20041216 Ver 1_CAMA Application_20040726

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Michael F. Easley, Governor Charles S. Jones, Director William G. Ross Jr., Secretary
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NCDENR
North Carolina Department of Environment and Natural Resources
Division of Coastal Management
July 22, 2004
MEMORANDUM:
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TO: John R. Dorney
Environmental Biological Supervisor
Division of Water Quality
FROM: Doug Huggett
Major Permits Processing Coordinator
WETLANDS / 4Q1 GRQUP
JUL 2 6 2004
WarE~ t~u~~i r~r s~cr~a-u
SUBJECT: CAMA/DREDGE & FILL Permit Application Review
Applicant: New Hanover County
Project Location: New Hanover County, Mason Inlet, between Figure 8 Island and Wrightsville
Beach.
Proposed Project: .Proposes to maintenance excavate Mason Inlet.
Please indicate below your agency's position or viewpoint on the proposed project and return this form
by August 12, 2004. If you have any questions regarding the proposed project, please contact Ed
Brooks at [phone]. When appropriate, in-depth comments with supporting data is requested.
REPLY: This agency has no objection to the project as proposed.
This agency has no comment on the proposed project.
This agency approves of the project only if the recommended changes are
incorporated. See attached.
This agency objects to the project for reasons described in the attached comments.
SIGNED DATE
127 Cardinal Drive Ext., Wilmington, North Carolina 28405-3845
Phone: [phone] FAX: [phone] Internet: www.nccoastalmanagement.net
An Equal Opportunity 1 Affirmative Action Employer - 50% Recycled 110% Post Consumer Paper

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DIVISION OF COASTAL MANAGEMENT
FIELD INVESTIGATION REPORT
1. APPLICANT' S NAME:. New Hanover County/Mason Inlet 1St Maintenance
2. LOCATION OF PROJECT SITE: Mason Inlet, between Figure 8 Island and Wrightsville Beach,
in New Hanover Co.
Photo Index - 1998: 11-224 & 226 1995: 24-29 1989: 5176-21 & 22
State Plane Coordinates - X: 2371651 Y: 182526 Rover file: S-071618A
3.
4.
5.
INVESTIGATION TYPE: CAMA/D&F
INVESTIGATIVE PROCEDURE: Dates of Site Visit - 7/16/04
Was Applicant Present -Yes
PROCESSING PROCEDURE: Application Received - 6/24/04
Office -Wilmington
6. SITE DESCRIPTION:
(A) Local Land Use Plan -New Hanover Co.
Land Classification From LUP -Conservation
(B) AEC(s) Involved: EW, PT, OH, and CW
(C) Water Dependent: Yes
(D) Intended Use: Public/Private
(E) Wastewater Treatment: Existing - N/A
Planned -None
(F) Type of Structures: Existing -None
Planned -None
(G) Estimated Annual Rate of Erosion: N/A
Source - N/A
7. HABITAT DESCRIPTION: ~ [AREA]
T)RF.T~CTF,T) FTT,T,F,D
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OTHER
(A) Vegetated Wetlands
(B) Non-Vegetated Wetlands -
Shallow bottom and inter-tidal flats 629,000 sgft
Inter-tidal beach area dis osal 1,293,732 sgft
(C) Other- Upland (accreted inlet shoulder) 199,500 sgft
Upper beach disposal 646,866 sgft
(D) Total Area Disturbed: 2,984,720 sgft (68.5 acres)
(E) Primary Nursery Area: No
(F) Water Classification: SA-ORW Open: Yes

New Hanover Co./Mason Inlet 1st Maintenance Project
Page 2
8. PROJECT SUMMARY
In 2001, New Hanover County obtained the State acid federal permits to relocate Mason Inlet
approximately 3,000 feet to the northeast. The relocation of the inlet was completed in March 2002. As
required by the permits, the County implemented a monitoring and maintenance plan that would ensure
the stability of the inlet location over a 30-year period. In accordance with the permitted Inlet
Management Plan, monitoring data indicates that sedimentation within the inlet system has now reached
the point that initiates a maintenance event.
9. PROJECT DESCRIPTION
Mason Inlet is located between Wrightsville Beach (south) and Figure 8 Island (north), in New Hanover
County. By 1996, the southern migration of Mason Inlet presented an erosion threat to the development
on the northern end of Wrightsville Beach, including the multi-story Shell Island Resort complex, the
terminus of North Lumina Avenue, as well as, potentially numerous single-family and multi-family
residential structures located to the south. In 2001, New Hanover County obtained the State (#151-01)
and federal (#199901052) permits to relocate Mason Inlet approximately 3,000 feet to the northeast. The
relocation of the inlet was completed in March 2002. In accordance with the permitted Inlet
Management Plan (IMP), the County implemented a monitoring and maintenance plan (Appendix C)
that would ensure the stability of the inlet location over a 30year period. Maintenance events were
projected to occur at 3-5 year intervals and would consist of the dredging of Mason Creek, the
sedimentation basins and the inlet channel to re-establish the design template for the relocated inlet. The
excavated sediments would be placed on the adjacent updrift and downdrift beaches. The IMP includes
three (3) triggers that would initiate a maintenance event:
1. volumetric losses along the oceanfront shorelines of Figure 8 Island and/or Wrightsville
Beach
2. the sedimentation of Mason Inlet and/or the designed sedimentation basins
3. inlet migration outside of the designed inlet corridor
Monitoring data indicates that Trigger 2 has been initiated and as such, the County has submitted this
application for maintenance of the inlet.
In the project area, the NC Division of Water Quality classifies the Atlantic Ocean as SB, and'the waters
of Mason Creek as SA-ORW. The waters of Mason Creek are OPEN for the harvest of shellfish.
Although the saltmarshes on either side of the project area are designated as Primary Nursery Area
(PNA) by the NC Division of Marine Fisheries, the open waters of Mason Inlet and Mason Creek are
excluded from the surrounding PNA classification.
The applicant's analysis ofpost-project survey data indicates the need to modify the permitted maintenance
protocol from the original IMP. The data showed that the projected 375,000 cy ofmaterial that was predicted
to enter the system within the first 4-5 year period, actually did so within 9 months of project completion.
Also, surveys indicated that the majority of this material was primarily derived from the southern 3,000 feet

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New Hanover Co./Mason Inlet 1st Maintenance Project
Page 3
of the updrift shoreline (Figure 8 Island). The applicant's consultant, Gahagan & Bryant Associates, Inc.
(GBA), states that this shoaling rate was a result of the formation of the inlet's flood-tide delta, which was
not considered in the pre-project estimates of sediment deposition. GBA further states that during year 2,
following flood ebb-tidal delta development, the recorded shoaling rates were similar to those predicted from
pre-project data. It is reasonable to expect that if the original inlet design template were to be re-established
as currently permitted, then a similar episode of .massive shoaling would occur in the same location
following the maintenance event. To address the excessive shoaling within the inlet and the associated
erosion of the updrift shoreline observed after initial construction, the applicants .developed several
alternative maintenance dredging plans and compared the predicted responses of each scenario .using
hydrodynamic modeling (Appendix D). The alternative that proposes dredging only within Mason Creek
produced the most favorable erosion/deposition conditions and inlet stability. This scenario would promote
inlet stability by leaving the existing. flood-tide delta in place to prevent post-project erosion of the updrift
oceanfront shoreline and its reduced scale lessens the environmental impacts associated with dredging the
entire design template of the project. The applicant proposes to modify their permit to incorporate this
alternative into their inlet maintenance strategy.
The proposed maintenance project has two distinct areas of excavation, the accreted inlet shoulder on the
southern end of Figure 8 Island and Mason Creek. The excavation of the inlet shoulder on Figure 8
Island would be a land-based operation, using mechanical excavators and off-road. dump trucks. This
area is located within the inlet channel and sedimentation basins of the design template and is
approximately 1,500 feet long and between 200 - 500 feet wide. Excavation depth would be -3.0 feet at
mean low water (MLV~. The excavated material would be hauled along the shoreline to the nourishment
area, which is a 4,500 linear foot section of beach, starting 1,200 feet from the inlet shoulder and
extending north. The mechanically excavated material would be used to reconstruct the eroded berm to
its design dimensions (Elev. 14' NGVD and 40' crest width) and approximately 50 feet of the slope
seaward of the berm crest (7' NGVD). The Mason Creek portion of the project would be dredged to the
design template (3400' long and 80' wide, to -10' MLV~ using a hydraulic pipeline dredge. These
excavated materials would be pumped to the shorefront slope of the nourishment area and bulldozers
used to grade the material to the design slope. The resulting beach profile, after reaching equilibrium, is
expected to produce an additiona170 - 90 foot width to the upper beach with an elevation sloping from
14 to 7 feet NGVD and extend at a 1:30 slope into the near shore surf zone, approximately 200 - 400 feet
beyond mean low water.
10. ANTICIPATED IMPACTS
The maintenance excavation of the Mason Creek channel by hydraulic pipeline dredge would disturb
272,000 square feet (6.2 acres) of sandy, shallow bottom. The mechanical excavation of the inlet shoulder
area would convert 199,500 square feet (4.6 acres) of accreted uplands and 357,000 square feet (8.2 acres) of
inter-tidal flats back to inlet channel. The project would produce approximately 184,000 cubic yards of
beach quality sand that would be placed on the southern end Figure 8 Island. The deposition of this material
would disturb 2,156,220 square feet (49.5 acres) of upper beach and inter-tidal zone along 4,500 linear

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New Hanover Co./Mason Inlet 1st Maintenance Project
Page 4
feet of oceanfront shoreline. The proposed project modification is designed to prevent the large-scale,
inlet-induced erosion of the updrift beach that followed the initial project construction. The smaller scale
of the proposed modification reduces the area impacted, while promoting a more stable inlet
configuration.
An area of concern is the combined effect of the use of contiguous beach nourishment areas with the
adjacent Figure 8 Island Banks Channel project. However, GBA states that the combined total of both
proposed projects (410,OOOcy over 10,000 LF of beach) is 100,000 cubic yards less than the quantity of
sand that would be placed on the beach, if the Mason Inlet project were to be excavated to the design
template, as previously reviewed and permitted from the Inlet Management Plan. Also, the combined
nourishment would not exceed the State's deposition rate standard (50 cy/LF) for small-scale beach
nourishment projects.
It should also be noted that the hydrodynamic and sediment transport modeling analyses of the
maintenance alternative proposed in this application, also included a dredging component that proposed
connecting Mason Inlet. with Banks Channel. Based on model results, the proposed modification plus a
connection to Banks Channel would be the most favorable system for inlet stability. This scenario would
reduce shear stress patterns, sediment transport and AIWW and Banks Channel shoaling, while
maintaining existing tidal exchange rates (See Appendix D). During a preliminary meeting with
USACOE and NCDCM staff (5/6/04), it~was determined that excavation between the inlet and Banks
Channel would require significant review by both State and federal agencies. Given the urgency and
need to perform maintenance of the inlet and the time constraints associated with permitting of a
dredging connection to Banks Channel, the applicant has opted to limit the proposed modification to the
dredging of Mason Creek and the excavation of the inlet shoulder on the north side of the inlet channel
and sedimentation basins. The applicant will likely seek a subsequent modification, in the interim
between this work and the next maintenance event, to address the potential connection to Banks
Channel
Submitted by: E.F. Brooks Date: 7/19/04 Office: Wilmington

1
September 3, 2004
North Carolina
Coastal Federation
Henry Wicker
U.S. Anny Corps of Engineers -Wilmington District
P. O. Box 1890
Wilmington, North Carolina 28402-1890
Doug Huggett
Major Permits Coordinator
North Carolina Division of Coastal Management
1638 Mail Service Center
Raleigh, NC 27699-1638
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WETLANDS 1401 GR~~P
SEP 1 4 2004
~NATER (~UAL1T`! S~CT10~
Re: New Hanover County application for a maintenance dredge event under Department of the Army
(DA) permit # 199901052 and a Coastal Area Management Act (CAMA) Modification under Major
Permit #: 151-O1 to maintenance dredge Mason Inlet and Mason Creek and place the material on
Figure 8 Island for beach nourishment
Dear Mr. Wicker and Mr. Huggett:
The North Carolina Coastal Federation (NCCF) has reviewed the US Army Corps of Engineers (USAGE)
Public Notice (PN) for the application for a maintenance dredge event under Department of the Army (DA)
permit # 199901052 and the Coastal Area Management Act (LAMA) Modification application under Major
Permit #:151-01 to maintenance dredge Mason Inlet and Mason Creek and place the material on Figure 8
Island for beach nourishment.
.NCCF represents approximately 8,000 members across coastal North Carolina and participates actively in all
facets of regulatory and environmental protection activities affecting, the state's coast. NCCF has a long
history of environmental advocacy regarding the beachfront and estuaries of the Southeastern coastal area
and other segments of the North Carolina coastline, and appreciates the opportunity to submit these
comments.
The proposed project, as outlined in the DA PN and CAMA Major Permit Application, includes maintenance
dredging of 58,000 cubic yards (cy) from Mason Creek, and 126,000 cy from the inlet shoulder and sediment
basin at Mason Inlet with material placed along 10,000 feet of the Figure 8 Island beach as authorized under
DA permit # 199901052. This is described as the first maintenance event under the USAGE permit
authorizing maintenance until December 31, 2031. The stated purpose of the proposed project is to maintain
Mason Inlet within its 1000-foot corridor. Annual dredging is described as potentially necessary to minimize
environmental impacts and the movement of the inlet.
NCCF comments on the proposed application for the project focus on two components of the Mason Inlet
Relocation Project. The first portion of NCCF's comments focus on the proposed maintenance dredge event.
"Citizens ~1/orkirl~~ To~etl~er For A NP~ldrl y Coast"
NCCF Headquarters Phone: [phone] • Fax: [phone] • Email: [e-mail] • Website: www.nccoast.org
Field Office Phone: [phone] • Fax: [phone]
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NCCF Headquarters: 3609 Highway 24 (Ocean) Newport, NC 28570
Field Office: 3806-B Park Avenue, Wilmington, NC 28403

The second portion of the comments focus on the status and compliance with the original authorized DA and
CAMA Permits, NCDWQ 401 Water Quality Certification, and USFWS Biological Opinion (BO).
I. As stated in the project description contained in the permit application file and DA PN, New
Hanover County is seeking authorization to conduct the first maintenance event for the Mason Inlet
Relocation Project. This project is proposed to occur during the 200405 dredging period.
The project description states that Trigger 2, which uses specific shoaling rates to determine when a
maintenance event needs to occur, as described in the Inlet Maintenance Plan (IMP) has been initiated. The
proposed maintenance event is described as a modification of the existing maintenance protocol to adapt to
the shoaling rates and morphologic change of the inlet system. The proposed modification is described as
potentially more cost effective and environmentally sound approach.
The proposed maintenance event is described as having two distinct excavation sections consisting of the
southern end of Figure 8 Island and Mason Creek. The originally relocated inlet channel and created
sediment basin are described as extensively shoaled. The proposed excavation will be performed
mechanically; using land based equipment and hauled by truck to the nourishment areas. The material
excavated from this area will be placed on the upland portion of the nourishment azea, including the eroded
dune azea. Within Mason Creek the material will be dredged hydraulically and placed along the shore face of
the nourishment area and beyond mean low water. It is estimated that 186,000 cy yards of beach quality
material sand will be excavated from a 22.6-acre tract within the inlet channel, sediment basin and Mason
Creek. The material will be placed along a 4,500 lineaz foot section of the Figure 8 Island beach starting
approximately 1,200 feet from the inlet shoulder, extending north. It is estimated that the proposed
nourishment azea will be approximately 49.5 acres, extending from the existing dune line to approximately
200 feet below mean low water.
The proposed modification to the maintenance plan is described as keeping the main portion of the inlet
flood delta intact and performing dredging operation in specific areas with limited depths. The proposed
maintenance approach is proposed as seeking to reduce environmental impacts associated with large-scale
dredging of the entire system (sediment basin and channel segments), while producing a more stable inlet
configuration. With the proposed modification, the overall projected impacts from the original design
template are lowered from a total of 5.7 acres of supratidal habitat to 4.2 acres; 16.9 acres of intertidal
habitat to 8.0 acres; and 20.7 acres of subtidal habitat to-10.4 acres. The overall total impacts to tidal
habitats are lowered from 43.3 acres to 22.6 acres.
It is commendable that the County and its engineers, Gahagan and Bryant, have examined project
alternatives to.seek a maintenance dredge event with potentially reduced costs and environmental impacts. It
is appazent that an effort has been made to comply with the 404 B (1) guidelines for avoidance and
minimization of impacts to the resources. This approach is encouraged by NCCF. However, there are several
questions and concerns with the proposed maintenance event that should be addressed.
The project description outlines the methods for land-based excavation of the shoal area from the southern
end of Figure 8 Island. An excavator and dump trucks will be used to.move the shoal material. It is not stated
if the material, once excavated will be stockpiled then loaded into the trucks. If it all possible, the material
should be placed directly into the dump trucks to reduce "double handling" and impacts on the beach and
inlet shoulder areas.
The pipeline carrying material from the dredge operating in Mason Creek will be routed along the shoreline
of Mason Creek along the north corridor limit. Per DA Permit Condition # 10 "The pelmittee shall not
impact mature marsh on north side of Mason Creek", every effort should be made to ensure the pipeline does
NCCF Comments
Mason Inlet Maintenance
09/09/04 2

not impact the marsh along Mason Creek through its placement or by leaking material from the pipe.
The proposed beach disposal area has been the site for beach disposal and beach scraping resulting from a
number of projects in 2002, 2003 and 2004. The proposed project represents the fourth consecutive year that
this area of beach will have been significantly impacted from beach activities. The cumulative impacts to the
beach, in particular benthic species; mole crabs and coquina clams, from successive. projects need to be
considered when reviewing this permit application: While research indicates that ocean front disposal areas
may be re-colonized by benthic species in several months to a year's time; if the same area is impacted in
successive years, the potential for re-colonization declines greatly. Seasonal pre and post project monitoring
of the disposal site should be extended and evaluated as a required permit condition. This site is under
significant pressure from frequent beach disposal operations.
The project description states that smaller annual excavation events along the inlet shoulder may be needed
to keep the inlet channel from shoaling in rapidly. It is stated that these smaller annual events will be
proactive and will result in overall reduced costs and environmental impacts. These an;-lual events, beyond
the proposed 2005 maintenance event, should be required to be submitted for DA and CAMA permit
applications if proposed, and not be automatically covered under the current permit applications.
It is stated that all work with the proposed maintenance event will be confined to previously disturbed areas.
NCCF assumes that this is the reason that the permit application does not contain a mitigation plan.
However there are a number of areas of concern within the original mitigation plan that should be addressed.
II. The current status of the project permitee's, New Hanover County, compliance with existing
permit conditions, conservation measures and mitigation requirements needs to be examined by the
regulatory agencies to ensure that adequate mitigation occurs and that compliance with the agreed
upon permit conditions is enforced.
The original mitigation plan for the Mason Inlet Relocation project fell short of compensating for the loss of
40.7 acres of inlet and intertidal sand bar and shoal habitat as a result of the project. These are critical
habitats for many species of concern in this region. This shortfall and the current status of compliance with
existing permit conditions, conservation measures and mitigation requirements need to be examined by the
regulatory agencies to ensure that adequate mitigation occurs and that compliance with the agreed upon
permit conditions is enforced. This evaluation needs to occur in conjunction with the review of the
application for the planned maintenance event. The summary of permit conditions, conservation measures
and mitigative requirements. are taken from the following associated permits:
^ L7S Army Corps of Engineers (Corps) Department of Army (DA) permit Action ID. #: 199901052 dated
December 14, 2001 to relocate Mason Inlet, excavate Mason Creek, construct a sediment basin, and renourish
the southern end of Figure 8 Island and the northern end of Wrightsville Beach
^ US Fish and Wildlife Service (USFWS) Biological Opinion (BO) Service ID. #: 00-0655 dated March 14,
2001 on the Mason Inlet Relocation Project and the USFWS letter of amendment to the BO dated September
5, 2001
^ North Carolina Department of Environment and Natural Resources (NCDENR) and Coastal Resources
Commission (CRC) Coastal Area Management Act (CAMA) Major Permit #: 151-01 dated November 28,
2001 for major development'in an Area of Environmental Concern (AEC) and for excavation and filling at
Mason Inlet, Mason Creek and AIWW.
^ North Carolina Department of Environment and Natural Resources (NCDENR) Division of Water Quality
(DWQ) Certification Pursuant to Section 401 of the Federal Clean Water Act WQC Project #: 000008 and
NCCF Comments
Mason Inlet Maintenance
09/09/04 3

Certification #: 3274 dated April 30, 2001 for the proposed Mason's Inlet relocation and associated dredging
and Revised Certification for Project #: 000008 and Certification #: 3274 dated June 27, 2001
Following is a summary of NCCF's concerns with the status of compliance with the described permit
conditions, conservation measures and mitigative requirements.l~CCF comments and findings are in italics.
A. The North Carolina Department of Environment and Natural Resources (NCDENR) Division of
Water Quality (DWQ) Certification Project #: 000008 and Certification #: 3274 dated April 30,
2001 for the Mason's Inlet relocation and associated dredging and Revised Certification for
Project #: 000008 and Certification #: 3274 dated June 27, 2001 contain condition # 6. This
condition describes the required monitoring of marshes adjacent to Mason Creek. It states that, "If this
monitoring reveals an additional loss of wetlands in this area, then additional compensatory wetland
mitigation will be required". The required Biological Monitoring Plan contained parameter #
Distance (ft) loss or Bain of intertidal marsh habitat at transect locations.
This monitoring parameter addresses the requirement to measure any loss or gain in the marshes
adjacent to Mason Creek. The Biological Monitoring reports should be examined to determine the
status of these marshes and if any additional mitigation. is required.
B. All work, new and maintenance must occur between 11/15 and 3/30 of any year unless the
applicant receives an. explicit exemption or extension from the' Corps. Corps Permit #2. Prior
approval of beach nourishment occurring outside 11/15 to 4/1 must also be obtained from DCM, in
consultation w/ NCDMF. CAMA Permit # 18. In order to protect sea turtle nesting habitat, no work
may be carried out on the beach between 5/1 and 11/15 without prior authorization from DCM, in
coordination with WRC and FWS. CAMA Permit # 25. Finally, the BO restricts work to between
11/15 and 7/15. BO Amendendemnt 1.
The initial construction phase of the project extended past this deadline and was oj~cially completed
on Apri122, 2002. An extension was applied for on 1/28/02 for and granted on March 28, 2002. The
extension for the construction window resulted in construction activity, dredging and beach in-frll
activities. occurring as water birds were trying to nest, fishery resources were active in the area, and
some invertebrates were at their peak abundance
C. Only beach compatible sand shall be used for beach nourishment. Corps Permit # 18, LAMA Permit
Conditions # 20, 21, Biological Opinion (BO) Sea Turtle Teens and Conditions (T&C) #1. Equipment
must allow for inspection of dredged materials to determine if beach compatible. Corps Permit # 18. All
dredged material shall be tested for beach compatibility and tests must be provided to Corps for
confirmation before material placed on beach. Incompatible material will be removed from project area
and placed in a high ground site specifically approved by Corps, NCDCM, and NCDLQ. Corps Permit
# 18. CAMA Permit Condition #21 further requires that if the dredging operation encounters any
incompatible material, dredge must stop immediately and-move to a different approved area where
suitable material exists.
New Hanover County and one of its contractors, All State Dredging, received a Notice of Violation
(NOV #03-140 & #03-I1D) of its CAMA Permit # 1SI-01. They were in violation ofCAMA conditions
#20, 21, and the County received a letter of non- compliance from the Corps for being out of
compliance with the Corps Permit Condition #18. 2100 sq ft of marsh was filled from a leaking dredge
pipeline, dredging was not halted until the leak was fixed, and unsuitable material had been delivered
and placed onto the beach along the southern end of Figure 8 Island.
NCCF Comments
Mason Inlet Maintenance
09/09/04
4

D. The permittee shall maintain the dike walls constructed around holding areas to eliminate the
release or escape of dredged material. Failure of a dike wall will result in the immediate cessation of
pumping into the specific diked area. Repair work on dike walls will not begin until. specific permission
is requested and received from the Corps and NCDCM with the exception of work necessary to provide
emergency repair of dike wall failures. Corps Permit # 18 A cross dike or similar structure and sections of
the existing dike(s) aze to be constructed with material from within the Corps property boundary of the
disposal are to sufficiently retain the dredged materials. Corps Special Condition. 8/27/02
Appropriate sediment and erosion control practices which equal or ezceed those outlined in the
most recent version of two manuals .... will be put in place and maintained. The control practices
shall be utilized to prevent exceedence of the appropriate turbidity water quality standard (25 NTUs in
all saltwater classes). NCDWQ 401 WQC Condition # 1
New Hanover County was found to be Not In Compliance with the above listed conditions as noted in
letter from the Corps to the County dated 10/21/02. The County violated the permit conditions by:
1) "There is an area of disturbance along the dike of the disposal area adjacent to the AIWW.
Approximately 3001inear feet of dike crest adjacent to the AIWW... was cleared of all vegetation
without any erosion control measures or re-seeding. The disturbed areas were also depleted of all
vegetation with no erosion control measures or re-seeding. Sand was noticed sloughing of into marsh
adjacent to the entire length of dike.
2) There were 2 HDPEpipelines left on site
3) There was no cross dike or similar structure constructed within the Corps property boundary of the
disposal area.
E. Maintenance events or other work after the initial construction may not proceed without
approval from the Corps, Condition # 3, and a modification of the CAMA permit, CAMA
Condition # 29. The project will only be maintained for inlet stabilization purposes per the Inlet
Management Plan. Corps Permit #22. Each maintenance request requires submission of a report
identifying the need for the maintenance, submitted to Corps 120 days prior to the anticipated event and
including monitoring data and analyses, #3. Corps will evaluate to insure impacts, including cumulative
effects,. aze reasonable, that mitigation is appropriate and that maintenance shall be as widely spaced as
practicable. Corps will coordinate w/state and fed resource agencies. The request for modification of the
CAMA permit will consider such factors as migration of new inlet, amount.of material to be excavated,
season of proposed work, information from monitoring, success of wetland mitigation, and construction
methodology, #29.
Regulatory agencies are required to evaluate all the information and data gained from the physical
and biological monitoring, in addition to -the maintenance triggers contained within the inlet
maintenance plan, to determine if a permit modification is justified. This must include an evaluation
of the success of the biological monitoring plan and water and shore bird habitat management plan.
In addition the status of the marsh adjacent to Mason. Creek must be evaluated. Finally, the status of
compliance of the permittee with the required permit conditions, conservation measures and
mitigative measures must be measured. If there are items that are deemed unsatisfactory, then that
should weigh on the review process of the modification request.
F. The applicant shall implement compensatory wetland mitigation at same time or prior to
beginning project construction, as proposed in the applicant's mitigation plan. Attach. 5, Corps
EA. Any deviation must receive specific prior approval from Corps. Corps Permit # 15.
The completion of the wetland mitigation restoration site was delayed until June 2003. While this
NCCF Comments
Mason Inlet Maintenance
09/09/04 5

delay was approved, the USFWS requested immediate implementation of the wetland compensation.
Citing the interim losses to frsh and wildlife services due to the year delay, the USFWS requested
assurance offending to perform the compensation and an increase in the acreage of wetlands to be
restored, enhanced, created or preserved.
G. Within 30 days of permit issuance, the applicant shall develop and implement, in consultation
w/DENR, WRC, FWS, NMFS, and Audubon, subject to approval by Corps, a shorebird and
waterbird management plan and biological monitoring plan. If Corps determines remedial action
necessary, shall implement action directed by Corps. Corps Permit #16. Applicant will also devise
and implement a plan, in coordination w/Corps and FWS, to minimize impacts to nesting plovers during
initial construction, including minimizing heavy equipment in project area at any given time, not storing
heavy equipment w/in project area, minimizing spatial extent of work area, cordoning off an area to
remain undisturbed. BO T&C Plover #2. Applicant will also design and implement a restrictive access
program, including enforcement, to limit access to sand spit, sand and mud flats, and bayside flats in the
project area throughout the year upon completion of construction activities. BO T&C Plover #3.
1) Biological monitoringylan
A number of recommendations made by the US Fish and Wildlife Service, the North Carolina Wildlife
Resources Commission, and the Audubon Society regarding needed elements of the monitoring plan
were not incorporated into the final document. Specifically, these agencies:
a) Requested more pre project baseline data. They advised that at least one year ofpre-construction
data on the biological resources in the project area was needed and should be collected on at least a
seasonal basis. Instead, such data was only collected during December when population levels are
often very reduced. This does not provide a full and accurate picture offish and wildlife resources '
utilization of the area and excludes adequate baseline data. Data from the Wilmington Harbor Study
will be used to supplement the Mason Inlet Project data. However, the data from the Wilmington
Harbor Study is not specific to the Mason Inlet Project area.
b) Called for more frequent biological monitoring under the plan. The monitoringplan prescribes
sampling for biological resources only once annually in November or December. Sampling in the
inter-tidal surf zone will occur only once annually in the spring. Annual monitoring will occur for the
life of the permit or_ until such time deemed necessary by relevant state and/or federal agencies. Many
of the resource agencies were concerned that the described sampling regime will not provide accurate
or adequate data due to the sampling occurring only during winter months. The status and diversity of
animal and plant communities. and populations. in the project area vary throughout the year, and
many species are at their lowest levels of activity. and population in December when the sampling will
occur. This will make it very dill cult to fully evaluate the effects of the project on the biological
resources in the project area, potentially endangering fish, wildlife and plant communities in the
project area. In addition it will be difficult to determine when the biological resources of the project
area have recovered from the dredging and beach frll activities of the project.
Z) Shorebird and waterbird mana eg ment plan
Condition #16 required the preparation of a shorebird and waterbird and biological monitoring and
management plan within 30 days of the issuance of the permit. This requirement was a critical element
of the project so that it would not cause unacceptable environmental damage. Several key components
of this condition were not adequately complied with:
Piping plover monitoring began on November 21, 2001 and was conducted by Dr. David Webster of
UNCW and several of his students. Waterbird monitoring began on Apri123, 2002 and continued 2-3
NCCF Comments
Mason Inlet Maintenance
09/09/04

times a week throughout the nesting season and then weekly outside of the nesting season.
The water and shore bird management plan was developed late and not completed until Apri19, 2002,
86 days after they were due. Some.. elements of the plan were put in place in a timely fashion.
However, the goals of restraining human and animal disturbance to waterbirds, and protecting and
providing nesting, foraging and roosting habitats for waterbirds were not fully implemented until May
24, 2002, when posts, ropes and signs protecting the nesting area were put up. The water and shore
bird nesting season begins April 1.
As a result of the delay in posting and restricting access to the nesting area, and inadequate
enforcement of the restricted area, adequate protection of nest sites did not occur during the 2002
nesting season. Human and animal disturbances were observed in and near the restricted nesting
area and more frequently in the intertidal shoal areas, which are utilized as foraging and roosting
habitats. These factors are significant and need to be seriously considered when evaluating the bird
activity'and nesting data from .the 2002 nesting season.
In 2001 approximately 126 nests that were laid by five species of water and shore birds were observed
in the project area. According to the Year 1 Piping Plover and Nesting Shorebirds and Waterbirds
Survey Report submitted by Dr. Webster, 22 nests were laid by S species of waterbirds and shore birds
in the project area during the 2002 nesting season. Webster states that , " In terms of nest numbers of
nest numbers, it appears that the relocation project had a severe negative impact on colonially-
nesting waterbirds, but that the project had little impact on nesting shorebirds. In terms of overall
productivity ..., it appears as though the relocation project had a negative effect on both colonial
waterbirds and shorebirds: "The factors described above should be evaluated when determining the
effectiveness of the compliance with this permit condition.
In an 11/25/02 letter from the USF'WS to the Corps the USFWS stated; "Not all of the Terms and
Conditions of the BO have been met ". "We believe that the permitee and Corps are not in compliance
with the Service's BO. " "Specifically: BO T&C Plover #3 was not properly implemented. As a result
there were impacts from pedestrians and pets to the piping plover that were not anticipated. We
believe this would not have been the case had this condition been fully implemented as we had agreed
to in the BO and Corps permit ".
Again in a 04/08%03 letter from the USFWS to the Corps the USFWS stated; "That the BO T&C
Piping Plover #3 was not implemented properly or in a timely manner. However ... it appears that the
__ ..permitee has taken some. measures. and is in the process of implementing additional measures. that will
fulfill this condition. "
With the finalizing of the shorebird and waterbird and biological monitoring and management plan in
2002, a number ofpositive steps were taken by the County to comply with this permit condition for the
2003 nesting season. Protective ordinances were put in place, educational signage was created and
put in place, and a cooperative agreement between Audubon NC and the County was developed to
cover the project area for the 2003 and 2004 nesting seasons. The above steps and the cooperative
agreement empowered Audubon to conduct educational activities, and employ a steward for the
nesting area. These steps in combination with the County and its consultant posting and roping off the
nesting area served to implement Corps Permit #16. The 2003 nesting season was successful and over
200 nests were laid in the project area. The 2004 nesting season was described as being even more
successful with approximately 300 nests laid. NCCF recommends that these actions be continued for
the next maintenance interval. This is due to its success and the need to mitigate for the failure in
2002.
NCCF Comments
Mason Inlet Maintenance
09/09/04

H. Immediately after nourishment and prior to April 1g` for three subsequent years, sand
compaction shall be monitored in the placement area according to protocol agreed to by service,
State, County, and Corps, BO T&C Turtles #3, and visual surveys for escarpments shall be made.
Those escarpments that interfere with sea turtle nesting or exceed 18 inches in height for a distance of
100 ft shall be leveled to natural beach contour by April 1st. BO T&C Turtles #5.
In an 11/25/02 letter from the USFWS to the Corps the USFWS stated "Not all of the Terms and
Conditions of the BO have been met ". Speciftcally: BO T&C Turtles #4 addresses pre project sand
compaction data. Sand compaction data were not collected, therefore this condition was not
implemented in accordance with the BO and the Corp's permit. This lack of implementation of this
condition of the BO was reiterated in the 4/8/031etter from the USFWS to the Corps.
I. USACE permit condition #7 states that the permitee would cooperate with the NCDMF in an
oyster-seeding program in the project area. Ten thousand bushels of oyster shells are to be seeded
annually until the first maintenance e~+ent.
The County worked with the Town of Wrightsville Beach to establish a temporary loadingfacility for
NC DMFbarges. The facility was used to load shell onto the barges for transport of oyster shell to
planting sites. To date the County has purchased approximately 13, 000 (3, 000 in 2002 & 10, 000 in
2003) bushels of oyster shell for NC DMF to spread. Corps Permit # 7 requires 30, DOD bushels to
have been planted to date.
Ina 10/31/02 letter from the Corps to Ted Wilgis ofNCCF, the Corps states; `At any maintenance
request, if the average is less than 10, 000 bushels annually, then the project's impacts on fisheries
resources should be reexamined. "
J. USACE permit condition #11 states that all sand bags and fragments were to be removed from
Shell Island Resort and disposed of properly in accordance with NC Division of Coastal
Management requirements.
A significant portion of the sand bag wall structure was left in place. Removal of these bags was a
condition of the variance granted by the Coastal Resources Commission that allowed the bags to stay
in place until the inlet was relocated. The Commission never removed that condition from its
variance, and legally no other entity had the authority to override this explicit requirement. However,
the Wilmington Regional DCM oj~ce allowed the remaining sand bag structure to remain in place.
In mid-October 2002, the County had heavy equipment on the ocean beach on the Wrightsville Beach
side of the Mason Inlet Project- area removing geo-textile material left over from the construction
phase of the project. The USFWS had no record of the Corps or the County contacting them about the
timing or methods of removal prior to the activity. Sea turtle hatching season runs through November
1 S, therefore the work was conducted during the nesting and hatching season.
III. As stated in the cover letter for the Biological Opinion (BO) transmitted from the USFWS to the
Corps on 3/14/01, "[t]he conservation measures... offered by the applicant in the biological
assessment and in their February 26, 2001 letter, are considered part of the proposed project and
were reviewed as such in preparing our opinion." The 9/15/01 BO Amendment reiterates this point,
stating, "Since conservation measures are part of the proposed action, their implementation is required under
the terms of [Endangered Species Act] consultation." These statements, as well as communication with
FWS staff, indicate that the "no jeopardy" finding in the BO is contingent on the implementation of these
measures. USFWS staff has also indicated the belief that Corps Permit Condition # 1, which states that
NCCF Comments
Mason Inlet Maintenance
09/09/04

y . • ~
"[t]he work will be constructed in strict accordance with the attached plans and all conditions of this permit,"
incorporates the conservation measures into the binding conditions of the Corps permit. Therefore the
permitee must follow through on the following commitments:
IC. Protection of the north end of Carolina Beach must include implementation of a monitoring
program and /or the development of a Comprehensive Habitat Management and Conservation
Plan (developed in conjunction with the USFWS) within one year of the start of the initial
construction operation (at Mason Inlet) to assess and further minimize impacts to Federally-listed
species and other trust resources. USFWS BO T&C #6
Ina 04/08/031etter from the USFWS to the Corps the USFWS stated; "The permitee has failed to
develop and implement a Comprehensive Habitat Management and Conservation Plan and
monitoring program at the north end of Carolina Beach ". "We understand that some measures have
been taken to minimize impacts to federally listed species at the site. However, this measure. does not
satisfy the condition of the BO. To fully and completely implement the condition, a conservation plan
that provides for management and protection of the site must be developed." Ina 08/20/03 letter to
the USFWS the Corps states that they recommend the removal of this term and conservation measure.
A citizens advisory group has formed under the auspices of the Town of Carolina Beach to develop
some policies for the North end of Carolina Beach. The Town also successfully requested that the
County transfer jurisdiction of the area to the Town. These measures, while constructive, do not
address the required habitat management or monitoring plan. To date this condition has not been
fully implemented.
L. The. remaining tracts (approximately 30 acres) on Masonboro Island must be purchased and/or
placed into permanent conservation status prior to the initiation of any maintenance dredging
activities or within three years of the start of the initial construction operation, whichever is
earlier. USFWS BO T&C #5
Ina 04/08/03 letter from the USFWS to the Corps the USFWS stated; " We propose to remove this
condition from the BO T&C Piping Plover #3 was not implemented properly or in a timely manner.
However.... it appears that the permitee has taken some measurers and is in the process of
implementing additional measures that will fulfill this condition. "
The removal of this condition from consideration as compensation for direct losses to the resource,
leaves the loss of bare sand barrier spit habitat uncompensated. The direct, uncompensated loss of
40.7 acres of intertidal sand bar and shoal habitats represents a significant impact to aquatic
resources and coastal waters. The USFWS evaluation of impact to these resources based on the 40
CFR 230.10 (c) guidelines for adverse impacts to aquatic resources, indicate that the proposed
compensatory mitigation does not adequately offset losses of habitats. This area is critical nesting
area for shorebirds and waterbirds. NCCFfinds the current compensatory mitigation plan severely
inadequate, and it needs to be revaluated to assure adequate mitigation occurs for the Mason Inlet
Relocation Project. While a significant portion of intertidal shoal has reformed since the initial
relocation project, the proposed maintenance-dredging plan includes impacts to some of these
reformed acres of intertidal shoal. An adequate mitigation plan must be in place before the proposed
maintenance dredging is permitted..
In Summary
The proposed application for a maintenance event to dredge Mason Inlet and Mason Creek and place the
material on Figure 8 Island for beach nourishment offers an opportunity to evaluate a project with potentially
NCCF Comments
Mason Inlet Maintenance
09/09/04
9

.. .
reduced costs and environmental impacts. While the project will still result in the direct loss of reformed
intertidal and shallow subtidal areas, an effort has been made to reduce these impacts.
However the proposed project and permit application must be evaluated together with the status of the
original permit conditions, mitigative requirements, conservation measures and prior and current conditions
within the project area. While some of the impacts from the Mason Inlet Relocation Project have been
mitigated for either naturally or through the action of the petrnitee, additional impacts have demonstrated the
project's potential to adversely effect bird and fish habitats and populations, including federally endangered
or threatened piping plovers and other biological resources. These were some of the principal concerns in the
authorization of the project. Permits were issued that included numerous conditions that, while still
inadequate, were supposed to either avoid or offset the majority of these expected consequences of the
project.
However, as indicated above, there a number of critical conditions that have not been met, fully complied
with, or have been removed from the pernlits. This is in addition to the NOV's and letters ofnon-compliance
incurred by the pelmitee. NCCF strongly recommends that all the relevant permitting and regulatory
agencies, convene to reinitiate formal consultation to fully evaluate the status of the existing permit
conditions, conservation measures, and mitigative measures. This evaluation and consultation should also
include the record of compliance of the permitee with these requirements, and the status of the conditions
within the project area.
Due to some of the conservation measures being removed as conditions for the project, a full evaluation of
required mitigation calculations and measures based on the original project impacts and mitigation plan must
be reinitiated to account and mitigate for the uncompensated losses to critical intertidal, barrier beach and
inlet shoulder habitats. Acceptable plans and timetables for current and planned mitigative measures must be
adopted and enforced. The public should be provided with formal opportunities to review and comment on
any additional permit modifications, and proposed mitigation and conservation measures to ensure full
compliance with public participation opportunities provided by the law. It is recommended that this
consultation occur as soon as possible so that adequate and timely consideration can be given to the
proposed maintenance dredging application.
Thank you for your time and consideration of these recommendations. NCCF appreciates the opportunity to
continue to participate in the discussion of this project. Please feel free to contact me at 910-790-3275 or
coastk er-cf~nccoast.or if you have any questions or need additional information.
1
Since y
j
1
T i
Cape Fear C eeper
~:
Colonel Charles R. Alexander - USACE
Charles Jones- NCDCM
Ron Sechler - NMFS
Dr. Garland Pardue - USFWS
Bennett Wynne-NCWRC
John Domey - NCDWQ
Dave Weaver -New Hanover County
Chris Gibson - Gahagan & Bryant Associates, Inc.
Steve Morrison -Land Management Group, LLC
Trip Van Noppen - SELC
Walker Golder -Audubon
Todd Miller -NCCF
NCCF Comments
Mason Inlet Maintenance
09/09/04 10

Form DCM-MP-1
~~~~ V
ATI~
PLIC
WETLANDS P JUN 2 4~ ~t~Ni
(To be completed by alt applicants)
JUL 2 6 2004 ~ DIVISION OF
A (ll ini ITV e~nrinu _
1. APPLICANT
a. Landowner:
Name New Hanover County
Address
230 Market Place Drive. Suite 160
City Wilmington State N.C.
Zip 28403 Day Phone 9 i 0-798-7139
Fax [phone]
b. Authorized Agent:
. Name
Gahagan & Bryant Associates, Inc.
Address 7217 Ogden Business Lane, Unit 113
Wilanington State N.C.
City
Zip 28411 Day Phone [phone]
Fax [phone]
c. Project name (if any) Mason Inlet Relocation
Proiect
!V ~D7E: Penrit wiR be irurnd in aan¢ of lm~downer(i), ad/or
~-iOXd wame.
2. LOCATION OF PROPOSED
PROJECT
t, ~u~, New Hanover
COASTAL MANAGEMENT
b. City, town, community or landmark
T=imire R Tclanri
c. Street address or secondary road number
d. Is proposed work within city Limits or planning
jurisdiction? Yes _~ No
e. Name of body of water nearest project {e.g. river,
creek, sound, bay}Middle Sound & Atlantic Ocean
3. DESCRIPTION AND PLANNED USE
OF PROPOSED PROJECT
a. List ail development activities you propose (e.g.
building a home, motel, marina, bulkhead, pier, and
excavation and/or filling activities.
Maintenance dredging of Mason Inlet and
Mason Creek. Nourishment of Figure 8 Island
Beach.
b. js the proposed activity maintenance of an existing
project, new work, or both? Maintenance
c. Will the project be for public, private or commercial
use? Public
d. Give a brief description of purpose, use, methods of
ooastrucxion and daily operations of Proposed
project. If more space is Headed, please attach
additional pages. See attached nroiect drescrintion.

A.~.a a;ros

Form DCM MP-1
wastewater treatment facilities.
existin
ib
D
g
e
escr
m.
4. LAND AND WATER Adiacent nronerties are on sevtic svstems.
CgARACTERISTICS

+/- 80 acre n. Describe location and type of discharges to waters
a. Size of entire tract of the state. (For example, surface runoff, sanitary
b. Size of individual lot(s) N/p' wastewater, industnal(commercial effluent, "wash
down" and residential discharges.}Surface runoff.
c. Approximate elevation of tract above MHW or
NV47L -10 to +7 NGVD
d. Soil type(s) and texture(s) of tract o. Describe existing drinking water supply source.
fine/medium Qrain sand Community Water Svstem

e. Vegetation on tract N/A

f. Man-made features now on tract None
5. ADDITIONAL INFORMATION

g. What is the CAMA Land Use Plan land ~ addifion to the completed application form, the

• classification of the site? (c~u ~ tort tma,~ ~-) following items must be submitted:
Conservation Transitional • A Dopy of the deed (with state application only) or
Developed Community
other instrument under which the applicant claims tide
Rural X Other to the affected properties. If the applicant is not
h. How is the tract zoned by local government? ~ai~ng ~ ~ the owner of said property, then
forward a copy of the deed or other instrument under
Residential ~ Conservation ion
i
i
l
tt$n perm
ss
us wr
which the owner claims title, p
i Is the proposed project consistent with the applicable from the owner to carry out the project.
.
zoning? X Yes No
~~ z~8 ~~, ~~~1
• An securate, dated work plat {'including plan view
and cross-secxional drawings) drawn to scale in black
j. Has a professional archaeological assessment been ink on an $ 1/Z' by 11" white paper. (Refer w
done for the tract? X y~ No Coastal Resources Commission Rule 7J.0203 for a
If yes, by whom? ATM 2000 detailed description.)
k Is the project located in a National Registered ~•~ note that original drawings are prefaced and
. Historic District or does it im-oive a National ~Y high 9u~rty copies will be accepted. Blue-line
Register listed or eligible propert}~- P~ or otha ~8a Plats are acceptable only if an
Yea X No adequate number of quality copies are provided by
applicant. {Contact the U.S. Army Corps of
1 Are there wetla~s on die site? Yes X No ~ regarding that agency's use of larger
. Coastal {marsh) Other drawings.) A site or location map is a part of plat
has a delineation been conducted?
If yes ~Nb'~~ ~ it must be sufficiently detailed to
,
(~ ~~, ~~u1 guide agency personnel unfamiliar with the area to die

Form DCM-MP-1
site. Include highway or secondary road (SR}
numbers, landmarks, and the like.
• A Stormwater Certification, if one is necessary
• A list of the names and complete addresses of the
adjacent waterfront (riparian) landowners and
signed return receipts as proof that such ovmers
have recxived a copy of the application and plats
by certified mail. Such landowners must be advised
that they have 30 days is which to submit comments
on the proposed project to the Division of Coastal
Management. Upon signing this form, the applicant
further certifies that such notice has been provided.
Name Sep-attached list- -_ _ __-- _
Address
Phone _
Name
Address
Phone
Name
Address
Phone
• A list of previous state or federal permits issued for
work on the project tract. Include permit numbers,
permittee, and issuing dates.
NCDENR Permit #151-O1
USACE Permit # 199901052
• A check for X475 Wade payable to the Department of
Environment, Health, and Natural Resources
(DEHNR) to cover the costs of processing the
application.
• A signed AEC hazard notice for projects in
oceanfront and inlet areas.
• A statement of eompGance with the N.C.
Environmental PoCrcy Ad (N.C.G.S. 113A - 1 to
10) If the project involves the expenditure of public
. funds or use of public land's, attach a atatemeM
doazmeating compliance with the North Carolina
Environmental Policy Act_
6. CERTIFICATION AND PERMISSION
TO ENTER ON LAND
I understand that any permit issued in response to this
application will allow only the development described in
the application. The project will be subject to conditions
and restrictions contained ~~ the permit.
I certify that to the best of my knowledge, the proposed
activity complies with the State of North Carolina's
approved Coastal Management Program and will be
conducted in a manner consistent with such program.
i certify that I am authorized to grant, and do in fact,
great permission to representatives of state and federal
review agencies to enter oa the aforementioned leads in
connection with evaluating information related to this
permit application and follow~p monitoring of the
project.
I further certify that the information provided in this
application is truthful to the best of my knowledge.
Q~ ~~
This is the 23 day of J'^'~E .~"
Print Name tf ,e1S G l ~ So r/ /-E
Signature
lardax~cr ar Arthoriz~d Ageru
Please indicate attachments pertaining to your Proposed
proj~-
X 1DCM MP-2 Excavation and Fill Information
DCM MP-3 Upland Development -
DCM MP-~
- Structures Information
DCM MPS Bridges and Culverts
DCM MP-b Marina Development
NOTE: Please sign and date each attadvnent in the
space provided at the bonom of each form.

Dr. Douglas C. Leet
10749 Trego Trail
Raleigh, NC 27614
RIPARIAN NOTIFICATION LIST
Mr. Stuart R. deWitt
500 Museum Drive
Charlotte, North Carolina 28207
Mr. Adair M. Graham
P.O. Box 7005
Wilmington, North Carolina 28406
Mr. Edmund T. Buckman, III
Buckman Family, LLC
102 Forest Drive
Washington, North Carolina 27889
Mr. Hall F. Barnett
2804 Lakeview Drive
• Raleigh, North Carolina 27609
Mr. Charles Woodrow Smith, Jr.
114 Martingale Lane
Wilmington, North Carolina 28409
Mr. Kenneth L. Huggins
5407 Tory Hill Road
Greensboro, North Carolina 27410-
Mr. James H. Wilson
2792 Fieldwood Court
Winston-Salem, NC, North Carolina 27106
Mrs. Blair Hughes
HTH Partnership
2209 White Oak Road
Raleigh, North Carolina 27608
Mr. Thomas G. Fisher
920 Cowper Drive
Raleigh, North Carolina 27608
106 BEACH ROAD SOUTH
108 BEACH ROAD SOUTH
110 BEACH ROAD SOUTH
112 BEACH ROAD SOUTH
114 BEACH ROAD SOUTH
116 BEACH ROAD SOUTH
116 BEACH ROAD SOUTH
120 BEACH ROAD SOUTH
122 BEACH ROAD SOUTH
124 BEACH ROAD SOUTH
•

RIPARIAN NOTIFICATION LIST
Mrs. Paula Bushardt 126 BEACH ROAD SOUTH
1513 Futch Creek Road
Wilmington, North Carolina 28411
Dr. George C. Venters 128 BEACH ROAD SOUTH
905 Willimason Drive
Raleigh, North Carolina 27608-
Mr. Matt H. Nowell 130 BEACH ROAD SOUTH
P.O. Box 10005
Raleigh, North Carolina 27605
Mr. Patrick Bradley Southerland 132 BEACH ROAD SOUTH
410 Loder Ave.
Wilmington, North Carolina 28409
Mr. William D. Poe, Jr. 134 BEACH ROAD SOUTH
1113 Cowper Drive
Raleigh, North Carolina 27608-
• Mr. William C. Smith, Jr 136 BEACH ROAD SOUTH
60 Magnolia Road
Pinehurst, North Carolina 28374
Mr. William deR. Holt 138 BEACH ROAD SOUTH
206 Meadowbrook Terrace
Greensboro, North Carolina 27408
Dr. James David Jones 140 BEACH ROAD SOUTH
2813-305 Market Bridge Lane
Raleigh, North Carolina 27608
Mr. Frank D. Gorham, III 142 BEACH ROAD SOUTH
40 First Plaza
Suite 601-N
Albuquerque, New Mexico 87102
Mr. Michael W. Haley 146 BEACH ROAD SOUTH
902 Country Club Drive
Greensboro, North Carolina 27408
•

RIPARIAN NOTIFICATION LIST
Mr. Julian W. Rawl 148 BEACH ROAD SOUTH
BBC Investors, LLC
PO Box 8068
Greenville, North Carolina 27835
Mr. Stephen D. Goggins 150 BEACH ROAD SOUTH
150 Beach Road South
Wilmington, North Carolina 28411
Mr. John J. Mack 152 BEACH ROAD SOUTH
Bald Eagle Partners
91 Sunset Lane
Rye ,New York 10580
Mr. Bradley Charles Davis 154 BEACH ROAD SOUTH
2706 Bartram Place
Winston-Salem, North Carolina 27106
Mrs. Carolyn R. Armstrong 156 BEACH ROAD SOUTH
1806 Winterlochen Road
• Fayetteville, North Carolina 28305
Mr. Hamid Dehghan 158 BEACH ROAD SOUTH
116 Michael Street
Edison, New Jersey 08820
Dr. Harry R. Culp 160 BEACH ROAD SOUTH
500 Woodbrook Drive
High Point, North Carolina 27262
Mrs. NaFiseh Hatefi 162 BEACH ROAD SOUTH
6832 Greystone Drive
Raleigh, North Carolina 27615
Mr. John Bratton; Jr. 164 BEACH ROAD SOUTH
3412 Williamsborough Court
Raleigh, North Carolina 27609
Mr. Earl Johnson, Jr. 166 BEACH ROAD SOUTH
1001 Marlowe Road
Raleigh, North Carolina 27609
•

RIPARIAN NOTIFICATION LIST
Mr. Phillip D. Ray, Jr 168 BEACH ROAD SOUTH
2011 Saint Andrews Road
Greensboro, North Carolina 27408
Mr. Joe D. Floyd, Sr 170 BEACH ROAD SOUTH
1500 Westchester Drive
High Point, North Carolina 27262
Mr. Rudy Smithwick 172 BEACH ROAD SOUTH
8633 Vintage Club Drive
Wilmington, North Carolina 28411
Mr. N.P. Hayes, Jr 174 BEACH ROAD SOUTH
2109 Layfayette Avenue
Greensboro, North Carolina 27408
Mr. Louis W. Sewell, Jr 176 BEACH ROAD SOUTH
P.O. Box 536
Jacksonville, North Carolina 28541
Mr. Charles M. Winston 178 BEACH ROAD SOUTH
2626 Glenwood Avenue, Suite 200
Raleigh, North Carolina 27608
Mr. Charles M. Winston 180 BEACH ROAD SOUTH
3504 Chaucer Place
Raleigh, North Carolina 27609
Mr. Charles M. Winston 182 BEACH ROAD SOUTH
3504 Chaucer Place
Raleigh, North Carolina 27609
Mr. Warren R. Hall 184 BEACH ROAD SOUTH
1108-F Dover Road
Greensboro, North Carolina 27408
Mr. Patrick H. Nettles 186 BEACH ROAD SOUTH
186 Beach Road South
Wilmington, North Carolina 28411
Mr. Pablo Eguia 188 BEACH ROAD SOUTH
PO Box 364127
San Juan, Puerto Rico 00936-4127
•

RIPARIAN NOTIFICATION LIST
George Henry Hutaff Trust #2 190-194 BEACH ROAD SOUTH
c/o Mr. David Ward
Ward & Smith
1001 College Court
New Bern, NC 28562
Figure "8" Beach Homeowners' Association
15 Bridge Road
Wilmington, NC 28411
Shell Island Homeowners' Association
c/o Ms. Carol Giachetti
P.O. Box 420
Wrightsville Beach, NC 28480
•
•

Form DCM MP 2
~'XCAVATION
AND FILL
{Except bridges and ca-Iverts)
Attach this form to Joint Application for CAMA Major
Permit, Form 1JCM-MP-1. Be sure to complete all
oilier sections of the Joint Application that relate to this
proposed project.
Describe below the purpose of proposed excavation or
fill activities. All values to be given in feet.
Average )k~asl
> h'qi~
t.e~w wiam Dept>~ nept]t
Access
channel
Canal
Boat
basin
Boat
ramp
Rock
groin
Rock
breakwater
Beach
Nourishment
(Excluding
shoreline
stabilization)

-8 MLW
4800 i40- Elevation Mason
500 -5 to +8 Creek
MLW -3 Inlet

,~ YY; y'
`P' 'F ,~ r
T
"j1
Elevation Elevation
4500 300 +2 NGVD +7 NGVD
1. EXCAVATION
a. Amount of material to be excavated from below
MHW or NWL in cubic yards 150.000 cv
b. Type of material to be excavated fine/medium
Arai
c. Does the azea to be excavated include coastal
wetlands (marsh), submerged acluaiic vegetation
(SAVs) or other wetlands? Yes x No
d. Highground excavation in cubic yards 34.000 cv
2. DISPOSAL OF EXCAVATED
MATERIAL
a. Location of disposal area Beach front on Figure "8"
Island
b. Dimensions of disposal area 4500 x 300
c. Do you claim tale to disposa! area?
Yes X No
If no, attach a letxer granting permission from the
p~y~, Land of the state.
d. Will a disposal azea be available for future
maintenance? X Yes No
If yes, where? Beach front of Figure "8" Island
Revised 03195

Form DCM-MP-2
Does the disposal area include any coastal wetlands
(marsh), SAVs or other wetlands?
y~ x No
f. Does the disposal include any area in the water?
x Yes No
If yes,
(1) Amount of material to be placed in the
water 58.000 cv
(2) Dimensions of fill area 4500 x 300
{3) Purpose of fill beach nourishment
3. SHORELINE STABII.IZATION
a. Type of shoreline stabilization
Bulkhead Riprap
b. Length
c. Average distance waterward of MHW or NWL
d. Maximum distance waterward of MHW or NWL
i
Shoreline erosion during preceding 12 months
rs~.« of ~o.»~o.,~
f. Type Qf bulkhead or riprap material
g. Amount of fill in cubic yards to be placed below
water level
{1) Riprap
{2} Bulkhead backfill
h. Type of fill material
i. Source of fill material
b. Will fill material be placed in coastal wetlands
(marsh), SAVs or other wetlands?
y~ x No
If yes,
(l) Dimensions of fill area
(2} Purpose of fill
S. GENERAL
a. How will excavated or fill material be kept on site
and erosion controlled? Use of temporary training
dikes during placement.
b. What type of construction equipment will be used
(for example, dragline, bac>fioe, or hydraulic
dredge)?
Backhoe Hydraulic Dredge, Bulldozer
c. Will wetlands be cr:,ssed in transporting equipment
to project site? Yes x No
If yes, explain steps that will be taken to lessen
environmental impacts.
4. OTHER FII,L ACTNITIES
(Exctuding shoreline stabilization)
~a. Will fill material be brought to site?
x Yes vo
Mason Inlet Relocation Proiect
~~ _
Z ~ ~4n! E ~
Date
Revised 03/95

~ g~FOR~ you Bu~~o

Setting Back for Safety: A Gulde to Wise Development Along the dceanfront
When you build along the ~ceanfron t you take a cattalo ted
risk. Natural #orces of watez and wind collide with tons of
force, even on ealrn days.
~ Man-made structures cannot be guaranteed to survive the
force of a hurricane. Long-term erosion (or barrier island
~ migration) may take.from two to ten feet of the beach each
i year and, st~aner or later, wilt threaten oceanfront s#ruc-
lures. Theme are the facts of Iife for oceanfront property
~ owners.
The t::oastal Resources Commission (CRC) has adopted
rates for building along fine oceanhant. The rules are in-
tended to avoid an unreasonable risk to life and property
and to limit public and private losses from storms and
long-term emswn, These rules lessen but do not eliminate
the element of risk in oceanfront development.
As you rnn~ider building along the oceanfront the CRC
wants you t4 understa nd the rules and the risks, With this
knowledge you can make a more informed decision about
where and ho~v to build in the coastal area,
The Rules
When you Build along the oceanfront, eoast<il manage-
ment rules require that the structure be sited to fit safely
into the beach environment.
Structures along the oceanfront must be behind file frontal
dune, landward of the Crest of the primary dune and set
back #ram the first line of natural stable vegetation a dis-
tanceequal tp 30timesthe mutual erosion rate fa minimum
of 60 feet). barge structures {multi familyrQSidential struC-
tures 'eater thin 5,000 scjuare feet and non-residential
structures greater than 5,000 square feek) must be setback
from the first line of natural s#able vegetation a distance
equal to t~ tittles the annual erosion rate or 120 feet,
SE~ TsApC~p SETBACK ~,, FIRST LIN$ OF
sa x ANNUAL 3o-x ANNUiAt ~- srnaLE
L~~ ~AV£RAGE ~ AVERAGE ~ VEGE7A714N
t~ I£ROSION ~ E[tOStQN
RATE ~ AA7E
QQO ,
I t~`r.
iu.a~c ~IsM~~~
s7auCrueFS~ 1 sr0.ucTUaESS !
tivhichever is greater. If the erosion rate is greater than 3,5
feet/year, the setback is 30 times the erosion rate plus 105
feet,
TF~e Reasons
The beachfront is an ever hanging laridform. The beach
and the dunes are natural "shock absorbers", tak;ng the
beatir-gs of the winds and waves and protecting the inland
areas. By setting back 30 or 60 times the annual longg-term
erosion rate, you have a good chance of enjoying the full
Iife of the structure. At first, it seems very inviting to build
your dream house as dose to the beach as ossible, but in
five years you could find the dream has become a
roghtmare as high tides and storm tides threaten your
investment.
The Exr-option
The Coastal Resources Commission recognized that these
rules, initially passed in June of 1979, might prove a
hardship far same property owners. Therefore, then estab-
lished an exception For lots which cannot meet the "setback
reel uirement. The exceptionallows buildings in front of the
setback line if the following conditions apply:
(1) the lot must have beer- platted aS of June 1,1979, anti
notcapabie of beingeniarged by combining with adjoining
land under the same ownership, (2) developmeet must be
as far back on the pgroperty as possible ar~d in no case less
than fs0 feet landward of the vegetation tine, (3) no
development can take place on the frontal dune {4) special
cortstn~ctionstandardsonpilingdepthand squarefootage
must be met and t5) all other LAMA, state and local
regulations must be met.
The exception is not available in the Inlet Hazard Area.
To rietetmine e3igibili ty for the exception, the Local Permit
Officer will make these measurements and observations:
requfr ed setback from vegetmtion tine
exception setback (maximum fQus7ble}
rear property tine setback
TIIRX. rrllozrxxble SlI1I1tY~~OptRgC On JOZ(,p_5t floor
tot area as Calculated from vegetation fine
piling Iength needed to extend 4 feet below MSIr
PRE-PERMIT STRUCTURE; IRi~DEQUATE 5ET9ACK
PERMITTED
STRUCTURE; PRE-STORM BEACIi PROf1LE
ADEQUATE POST•STORM BEAGy PROFILE
SETBACK _
~"~ ONE YEAR AFTER STORM/BEACH REBU!l,D/NG
- +ti
A fter the stnrnt, ttre Iwuse vn the dune will begone. The other hoxse >7as a much better chance of survival.

AEC HAZARD NOTICE
Project is tfi An: ~ pcean Erodible Ar®a
Date Lot Was Platted:
High Hazard 1=1ood Area /~ inl®t Hazard ~-rea
This notice is intended to make you, the applicant, aware
of the special risks and conditions associated with
development in this area, which is subject b natural
l~2ards such as storms, erosion and currents. The rifles of
the Coastal Resources Commission require that you
receive an AEC Ha7,ard Notice and acknowledge #hat
notice in writing before a permit for development can be
issued,
'l'he Commission's reutles onbuildingstandard9,oceanfront
setbacksand dunealterationaredesignedto minimize,but
not eliminate, property lass from hazards_ gy granting
permits, the Coastal esources Commission does nat
guarantee the safetyt of the development and assumes no
inability for fgtuze de to the development,
'IY~e best available information, as accepted by the Coastal
Resources Commission, indicates that the annual ocean
erosion rate for the area where your property is located its
,~~ feet per year.
Tt-e rate was e9tablished by careful analysis of aerial
photogaphs of the coastline taken over the past 50 years,
Studies also indicate that the shoreline could move as
much as~O feet landward in a major storm.
The flood wags in a ma jot stc3rm are predicted to be about
1S2 feet deep in this area.
Pxeferred oceanfront protection measures are beach
nourishment and relocation of threatened structures.
Hard erosio#- control structures such as bulkheads,
seawalls, revetments, groins, jetties and breakwaters are
prohibited. Temporary devices, including aar~i bags, may
be allowed under certain opnriitior+s.
This structure shall be relocated or dismantled wixhin two
years of becoming imminently threatened.
The applicant must acknowledge this information and
requirements by signing this notice in the beloti* space_
Without the propez signature, the application will not be
rnmplete. /
/G ~ y..i`~~--
Applicani's Signature
cafe
SPECIAL NOTE; This hazard notice is regcued fior
development in areas subject to sudden and massive
stoma arui erosion. Permits issued for developpment in this
area expire on December 31 of the third yeaz following the
year in which the permit was issued, Shortly before wank
begins on the project site, the Local Permit Officer wiII
determine the vegetation lute and setback distance at your
site if the property has seen little change and the proposed
development can still meet the setback requirement, the
LPO will inform you thatyou ma begir} woxk. It is xmpor-
tantthatyou cl~ec[c with the I1'O before the pe.*mit expirea
for official a oval to continue the work after the permit
has expired~enerally, if foundation pilings have been
placed and substantial progress is contintur-g, permit
renewal may not be necessary. If substantial progress has
not made, the permit must be renewed and a new
setback line'esta~lished. It is unlawful to eonfinue work
after permit expiration without this approval.
For more information, contact;
i')')r' ~vbb fL(a t r5
L o ca/ Pe rm~~it --Offic--e /Ir
Address
Locality o
Phone

•
Revised r y/93

TABLE OF CONTENTS
1.0 PROJECT HISTORY AND OVERVIEW ................................................................... 1
2.0 PROJECT PURPOSE ................................................................................................. .. 4
3.0 PROPOSED PLAN ........................................................•---........................................... 5
4.0 CONSTRUCTION METHODOLOGY AND PROJECT SEQUENCING ............... 10

...........................................................................
4.1 Figure "8" Island ..........................
10
4.2 Mason Creek ........................................................................................................... 11
5.0 EXISTING ENVIRONMENT .................................................................................... 12
5.1 Waterbird Habitat .................................................................................................... 12
5.2 Shellfish, Fish, and their habitats ............................................................................ 15
6.0 TIDAL HYDRAULICS .............................................................................................. 18
6.1 Option A .................................................................................................................. 20
6.2 Option B .................................................................................................................. 21
6.3 Option C .................................................................................................................. 22
7.0 OTHER ONGOING PROJECTS ............................................................................... 25
•
PERMIT DRAWINGS ......................................................................................Appendix A
PREVIOUS/EXISTING PERMITS ..................................................................Appendix B
INLET MANAGEMENT PLAN ....................................................................... Appendix C
HYDRODYNAMIC MODELING REPORT ....................................................Appendix D

•
Project Description
•
~~~
ENCitNEfRB '~ SLiR'V'EYOfiS
•

1.0 PROJECT HISTORY AND OVERVIEW
Mason Inlet is a small mixed-energy system located within the Onslow Bay compartment
of the southeastern North Carolina coast, approximately 11 miles east of the city of
Wilmington. The inlet separates Figure "8" Island, a privately developed barrier island
located to the northeast, from the town of Wrightsville Beach, a densely populated barrier
located to the southwest (Fig. 1). The average tidal range for the project area is 3.8 ft
with spring ranges occasionally exceeding 4.6 ft; average wave height and period for the
region are Q.79 m (2.6 ft) and 7.9 seconds (JARRETT, 1977).

Figure 1. Location map showing Mason Inlet and surrounding
features.
Mason Inlet is a locatonally unstable system that has historically migrated from north to
south primarily affecting the shoreline of Figure "8" Island and the northern end of
Wrightsville Beach. In 1995, the inlet's southerly migration began to threaten upland
1

structures located on the northern end of Wrightsville Beach. In an effort to combat the
inlet's southerly migration and eventual loss of property, a temporary sand bag revetment
was constructed in 1996. The revetment remained in place until January 2002, when
New Hanover County, North Carolina undertook the relocation of Mason Inlet in order to
mitigate the southward migration of the inlet and protect existing development located on
Wrightsville Beach. The relocation project was completed on March 7, 2002 when the
inlet was moved approximately 3,000 ft to the northeast. In accordance with the Inlet
Management Plan (IMP) contained within the County's Environmental Assessment (EA),
the U.S. Army Corps of Engineers (USAGE) Permit #199901052, and the North Carolina
Department of Environment and Natural Resources (NCDENR) Permit #151-O1, a
monitoring and maintenance program was implemented to prevent Mason Inlet from
encroaching on upland structures for the 30 yr duration of the project permits. Copies of
these documents are located in Appendix B for reference.
The physical monitoring protocol is described in Section 3.1 of the IMP contained within
the project's EA and Appendix C. The accepted monitoring program consists of
conducting periodic topographic and hydrographic surveys to track changes within the
Mason Inlet system and adjacent oceanfront beaches. These surveys were conducted
quarterly for the first year of monitoring and biannually for the remaining years. Existing
survey datasets are summarized in Table 1.

2

Maintenance events and remedial actions, outlined in Section 3.3 of the IMP, were
originally planned to occur at 3-5 year intervals and consisted of routine dredging to
remove shoaled material from the designed channel segments including Mason Creek, the
Survey Date Areas Surveyed
Apr-02 Mason Inlet, Wrightsville Beach, Figure "8" Island
Juf-02 Mason Inlet, Wrightsville Beach, Figure "8" Island
Oct-02 Mason Inlet, Wrightsville Beach, Figure "8" Island
Jan-03 Mason Inlet, Wrightsville Beach, Figure "8" Island
Apr-03 Mason Inlet, Banks Channel, Wrightsville Beach, Figure "8" Island
Oct-03 Mason Inlet, Banks Channel, Wrightsville Beach, Figure "8" Island
Apr-04 Mason Inlet, Banks Channel, Wrightsville Beach, Figure "8" Island
Table 1. Information concerning surveys conducted within Mason Inlet as part of the
Mason Inlet Monitoring Project.
sedimentation basin, and the inlet channel (Appendix C). The dredged material would be
placed on the adjacent updrift and downdrift beaches of Figure "8" Island and
Wrightsville Beach, dependent upon need. Maintenance events were planned in order to
maintain the inlet within the defined inlet corridor and mitigate any adverse effects that
Mason Inlet may have on the adjacent oceanfront beaches. The IMP specifies three
system triggers designed in order to initiate inlet maintenance events. These triggers
include volumetric losses along the oceanfront shorelines of Figure "8" Island and or
Wrightsville Beach, sedimentation of Mason Inlet and the designed sedimentation basin,
and inlet migration outside of the designed inlet corridor.

3

2.0 PROJECT PURPOSE
This document has been prepared in order to implement an inlet maintenance event as
prescribed within the IMP. Trigger 2 contained within the IMP (Sedimentation of Mason
Inlet and Sedimentation Basin) has been initiated. The trigger specifies that if average
projected shoaling rates are exceeded by more than 30% for a period of 2 years, or
shoaling within the inlet exceeds the 375,000 cy capacity, a maintenance event will be
implemented. Upon examination of the survey data collected during the April 2004
survey, it has been determined that shoaling rates have been exceeded by more than 30%
for two consecutive years, and that the sediment basin has reached its designed capacity
of 375,000 cy; thus under the permitted IMP, a maintenance event is required.
Pre-project calculations of shoaling rates estimated that the inlet throat and sedimentation
• basin would shoal at a rate of about 375,000 cy per 4-5 year maintenance interval or
75,000 cy/yr. This translates to a major maintenance event every 4-5 yrs. Maintenance
events were planned to consist of removing shoaled material from within the
sedimentation basin, inlet channel, and Mason's Creek, and subsequent placement of the
material on the adjacent oceanfront beaches. Under the current maintenance protocol the
design template of the inlet channel and sedimentation basin would be re-established.
Due to current inlet shoaling rates and morphologic change of the inlet system, GBA
proposes to modify the existing maintenance protocol in order to implement a more cost-
effective, environmentally sound maintenance approach.

4

3.0 PROPOSED PLAN
Survey data collected in accordance with the permitted monitoring protocol indicate
several inconsistencies associated with pre-project estimates of shoaling within Mason
Inlet. The data show that the projected 375,000 cy of material that was predicted to enter
the system over a 4-5 yr period, actually did so within the first 9 months after project
completion, filling the sediment basin to capacity. The survey data also show that an
additional 75,000 cy of material was added to the area during year two. This material
was deposited primarily within Banks and Mason Channels. Data derived from the post-
project monitoring surveys show that the estimates of annual shoaling rates, post
equilibration, are relatively accurate, however the estimates did not take into account the
initial 375,000 cy of material that would be needed for flood-tidal delta formation. It
should be noted that during year 2, following flood and ebb-tidal delta development, the
• recorded shoaling rates mimicked those predicted from pre-construction data.
Monitoring surveys have shown that the material being transported into Mason Inlet is
primarily derived from the updrift shoreline of Figure "8" Island. The majority of the
450,000 cy of material that was transported into the inlet during the first two years after
project construction was derived from the southern 3,000 ft of the Figure "8" Island.
Losses along Figure "8" Island were expected to occur in the original project design. In
an effort to mitigate these oceanfront losses, 400,000 cy of material derived from the
excavation of the new inlet was placed along the southern 10,000 ft of the Figure "8"
Island shoreline during initial project construction. This sediment was sacrificial and
partially intended to compensate for the amount of material that would be required during
•
5

initial system equilibration. However, the majority of the sand lost from the Figure "8"
Island beach has been within the southern 3,000 feet of the nourishment area, which has
resulted in shoreline retreat beyond the pre-project condition in this area.
The quantity of material that was transported into the interior portions of the inlet channel
and sedimentation basin during the first 9 months after project construction, effectively
led to a less stable inlet configuration, as well as excessive shoaling within portions of
Banks Channel, Mason Creek, and the AIWW. Under the original permitted
maintenance plan, the material contained within the sediment basin would be removed
and placed on one of the adjacent oceanfront beaches, and the original inlet design
template re-established. Under this scenario, it is reasonable to expect that a similar
episode of massive shoaling will occur immediately following each maintenance event in
• order to establish system equilibrium and re-form the already present flood-tidal delta.
This initial shoaling will most likely take place in the same location and immediately fill
the sediment basin to capacity. Material will most likely continue to be derived from the
southern portions of Figure "8" Island, resulting in significant losses along the oceanfront
beach and dune. In order to avoid future episodes of excessive shoaling and beachfront
erosion, like the one observed after initial project construction, GBA proposes to modify
the existing maintenance protocol by implementing slow-impact maintenance approach.
The primary focus of this permit proposal is to implement a maintenance event with
modifications to the current maintenance approach. The proposed maintenance plan will
keep the main portion of the flood delta in tact and perform dredging operations in
•
6

specific areas with limited depths (Fig. 2). The areas to be dredged are located on the
periphery of the current flood shoal and will have negligible impacts on the inlet's
morphologic equilibrium. The proposed maintenance approach seeks to reduce
environmental impacts associated with large-scale dredging of the entire system
(sediment basin and channel segments), while promoting a more stable inlet
configuration.
•
Figure 2. Areas of proposed dredging. For detailed project drawing see Project
Drawings in Appendix A.
Permit objectives are to:
1) Implement a maintenance event in order to keep the inlet within the prescribed
area and ameliorate shorefront losses on adjacent beaches.
•
7

2) Lessen environmental and financial impacts through the application of land-
based excavation on Figure "8" Island shoulder, with conventional dredging
utilized only in Mason Creek.
3) Leave newly formed flood-tidal delta in place, in order to prevent episodes of
inlet-induced large-scale oceanfront erosion along the southern end of Figure
"8" Island, and to promote inlet morphologic and spatial stability.
The proposed maintenance project has two distinct excavation sections consisting of the
southern end of Figure "8" Island and Mason Creek. Due to extensive shoaling within
the inlet and flood shoal areas, the southern end of Figure "8" Island has accreted greatly.
High ground now extends completely across the western end of the designed inlet
channel and the intertidal margins encompass virtually the entire sediment basin area.
This area will be excavated to -5.0 feet NGVD (~3 ft MLW). The planned excavation
for these areas will be performed mechanically, using land-based excavation equipment
and hauled to the nourishment area. Approximately 45% of this material excavated
mechanically will be used to restore the eroded dunes to an elevation and width
consistent with pre-project conditions (Elev. 14.0' NGVD and approximately 40 ft crest
width). The remaining 55% will be used for the upland portion of the nourishment that
will extend 50 feet seaward of the dune at elevation 7.0' NGVD. For Mason Creek,
material will be dredged hydraulic and be placed along the shoreface of the nourishment
area to complete the 1 Ver.: 30 Hor. beachslope beyond mean low water. See Sheet 8 for
detailed cross-sections.
•
8

• According to the April 2004 surveys, it is estimated that the proposed project will
excavate approximately 184,000 cubic yards of beach quality sand from a 22.6 acre tract
within the inlet channel, sediment basin, and Mason Creek. The material will be placed
along a 4,500 linear foot section starting approximately 1,200 feet from the inlet
shoulder, extending north. It is estimated that the proposed nourishment area will be
approximately 49.5 acres, extending from the existing dune to approximately 200 feet
beyond mean low water.

•
9

4.0 CONSTRUCTION METHODOLOGY AND PROJECT SEQUENCING
• As described above, the proposed project intends to use a combination of land-based
excavation equipment and conventional hydraulic dredging to remove shoal material and
renourish the beach along the southern portion of Figure 8 Island. It is anticipated that
the project will be performed during the first quarter of 2005 and require less than 60
days to complete including mobilization and demobilization. It is expected that hydraulic
dredging within Mason Creek and mechanical excavation within the inlet area will be
performed concurrently.
4.1 Figure "8" Island
Removal of material from the southern end of Figure "8" Island will be performed
utilizing excavator and off-road dump trucks. The shoal area is approximately 38%
• upland and 62% inter-tidal.. The area includes the tidal flat that is exposed during half of
the tide cycle. During the lower half of the tide cycle, excavation equipment will be
moved out onto the shoal and excavate the seaward edge of the flat. As the tide rises,
equipment will be moved landward and work on the upland portion of the shoal area.
Material will be loaded into trucks and hauled along the shorefront and placed within the
dune and upper portion of the nourishment template. Bulldozers will grade the material
to the appropriate elevation and slope. Utilizing two (2) excavators, six (6) off-road
dump trucks, and two (2) bulldozers, it is estimated that the excavation of the shoal will
require 42 working days and 3 days each of mobilization and de-mobilization.
•
10

4.2 Mason Creek
• Mason Creek will be dredged to the previous design template of 80 ft wide and -10.0 ft
NGVD (~8 ft MLW) using a hydraulic pipeline dredge. The material will be placed on
the shorefront slope of the nourishment area and bulldozers will be used to grade the
material to design slope. Due to draft limitation within Mason Creek and the inlet, the
dredge will start operations at the AIWW end of Mason Creek and work seaward. The
pipeline will be routed along the shoreline of Mason Creek, along the north corridor limit
and down the beach along the seaward edge of the dune. Shoaling within the AIWW is
an ongoing process. Prior to demobilization any material within the AIWW channel
between Stations 78+00 and 110+00 will be removed.
The estimated production rate for the dredge is 2,500 cubic yards per day and the
operation will take approximately 27 days to complete. Mobilization and pipeline setup
will take approximately one week. The dredging operations should be scheduled to begin
7 to 10 days after in order to be completed simultaneously with the land-based
excavation. Demobilization and cleanup will require approximately one week.
•
11

5.0 EXISTING ENVIRONMENT
• All work will be confined to previously disturbed areas. The existing environmental
components of the project area have been previously outlined in the original project
Environmental Assessment (EA). The majority of these components including land use,
waves and littoral processes, unique agricultural lands, public lands, recreational and
scenic areas, areas of archeological or historic values, air quality, water resources, water
quality, groundwater quality, introduction of toxic substances, noise levels, water supply
and wastewater systems, shellfish/fish habitats, threatened and endangered species, and
sediment characteristics have remained unchanged. Information concerning these
environment conditions, and effects of the project on those environments, can be found in
Chapter 2 and Chapter 5 of the project EA prepared by Applied Technology Management
(ATM). Specific items that vary from the original conditions, including tidal hydraulics,
• essential fish habitat (EFH), and Waterbird habitat are addressed below.
5.1 Waterbird Habitat
As part of the 30 yr federal permit, the Applicant has been required to develop a
Waterbird Habitat Management Plan. This plan was initiated after project construction
and finalized May 18, 2004. As part of the plan, the Applicant is required to monitor the
recovery and development of three habitat types within the inlet system. The three types
of habitats include supra-tidal sand spits suitable for nesting, inter-tidal sand flats for
foraging areas, and sub-tidal areas. The original project impacted a 120-acre area that
includes the existing inlet area, as well as the previous inlet fill area. This maintenance
project will not require any activities on the Wrightsville Beach side of the inlet, thus all
•
12

impacts will be confined to the inlet channel, sediment basin, Mason Creek and the
• southern end of Figure "8" Island. There may be limited disturbance to birds on the
Wrightsville Beach side of the inlet due to equipment noise or movement within the
project area, but there will be no traffic or direct disturbance within the Waterbird
Protection Area or the inter-tidal flats adjacent to it. The total area of direct impact is 80
acres inclusive of the 5-acre transport corridor between the excavation area and the beach
nourishment area. The area of potential habitat impact for waterbirds within the
excavation area includes 4.2 acres of supra-tidal sand spit and 6.9 acres of inter-tidal sand
flats along the north shoulder of the inlet. This area is entirely within the original design
template and was planned for disturbance during this and future maintenance events. The
original maintenance plan did not anticipate disturbance of any potential nesting habitat,
mainly because it was not anticipated that the shoal formation between maintenance
• events would create upland areas. Although if left undisturbed, this area could
potentially be suitable for nesting, excavation of this area is necessary and unavoidable if
the inlet is to be maintained within the designated inlet corridor. Every effort has been
made to minimize impacts to waterbirds in this project design while still incorporating
necessary design criteria. These are listed below.
1) Minimization of the excavation area and equipment access area.
The northern extent of the excavation area has been limited to 150 south of the
northern corridor limit so that vehicular and equipment movement along the inlet
shoulder will be limited to within the inlet corridor limits.

13

2) Use of land-based excavation equipment on the inlet shoulder.
• Use of land-based equipment will allow minimal excavation depths along the inlet
shoulder (-3.0 ft MLW}. This will minimize loss of additional habitat outside the
corridor immediately post project, as happened after initial construction due to
inlet equilibration. In addition, use of this type of equipment along the inlet
shoulder coincident to dredging activities in Mason Creek will minimize the
period of disturbance.
3) Time period for operations.
The project will be performed in the latter half of the dredging window {January-
March) in order to avoid disturbance of piping plover nesting habitat during the
prime nesting season. It is our understanding that this is the USFWS preferred
period for construction. If there are alternative windows for construction that will
be less impactive for all species concerned, the construction period will be altered
so long as the provided timeframe is adequate for project completion.
4) Equipment access route.
The only guaranteed equipment access on Figure "8" Island is located at the north
end of the island between 5 Surf Court and 7 Surf Court, approximately 3 miles
from the construction area. Undeveloped properties do exist within the
nourishment area, which have been previously used for equipment access. Every
effort will be made to gain access through those properties in order to minimize
traffic on the beach. If this cannot be done, it is understood that there may be
limited disturbance along the Island's shorefront during the equipment
mobilization and demobilization periods, as well as times when conveyance of
•
14

supplies such as fuel or repair equipment is needed. During the project, access
along the beachfront shall be limited to the bottom half of the tide cycle and
require equipment and vehicles to operate only on the wet sand area and at
minimal speed. Access during the high tide period will be granted only for
emergency situations.
5.2 Shellfish, Fish, and their habitats
Sections 2.18 and 5.18 of the original Environmental Assessment addresses impacts to
shellfish, fish and their habitats, including Essential Fish Habitats, as outlined by the
provisions of the Magnuson-Stevens Fishery Conservation and Management Act. The
EA addressed impacts both for the original project and future maintenance events. The
direct impacts of the construction operations will not vary from those addressed by the
EA, however the EA did purport that their would be improvements to water quality.
Studies done on the subsequent benefits to water quality within the estuary described in
the EA have been inconclusive. The University of North Carolina at Wilmington
performed post project water quality surveys within Howe Creek (Mallin 2003), and
found no distinguishable improvement to water quality. Hydrodynamic modeling
performed by the applicant in August 2003 (GBA, ACRE 2003) indicated that, although
entrance to Howe Creek was in very close proximity to the inlet (1500 ft south of the
inlet), it is not within the service area of Mason Inlet. The modeling showed that tidal
flow within the estuary is dominated by Masonboro Inlet and that Mason Inlet only
services Middle Sound north of Mason Inlet and south of the Figure "8" Island
Causeway. Thus the data is inconclusive because the study area was not within the tidal
•
15

exchange area of Mason Inlet. Non-standardized observations, including the rapid
success of the Mitigation Island marsh and good shellfish harvests from the area, indicate
that the inlet project may be having a positive effect of the health of the estuary.
With regards to impacts on Inter-tidal Flats, the Section 5.18 of the EA indicated that the
design of the projects would trap sand within the sediment basin and prevent sand loading
within Mason Creek and the adjacent estuary. The six survey monitoring reports (GBA
06/02 through 04/04) indicate that there has been deposition within the creek system. All
survey profiles conducted extend 200 ft outside the creek channel. The surveys show that
deposition within the creek has been limited to the creek bed, and has not affected
adjacent marsh or inter-tidal flats. The hydrodynamic modeling indicates that after
completion of this maintenance project, that shoaling within the creek will again occur
• within Mason Creek, but at a slower rate.
As with all beach nourishment projects, the dredging and sand placement activities can
have impacts to the local fauna. In order to minimize these activities the project will
include the following safeguards:
1) Mechanical excavation equipment will be used on the inlet shoulder, which will
minimize turbidity.
2) Dredging and beach nourishment activities will occur in the winter months when
habitat utilization is minimal.
3) Temporary training dikes will be required during the hydraulic placement
activities to minimize turbidity in the surf zone.

16

4) Nourishment activities will be postponed during periods of extreme weather to
minimize turbidity and sand placement outside the nourishment template.

17

6.0 TIDAL HYDRAULICS
Tidal inlet morphology is controlled primarily by the complex interaction between tidal
currents, wave energy, and sediment supply. Changes in any of these controlling
variables may result in large-scale morphologic adjustments within an inlet system.
Dredging operations have been shown to have considerable effects on altering tidal
hydraulics within an inlet setting. Changes in tidal flow including current speed, flow
duration, and most importantly tidal prism, may have negative effects on inlet
morphology, resulting in potential impacts to adjacent oceanfront beaches. Generally, an
increase in tidal prism will result in exacerbated oceanfront erosion within the updrift and
downdrift zones of inlet influence due to the inflation of inlet-related sand bodies such as
the ebb-tidal delta. Conversely, when tidal prism is decreased, locational stability may be
reduced resulting in the onset of inlet migration. In the case of Mason Inlet, detailed
• investigations have been conducted, to identify potential impacts that dredging operations
may have on the stability of the inlet system, and the associated impact on adjacent
oceanfront beaches. These investigations include a study conducted by ATM in 1999 and
a more recent investigation conducted by GBA/ACRE in 2003; both documents contain
detailed information concerning system hydraulics (Appendix D).
The proposed maintenance plan outlined within this document, seeks to reduce the
potential impacts that dredging operations may have on tidal hydraulics within the Mason
Inlet system, through reducing the affected area and minimizing excavation depths. The
permitted maintenance plan found within the project's IMP calls for system wide
dredging including Mason Creek, the inlet channel, and sedimentation basin to re-

18

establish the original project template. Because of the excessive shoaling within the inlet
and the associated shorefront erosion that occurred immediately post-project, an analysis
of various dredging plans was performed in July 2004, to insure the most economical and
beneficial approach. Although many potential configurations were considered, the
analysis was narrowed to three potential scenarios for modeling. These scenarios
included hydrodynamic modeling of the existing conditions, the original maintenance
dredging plan, and two dredging alternatives. One alternative included "inverting" the
sediment basin so that the largest portion was on the northern side of the inlet channel.
The second option involved dredging only Mason Creek. This option also modeled
potential impacts from the proposed Banks Channel maintenance project, including
extension of the project 1000 ft south of the southern-most lagoon. The models looked
at four (4) areas of concern:
• 1) Overall Sedimentation Potential -Would the relative probability for material to
be transported into the inlet system be different for alternate configurations,
and would the expected maintenance interval be altered?
2) Migration Potential -Would varying the dredge template alter the potential
for the inlet to migrate one direction or the other?
3) Sedimentation Potential outside the project area -How would a maintenance
event affect shoaling in the AIWW and Banks Channel, and would altering
the dredging designs improve the shoaling rates?
4) Effects of Other Projects -Permitting of maintenance dredging within Banks
Channel was in progress. How would this project affect the inlet?
•
19

Sediment transport modeling is not a finite science, thus information derived from the
• models must be looked at in relative terms to a defined baseline condition. The baseline
condition for the study was derived from the April 2003 monitoring surveys. The
baseline model predicted erosion and accretion trends for the inlet system based on the
existing condition without modification. Predicted erosion and accretion trends were
then groundtruthed, using actual volume calculations and shoreline movements from the
October 2003 surveys. Because the data used to truth the model was taken after the
modeling efforts were performed, the models did not contain any user bias toward a
desired outcome.
6.1 Option A
The permitted maintenance template included reconstructing the inlet channel sediment
basin and Mason Creek to the original design depths and widths. When this scenario was
modeled, the outcome showed that sediment potential within the inlet and basin area
would be greatly increased, while Mason Creek showed an increase potential for
scouring, particularly in the channel curves (Fig. 3). The model also showed that
shoaling potential within the AIWW would likely increase significantly after the
maintenance event.
•
20

•
Figure 3. Erosion/deposition potential. for Option A (permitted
maintenance plan). Red indicates erosion potential, green indicates
potential for deposition.
6.2 Option B
• The first alternate dredging plan included the same template within the inlet and Mason
Creek, but inverted the sediment basin so that the largest capacity was north of the inlet
(Fig. 4). Monitoring surveys indicated that shoal formation after construction occurred
predominately north of the main inlet channel, primarily attributed to tidal flows into
Banks Channel. It was hoped that by placing the majority of the sediment basin on the
north side of the channel, more material would be drawn into the basin, rather than
carried into the AIWW, however this was not the case. The Option B design did not
show significant improvement over the original design.
•
21

•
Figure 4. Erosion/deposition potential for Option B (inverted
sedimentation basin). Red indicates erosion potential, green indicates
potential for deposition.
6.3 Option C
. The third option analyzed included dredging only within Mason Creek. Option C also
looked at the potential maintenance dredging project within Banks Channel (Fig. S).
Dredging within Banks Channel has been a concern throughout the engineering process.
During the initial permitting process, it was touted that previous dredging operations
within Banks Channel had exacerbated the migration of Mason Inlet. Subsequent
modeling efforts have shown that this probably wasn't the case, rather an overall
reduction in the inlet's tidal prism and eventual channel cross-sectional instability caused
the onset of migration. The conducted model also showed that of the four options
examined, Option C produced the most favorable erosion/deposition conditions, and
provided the most stable conditions.
•
22

•
Figure S. Erosion/deposition potential for Option C (Mason Creek and
Banks Channel). Red indicates erosion potential, green indicates
potential for deposition.
The proposed maintenance strategy outlined in this document is based on the information
• and findings of the previously mentioned modeling effort conducted by GBA/ACRE in
2003 and mimics most of the conditions presented in Option C. A detailed explanation of
the original Option C conditions may be found in the modeling report located in
Appendix D and entitled "Mason Inlet and Middle Sound System New Hanover County,
NC. Hydrodynamic Modeling and Sediment Transport Analyses of Present Conditions
and Dredging Alternatives" (Kelley and Ramsey, 2003). During a preliminary meeting
on May 6, 2004 with representatives from the U.S. Army Corps of Engineers (USAGE)
and the North Carolina Division of Coastal Management (NCDCM), Option C was
outlined for initial comment. It was determined at that meeting that excavation between
the inlet and 200 ft south of the southern lagoon would require significant review and
reassessment by both state and federal agencies. Given the urgency of the proposed
• maintenance event and the time that would be required in order to permit new work
23

within the southernmost portion of Banks Channel, it was decided that the applicant
• would forego dredging activities in that area. The resulting maintenance strategy will
involve the removal of material only from within Mason Creek and along the Figure "8"
Island shoulder. Dredging within Banks Channel is not being requested at this time in
part due to time constraints associated with the permitting of "new work" and the
environmental dredging window. In addition, review of the plans for Figure "8" Island
maintenance project indicate that the dredge depth will be sufficient to allow considerable
shoaling without hindering navigation. Figure "$" Island's planned dredge depth within
Banks Channel (-9 MLW) should compensate for material moving into that portion of the
Mason Inlet system. The resulting channel configurations are expected to behave similar
to the configurations outlined in Option C of the modeling report.

•
24

7.0 OTHER ONGOING PROJECTS
• As mentioned through this project description, the Figure "8" Island Beach Homeowners'
Association currently has a permit under review for maintenance dredging in Banks
Channel, and subsequent placement of the dredge material on the shorefront along the
southern end of Figure "8" Island. Numerous regulatory and environmental groups have
expressed varying levels of concern over these two projects being permitted separately
yet being constructed simultaneously. This is understandable given the complexity of
inlet systems and the overlap of beach nourishment areas. The two primary concerns are
the effects of the Banks Channel project on Mason Inlet's stability and the combined
effects of the beach re-nourishment resulting from the two projects. As described in the
Tidal Hydraulics section of this document, the effects of different dredging templates, as
well as the effect of the Banks Channel project on the Inlet's stability were carefully
• considered.
The use of contiguous beach nourishment areas is another item of concern that has been
expressed. The southern end of Figure "8" Island has been an erosional "hotspot" over
the years for various reasons. Prior to the implementation of the Mason Inlet Project, the
southern end of the island had erosion issues due to the actual migration of the inlet and
subsequent sand starvation. The Figure "8" Homeowners' Association addressed this
issue through a series of beach renourishment projects. Subsequent to the relocation of
the inlet, inlet-induced erosion during the equilibration period has resulted in the loss of
the beach built during the initial inlet project. Maintaining the location and size of the

25

inlet through pro-active maintenance may, in time, result in lower erosion rates within
this area.
However, at this time property protection within this area is a serious concern for both
applicants. The Banks Channel project is addressing this issue by following the State's
policy that beach quality material removed from navigation projects be returned to the
oceanfront littoral system. The Mason Inlet Project will do the same through the
provision of the IMP that requires maintenance material to be placed in the area of
greatest need. The two projects propose to place a combined total of approximately
410,000 cy of sand along a 10,000 ft stretch of beach. This quantity is approximately
100,000 cy less than the quantity that would be placed, if the Mason Inlet project were to
be excavated to the initial design template, and the combined nourishment from the two
projects will not exceed the state's SOcy/ft standard for small-scale beach nourishment.
Because the combined beachfront placement for the two projects and the construction
timing are similar to those addressed in the Mason Inlet IMP, the total impact to this
beachfront has been previously addressed within the Mason Inlet EA. In summary, the
effects of the Banks Channel project on the hydraulics of Mason Inlet have been studied
and determined to be neutral or mildly positive. Additionally the total quantity of beach
nourishment from the two projects is less than the amount previously reviewed for the
Mason Inlet Project alone.

26

•
Appendix A
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7

APPENDIX B
PREVIOUS/EXISTING PERMITS
• • •

•
Appendix B
Previous/Existing Permits
•
~~
~~~ # „~
•

•
U.S. Armv Corps of Engineers
Permit#199901052
•
~~
#~

•
December 14, 2001
Regulatory Division
Action ID. 199901052
Mr. Dave Weaver
Assistant County Manager
New Hanover County
414 Chestnut Street
Wilmington, North Carolina 28401
Dear Mr. Weaver:
in accordance with your written request, and the ensuing administrative record, enclosed is a
Department of the Army (DA) permit to relocate Mason Inlet, excavate Mason Creek, construct a
sediment basin, and renourish the southern end of Wrightsville Beach, including maintenance
activities for thirty years. The project is located adjacent to the Atlantic Intracoastal Waterway
(t?-IWV~ and the Atlantic Ocean, in Wrightsville Beach and Figure Eight Island, New Hanover,
North Carolina.
If any change in the authorized work is required because of unforeseen or altered conditions
or for any other reason, the plans revised to show the change must be sent promptly to this office.
Such action is necessary, as revised plans must be reviewed and the permit modified.
Carefully read your permit. The general and special conditions are important. Your failure
to comply with these conditions could result in a violation of Federal law. Certain significant
general conditions require that:
a. You must complete construction before December 31, 2031.
b. You must notify this office in advance as to when you intend to commence and
complete work.
c. You must allow representatives from this office to make periodic visits to your
worksite as deemed necessary to assure compliance with permit plans and conditions.
•

• -2-
Should you have questions, please contact Mr. Keith Harris, Chief of the Wilmington
Regulatory Field Office at [phone]. FILENAME:mason68.12a
CESAW-RG-IJHARRIS/ ~
Sincerely, CESAW-OC
CESAW-RG,~~FR~F1- T~'
CESAW-OPBUTLER
CESAW-DXBURCHR
CESAW-DDPM/TICKNER
James W. DeLony CESAW-DD/SHEPARD
Colonel, U.S. ArmyCESAW-DE/DELONY/s ~~
District Engineer MAIL
CESAW-RG/FILE
Enclosures
Copy Furnished with enclosures:
Chief, Source Data Unit
NOAA/National Ocean Service
ATTN: Sharon Tear N1CS261
1315 East-west Hwy, Rm 7316
Silver Spring, MD 20910-3282
Copies Furnished with special conditions
and plans:
U.S. Fish and Wildlife Service
Fish and Wildlife Enhancement
Post Office Box 33726
Raleigh, North Carolina 27636-3726
Mr. William L. Cox, Chief
Wetlands Protection Section -Region N
Water Management Division
U.S. Environmental Protection Agency
b 1 Forsyth Street
Atlanta, Georgia 30303
Mr. Doug Huggett
Division of Coastal Management
North Carolina Department of
Environment and Natural Resources
1638 Mail Service Center
Raleigh, North Carolina 27699-1638
Mr. Ron Sechler
National Marine Fisheries Service
Pivers Island
Beaufort, North Carolina 28516
BCF:
CESAW-RG-L/HARRIS
CESAW-RG-L/PENNOCK
Mr. David Rackley
National Marine Fisheries Service
219 Fort Johnson Road
Charleston, South Carolina 29412-9110
~ f ~~/`°/
C3~.,~ P/
~a,n ~ ~`~~~r~ ~ U
r:

~~ ,
•
A licant: NEW HANOVER COUNTY File Number: 199901052 Date: 12 Dec 2001
Attached is: See Section below
X INITIAL PROFFERED PERMIT Standard Permit or Letter of ermission A
PROFFERED PERMIT Standard Permit or Letter of ernussion B
PERMIT DENIAL C
APPROVED JURISDICTIONAL DETERMINATION D
PRELIMINARY JURISDICTIONAL DETERMINATION E
SECTIO~T~Y The following~dentifes your nghts and options~~xc~axdmg.,..~r ailministra~'Lv
,,~~~appeal of the.atio~~e+
,
decision. Additional information niay be~,found at http://tisace~u l~iy.nu~Uinet/functions/cw/~ecwo/reg
'or~
~
,
Co -s re ulations at 33 CFA Part 331. -. ,~ -j r y~ ~ ~ ~, . '
A: INITIAL PROFFERED PERMIT: You may accept or object to the permit.
• ACCEPT: If you received a Standard Permit, you may sign the permit document and return it to the district engineer for final
authorization. If you received a Letter of Permission (LOP), you may accept the LOP and your work is authorized. Your
signature on the Standard Permit or acceptance of the LOP means that you accept the permit in its entirety, and waive all rights
to appeal the permit, including its terms and conditions, and approved jurisdictional determinations associated with the permit.
• OBJECT: If you object to the permit (Standard or LOP) because of certain terms and conditions therein, you may request that
the permit be modified accordingly. You must complete Section II of this form and return the form to the district engineer.
Your objections must be received by the district engineer within 60 days of the date of this notice, or you will forfeit your right
to appeal the permit in the future. Upon receipt of your letter, the district engineer will evaluate your objections and may: (a)
modify the permit to address all of your concerns, (b) modify the permit to address some of your objections, or (c) not modify
the permit having determined that the permit should be issued as previously written. After evaluating your objections, the
district engineer will send you a proffered permit for your reconsideration, as indicated in Section B below.
PROFFERED PERMIT: You may accept or appeal the permit
• ACCEPT: If you received a Standard Permit, you may sign the permit document and return it to the district engineer for final
authorization. If you received a Letter of Permission (LOP), you may accept the LOP and your work is authorized. Your
signature on the Standard Permit or acceptance of the LOP means that you accept the permit in its entirety, and waive all rights
to appeal the permit, including its terms and conditions, and approved jurisdictional determinations associated with the permit.
• APPEAL: If you choose to decline the proffered permit (Standard or LOP) because of certain terms and conditions therein
you
,
may appeal the declined permit under the Corps of Engineers Administrative Appeal Process by completing Section II of this
form and sending the form to the division engineer. This form must be received by the division engineer within 60 days of the
date of this notice.
C: PERMIT DENIAL: You may appeal the denial of a permit under the Corps of Engineers Administrative Appeal Process
by completing Section II of this form and sending the form to the division engineer. This form must be received by the division
engineer within 60 days of the date of this notice.
D: APPROVED JURISDICTIONAL DETERMINATION: You may accept or appeal the approved JD or
provide new information.
• ACCEPT: You do not need to notify the Corps to accept an approved JD. Failure to notify the Corps within 60 days of the date
of this notice means that you accept the approved JD in its entirety, and waive all rights to appeal the approved JD.
• APPEAL: If you disagree with the approved JD, you may appeal the approved JD under the Corps of Engineers Administrative
Appeal Process by completing Section II of this form and sending the form to the division engineer. This form must be received
by the division engineer within 60 days of the date of this notice.
E: PRELIMINARY JURISDICTIONAL DETERMINATION: You do not need to respond to the Corps
regarding the preliminary JD. The Preliminary JD is not appealable. If you wish, you may request an
pproved JD (which may be appealed), by contacting the Corps district for further instruction. Also you may
rovide new information for further consideration by the Corps to reevaluate the JD.

I I .: ~`
SECTION IT=REQUEST FOR APPEAL ~or OB7ECTI,ONS TO'AN~TN~T~ATI~PROFFE~2ET~~P~ER~111' "~~ ~~~,u
w „~ .~ ~ ,, rr ~ 4, ~ ~ ~~
REASONS FOR APPEAL OR OBJECTIONS: (Describe your reasons for appealing the decision or your objections to an
initial proffered permit in clear concise statements. You may attach additional information to this form to clarify where your reasons
or objections are addressed in the administrative record.)
ADDITIONAL INFORMATION: The appeal is limited to a review of the administrative record, the Corps memorandum for the
record of the appeal conference or meeting, and any supplemental information that the review officer has determined is needed to
clarify the administrative record. Neither the appellant nor the Corps may add new information or analyses to the record. However,
you may provide additional information to cIarifv the location of information that is ah•eadv in the adnnistrative record.
If you have questions regarding this decision and/or the appeal
process you may contact:
Mr. Keith Hams
U.S. Army Corps of Engineers, Wilmington District
Post Office Box 1890
Wilmington, North Carolina 28402-1890
~~
_ ,~~
v1ATI,ON
If you only have questions regarding the appeal process you may
also contact:
Mr. Arthur Middleton, Administrative Appeal Review Officer
CESAD-ET-CO-R
U.S. Army Corps of Engineers, South Atlantic Division
60 Forsyth Street, Room 9M15
Atlanta, Georgia 30303-8801
RIGHT OF ENTRY: Your signature below grants the right of entry to Corps of Engineers personnel, and any government
consultants, to conduct investigations of the project site during the course of the appeal process. You will be provided a 15-day
notice of any site investigation, and will have the opportunity to participate in all site investigations.
Date:
of appellant or
DIVISION ENGINEER:
Commander
U.S. Army Engineer Division, South Atlantic
60 Forsyth Street, Room 9M15
Atlanta, Georgia 30303-3490
Telephone number:

.~
.: .
~ -~
DEPARTMENT OF THE ARMY PERMIT
Permittee NEW HANOVER COUNTY
Permit No. 199901052
Issuing Office CESAW-RG-L
NOTE: The term "you" and its derivatives, as used in this permit, means the permittee or any future transferee. The term "this
office" refers to the appropriate district or division office of the Corps of Engineers having jurisdiction over the permitted
activity or the appropriate official of that office acting under the authority of the commanding officer.
You are authorized to perform work in accordance with the terms and conditions specified below.
Project Description: To relocate Mason Inlet, excavate Mason Creek, construct a sediment basin, and
renourish the southern end of Figure Eight Island or the northern end of Wrightsville Beach,
including maintenance activities for thirty years.
Project Location: Adjacent to the Atlantic Intracoastal Waterway (AIWW) and the Atlantic Ocean, in
Wrightsville Beach and Figure Eight Island, New Hanover County, North Carolina.
Permit Conditions:
General Conditions:
1. The time limit for completing the work authorized ends on December 31, 2031 If you fmd that you need more time
to complete the authorized activity, submit your request for a time extension to this office for consideration at least one month
before the above date is reached.
2. You must maintain the activity authorized by this permit in good condition and in conformance with the terms and
conditions of this pemut. You are not relieved of this requirement if you abandon the permitted activity, although you may
make a good faith transfer to a third party in compliance with General Condition 4 below. Should you wish to cease to
maintain the authorized activity or should you desire to abandon it without a good faith transfer, you must obtain a
modification of this permit from this office, which may require restoration of the area.
3. If you discover any previously unknown historic or archeological remains while accomplishing the activity authorized by
this permit, you must immediately notify this office of what you have found. We will initiate the Federal and state
coordination required to determine if the remains warrant a recovery effort or if the site is eligible for listing in the National
Register of Historic Places.
ENG FORM 1721, Nov 86 EDITION OF SEP 82 IS OBSOLETE. (33 CFR 325 (Appendix A))
•

~.
• ,
4. If you sell the property associated with this permit, you must obtain the signature of the new owner in the space provided
and forward a copy of the permit to this office to validate the transfer of this authorization.
5. You must allow representatives from this office to inspect the authorized activity at any time deemed necessary to ensure
that it is being or has been accomplished in accordance with the terms and conditions of your permit,
Special Conditions:
SEE ATTACHED SPECIAL CONDITIONS
Further Information:
1. Congressional Authorities: You have been authorized to undertake the activity described above pursuant to:
(X) Section 10 of the Rivers and Harbors Act of 1899 (33 U.S.C. 403).
(X) Section 404 of the Clean Water Act (33 U.S.C. 1344).
( ) Section 103 of the Marine Protection, Research and Sanctuaries Act of 1972 (33 U.S.C. 1413).
2. Limits of this authorization.
• a. This permit does not obviate the need to obtain other Federal, state, or local authorizations required by law.
b. This permit does not grant any property rights or exclusive privileges.
c. This permit does not authorize any injury to the property or rights of others.
d. This permit does not authorize interference with any existing or proposed Federal project.
3. Limits of Federal Liability. In issuing this permit, the Federal Government does not assume any liability for the following:
a. Damages to the permitted project or uses thereof as a result of other permitted or unpermitted activities or from natural
causes.
b. Damages to the permitted project or uses thereof as a result of current or future activities undertaken by or on behalf
of the United States in the public interest.
c. Damages to persons, property, or to other permitted or unpermitted activities or structures caused by the activity
authorized by this permit.
d. Design or construction deficiencies associated with the permitted work.
2

e. Damage claims associated with any future modification, suspension, or revocation of this permit.
4. Reliance on Applicant's Data: The determination of this office that issuance of this permit is not contrary to the public
interest was made in reliance on the information you provided.
5. Reevaluation of Permit Decision. This office may reevaluate its decision on this permit a# any time the circumstances
warrant. Circumstances that could require a reevaluation include, but are not limited to, the following:
a. You fail to comply with the terms and conditions of this permit.
b. The information provided by you in support of your permit application proves to have been false, incomplete, or
inaccurate (See 4 above).
c. Significant new information surfaces which this office did not consider in reaching the original public interest decision.
Such a reevaluation may result in a determination that it is appropriate to use the suspension, modification, and revocation
procedures contained in 33 CFR 325.7 or enforcement procedures such as those contained in 33 CFR 326.4 and 326.5. The
referenced enforcement procedures provide for the issuance of an administrative order requiring you to comply with the terms
and conditions of your permit and for the initiation of legal action where appropriate. You will be required to pay for any
corrective measures ordered by this office, and if you fail to comply with such directive, this office may in certain situations
{such as those specified in 33 CFR 209.170) accomplish the corrective measures by contract or otherwise and bill you for the
cost.
6. Extensions. General condition 1 establishes a time limit for the completion of the activity authorized by this permit, unless
there are circumstances requiring either a prompt completion of the authorized activity or a reevaluation of the public interest
decision, the Corps will normally give favorable consideration to a request for an extension of this time limit.
Your signa a below, as permittee, indicates that you accept and agree to comply with the terms and conditions of this permit.
. /~~/~ ~DI ~--
(LJf<~l E)~ t~,11~tlC./ v~~0~ ~ t CO~~SI~~IS (DATE)
This pemut $ecomes effective when the ~eder~l off cial, designated to act for the Secretary of the Army, has signed below.
fs'~ ~ ~' ~c%z o ~
BR) JAMES W. De ONY, COLONEL (DATE)
the structures or work authorized by this permit are still in existence at the time the property is transferred, the terms and
conditions of this permit will continue to be binding on the new owner(s) of the property. To validate the transfer of this
permit and the associated liabilities associated with compliance with its terms and conditions, have the transferee sign and date
below.
(TRANSFEREE)
(DATE)
'U.S. GOVERNMENT PRINTING OFFICE: 1986 - 717-425

.~;
y
PERMIT CONDITIONS
1. The work will be constructed in strict accordance with the attached plans and all conditions
of this permit. In addition, all initial work will be constructed in strict accordance with the
constructian methods and sequencing as described in Section 1.3 of the Corps Environmental
Assessment (EA).
2. The permittee shall conduct all work, both new construction and maintenance, between
November 15 and March 30 of any year unless an exemption or extension has been specifically
requested from and approved by the Corps of Engineers.
3. The permittee shall not perform any maintenance or other work after completion of initial
construction of the project without providing a written report identifying the need for the
maintenance event. The permittee must submit this report to the Corps at least 120 days before
maintenance activities are anticipated. Each request will include monitoring data and analyses.
The Corps will coordinate with other Federal and state resource agencies. The Corps will
evaluate each maintenance request to insure that project impacts, including cumulative effects,
are reasonable, that the mitigation is appropriate, and that the maintenance cycles are as widely
spaced as practicable considering the need of the maintenance activity to stabilize the inlet within
the inlet corridor.
4. The permittee shall provide advanced notice and arrange apre-construction meeting among
the Corps, U.S. Fish and Wildlife Service (Service), North Carolina Division of Coastal
Management {NCDCM), the applicant, and all contractors within 30 days of construction in
order to discuss all permits and permit conditions, and to address all questions and concerns
regarding the project. No construction or maintenance event will begin until the applicant and all
contractors are aware of and fully understand the intent of all permit conditions.
5. Prior to the start of construction ar any maintenance event, bathymetric surveys will be taken
of all areas to be temporarily or permanently impacted. These surveys will be submitted to the
Corps and include the following: aerial photography; beach and offshore profiles; new inlet area,
sedimentation basin area, existing inlet area, Mason Creek area and Atlantic Intracoastal
Waterway area. Following completion of the initial construction or any maintenance event,
temporary work areas, including stockpiles, will be returned to pre-project contours based on the
surveys. Post-project surveys will be taken of all restored temporary work areas. These surveys
will be submitted to the Corps for verification that restoration is adequate. Restoration will be
considered satisfactory only upon receipt of the Corps' approval.
6. Monitoring is required as follows. At the anniversary of the completion of construction a
report will be provided to the Corps analyzing the data and providing an executive summary of
impacts of the project and mitigation accomplished. The monitoring requirements will be
reviewed and modified as appropriate in conjunction with the Corps review of a maintenance
event.
•

.s
• s f
a. The permittee shall establish a minimum of three permanent monitoring transects
(minimum distance 600 feet) in Mason Creek to monitor biota (including macro invertebrates)
and physical conditions. Pre-construction data will be collected.
b. The permittee shall establish a minimum of one permanent monitoring station in Banks
Channel a minimum of 50 feet away from each side of the sediment basin to monitor biota
(including macro invertebrates) and water quality. Pre-construction data will be collected.
c. The permittee shall monitor a minimum of twelve transects (between mean high tide and
mean low tide along the beach disposal site) on Figure 8 Island for macro invertebrates and bird
usage. Pre-construction data will be collected.
7. The permittee shall cooperate with the North Carolina Division of Marine Fisheries
(NCDMF) oyster seeding program in the project area by providing dockage and loading facilities
for barges used in the NCDMF oyster seeding program. NCDMF will monitor this program to
insure that areas seeded are suitable for oyster seeding and seed about 10,000 bushels of oysters
annually until the first maintenance event. The Corps will evaluate this mitigation measure for
its effectiveness in offsetting fisheries impacts as part of their review of the first maintenance
event.
8_ Dredging will be timed so that turbidities will be minimized to the maximum extent
practicable. (timed to avoid or halted just before and during storms and other periods of
S potential high erosion, currents, and waves)
9. The placement of dredged material in the existing inlet and along the beach will be timed so
that turbidities will be minimized to the maximum extent practicable. (timed to avoid or halted
just before and during storms and other periods of potential high erosion, currents, and
waves)
10. The permittee shall not impact mature marsh on the north side of Mason Creek.
11. All sandbags and fragments will be removed from Shell Island Resort area and disposed of
properly in accordance with NCDCM requirements.
12. This Corps permit does not authorize the permittee to take an endangered species, in
particular the piping plover (Charadrius melodus), the seabeach amaranth (Amaranthus
pumulis), the West Indian manatee (Trichechus manatus) the green sea turtle (Chelonia mydas),
and the loggerhead sea turtle (Caretta caretta). In order to legally take a listed species, you must
have separate authorization under the Endangered Species Act (ESA) (e.g., an ESA section 10
permit or a Biological Opinion (BO) under ESA section 7, with "incidental take" provisions with
which you must comply). The enclosed US Fish and Wildlife Service (Service) BO, dated
March 14, 2001, and BO amendment, dated September 5, 2001, contain mandatory terms and
conditions to implement the reasonable and prudent measures that are associated with "incidental
take" that is also specified in the BO. Your authorization under this Corps permit is conditional
upon your compliance with all of the mandatory terms and conditions associated with incidental
take of the attached BO, which terms and conditions are incorporated by reference in this permit.
2

,.
• ~
Failure to comply with the terms and conditions associated with incidental take of the BO,
where a take of the listed species occurs, would constitute an unauthorized take, and it would
also constitute noncompliance with your Corps permit. However, the Service is the appropriate
authority to determine compliance with the terms and conditions of its BO, and with the ESA.
For further clarification on this point, you should contact the Service. Should the Service
determine that the conditions of the BO have been violated, normally the Service will enforce the
violation of the ESA, or refer the matter to the Department of Justice.
13. The permittee shall undertake the project with extreme care. If, during construction or any
maintenance event, submerged materials are encountered, the permittee shall move work to
another area and contact the Corps and the North Carolina Department of Cultural Resources
(NCDCR), Underwater Archaeology Unit immediately at [phone] to investigate and
determine the proper course of action. The Corps will advise the permittee when
construction/maintenance may resume in the area of the archaeological investigation.
14. Shipwreck site 0002MAI, the remains of a wooden sailing ship, is located approximately 200
yards north of the Shell Island resort. Prior to beginning work on the project, the permittee shall
provide NCDCR with detailed plans for closure of the existing inlet. Upon receipt, NCDCR
staff members will attempt to pinpoint the present location and nature of site 0002MAI to assist
engineers of the proposed project in avoiding damage to the shipwreck.
• Address: NC Department of Cultural Resources
Division of Archives and History
109 East Jones Street
Raleigh, North Carolina 27601-2807
15. The permittee shall implement compensatory wetland mitigation at the same time or prior to
beginning project construction as proposed in the applicant's ntigation plan, Attachment 5 of
the Corps' EA. Any deviation from the wetland mitigation plan will be coordinated with the
Corps and must receive specific approval before being implemented.
16. Within 30 days of permit issuance, the pernuttee shall develop and implement, in
consultation with the North Carolina Department of Environment and Natural Resources, the
North Carolina Wildlife Resources Commission, the U.S. Fish and Wildlife Service, the
National Marine Fisheries Service, and the Audubon Society, subject to approval by the Corps, a
shorebird and waterbird management plan and biological monitoring plan with regard to issues
related to nesting, roosting, and foraging habitat. In the event the Corps determines that the
results of those studies indicate that remedial action is necessary, the permittee shall implement
any such remedial action directed by the Corps.
17. The Wilmington District routinely surveys the AIWW, including the portion at its
intersection with Mason Creek, in order to assess dredging needs for maintenance of navigability
of the AIWW. The permittee shall notify the Wilmington District Regulatory Division two
weeks prior to the commencement of construction, to allow the District to perform a survey of
the area of the AIWW that will be potentially affected by the proposed project.
3

• ~
If the District Engineer, in his sole discretion, determines that shoaling has occurred within the
AIWW on Tangent 12, Section 3 between monuments T12-8 and T12-41, at any time during the
life of the project and that such section should be dredged in order to maintain safe and efficient
navigation on the AIWW, he will so notify the permittee in writing. The notification will specify
the area of the AIWW that must be dredged, the depth to which it must be dredged, and the time
frame within which dredging must begin (a minimum of 90 days will be allowed). The permittee
shall cause the area of the AIWW specified by the District Engineer to be dredged in a manner
and within the time frame specified in the notice.
18. Borings of the proposed work area did not reveal the presence of any unsuitable (non-beach
compatible) material. The equipment and techniques to be used by the contractors must allow
for the inspection of all materials. All material dredged from Mason Creek, and any additional
material that is determined to be unsuitable beach material will be pumped to the diked settling
area for removal of unsuitable material. The applicant shall test all dredged material for beach
compatibility, and provide the tests to the Corps for confirmation before placing material on the
beach. Material deemed to be non-beach compatible will not be placed on the beach or in the
Corps' dredged material islands, but will be removed from the project area and placed in a high
ground site that has received specific approval from the Corps, NCDCM, and the North Carolina
Division of Land Quality.
19. The permittee shall maintain the dike walls constructed around holding areas for dredged
material to eliminate the release or escape of dredged material. Failure of a dike wall will result
in the immediate cessation of pumping into the specific diked area. Repair work on dike walls
will not begin until specific permission is requested and received from the Corps and NCDCM
with the exception of work necessary to provide emergency repair of dike wall failures.
20. The permittee shall comply with the attached US Coast Guard regulations.
21. The permittee understands and agrees that, if future operations by the United States require the
removal, relocation, or other alteration, of the structure or work herein authorized, or if, in the
opinion of the Secretary of the Army or his authorized representative, said structure or work shall
cause unreasonable obstruction to the free navigation of the navigable waters, the permittee will be
required, upon due notice from the Corps of Engineers, to remove, relocate, or alter the structural
work or obstructions caused thereby, without expense to the United States. No claim shall be
made against the United States on account of any such removal or alteration.

4

In addition, the permittee shall notify
NOAA/NATIONAL OCEAN SERVICE
Chief Source Data Unit
Attention: Sharon Tear N CS261
1315 E West HWY RM 7316
Silver Spring, MD 20910-3282
at least two weeks prior to beginning work and upon completion of work.
22. The project will only be maintained for inlet stabilization purposes per the Inlet Management
Plan (Section 1.4 of the Corps EA).
23. The applicant will comply with all conditions of the 401 Water Quality Certification No.
3274, issued April 30, 2001 and modified on June 27, 2001 (Attachment b of the Corps' EA).
24. The applicant will comply with all conditions of the State Permit issued by NCDCM.
25. The permittee shall utilize bathymetric surveys and aerial photography required in
Condition 5 to determine the loss of intertidal areas as a result of project construction and
maintenance. Preproject surveys and post-construction and -maintenance surveys will be
• provided to the Corps with all impacted intertidal areas tabulated. Annual monitoring reports,
provided to the Corps, North Carolina Department of Environment and Natural Resources, the
North Carolina Wildlife Resources Commission, the U.S. Fish and Wildlife Service, and the
National Marine Fisheries Service, will provide bathymetric surveys and aerial photography
indicating the amount of intertidal areas in the project area. The permittee shall address any
difference between preproject intertidal areas and the amount of intertidal areas formed post-
construction and propose appropriate remediation in the third annual monitoring report and
update the analyses in each annual report thereafter.
w
5

•
N.C. Department of Environment
and Natural Resources
Permit #151-01

~A,
ENOn~EI~ 'k 8t~1tEY~

•
]?ermit Class ' ' . .
Perrrtit Number
NEW
151-t31
STATIfr Ulu' NU32TH CAROIL,1'NA
Dtpartmrn# of Environtncnt and Natural Resources
an d
Coastal l~source8 Commission
~~~~~
for
~ Ni~jor Development in an Arse of ~nvironmcnt$3 Concern
pursuant to NCGS ! 13A- I I S
X )?xoavatiz,n andlor filling pursuant #o NCGS 113-229
•
Issued to N'ew Hanover Couaty, 414 ChQStttl~t Street, W~Isaington, NC 284Q1
Authorizing dcvelflpment in Neyv Hsrwver County at Mason Inlet, adi. At]a.n#ic Ocean Mason
Craelc and AIWW ~ ~ , as requested in the pcrmittco'S application dated 8125/93, inclndint; .~
attached the workplan drtYtyirl~B {3~), as referenced izt Canditifln No 1 of this permit
Thin permit, issued on ~ Nove~nr 28, X00] , is subject io t:ampliance wi#h the application (wl~cre Cnnsisiertt
w{lh the permit}, all apolicablc rCgtllBt]nA.6, species ct~rditicna and notes set Earth below, Any violator. >3f these terns may
lie subjeLt #u find, im}~rieonmant flr civil d~#ion; or mny cause the paznit to be null and void,
1} The authorized project shall be ciflne in compiiancc with the attat;<hcd wslrkplan drawings, except as
maclifietl herein=
Sheets 1-S, all- dated 8I25I99
Sheets 6, 7 dated 2127/01 and revised 3.1/21/01
Sheet 8 dated $f24I99 and revised 11/21!01
Sheet 9 dated 2127101 and revised I I121 ~O1
Sheets 10•I7 aII dated 8!20/99 and revised 11/2l/01
S)leat I$-20 ell dated $120101 and revised 11/21>O1
6hpat 2l dated and revised 11/21/01
Sheen 22-Z4, sll dated 8126/99
See#s2S-28, alI Baled 8126194 and revised 11121103
Sheets 2932, alt dated 8/26/99
(See aktat:hed sbeet8 for Addltdortal Coudlt3ona}
~cttnit action atav ho annealed by rhr nrn,,;rraP ~ e;Rti,..~ h„+i,. ~,.,t,,,.;... ..r .c... n...._,..,. ~ -
•
otlser qualified persona within twt:nty f24} Boys of the isruing
dote. An appeal raqulras sesolutian prior to work irfitiatiosl nr
coat{nurinco ne zhc coo may 60.
T1ii8 puz~it rcluBt ke YGGt;B81~1C O$1-9i2L to Dtspartmant
personnel When tl~e pmjoet is lri9pectpd for compliance.
Any ma{ntenance wnr9c or project modil'icatioa not covered
ktercundcr;oquiroA fttriher Div-it;lan approval.
ill work mus[ cease when the Pcrrnir t;xplres on
December 3~, 2004
In f6eui-u8 this pa~rait, the Fitat4 of Atorrh Carolina egress
thin your proJcot !e cogainiont with the North C~rolino Coastal
Management Pr4gratn,
Chttlrntart of the Coastal'2caflnrces Co3nmission.
f'j/
( D a D.1vlvffitk, Director
Division of Coastal Mana~,t:mrnt
7'4tfs parrnit and its cotaditlox~ nee IZnra6y :tccuptva_
tgnature o Pciznittee

NeW I~auDVe~~onaty Perv~lt ~#15X~Q1
• Page Z of 7
~DD)fTrONAit CDNDITIt1N8
I'~lew Inlet Pxcavstinn
2) Prior to and witbiz~ twa weeks of the excavation of i~igurc 8 Island, the tarnporary plactznent of
sppraximatsly 600 linear feet of sheet pile i~ authori~ad on #.he btachi~ont st the month of t23e proposed
new inlet par~lIel to and just landward of MHW, as depicted on attached wvrkplan drawings 6 and 7,
both dated 3/2~lO1. This s>:teet pile would allow subsequent oxcavation of the new inlet channel while
preventing an inadvet#erlt breach during storm and spring tide events.
3) Removal of the shut pile sixueture at the mouth. of Y}~e now inlet must be initiated dt;ring the first titiai
cycle following completion of tko dredging of the new inlet. '
4} The depth of exc~vatian flf rllc new inlet ~h~ll na exceed -l b feet NCiVD,
Sediment basin
•
3} 13a5ct1 upon commitments made by The pcnnittte, the east-west dimension of the ,sodimt~t basin is
r$dtrced by 100 fleet. The limits of the revised sadiraer;t basin excavatior shall not exceed those
indicated ou attached workplan drawings b, 7, and 9, ail dac~d 3I27/al,
5) Tie dapttt cif excavation of tlic sediment basin, Including the Irottion of the Mason Lr~k channel
nu~ning through the sedir*lEnt basip shall not exceed -32 feet NGVD.
Masan Creek Is~~cyavation
•
~ If sedimentation barriers fail to prevent sand move +serct i~bo the Atlantic Intracoastal Waterway
{AIWW}, IVtASOn Crock shall be cl~dged rduring Lida] conditions tbai prevent tida3 #lows into the AIWI~.
8) The dredging of I~son Creek is limittd to a bottom width of 80 feet and a width of 144 feet at the 0.0
(~iGVD) elevation. .
9) T}ie depth of exoavstifln of the Mason Crcck shall not exceed -l Q feet NQV'D, except that the pgrtion of
Iviason Creek that runs through the sediment basin, shall not excn8d -12 feet NGVIa,
14) In order to reduoe sediTpentarion from enterins the A1WVJ during project cwzstrucci4n, a +/- 1,op0 foot
lopg undredged plug will remain in place neat the AIWW, seed a temporary sheet pile stnzcturc ar ether
approved sodimaitation barrier installed near the ocean-side of the plug. The plug and temporary sheet
pile or other approved sedimentation bazxier shall be removed immediately follflwing completion of the
dredging of bnih the sodimentaciazs basin atad zhc new in1Gt.
11) The final dimensions oY the sheet pile strnettue shall be the absolute .minimum necessary to ensure its
funckionaliry, The final dimensions, design and location shall be approved by the Division o#~ Coastal
I~Sanagemszrt,prior to placement of the structure.

i ~
New Hauovar Couhty Permit #131-~{li
• Page 3 of 7
ADDITI©N1-.L Cnx~rrroNs
12) Material dredged £ram Mason Creek will be dewatered and stockpiled in a temporary 8-9 acre diked
high ground area on the not-dtern side of the existing istlct. Prior to dredging, material from within the
stockpile area shall ba bulldozed to create the 15-foot high dike and to deepen the site, allowing the
deposition of more dredged material, Additional temporary diked stockpiles may be created and located
ott the south aide pf Masou Inlet, on high ground at the north cud of the Shell Island Resort, on North
1/uraina Avenue, or on a portion of the natural beach in front of the Resort.
Closing of >~xlstlug_Inlet
•
13) Near the completion of the initial phase of Mason Creek dredging, the temporary placcrrtent of
approximately 6130 to '700 linear feet of sheet pile or other approved temporary tcmparary shoring or
siltation barriers across the existing inlet ie authorised. The sheet pile or approved tetnpflrary
sharing/ailtatinn bamer will begin on the ocean-side of she stockpiled dredge material site and extend in
a southerly direction to tiB into the oceanward face of the sandbag revetment at the Shah Island resort.
1 ~} Prior to the initiation of any rc~nstruc~ion authorized by this permit, a detailed ~vorkplszi drawing
depicting the location of this t~nporasy sheet pile structure or approved temporary sJ~ariugJsiltation
barrier across the mount of the existing inlet shall be stlbmittcd to the Division of Coast$1 Management
for approval.
l5) Removal of the sheet pile structure or approved temporary shoringJailtation Farrier at the mouth of
existing inlet must be initiated daring the firer tidal cycle following the complttc closure of the existing
inlet Tho shtct pile Sts1.iCCuro or approved temporary shoring/si]tation barrier shall lac allowed to remain
in place for a maximum of 30 days.
NOTE: The Division of Coastal Management will entertain a regtaost by the permittee to modify #his
perutit #a allow the sheet pilt or approved temporary shoringlailtatiou bamer to remain in place
for slightlymore than 30 days only if work has begun and is ongoix-g ort the closure of rho
existing inlet, end reasonable assurances are provided that the authorized work wlll be completed
in se short a time a& possible.
Beach DepQSit)ott and lVourlsbrttent
•
l6) Prior to the initiation of any beach naurisbxrtent activity above mean high water (MHW) witltin the
limits of the permittee's authorized beach deposition area, casements or othcx legal authorities to
urtdertakc, rho authorized activity on cash property must be obtained.
I7) Prior to tba initiation of azty beach nourishment activity, rho existing mean high water line must be
dalineataQ and the line approved by reprasentativas from the Division of Coastal Management. The
approved lines must be surveyed in and the survey submitted to pivision, If nourishment activity is not
initiated within sixty (60} days or there is s major shoreline change prior to rho commencement of beach
nourishment, a new survey must be conducted.

lYe~VV Hanover` Co>rnty Pormli X151-01
• Page 4 t~f 7
AD~AITIONAL CON~1[Tl;ONS
•
18) In order to protect threatened and endangered species and to minimize adverse impacts to affshorc,
neezsltoCe, intertidal and 6e~ch raeources no beach nourishmont activity may occur from April 1 to
~lovemher l5 of any year withQUt prior approval from the Narth Carolina Division of Coaxial
Management izt consultation with the NC 3xvisio^ of Iviarinc Fishcrias and the I~iC ~ildlifa Rosflurcas
Commis&iort.
l9) Irt order to ensure that advcrso impacts do not occur to Wasting sea ttutlcs as a result of the {ormation of a
scarp ~or frorn aubstrntc cornpactian, the permittee s1~a11 ursdet-t31ce remedial e-ecian (ire, ripping or tilling
of the nourished boach, ]cvelitlg cut the scarp) at the request of either the Division of Coastal
Management, tho t~.S. Army Corps of L'ngineers or the US Fish artd Vl~ildlifa Service.
NOTE: The pcrmittoa is advised that there maybe additional timing res#rictions placed on the authorized
pro,~aat by the ~.5. A7mY Carps of Engineers as part of the Federal permitting proaaea. Nothing
in this State permit should be construed as overriding ox aupercading any such Federal permit
requirement.
20) Only beach quality sand shall be used fflr bcac3a nousiahrnent andJor inlet closure purposes.
Furthermore, sand of similar grain size to the existing beach will 6e used to reQ~ca any changes in
physical characteristics of the beech. Any non-beach quality material must be dispo9ed of in an
approved ngland disposal area, ~-
21) ;>hauld the dredging or excavation operations encounter any non-beach compatible sand, the dredge
alzall immediately cease operatifln and move to an apprnvec3 area where suitable material does exist,
22) Iri order to prevent lGalcago, dredge pipes shall be routinely inspected. If leakage is found and repairs
1 cannot be made immadia~ly, pumping of material shall stop unri! such leaks arc fixed.
23} During and after canstrnction activities, a uniform, gradual beach slope will be maintained so as oat to
endanger rho public txr interfere with the public's use of zhe bench.
anon ..
24) In accordaztce with comrnitmcnts made by the pormittee, the following mitigative measures shall be
enacted, Subject t~ any additional condiiions contained herein;
a} The permitieo shall allow nQ devalapmcnt within its newly cra$t$d 1,440 foot inlet corridor.
Additionally, tlzo pertnittee sha11 prcvant devalapment of rho "H~taff properiy" by utilizing its 30-
yagz~ nptioi~ to purchase a aonstntctian easement otl the Hutaff property. A management plan for
those areas, as vve11 ae any aroa within cha project location fallizig under State ownership, shell be
developed in consultation with rho U.S, Fish and 'UVildlife Service, tba U.S. Army Corps of
Rngitteera, tht N.C. Wildlife Resources Commission, and the N.C. Division of Coastal Managetncnt.
This management plan must be finalized within 6 months of the issuance of this permit,
•
b) The parmitcec shall continue to investigate ~o purchase of all remaining tracts of the Masonbam
Island complex that are Currently in private ownership.

• Ne~v Iianover County permit #ISl-Q1
Page 5 of 7
ADDiT'XON~1I. CONDITIONS
c) Urditzanens shall be put into place that control and manage vehicular uses of the undeveloped area
north afthe Town of Carolina Haach.
d) In accordance with the December 2000 mitigation plan prepared far the pragosed pxaject, the
permittee shall restore tho majority of the 10.7 acrd Corps of Engineers Confined Disposal Facility
~CDP} located is close proximity to ills project site. Tlie mitigation site habitat acrtagee include:
- Intcstidal Marsh 5.2 acres
- High Marsh 2.1 acres
- Sub-T~dal CTeelcs l ,4 AGres
- 1~3are Sand A,toB Z.0 acres
- Preservation of adjacent
wetlands 19.0 acres
•
The beach-compati6lB material to 1}e removed from, the CDF may be placed on the beachfront,
provided that all conditions of this permit dealing with beach ncttrls}lment are strictly adhered to.
A13 morGitoriztg reports associated with this mitigation effm# shall be provided to the Division of
Coastal lvianagctnent.
e} The permittce shall utilize bathymetric surveys and aerial photography regttixed to determine the loss
pf intortidal areas as a rebult of project construction and maintananco. Pre-project surveys and pest-
cansttuction and uiaintenanee surveys wi31 be provided to the Division of Coastal Managctncnt with
ail impaoted intertidal areas tabulated Annual monitoring reports will provide bathymctric surveys
and aerial photography indicating the amount of intertidal arcs in the pxaject axes, The permittec
shall address any dificronco between. pre-project intertidal areas and the amount of intertidal areas
fotmecl following project construction. Proposed remediation far any net loss of intertidal area must
be proposed in rbe third annual crionitoiing rzpon.
25) In order to protect sea turtle nzsting habitat, no work may be carried out on the beach between Mayl and
Novombet 1 S o#' $ny yaar without first obtaining autharizatioq from the Division of Coastal
Managamant, in coardinetion with the N.C. rildlife Resources Commission and U,S, Fish and Wildlife
Service,
2b) Iti order to en~urc protection of all threatened and endangered species, all conditions of the U.S. Army
Corps of 8n$inc~s Irtdiyitiual Pem~.it relating to suola species protection shall be fully implemented.
27) Any additional mitig~tiva tnoasures contained in ilae National Enviranmantal Policy Act Brivirotuncntal
Assessment document prepared for the proposed project shall he implemented unless specifically altered
horoin.
•

• NEw Hanover county Ptzrmit #IS1-lll
Page b of 7
AiyDI'PIOI~tAI. C(aNDTTIOIV'S
Archaeolagiesl Resource Prateetlon
28) The N.C. Division of Archives and History has identified one shipwreck in tbt project area (#OIMAI)
.
Extreme care must be oxoreisod when working in proximity to this historic and cultural resources site
,
The applicant should contact the Division of Archives and History to discuss prntecrion measures for the
shipwreck. Ftrrtlrsrnlare, ahvuld arty unknown shipwrecks be enraUntered during the course of the
project, all work in that area immediately cease, and the applicant immediately contact both the Dtvi9ion
of Coastal Management and the 1`T.S. Army Corps of Engineers so that the appraprfate coordination ma
y
begin.
" Future Maintenance Excavation Events
29) l/ach Future request for maintenance excavation and subsequent beaohfrant disposal will require a
madiPica[iou of this Coastei Arca Management Act/State D
ed
r
ge a.uQ Fill Lew permit, l~l.irthetmore,
should the relocated inlet migrate outside of the inlet comdor area indicated on tbo workplan drawin
s
g
submitted with the permit application, a major modifloatinn of the permit will be xequired. The
i
d
i
• peim
ttea
s a
vised that the factors t4 be considered in reaching a decision on any such modification
request will inoludc the rtii$ration of the new inlet, amount of material to be excavated, season of the
proposed work, information collected during tlae various monitoring efforts foIIowing initial project
comptetiou, success of th8 proposed wetland mitigation $raa, eansiruction rrtethodolagy, etc.
NOTES; The permittee is advised that futtue maintenance request should be driven sorely by the
movement or shoaling in of the new inlet, not by the need for sand far beach nQUrishment
Furposcs.
General
30} Ail conditions and stipulations of 40J Warec Quality Certification No_ 3274 (Permit No. 000008}
which
,
waa issued an d/3QJ91 and revised. on 6127101, must be strictly adhered ta, ,Any violation of the Water
Qualiry Certification would also be considered a violation of the CAMAI~ruisa and $i11 permit.
31) A1o in-water work Will be petmitCed between April 1 arrd November 15 of any year without the prior
approval of iho Division of Coastal MatlagamQnt, in consultation with the Division of Marine Fisheries.
32) The petmittca is advised that the State of Nonh Carolina claims title to any currently submerged lands
raised above tb$ mean high water lies as a result of this project. The public will have rights of use such
newly created public beacb~
i
33) All monitoring reports submitted io the U.S. Army Corps of Friginarus and/or the N.C. Division of
Water Quality must also be provided to the Division of Coastal Management.
NOTE: This permit does not eliminate iho need Yo obtain any additional permits, $pprovals or
authorisations that tray be required.

•
•

•
N.C. Division of Water Quali
401 Certification
WQC Project #000008
•
E~
• ~ ,~

•
`~ ^~~r-.
..
Michael F. Easley
Governor -
Sherri Evans-Stanton, Acting Secretary
Department of Environment and Natural Resources
Kerr T. Stevens
Division of Water Quality
June 27, 2D01
~0 ( C~~r i F~e~-T~ o~
Mr. Greg Thompson
New Hanover County
414 Chestnut Street
Wilmington, NC 28401
Dear Mr. Thompson:
Re: Revised Certification Pursuant to Section 401 of the Federal Clean Water Act,
Proposed Mason's Inlet relocation and associated dredging
WQC Project #000008
New Hanover County
Attached hereto is a copy of the revised Certification No.3274 issued to New Hanover Gounty
dated June 27, 2000. This Certification replaces one issued to you on April 30, 2001.
If we can be of further assistance, do not hesitate to contact us.
•
~}
Attachments

'rtc ely,,
err T teven
cc: Corps of Engineers Wilmington Field Office
Wilmington DWQ Regional Office
Doug Huggett, Division of Coastal Management
File Copy
Central Files
Karyn Erickson Applied Technology & Management of N.C., Inc. 201 Front Street, Ste 201
Wilmington, NC 28402
Steve Morrison; Land Management Group, Post Office Box 2522, Wilmington; NC 28402

~~
fit'
~~~..E71=i'~iz
Division of Water Quality
~n~e+hnAc/drl'I Ilnit• fQ~A1733-1786
1621 Mail Service Center Raleigh, NC 27699-1621

r4 ~'' ~, ;: Michael F. Easley
~ j .. ?„~
Governor
~,:'~ "v
'~ ~~'`y'~~~; i Sherri Evans-Stanton, Actin Secrets
C A S '"~a. ~. r 9 ry
• ~ v ~~ -.:~~a.: ~ Department of Environment and Natural Resources
....
%-~ " Kerr T. Stevens
:,;
,~ ~.
Division of Water Quality
NORTH CAROLINA 401 WATER QUALITY CERTIFICATION
THIS CERTIF1CATlON is issued in conformity with the requirements of Section 401 Public
Laws 92-50D and 95-217 of the United States and subject to the North Carolina Division of
Water Quality (DWQ) Regulations in 15 NCAC 2H, Section .0500. It is issued to New Hanover
County resulting in 1.9 acres of wetland impact 49 acres of open water dredging and 41 acres of
open water fill in New Hanover County pursuant to an application filed on the 4 day of June,
2000 with the final EA/FONSI and letter dated January 8, 2001 from Applied Technology and
Management of N.C., Inc. to relocate Mason's Inlet.
The application provides adequate assurance that the discharge of fill material into the
waters of the Atlantic Ocean (Mason's Inlet) and Mason's Creek in conjunction with the
proposed development will not result in a violation of applicable Water Quality Standards and
discharge guidelines. Therefore, the State of North Carolina certifies that this activity will not
violate the applicable portions of Sections 301, 302, 303, 306, 307 of PL 92-500 and PL 95-217
if conducted in accordance with the application and conditions hereinafter set forth.
This approval is only valid for the purpose and design that you submitted in your
application, as described in the Public Notice. If you change your project, you must notify us and
send us a new application for a new certification. If the property is sold, the new owner must be
given a copy of the Certification and approval letter and is thereby responsible for complying with
all conditions. if total wetland fills for this project (now or in the future) exceed one acre or #otal
perennial stream impact exceeds 150 feet, compensatory mitigation may be required as
• described in 15A NCAC 2H .0506 (h) (6) and (7). For this approval to be valid, you must follow
the conditions listed below. 1n addition, you should get any other federal, state or local permits
before you o ahead with your project including (but not limited toj Sediment and Erosion
control, Coa~al Stormwater, Non-discharge and Water Supply watershed regulations.
Condition(s) of Certification:
Appropriate sediment and erosion control practices which equal or exceed those outlined in the
most recent version of two manuals, either the "North Carolina Sediment and Erosion Control
Planning and Design Manual" or the "North Carolina Surface Mining Manual" (available from the
Division of Land Resources in the DEHNR Regional or Central Officesl. The control practices
shall be utilized to prevent exceedances of the appropriate #urbidity water quality standard (50
NTUs in a!I fresh water streams and rivers not designated as trout waters; 25 NTUs in all lakes
and reservoirs, and all saltwater classes; and 10 NTUs in trout waters);
2. All sediment and erosion control measures placed in wetlands or waters shall be removed and
the natural grade restored after the Division of Land Resources has released the project;
3. Measures shall be taken to prevent live or fresh concrete from coming into contact with
waters of the state until the concrete has hardened;
4. Should waste or borrow sites be {ocated in wetlands or other waters, compensatory mitigation
will be required since it is a direct impact from road construction activities;
5. Compensatory mitigation shall be done as outlined in the final EA/FONSI with the following
additions:
• a) Biological monitoring shall be for three (3) transects rather than the two proposed,
b) Biological monitoring shall be for five years. Three copies of annual reports sha(I be sent to
DWQ for review and comment and recommended modifications shall be implemented to
ensure success,
~'4~ .
--_- ----
I~t;DE
Division of Water Quality 1621 Mail Service Center Raleigh, NC 27699-1621
ina,a~.....l~L1M I InB• /O~OI 73317RR

. ~;G ;-1;,,~ Michael F. Easley -
- ~ ~ `T~ ~:>.'~' ~",- Governor
:,~..,ri<,, R ~ ~~f f Sherri Evans-Stanton, Acting Secretary
-_ s .i a ~ =~:;_ _, Department of Environment and Natural Resources
- Kerr T. Stevens
' ~ - Division of Water Quality
6. Applicant shall submit within four mouths for written DWQ approval a plan to monitor marshes
- adjacent to Mason's Creek. This plan shall included measure, to compare the predicted water
velocities to help understand and compensate for any observed impacts to marshes. If this
monitoring reveals an additional loss of wetlands in this area, then additional compensatory
wetland mitigation will be required.
7. All other conditions of General Certification #3274 are hereby incorporated by reference.
Violations of any condition herein set forth shall result in revocation of this Certification and
may result in criminal and/or civil penalties. This Certification shall become null and void unless
the above conditions are made conditions of the Federal 404 and/or coastal Area Management
Act Permit. This Certifiication shall expire upon expiration of the 404 or CAMA permit.
1f this Certification is unacceptable to you have the right to an adjudicatory hearing upon
written request within sixty (60) days following receipt of this Certification. This request must be
in the form of a written petition conforming to Chapter 1508 of the North Carolina General
Statutes and filed with the Office of Administrative Hearings, P.O. Box 27447, Raleigh, N.C.
27611-7447. 1f modifications are made to an original Certification, you have the right to an
adjudicatory hearing on the modifications upon written request within sixty (60) days following
receipt of the Certification. Unless such demands are made, this Certification shall be final and
binding.
• This the 27T" day of June, 2001
DIVISION OF WATER QUALITY
~~
- ~- e .. tevens
•
.~
~t~:Dl_;
Division of Water Quality 1621 Mail Service Center Raleigh, NC 27699-1621

•
f ~~ ~
%, ~ ~ ~sy
~~, '- t.
DWQ Project No.: County:
Annliranfi•
_ Michael F. Easley
'' Governor
Sherri Evans-Stanton, Acting Secretary
J= Department of Environment-ond Natural Resources
Kerr T. Stevens
Division of Water Quality
. .r r-------
Date of Issuance of 401 Water Quality Certification:
Certificate of Completion
Upon completion of all work approved within the 401 Water Quality Certification or
applicable Buffer Rules, and any subsequent modifications, the applicant is required to
return this certificate to the 4011V11etlands Unit, North Carolina Division of Water Quality,
'1621 Mai! Service Center, Raleigh, NC, 276 9 9-1 6 21.This form may be returned to DWQ by
the applicant, the applicant's authorized agent, orthe project engineer.lt is not necessary to
send certificates from all of these.
Applicant's Certification
1, _ - ~ .- ,hereby state that, to the best of my abilities,
due care and diligenceiviras used in the observation of the construction such that the
construction was observed to be built within substantial compliance and intent of the 401
Water Quality Certification and Buffer Rules, the approved plans and specifications, and
other supporting materials.
Signature: - Date:
Agent's Certification
1, ~ -~ - - ,hereby state that, to the best of my abilities,
due care and diligence`viias used in:the observation of the construction such that the
construction was observed to be built within substantial compliance and intent of the 401 .
Water Quality Certificatio.n~and Buffer Rules, the approved plans and specifications, and
other supporting materials.
Signature: Date:
Yr'a5 Ci Sly^i~^cu j'ti Ce:t:r~"t'. D: vfeS.S:.^+::?.~
ii iiiiS pi vjc~ ~
1, ~~ ~ , as a duly registered Professional
(i.e,, Engineer, Landscape Architect; Surveyor, ect.) in the State of North Carolina, having
been authorized to observe (periodically, weekly, full time) the construction of the project,
for the Permittee herebystate that, to the best of my abilities, due care and diligence was
used in the observation'of the construction such that the construction was observed to be
built within substantial compliance and intent of the 401 Water Quality Certification and
Buffer Rules, the approved plans and specifications, and other supporting materials.
Signature Registration No. ~ ~ ~ - Date ~ -

Division of Water Quality
1621 Mal Service Center Raleigh, NC 27699-1621

•
SHPO Letter
•
~~
*~

•
-~>.
dJ ~~ -'~2C
.,T~~ , ~
~`~~. _
North Carolina Department of Cultural Resources
Jamcs $_ Hvnt Jr., Governor
$etty Ray McCzin, Secretary
October 1 3, 1997
6teve Marrison
Environmental Consultant
Land Management Group, Inc.
P.O. Box 2522
Wilmington, NC 28402
Re: Request for information concerning the
preparation of an environmental assessment #or
the proposed dredging in and near Mason's Inlet,
New i-lanover County
•
Dear Mr. Morrison:
Division of Archives and History
Jeffrey J. Crow, Director
As requested, members of our Underwater Archaeology Unit reviewed the proposed
dredging ofi Mason's inlet, Mason's Inlet Creek, Banks Channel, and Lich Inlet
Creek and determined that the dredging constitutes a major bottom disturbance.
A review of historical records indicates that these channels were shallow and
seldom used. In addition, Mason's Inlet and Rich Inlet have been unstable and
prone to move north and south thus altering channel alignments. Recently,
signifiicant portions of Banks Channel and Rich Inlet Creek have been dredged_
Based on this information, the proposed dredging occurs in an area that holds a low
to moderate potential for containing submerged cultural remains. We, therefore,
recommend that no underwater archaeological investigation be conducted in
connection with the dredging portion of the project.
V1~e would like to notifiy you that this project should be undertaken with extreme
caution. if during construction submerged materials are encountered, work should
move to another area and our Underwater Archaeology Unit be contacted
immediately (910/458-9042}. A staff member will be sent to make an assessment
ofi the remains and determine the proper course of action.
The above comments are made pursuant to Section 106 of the National Historic
Preservation Act and the Advisory Council on Historic Preservation's Regulations
for Compliance with Section 106 codified at 36 CFR Part 800.
•

•
Thank you for your cooperation and consideration. if you have questions
concerning the above comment, please contact Renee Gledhill-;=arley, environmental
review coordinator, at 91 9/733-4763.
Sincerely,
~~~~_~ .
David Brook
Deputy State Historic Preservation Officer
DB:slw
cc: John Parker, Division of Coastal Management
Wayne Wright, Army Corps of engineers, Wilmington

s

•
Appendix C
Inlet Management Plan
•
~-~
~~„~~

Mason Inlet Management Plan

By:
Applied Technology 8~ Management of North Carolina, Inc.
Revised August 2000
•

•
Table of Contents
1.0 Introduction ......................................................................................................................1
1.1 Purpose and Authorization .....................................................................................1
1.2 Scope of the Mason Inlet Management Plan .........................................................2
1.3 General Description of Mason Inlet ........................................................................2
1.4 Interest Groups and Inlet Use ................................................................................3
1.5 History of Mason Inlet ...........................................................................................4
1.5.1 Inlet Migration Effects at North Wrightsville Beach
1.5.2 Recent Short-Term Efforts to Protect Properties at Wrightsville Beach
1.5.3 Figure 8 Island
2.0 Physical Processes .........................................................................................................8
2.1 Geologic Setting and Beach Processes ............................................................... ..8
2.2 Wind and Wave Climate ....................................................................................... ..9
1.5.4 Wind Climate
1.5.5 Wave Climate
1.5.6 Littoral Transport
2.3 Significant Storm Events (1996-2000) ................................................................. 12
2.4 Shoreline and Profile Changes ............................................................................ 13
2.4.1 Long-Term Changes
2.4.2 Recent Changes
2.5 Inlet Bathymetry and Shoaling ............................................................................. 16
2.6 Inlet Influence ....................................................................................................... 17
2.7 Sediment Budget .................................................................................................. 17
2.7.1 General
2.7.2 Regional Littoral Transport
2.7.3 Figure 8 Island
2.7.4 Wrightsville Beach and Shell Island
2.7.5 Mason Inlet Flood Shoal
2.7.6 Mason Inlet Ebb Shoal
2.7.7 Dredging Volumes
2.7.8 Beachfill Placement
2.7.9 Conceptual Sediment Budget
3.0 Mon itoring and Mitigation Plan .................................................................................... 24
3.1 Physical Monitoring Network ................................................................................ 24
3.1.1 Beach and Offshore Profiles
3.1.2 Inlet Area Bathymetry
3.1.3 Surficial Sand Sampling
3.1.4 Aerial Photography
3.1.5 Video Monitoring
3.2 Biological Monitoring Network ............................................................................... 26
3.2.1 Biological Monitoring Parameters
3.2.2 Biological Sampling and Analysis Methodology
3.2.3 Biological Monitoring Schedule
3.2.4 Biological Report Documentation

GNV/2000/Reports/99265-Final EA/InletMgmtPlan6/16/04 2

3.3 Managed Systems Approach for Maintenance and Remedial Actions ................. 29 .
3.3.1 Overview
3.3.2 Trigger 1 -Volumetric Losses
3.3.3 Trigger 2 -Sedimentation of Mason Inlet and Sedimentation Basin
3.3.4 Trigger 3 -Inlet Migration Threshold
3.4 Maintenance and Remedial Actions .....................................................................34
4.0 Mason Inlet Management Plan ....................................................................................35
4.1 Plan Elements ......................................................................................................35
4.2 Maintenance Element .......................................................................................... 36
4.2.1 Inlet Channel Maintenance and Dredging of the Sedimentation Basin
4.2.2 Maintenance of Beaches on Figure 8 Island and Wrightsville Beach
References
Appendix A -Tracks for Recent Tropical Storms
Appendix B -Beach Profile Comparisons
•

GNV/2000/Reports/99265-Final EA/InletMgmtPlan6/16/04 3

•
1.0 Introduction
1.1 Purpose and Authorization
On behalf of New Hanover County, Applied Technology and Management of North Carolina,
Inc. (ATM) has submitted a permit application to the North Carolina Division of Coastal
Management (NCDCM) and the U.S. Army Corps of Engineers (USCOE) for activities
associated with the proposed relocation of Mason Inlet. The purpose of this project is to
protect homes and upland property at the northern end of Wrightsville Beach from erosion
losses resulting from the continued southerly migration of Mason Inlet. Sand will be
excavated from Mason Creek, the sedimentation basin and the new inlet channel between
the Atlantic Intracostal Waterway (AIWW) and Figure 8 Island. The excavated material will
be transported via pipeline to infill the existing Mason Inlet and to restore the southern
oceanfront beaches of Figure 8 Island. An Environmental Assessment (EA) examining
existing environmental conditions, alternative corrective measures and projected project
impacts has been prepared for federal and state regulatory agencies for review.
In March 2000, New Hanover County authorized Applied Technology & Management of
North Carolina, Inc., to develop an Inlet Management Plan for Mason Inlet. The purpose
and goals of the Mason Inlet Management Plan (IMP) are described as follows:
1. review the existing and historical conditions at Mason Inlet and the adjacent beaches
-physical and morphological changes that have occurred;
2. develop a conceptual sediment budget associated with Mason Inlet;
3. outline a monitoring program to be implemented upon construction of the inlet
relocation, in order to document project performance;
4. identify "triggers" for remedial actions and, or maintenance work; and
5. recommend inlet management strategies to maintain the relocated inlet and to
address the mitigation of any adverse impacts that result to the inlet or adjacent
shorelines that are directly attributable to the inlet relocation.
•
GNV/2000/Reports/99265-Final EA/InletMgmtPlan6/16/04 ~

1.2 Scope of the Mason Inlet Management Plan
This Plan is divided into four sections. Following the introduction, a review of the involved
participants and inlet use is summarized. The history of Mason Inlet is also provided in
Section 1.0. Section 2.0 describes the physical processes that govern the behavior of
Mason Inlet and its adjacent coastal area of influence. Section 3.0 presents a monitoring
and mitigation plan for Mason Inlet. This plan will identify the measures to be taken to
document the changes over time following inlet relocation, and provide necessary data to
evaluate future actions in the inlet area. Section 4.0 provides the primary elements of the
Mason Inlet Management Plan, which are in essence, the corrective measures to be
implemented should adverse effects be observed during the monitoring phase.
It is noted that this document relies upon existing information and data for Mason Inlet and
the adjacent barrier islands, and is therefore not a complete, "stand alone" thesis on the
inlet. Numerous references are made to the detailed studies conducted during the
preparation of the Environmental Assessment, Mason Inlet Relocation Project (ATM and
LMG, 2000), and other regional related reports. Readers are directed to the reference
section for specific reports and details on the inlet and adjoining islands not provided herein. ,
1.3 General Description of Mason Inlet
Mason Inlet is located in New Hanover County, approximately 12.4 miles east of Wilmington.
Mason Inlet separates two barrier islands, Figure 8 Island to the north and Shell Island to
the south (Figure 1-1 ). The existing inlet corridor is approximately midway between two
larger tidal inlets, Rich Inlet to the north and Masonboro Inlet to the south. Masonboro Inlet
is a Federally Authorized navigation project that includes jetties and periodic maintenance
dredging.
The predicted mean tide range at Masonboro Inlet is 3.8 ft with a spring mean range of 4.8 ft
(US Dept. of Commerce, 1996). These ranges were verified by in-situ water level meters
installed during 1999 as part of the hydrodynamic modeling field data collection effort (ATM
and ASA, 1999). Tidal waters moving through Mason Inlet flow through Banks Channel,
Mason Creek, and the surrounding wetlands, which all route to the Atlantic Intracoastal
Waterway (AIWW).
s
GNV/2000/Reports/99265-Final EA/InletMgmtPlan6/16/04 2

The beaches adjacent to Mason Inlet are relatively low and flat. The littoral materials in the
vicinity are predominantly clean, fine to medium grained, and relatively uniform with mean
grain sizes ranging from 0.18 to 0.30 mm and small shell content (ATM and LMG, 2000).
Net littoral transport is directed to the south, although periodic reversals do occur.
Flora and fauna in the vicinity are typical of the North Carolina barrier islands, coastal inlets,
and saltwater marsh zones. More detailed discussions of the existing wildlife (benthic and
terrestrial) are found in Section 2.0 of the Mason Inlet Relocation Project's Environmental
Assessment Report (ATM and LMG, 2000).
1.4 Interest Groups and Inlet Use
Mason Inlet is not considered a navigable inlet. The local littoral processes and lack of
stabilizing structures have caused large-scale inlet migration and extensive shoaling, as a
result the inlet is considered dangerous for all but very shallow draft vessels at higher tide
stages. Considerable local knowledge and timing to coincide with proper tidal and wind
conditions is essential to safe passage. The historical location of the inlet, (prior to 1990s)
between developed portions of Shell Island and Figure 8 Island, has been of little
consequence to the adjacent populations. The area was utilized as a beach for walking,
fishing, surfing, and other outdoor recreational activities.
The 1990s saw acceleration of the inlet's southerly migration, which applied considerable
erosional stress on both the updrift and downdrift shorelines. This erosion initiated local
concern and beach nourishment actions in the 1980s on Figure 8 Island, (Cleary and
Hosier, 1990) followed by erosional impacts to the Shell Island-Wrightsville Beach shoreline
in the mid to late 1990s. In response to this erosion, the Shell Island Homeowners
Association constructed a temporary, sand filled geotextile structure to limit erosion of the
southward moving inlet in September 1997.
Subsequent requests for permits to extend the permit for the temporary structures, as well
as requests to construct more permanent training structures have been rejected and gained
national notoriety. A complete listing of the recent activities by both Figure 8 Island and
Shell Island Resort is given in Appendix K of the EA report (ATM and LMG, 2000).

GNV/2000/Reports/99265-Final EA/InletMgmtPlan6/16/04 3

In 1999, property owners at Wrightsville Beach and Figure 8 Island took the lead in
combining their interests and concerns and formed the Mason Inlet Preservation Group
(MIPG). This group is responsible for organizing the support of the County to sponsor this
Project and to develop funding for design, permitting and recent investigations, culminating
with the current proposal to relocate Mason Inlet to a more northerly position. Section 1.5
describes more details of the history of Mason Inlet.
1.5 History of Mason Inlet
The historical behavior of Mason Inlet has been documented by several authors, primarily in
compilations pertaining to inlets of North Carolina (Langfelder et. al., 1974; Priddy and
Carraway, 1978; Brooks, 1988; Cleary and Marden, 1999). Primary documentation has
been by comparison of periodic, horizontally controlled aerial photography.
Over the past 30 years, Mason Inlet has slowly migrated to the south. The migration of
Mason Inlet has accelerated over the past 12 years, following a classic southward trend due
to the net north-south littoral transport. As the result of this migration, the north shoreline at
Wrightsville Beach and the southern beaches at Figure 8 Island have experienced extensive
sand losses. A summary of the recent historical actions taken by New Hanover County, the
Shell Island Homeowners Association and the Figure 8 Beach Homeowners Association is
presented in the following sections.
1.5.1 Inlet Migration Effects at North Wrightsville Beach
Since 1985, inlet migration has resulted in the loss of more than 2,200 feet of shoreline at
the north end of Wrightsville Beach. As the result of sand deposits and inlet infilling at the
updrift (north) side of Mason Inlet, the inlet channel has been forced to move in a downdrift
direction causing strong tidal flows and the resulting sand losses at the north end of
Wrightsville Beach.
Following construction of the Inlet Relocation Project, the hydraulic forces attributed to the
increased tidal prism combined with inlet maintenance will act to stabilize the beaches of
Figure 8 Island by allowing the full development of an ebb tidal shoal, thus reducing beach
erosion at Figure 8 Island. The use of the Banks Channel as a borrow site for the
renourishment activities concurrent to the shoaling of Mason Creek caused an alteration in
the tidal vector behind Mason Inlet that has played the primary role in accelerating the
GNV/2000/Reports/99265-Final EA/InletMgmtPlan6/16/04 4

migration of Mason Inlet. The act of placing sand on Figure 8 Island is a secondary factor
contributing to the inlet's past migration.
With the relocation of Mason Inlet to arrest further migration south, the loss of the Shell
Island Resort; 38 single-family homes; and Wrightsville Dunes, Duneridge Resort, and
Cordgrass Bay condominiums will be prevented. These buildings will be protected to
eliminate further losses to the homeowners and a great economic loss to the County and
State of North Carolina. The planned project prevents further losses to the Shell Island
Resort building that is in immediate jeopardy of total loss as the design life of the geotextile
revetment protecting it has been exceeded. In addition, collapse of the Town of Wrightsville
Beach sand bags at the north end of Lumina Drive which occurred in 1999 will be avoided
and the bags removed; and the loss of the primary roadway, Lumina Drive, and utilities
(power, wastewater, and telephone/cable lines) will be prevented.
1.5.2 Recent Short-Term Efforts to Protect Properties at Wrightsville Beach
In September 1997, with the inlet channel within 100 feet of the Shell Island Resort, Shell
Island Homeowners Association stabilized Mason Inlet's south channel bank by constructing
a 410-foot geotextile revetment along the northeast perimeter of their building. Without the
construction of a temporary sand bag structure, Mason Inlet would have moved 600-700
feet south of its present location. The Coastal Resource Commission approved a variance
to the rules governing the placement location and size of sand bags in January 1997
allowing construction of a temporary, sand-filled geotextile revetment. This permit requires
removal of this structure by September 17, 2000. The north end of Wrightsville Beach is
protected by this structure, which was constructed of sand fill within 8 containers constructed
of a single-layer polyester container placed in a sloped configuration. Toe scour bags,
constructed in 1998, extend waterward along the lowest container to control bed scour and
the resulting subsidence and tearing of the large containers.
Over a period of 3 years, Mason Inlet's ebb channel deepened from -10 ft NGVD to -18 ft
NGVD (ATM, 1999 Geotextile Revetment 18-month Monitoring Report). Deepening of the
inlet channel has placed the downdrift properties at risk. The emergency sand bags
protecting the street end and island infrastructure were lost in the winter of 1998-99, which
required removal, retreat, and replacement in July 1999.
GNV/2000/Reports/99265-Final EA/InletMgmtPlan6/16/04 cJ

Following the 1999 hurricane season, Mason Inlet shoaled to a maximum depth of -8 ft
(NGVD) as described in the 24-Month Monitoring Study of Mason Inlet; however, since that
time, Mason Inlet has scoured to a depth of -18 ft (NGVD) as shown on the 34-Month
Monitoring Study of Mason Inlet.
As Mason Inlet continues to trap sand, which has resulted in an extensive interior shoal
feature containing in excess of 270,000 cubic yards of sand, the primary tidal channel
deepens. The flow is restricted within a limited cross-section and the channel bank has
been undermined, requiring replacement of sand bags and bag structures. Although the
migration of Mason Inlet had been halted and temporarily stabilized, the tidal prism has
decreased and erosive stresses plague the Town's north shore (refer to tidal prism
calculations, ATM, 1998).
Since 1997, the condition of this geotextile revetment has deteriorated. Wear from foot
traffic, tears, vandalism and UV radiation has significantly reduced the longevity and design
life of the geotextile fabric. Additional damage was caused by two strong northeasters and
three hurricanes [Hurricanes Bonnie (1998), Dennis (1999) and Floyd (1999)], requiring
costly repairs to the north shoreline properties.
1.5.3 Figure 8 Island
The Figure 8 Beach Homeowners Association has historically undertaken maintenance
dredging to provide material for beach nourishment. The purpose of the dredging has been
to maintain navigation within Banks Channel (landward of Figure 8 Island) and Rich Inlet
and to provide a source of sand for enhancement of oceanfront beaches. Permits issued by
NCDCM for various dredge and fill projects on Figure 8 Island where sand placement
occurred on the south half of the island are listed in Table 1-1. Dredging Banks Channel by
Figure 8 Island has occurred on multiple occasions.
During late 1992 and early 1993, the Figure 8 Island Homeowners' Association undertook a
large-scale beach nourishment project on the southern half of the island, which had severely
eroded due to long-term chronic erosion, and a series of storms. Sand for beach
nourishment purposes was dredged from the small boat navigation channel extending along
the western side of the island. The project was considered a success in restoring the small •1
GNV/2000/Reports/99265-Final EA/InletMgmtPlan6/16/04 6

boat channel and providing sand for beach nourishment using sand that had shoaled in the
channel and boat basin.
Table 1-1 NCDCM Permits Issued to Figure 8 Island or Groups of Owners
on Figure 8 Island
Permit Number
Date Issued
Location/Project
Volume Date of
Construction
11-85 2/85 Bank's Channel 46,000 1985
26-92 11/92 Bank's Channel 550,000 10/93
12-99 1/99 USCOE Spoil Island and
Banks Channel 600,000 4/99
The 1992-93 beach renourishment project performed as predicted over the next 2 years with
the overall design template remaining intact until 1996 following the occurrence of Hurricane
Bertha (July) and Hurricane Fran (September). These hurricanes caused the loss of the
remaining sand within the beachfill template and the exposure of many homes to damage
during routine winter wave and storm tide events.
The vulnerability of these beachfront dwellings to damage from high frequency storm events
resulted in an emergency beach renourishment project at Figure 8 Island in February to
April of 1999. The source of sand for this project was material located within the spoil island
immediately north of Mason Creek, used by the USCOE for ICWW maintenance material
disposal. This work was authorized by the North Carolina DCM and the USCOE in February
1999 allowing the placement of approximately 640,000 cubic yards along the southerly
12,500 feet of developed shoreline. A portion of this work was not completed along the
northern most 4,500 feet of the 12,500-foot total project length due to restrictions on
dredging during the sea turtle nesting moratorium (April 15 through November 15).
Approximately 450,000 cubic yards of sand was placed along the southerly 8,300 of Figure
8 Island's developed area in February-April 1999, and the remaining volume placed in 1999-
2000. During Hurricane Floyd, severe erosion caused sand loss under many homes and led
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to a determination by NCDCM that homes on the southern 11,500 feet of the developed
portion of Figure 8 Island are imminently threatened. There are 88 oceanfront homes in this
stretch of the island.
2.0 Physical Processes
2.1 Geologic Setting and Beach Processes
As is true on most coasts, the geologic setting of the study area controls the surficial
geomorphology, sediment type and availability and overall gradient. As such, the Mason
Inlet area is a product of the dynamic ocean environment acting upon unconsolidated barrier
islands.
The study area is located at the northern portion of an area known as the Georgia
Embayment (Hayes, 1994). The Georgia Embayment flanks the coastal plain on the trailing
edge of the North American plate (Inman and Nordstrom, 1971). The embayment that
comprises the Georgia Bight arches away from the continental shelf at the southeast edge
of the North American plate. This configuration of the continental shelf dictates the tidal
magnitudes along the Southeast coast.
During the Holocene period (around 6,000 B.P.), the sea level probably rose rapidly to within
a few meters of its present state. Subsequently, sea level has fluctuated and was likely at 6-
13 ftbelow present levels between 3,000 to 2,000 B. P. Since then, virtually still-stand
conditions have existed at the present sea level (Hayes, 1994).
Along unconsolidated coasts, large amounts of sediment are usually available and
morphological changes occur frequently. Thereby, marine processes continually modify
unconsolidated material, which is readily sorted and redistributed. The unconsolidated
material is sculpted into forms that are in a state of dynamic equilibrium with incident energy.
The changes in sea level mentioned above combined with the effects of wind, waves and
tide produced the geomorpholgy of the project area.
Holocene beach ridges of Figure 8 Island protrude seaward as a result of sand supply
furnished by littoral transport. The northern portion of Figure 8 Island has eroded at
GNV/2000/Reports/99265-Final EA/InletMgmtPlan6/16/04 $

moderate rates, while the southeastern portion has experienced significant accretion. The
updrift Figure 8 Island shoreline is elongating in the direction of the net littoral sand transport
causing erosion of the downdrift Shell Island side of Mason Inlet. Historically, this cycle of
updrift recurved spit growth, inlet migration and downdrift shoreline truncation is periodically
repeated as a new inlet catastrophically opens updrift (Brooks, 1988).
2.2 Wind and Wave Climate
2.2.1 Wind Climate
Directional winds for the project vicinity are provided by the US Army Corps of Engineers
WIS Station 42.
2.2.2 Wave Climate
The USCOE Wilmington District collected non-directional wave measurements at Johnnie
Mercers Pier on Wrightsville Beach between 1971 and 1975. The average significant wave
height and average wave period for the measurements were 2.55 feet and 7.88 seconds,
respectively (USCOE, 1977). The USCOE combined their measured wave records with
directional wave observations from the US Coast Guard station at Frying Pan Shoals Light
Tower to determine relative directional distribution of wave energy. Table 2-1 presents the
directional wave frequency of the observations. The shoreline orientation along this
segment of coast is aligned approximately 35 degrees to 215 degrees east of north.
Table 2-1. Relative Distribution of Wave Energy, Wrightsville Beach Vicinity
Incident Direction Wave Energy Percentage
N E 36.96
ENE 11.79
E 6.06
ESE 7.36
SE 11.42
SSE 10.89
S 15.52
Source: USGUt, 19//
Mare recent wave hindcast data, for the period 1976-1995, are prepared by the US Army
• Waterways Experiment Station (WES) as part of the Wave Information Study (WIS). These
data are available from the WES website and include the effects of tropical storm activity in
GNV/2000/Reports/99265-Final EA/InletMgmtPlan6/16/04 9

the 20-year database. The recent data sets were produced with improved methods that
corrected for apparent directional biases inherent in the older hindcast data sets. Summary
data tables for directional frequency of wave height and period for WIS Station 42 (located
at 34.00 N, 77.75 W) are provided in Appendix C of the EA (ATM and LMG 2000).
The specific directional distribution characteristics of the recent WIS wave data set vary from
the older, measured wave data. The WIS data result in a total of 88.5% of all wave energy
being incident on the local shoreline. This assumes that waves incident from 45° through
202.5° (measured clockwise from north) may impinge upon the local shoreline, which is
oriented about 35° east of due north. Of the incident offshore waves, the w8ed average
hindcast significant wave height is 3.3 ft and peak period is 7.6 seconds. It is noted that
WIS hindcast station 42 is located in approximately 30 ft of water offshore of Wrightsville
Beach, while the measured data were obtained in water depths less than 20 ft and are
subject to wave refraction and shoaling effects.
The WIS data indicates that 64.3% of the onshore-directed waves occur from directions
north of shore normal, while 35.7% occur from south of shore normal. These overall
percentages agree with the relative directional distributions reported for the measured data,
which total 62.2% north and 37.8% south of shore normal.
2.2.3 Littoral Transport
Littoral transport in the Mason Inlet vicinity is controlled primarily by fluctuations in wave
height and direction. Tidal and wind-driven currents are secondary sediment transport
mechanisms, but generally require initial suspension of the sandy sediments by wave action
followed by current transport.
Littoral transport along Wrightsville Beach and Figure 8 Islands is predominately from north
to south. A simple evaluation of the WIS hindcast and measured wave data presented
above indicate that greater than 60% of all waves occur from angles of incidence north of
shore normal. Upon breaking, these waves induce a longshore transport that is related to
wave energy and breaking angle by the equation for the longshore component of wave
energy flux:
P,S = (Ec9)b sin ab cos ab (Eqn. 1)
where Eb = pgH2~/8 and C9b = (gdb)'~2

GNV/2000/Reports/99265-Final EA/InletMgmtPlan6/16/04 1 ~

•
The USCOE (1977) utilized wave records and surveys to model wave refraction for the
Wrightsville and Carolina Beach area. Results were used to determine longshore
distribution of potential transport (refer to Eqn. 1 and Figure 2-1 ). Sediment budget
computations developed by the USCOE (1977; 1982) for north Wrightsville Beach indicate
littoral transport averages of 173,000 CY/Yr (net) toward the south and 685,000 CY/Yr
(gross).
For Wrightsville Beach, the USCOE has estimated the gross littoral transport to be
1,095,000 CY/Yr. This gross sediment transport is comprised of 769,000 CY/Yr toward the
south and 326,000 CY/Yr to the north, resulting in a net transport of 443,000 CY/Yr to the
south (USCOE, 1982). These transport values were based on the directionally adjusted
wave records collected at Johnnie Mercers Pier (as described previously) and represent
average conditions between Mason and Masonboro Inlets.
Littoral transport reversals are common in the vicinity of inlets such as Mason Inlet, primarily
due to:
(1) Seasonal shifts in wave direction; and
(2) Sheltering and refractive effects of the ebb shoal feature.
Mason Inlet exhibits a classic convex shoreline shape along the immediate downdrift
shoreline from Mason Inlet (refer to Figure 2-2). A convex shoreline is typical of ebb-
dominant inlets, where sand bypasses the inlet around the ebb tidal shoal feature. Wave
refraction along the ebb tidal shoal causes a reversal in the direction of sand transport south
of the inlet. As sand moves north towards the inlet, the sand deposits along the protected
beaches in the lee of the ebb shoal, thus these shoreline segments tend to accrete, causing
this shoreline perturbation. This phenomenon has been documented by Kana (1985 and
1988) among many others.
2.3 Significant Storm Events (1996-2000)
While most long-term predictions for littoral transport and inlet evolution consider average
annual wind and wave conditions, the project site is vulnerable to low-frequency storms that
have significant effects on local coastal processes. These storms are typically nor'easters
GNV/2000/Reports/99265-Final EA/InletMgmtPlan6/16/04 11

(winter storms) or tropical storms during the summer/fall. Recent years (1996-1999) have i
included both storm types; highlights are described below.
Tropical and winter storm events of significance are discussed in the 6-Month, 12-Month,
18-Month and 24-Month Monitoring Reports (ATM, 1997-1999). Significant Storm Events
are also discussed in the EA Report (ATM and LMG, 2000). Erosion rates and alterations to
the project site as a result of the Significant Storm Events are discussed in the referenced
documents.
Tropical storms and the approximate dates affecting the Wrightsville Beach vicinity, since
1996, are listed in Table 2-2. Eight tropical storm events have occurred since the summer of
1996. Significant winter storm events to the project site, including Northeasters, occurred
between the dates of September 1997 and September 1999. Figure 2-3 includes a map of
historical tropical storms, which have passed close to Wrightsville Beach.
Hurricanes and Nor'easters can produce dramatic changes in the shoreline and the inlet
configuration. Although tools are available to evaluate storm-induced beach profile changes
on a straight and linear beach, changes to inlet configuration are difficult to predict. The
most practical way to manage these unpredictable changes is to include the appropriate
emergency response in the Inlet Management Plan. If a low frequency storm event, such as
a severe Category 3 to 5 hurricane were to trigger any one of the maintenance parameters,
then a maintenance project would occur.
In regard to impacts of the project on system hydraulics during storm conditions, since the
project inlet cross section is similar to the inlet cross section that existed in the 1980's, the
project will not result in any significant changes in flows into the system during storm events
as compared to the inlet system that existed in the recent past.

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•

Table 2-2. Tropical Storm Events and Approximate Dates Affecting the Wrightville
Beach Area
1999 Dates
Hurricane Dennis August 29 to September 6
Hurricane Floyd
Hurricane Irene
July 15 and 16
October 17 and 18
1998 Dates
Hurricane Bonnie August 25 to 28
1997 Dates
Tropical Depression Danny July 23 to 25
1996 Dates
Tropical Storm Arthur June 18 to 20
Hurricane Bertha
Hurricane Fran
July 11 to 13
September 5 and 6
Appendix A includes tropical storm tracks for the years 1996, 1998 and 1999.
2.4 Shoreline and Profile Changes
2.4.1 Long-Term Changes
Long-term shoreline change trends adjacent to Mason Inlet are documented by the State
Division of Coastal Management in the form of shoreline change maps (DCM, 1996). The
State's analysis is based on digitized historical aerial photography, with the most recent
update extending from the 1940s through 1992. The State's analysis indicates that the
majority of Wrightsville Beach is accretional, due to the updrift influence of the Masonboro
Inlet north jetty and the Corps' placement of significant quantities of beachfill material along
the central portion of Wrightsville Beach since 1966. Following 1.4 million CY of beachfill
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13

placement in 1970, the Corps reported an average accretion rate of 47 CY/ft over a 6,700 ft
reach immediately north of the fill area. This occurred over 9 years, which equates to a total
of 5.2 CY/ft/yr accretion.
The Wilmington District, USCOE calculated sand losses and gains within the northerly area
of beachfill placement and immediately north at distance of 7,000 ft (stations 100+00 to
170+00). These sand losses were -5.8 CY/ft/yr from 1980 to 1979, -6.5 CY/ft/yr from 1981
to 1985 and -8.6 CY/ft/yr from 1987 to 1992, or an average sand loss rate of approximately
-6.9 CY/ft/yr. North of this shoreline segment adjacent to Wrightsville Dunes and Shell
Island Resort, i.e. stations 180+00 to 197+00, the beach sand volume changes were
generally stable to accretional. Sand gains along this shoreline segment were computed at
+0.0 CY/ft/yr from 1970 to 1979, +4.4 CY/ft/yr from 1981 to 1985 and +2.6 CY/ft/yr from
1987 to 1992, or an average of approximately +2.3 CY/ft/yr. These beach profile data were
sent to ATM by the USCOE based on surveys taken over the past 30 years (refer to
Appendix B). This shoreline segment includes the area of beachfill placement and the area
immediately north (i.e. Holiday Inn Sun Spree to Shell Island Resort) where sand spreads
and redistributes following the USCOE's Wrightsville Beach Renourishment Projects.
The long-term shoreline changes are as high as -5 feet per year within the first 0.25 miles
south of Mason Inlet, with a trend of stability to slight erosion (approximately 1 ft/yr)
extending south about 1.4 miles. The maximum long-term erosion rate extending north of
the inlet along Figure 8 Island averages -3 feet per year, with accretion limited to the
extreme north portion of the island. Long-term shoreline changes are shown on Figure 2-4.
Long-term trends of inlet migration (1971-1996) at Mason Inlet's south channel bank varied
between 51 and 153 feet per year, as determined by analysis of aerial photography
summarized in Table 2-3. A complete description of the inlet migration trends is found in the
EA report, Section 2 (ATM and LMG, 2000).

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Table 2-3. Mason Inlet Migration Rates Based on Historical Aerial Photography
Photograph North Channel Bank Primary Channel South Channel Bank

ate

Time
(years) Location of
Updrift Shoulder
(ft from
baseline) Net
Change
Rate
(ft/yr) Location of
Thalweg
(ft from
baseline)
Net
Change
Rate (ft/yr) Location of
Downdrift
Shoulder (ft
from baseline)

Net Change
Rate (ft/yr)
13-Mar-62 2582 2891 3382
9.63 0.8 -6.3 -20.1
01-Nov-71 2590 2830 3188
6.69 38.9 47.5 51.7
11-Aug-79 2850 3148 3534
5.77 89.1 207.9 167.4
27-May-85 3364 4347 4499
11.32 140.5 154.6 153.6
23-Sept-96 4955 6097 6238
1. Measurements obtained trom verncal aerial photography.
2. All aerials 1 inch = 1,000 feet except 1962 at 1 inch = 2,000 feet as reported by USCOE.
• 3. Baseline established to coincide with common geologic features found on aerial photography.
4. No photo corrections for scale inconsistencies
2.4.2 Recent Shoreline Changes
Recent shoreline changes in the vicinity of Mason Inlet are documented for Shell Island in
the series of monitoring reports (ATM, 1997-1999). The first 1,000 ft south of the present
inlet location experienced general erosion between September 1997 and October 1999,
averaging 80 ft (based on 0 NGVD). Volumetrically, the same reach lost 22,200 CY above
NGVD. Over the same time period, the next segment (extending from 1,000 to 2,500 ft
south of the inlet) accreted an average of 40 ft. The corresponding volume gain above
NGVD was 10,800 CY. The profiles extended only to wading depth and these are not
deemed a complete representation of the actual sand losses or gains. Comparison plots of
the recent profile changes south of Mason Inlet are provided in the Appendix B.
More recent shoreline changes for Figure 8 Island are presented by Cleary and Hosier,
1990. Their results, based on 1984-1989 surveys, indicate average annual dune erosion
losses of 3 to 9 ft/yr (average 5.8 ft/yr), extending northward about 12,000 ft north of Mason
GNV/2000/Reports/99265-Final EA/InletMgmtPlan6/16/04 15

Inlet. Over the same reach, high water line erosion ranged from 13-26 ft/yr, with an average •
of 18.5 ft/yr (Figure 2-5). The beaches eroded at very high rates although a 1985 beach
nourishment project placed some 46,000 CY of sand from Banks Channel along this
shoreline. According to Cleary and Hosier (1990), the documented high rate of erosion
represents average wind and wave conditions without occurrence of a major storm although
they note that the southerly 4,100 feet of developed shoreline property was influenced by
Mason Inlet.
Recent inlet migration rates (1992-1995) have peaked at a rate of over 450 ft/yr.
Acceleration of the migrating inlet is partially attributed to the gradual siltation of Mason's
Creek, in concert with dredging of Banks Channel, behind Figure 8 Island, with subsequent
beach nourishment in the 1980s and 1990s. Both of these occurrences shifted the tidal
flow forces from a generally east-west direction to a north-south direction. These flows,
coupled with the prevailing littoral transport direction and large quantities of sand placed on
Figure 8 Island have undoubtedly promulgated the acceleration of southward inlet migration.
2.5 Inlet Bathymetry and Shoaling •
Monitoring surveys for the south channel bank at Mason Inlet have been performed
periodically since more detailed studies of inlet migration began in June 1996. Figure 2-6
presents a comparison plot of successive profiles for the period of September 1996 to
January 1997.
Since September 1997, the inlet has both narrowed (from 1210 to 840 ft) and deepened,
from an average of -8 to -10 ft NGVD to an average of -15 to -18 ft (NGVD). This narrowing
is associated with the incoming, northerly littoral transport from Figure 8 Island, the fixed
position of the geotextile revetment, and the natural force to convey a similar volume of
water with each tidal cycle (ATM, 1998).
Inlet infilling is evident in the comparison of a June 1996 bathymetric survey and the July
1999 bathymetric survey of the inlet channel. Figure 2-7 provides a graphic overlay of these
contours to illustrate areas of inlet deposition. An analysis of the change in interior inlet
shoal planform was performed for the areas above the mean low water and above the 0 ft
NGVD contour. Over this 3-year period, the inlet's cross-sectional area at mean high water
decreased 39.5 percent and the cross-sectional area of the shoal increased 43 percent.
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As Mason Inlet migrates, the ebb tidal shoal builds as a large intertidal planform that
migrates with the inlet channel. At Mason Inlet, these processes are evidenced by the
prograding shallow shoal on the Figure 8 Island side of the inlet, the growth of the shallow
flood and ebb shoals, and the relatively "healthy" (i.e., typical) beach and dune system south
of the area of the inlet. Sand trapped within the inlet periodically is moved further inland as
strong currents associated with high storm tidal surges (i.e. northeasters and hurricanes)
carry sand into Mason Creek and the interior channel shoals.
2.6 Inlet Influence
The inlet's influence (based on the NCDCM long-term shoreline change maps) extends
about 1.2 miles to the north and 1.4 miles to the south, although the influence of the
Masonboro Inlet north jetty affects a large portion of Wrightsville Beach. For this reason, the
proposed beach profile-monitoring plan (Section 3) includes a shoreline segment extending
beyond these distances, or 2.2 miles north and 2.5 miles south of the relocated inlet.
• 2.7 Sediment Budget
2.7.1 General
This section presents a conceptual sediment budget for Mason Inlet, based on the available
existing data. It is by no means comprehensive; however, this approach provides a
framework from which to evaluate the changes that occur as the relocated inlet adjusts
following construction. The conceptual sediment budget will be evaluated and refined in
accordance with the acquisition of detailed hydrographic and land surveys summarized in
the monitoring plan described in Section 3.
2.7.2 Regional Littoral Transport
Regional littoral transport was evaluated based on wave refraction and longshore transport
computed by the Corps (USCOE, 1977). Table 2-4 presents a summary of gross and net
transport rates at specified distances from Mason Inlet. The analysis indicates an increase
in net transport moving south toward Mason Inlet, with a reduction south of the inlet and
slight increase moving south on Wrightsville Beach.
•
GNV/2000/Reports/99265-Final EA/InletMgmtPlan6/16/04 17

2.7.3 Figure 8 Island •
The conceptual sediment budget for Figure 8 Island is based on the erosion rates
determined by Cleary and Hosier (1990). The southern 4,100 ft of the island averages 7.5
ft/yr and 19.5 ft/yr erosion for the dune and high water line, respectively. Similarly, the
subsequent 8,000 ft north segment averages 4 ft/yr (dune) and 15 ft/yr (high water).
In order to estimate profile volume changes to depth of closure, a conversion factor of 1
CY/ft for each foot of shoreline change is adopted (USCOE, 1977; Overton and Fisher,
1996). This factor will be adjusted, as needed, following the completion of several
monitoring events. Application of this factor to the high water change rates results in an
average annual erosion loss of approximately 200,000 CY/yr.
2.7.4 Wrightsville Beach and Shell Island
The north end of Wrightsville Beach adjacent to Mason Inlet exhibits a classic convex
shoreline shape. Wave refraction along the existing ebb tidal shoal causes a reversal in the
direction of sand transport south of the inlet. As sand moves north towards the inlet, sand
deposits along the protected beaches in the lee of the ebb shoal, thus this shoreline .
segment tends to accrete as a result of the inlet's location. The length of shoreline that is
significantly wider, as a result of this inlet related sediment reversal and resulting convex
shoreline shape, is approximately 1,500 feet. Adjacent to Shell Island Resort south to
Wrightsville Dunes the additional beach width is largely the result of the localized sediment
transport processes at the inlet, and thus are directly attributable to the shorelines proximity
to Mason Inlet.
The recent, monitored profile changes for Shell Island Resort were utilized to estimate
volume changes for the 2,500 ft beach segment south of Mason Inlet. Application of the
average annual shoreline changes to the shoreline-volume relationship results in a net
erosion loss of 10,000 CY/yr. In comparison, historical profile changes calculated by the
USCOE (as described in Section 2.4.1) indicate that this shoreline was stable to slightly
accretional until recently. The sand gains averaged approximately 2.3 CY/ft/yr between
1970 and 1992 although this period was prior to the inlet's direct impact on the local
shoreline. South of this point, historical volume changes are estimated based on the Corps
erosion data (USCOE, 1982).
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•
2.7.5 Mason Inlet Flood Shoal
Estimates of the inlet's historical sediment trapping capacity are not readily ascertained due
to the migratory nature of the inlet. ATM estimated interior shoaling rates by comparing
cross-section surveys conducted in 1996 and 1999 (refer to Section 2.5). Over the three-
year period, the average annual deposition was determined to be approximately 75,000 CY.
2.7.6 Mason Inlet Ebb Shoal
There are no reliable estimates of historical ebb shoal growth at Mason Inlet. To estimate
the equilibrium volume of the relocated inlet ebb shoal, ATM conducted an analysis of
predicted volumes based on research completed by Walton and Adams, as documented in
Coastal Processes with Engineering Applications (Dean & Dalrymple, 1993). The
relationship for a moderate wave climate is:
V = 10.7 x 10-s Tp 1.23
where V is ebb shoal volume in cubic yards (CY) and TP is tidal prism in ft3.
Using this relationship and assumed average tidal prisms as shown we computed:

Inlet Average
Tidal Prism
(million cu. ft.) Computed Ebb
Shoal Volume
(million CY) Estimated Ebb Shoal
Volume
Cleary & Marden
(million CY)
Mason (existing) 50 0.316 0.785
Rich 350 3.456 8.109
Masonboro 800 9.554 12.295
Mason (relocated) 150 1.219 N/A
Based on this methodology, the predicted ebb shoal volume is roughly 3.86 times the size of
the existing predicted ebb shoal volume.
Also indicated in the table are estimates of ebb shoal volumes reported in Shifting
Shorelines: A Pictorial Atlas of North Carolina's Inlets (Cleary &Marden, 1999). It is noted
that these estimates are based on observed shoal areas, assumed to be computed from
aerial photos, and taken to a depth of 20 ft. Assuming a reasonable "visible" depth in the
GNV/2000/Reports/99265-Final EA/InletMgmtPlan6/16/04 1 g

inlet of 10 ft to demarcate the outer boundary of the shoal, an average depth of 6.5 ft over
an area of 31.36 acres results in an estimated volume of 683,000 CY. These estimates are
subjective, based on the "visible" area of the shoal and a continuous base elevation of -20
ft. This method overestimates the shoal sand quantities as it does not recognize the sand
contained within the natural beach planform (i.e. the sand quantity that exists naturally within
the beach profile). The assumed shoal crest elevation and fixed base elevation thus
provides only a rough estimate of shoal volume.
In order to verify the computed shoal volumes, an analysis of the surveyed ebb shoal at
Mason Inlet was conducted using a December 1999 hydrographic survey. Since a typical
profile in the absence of an inlet or beachfill project is not readily available due to the recent
beach nourishment projects at both Figure 8 Island and Wrightsville Beach, an equilibrium
beach profile given by the y = Ax2~3 relationship was superimposed on representative
sections of the surveyed shoal.
The Wilmington District (1982) reports the local depth of closure typical of Wrightsville
Beach to be -20 ft NGVD, which was applied along the seaward boundary. The mean grain .
size for the beach in the vicinity of the inlet is 0.24 mm (the Corps reports 0.20 mm along
Wrightsville Beach nourished beach area). An area considered to be the ebb shoal
boundary was identified to compute the volume differences between the equilibrium and
existing shoal profiles. This analysis results in ebb shoal volumes of 383,000 CY based on
atypical profile with a d50 sand grain size of 0.24 mm. Thus, the predicted ebb shoal volume
of the Mason Inlet ebb shoal based on Walton and Adams is 316,000 CY and the computed
ebb shoal volume is 383,000 CY, the latter of which is considered more reliable than the
estimated volumes based on tidal prisms. Thus, the existing ebb shoal is near an
equilibrium and likely bypasses a majority of the incident littoral transport.
The timing of new ebb shoal development is also of note. In the case of Captain Sams Inlet
(based on the Mason report), the surveyed ebb shoal (abandoned) volume was 1.439M CY
and the computed equilibrium volume based on the Walton and Adams method was 1.17M
CY (J. Mason, 1986). It was reported that after 2 years, the surveyed ebb shoal volume was
34% of the predicted total, and that it would take approximately 8.7 years to reach this
"theoretical" limit. It was also determined that a migrating inlet would have lower ebb shoal
volumes than that predicted by the Walton and Adams method.
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•
Therefore, the new ebb shoal at Mason Inlet will develop over 3 to 8 years to reach an
equilibrium volume, estimated to be 1.2 million CY. This volume is based on existing ebb
shoal volume predictions of 316,000 CY as described above. ATM's computed maximum
ebb shoal quantity of 383,000 CY could result in a slightly higher volume at 1.5 MCY.
During the first year or two following construction, much of the littoral transport will be
deposited in the ebb shoal feature. It is our opinion that the littoral material "lost" to ebb
shoal formation will be balanced both from the excess sand placed along the Figure 8
beaches (projected to be 400,000 - 450,000 CY) and the southerly beaches where the
existing inlet's abandoned ebb tidal shoal (300,000-380,000 CY) will migrate onshore.
Aside from the first year or two, the anticipated rate of annual ebb shoal deposition at Mason
Inlet should not exceed the observed annual ocean bar shoaling rates for Carolina and
Masonboro Inlets, which range between 160,000 and 190,000 CY and are periodically
dredged for navigation access.
• 2.7.7 Dredging Volumes
No material has been dredged from Mason Inlet that would affect the sediment budget.
Future spoils from maintenance dredging of the inlet channel and sedimentation basin
(estimated to be 350,000 to 375,000 CY every 4-5 years) will be placed on the updrift and/or
downdrift beaches, based on the results of the monitoring plan and analysis of impacts to
adjacent beaches.
2.7.8 Beachfill Placement
Historical beachfill projects have occurred on both Figure 8 Island and Wrightsville Beach.
Three beach nourishment projects were constructed along the southern 10,000 feet of
Figure 8 Island's developed shoreline between 1985 and 1999 to protect beachfront
properties from storm damage and land losses. The total volume of sand placed was nearly
1.2 million CY or an average of 85,400 CY/yr. This average annual quantity has not been
sufficient to overcome the average annual requirement of 104,000 CY as estimated by
Cleary and Hosier (1990).
Along Wrightsville Beach, beachfill has been placed periodically since 1965, with the north
limit of fill approximately 6,000 ft south of the present inlet location. The most recent project
GNV/2000/Reports/99265-Final EA/InletMgmtPlan6/16/04 21

has influenced the south portion of the Shell Island monitoring area, and is thereby
accounted in the recent erosion analysis. It is assumed that the Federal beachfill project
along Wrightsville Beach which has been authorized by Congress (since the 1960's) will
continue for the duration of future maintenance of the Mason Inlet Project.
2.7.9 Conceptual Sediment Budget
The conceptual sediment budget is illustrated in Figure 2-9. Again, it is imperative to realize
that this is an initial attempt to quantify the littoral processes in the inlet region and must be
updated based on actual measurements surveyed and analyzed during the implementation
of the comprehensive monitoring plan.
3.0 Physical and Biological Monitoring Plan
The following plan outlines various components of the physical and biological monitoring
that will be used to evaluate potential impacts associated with the inlet relocation project.
The EA should be referred to for additional information regarding project design and
potential impacts to environmental resources.
3.1 Physical Monitoring Network
3.1.1 Beach and Offshore Profiles
Beach and offshore profiles shall be measured at 35 reference monuments to be
established along Figure 8 Island, Mason Inlet and the Wrightsville Beach shoreline
adjacent to the newly relocated Mason Inlet Project Area. Profiles will extend along the
shore normal azimuths, from the backbeach (west of the existing dune or berm feature)
approximately 1,500 ft offshore (to the -25 ft NGVD contour). The average spacing
between monuments will range from 250 ft near the inlet to 1,000 ft at distances greater
than 1,500 ft from the new and the closed Mason Inlet location. Refer to Figure 3-1 (3
sheets) for the physical monitoring network.
Beach profiles will be performed immediately before and after construction. Additional
surveys will be performed quarterly for the first year following construction, at 18- and 24-
months post-construction, and annually thereafter for the life of the project (i.e., as long as
New Hanover County is responsible). Profile surveys will also be conducted following
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• significant storm events based on the concurrence of the County, USCOE and the NCDCM.
Included in the analysis for apost-storm survey will be an even-odd type analysis to
determine the effects of the storm due to the inlet versus regional storm erosion.
Vertical and horizontal control will be referenced to NGVD 1929 and North Carolina State
Plane Coordinate System (NAD 1983), respectively. Survey line azimuths will be identified
by magnetic bearing. Survey data will be submitted to the DCM in the form of cross-
sectional profile plots and on 3.5" disk in the NCDCM designated digital format. A report will
be submitted for each post-construction survey which will document the results of volumetric
and shoreline change analyses to the Inlet, sedimentation basin and the ebb tidal shoal(s) in
the Project area and along adjacent beaches.
3.1.2 Inlet Area Bathymetry
Bathymetric surveys of the inlet channel and sedimentation basin will be measured prior to
construction, immediately following construction, at quarterly intervals for the first year
following construction, and at 6-month intervals for as long as the project remains viable.
The surveys will consist of 13 lines spaced approximately 150 ft apart. The lines will run
approximately 1,000 to 1,500 ft in a direction perpendicular to the inlet channel. An
additional bathymetric transect will be surveyed down the centerline of the inlet channel and
across the ebb shoal feature. The data and volumetric change analyses will be included in
the 1-year and 2-year post-construction hydrographic monitoring reports indicated above.
3.1.3 Surficial Sand Sampling
Surface sand samples will be collected immediately following construction and concurrently
with the annual beach profile surveys. Sand samples will be collected along 8 (8) longshore
transects. Sand samples will be collected at elevations +10, +5, 0, -5, -10, and -15 ft
NGVD. Samples will be analyzed using standard ASTM procedures to determine the grain
size distribution (8 sieves). Results will be submitted to the DCM with an analysis of the
longshore and cross-shore adjustment of the beach sediments, inlet channel banks, and
ebb shoal.
•
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3.1.4 Aerial Photography •
Color, vertical aerial photographs will be flown along the Project shoreline at the time of
each full monitoring survey (i.e., inclusive of beach profiles and bathymetric surveys). The
scale of the photographs will be 1 inch equals 200 feet. The flight line will begin 3,000 feet
north of the inlet and proceed southward at distance of 10,000 feet, which is approximately
7,000 feet south from the relocated inlet.
Each photograph will include the entire beach, nearshore environment, and sufficient upland
features (i.e., beach-fronting buildings, roads, etc.) to determine the location of any
photograph. The shoreline location in any image will be approximately half way across the
width of the photograph. Consecutive photographs will have sufficient overlap
(approximately 20%) to identify common points of interest. Photographs will be taken prior
to 2:00 PM to avoid building shadows cast towards the beach.
Local predicted tides will be used to determine flight times so subsequent photography
events will occur during similar times in the tidal cycle. Photographs will not be rectified, but
horizontal ground control will be established by setting sufficiently sized aerial targets (4 ft x
4 ft) on representative reference monuments in the days prior to the flight. In the event that
a monument is either not visible due to vegetation or located in an area of heavy traffic, the
aerial target will be offset from the monument along the profile azimuth. This offset distance
and azimuth will be kept in the target-setting party's field notes for use during any
subsequent photographic analysis.
3.1.5 Video Monitoring
At the request of the US Fish and Wildlife Service, a video camera system will be deployed
atop the Shell Island Resort building to monitor the construction and post-construction
response of the relocated inlet. This system will be programmed to capture several scenes
(both zoomed and wide angle views) of the inlet and adjacent beaches. The system will be
deployed for the first year following the project construction, with images collected at a
minimum of 4 hour intervals and stored in JPEG compressed format on a local website. The
web address will be made available at the time of installation, to allow interested parties
access to the captured images.
•
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• 3.2 Biological Monitoring Network
The goal of the biological monitoring plan is to assess and document potential effects of
project activities on primary productivity, faunal utilization, and substrate texture/organic
content of marsh areas adjacent to the proposed work zone. Pre- and post-construction
monitoring will provide quantitative data and qualitative observations that can be used
determine if any deleterious effects to the marsh habitat are directly attributable to the inlet
relocation project. The extent to which monitoring parameters will be affected depends on
various conditions (e.g. the character of the dredged material, tidal and current regimes,
etc.) and any system responses will likely be distributed in a linear fashion from Mason
Creek.
3.2.1 Biological Monitoring Parameters
Selection of monitoring parameters has been based upon those factors potentially impacted
by project activities and those readily sampled and evaluated. The following monitoring
elements have been selected:
• (1) Spartina stem density
(2) Mature (>30 cm ht) Spartina stem height
(3) Percent sand, silt, and clay of surface substrate
(4) Percent organic content of surface substrate
(5) Sedimentation rate
(6) Benthic macroinvertebrate utilization
(7) Wildlife utilization
(8) Creek marsh edge erosion
Evaluation of each of these parameters is discussed in the following section.
3.2.2 Biological Sampling and Analysis Methodology
Sampling efforts will focus on the area of potential impact where biota and physical
conditions (e.g. soil texture) are most likely affected by project activities and associated
perturbations such as altered flooding regime and sedimentation. As discussed earlier, any
perturbations will manifest in system responses distributed linearly from Mason Creek.
• Therefore, three permanent 300 ft monitoring transects will be established along anorth-
south axis on both sides of Mason Creek (totaling six transects). Five one-meter square
GNV/2000/Reports/99265-Final EA/InletMgmtPlan6/16/04 25

quadrats for each transect (located 5, 50, 100, 150 and 300 ft away from Mason Creek) will •
be sampled for stem density and height of Spartina. The quadrat located farthest from
Mason Creek will serve as the control plot for each transect. (Refer to the enclosed map
depicting monitoring transects and plots.)
Sediments will be characterized according to percent sand/silt/clay and percent organic
matter. A composite sample will be collected for the 5, 50, 100, and 150-foot plots. One
sample will be collected for each control plot. In addition, metal rebar installed flush with the
sediment surface prior to project construction will used to evaluate sediment deposition
and/or loss over time for each plot.
Faunal utilization of marsh habitat will be evaluated through species lists and relative
densities of epibenthic macroinvertebrates and wildlife along transect corridors. Indirect
evidence and direct observation will be used to document the presence of a species within
the transect corridor. Each transect corridor will extend 150 feet away from Mason Creek
and will be 3 feet wide. Separate control transect corridors (150 feet by 3 feet) will be
established in an east-west orientation as depicted on the enclosed map. •
The distance from the plots nearest the creek to the waterward edge of the marsh will be
measured during monitoring events in order to quantify any erosion that could be a
secondary impact from the project. Compensatory mitigation for potential marsh edge
losses along the creek attributable to erosion from increased boat wakes is addressed in
Section 6.0, Mitigative Measures.
Each survey will incorporate photographic documentation depicting site conditions along
each transect corridor. During each monitoring period, close-up and panoramic views will
be photographed at designated stations.
Pre-dredging and the post-dredging mean values of each parameter will be statistically
compared using Analysis of Variance (ANOVA)/paired t-tests or Wilcoxon signed rank tests.
Ninety-five percent confidence intervals will be used to determine statistically significant
differences of means (means will be significantly different if confidence intervals do not
overlap). Proximal and/or distal changes (if any) in sedimentation rates, stem density and/or •
stem height will also be statistically determined.
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•
3.2.3 Biological Monitoring Schedule
The effects of any perturbation on vegetative conditions will be most pronounced and
detectable during active growth and development. Therefore, monitoring will occur during
the end of the growing season (September/October) once each year subsequent to project
completion for a period of two years. Sampling for baseline conditions will be conducted in
the September/October prior to project initiation (provided that there is sufficient time once
the project permit has been obtained). An immediate pre-construction survey (conducted
within 30 days prior to project initiation) will detect changes resulting from storm events
during the elapsed time between June/July and the
start of project construction. A total of four monitoring events will be used to determine if
impacts are directly attributable to project activities. All the parameters discussed in the
previous section will be evaluated during each monitoring event. After the second annual
post-construction survey, annual surveys will continue but will include only 2 quadrats (50
and 150 ft from Mason Creek) per transect.
•
3.2.4 Biological Report Documentation
Monitoring reports documenting site conditions and findings will be prepared and submitted
annually to the Division of Coastal Management, the U.S. Army Corps of Engineers, and the
Division of Water Quality by December 15th (following the September-October monitoring
event). Annual monitoring will be submitted to the USCOE on December 15th of each year.
The following information will be provided in each report:
(1) Project overview
(2) Site parameters monitored
(3) Methodology used to evaluate parameters
(4) Data analysis
(5) Summary of findings
(6) Prints of photographs at specified stations
(7) Maps depicting location of transects and sampling plots.
•
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•
3.3 Managed Systems Approach for Maintenance and Remedial Actions
3.3.1 Overview
The development of the managed systems approach assumes that the inlet is relocated and
that monitoring, as described in Section 3.2 is conducted at the regularly specified intervals.
The results of the monitoring plan will be analyzed to determine whether or not the following
predetermined "thresholds" are exceeded. If these "thresholds" are exceeded for two
consecutive years, the County will commence inlet maintenance dredging with sand placed
along the affected shoreline segments during the next scheduled maintenance event or, if
this work is not scheduled for occur for 2 or more years, the work will commence within an
18-month period. This schedule will allow for maintenance to be scheduled with reasonable
timeframes for planning, design, engineering and contracting for the next opportunity to
dredge (i.e. November 15th to March 31St annually). It is anticipated that this inlet-related
maintenance work would be implemented under the authorizations provided for in the State
and Federal construction permits for the initial relocation work. If a supplemental permit is
required, additional time may be required for permit processing and acquisition in order to
begin the construction work. The final recommended sand placement volumes, shoreline •
lengths and unit fill placement will be a function of the sand losses measured by the
Physical Monitoring program.
3.3.2 Trigger 1 -Volumetric Losses
An analysis of recent shoreline and volumetric data identified recent volumetric change
trends within the project and adjacent beach areas (Section 2.7). This data was analyzed to
determine a representative "baseline" condition that could be properly selected, and thereby,
provide the basis from which maintenance and/or remedial action will be required.
A sediment control volume approach is proposed to analyze the profile monitoring data and
evaluate the need for corrective actions. Along the monitoring area, control volume "cells"
are defined laterally as shown on Figure 3-2. The control volume cells were designated by
shoreline reach (based on location, coastal processes, and project features) and extend
seaward to the pre-project -12 ft NGVD depth contour.
Although volume change analysis to depth of closure would be computed to the -20 ft depth •
contour, problems in defining an "impact" can develop where deepwater sand gains
GNV/2000/Reports/99265-Final EA/InletMgmtPlan6l16/04 28

• disproportionately outweigh the nearshore sand losses. Thus, basing the need for
maintenance work or corrective actions on calculations of beach profile volumes over the
entire width of the beach profile (i.e., from the upland back-beach to depth of closure), can
mask the degree of vulnerability of the remaining upper beach. This is particularly evident
when a substantial fraction of sand moves from the nearshore portion of the profile into
relatively deep portions of the profile (-12 to -18 ft NGVD) where sand is less likely to move
back to the upper, protective portion of the beach profile. Thereby, computing sand volume
loss/gain quantities to the -12 ft NGVD contour, for the purpose of establishing whether an
"impact" has occurred fairly represents the sand within in the upper, emergent portion of the
profile and avoids the problems associated with survey error at increasing depths/distances
along the profile.
The average end method will be used to compute quantities of sand losses and gains within
a control volume cell. The overall impacts and spatial variation as the result of storm events
will be determined in order to adjust the total storm-related sand losses within a control
volume cell. It is acknowledged that some increased impact is likely to occur adjacent to
the inlet and that this impact will be deemed inlet-related. However, sand losses along the
adjacent, distant cells (i.e. cell #1 and cell #5) will be used to determine the "background"
storm-related sand losses. Following a severe storm event the beaches will be surveyed
and the net average storm-related sand volume losses will be determined using the profile
data surveys beyond a 5,000 ft distance of the inlet, both updrift and downdrift cells (i.e. cell
#1 and cell #5). This resulting volume will be subtracted from the computed changes within
these shoreline control volume cells. This "background" loss determination will also be
applied to adjust the adjacent shoreline control cell volumes.
Following inlet closure, shoreline control volume Cell #4 (refer to Figure 3-2) will initially gain
sand as the ebb tidal shoal moves onshore over an estimated 2-year period. After this ebb
shoal attachment, the wider sandy beach will slowly equilibrate over several years as the
sand redistributes north and south. The net result will be a straightening of the adjoining
shorelines over time (i.e. 3-5 years following inlet relocation) as the submerged portion of
the beach profiles and the shoreline adjusts with sand spreading north and south. As
described in Section 2.4.1 of this report, at present the north end of Wrightsville Beach,
adjacent to Mason Inlet, exhibits a classic convex shoreline shape. South of the inlet,
wave refraction along the ebb tidal shoal causes a reversal in the direction of sand transport.
GNV/2000/Reports/99265-Final EA/InletMgmtPlan6/16/04 29

As sand moves north towards the inlet, sand deposits along the protected beaches in the •
lee of the ebb shoal, thus this shoreline segment tends to accrete as a result of the inlet's
location. Thereby, the shoreline south from Mason Inlet (prior to inlet relocation) is
significantly wider for a distance of some 1,500 ft as a result of this inlet related sediment
reversal.
As a result, following inlet relocation the expected shoreline equilibration along Cell #4 is a
net loss of beach width from the Shell Island Resort south approximately 1,500 ft. This loss
is reflected in the "threshold" sand volume change shown in Table 3-1 for Cell #4, to account
for this future erosion. This sand loss and shoreline equilibration is expected to occur over a
period of 3 to 5 years following inlet relocation. As a result, this beach will adjust landward
because the new inlet position will be some 2,000 to 2,500 ft north. The beach losses will
be greatest (estimated at a loss of 100 to 130 ft beach width adjustment) fronting the Shell
Island Resort gradually decreasing to no net loss in the vicinity of Wrightsville Dunes
Condominiums. The recommended "threshold" loss volume that would trigger amelioration
for sand losses in Cell #4 is 10 CY/ft/yr or 37,000 CY/yr over a two consecutive years.
South of the new inlet position a similar convex shoreline shape will tend to develop along
Cell #3.
The actual pre-project base sand volume within discrete cells will be based on the
immediate post construction surveys. Table 3-1 presents the recommended "threshold"
erosion volume triggers for the adjacent beach cells.
Table 3-1. Preliminary Erosion Volume Thresholds
Cell Length (ft) Volume Trigger
1 7,000 -137,000 CY/yr*
2 3,700 -94,000 CY/yr*
3 3,400 N/A -Inlet zone
4 3,700 -37,000 CY/yr
5 8,000 -72,000 CY/yr
" beyond total sand volumes placed within Cells #1 and #2 during the initial inlet relocation project
•
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• The trigger volumes along discreet shoreline segments were computed based on the past
beach sand loss rates for individual profiles surveyed. Beginning at the north, Cell #1 along
the Figure 8 Island beaches, the average erosion rates were determined based on studies
by Cleary and Hosier (1990) at 15 ft per year (refer to Sections 2.7.3 and 2.4.2 of the Mason
Inlet Management Plan (MIMP), Appendix P of the EA). Applying a conversion factor of 1
CY/ft to estimate profile volume changes to depth of closure (USCOE, 1977; Overton and
Fisher, 1996) results in a total sand volume loss rate of 105,000 CY (15 CY/ft x 7,000 ft) for
the Cell #1. Since the annual average conditions can be expected to vary by up to 50%, a
30% loss exceedance is built into the proposed volume thresholds that results in a threshold
loss rate of 136,500 CY. All volume loss thresholds were rounded to the nearest thousandth
such that a value of 137,000 CY/yr resulted.
Similarly, along Cell #2 fronting the Figure 8 Island southernmost developed shoreline, the
annual average erosion rates were determined based on studies by Cleary and Hosier
(1990) at 19.5 ft per year (refer to Section 2.7.3 and 2.4.2 of the MIMP). Applying this rate
to the conversion factor of 1 CY/ft along a 3,700 ft length of shoreline results in a total sand
volume loss rate of 72,150 CY (4 CY/ft x 3,700 ft) for Cell #2. The 30% loss exceedance,
above the average background erosion rate, was applied resulting in a threshold loss rate of
94,000 CY/yr (rounded to the nearest thousandth).
Cell #4 and Cell #5 were based on the USCOE beach profile data sets sent to ATM and
analyzed for volume loss rates. The results of these analyses indicated average annual loss
rates of 6.9 CY/ft and 7.7 CY/ft. The 30% loss exceedance, above the average background
erosion rate, was applied resulting in a threshold loss rate of 37,000 CY/yr (Cell #4) and
72,000 CY/yr (Cell #5), respectively.
Since annual average conditions can be expected to vary by up to 50%, a 30% loss
exceedence is built into the proposed volume thresholds. These volume thresholds must be
exceeded (averaged over the cell) by the values indicated, over a minimum of two
consecutive years to trigger remedial, corrective actions. It is also important to realize that
the initial year following beachfill placement along Figure 8 Island, sand losses will result in
greater than average recession rates, as the beachfill construction template adjusts to an
equilibrium profile.
GNV/2000/Reports/99265-Final EA/InletMgmtPlan6/16/04 31

The volumetric triggers should be reevaluated by the County, NCDCM and the USCOE after •
the first year of monitoring.
3.3.3 Trigger 2 -Sedimentation of Mason Inlet and Sedimentation Basin
The post-construction shoaling rate of the inlet throat and sedimentation basin (Cell 3) is
estimated to be 375,000 CY over a projected 4 to 5-year maintenance interval. This
projection is based on the regional average littoral transport rates and measured changes at
Mason Inlet over the past 3 years (ATM and LMG, 2000). This represents 75,000 to
100,000 CY/yr of shoaling within the inlet channel, north inlet shoulder and the
sedimentation basin. Thus, monitoring surveys of the inlet throat and sedimentation basin
will be analyzed for shoaling rates in order to evaluate this trigger. Shoaling during the first
year post-construction is anticipated to be higher than the existing average. Thereafter, if
the average projected shoaling totals are exceeded by more than 30 percent (over a
repeated period of 2 years, resulting in a projected accumulation to exceed the 5-year total),
maintenance dredging will be triggered and work initiated to perform maintenance dredging
in the winter of the year that shoaling is expected to reach approximately 375,000 CY.

3.3.4 Trigger 3 -Inlet Migration Threshold
An inlet "corridor" has been established along a 1,000 ft length of Figure 8 Island (refer to
Figure 3-1 ). This is the region of Cell #3 over which the relocated inlet is expected to
fluctuate. Post-construction inlet migration rates for the relocated inlet are anticipated to be
on the order of 100 to 150 ft/yr (ATM and LMG, 2000). Under typical conditions, the inlet
should not move beyond the 1,000 ft corridor during the projected 4 to 5-year maintenance
interval. The inlet's north channel bank is not expected to migrate south of the 1,000 ft inlet
corridor boundary (i.e. inlet corridor is a 1,000 ft segment of barrier island purchased in fee
simple title by the County) prior to channel and basin shoaling exceeding a minimum of
300,000 CY. However, if this situation occurs, remedial actions will be triggered to conduct
maintenance dredging that would position the inlet back along the north boundary of the
inlet corridor. Additional actions, if necessary, would be conducted based on the actual
migration rate and information and data collected for the inlet monitoring program to
measure the sand movement adjacent to the inlet.
•
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i 3.4 Maintenance and Remedial Actions
Determination of who will make the final decision that remediation of project impacts on
adjacent shorelines "that are clearly attributable to the inlet" will be implemented will be
based on the findings of the Project Monitoring Reports. These reports will analyze the data
collected to determine if exceedance of the threshold triggers for two consecutive years
occurs. If these sand losses occur for a shoreline segment over a one year period, the
reports will identify this situation and the subject shoreline segment will be closely monitored
to determine if the problem persists, thereby triggering corrective, remediation actions. The
qualifying statement "clearly attributable to the inlet" is intended to preclude extreme storm
impacts or unforeseen activities associated with other Projects from triggering a remediation
action unless these losses are clearly attributable to the inlet. The special conditions of the
final permit may address this matter if the USCOE deems this is necessary. However, the
extensive monitoring and reporting will provide the high quality data and information
necessary to make such a determination by all entities having jurisdiction over this Project,
including New Hanover County, the USCOE and the State of North Carolina.
• Should any one of the triggers described above be exceeded along the project area or
adjacent beach segment(s) control volume cells for two consecutive years, that is clearly
attributable to the inlet, the County will initiate a series of corrective actions within 18 months
to restore the sediment deficit to the impacted area. As mentioned previously, storm
impacts to area-wide beaches will be evaluated on a case-by-case basis, in order to
determine the net impact of the storm versus any impacts directly attributable to the inlet
relocation. Proposed corrective actions are described in the Section 4.0.
4.0 Mason Inlet Management Plan
4.1 Plan Elements
Principal elements of the Inlet Management Plan for Mason Inlet are described according to
the type of work, including (a) periodic maintenance to dredge the inlet channel or
sedimentation basin and, or (b) dredging to place sand on adjacent beaches for amelioration
of sand losses exceeding "thresholds" of impact.
•
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• Continuous periodic maintenance of the inlet channel and the sedimentation basin to i
maintain the location of the inlet within the inlet corridor with sand placement on the
adjacent beaches extending 2 miles north and 2 miles south of the inlet;
• Dredging and beach disposal of material located within Mason Creek to reduce the
potential for future shoaling at the AIWW (as a work item during the County's
scheduled periodic maintenance of the inlet channel) to reduce tendencies for the
inlet to migrate south;
• Beachfill placement to ameliorate for sand losses that are inlet-related and exceed
established sand loss thresholds to maintain adjacent beach widths; and
Implementation of activities identified above, will be in accordance with the thresholds and
triggers established for the Project, and described in Section 3.3 of this Plan. The level of
County funding shall be in accordance with the activity to be conducted and the provisions
of the Inlet Management Plan. This Plan is based on the supporting data contained herein
and each activity is subject to future update based on evaluations of the data collected for ,
the monitoring program. Nothing in this Plan precludes the evaluation and potential
adoption of modifications or alternative maintenance strategies for management at Mason
Inlet provided that such changes are adopted by the County and approved by the USCOE
and NCDCM through their permit authorization process.
Maintenance Element
The recommended maintenance elements of the Plan are based on the need to maintain
the inlet within the inlet corridor, implement the most cost-effective schedule of routine
dredging and ameliorate quantifiable adverse inlet impacts on adjacent beaches. Erosion
problems that may occur due to the inlet's sink effects on sediments entering the inlet's
shoal system will be mitigated by the placement of beach quality sand on the effected
shoreline.
These periodic maintenance events will provide for an estimated 375,000 cubic yards of
dredging with beach placement of sand on a 5-year interval. The project costs for the
Mason Inlet Project were calculated over a 30-year project horizon and reduced to present
value. To reduce the annual value of net present values, we utilized a "corrected" interest
GNV/2000/Reports/99265-Final EA/InletMgmtPlan6/16/04 34

;~ rate. At the present time, the typical interest rate for bonds is seven (7) percent. This
seven (7) percent rate is then reduced to account for the impact of future inflation. The rate
of inflation has varied from 1.9 to 2.1 percent over the past year, therefore we have
assumed an average rate of inflation of two (2) percent. In effect, the real discount rate is
thereby five (5) percent.
The results of the analysis of project costs over a 30-year period were computed using a
discount rate of five (5) percent and a maintenance interval of 5 years. On the basis of
these calculations, the net present value of the Mason Inlet project over a 30-year horizon is
estimated at $16,543,500. An estimate of these costs over a 30-year period, including the
initial construction costs, the costs of design, engineering and project monitoring is
summarized in Table 4-1.
To evaluate the cost of inlet related maintenance on a more frequent interval, i.e. fora 3
year frequency of inlet dredging, an alternative analysis of the project costs over a 30-year
period were computed using a five (5) percent rate of interest and a maintenance interval of
3 years. On the basis of these calculations, the net present value of the Mason Inlet project
over a 30-year period is estimated at $23,275,000 as summarized in Table 4-2. This cost
basis may be unduly conservative as it assumes, AIWW maintenance dredging at the
USCOE maximum shoaling rate in the late 1980s and a fixed, 3-year inlet channel and
sedimentation basin dredge maintenance interval. In reality, the interval will be greater
during periods of lesser storm activity and increase during other periods as is seen at
Masonboro and other maintained inlets.
Most federally sponsored projects are maintained based on 30-year agreements, where
after the conclusion of the 30-years, new agreements for continued maintenance are drafted
and authorized. Thus, the USCOE customarily utilizes a 30-year planning period for Project
Horizons in developing maintenance and project funding agreements. Thus, the County's
Agreement for maintenance of this project is for thirty years and determining the effects of
this project beyond that timeframe is outside the scope of this EA and will be evaluated in
future maintenance plans.

GNV/2000/Reports/99265-Final EA/InletMgmtPlan6/16/04 35

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Wrightsvil{e Beach Beachfill Volume = 62.5 375,000
Average Annual Shoaling Rate = 75,000
Total Loss = 375,000
Mobilization = $500,000
Unit Cost = $4.50
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Maximum Conveyance Distance = 12,000
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19-265/TBL47.WK41
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rlgure a isiana t~eacntni volume = 5u.u
Wrightsville Beach Beachfill Volume = 50.0
Average Annual Shoaling Rate = 75,000
Total Loss = 375,000
Mobilization = $500,000
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Interest Rate = 7%
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99-265/inletmgtplan/table42.wk4/kme08/22/0005:02:17 PMINLET MGT PLAN REVISED TABLE 42 {3YR MAINT) IW1E.123

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Total Project Cost $42,671,998 x23,696,880
Initial Project Cost x5,626,138
•
•
99-265finletmgtpian/table42.wk4/kme0&22/0005:02:17 PMINLET MGT PLAN REVISED TABLE 42 (3YR MAtNT) IWIE.123

•
4.2.1 Inlet Channel Maintenance and Dredging of the Sedimentation Basin
The sediment deposition rate within the sedimentation basin and the inlet channel is
estimated at 75,000 cubic yards (5 year maintenance interval) to 125,000 (3 year
maintenance interval) annually. The source of this sediment is the longshore sediment
transport moving within the adjacent beach littoral system. The tendency of the inlet to
scour and maintain a critical cross-sectional area will tend to cause these sediments to
remove deposits from the inlet channel during a typical spring-near-spring tidal cycle
resulting in net shoaling within the inlet's sedimentation basin, channels and the nearshore
ebb tidal shoal. As described in Section 3, the inlet shoaling rate following inlet relocation
will be monitored on a quarterly interval, and upon the net deposition of 375,000 cubic yards
within the sedimentation basin and inlet channel, a maintenance project will be
implemented.
The ebb tidal shoal will build over time and the shorelines on the adjacent beaches will
adjust such that the ends of the island will bend towards the inlet. This ebb tidal shoal
theoretical equilibrium volume at Captain Sam's Inlet was approximately 1.17 million cubic
yards and after 2 years, approximately 397,800 cubic yards had shoaled equal to an
average annual volume of nearly 199,000 cubic yards. It is assumed that Mason Inlet's
ebb shoal, which is of similar size with longshore transport magnitudes comparable to
Captain Sam's Inlet, will develop over a 3-8 year period. The rate of deposition will be
greater in the first 2 years following inlet relocation and gradually lessen as the shoal
reaches an equilibrium volume allowing for full sediment bypassing across the inlet.
4.2.2 Maintenance of Beaches on Figure 8 Island and Wrightsville Beach
Figure 8 Island has historically undertaken beach nourishment projects to maintain their
beaches. The Mason Inlet maintenance project will provide a supplemental source of sand
for this on-going project. It is not anticipated that these dredge quantities will serve as the
sole source of sand for their beaches, however, it will provide a significant source of sand for
future erosion control. A uniform distribution of sand placement ranging from 40-60 cubic
yards per foot of shoreline is planned for interim nourishment along a shoreline segment of
8,000 to 10,000 feet. Over time, their beaches may stabilize as the inlet shoal system
develops and the updrift impact of the inlet's historic migration on this shoreline is lessened.
GNV/2000/Reports/99265-Final EA/InletMgmtPlan6/16/04 39

Sand placement at Wrightsville Beach will be conducted as required to satisfy the S
requirements of Trigger 1 and Trigger 3. This placement will be to reduce any significant
sand losses observed along the downdrift shoreline, extending south from the closed inlet
position south. The maintenance plan objectives state that the inlet is expected to migrate
at a greatly reduced rate (50 to 100 ft per year) compared to the historic rates of 350 ft per
year or greater. The trigger for inlet maintenance is the migration of the inlet outside of the
specified inlet corridor.

GNV/2000/Reports/99265-Final EA/InletMgmtPlan6/16/04 40

References
Applied Technology and Management, Inc., 1998. "Monitoring Report: Shell Island Resort
6-Month Surveys, September 1997 to February 1998." Report submitted to NCDEHNR,
March 1998.
Applied Technology and Management, Inc., 1998. "Mason's Inlet South Channel Bank
Stabilization Project, Design Memorandum." Prepared for Shell Island Homeowners
Association.
Applied Technology and Management, Inc., 1999. "Monitoring Report: Shell Island Resort
18-Month Post-Construction Surveys, September 1997 to April 1999." Report submitted to
NCDEHNR, May 1999.
Applied Technology and Management, Inc., 1999. "Monitoring Report: Shell Island Resort
24-Month Post-Construction Surveys, September 1997 to October 1999." Report submitted
to NCDEHNR, November 1999.
Applied Technology & Management, Inc. and Applied Science Associates, Inc., 1999.
"Hydrodynamic Modeling of Mason Inlet and the Middle Sound Estuary." Report prepared
for New Hanover County, NC, October 13, 1999.
Applied Technology & Management, Inc. and LMG Group, Inc., 2000. "Environmental
Assessment, Mason Inlet Relocation Project." Report prepared for North Carolina Division
of Coastal Management and US Army Corps of Engineers, October 1999.
Brooks, W.B., 1988. "A Historic and Morphologic Study of Mason and Rich Inlets, North
Carolina." Master of Science Thesis, University of North Carolina, Wilmington, Department
of Biological Sciences.
Century/von Oesen-Consulting Engineers, 1995. "Mason Inlet Migration/Shell Island
Erosion Problem." Report for Shell Island Resort Homeowners Association.
•
GNV/2000/Reports/99265-Final EA/InletMgmtPlan6/16/04 41

Cleary, W.J. and Hosier, P.E., 1979. "Geomorphology, Washover History and Inlet
Zonation, Etc. Academic Press, New York, New York. p.237-262.
Cleary, W.J. and Hosier, P.E., 1990. "A Long Range Plan for Channel Maintenance and
Beach Restoration, Figure 8 Island, North Carolina." Report prepared for Figure "8"
Homeowners Association, Inc., May 1990.
Cleary, W.J. and Marden, T.P., 1999. "Shifting Shorelines: A Pictorial Atlas of North
Carolina Inlets." North Carolina Sea Grant, UNC-SG-99-04.
Hayes, M.O., 1994. Chapter 7: The Georgia Bight Barrier System:. in "Geology of Holocene
Barrier Island Systems" (R.A. Davis, Jr., Ed.), Springer Verlag, N.Y., pp. 233-304.
Inman D.L., and Nordstrom C.E., 1971. "On the tectonic and morphologic classification of
coasts." Journal of Geology, 79, pp. 1-21.
Langfelder, J., et. al., 1974. "Historical Review of Some of North Carolina's Coastal Inlets."
Center for Coastal Studies Report No. 74-1, North Carolina State University.
North Carolina Division of Coastal Management. 1992. "North Carolina Long-Term
Average Annual Rates of Shoreline Change," Methods Report and Maps, 1992 Update.
Overton, M.F., J.S. Fisher, W.A. Dennis, and H.C. Miller. 1992. "Shoreline Change at
Oregon Inlet Terminal Groin," in Coastal Engineering 1992, ASCE, pp. 2332-2343.
Overton, M.F. and J.S. Fisher. 1996. "Shoreline Monitoring at Oregon Inlet Terminal Groin,
Report 13 (February 11, 1996 -June 6, 1996)." Report prepared for NCDOT, NCSU
Department of Civil Engineering, 22p.
Priddy, L.J., and Carraway, R., 1978. "Inlet Hazard Areas, The Final Report and
Recommendations to the Coastal Resources Commission." Technical Services Section,
Division of Marine Fisheries, NC Department of Natural Resources and Community
Development.

GNV/2000/Reports/99265-Final EA/InletMgmtPlan6/16/04 42

Sexton, W.J., 1997. "Modern Clastic Depositional Environments Field Trip Guidebook," pp.
20-32.
U.S. Army Corps of Engineers, 1977. "General Design Memorandum, Masonboro Inlet,
North Carolina, South Jetty." US Army Corps of Engineers, Wilmington District.
U.S. Army Corps of Engineers, 1982. "Feasibility Report and Environmental Assessment,
Shore and Hurricane Wave Protection, Wrightsville Beach, North Carolina." US Army Corps
of Engineers, Wilmington District.
U.S. Army Corps of Engineers, 1997. "Draft General Reevaluation Report and
Environmental Assessment for Beach Erosion Control and Hurricane Wave Protection,
Brunswick County Beaches, North Carolina, Ocean Isle Beach Portion." Wilmington District,
South Atlantic Division.
U.S. Army Corps of Engineers, 1998. Hindcast Wave Information Studies for the period
1976-1995. Retrieved from the CERC Web Site.
US Department of Commerce, NOAA, National Ocean Service, 1996. High and Low Water
Predictions of North and South America.
Winton, T.C., Chou, I.B., Powell, G.M., and Crane, J.D. 1981. Analysis of Coastal
Sediment Transport Processes from Wrightsville Beach to Fort Fisher, North Carolina.
Prepared for the U.S. Army Corps of Engineers Coastal Engineering Research Center, Fort
Belvoir, VA. Misc. Report No. MR-81-6.

GNV/2000/Reports/99265-Final EA/InletMgmtPlan6/16/04 43

•
•

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Mason Inlet Migration 1989-1995 ~~r .n~a~',~rrrerz~i
I
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Survey Monuments and Lines ~~, ~~ -
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•
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Figure 3-1 (Sheet 2 of 3) ~y~,/
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• • •
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..WATERWAY______ _ .. ,
. _ CHANNEL
RELOCATED INLET
~~~ CORRIDOR
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(8,000') (3,700') CELL 3 N-4
(3,400') CELl2 BP_4
(3, 700')
CELL 1
(7, 000') BP- I 1
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~Z
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•
Appendix D
Hydrodynamic Model
•
-E
ENt3iNEERB tlt SURVEYORS

• Mason Inlet and Middle Sound System
New Hanover County, North Carolina
Hydrodynamic and Sediment Transport Analyses of
Present Conditions and Dredging Alternatives
by Sean W. Kelley
John S. Ramsey
Applied Coastal Research and Engineering, Inc.
766 Falmouth Road, Suite A-1
;~ Mashpee, MA 02649
,_ ;
~,~
~ - ,~,
,t ~ ~ ~ ~.
a ~ ~_ 'rs, ;r ~
j ~ -observed "~ ' •~~~ ~ ' '~~
,~
CO 2 - - computed ~~". a
/ I ,~ ~N , ~-,.
3 4 r ~ _, Mason Creek t.
50 60 70 80 90 100 ~AIM/W north i
simulation time (hr) AIWW south
_ 4 i
~ 2 ~ _
,,
c_~ ~ , U r
3 i, i i _ i ~
_4 -__- _- - -__. _ - - - _ ~ __i
40 60 80 100 120 140
simulation time (hr)
_3 ~_-. _ i _ . __ _..~_
106 112 118 124 130 136 142 148
DRAFT REPORT -OCTOBER 2003
Prepared for:
Gahagan and Bryant Associates, Inc.
GBA Wilmington, NC
• 7127 Ogden Business Lane, Unit 113
Wilmington, NC 28411

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
TABLE OF CONTENTS •
Section Page
LIST OF FIGURES .......................................................................................................... ii
LIST OF TABLES ........................................................................................................... iv
1. INTRODUCTION ........................................................................................................1
2. DATA ANALYSIS .......................................................................................................3
2.1 Bathymetry Data Collection ................................................................................3
2.2 Tide Data Collection and Analysis ......................................................................4
3. HYDRODYNAMIC MODEL DEVELOPMENT ...........................................................10
3.1 Model Theory ................................................................................................... 10
3.2 Model Setup ..................................................................................................... 10
3.2.1 Grid generation .......................................................................................... 11
3.2.2 Boundary condition specification ................................................................ 12
3.2.3 Calibration .................................................................................................. 12
3.2.3.1 Friction coefficients .............................................................................. 13
3.2.3.2 Turbulent exchange coefficients .......................................................... 14
3.2.3.3 Marsh porosity processes .................................................................... 14
3.2.3.4 Comparison of modeled tides and measured tide data ........................ 15
3.2.5 ADCP verification of the Mason Inlet system model ................................... 19
4. CIRCULATION CHARACTERISTICS AND IMPACTS OF DREDGING OPTIONS... 21
4.1 System Circulation and Residual Flows ............................................................ 22
4.1.1 Present Conditions ..................................................................................... 22
4.1.1.1 AIWW /Mason Creek Junction ............................................................ 22
4.1.1.2 Mason Inlet .......................................................................................... 25
4.1.2 Dredging Options ...................................................................................•-.. 25
4.2 Tidal Currents and Residual Velocities ............................................................. 26
4.2.1 Flow Patterns of Present Conditions .......................................................... 27
4.2.2 Channel Characteristic Tidal Dominance for Present conditions ................ 27
4.2.4 Dredging Options ....................................................................................... 31
5. SEDIMENT TRANSPORT MODELING .................................................................... 34
5.1 Present Conditions ...........................................................................................34
5.2 Modeled Dredging Scenarios ...........................................................................36
6. CONCLUSIONS .......................................................................................................42
7. REFERENCES .........................................................................................................44

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
LIST OF FIGURES
Figure
Page
Figure 1-1. Topographic map detail of the Mason Inlet System, in New Hanover
County, North Carolina. This map shows the past configuation of the
inlet, prior to the dredging of Mason Creek and relocation of the Inlet
approximately 3000 ft to the northeast .....................................................2
Figure 2-1. Aerial photograph (credit GBA, 2003) .......................................................3
Figure 2-2. Plot of interpolated finite-element grid bathymetry of the Mason Creek
system, shown superimposed on 2003 aerial photos of the system locale.
Bathymetric contours are shown in color at one-foot intervals ..................4
Figure 2-3. Plot showing two tide cycles tides at three stations in the Mason Creek
system plotted together. Demonstrated in this plot is the tidal phase and
amplitude differences across the system. The time lag of low tide from
the offshore gauge and the gauge located at the Figure Eight Island
bridge, from this plot, is 58 minutes ..........................................................5
Figure 2-4. Example of an observed astronomical tide as the sum of its primary
constituents .............................................................................................. 6
Figure 2-5. Plot showing the comparison between the measured tide time series (top
plot), and the predicted astronomical tide (middle plot) computed using
the 23 individual tide constituents determine in the harmonic analysis of
the Mason Inlet gauge data. The residual tide shown in the bottom plot is
computed as the difference between the measured and predicted time
series (r=m-p) ...........................................................................................9
Figure 3-1. Detail of the completed finite element mesh for the Mason Inlet system,
showing mesh structure and color shaded bathymetric contours............11
Figure 3-2. Detail of finite element grid of Mason Inlet, showing material-type divisions
used to vary bottom friction and eddy viscosity model coefficients across
the model domain ...................................................................................14
Figure 3-3. Comparison of model output and measured tides for the tide gauge
location offshore Mason Inlet (M4, Figure 2-1 ). The top plot is a 50-hour
sub-section of the total modeled time period, shown in the bottom plot..16
Figure 3-4. Comparison of model output and measured tides for the tide gauge
location inside Mason Inlet (M5, Figure 2-1 ). The top plot is a 50-hour
sub-section of the total modeled time period, shown in the bottom plot..16
Figure 3-5. Comparison of model output and measured tides for the tide gauge
location at the Mason Creek/ AIWW junction (M2, Figure 2-1 ). The top
plot is a 50-hour sub-section of the total modeled time period, shown in
the bottom plot .......................................................................................17
Figure 3-6. Comparison of model output and measured tides for the tide gauge
location at the Lollipop Bay/ AIWW junction (M1, Figure 2-1 ). The top plot
is a 50-hour sub-section of the total modeled time period, shown in the
bottom plot .............................................................................................17

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
Figure 3-7. Comparison of model output and measured tides for the tide gauge
location at the Figure Eight Island bridge/AIWW junction (M3, Figure 2-
1). The top plot is a 50-hour sub-section of the total modeled time period,
shown in the bottom plot ........................................................................18
Figure 3-8. Comparison of model output and measured tides for the tide gauge
location in the Banks Channel (M6, Figure 2-1 ). The top plot is a 50-hour
sub-section of the total modeled time period, shown in the bottom plot..18
Figure 3-9. Comparison of measured volume flow rates versus modeled flow rates
(top plot) through West Bay Inlet over a flood tidal on July 8, 2003. Flood
flows into the inlet are positive (+), and ebb flows out of the inlet are
negative ~ ). The bottom plot shows the tide elevation offshore Dead
Neck. (R =0.87, error~ms 11.5%) ...........................................................20
Figure 4-1. Planned dredging scenarios modeled for Mason Inlet. All options included
the dredging of Mason Creek (yellow area) ............................................21
Figure 4-2. Location of channel transects used to compute total Flood and Ebb flow
volumes, and resulting flow residuals (Table 4-1 ), at the junction of the
AIWW and Mason Creek ............................•-•---....-----•------------................23
Figure 4-3. Location of channel transects used to compute total Flood and Ebb flow
volumes, and resulting flow residuals (Table 4-2), at the junction of Mason
Creek and Banks Channel at Mason Inlet ..............................................24
Figure 4-4. Comparison of inlet cross-sections for present conditions (solid line) and
Option A dredge plan (dot-dashed line). Inlet areas were calculated
~~
based on the mean tide level (MTL), which corresponds to 0.0 ft NGVD at
the inlet ..................................................................................................25
Figure 4-6. Example of model output for the Mason Inlet system, for a single time step
where maximum flood velocities occur for this tide cycle. Color contours
indicate velocity magnitude, and vectors indicate the direction of flow....28
Figure 4-7. Example of model output for the Mason Inlet system, for a single time step
where maximum flood velocities occur for this tide cycle. Color contours
indicate velocity magnitude, and vectors indicate the direction of flow....28
Figure 4-8. Time series plot of tidal velocities for channels at Mason Inlet. Positive (+)
velocities are for flooding tides, and negative (-) velocities are for ebbing
tides ....................................................................................................... 29
Figure 4-9. Time series plot of tidal velocities for channels at the junction of Mason
Creek and the AIWW. Positive (+) velocities are for flooding tides, and
negative (-) velocities are for ebbing tides. The AIWW floods to the
northeast and ebbs to the southwest ......................................................29
Figure 4-10. Peak flood and ebb tide, mid-channel, depth-averaged velocities (ft/sec)
in the Mason Inlet system. Velocities are from the 7-day model simulation
of existing conditions. Blue arrows indicate ebbing peak velocities, and
red arrows indicate flooding peaks .........................................................30
Figure 5-1. Bathymetric change in the Mason Inlet system, between July 2002 and
July 2003. Areas of erosion are shaded from gray to red, and deposition
is indicated by colors from gray to dark green. Grid coordinates are NC
state plane, feet ......................................................................................35

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
Figure 5-2. Modeled erosion/deposition potential using July 2002 bathymetry. Red
areas indicate erosional potential, while green areas indicate depositional
potential ................................................................................................. 35
Figure 5-3. Modeled erosion/deposition potential for present 2003 conditions. Red
areas indicate erosional potential, while green areas indicate depositional
potential . ................................................................................................37
Figure 5-4. Average modeled bottom shear stress for present (2003) conditions......37
Figure 5-5. Modeled erosion/deposition potential for Option A dredging plan. Red
areas indicate erosional potential, while green areas indicate depositional
potential. Black-dotted outline indicated the areas to be dredged..........38
Figure 5-6. Average modeled bottom shear stress for Option A dredge plan. Black-
dotted outline indicated the areas to be dredged ....................................38
Figure 5-7. Modeled erosion/deposition potential for Option B dredging plan. Red
areas indicate erosional potential, while green areas indicate depositional
potential. Black-dotted outline indicated the areas to be dredged..........40
Figure 5-8. Average modeled bottom shear stress for Option B dredge plan. Black-
dotted outline indicated the areas to be dredged ....................................40
Figure 5-9. Modeled erosion/deposition potential for Option C dredging plan. Red
areas indicate erosional potential, while green areas indicate depositional
potential. Black-dotted outline indicated the areas to be dredged..........41
Figure 5-10. Average modeled bottom shear stress for Option C dredge plan. Black-
dotted outline indicated the areas to be dredged ....................................41
LIST OF TABLES
Table Page
Table 2-1. Tide datums computed from data records collected offshore Mason Creek,
in the AIWW at Lollipop Bay and the Figure Eight Island bridge, and in the
Banks Channel (June 24, 2003 and August 13, 2003 deployment).
Datum elevations are given relative to NGVD 29 ......................................6
Table 2-2. Major tidal constituents determined for gauge locations in the Mason Inlet
system, June 27 through August 05, 2003 ...............................................6
Table 2-3. M2 tidal constituent phase delay (relative to tides immediately offshore
Mason Inlet) for gauge locations in the Mason Inlet system, determine
from measured tide data ..........................................................................7
Table 2-4. Percentages of Tidal versus Non-Tidal Energy for the Mason Inlet system,
June to August 2003 ................................................................................8
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Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
Table 3-1. Manning's Roughness coefficients used in simulations of modeled
embayments. These embayment delineations correspond to the material
type areas shown in Figure 3-2 ..............................................................13
Table 4-1. Average total flood and ebb tide flow volumes, and resulting flow
residuals, at model transects at the junction of Mason Creek and the
AIWW, for present conditions and three modeled dredging options. The
AIWW floods to the NE and ebbs to the SW. Positive (+) residuals
indicate larger flood volume; negative (-) residuals indicate larger ebb
volume. Tide volumes were computed based on a 14 tide cycle
simulation. All volumes are given in cubic feet per tide cycle (ft3/tide)....23
Table 4-2. Average total flood and ebb tide flow volumes, and resulting flow
residuals, at model transects at Mason Inlet, and the junction of Mason
Creek and the Banks Channel, for present conditions and three modeled
dredging options. Positive (+) residuals indicate larger flood volume;
negative (-) residuals indicate larger ebb volume. Tide volumes were
computed based on a 14 tide cycle simulation. All volumes are given in
cubic feet per tide cycle (ft3/tide) .............................................................24
Table 4-3. Present Conditions: Relative velocity phase difference of M2 and M4 tide
constituents, determines using velocity records output from computer
model simulation of 14 tide cycles ..........................................................30
Table 4-4. Peaks mid-channel, depth-averaged velocities for channels in the Mason
Inlet system. Results from model output of present conditions and three
dredging options are given. All velocities are in ft/sec ...........................31
Table 4-5. Option A: Relative velocity phase difference of M2 and M4 tide
constituents, determines using velocity records output from computer
model simulation of 14 tide cycles ..........................................................31
Table 4-6. Option B: Relative velocity phase difference of M2 and M4 tide
constituents, determines using velocity records output from computer
model simulation of 14 tide cycles ..........................................................32
Table 4-7. Option C: Relative velocity phase difference of M2 and M4 tide
constituents, determines using velocity records output from computer
model simulation of 14 tide cycles ..........................................................32
v

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
1. INTRODUCTION
The Mason Inlet system is located northeast of Wrightsville Beach, NC, in New
Hanover County (Figure 1-1 ). Due to southerly migration of the inlet channel on erosion
impacts to adjacent properties, a plan was developed to relocate the inlet approximately
3,000 feet northeast of its 2001 location, and to re-open a connection between the inlet
and the Atlantic Intracoastal Waterway (AIWW), known as Mason Creek. Following the
Mason Inlet relocation, completed in March 2002, rapid infilling of the impoundment
basin and shoaling within the AIWW at the junction with Mason Creek have generated
concerns regarding performance of the modified inlet system. Specifically, future
management of sediments within the inlet complex needs to be addressed to ensure that
dredging efforts do not exacerbate shoaling in navigation channels. In addition, an
evaluation of shoaling patterns following the relocation of Mason Inlet can be utilized (a)
to understand processes governing these shoaling patterns and (b) to predict future
sediment transport patterns.
Hydrodynamic and sediment transport models are often used as predictive tools
to quantitatively assess sediment transport patterns. within a given tidal inlet complex.
For the case of Mason Inlet, a hydrodynamic model can be developed based on existing
topography/bathymetry, as well as coincident tidal records at key locations within the
estuarine system. Since a substantial data set exists regarding bathymetric change
between the relocation of the inlet and July 2003, sufficient information exists to ground-
truth asediment transport model. Therefore, a combined hydrodynamic and sediment
transport model can provide a deterministic tool for evaluating alternative inlet
geometries.
A two-dimensional (depth-averaged) hydrodynamic and sediment transport
modeling analysis was performed for the Mason Inlet system. The topographic map
detail shown in Figure 1-1 shows the general study area, prior to the inlet relocation. The
Mason Creek system, as modeled, has three main channels: 1) the AIWW; 2) Mason
Creek, the new channel between the inlet and the AIWW; and 3) the Banks Channel,
which was previously the main channel between the Inlet and AIWW before the
relocation of the inlet. The study area contains extensive marsh resources throughout
the area called Middle Sound. Circulation in the Mason Creek system is dominated by
tidal exchange with the Atlantic Ocean and the AIWW.
The entire Mason Creek study area covers approximately 2,150 acres, of which
1,300 acres are marsh. The elevation of the marsh plain is typically between 2.2 and 2.4
ft NGVD, which corresponds roughly to the level of the mean high water (MHW) tide
elevation for this region.
As stated above, the evaluation of inlet/estuarine processes proceeded as two
component efforts. The first portion of the study focused on the development of a
numerical hydrodynamic model of the Mason Creek system. Using bathymetry survey
data made available by Gahagan & Bryant Associates (GBA), a model grid was
generated for use with the RMA-2 hydrodynamic code. Tide data collected by GBA at
six gauging stations located within the study area were used to provide open boundary
time series required to run the RMA-2 model, and also provide calibration data at critical
portions of the modeled domain. Additionally, measured Acoustic Doppler Current
Profiler (ADCP) data collected at the Inlet (Welsh, 2003) were used to verify calibrated
model performance. The model calibration and verification process is intended to ensure

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
that the completed model accurately represents the dynamics of the real, physical
system.
The calibrated computer model of the Mason Creek system was used as the
basis of the second component to this study, namely the analysis of current and flow
patterns throughout the system, and additional sediment transport modeling for present
conditions and three inlet dredging alternatives. As part of the sediment transport
analysis, bathymetric change results from July 2002 to July 2003 were compared with
model-predicted bathymetric change trends. Good agreement between modeled and
measured shoaling patterns is an indication that the model is parameterized properly
and sediment sources are largely derived from within the model domain. Once the
model has been "calibrated" to existing sediment transport trends, alterations to
sediment transport patterns can be determined for each of the specified alternatives.
Results of these analyses provide insight into the physical processes of the system
which effect channel shoaling and stability (for present conditions, as well as for each of
the modeled alternatives).
s .,~ ~, ~- ~ ~.~ -~ , ~.,
~ ~
~T`,~. ~ ~ a !' i r
1 ~ ,_ j f
~~ ~ 6 .~ 't ~ ~~ ~ Y 1 ~~
t ~ i
r ~ ~ -~' . ,. ~ ~ -„ ~j I
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`~ k f ~
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f }('f
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i / i ~ 1 _ r _
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:~ . sb ~ +~' ~~
1.~..,i ~, ~ ~ sa ,'F
Figure 1-1. Topographic map detail of the Mason Inlet System, in New Hanover County, North
Carolina. This map shows the past configuation of the inlet, prior to the dredging of
Mason Creek and relocation of the Inlet approximately 3000 ft to the northeast.
2

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
2. DATA ANALYSIS
The field data collection was performed by GBA. Field data are required to
properly characterize the physical properties of the Mason Creek estuary. Bathymetric
measurements were collected throughout the system so that the complex network of
channels could be represented accurately within the hydrodynamic model, the basis for
the dredging alternatives analysis. Tide data were also collected, at six locations, as part
of the field data collection effort. The tide data were used to force the circulation model
from the Atlantic Ocean and at two locations within the AIWW, as well as to calibrate its
performance. In addition to bathymetry and tide data collected by GBA, ADCP flow data
collected at the inlet, by the University if North Carolina at Wilmington (UNCW) Center
for Marine Science (Welsh, 2003), was used to verify the performance of the calibrated
model.
2.1 Bathymetry Data Collection

~ ~~ ~. fl ~~~`` . y
~ ~'
..:.'~.
~r, ~ x~
~'~' 1 ~ ~ ,,,,
,'~ w ,/~
Bathymetry data used for the development of the hydrodynamic model were
collected during the period between April and July 2003. The actual survey transects
are shown in Figure 2-1. The resulting bathymetric surface created by interpolating the
data to the finite element mesh of the Mason Creek system is shown in Figure 2-2. All
bathymetry provided by GBA was tide corrected, and referenced to the National
Geodetic Vertical Datum of 1929 (NGVD 29),
Figure 2-1
Aerial photograph (credit GBA, 2003)
3

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
~ ~~ ~~
~y :~~ ~~
~- k 7 1 ~~ t F~~
!T.
~y ~,.q ~
'_@~,'
_.~
x~ Y
€ f ~.
w.' r :.
vY,
54 r.
~~ ~ ~
s~i~s !
:..~:'
W~
'i1~
-1©.1~
-~~.~
Ad.~
-16.~
Figure 2-2. Plot of interpolated finite-element grid bathymetry of the Mason Creek system,
shown superimposed on 2003 aerial photos of the system locale. Bathymetric
contours are shown in color at one-foot intervals
2.2 Tide Data Collection and Analysis
Tide data records used in this study were collected at six stations in the Mason
Creek estuary system: 1) offshore Mason Inlet (M4), 2) Mason Inlet (M5), 3)
AIWW/Mason Creek junction (M2), 4) Banks Channel (M6), 5) Figure Eight Island Bridge
(M3), and 6) AIWW/Lollipop Bay junction (M1). The locations of the stations are shown
in Figure 2-1. The gauges used to record the tide data were deployed between June 24,
2003 and August 13, 2003. All gauges were deployed longer than the 29-day minimum
required to record the monthly maximum and minimum astronomical tide ranges, and
also to provide a record of sufficient length to perform a harmonic analysis to determine
the 23 main tidal constituents at the gauge locations. The elevation of each gauge was
surveyed relative to NGVD 29. Data from the offshore record and from the AIWW at
Lollipop Bay and the Figure Eight Island Bridge were used to develop the three open
boundary conditions of the hydrodynamic model. Data from the other three locations
were used to calibrate the model.
The tides the Mason Creek system are semi-diurnal, meaning that there are
typically two complete tide cycles in a day. Plots of tide data from three representative
gauges are shown in Figure 2-3, for approximately two 12.4-hour tide cycles, near the
'ZY'
'~
~.<,.
} z
•

s
4

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
spring tide maximum (full moon occurred July 13, 2003). This plot demonstrates the
slight variation in the time and elevation of the high and low tides at these three stations.
These tidal phase (delay) differences provide potential for flow through the Mason Creek
system, in addition to the potential supplied by the rise and fall of the tide offshore.
c~
z
~ 1
c
0
.~
m 0
a~
m
~ -1
m
-2
-3
Jul-1012h Jul-1018h Jul-1100h Jul-1106h Jul-11012h
Eastern Standard Time, July 10 and 11, 2003
Figure 2-3. Plot showing two tide cycles tides at three stations in the Mason Creek system
plotted together. Demonstrated in this plot is the tidal phase and amplitude
differences across the system. The time lag of low tide from the offshore gauge
and the gauge located at the Figure Eight Island bridge, from this plot, is 58
minutes.
Standard tide datums were computed from the tide records. These datums are
presented in Table 2-1. For most NOAA tide stations, these datums are computed using
19 years of tide data, the definition of a tidal epoch. For this study, a significantly shorter
time span of data was available, however, these datums still provide a useful
comparison of tidal dynamics within the system. The Mean Higher High (MHH) and
Mean Lower Low (MLL) levels represent the mean of the daily highest and lowest water
levels, respectively. The Mean High Water (MHW) and Mean Low Water (MLW) levels
represent the mean of all the high and low tides of a record. The Mean Tide Level (MTL)
is simply the mean of MHW and MLW. The MTL, MLW and MLLW levels at the Figure
Eight Bridge gauge show that there is significant attenuation of the tide to the north of
the bridge. The cause of the attenuation is less efficient tidal exchange in the AIWW to
the north of Figure Eight Island bridge, e.g. at Rich Inlet.
In addition to computing the standard tide datums, a more thorough harmonic
analysis of the six tidal data sets was performed to produce the tidal amplitude and
phase of the major tidal constituents. This analysis also yielded a quantitative
assessment of the relative influence of non-tidal, or residual, processes (such as wind
forcing) on the hydrodynamics of the system. Harmonic analysis is a mathematical
procedure that fits sinusoidal functions of known frequency to the measured signal. The
observed astronomical tide is therefore the sum of several individual tidal constituents,
with a particular amplitude and frequency. For demonstration purposes a graphical
5

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
example of how tidal constituents add together is shown in Figure 2-4, where the
observed tide is equal to the superposition of the various constituent curves shown. The
amplitudes and phase of 23 known tidal constituents result from this procedure. Table
2-2 presents the amplitudes of eight tidal constituents at the six gauge stations in the
Mason Creek system.
Table 2-1. Tide datums computed from data records collected offshore Mason
Creek, in the AIWW at Lollipop Bay and the Figure Eight Island bridge, and in the
Banks Channel (June 24, 2003 and August 13, 2003 deployment). Datum elevations
are iven relative to NGVD 29.
Figure AIWW/

Offshore Lollipop
Eight Island Mason Banks
Tide Datum
(M4) Bay/ Creek Channel
AIWW (M1) AIWW (M3) Junction (M6)
M2
Maximum Tide 3.4 3.1 3.0 3.2 3.1
MHHW 2.5 2.4 2.3 2.4 2.3
MHW 2.0 2.0 1.9 1.9 1.9
MTL 0.0 0.0 0.1 0.1 0.0
MLW -2.0 -1.9 -1.7 -1.7 -1.9
MLLW -2.2 -2.1 -1.9 -2.0 -2.1
Minimum Tide -3.1 -3.0 -2.7 -3.2 -2.7
3
Z
1
E
,`o_ 0
w
-1
_2
-3
-Observed Tide
- M2 constituent
~~~~~~~~ M4 constituent
- K1 constituent
-- N2 constituent
0 6 12 18 24
Time (hour)
Figure 2-4. Example of an observed astronomical tide as the sum of its primary constituents.
Table 2-2. Major tidal constituents determined for gauge locations in the Mason Inlet system,
June 27 throu h Au ust 05, 2003.
Am l itude feet
Constituent M2 M4 Ms S2 N2 K, O, Msf
Period hours 12.42 6.21 4.14 12.00 12.66 23.93 25.82 354.61
Offshore Mason Inlet 1.91 0.05 0.03 0.20 0.41 0.43 0.25 0.19
Mason Inlet 1.84 0.04 0.04 0.16 0.39 0.43 0.25 0.21
Mason Creek/AIWW Junction 1.78 0.04 0.06 0.16 0.36 0.42 0.27 0.20
Lollipop Bay (AIWW) 1.82 0.03 0.06 0.18 0.37 0.43 0.25 0.20
Figure Eight Bridge (AIWW) 1.68 0.06 0.08 0.15 0.32 0.41 0.27 0.21
Banks Channel 1.74 0.08 0.08 0.16 0.33 0.40 0.28 0.20
•
6

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003

The M2, or the familiar twice-a-day lunar semi-diurnal tide, is the strongest
contributor to the signal with an offshore amplitude of 1.9 ft. The total range of the MZ
tide is twice the amplitude, or 3.8 ft. The M4 and M6 tides are higher frequency
harmonics of the M2 lunar tide (exactly half the period of the M2 for the M4, and one third
of the M2 period for the M6), and result from frictional attenuation of the M2 tide in shallow
water. The M4 and M6 both have very small amplitudes throughout the system (less than
0.1 feet). Aside from the minor growth observed in the M4 constituent amplitude in the
Banks channel data, tidal energy losses and transfers in the system are difficult to
characterize (other than their magnitudes) due to complications associated with the
north and south AIWW connections in the study area.
The other major tide constituents show little variation across the system. The
diurnal tides (once daily), K~ and O,, possess amplitudes of approximately 0.4 feet and
0.3 feet respectively. Other semi-diurnal tides, the S2 (12.00 hour period) and N2 (12.66-
hour period) tides, contribute significantly to the total tide signal, with offshore amplitudes
of 0.2 feet and 0.4 feet, respectively. The Msf is a lunarsolar fortnightly constituent with a
period of approximately 14 days, and is the result of the periodic conjunction of the sun
and moon. The Msf has an amplitude of 0.2 ft.
Along with the variation in constituent amplitudes throughout the system, the
phase change of the tide is seen from the results of the harmonic analysis. Table 2-3
shows the delay of the M2 at different points in the Mason Creek system, relative to the
timing of the MZ constituent offshore Mason Inlet. The greatest delay is at the Banks
Channel gauge station, which also showed the largest reduction of the M2 amplitude
(Table 2-2). Compared to other locations instrumented in this study, the Banks channel
shows the greatest tidal attenuation compared to the tide offshore.
Table 2-3. MZ tidal constituent phase delay
(relative to tides immediately offshore Mason
Inlet) for gauge locations in the Mason Inlet
s stem, determine from measured tide data.
Station Delay
minutes
Mason Inlet 20.0
Mason Creek/AIWW Junction 46.6
Lolli o AIWW 34.9
Fi ure Ei ht Brid a AIWW 58.5
Banks Channel 62.9
In addition to the harmonic analysis, the tide data were further evaluated to
determine the importance of tidal versus non-tidal processes to changes in water surface
elevation. These other processes include wind forcing (set-up or set-down) within the
estuary, as well as sub-tidal oscillations of the sea surface (e.g., caused by large scale
weather systems). Variations in water surface elevation can also be affected by
freshwater discharge into the system, if these volumes are relatively large compared to
tidal flow.

7

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
The results of the analysis to determine the energy distribution (or variance) of
the original water elevation time series for the Mason Creek system is presented in
Table 2-4, and is compared to the energy content of the astronomical tidal signal (re-
created by summing the contributions from the 23 constituents determined from the
harmonic analysis). Subtracting the tidal signal from the original elevation time series
(measured data) resulted with the non-tidal, or residual, portion of the water elevation
changes. The energy of this non-tidal signal is compared to the tidal signal, and yields a
quantitative measure of how important these non-tidal physical processes can be to
hydrodynamic circulation within the estuary. Figure 2-5 shows the comparison of the
measured tide from inside Mason Inlet, with the computed astronomical tide resulting
from the harmonic analysis, and the resulting non-tidal residual. The tidal residual is
seen to be generally less than 0.5 ft throughout the deployment period, shown in this
figure.
Table 2-4 shows that there is a reduction in tidal energy in areas farther from the
inlet. This is another indication of the tidal attenuation through the system. The analysis
also shows that tidal processes are responsible for approximately 98% of the water level
changes in the Mason Creek system. The remaining 2% was the result of atmospheric
forcing, due to winds or barometric pressure gradients. The small contribution of the
residual to the complete tide signal provides confidence that the system can be
adequately modeled using tide data time series.
Table 2-4. Percentages of Tidal versus Non-Tidal Energy for the Mason Inlet
s stem, June to Au ust 2003.

TDR Location Total Variance
2 Tidal
Non-tidal (%)
ft
•sec %
Offshore Mason Inlet 2.070 97.8 2.2
Mason Inlet 1.917 97.9 2.1
Mason Creek/AIWW Junction 1.808 97.7 2.3
Lollipop (AIWW) 1.893 97.9 2.1
Figure Eight Bridge (AIWW) 1.621 97.4 2.6
Banks Channel 1.737 97.6 2.4
8

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
•
•
•
Measured Tide
Jul-1 Jul-7 Jul-14 Jul-21 Jul-28 Aug-1
Predicted Tide
Jul-1 Jul-7 Jul-14 Jul-21 Jul-28 Aug-1
Residual Tide
Jul-1 Jul-7 Jul-14 Jul-21 Jul-28 Aug-1
date, 2003
Figure 2-5. Plot showing the comparison between the measured tide time series (top plot), and
the predicted astronomical tide (middle plot) computed using the 23 individual tide
constituents determine in the harmonic analysis of the Mason Inlet gauge data. The
residual tide shown in the bottom plot is computed as the difference between the
measured and predicted time series (r=m-p).
4
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't
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~_
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°~ -1
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~_
~° -2
9

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
3. HYDRODYNAMIC MODEL DEVELOPMENT
For modeling the Mason Inlet system, Applied Coastal utilized astate-of-the-art
computer model to evaluate tidal circulation. The particular model employed was the
RMA-2 model developed by Resource Management Associates (King, 1990). It is a two-
dimensional, depth-averaged finite element model, capable of simulating transient
hydrodynamics. The model is widely accepted and tested for analyses of estuaries or
rivers. Applied Coastal staff members have utilized RMA-2 for numerous hydrodynamic
studies including aTown-wide study of five estuary systems within Chatham, MA
(Kelley, et al, 2001), a marsh habitat reclamation project in Chesapeake Bay (Ramsey
and Ruthven, 2003), and a flushing analysis in the AIWW, in the Indian River of Martin
County, FL (Ramsey, 2002).
3.1 Model Theory
In its original form, William Norton and Ian King developed RMA-2 under contract
with the U.S. Army Corps of Engineers (Norton et al., 1973). Further development
included the introduction of one-dimensional elements, state-of-the-art pre- and post-
processing data programs, and the use of elements with curved borders. Recently, the
graphic pre- and post-processing routines were updated by a Brigham Young University
through a package called the Surfacewater Modeling System or SMS (BYU, 1998).
Graphics generated in support of this report primarily were generated within the SMS
modeling package.
RMA-2 is a finite element model designed for simulating one- and two-
dimensional depth-averaged hydrodynamic systems. The dependent variables are
velocity and water depth, and the equations solved are the depth-averaged Navier
Stokes equations. Reynolds assumptions are incorporated as an eddy viscosity effect to
represent turbulent energy losses. Other terms in the governing equations permit friction
losses (approximated either by a Chezy or Manning formulation), Coriolis effects, and
surface wind stresses. All the coefficients associated with these terms may vary from
element to element. The model utilizes quadrilaterals and triangles to represent the
prototype system. Element boundaries may either be curved or straight.
The time dependence of the governing equations is incorporated within the
solution technique needed to solve the set of simultaneous equations. This technique is
implicit; therefore, unconditionally stable. Once the equations are solved, corrections to
the initial estimate of velocity and water elevation are employed, and the equations are
re-solved until the convergence criteria is met.
3.2 Model Setup
There are three main steps required to implement RMA-2:
Grid generation
Boundary condition specification
Calibration

The extent of each finite element grid was generated using a 2003 digital aerial
photograph of the Middle Sound/Mason Creek region, provided by GBA. Atime-varying
10

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
water surface elevation boundary condition (measured tide) was specified at the offshore
boundary of the grid at Mason Inlet, and at the AIWW southwestern and northeastern
limits in the model domain, at Lollipop Bay and the Figure Eight Island bridge,
respectively. The tidal boundary conditions were based on tide gauge data. Once the
grid and boundary conditions were set, the model was calibrated to ensure accurate
predictions of tidal dynamic within the model. Various friction and eddy viscosity
coefficients were adjusted, through several (20+) model calibration simulations for each
system, to obtain agreement between measured and modeled tides. The calibrated
hydrodynamic model provides the basis for the analysis of sediment transport patterns in
the system, and the evaluation of selected dredging scenarios for the inlet system.
3.2.1 Grid generation
The grid generation process was aided by the use of the SMS package. The
2003 digital composite aerial photograph and recent bathymetry survey data were
imported to SMS, and a finite element grid was created to represent the Mason Inlet
estuary. The aerial photographs were used to determine the land boundary of the
modeled domain. Bathymetry data were interpolated to the developed finite element
mesh of the system. The completed grid consists of 7,487 nodes, which describe 3,124
total 2-dimensional (depth-averaged) quadratic elements, and covers 2,150 acres. The
maximum nodal depth is -31 ft (NGVD 29), at the offshore open boundary of the grid.
Maximum channel depths within the grid typically range between -10 ft in the Inlet and
Mason Creek and -17 ft in the AIWW. A close-up of the completed inlet system mesh
is shown in Figure 3-1.

Figure 3-1. Detail of the completed finite element mesh for the Mason Inlet system, showing
mesh structure and color shaded bathymetric contours.
11

implied Coastal Research and Engineering, Inc. Mason Inlet, 2003
The finite element grid for the system provided the detail necessary to evaluate
accurately the variation in hydrodynamic properties throughout the modeled Mason Inlet
area. The SMS grid generation program was used to develop quadrilateral and
triangular two-dimensional elements throughout the estuary. Grid resolution was
governed by two factors: 1) expected flow patterns, and 2) the bathymetric variability of
the system. Relatively fine grid resolution was employed where detailed bathymetry
data were available, and complex flow patterns were expected. For example, smaller
node spacing in the inlet and over the flood shoal, as well as at the confluence of Mason
Creek and the Banks Channel, were designed to represent the widely varying
bathymetry in these areas. Larger node spacing was often employed in areas where
flow patterns are not likely to change dramatically, such as on the marsh plain of Middle
Sound. Appropriate implementation of wider node spacing and larger elements reduced
computer run time with no sacrifice of accuracy.
3.2.2 Boundary condition specification
Two types of boundary conditions were employed for the RMA-2 model of the
Mason Inlet system: 1) "slip" boundaries, and 2) tidal elevation boundaries. All of the
elements with land borders have "slip" boundary conditions, where the direction of flow
was constrained shore-parallel. The model generated all internal boundary conditions
from the governing conservation equations. Tidal boundary conditions were specified
offshore the Inlet and at the limits of the AIWW included in the model grid. Tide
measurements from the deployed gauges (i.e., offshore Mason Inlet, at the AIWW
junction with Lollipop Bay, and at the Figure Eight Island bridge across the AIWW)
provided the required data.
The rise and fall of the tide offshore Mason Inlet is the primary driving force for
estuarine circulation in this system. In addition, the phase and amplitude variation
between the AIWW model boundaries provided secondary driving forces for the estuary
system. Dynamic (time-varying) model simulations specified anew water surface
elevation at the three model open boundaries every model time step of 10 minutes,
which corresponds to the time step of the tide data measurements.
3.2.3 Calibration
After developing the finite element grid, and specifying boundary conditions, the
model for the Mason Creek system was calibrated. The calibration procedure ensures
that the model predicts accurately what was observed in nature during the field
measurement program. Numerous model simulations are required (typically 20+) for an
estuary model, specifying a range of friction and eddy viscosity coefficients, to calibrate
the model.
Calibration of the hydrodynamic model required a close match between the
modeled and measured tides in each of the sub-embayments where tides were
measured (i.e., from the tide gauge deployments). Initially, the model was calibrated to
obtain visual agreement between modeled and measured tides. Once visual agreement
was achieved, a seven lunar-day period (14 tide cycles) was modeled to calibrate the
model based on dominant tidal constituents discussed in Section 2. The seven-day
period was extracted from a longer simulation to avoid effects of model spin-up, and to
focus on average tidal conditions. Modeled tides for the calibration time period were
evaluated for time (phase) lag and height damping of dominant tidal constituents.
12

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
The calibration was performed for aseven-lunar-day period (14 tide cycles, or
7.25 solar days) beginning July 5, 2003 1300 EST. This representative time period
spanned the transition between spring and neap tide ranges (bi-weekly maximum and
minimum tidal ranges, respectively). This simulation period also framed the time
covered during the July 8, 2003 ADCP survey of the inlet, which was used to verify the
model's performance.
3.2.3.1 Friction coefficients
Friction inhibits flow along the bottom and sides of estuary channels or other flow
regions where velocities are relatively high. Friction is a measure of the channel
roughness, and can cause both significant amplitude damping and phase delay of the
tidal signal. Friction is approximated in RMA-2 as a Manning coefficient, and is applied
to grid areas by user specified material types. Initially, Manning's friction coefficient
values of 0.03 were specified for all element material types. This value corresponds to
typical Manning's coefficients determined experimentally in smooth earth-lined channels
with no weeds (low friction) (Henderson, 1966).
During calibration, friction coefficients were incrementally changed throughout
the model domain. Friction coefficients are assigned to the model grid using material-
type divisions used by the RMA-2 code, as defined by the user. The material type
divisions used for the Mason Creek system are shown in Figure 3-2. Final model
calibration runs incorporated various specific values for Manning's friction coefficients,
depending upon flow damping characteristics of separate regions within the estuary
system. Manning's values for different bottom types were initially selected based ranges
provided by the Civil Engineering Reference Manual (Lindeburg, 1992), and values were
incrementally changed when necessary to obtain a close match between measured and
modeled tides. Final calibrated friction coefficients are summarized in the Table 3-1.
Table 3-1. Manning's Roughness
coefficients used in simulations of
modeled embayments. These
embayment delineations correspond to
the material type areas shown in Figure
3-2.
System Division Bottom
Friction
Offshore 0.030
Inlet Channel 0.025
Mason Creek 0.025
AIWW North Channel 0.025
AIWW South Channel 0.025
Banks Channel 0.025
Marsh Plain 0.070
Old Inlet Channel 0.030
Inlet Tidal Bank 0.040
13

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
•
Figure 3-2. Detail of finite element grid of Mason Inlet, showing material-type divisions used to
vary bottom friction and eddy viscosity model coefficients across the model domain.

3.2.3.2 Turbulent exchange coefficients
Turbulent exchange coefficients approximate energy losses due to internal
friction between fluid particles. The significance of turbulent energy losses increases
where flow is swifter, such as inlets and bridge constrictions. According to King (1990),
these values are proportional to element dimensions (numerical effects) and flow
velocities (physics). Typically, model turbulence coefficients were set between 80 and
200 Ib-sec/ft2. In most cases, the Mason Creek system was relatively insensitive to
turbulent exchange coefficients. The exception was at the inlet and open boundaries
located at the modeled limits of the AIWW. Higher exchange coefficient values (200 Ib-
sec/ft2) were used to ensure numerical stability in these areas characterized by strong
turbulent flows and large velocity magnitudes.
3.2.3.3 Marsh porosity processes
Modeled hydrodynamics were complicated by wetting/drying cycles on the marsh
plain included in the model of the Mason Creek system. Cyclically wet/dry areas of the
marsh will tend to store waters as the tide begins to ebb and then slowly release water
as the water level drops within the creeks and channels. This store-and-release
characteristic of these marsh regions was partially responsible for the distortion of the
tidal signal, and the elongation of the ebb phase of the tide. On the flood phase, water
rises within the channels and creeks initially until water surface elevation reaches the
marsh plain, when at this point the water level remains nearly constant as water `fans'
out over the marsh surface. The rapid flooding of the marsh surface corresponds to a
flattening out of the tide curve approaching high water. Marsh porosity is a feature of the
14

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
RMA-2 model that permits the modeling of hydrodynamics in marshes. This model
feature essentially simulates the store-and-release capability of the marsh plain by
allowing grid elements to transition gradually between wet and dry states. This
technique allows RMA-2 to change the ability of an element to hold water, like squeezing
a sponge. The marsh porosity feature of RMA-2 is typically utilized in estuarine systems
where the marsh plain has a significant impact on the hydrodynamics of a system, such
as the Mason Inlet estuary system, where the marsh plain accounts for more than 50%
of the modeled area.
3.2.3.4 Comparison of modeled tides and measured tide data
A best-fit of model predictions for the tide gauge deployment data was achieved
using the aforementioned values for friction and turbulent exchange. Figures 3-3
through and 3-8 illustrate the seven-day calibration simulation along with a 50-hour sub-
section. Modeled (solid line) and measured (dotted line) tides are illustrated at each
model location with a corresponding tide gauge station.
Although visual calibration achieved reasonable modeled tidal hydrodynamics,
further tidal constituent calibration was required to quantify the accuracy of the models.
Calibration of M2 (principle lunar semidiurnal constituent) was the highest priority since
the Mz accounted for a majority of the forcing tide energy in the modeled systems. Due
to the duration of the model runs, two dominant tidal constituents were selected for
constituent comparison: K~, M2. Measured tidal constituent heights (H) and time lags
(~~a9) shown in Table 3-2 for the calibration period differ from those in Table 3-2 because
constituents were computed for only aseven-day sub-section of the 39-day period
represented in Table 2-2. Table 3-2 compares tidal constituent amplitude (height) and
relative phase (time) for modeled and measured tides at the tide gauge locations. The
constituent phase shows the relative timing of each separate constituent at a particular
location, and also the change (or phase lag) in timing of a single constituent at different
locations in an estuary.
The constituent calibration resulted in excellent agreement between modeled and
measured tides. The largest errors associated with tidal constituent amplitude were on
the order of 0.01 ft, which is better than the order of accuracy of the tide gauges
(generally order of ±0.1 ft). Time lag errors were typically less than the time increment
resolved by the model (1/6 hours or 10 minutes), indicating good agreement between
the model and data.
•
15

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
^ Y
o -observed
z 2 - -- computed .....__..._....._....... _........_ .................._..............................
c
0 ......................:.................................................:.....................:........................
a~
a~i
_2 ................................................:.......................... ...........................
m
~ -4
50 60 70 80 90 100
simulation time (hr)
„ 4
0
z 2 ..........................................................................; ................
0 .............................. ................. ...............................................................
a~i
~, -2
~ w
~ _4
40 60 80 100 120 140
simulation time (hr)
Figure 3-3. Comparison of model output and measured tides for the tide gauge location
offshore Mason Inlet (M4, Figure 2-1 ). The top plot is a 50-hour sub-section of the
total modeled time period, shown in the bottom plot.
_ 4
~ - observed
~ 2 -._.. computed ............................ ......................................................... .
z
~ ~
~ 0 ................................................................................................................ .
a~
~ -2
~_4I i i
50 60 70 80 90 100
simulation time (hr)
4
0
z 2 ........................................................................':........
~ 0 .............:...................:.................. ..................:.............................................
a~i
_2 ...............:...................................:............ ....._.................. ;...........................
~ -4
40 60 80 100 120 140
simulation time (hr)
Figure 3-4. Comparison of model output and measured tides for the tide gauge location inside
Mason Inlet (M5, Figure 2-1 ). The top plot is a 50-hour sub-section of the total
modeled time period, shown in the bottom plot
s
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Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
•
•
50 60 70 80 90 100
simulation time (hr)
_ 4
0
z 2
N 0
a~
y -2
is
~ -4
„ 4
0
z z
0
ar
~ -2
40 60 80 100 120 140
simulation time (hr)
Figure 3-5. Comparison of model output and measured tides for the tide gauge location at the
Mason Creek/ AIWW junction (M2, Figure 2-1 ). The top plot is a 50-hour sub-
section of the total modeled time period, shown in the bottom plot
~ -4
,..~ 4
z Z
v 0
a~
~ -2
is
~ -4
4
m
w 2
a~
U
N
- observed
_.. - - computed ....................................................................................... _
50 60 70 80 90
simulation time (hr)
100
1'j, ~ ;, ~' / I ,
Ji
40 60 80 100 120 140
simulation time (hours)
Figure 3-6. Comparison of model output and measured tides for the tide gauge location at the
Lollipop Bay/AIWW junction (M1, Figure 2-1 ). The top plot is a 50-hour sub-section
of the total modeled time period, shown in the bottom plot
m -2
N
-4
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Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
4
~ -observed
-._..
C~7 2 computed .............:............................................................................
z
0 ............................................... .................................................. .......................
a~
_2 ............... ........................... .............................................................. ....... ...
i~
3 -4
50 60 70 80 90 100
simulation time (hr)
„ 4
0
z 2 ......................................................................
0 .............................................................................................................
~ -2
~ _4
40 60 80 100 120 140
simulation time (hr)
Figure 3-7. Comparison of model output and measured tides for the tide gauge location at the
Figure Eight Island bridge/ AIWW junction (M3, Figure 2-1 ). The top plot is a 50-
hoursub-section of the total modeled time period, shown in the bottom plot
_ 4
~ -observed '
~ 2 ... -._.. computed ..........................:.........................................................
z ~ ~ i
i
+s=
~-- 0 ......................:.........................................................................: ......................
~ ~
- ~
_2 ............... ........................... ~.............................,..........................,........~...............
3 -4
50 60 70 80 90 100
simulation time (hr)
4
C9 2 ..................................<.............. ...<.................. ;......................... .........
z
0 ....................................................................................... ..........................
~, -2
~ _4
40 60 80 100 120 140
simulation time (hr)
Figure 3-8. Comparison of model output and measured tides for the tide gauge location in the
Banks Channel (M6, Figure 2-1 ). The top plot is a 50-hour sub-section of the total
modeled time period, shown in the bottom plot
•

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18

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
•
Table 3-2. Tidal constituents for measured water level data and
calibrated model output, with model error amplitudes, for the Mason
Inlets stem, Burin modeled calibration time eriod.
Model calibration run
Constituent Phase (deg)
Location Amplitude (ft)
M2 K~ M2
Offshore Mason Inlet* 2.08 0.43 8.6
Mason Inlet 2.01 0.43 14.2
Mason Creek/AIWW Junction 1.92 0.43 29.6
Lollipop Bay (AIWW) 1.98 0.43 25.7
Figure Eight Bridge (AIWW) 1.80 0.43 36.9
Banks Channel 1.82 0.42 38.7
Measured tide Burin calibration eriod
Constituent Phase (deg)
Location Amplitude (ft)
M2 K~ M2
Offshore Mason Inlet* 2.08 0.43 8.6
Mason Inlet 2.01 0.43 17.1
Mason Creek/AIWW Junction 1.93 0.43 30.9
Lollipop Bay (AIWW) 1.97 0.43 25.6
Figure Eight Bridge (AIWW) 1.81 0.43 36.6
Banks Channel 1.87 0.41 39.7
Error
Error Amplitude (ft) Phase error
Location (min)
M2 K~ MZ
Offshore Mason Inlet* 0.00 0.00 0.0
Mason Inlet -0.01 0.00 6.0
Mason Creek/AIWW Junction 0.01 0.00 2.9
Lollipop Bay (AIWW) 0.00 0.00 -0.2
Figure Eight Bridge (AIWW) 0.01 0.01 0.1
Banks Channel 0.05 -0.01 2.2
3.2.5 ADCP verification of the Mason Inlet system model
An additional model verification check was possible by using collected ADCP
velocity data to verify the performance of the Mason Inlet model. Computed flow rates
from the model were compared to flow rates determined using the measured velocity
data. The ADCP data was collected July 8, 2003 (Welsh, 2003) at one transect across
the inlet, during only the flood-portion of the tide. For the model ADCP verification, the
Mason Inlet model was run for the period covered during the ADCP survey. Model flow
rates were computed in RMA-2 at continuity lines (channel cross-sections) that
correspond to the actual ADCP transect followed in the survey (i.e., across the inlet
channel).
Comparisons of the measured and modeled volume flow rates through Mason
Inlet are shown in Figure 3-9. In this figure, the top plot shows the flow comparison, and
the lower plot shows the time series of tide elevation at the Inlet for the same period.
19

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
Each ADCP point (individual points shown on the plots) is a summation of flow
measured across the ADCP transect. The `bumps' and `skips' of the flow rate curve
(more evident in the model output) can be attributed to the effects of winds (i.e.,
atmospheric effects) on the water surface and friction across the seabed periodically
retarding or accelerating the flow through the inlets, and inside the system channels. If
water surface elevations changed smoothly as a sinusoid, the volume flow rate would
also appear as a smooth curve. However, since the rate at which water surface
elevations change does not vary smoothly, the flow rate curve is expected to show short-
period fluctuations.
Data comparisons at the ADCP transect show good agreement with the model
predictions. The computed root-mean-square (rms) error of the model output, compared
to the ADCP data, is 539 ft3/sec or 11.5% of the maximum measured flow rate. Much of
the error can be attributed to the measurement technique's inability to measure flows in
the shallow channel margins. This minor shortcoming is evident at the peak flood flow,
where the measured flow is lower than the flow computed by the model. Although
measured flow slightly underestimates model flow, the error is minor and the
characteristics of the flow are identical.
6000
4000
2000
M
~}-v' 0
_~
l4
L
-2000
-4000
-6000
06h 08h
0 4
C7
z 2
~_
= 0
0
.~
°~i -2
a~
~ 4
10h 12h 14h 16h 18h
06h 08h 10h 12h 14h 16h 18h
hour, July 8, 2003
Figure 3-9. Comparison of measured volume flow rates versus modeled flow rates (top plot)
through West Bay Inlet over a flood tidal on July 8, 2003. Flood flows into the inlet
are positive (+), and ebb flows out of the inlet are negative (-). The bottom plot
shows the tide elevation offshore Dead Neck. (RZ=0.87, error~ms=11.5%).
•

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Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
4. CIRCULATION CHARACTERISTICS AND IMPACTS OF DREDGING OPTIONS
The final calibrated model serves as a useful tool in investigating the circulation
characteristics of the Mason Inlet system and any proposed dredging improvements of
the Inlet channels. Using model inputs of bathymetry and tide data, current velocities
and flow rates can be determined at any point in the model domain. This is a very
useful feature of a hydrodynamic model, where a limited amount of collected data can be
expanded to determine the physical attributes of the system in areas where no physical
data record exists.
In addition to the modeled present conditions of the Mason Creek system, three
dredging options were modeled to investigate the circulation characteristics of the
present conditions of the system, and how the system may respond to the different
dredging plans. This analysis examines 1) residual circulation and 2) residual velocities,
i.e., the flood or ebb dominance of the main channels in the Mason Inlet system. The
focus areas are the junction of the AIWW and Mason Creek, and the Mason Inlet
junction of Mason Creek and the Banks Channel.
The layouts of the three modeled dredging options are shown in Figure 4-1. All
options included the dredging of Mason Creek to a depth of -10 ft NGVD. For Option A,
(red line in Figure 4-1) the inlet channel would be dredged to a depth of -10 ft NGVD,
and a sedimentation basin would be dredged in an area which includes a portion of the
present flood shoal, to a depth of -12 ft NGVD. Option A is the original dredging plan for
the inlet relocation project, as permitted. For Option B (green line in Figure 4-1 ), the
flood shoal would be removed, and the inlet channel would be dredged, all to a depth of
-12 ft NGVD. In Option C, two areas (blue and pink areas in Figure 4-1) in the Banks
Channel would be dredged to a depth of -8 ft NGVD.
f 7~_. ~. _
± ~ a
,~
lr.'~ - f~~' I
Dredging ©ptions
f ~ Option A: Inlet and Sedimentation Basin
Mason Gn3ek ,
Optkm 8: Inlet and Hood Shoal
Ii' ,/vOptian C: Banks Channel
f~~' Option G: kwver Sanks Channel.
y,
f ~ ~, ~ 1 ~
j ~-
~,
r
_.~ ~_,..
Figure 4-1. Planned dredging scenarios modeled for Mason Inlet. All options included the
dredging of Mason Creek (yellow area).
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Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
4.1 System Circulation and Residual Flows
A residual flow is simply the difference between the total flood tide volume and
the total ebb tide volume, across a channel transect. For a tidal estuary system with
only one inlet and no freshwater input, the flow residual would always be zero because
the flood and ebb tides would have equal volumes. For a complex system like the
Mason Inlet system, where there are multiple inputs (i.e., the AIWW and Mason Inlet)
and also multiple pathways for flow within the system (i.e., Mason Creek, the Banks
Channel, and the marsh plain), flow residuals at certain channel transects may be a
large percentage of the flood or ebb volume flux. As an example, if the flood tide volume
through a channel was +1,000,000 ft3, and the ebb volume was -750,000 ft3, the residual
for this channel would be +250,000 ft3, meaning that there was a larger flow through the
channel in the flooding direction.
The residual flow in a tidal channel has implications for sediment transport. For
example, if a channel has an ebb residual, it is likely that a larger volume of sediment will
be mobilized during the ebbing tide compared to the flooding tide. This effect is due to
larger velocities in the residual direction, longer duration of flows in the residual direction,
or the combination of these two factors.
4.1.1 Present Conditions
Flow residuals were computed for present conditions in the Mason Inlet system.
The results are shown in Table 4-1 for the junction of the AIWW and Mason Creek
(location of channel transects shown in Figure 4-2), and in Table 4-2 for the Mason
Creek ad Banks Channel junction at the Inlet (channel transects shown in Figure 4-3).
These residuals were computed based on the model simulation of 14 complete tide
cycles, i.e., the same period of time used for the model calibration. This seven tidal-day
period provides average conditions, as it spans the transition between neap and spring
tide ranges.
4.1.1.1 AIWW /Mason Creek Junction
At the junction of the AIWW and Mason Creek, for present conditions, the
average flood and ebb tide flow volume through the north AIWW channel is nearly equal
to the flow through the sum of south AIWW channel and Mason Creek. In other words,
during flooding conditions in Mason Creek, nearly all of the flow entering the AIWW flows
to the north. The situation is reversed during the ebbing tide, where nearly all of the flow
entering Mason Creek is derived from the AIWW to the north of the junction. This
indicates that velocities in the north AIWW channel generally would be greater than the
other two channels (based on similar channel cross sections), and therefore, there would
be greater sediment transport potential in the north AIWW channel.

There is a large ebb residual in the AIWW channel (from Table 4-1 ), of
approximately 13.7 M ft3 (million cubic feet) per tide cycle. This residual volume is 25%
of the average total flood volume in the north AIWW channel, or 36% of the flow in the
AIWW section south of Mason Creek. In the AIWW, the flooding flow direction is to the
northeast (toward Rich Inlet), and the ebbing flow direction is to the southwest (toward
Masonboro Inlet). The large residual ebb flow through the AIWW indicates that there is
a greater potential for sediment to be transported to the southwest.
22

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
•
•
Table 4-1. Average total flood and ebb tide flow volumes, and
resulting flow res iduals, at model transects at the junction of Mason
Creek and the AI WW, for present conditions and three modeled
dredging options. The AIWW floods to the NE and ebbs to the SW.
Positive (+) resid uals indicate larger flood volume; negative (-)
residuals indicate larger ebb volume. Tide volumes were computed
based on a 14 tide cycle simulation. All volumes are given in cubic
feet er tide c cle ft3/tide .
2003
Channel Flood Ebb Residual (F-E)
Mason Creek 22,755,000 22,919,000 -163,000
AIWW north 55,110,000 68,875,000 -13,765,000
AIWW south 38,176,000 51,883,000 -13,707,000
Option A
Channel Flood Ebb Residual (F-E)
Mason Creek 34,499,000 37,704,000 -3,204,000
AIWW north 56,806,000 72,487,000 -15,681,000
AIWW south 30,172,000 42,619,000 -12,447,000
Option B
Channel Flood Ebb Residual (F-E)
Mason Creek 30,320,000 32,732,000 -2,411,000
AIWW north 55,523,000 70,739,000 -15,215,000
AIWW south 32,421,000 45,358,000 -12,937,000
Option C
Channel Flood Ebb Residual (F-E)
Mason Creek 25,405,000 25,678,000 -273,000
AIWW north 54,626,000 68,712,000 -14,086,000
AIWW south 36,003,000 50,001,000 -13,998,000
;,r
~;r~. =
ti
t A f F ~~ ~*~, t~ A~
~ k.
s -; ~.
f4l t
~~
~ ~
~1. ti's
4.
`` .` .r .
t ~ ~~
....
Figure 4-2. Location of channel transects used to compute total Flood and Ebb flow volumes,
and resulting flow residuals (Table 4-1 ), at the junction of the AIWW and Mason
Creek.
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Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
Table 4-2. Average total flood and ebb tide flow volumes, and
resulting flow residuals, at model transects at Mason Inlet, and the
junction of Mason Creek and the Banks Channel, for present
conditions and three modeled dredging options. Positive (+)
residuals indicate larger flood volume; negative (-) residuals indicate
larger ebb volume. Tide volumes were computed based on a 14 tide
cycle simulation. A ll volumes are given in cubic feet per tide cycle
ft3/tide .
2003
Channel Flood Ebb Residual (F-E)
Inlet 66,206,000 64,496,000 +1,710,000
Mason Creek 29,602,000 29,340,000 +262,000
Banks Channel 25,045,000 22,771,000 +2,273,000
Option A
Channel Flood Ebb Residual (F-E)
Inlet 85,106,000 84,727,000 +379,000
Mason Creek 40,426,000 43,919,000 -3,493,000
Banks Channel 29,546,000 26,206,000 +3,340,000
Option B
Channel Flood Ebb Residual (F-E)
Inlet 84,279,000 82,470,000 +1,809,000
Mason Creek 35,974,000 38,762,000 -2,788,000
Banks Channel 33,277,000 29,640,000 +3,637,000
Option C
Channel Flood Ebb Residual (F-E)
Inlet 75,093,000 73,560,000 +1,532,000
Mason Creek 31,665,000 31522,000 +143,000
Banks Channel 31,322,000 28,750,000 +2,572,000
n7 _~: ~ .~
'"'~ '" Banks
~,~ Channel ~ f ~;, .
;.'
M>gson ~ ;_
Creetc~
f
Ni~aon; h {et
~_
Figure 4-3. Location of channel transects used to compute total Flood and Ebb flow volumes,
and resulting flow residuals (Table 4-2), at the junction of Mason Creek and Banks
Channel at Mason Inlet.
•
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•
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Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
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•
The flow residual of Mason Creek itself is very small by comparison, less than
1 % of the average total flood volume through the Creek. This indicates that the ebb and
flood volumes are well balanced in the Creek. Hence, the sediment transport potential is
not favored in either flow direction by the flow residual of the Creek.
4.1.1.2 Mason Inlet
At the junction of Mason Creek and the Banks Channel at Mason Inlet, flow
residuals are small compared to the average total ebb and flood volumes. From Table
4-2, the flow residuals through the inlet and Mason Creek are less than 1 % of the total
flood volume. In the Banks Channel, there is a larger flood residual, which is 9% of the
total flood volume. The flow residuals at the Inlet indicate that there is a greater potential
for sediment movement during the flooding portion of the tide cycle through the Banks
Channel, but a more balanced potential in the Inlet and the Mason Creek channels, for
present conditions.
4.1.2 Dredging Options
Option A: Dredging the Inlet and Mason Creek as originally permitted will change
system flow rates and residuals significantly. Total flow volume increases most notably
through Mason Inlet (29% flood volume), the Banks Channel (18%), and the northwest
end of Mason Creek (52%). The north channel of the AIWW flows change less than 5%,
and flows through the southern AIWW channel actually decrease by 21 %.
For most channels in the system, though there is a large change in the flood and
ebb volumes, the computed residual flow does not change as greatly. The largest
change in residual flow volume occurs in Mason Creek. In Mason Creek, the flow
residual changes from being insignificant (balanced flow) in present condition to an ebb
residual approximately 7% of the average total flood volume.
Figure 4-4 compares the originally permitted and constructed inlet cross section
(Option A dredge plan) with the measured 2003 cross section. Since the Option A inlet
cross-section is more than double the existing inlet cross section, the increase in tidal
prism resulting from this dredging alternative is not surprising.
~ 2
z 0
v -2
w -4
a -6
v
c -8
~ -10
L -12
,.
channel mean-title
cross=sectional area i -
.. ..,
•~ 2003: 2744 ft~ ~
:.....
southwest tiiarik '. ~ s - northeast bank
Opt A: 5857 fE
_,_„ option A as permitted .........__ .. _ ........:..............................._._.:.... _....._...:_...._...._ E.:.............. _._. .
2003 inlet channel ~._._._,_.~._._._,_.__._._,_._._.._._,_,~ ... ..............
U 0 100 200 300 400 500 600 700 800 900 1000 1100
cross-channel distance (ft)
Figure 4-4. Comparison of inlet cross-sections for present conditions (solid line) and Option A
dredge plan (dot-dashed line). Inlet areas were calculated based on the mean tide
level (MTL), which corresponds to 0.0 ft NGVD at the inlet.
25

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
Option B: Dredging the flood shoal and Mason Creek for this option will modify flow
patterns in a way similar to the Option A plan. More flow is exchanged though the Banks
channel (a 33% change in flood volume, from .present conditions), compared to Option
A. This is due to increased hydraulic efficiency of this channel from removal of the entire
flood shoal. Flow through Mason Creek also increases over present conditions (33% at
the AIWW junction), but the change is not as great as it is in Option A.
The effect of the Option B plan on flow residuals is similar to Option A. The most
significant changes occur in Mason Creek, were there is a resulting 2.4 M ft3 ebb
residual (8% of the average total flood volume). As in Option A, this is a shift for the
Creek, from balanced flood-ebb conditions, to a significant ebb residual.
Option C: The third option causes the least flow changes compared to present
conditions. Flow through the Banks channel increases by 25% from present, which is
the greatest change for this option. Flow residuals remain essentially unchanged from
present conditions, for all channels in the system.
4.2 Tidal Currents and Residual Velocities
Flow velocities are important to characterize because they drive sediment
movement through a tidal system like the Mason Inlet estuary. Similar to flow residuals,
velocity residuals can occur in a tidal channel due to differences in peak ebb and peak
flood current velocities. In a channel where peak tidal velocities are strongest during the
ebb portion of the tide, this channel is characterized as being "ebb dominant".
Conversely, a channel would be described as being "flood dominant" if peak velocities
typically occurred during the flooding portion of the tide.
The characteristic dominance of a tidal channel has direct significance for
sediment transport. An ebb dominant channel has higher velocities during the ebb
portion of the tide, and therefore, more sediment would be mobilized and re-suspended
with the ebb tide. This has implications for inlet systems like Mason Inlet, with regard to
formation of flood or ebb shoals, and sedimentation at channel intersections, such as the
AIWW junction with Mason Creek.
A more thorough analysis technique for determining the flood or ebb dominance
in channels of a tidal system depends upon a harmonic analysis of tidal currents. A
discussion of the method of relative phase determination is presented in Friedrichs and
Aubrey (1988). For this method, the M2 and M4 tidal constituents of a tidal velocity time
series are computed, similar to the tidal surface constituents presented in Section 2.
The relative phase difference is computed as the difference between two times
the MZ phase and the phase of the M4, expressed as ~=2M2-M4. If ~ is between 270
and 90 degrees (-90<~<90), then the channel is characterized as being flood dominant,
and peak flood velocities will be greater than for peak ebb. Alternately, if ~ were
between 90 and 270 degrees (90<~<270), then the channel would be ebb dominant. If
~ is exactly 90 or 270 degrees, neither flood nor ebb dominance occurs. For ~ equal to
exactly 0 or 180 degrees, maximum tidal distortion occurs and the velocity residuals of a
channel are greatest. This relative phase relationship is presented graphically in Figure
4-5.
26

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
velocity gp°
2nnz.M< Figure4-5. Relative velocity phase relationship of M2
and M4 tidal velocity constituents and characteristic
dominance, indicated on the unit circle. Relative phase is
180° Ebh Fiood computed as the difference of two times the MZ phase and
Dominant Dominant ~° the M4 phase (2M2-M4). A relative phase of exactly 90 or
270 degrees indicates a symmetric tide, which is neither
flood nor ebb dominant.
270°
Though this method of tidal constituent analysis provides similar results to a
visual inspection of a velocity record (e.g., by comparing peak ebb and flood velocities),
it allows a more exact characterization of the tidal processes. By this analysis
technique, a channel can be characterized as being strongly, moderately, or weakly
flood or ebb dominant.
4.2.1 Flow Patterns of Present Conditions
Velocity contour plots of present 2003 modeled bathymetry are presented in
Figures 4-5 and 4-6. The model results shown in Figure 4-6 are for a single model time
step during the flood portion of a tide cycle. An interesting feature of the flow at the
AIWW junction with Mason Creek is how much larger the currents in the north AIWW
channel are compared to the south AIWW channel. This result emphasizes the
difference in the flows observed in section 4.1, where model output showed that more
flow passes through the north channel, compared to the south channel (i.e., as in Table
4-1 ). The larger flow causes larger velocities in the north channel of the AIWW. Also
apparent is a velocity "dead zone" at the AIWW junction with Mason Creek. In this area,
swift flooding currents discharging from Mason Creek quickly reduce to near-zero. This
happens because the channel cross sectional area greatly increases from the Creek
channel to the junction.
In the plot of model results shown in Figure 4-7, a single time step from an
ebbing portion of the same tide cycle is shown. Similar to the previous plot, velocities
are greater in the north channel of the AIWW than in the southern channel, and a
velocity "dead zone" appears at the mouth of Mason Creek at the junction.
The "dead zone" provides insight into the cause of the shoaling problems that
occur in this area. It is evident by the model results that sediment mobilized by currents
in the north AIWW channel and in Mason Creek likely would be deposited at the
junction. Velocities and flow turbulence at the junction are smaller than in the channels,
and therefore more favorable to sediment settling and deposition.
4.2.2 Channel Characteristic Tidal Dominance for Present conditions
Time series of velocities taken from the model output at single points were used
to evaluate the characteristic tidal dominance of the main channels of the Mason Inlet
system. Mid-channel velocities for 48-hour sub-sections of the full 14-tide cycle
simulation are presented in Figures 4-7 and 4-8. At Mason Inlet (Figure 4-8), the peak
ebb and flood velocities are similar in magnitude, though there is a slight bias toward
27

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
•
•
Figure 4-7. Example of model output for the Mason Inlet system, for a single time step where
maximum flood velocities occur for this tide cycle. Color contours indicate velocity
magnitude, and vectors indicate the direction of flow.
28
Figure 4-6. Example of model output for the Mason Inlet system, for a single time step where
maximum flood velocities occur for this tide cycle. Color contours indicate velocity
magnitude, and vectors indicate the direction of flow.

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
•
•
•
106 112 118 124 130 136 142 148
simulation time (hours)
Figure 4-8. Time series plot of tidal velocities for channels at Mason Inlet. Positive (+)
velocities are for flooding tides, and negative (-) velocities are for ebbing tides.
3
2.5
2
1.5
~ 1
0.5
~, 0
i!j -0.5
> -1
-1.5
-2
-2.5
3
106 112 118 124 130 136 142 148
simulation time (hours)
Figure 4-9. Time series plot of tidal velocities for channels at the junction of Mason Creek and
the AIWW. Positive (+) velocities are for flooding tides, and negative (-) velocities
are for ebbing tides. The AIWW floods to the northeast and ebbs to the southwest.
3
2.5
2
1.5
~ 1
0.5
7, 0
~ -0.5
> -1
-1.5
-2
-2.5
-3
greater flooding currents. The peak ebb and flood velocities from this simulation at
these channels are shown in Figure 4-10. This figure emphasizes the flood dominance
of the currents in the channels in the vicinity of the inlet.
At the AIWW junction with Mason Creek (Figure 4-9), the ebb dominance of the
AIWW channels is easily seen in the time series plot of tidal currents, especially in the
northern AIWW channel, where peak ebb velocities are nearly two times the peak flood
velocities. The velocities in Mason Creek at the AIWW junction show much stronger
flood dominance than at the other end of the Creek, toward the inlet. Peak velocities at
the AIWW junction are also shown on aerial photo of the inlet system in Figure 4-10.
This view of peak velocities highlights the ebb dominance of the AIWW.
29

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
,. ,.
,~ 4~~ ,
~~ ~~ ~ ,
~ x
1 =. e ` .~ iMM f ~r _
~ a ~,~ ~- ~
2.2
. _ ~ ~~~
V.awl ~i L ~a^3` ^r~, ~.~s) ~~1 ~I ~s'7
s r 4~M ~
mod' ~ ~. l ~ I .
}, 1,~. 7/
.~z; tau: ~~, R ~
iy r ~ ,,y ~: ~
,~` ~,. ~
,.{.
:~ 2.$
Figure 4-10. Peak floo, ~~~ _
d and ebb tide, mid-channel, depth-averaged velocities (ft/sec) in the
Mason Inlet system. Velocities are from the 7-day model simulation of existing
conditions. Blue arrows indicate ebbing peak velocities, and red arrows indicate
flooding peaks.

A harmonic analysis of tidal currents was performed to more exactly characterize S
the tidal dominance of the main channels in the system. The results of this analysis are
presented in Table 4-3, for present conditions at Mason Inlet and the AIWW junction with
Mason Creek. As discussed earlier in Section 4.2, tidal dominance can be quantified by
determining the relative phase (time difference) of the M2 and M4 constituents. The
results show that the inlet channels are moderately to weakly flood dominant. This
would indicate that residual velocities are oriented in the flooding direction, and tidal
currents would slightly favor sediment movement during the flooding tide.
Table 4-3. Present Conditions: Relative velocity phase difference of
M2 and M4 tide constituents, determines using velocity records output from
com uter model simulation of 14 tide c cles.
Inlet
Channel 2M2-Ma Characteristic dominance
relative hase
Mason Inlet 287.5 Weak FLOOD
Mason Creek (at inlet) 321.1 Moderate FLOOD
Banks Channel 305.3 Moderate FLOOD
AIWW Junction
Channel 2M2-Ma Characteristic dominance
relative phase
Mason Creek (at AIWW) 300.9 Moderate FLOOD
AIWW north channel 192.5 Strong EBB
AIWW south channel 183.1 Stron EBB
•
30

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
At the junction of Mason Creek and the AIWW, the relative velocity analysis
shows that the AIWW channel is strongly ebb dominant, while Mason Creek is
moderately flood dominant. This indicates that the velocity residual of the north AIWW
channel and of Mason Creek both direct sediment toward the junction. The velocity
residuals at the junction act together with the flow residuals (discussed in 4.1.1.1) to
make this area, in effect, a sedimentation basin. This is the least favorable configuration
of residuals with regard to significant shoaling potential at the junction.
4.2.4 Dredging Options
•
•
In addition to the modeled present conditions, the velocities in the three dredging
options were analyzed. Table 4-4 shows how peak flood and ebb tidal currents are
changed in each dredging option. Results of the relative constituent phase analysis for
each dredging option are presented in Tables 4-5 through 4-7.
Option A: For this option, peak velocities in the inlet and in the lower portion of Mason
Creek are reduced, compared to present conditions. These reductions occur because of
the deeper dredged channels at the inlet and in the creek. At the northwest end of
Mason Creek, velocities increase due to the 52% increase (as in Table 4-1) in tidal flow
though the channel. Velocities also increase in the Banks Channel due to increased
tidal flow that results from more efficient hydraulic conditions in the dredged inlet
channel.
Table 4-4. Peaks mid-channel, depth-averaged velocities for channels in the Mason
Inlet system. Results from model output of present conditions and three dredging options
are iven. All velocities are in ft/sec.
Channel 2003 Option A Option B Option C
Flood Ebb Flood Ebb Flood Ebb Flood Ebb
Mason Inlet 2.5 2.4 1.8 1.7 2.1 1.9 2.8 2.6
Banks Channel 2.2 1.7 2.5 2.1 2.6 2.8 1.0 0.7
Mason Creek at inlet 1.9 2.0 1.6 1.8 1.5 1.6 1.5 1.2
Mason Creek (at AIWW) 2.4 1.7 3.0 2.5 2.8 2.2 2.4 1.6
AIWW north 1.2 1.8 1.2 1.9 1.2 1.8 1.2 1.8
AIWW south 0.8 1.4 0.8 1.2 0.8 1.2 0.8 1.3
Table 4-5. Option A: Relative velocity phase difference of M2 and M4
tide constituents, determines using velocity records output from computer
model simulation of 14 tide c cles.
Inlet
Channel 2M2-Ma Characteristic dominance
relative phase
Mason Inlet 284.6 Weak FLOOD
Mason Creek (at inlet) 322.7 Moderate FLOOD
Banks Channel 287.4 Weak FLOOD
AIWW Junction
Channel 2M2-Ma Characteristic dominance
relative phase
Mason Creek (at AIWW) 298.3 Moderate FLOOD
AIWW north channel 182.4 Strong EBB
AIWW south channel 194.5 Stron EBB
31

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
Table 4-6. Option B: Relative velocity phase difference of MZ and M4
tide constituents, determines using velocity records output from computer
model simulation of 14 tide c cles.
Inlet
Channel 2M2-Ma Characteristic dominance
relative hase
Mason Inlet 283.7 Weak FLOOD
Mason Creek (at inlet) 334.4 Moderate FLOOD
Banks Channel 290.2 Weak FLOOD
AIWW Junction
Channel 2M2-Ma Characteristic dominance
relative phase
Mason Creek (at AIWW) 299.4 Moderate FLOOD
AIWW north channel 184.0 Strong EBB
AIWW south channel 189.8 Stron EBB
Table 4-7. Option C: Relative velocity phase difference of M2 and M4
tide constituents, determines using velocity records output from computer
model simulation of 14 tide c cles.
Inlet
Channel 2M2-Ma Characteristic dominance
relative hase
Mason Inlet 290.1 Weak FLOOD
Mason Creek (at inlet) 291.8 Weak FLOOD
Banks Channel 293.9 Moderate FLOOD
AIWW Junction
Channel 2MZ-Ma Characteristic dominance
relative hase
Mason Creek (at AIWW) 303.6 Moderate FLOOD
AIWW north channel 183.7 Strong EBB
AIWW south channel 185.8 Stron EBB
The results of the relative phase analysis of currents for the Option A dredging
plan is presented in Table 4-5. Compared to present conditions, the largest change
happens in the Banks channel. For present conditions the channel is moderately flood
dominant, but changes to weakly flood dominant in Option A. This indicates that the
velocity residual in the Banks Channel is reduced for this option, so there would be less
bias for sediment transport in the flooding direction.
Option B: For the option where the flood shoal is dredged, peak velocities in the Banks
Channel increase; and peak ebb currents become larger than those of the flood tide.
Velocities in the northwest end of Mason Creek increase as well. Though the increases
are not as large as in Option A, they have a similar cause, which is more tidal volume
exchange through the system.

The relative phase analysis shows that even though peak velocities occur during
the ebb portion of the tide in the Banks Channel, it still has weak flood dominance. The
actual magnitude of the peaks is less important than the relative phase in determining
32

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
the characteristic dominance of tidal currents. That is to say, the relative duration of the
flood and ebb portions of the tide indicated by the relative phase is more important than
peak current magnitude (which only represent momentary values) for evaluating
possible impacts to sediment transport potential.
Option C: Finally, for Option C (where only the lower portion of the Banks Channel and
the whole Mason Creek channel are dredged), there is a large reduction in velocities in
the Banks Channel due to the channel deepening, even though the tidal flow through the
channel increases from present conditions.
Results of the relative phase analysis of currents modeled for Option C show that
the greatest change occurs in the lower portion of Mason Creek, where its shifts to weak
flood dominance from moderate flood dominance in the present conditions. As with the
Banks Channel in Option A, this indicates that the velocity residual in the lower portion of
the Creek is reduced, and that there is less sediment transport potential in the flooding
direction, than for present conditions.
•
•
33

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
5. SEDIMENT TRANSPORT MODELING
Sediment transport analyses of the Mason Creek system was performed using
the SED2D-WES model developed through the US Army Corps of Engineers (Letter et
al. 1998). Version 3.2 of the model is implemented through the SMS software package,
and is coded to accept transient hydrodynamic output from the RMA-2 model. SED2D is
afinite-element, depth-averaged model, applicable to clay or sand beds (i.e., cohesive
or non-cohesive sediments). Only one effective grain size can be used in the model,
which is a minor limitation for the purposes of this study of Mason Inlet. The model
utilizes a generalized Crank-Nicholson discritization scheme, which allows the user to
specify the level of implicitness used in the computations of time-varying sediment
transport. Model outputs include time-varying bed elevation change resulting from
erosion and deposition, and time-varying bottom shear stress. For the model runs of
Mason Inlet, bottom shear stresses where computed using the Manning shear stress
equation option available in SED2D.
•
Input parameters required for the model includes sediment grain size, diffusion
coefficients, and Manning roughness coefficients. A 0.22 mm sediment grain size was
used for the model runs of the Mason Inlet system, based on the results of a sediment
grain size analysis provided by GBA. Diffusion coefficients were set at 50 m2/sec in both
the X and Y directions, based on model stability requirements. Manning roughness
coefficients for all grid material types were set at 0.04. The SED2D model runs were
executed using the same model meshes developed for the separate RMA-2
hydrodynamic model runs of Mason Inlet present conditions, and the three modeled
alternatives.
Each SED2D model simulation was run for 10 tide cycles to evaluate general
trends in sediment transport within the system. The SED2D modeling performed in this
study for Mason Inlet is not intended to provide absolute magnitudes of bed change, but
instead, to provide a relative measure to indicate areas that are likely to erode or shoal.
These sediment transport modeling results are intended to be used in conjunction with
the analysis of currents and flows, for the determination of impacts and benefits
associated with the different dredging alternatives.
5.1 Present Conditions
Present conditions were simulated in order to evaluate the performance of the
sediment transport model. Model results based on the July 2002 bathymetry of the inlet
were compared to the actual bathymetric change between July 2002 and July 2003.
Bathymetric change for this one-year period is shown in Figure 5-1. This is compared to
model output of the 2002 conditions shown in Figure 5-2, were areas of erosional and
depositional potential are indicated. It should be noted that the apparent erosion
observed in the AIWW between 2002 and 2003 (Figure 5-1) actually is a result of
dredging.
Generally, model results follow observed trends in the bathymetric change
analysis. An area of large erosional change greater than 8 ft in the throat of the Inlet
(shown in Figure 5-1) corresponds to an area with strong erosional potential in the model •
output. Similarly, areas of large depositional change greater than 8 ft on both sides of
the inlet channel and onto the flood shoal correspond to areas with strong depositional
34

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003

t ~ ~_i
i `, hi ,
1';
t$tt
tf a(j{~j
t 5
SSZ{M3A
18t{H~s
~3C?tSl~Jil L 3f?J'. Ji7
.v ~.
~: ~ , J }{3 ESl7~Ut} _, s~UsJti
~'~: , ~ ;
r W~ .;
< ~. ~"~ h
~<.+~;
~y
3~ .1 {)
' ~
~ Y w; ~ _
~.
=z
.. ~ r1
. ~. t,
p~.
G-u0~ :~XJ3 ~'
~S,toi$
6to&
_:4
8`
t
o
J
•
~
..: ... 2 tD ~ ~.Y
-- ,-2 to 3 ''
' '0.5to2 ~
-D.5 - 0.5
-7 to -0.~
-3 to -2
-4 to -2
~ to -41 ,,~y
r - -8 to -fi ~ asp.

~~ Na Via.
~ . 0
~w~~'~' i~(f' 1(kJt; 1500 2C~C Fc :t
~1"'~w~~
2368tkat3 236'30 2370fl0U ~3710t?0 ~37Z{$~4 2373t70o
•
•
Figure 5-1. Bathymetric change in the Mason Inlet system, between July 2002 and July 2003.
Areas of erosion are shaded from gray to red, and deposition is indicated by colors
from gray to dark green. Grid coordinates are NC state plane, feet.
~... ~ . ~ .
f-
,~ .
r: ~.~~.
~ "' ,f ,at~e~~-j
`1R
3
I
;.
"4:i
~IU*
,...
.vkS~
Figure 5-2. Modeled erosion/deposition potential using July 2002 bathymetry. Red areas
indicate erosional potential, while green areas indicate depositional potential.
35

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
potential in the model results. Considering the duration of the model simulation verses •
the time period of the bathymetric change analysis (i.e., 5 days vs. 1 year), the model
shows good agreement with observations, in asemi-quantitative sense.
The July 2003 bathymetry was used to provide a baseline for comparing the
effects of the different dredging plan options. Model output for these present conditions
are shown in Figure 5-3 (transport potential) and Figure 5-4 (average bottom shear
stress). Compared to the modeled 2002 bathymetry, the 2003 results show that the
area of the flood shoal has shifted from depositional to erosional potential. This may
indicate that the flood shoal has reached an equilibrium volume, and will be relatively
stable, baring additional sediment input from the updrift ocean-facing beach. Also, the
upper portion of Mason Creek has become more erosional, an indication that flows in the
channel have increased since 2002, as a result of the Banks Channel becoming less
efficient due to shoaling in the channel and on the flood shoal.
The plot showing the distribution of bottom shear stress, for July 2003 conditions,
is shown in Figure 5-4. Similar to the plot of velocities shown in Figure 4-6 and 4-7, a
shear stress "dead zone" is apparent at the junction of Mason Creek and the AIWW.
This is important because sediment deposition will tend to occur where there are strong
gradients in bottom shear, i.e., sediment mobilized by high bottom stresses will tend to
be deposited in areas were stresses are smaller or near-zero. Therefore, the confluence
of the AIWW and Mason Creek is a strong sediment sink and shoaling likely will
continue. The area showing highest modeled bottom stress is in the channel around the
northwestern side of the flood shoal in the inlet. This indicates that the most flow
diverted to the Banks Channel flows along this path. •
5.2 Modeled Dredging Scenarios
OPTION A: Model results for Option A are presented in Figures 5-5 and 5-6. A black-
dotted line shows the dredged areas in the Creek and the inlet. The area within the
dredged inlet channel (not Mason Creek) and sedimentation basins (on either side of the
main channel) shows a depositional potential. Though the sedimentation basins are
expected to be depositional, the seaward portion of the inlet channel may have regions
of deposition and erosion. The increase in tidal flow will cause some scouring of the ebb
shoal, with potential loss of this sediment to the system. Similar to the period following
initial inlet construction, this inlet configuration appears to be less stable than existing
conditions (seen in Figure 5-3 and 5-4).
Other significant changes are seen in Mason Creek, which becomes more
strongly erosional, compared to present conditions. Even though the channel has been
dredged to a deeper depth, velocities and shear stresses along the Creek channel
increase because of the increase in the total tidal flow though the Creek. The increased
flow through Mason Creek also creates a depositional area at the Mason Creek/AIWW
junction. This occurs as more sediment is mobilized in the Creek, and deposited at the
junction. Comparing the bed change model results with existing conditions (Figures 5-3
and 5-5, respectively), the deposition in the AIWW for Option A is significantly higher,
indicating that this alternative may lead to increased shoaling in the AIWW.
The plot of shear stress in Figure 5-6 shows that shear stress in the Mason •
Creek channel increase compared to present conditions. Stresses in the Banks channel
also increase, due to the larger tidal volume passing through the inlet. Bottom stresses
36

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003

•
•
-v<<~~~:-r. ~
~~
~,
` ~ f.t '~.. Ufa. y~
~ ~ R~-
~ ` ~~~~~~~~ ~ ` f
_ ,' ~,w' 4 ,~ ~
s
.: ~.
.K.
4.
i ;
o-
5 ~ ~ x
x
Figure 5-3. Modeled erosion/deposition potential for present 2003 conditions. Red areas
indicate erosional potential, while green areas indicate depositional potential.
Figure 5-4. Average modeled bottom shear stress for present (2003) conditions.
37

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
~ ~ ;
, n.
L ~' ~ ~ lid
r
~ xx a

~,u „
V ~~G.
~ -a.
,~ ~ . ~ '~
~f~ ~ 1h » f ~~

,tf i
z
f .F
V,~4 ., {~
.~.
~.
~~
K ~ ~
<h
f .~
r ~
Figure 5-5. Modeled erosion/deposition potential for Option A dredging plan. Red areas
indicate erosional potential, while green areas indicate depositional potential.
Black-dotted outline indicated the areas to be dredged.
Figure 5-6. Average modeled bottom shear stress for Option A dredge plan. Black-dotted
outline indicated the areas to be dredged.
•
•

38

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
are nearly zero within the area of the sedimentation basin, which allows this area to
collect sediment, as designed.
OPTION B: Model results for the dredging option that removes the flood shoal are
presented in Figures 5-7 and 5-8. Similar to the results for Option A, this plan
encourages deposition within the area dredged at the inlet, but increases erosional
potential in Mason Creek. A depositional area is created at the junction of the AIWW
and Mason Creek, as was with Option A, for similar reasons. Erosional areas increase
in the Banks channel due to the larger tidal flow through the channel.
Similar to Option A, Option B likely will cause increased shoaling in the AIWW
relative to present conditions. The reduced dredging area associated with Option B
relative to Option A would allow the inlet channel to "self-scour", hence the significant
erosion area at the seaward limit of the dredged area (Figure 5-7). Again, the increased
flow through the inlet likely will cause some scour of the ebb shoal, with the possibility
that this material will be pushed farther offshore and lost to the littoral system.
The effect of increased tidal flow is also seen in the average bottom shear stress
output for Option B (Figure 5-8). Stresses increase in the Banks channel to a greater
degree than shown by the results of Option A, indicating that this area of the Banks
Channel would experience an increase in sediment transport fluxes, over present
conditions. However, removal of the flood shoal will eliminate the observed scour and
high shear stress region along the northwest edge of the flood shoal (Figures 5-3 and 5-
4).
• OPTION C: For this dredging option (where Mason Creek and the Banks Channel are
dredged, and the inlet channel and flood shoal are left intact) changes in sediment
transport and shear stress patterns are not as acute as they are for Option A and B,
relative to existing conditions. In Figure 5-9, model results show that the lower portion of
the Banks Channel and the lower half of Mason Creek near the inlet become
depositional. Conditions along the main channel of the inlet remain similar to present
conditions. This is because the tide volume exchanged through the inlet only slightly
increases over present conditions. Most of the increased flow through the inlet is
diverted through the Banks Channel. This causes the main channel around the
northwestern edge of the flood shoal to become more erosional.
Model output of average bottom shear stress for Option C is presented in Figure
5-10. This output shows that shear stresses are elevated around the northwestern
extent of the flood shoal, as expected based on the sediment transport potential results.
Farther up in the Banks Channel, shear stresses are greatly reduced due to the dredged
area of the channel. Stresses in Mason Creek are slightly reduced from present
conditions. This reduction occurs because the channel has been dredged, but the tidal
flow through the channel does not significantly increase.
Overall, Option C appears to provide the most stable conditions for future
maintenance of the Mason Inlet system. Although additional scour can be anticipated
along the northwestern edge of the flood shoal, shear stresses in both the Banks
Channel and Mason Creek will decrease. Therefore, the dredged portions of these
channels likely will act as sedimentation basins, decreasing the amount of deposition in
• the AIVW1l (at the junction of Mason Creek) and in the portion of the Banks Channel
landward of the developed section of Figure Eight Island.
39

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
-,-- 1r --^-~---- . _-_.--~f ~--
a~ ~

w
.
w
~'
i yt
~ 4
Y ~'rb ~;
~., a

3

~ ~~ .
` i ~ ~
~~ f . ~'
+1 . ~... ... y.
... ,"t
;~ .
Figure 5-7.
-...
:t
-< e _.
Modeled erosion/deposition potential for Option B dredging plan. Red areas
indicate erosional potential, while green areas indicate depositional potential.
Black-dotted outline indicated the areas to be dredged.
•

Figure 5-8. Average modeled bottom shear stress for Option B dredge plan. Black-dotted
outline indicated the areas to be dredged.
•
40

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
•

•

. ~ _ ~" _
~y ., ,
~r.
~~ ` jMr
~; ~ ~~
* ~
t~
.s -
i:;. ~ : ~ S s
'

` ~~~
;_ f 4 Y
~ i
~
.~' a 7
~-
,~~, ~

., r

...

'.
.a r
n .~. .~

Figure 5-9. Modeled erosion/deposition potential for Option C dredging plan. Red areas
indicate erosional potential, while green areas indicate depositional potential.
Black-dotted outline indicated the areas to be dredged.
~~
1. ; ;
j..
R
-~.
# ~ r ~,
,,,, r,,
Figure 5-10. Average modeled bottom shear stress for Option C dredge plan. Black-dotted
outline indicated the areas to be dredged.
41

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
6. CONCLUSIONS .
The hydrodynamic and sediment transport analyses of the Mason Inlet estuary
provides insight into the dynamics of this complex tidal system. The computer models
developed for this system are valuable tools that greatly expand the utility of data
collected from the physical system. The hydrodynamic model was calibrated with in situ
tide measurements and later validated with current measurements within the inlet throat.
The combined calibration/validation process provides a high level of confidence that the
model simulates actual flow through the channels and across the marsh plain. Based on
the hydrodynamic model, atwo-dimensional sediment transport model was developed.
Model results for present conditions indicated similar accretion and erosion trends as
those observed during the July 2002 to July 2003 timeframe. Again, favorable
comparisons with observations indicate that the sediment transport model adequately
predicts erosion and accretion trends within the Mason Inlet system. Based on the
hydrodynamic and sediment transport modeling results, the models were used in a
predictive mode to assess a range of potential dredging options. The calibrated
hydrodynamic and sediment transport models provide a simple method for evaluating
bathymetric changes within the system to ensure that potential adverse impacts
associated with alternative dredging options can be addressed a priori.
The results of the hydrodynamics analysis for existing conditions illustrates the
mechanisms likely responsible for the observed shoaling at the AIWW junction with
Mason Creek, as well as in the lower Portion of the Banks Channel, near the Inlet. Flow
velocity residuals indicate that the AIWW is strongly ebb dominant, and therefore directs •
sediment to the confluence of the AIWW and Mason Creek. In addition, Mason Creek is
presently moderately flood dominant, and hence favors sediment transport toward the
AIWW junction. Prior to re-opening Mason Creek to the AIWW, no physical mechanism
existed to cause this confluence of tidal current residuals. Similar to Mason Creek, the
Banks Channel is moderately flood dominant, with a large flood residual flow. This result
indicates that conditions favor sediment movement into the channel from the inlet. At
both the AIWW junction with Mason Creek and in the seaward portion of the Banks
Channel, tidal dynamics favor sediment deposition.
The analysis of dredging alternatives shows that Option A (dredging as originally
permitted) and Option B (dredging flood shoal and Mason Creek) have similar impacts
on system hydrodynamics and sediment transport patterns. Both options greatly
increase the tidal volume exchanged through the main system channels, and the
erosional potential of Mason Creek and the Banks Channel increase from present
conditions.
For Option A, even though the channel has been dredged to a deeper depth,
velocities and shear stresses along the Creek channel increase because of the increase
in the total tidal flow though the Creek. The increased flow through Mason Creek also
creates a depositional area at the Mason Creek/AIWW junction. This occurs as more
sediment is mobilized in the Creek, and deposited at the junction. Comparing the bed
change model results with existing conditions, the deposition in the AIWW for Option A is
significantly higher, indicating that this alternative may lead to increased shoaling in the
AIWW. Similar to Option A, Option B likely will cause increased shoaling in the AIWW .
relative to present conditions. The reduced dredging area associated with Option B
relative to Option A would allow the inlet channel to "self-scour", hence the significant
42

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
• erosion area at the seaward limit of the dredged area (Figure 5-7). Again, the increased
flow through the inlet likely will cause some scour of the ebb shoal, with the possibility
that this material will be pushed farther offshore and lost to the littoral system.
For Option C (where Mason Creek and the Banks Channel are dredged, and the
inlet channel and flood shoal are left intact), changes in sediment transport and shear
stress patterns are not as acute as they are for Option A and B, relative to existing
conditions. Sediment transport model results show that the lower portion of the Banks
Channel and the lower half of Mason Creek near the inlet become depositional.
Conditions along the main channel of the inlet remain similar to present conditions. This
is because the tide volume exchanged through the inlet only slightly increases over
present conditions. Most of the increased flow through the inlet is diverted through the
Banks Channel. This causes the main channel around the northwestern edge of the
flood shoal to become more erosional.
Overall, Option C appears to provide the most stable conditions for future
maintenance of the Mason Inlet system. Although additional scour can be anticipated
along the northwestern edge of the flood shoal, shear stresses in both the Banks
Channel and Mason Creek will decrease. Therefore, the dredged portions of these
channels likely will act as sedimentation basins, decreasing the amount of deposition in
the AIWW (at the junction of Mason Creek) and in the portion of the Banks Channel
landward of the developed section of Figure Eight Island. Less change in system
dynamics is seen in the output from Option C model runs. Tidal exchange increases are
small compared to Options A and B because the inlet channel and flood shoal are not
dredged. The inlet channel and flood shoal strongly influence the tidal flux of the
system, much more so than conditions in Mason Creek and the Banks Channel.
Based on model results of the different dredging options, possible suggestions to
improve the shoaling conditions within the Mason Inlet system include: 1) dredging a
sedimentation basin in the north AIWW channel a the junction with Mason Creek, and 2)
following the dredging plan of Option C. The first suggestion addresses the shoaling
problem at the AIWW junction by providing a deep basin for the settlement of sediment.
This junction area is a natural sediment trap, mostly due to the tidal characteristics of
both the AIWW and Creek. The second suggestion is based on the performance of the
three modeled options. Options A and B both greatly increase the tidal flow though the
system, and in turn increase velocities and sediment fluxes. Option C is the most
favorable for system stability and navigation interests in the Banks Channel.
Figure 4-4 shows the 2003 inlet cross-section that has "equilibrated" to the
existing tidal regime. This cross-section is less than 50% of the Option Across-section;
however, the modeling analysis indicates that sediment movement within the existing
channels is significantly lower than those resulting from this dredging option.
Specifically, the smaller inlet cross-section lowers the rate of shoaling at the confluence
of Mason Creek and the AIWW. Therefore, an inlet cross-section of approximately
2,700 fttz relative to NGVD appears to be appropriate, as long as wave-induced transport
along the coast does not overwhelm the inlet.

43

Applied Coastal Research and Engineering, Inc. Mason Inlet, 2003
7. REFERENCES ~'
Brigham Young University (1998). "User's Manual, Surfacewater Modeling System."
Dyer, K.R. (1997). Estuaries, A Physical Introduction, 2"d Edition, John Wiley & Sons,
NY, 195 pp.
Friedrichs, C.T. and D.G. Aubrey (1988). "Non-linear Tidal Distortion in Shallow Well-
mixed Estuaries: a Synthesis." Estuarine, Coastal and Shelf Science (27), pp
521-545.
King, Ian P. (1990). "Program Documentation - RMA2 - A Two Dimensional Finite
Element Model for Flow in Estuaries and Streams." Resource Management
Associates, Lafayette, CA.
Kelley, S.W., Ramsey, J.R., Cote, J.M., Wood, J.D. (2001). "Tidal Flushing
Analysis of Coastal Embayments in Chatham, MA" Applied Coastal
Research and Engineering, Inc. report prepared for the Town of Chatham. 115
pP•
Letter, J.V., L.C. Roig, B.P. Donnell, W.A. Thomas, W.H. McAnally, S.A. Adamec (1998).
"User's Manual for SED2D-WES, a Genralized Computer Program for Two-
Dimensional, Vertically Averaged Sediment Transport." US Army Corps of
Engineers, Waterways Experiment Station, Vicksburg, MS.
Lindeburg, Michael R. (1992). Civil Engineering Reference Manual, Sixth Edition.
Professional Publications, Inc., Belmont, CA.
Norton, W.R., I.P. King and G.T. Orlob (1973). "A Finite Element Model for Lower
Granite Reservoir", prepared for the Walla Walla District, U.S. Army Corps of
Engineers, Walla Walla, WA.
Ramsey, J.R. (2002). "Lyon's Bridge Causeway Openings." Applied Coastal Research
and Engineering, Inc., technical memo prepared for Martin County, Florida.
Ramsey, J.R. and Ruthven, T. H. (2003). "Hydrodynamic Analysis of Hog Marsh and
Popar Island Cell 3D." Applied Coastal Research and Engineering, Inc.
Van de Kreeke, J. (1988). "Chapter 3: Dispersion in Shallow Estuaries." In:
Hydrodynamics of Estuaries, Volume I, Estuarine Physics, (B.J. Kjerfve, ed.).
CRC Press, Inc. pp. 27-39.
Welsh, John (2003) "Mason Inlet ADCP Data, June 27 and July 8, 2003." University of
North Carolina at Wilmington, Center for Marine Science, Wilmington, NC.
Zimmerman, J.T.F. (1988). "Chapter 6: Estuarine Residence Times." In:
Hydrodynamics of Estuaries, Volume I, Estuarine Physics, (B.J. Kjerfve, ed.).
CRC Press, Inc. pp. 75-84.
~_
44

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