer, and bathymetric survey was conducted in a portion of Areas A and C. This
survey, when combined with the geophysical survey conducted during Phase II, provided both
design level geophysical information as well as satisfied permitting requirements to conduct a
cultural resource investigation. When combined with data collected during the Phase II
geophysical survey, data collected during Phase III achieved a line spacing of approximately 30
m (approximately 98 ft.). Figures 16 and 17 show the locations of the geophysical tracklines
surveyed during Phase III.

With regards to assessing beach compatible sand availability, these geophysical data were used
to map the extent of targeted sand resources and the upper elevation of marginal to poor
quality sediment (i.e. silt, clay, rock). The data were also used to identify potential cultural
resources such as artifacts, underwater wrecks, submerged hazards, significant relict landforms
or any other features including modern debris that would affect borrow area delineation and
dredging activities. A qualified marine archaeologist was onboard at all times during the Phase
III geophysical investigation.

Equipment and Methods
Geophysical Survey: The equipment and methods used for the Phase III geophysical
investigation were generally the same as described above in Phase II. However, the following
minor modifications were made to the methods described for Phase II. The survey was
conducted in such a manner to achieve total bottom coverage within the survey area using the
sidescan sonar. The line spacing of approximately 30 meters allowed for 100% overlap to be
obtained (i.e. all areas of the seafloor were covered twice). Once the sidescan sonar data was
sufficiently processed a mosaic was produced in the form of a geotiff. With regards to the sub-
bottom profile data, using the vibracore descriptions as a guide, the sub-bottom stratigraphy
was interpreted and the depth of the top of marginal to poor quality material was determined.
The stratigraphic reflector that best correlated with this layer was digitized (Appendix 9).

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Figure 16. Map showing the locations of geophysical tracklines surveyed and vibracores
collected during Phase II and III in preliminary investigation Area A.

Vibracore Survey: Vibracores were collected to obtain continuous physical samples of the
material within the potential sand resources. Data obtained from the analysis of these samples
are used to characterize the physical properties of the material and groundtruth the sub-
bottom data.

For areas located in Federal waters, prior to conducting the vibracore survey, CPE-NC was
required to apply for authorization from BOEM to conduct Geological Prospecting for Mineral
Resources on the Outer Continental Shelf Related to Minerals Other than Oil, Gas, and Sulphur.
BOEM granted the Authorization (E13-003) on July 11, 2014 (Appendix 8).
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Figure 17. Figure showing the locations of geophysical tracklines surveyed and vibracores
collected during Phase II and III in preliminary investigation Area C.

A condition of the Authorization granted by BOEM for the geophysical survey conducted during
Phase II (E13-002) required that the data must be reviewed by a qualified marine archaeologist
to verify that no cultural resources would be impacted. Likewise, the data was reviewed by
geophysisits, geologists, and environmental scientist to verify that no environmental resources
would be impacted. Vibracores were collected within 50 ft. of the as-run survey lines and
avoided areas identified by the marine archeologist as potentially significant.

The vibracores were collected using the 271B Alpine Pneumatic vibracore, configured to collect
undisturbed sediment cores up to 20 ft. in length (Figure 18). This self-contained, freestanding
pneumatic vibracore unit contains an air-driven vibratory hammer assembly, an aluminum H-
beam which acts as the vertical beam upright on the seafloor, 20-ft. long steel tubes measuring
4” in diameter (with a plastic core liner), and a drilling bit with a cutting edge. An air hose array
provides compressed air from the compressor on deck to drive the vibracore. The vibracore
unit was A-frame deployed from the M/V Thunderforce.

The navigation and positioning system deployed for this survey was a Trimble Differential
Global Positioning System (DGPS) interfaced to Hypack Inc.’s Hypack 2013®. A Pro Beacon
receiver provided differential GPS correction from the U.S. Coast Guard Navigational Beacon
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located at New Bern. The DGPS initially receives the civilian signal from the global positioning
system (GPS) NAVSTAR satellites. The locator automatically acquires and simultaneously tracks
the NAVSTAR satellites, while receiving precisely measured code phase and Doppler phase
shifts, which enables the receiver to compute the position and velocity of the vessel. The
receiver then determines the time, latitude, longitude, height, and velocity once per second.
Most of the time, the GPS accuracy with differential correction, provides for a position accuracy
of one (1) to four (4) ft. This is within the accuracy needed for geotechnical investigations. Top
of hole elevations were obtained from the bathymetric data collected during the Phase II
geophysical survey.

Figure 18. Photograph of A-frame Deployment of the 271B Alpine Pneumatic vibracore system
from deck of the M/V Thunderforce.

If recovery was less than 80% of the expected penetration, the pipe was removed, a new pipe
inserted, and a jet pump hose was attached just below the vibracore head. The rig was, again,
lowered to the bottom and jetted into the sediment just above refusal depth. The jet was then
turned off and the vibrator resumed collecting the lower part of the core. Ex. Core DCVC-14-01
had 50% recovery. In order to achieve the required 80% recovery, a jet was collected and
labeled DCVC-14-01A. Using the jetted section, a total recovered length of 16 ft was achieved
with a penetration of 20ft (80% recovery). Core DCVC-14-27 had 60% recovery. However, 12.3
ft of material recovered, only the uppermost 10.0 ft was potentially beach compatible making
the recovery acceptable. The lower 3.3 ft. was predominantly clay. Due to the nature of this
material, and the fact that this material would not meet state standards, additional recovery
would not result in the identification of additional sand resources.
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Upon removal of the vibracores, they were measured, marked and cut into 5 ft sections, each
vibracore was split onboard the vessel and field logged (Figure 19). This process of field logging
the cores allowed CPE-NC geologists to characterize the material obtained in each vibracore in
real time. The real time interpretation of these data allowed the CPE-NC team to tailor the
subsequent vibracore investigation to maximize the identification of compatable material and
minimize the number of vibracores taken in areas that contained in-compatable material.

After being field logged, the cores were wrapped, labeled, and transported to CPE-NC’s office in
Wilmington, North Carolina. There, the vibracores were logged by describing sedimentary
properties by layer in terms of layer thickness, color, texture (grain size), composition and
presence of clay, silt, gravel, or shell and any other identifying features (Figure ). Wet Munsell
color was determined in accordance with American Society for Testing and Materials Standard
Materials Designation D2488-00 for description and identification of soils (visual-manual
procedure) (ASTM, 2009). The vibracores were digitally photographed against an 18% gray
background; this is the standard reference value against which all camera light meters are
calibrated. Sediment samples were obtained from irregular intervals based on distinct layers in
the sediment sequence. Sediment samples underwent sieve analysis and carbonate analysis as
described above under Phase I methods. The unsampled half of each core was then archived.

Figure 19. Photograph showing vibracore field logging being conducted aboard the M/V
Thunderforce by CPE-NC geologists.

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Figure 20. Photograph showing vibracore logging, sub-sample collection and Munsell color
determination being conducted.

Results and Discussion
During this investigation, design level geotechnical and geophysical investigations were
conducted. The results of these investigations are discussed below. The geotechnical
investigation (vibracores) was conducted in such a way as to combine reconnaissance and
design into one mobilization. By field logging vibracores as they were obtained, CPE-NC
geologists tailored subsequent vibracore collection to maximize the identification of
compatable material and minimize the number of vibracores taken in areas that contained in-
compatable material.

Vibracores: Between July 22 and August 4, 2014, one-hundred (100) vibracores were collected
within the three investigation areas. Appendices 11 and 12 contain vibracore logs and
photographs. The granularmetric reports and grain size curves/histograms for the samples
collected from these vibracores are presented in Appendices 13 and 14, respectively.
Vibracores collected generally contained three (3) different types of sediments. The first type of
sediment consisted of fine to medium grained sand with trace silt, trace shell hash, and trace
shell fragments. Typical mean grain size of this sediment type range from 0.35 mm to 0.50 mm.
The second type consisted of fine sand with trace silt, trace shell hash, and trace shell
fragments with mean grain sizes ranging from 0.20 mm to 0.35 mm. The third general type of
sediment observed in the vibracores was sandy clays and silts. These three sediment types are
represented by the colors green, yellow, and red, respectively in the interpretations of the sub-
bottom data (Table 3). Other less frequently observed layers in the vibracores include shelly
sand with some shell fragments (coded blue), and layers that were primarily clay, with trace to
little sand (coded dark gray).

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Table 3. Vibracore color code scheme showing the range of sediment differentiation. Note
vibracores represented on the sub-bottom records provided in Appendix 9 are color coded based
on these discriptions.

Color Description

Green

Medium sand with trace silt (SP) (SW) (SW-SM) (SP-SM)
Yellow

Fine sand with trace silt (SP) (SW) (SW-SM) (SP-SM)
Red

Fine sand with little to some silt (SM) (ML)
Blue

Shelly sand with some shell fragments (SW) (SW-SM)
Dark Gray Primarily Clay, with trace to little sand (CL)

Analysis of the vibracore data resulted in the following characterizations of each of the three
investigation areas :

Area A:
Sediments recovered from vibracores in Area A display high potential for quality sand
resources. Sediments were generally fine to medium with trace silt and trace shell
fragments.

Area B:
Sediments recovered from vibracores in Area B displayed low potential for quality sand
resources. Sediments were generally fine with trace to little silt and trace shell fragments.
Deposits of usable sand tended to be relatively thin (less than 3 ft). Likewise, the relatively
thin sand deposits were underlain by predominantly clay and silt deposits not conducive to
beach fill in the project area. Due to the poor quality of sediment recovered in Area B,
further development of the area will not proceed at this time.

Area C:
Sediments recovered from vibracores in Area C displayed moderate to high potential for
quality sand resources. Sediments were generally fine to medium with trace silt and trace
shell fragments.

Following the collection and analysis of the vibracore data, investigation Areas A and C were
further delineated into proposed borrow areas (Figures 21 and 22). Due to relatively fine mean
grain size and high silt concentration in much of the material obtained in vibracores from Area
B, no borrow areas were proposed in that area. The proposed borrow areas A and B were the
areas surveyed during the Phase III geophysical survey. This survey, when combined with the
geophysical survey conducted during Phase II, provided both design level geophysical
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information as well as satisfied permitting requirements to conduct a cultural resource
investigation.

Figure 21. Map showing Proposed Borrow Area A. Proposed Design Area = 1,173 Acres,
Proposed Design Volume = 17,350,000 cy.

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Figure 22. Map showing Proposed Borrow Area C. Proposed Design Area = 354 Acres, Proposed
Design Volume = 2,049,000 cy.

Sub-Bottom Data: All vibracores collected during Phase III investigations were collected along
reconnaissance geophysical lines surveyed during Phase II as a condition of the BOEM
Authorizations. Following the analysis of the vibracore data, color-coded vibracore logs were
plotted directly onto the sub-bottom data using the SonarWiz.MAP +SBP software program.
Each vibracore was plotted on the line along which it was collected. The sub-bottom data was
then interpreted and digitized based on the correlated vibracore data. Figure 23 shows an
example of a seismograph with color coded vibracore logs superimposed upon it as well as
digitized seafloor and sub-bottom reflectors.

Following the post processing of the Phase III sub-bottom data and after those lines along
which vibracores were collected had been interpreted, geophysists interpreted and digitized
correlative reflectors along adjacent lines along which no vibracores had been collected. Once
all of the sub-bottom data had been interpreted and reflectors digitized, the data was exported
as a “Web” based project of HTML/JPEG files viewable in any standard web browser software
package (Appendix 9). In addition, an ASCII file was exported out of the SonarWiz.MAP + SBP
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program that when merged with bathymetry, creates sediment thickness isopachs used in
borrow area design.

Figure 23. Example image of seismograph overlain with digitized reflectors and vibracores to
enable seismic interpretations.

Sidescan Sonar Data: The sidescan sonar data collected was reviewed and used to identify
potential natural resources and potentially significant cultural resources. CPE-NC staff reviewed
the data specifically to locate potential bottom features and/or debris that should be avoided.
Based on the sidescan imagery, the locations of low relief sand ripples, large scale sand waves,
and potential mud patches were observed. Figures 24, 25, and 26 show examples of each of
these types of bottom features, respectively. Figures 27 and 28 show the extent of the sidescan
sonar coverage of Areas A and C, respectively. These sidescan sonar mosaics were developed
using the 600 kHz frequency data.

During interpretation of the sonar data, sonar contacts specifically identified as potential
bottom features of interest or marine debris were called out and contact sheets were
generated for each. The sidescan sonar contact sheets are included as Appendix 10. Figures 27
and 28 show the locations of these sonar contacts. Though some of the contacts are within the
limits of the proposed borrow areas, the individual features do not appear to be of a nature
that would affect borrow area design. A separate evaluation of the data was conducted by
Tidewater Atlantic Research (TAR) to identify potential cultural resourcse (Appendix 15). TAR
identified ten (10) sonar anomalies in the vicinity of Area A and eight (8) sonar anomalies in the
vicinity of Area C, which are shown on Figures 27 and 28, respectively.

Based on signatures of known substrate, the bottom material across the survey area is
predominately unconsolidated fine to medium grained sand overlaying unconsolidated and
semi-consolidated silty sand and sandy silty clays. Holocene sand deposits in the region form
large, high relief sand shoals. Superimposed upon these sand shoals are smaller scale sand
waves from 150 m to 275 m wide (Figure 24). These large scale sand waves, in general, trend
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northeast. Furthermore, small scale sand ripples are superimposed upon these sand waves in
some locations (Figure 25). Clustered mud patches can be seen on the western end of Area C
(Figure 26). These mud patches may be areas in which Holocene sediments have been eroded
away exposing pleistocene sediments.

Figure 24. Sonargraph showing large, high relief sand waves ranging in length from
approximately 150 meters to 275 meters in width.

Figure 25. Sonargraph showing small, low relief sand ripples ranging from approximately 13
meter in length to 1 meters in width.

Small scale sand ripples
Large scale sand waves
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Figure 26. Sonargraph showing potential isolated exposed mud patches with sand/gravel wave.
Isolated patches averaged at 40 meters long and 22 meters wide.

Exposed mud patches
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Figure 27. Sidescan sonar mosaic for Proposed Borrow Area A. The sidescan contact sheet ID’s
correspond to the sidescan sonar contact sheets found in Appendix 10.

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Figure 28. Sidescan sonar mosaic for Proposed Borrow Area C. The sidescan contact sheet ID’s
correspond to the sidescan sonar contact sheets found in Appendix 10.

Cultural Resources: To determine the projects effects on potentially significant submerged
cultural resources, TAR carried out a background literature review and supervised a cultural
resource investigation of the proposed borrow area. The cultural resource report compiled by
TAR is provided in Appendix 15.

Following the literature review, TAR supervised a magnetometer, sidescan sonar and sub-
bottom profile survey in the vicinity of the proposed borrow areas which was conducted by
CPE-NC in 2014. Analysis of remote sensing data collected during this investigation, identified a
total of nine (9) magnetic anomalies, four (4) of which were considered potentially significant
within the Preliminary Investigation Area A and a total of eight (8) magnetic anomalies, four (4)
of which were considered potentially significant within Proposed Borrow Area A. Analysis of
remote sensing data collected during this investigation, identified sixty-five (65) magnetic
anomalies, twenty-five (25) of which were considered potentially significant within Preliminary
Investigation Area C and a total of twenty-five (25) magnetic anomalies, seven (7) of which
were considered potentially significant within Proposed Borrow Area C. Avoidance buffers have
been applied to all potentially significant magnetic anomalies within Proposed Borrow Areas A
and C (Figure 27 and Figure 28).
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PROPOSED BORROW AREA DESIGN

Proposed borrow areas were designed that contained beach compatible material that meets
the State Sediment Criteria. Proposed Borrow Areas A and C were designed in investigation
Areas A and C, respectively. No proposed borrow area was developed within Area B or S1-4.
The proposed borrow area designs are shown in Figures 21 and 22.

Design Considerations
Design considerations for the proposed borrow areas included:

• Construction of the project using a Hopper Dredge
• Location of sufficient sand to construct the three proposed beach nourishment projects
for the Towns of Duck, Kitty Hawk, and Kill Devil Hills
• Beach compatible sand with similar mean grain size and sorting of the project beaches
• Avoidance of environmentally sensitive areas such as hardbottom, seagrass beds, etc.
• Avoidance of potentially significant cultural resources
• Avoidance of nearshore impacts due to wave refraction over borrow areas

Proposed Borrow Area A is located on the Outer Continental Shelf between 5.0 and 6.5 miles
offshore of the Towns of Kill Devil Hills and Nags Head in water depths between 50 and 60 ft.
(NAVD88). The proposed borrow area covers 1,173 acres and contains approximately
17,350,000 cy of sand. The proposed borrow area is broken up into six (6) different cuts with
cut depths ranging from -58.5 to -68.0 ft. NAVD88. Additionally, three (3) dredge avoidance
buffers have been added to the proposed borrow area design that represents potentially
significant cultural resources (Figure 21).

Proposed Borrow Area C is located on the Outer Continental Shelf between 4.1 and 5.2 miles
offshore of the Town of Duck in water depths between 55 and 65 ft. (NAVD88). The proposed
borrow area covers 354 acres and contains approximately 2,049,000 cy of sand. The proposed
borrow area is broken up into five (5) different cuts with cut depths ranging from -61.0 to -65.0
ft. NAVD88. A no dredge zone is shown in the middle of proposed Borrow Area C where
potentially unsuitable material exists. Additionally, six (6) dredge avoidance buffers have been
added to the proposed borrow area design that represent potentially significant cultural
resources, and a no-dredge area identified due to the quality of the material in that particular
section (Figure 22).

Composite mean grain size, percent silt content and sorting were computed for each vibracore
within Proposed Borrow Areas A and C by calculating the weighted average (sample weighted
by representative lengths of the sampled layer within the core) and are included in Appendices
16, 17 and 18. The composite statistics for the entire proposed borrow area were compiled by
averaging the weighted results for all cores within the lateral and vertical limits of the proposed
borrow area. The grain sizes of the fill materials are based on the geotechnical investigations
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for the proposed borrow areas. The proposed borrow area composite statistics are shown in
Table 4.

Table 4. Borrow Area characteristics.

Location Mean Grain Size1 Sorting1 Silt2
(mm) (phi) (phi) (%)
Proposed Borrow Area A

0.36 1.47 0.90 0.83
Proposed Borrow Area C

0.28 1.83 1.09 1.36

1 Sieve analyses were conducted on all sediment samples in accordance with American
Society for Testing and Materials Standard Materials Designation D422-63 for particle size
analysis of soils. Grain size data were entered into the gINT® software program, which
computes the mean and median grain size, sorting, and silt/clay percentages for each
sample using the moment method (Folk, 1974).
2 Silt content is defined as the percentage of material finer than 0.0625 mm.

Data Quality
Data collection utilized industry standard survey systems and methodologies to collect high
resolution and high quality geophysical and geotechnical data. Geophysical surveys (sidescan
sonar, sub-bottom profile, magnetometer, and bathymetric) were conducted at 30 meter line
spacing and tie lines throughout the proposed borrow area. Vibracores were collected at
approximately 1000 ft. spacing throughout the areas. Despite the resolution of the geophysical
and geotechnical data, it is possible that interpolations between lines and vibracores may result
in unexpected material (rock, silty sand, clay, etc.) in the borrow area. Dredge and fill
operations should be monitored in real time to ensure the quality of the material placed on the
beach and if unsuitable material is encountered, dredge practices should be modified to avoid
such isolated areas of unsuitable material.

The borrow areas tend to contain coarser grained sediment grading into finer grained
sediments with depth. Percent fines increase with depth as well. Borrow Area composite
sediment data included herein represents all material contained within the horizontal and
vertical limits. Given the distance between the proposed borrow areas and the project areas
hopper dredges will most likely be used for the construction of the projects. However, the
project is being permitted to allow both hopper dredges and cutterhead suction dredges.
Excavation of the borrow area using a hopper dredge, which typically excavates shallow layers
of sand from the upper portion of a defined sand deposit, may result in the placement of sand
with a mean grain size coarser than composites listed herein. Conversely, the use of a
cutterhead suction dredge, which typically dredges deeper deposits of sand throughout the
defined sand deposit, would result in the placement of sand with a mean grain size comparable
to the composite listed herein.
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Compatibility Analysis
The compatibility of the proposed borrow areas designed by CPE-NC as a result of this
investigation (Proposed Borrow Areas A and C) were evaluated with regards to beach
sediments along the Towns of Duck, Kitty Hawk, and Kill Devil Hills, North Carolina. The analysis
considered color, silt content, granular content, gravel content, and carbonate content.
Composite mean grain size, percent silt, percent granular, percent gravel, percent carbonate,
and sorting were computed for each vibracore by calculating the weighted average (sample
weighted by representative lengths of the sampled layer within the core). The summary
composite tables for the proposed borrow areas are provided in Appendix 16. Composite
granularmetric and grain size distribution curves/histograms for each core are provided in
Appendices 17 and 18. The composite statistics for the proposed borrow areas were compiled
by averaging the weighted results for all cores within the lateral and vertical limits of the
borrow area (Appendix 16). The existing beach composites for Duck, Kitty Hawk, and Kill Devil
Hills are based on samples collected by CPE-NC in 2013 and 2014, supplemented with samples
collected by the USACE. Composite mean grain size, percent silt, percent granular, percent
gravel, percent carbonate content and sorting for the existing beach are provided in Appendix
4. Composite granularmetric and grain size distribution curves/histograms for the existing
beach at Duck, Kitty Hawk, and Kill Devil Hills are provided in Appendices 5 and 6. The summary
results are shown in Table 5.

Table 5. Beach and proposed borrow area characteristics.

Borrow
Area/Beach
Average
Shell Hash1
Carbonate
Content2
Mean
Grain Size3

Sorting3

Silt4
Average Wet
Munsell
(%) (%) (mm) (phi) (phi) (%) Color Value5
Proposed
Borrow Area A 1 0.36 1.47 0.90 .83 5

Proposed
Borrow Area C
8 0.28 1.83 1.09 1.36 5
Duck 2 0.33 1.58 1.32 1.01 5
Kitty Hawk 2 0.38 1.38 1.41 0.94 5
Kill Devil Hills 2 0.36 1.47 1.37 0.90 5

1 During sieve analysis, the visually estimated percentage of shell on the #5 and #7 sieves was noted.
2 Carbonate content was determined by percent weight on thirty-one (31) samples using the acid
leaching methodology described in Twenhofel and Tyler (1941).
3 Sieve analyses were conducted on all sediment samples in accordance with American Society for
Testing and Materials Standard Materials Designation D422-63 for particle size analysis of soils. Grain
size data were entered into the gINT® software program, which computes the mean and median grain
size, sorting, and silt/clay percentages for each sample using the moment method (Folk, 1974).
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4 Silt content is defined as the percentage of material finer than 0.0625 mm (F.A.C. 62 B-41.007).
5 Wet sand colors were evaluated using the Munsell color system. The Munsell notation for color
consists of separate notations for Hue (combination of red, yellow, green, blue, and purple colors),
Value (lightness of the sand color) and Chroma.

Color: Wet sand colors are evaluated using the Munsell color system. The Munsell notation for
color consists of separate notations for Hue, Value and Chroma, which are combined in that
order to form the color designation. Hue indicates the combination of red, yellow, green, blue,
and purple colors. Value indicates the lightness of the sand color. A higher number indicates a
lighter sand sample. Chroma indicates the intensity of the color. A higher number indicates a
more intense color.

Of these parameters, the most important for beach nourishment is Value. Based on existing
data, the existing beach sand is light gray and exhibits a typical wet Munsell color value of 5 for
the Towns of Kitty Hawk, Kill Devil Hills and forthe Town of Duck. The fill material is light gray,
with an average wet color value of 5. The Hue of the existing beach and the Proposed Borrow
Areas are a mix of 2.5Y and 5Y. The Chroma of the existing beach and fill material range
between 1 and 2 for both. This indicates that the existing beach color is very similar to the fill.
The Munsell value of the fill material is similar to the existing beach.

Carbonate Content: The average carbonate content of the existing beach at Duck, Kitty Hawk,
and Kill Devil Hills ranges from 2%, 2%, and 2%, respectively. The average carbonate content of
Proposed Borrow Areas A and C are 1% and 8%, respectively. The carbonate content of the
borrow area is within tolerance of the State limit defined in Rule 15A NCAC 07H .0312, which
states that the borrow source shall not exceed the average percentage by weight of calcium
carbonate of the recipient beach characterization plus 15%. In this case, the limit is 17% for
Duck and Kitty Hawk and Kill Devil Hills.

Fines: In this analysis, percent fine is defined as the percentage of material finer than 0.0625
mm as defined by Rule 15A NCAC 07H .0312. The average percent fines in Proposed Borrow
Area A is 0.83% and 1.36% in Proposed Borrow Area C, which is well below the State limit of 5%
defined for beach fill projects. The beach samples exhibit silt content of 1.01% in the Town of
Duck, 0.94% in the Town of Kitty Hawk, and 0.90% in The Town of Kill Devil Hills. The silt
content of the fill material falls within this range and is acceptable as beach quality material.

Granular: In this analysis, granular content is defined as the percentage of material greater
than or equal to 2.0 mm and less than 4.76 mm as defined by Rule 15A NCAC 07H .0312. The
composite granular content of the proposed Borrow Areas A and C are 1.48% and 2.21%,
respectively. The composite granular content of the beach at Duck, Kitty Hawk, and Kill Devil
Hills are 3.89%, 6.38%, and 5.15%, respectively (Table 6). The granular content of the proposed
borrow areas is above the State limit which states that the granular content shall not exceed
the average percentage by weight of granular-sized sediment of the recipient beach
characterization plus 5%. In this case the limit is 8.89% for Duck, 11.83% for Kitty Hawk, and
10.15% for Kill Devil Hills.
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Gravel: In this analysis, gravel content is defined as the percentage of material greater than or
equal to 4.76 mm and less than 76 mm as defined by Rule 15A NCAC 07H .0312. The composite
gravel content of the proposed Borrow Areas A and C are 0.52% and 1.09%, respectively. The
composite gravel content of the beach at Duck, Kitty Hawk, and Kill Devil Hills are 2.00%, 1.64%,
and 1.62%, respectively (Table 6). The gravel content of the proposed borrow areas is above the
State limit which states that the gravel content shall not exceed the average percentage by
weight of gravel-sized sediment of the recipient beach characterization plus 5%. In this case
the limit is 7.00% for Duck, 6.64% for Kitty Hawk, and 6.62% for Kill Devil Hills.

Table 6. Allowable fine, granular, gravel, and carbonate limits defined by State rules.

Borrow Area

Fines

Granular

Gravel

Carbonate
(%) (%) (%) (%)
Allowable limits defined by
Rule 15A NCAC 07H.0312
(Town of Duck)
6.01 8.89 7.00 17
Allowable limits defined by
Rule 15A NCAC 07H.0312
(Town of Kitty Hawk)
5.94 11.83 6.64 17
Allowable limits defined by
Rule 15A NCAC 07H.0312
(Town of Kill Devil Hills)
5.90 10.15 6.62 17
Proposed Borrow Area A 0.83 1.48 0.52 1
Proposed Borrow Area C 1.36 2.21 1.09 8

Grain Size: Grain size compatibility is quantified using the overfill factor, which indicates the
proportion of sand required to compensate for differences between the grain size distributions
of the proposed borrow area sediment and the existing beach. An overfill factor of 1.0 indicates
that no extra sand is required. An overfill factor of 1.28 indicates that the sand volume must be
increased 28% to achieve the same performance as material identical to the existing beach, etc.
In general, the overfill factor decreases as the mean grain size of the borrow source increases
towards the grain size of the existing beach.

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CONCLUSIONS

The marine sand search investigation conducted by CPE-NC in 2014 on the outer continental
shelf of Dare County, North Carolina resulted in the design of two proposed borrow areas.
Table 7 summarizes the geophysical and geotechncical data collected in support of this
investigation. Proposed Borrow Area A is located on the Outer Continental Shelf between 5.0
and 6.5 miles offshore of the Towns of Kill Devil Hills and Nags Head in water depths between
50 and 60 ft. (NAVD88). The proposed borrow area covers 1,173 acres and contains
approximately 17,350,000 cy of sand. The mean grain size of the sand is 0.36 mm with a sorting
value of 0.90. Sand is characterized as fine to medium grained quartz sand with trace silt, shell
hash, and shell fragments. The average wet Munsell color value is 5 and dry color value is 6.
The borrow area is broken up into 6 different cuts with cut depths ranging from -58.5 to -68.0
ft. NAVD88.

Table 7. Geophysical and geotechnical investigations conducted in 2014.

Proposed Borrow Area C is located on the Outer Continental Shelf between 4.1 and 5.2 miles
offshore of the Town of Duck in water depths between 55 and 65 ft. (NAVD88). The proposed
borrow area covers 354 acres and contains approximately 2,049,000 cy of sand. The mean
grain size of the sand is 0.28 mm with a sorting value of 1.09. Sand is characterized as fine
grained quartz sand with trace silt, shell hash, and shell fragments. The average wet Munsell
color value is 5 and dry color value is 6. The proposed borrow area is broken up into 5 different
cuts with cut depths ranging from -61.0 to -65.0 ft. NAVD88.

The compatibility of the proposed borrow areas with the existing beaches was evaluated
according to wet Munsell color, percent fine-size sediment, percent granular-size sediment,
percent gravel-size sediment, carbonate content and grain size. For the proposed borrow areas
all values meet the allowable limits defined by Rule 15A NCAC 07H .0312.

Reconnaissance level total nautical miles surveyed
(bathymetric and magnetometer) 60.0
Number of CPE-NC vibracores collected 100
Design level total nautical miles surveyed
(bathymetric, magnetometer, sub-bottom and sidescan sonar) 170.2
Number of proposed borrow areas identified 2
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COASTAL PLANNING & ENGINEERING OF NORTH CAROLINA, INC.
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ACKNOWLEDGEMENTS

Geophysical data was collected by Jeff Helgerson, Franky Stankiewicz, Ben Alcocer, Alex
Valente, Natasha Flores, Scott Tillman, Chris Dougherty, Tim Moss, Adam Priest, and Stephanie
Bush. Vibracores were collected by Adam Priest, Brant Priest, Ken Willson, and Tim Moss.
Vibracores were logged and compiled by Kristina McCoy, Leah Colombo, Brant Priest, Tim Moss,
and Stephanie Bush. The project manager was Ken Willson. The project geologist was Kristina
McCoy.

LITERATURE CITED

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Philadelphia: American Society for Testing Materials.

ASTM, 2006. Standard methods for amount of material in soils finer than No. 200 (75 um) sieve,
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Bodge, K.R., 2004. Alternative Computation of Dean’s Overfill Ratio, 17th Annual National
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