OakIsland_Caswell_MonitoringProcedure Jan2020_final

,", 4700 Falls of Neuse Road, Suite 300
Raleigh, NC 27609
m o f f a t t & n i c h o l [phone] Fax: [phone]
www.moffattnichol.com
January 30, 2020
Ms. Heather Coats
Division of Coastal Management
127 Cardinal Drive Extension
Wilmington, NC 28405
Re: Town of Oak Island Proposed Shoreline Monitoring Plan for Caswell Beach
Dear Ms. Coats,
After the meeting held on January 16, 2020, the Town of Oak Island (Town) received the Village of
Bald Head Island's (VBHI), Terminal Groin Project Inlet Plan, Oak Island Monitoring report. The
Town has reviewed the report to determine if they could proceed utilizing the same guidelines as
detailed in the VBHI's monitoring plan. The Town understands and agrees that it is difficult to develop
baseline conditions given storms, intermittent survey data availability, and ongoing US Army Corps
of Engineers beneficial use placements from the Wilmington Harbor Maintenance project. The Town
offers the following protocol for monitoring Caswell Beach's oceanfront as a result of excavating
approximately 1.1 million cubic yards from the Jay Bird Shoals borrow area:
1) The Town will evaluate available historical datasets and calculate mean change and standard
deviations for Mean High Water (MHW) shoreline and volume changes above -2ft NGVD
and out to depth of closure. Efforts will be made to determine overall calculations and
calculations within discrete timeframes in order to bracket storms and other effects (from
nourishment) to the extent practicable.
2) The Town will collect surveys from Station 20+00 to 200+00 (every 1,000 ft) beginning in
spring 2020 (in addition to the annual surveys collected by the Town every 1,000 ft from
Station 210+00 — 700+00), as shown in Figure 1 below. This initial survey will represent the
conditions before the Town will construct its anticipated renourishment project in 2020
utilizing the Jay Bird Shoals borrow area.
The Town will collect surveys annually within the area identified (Station 20+00 to 200+00),
for a minimum of 3 years after utilizing the Jay Bird Shoals borrow area. The Town's Engineer
will calculate MHW shoreline and volume changes annually and will compare them to the
available historical calculations outlined in Item 1.
3) If the average calculated values over any three adjacent beach profile survey transects (covering
a 33000 ft section of shoreline) exceeds the mean values by ± one standard deviation, the Town
will convene a Technical Advisory Committee (TAC) consisting of three coastal engineers
registered in the State of North Carolina, (1 — Oak Island, 1— Caswell Beach, 1— Independent)
to review the measured MHW shoreline and volume changes and investigate potential causes.
The TAC will determine if a cause determination for the exceedance can be made or if
additional monitoring is required.
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If the TAC is not activated within 3 years after utilizing the Jay Bird Shoals borrow area, the
Caswell Beach monitoring requirements for the Town will cease.
4) If the TAC is engaged and agrees that the utilization of Jay Bird Shoals borrow area is causing
unintentional effects on Caswell, the Town will be responsible for mitigation. Mitigation will
most likely consist of the Town paying the United States Army Corps of Engineers to dredge
and place additional material in the affected areas during the next Wilmington Harbor
Maintenance project when placement is planned for Caswell Beach/Oak Island oceanfront.
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Figure 1. Caswell/Oak Island Monitoring Stations
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Sincerely,
MOFFATT & NICHOL
Johnny Martin, P.E.
Project Manager
CC.
Jonathan Howell, DCM
Ronnie Smith, USACE
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