20120868 Ver 3_Agency Consultation_20211006

NEW HANOVER COUNTY
ENGINEERING
230 Government Center Drive, Suite 160, Wilmington, NC 28403
P: [phone] I F: [phone] I NHCgov.com
Jim Iannucci, PE, CFM, County Engineer
6 October 2021
Resource Agencies:
New Hanover County, Carolina Beach Inlet:
Email Transmittal
On 29 September, the US Army Corps of Engineers (USACE) notified New Hanover County
(NHC) that the special purpose dredge Murden may return to the Wilmington District for a brief
mechanical maintenance event in the mid to late October timeframe before immediately
returning to the Northeast. There is a potential maintenance dredge event of approximately 24
hours before the Murden enters the maintenance yard and before returning north for the winter.
A mid/late October hopper dredging event facilitating the inshore dredge material management
site (IDMMS) would be beneficial. As a result of the most recent Coastal Barrier Resources Act
(CBRA) dredge material management interpretation, NHC has initiated a supplemental IDMMS
volume tracking approach. The CBRA interpretation's impact on NHC's programmatic approach
to regional sediment management is significantly worrisome. NHC's baseline volumetric
capacity tracking began on 30 August; this survey indicated an accepting capacity of —245,000
cubic yards below the -14' contour.
For planning purposes, NHC and the USACE are marking an approximate 2-day maintenance
dredging event predicated on the Murden's availability and schedule. Based on a 27 September
survey, the template dredge volumes range from - 6,334 cubic yards (cy) in the -8' template to
-26,775 cy in the -10' template. With these surveyed volumes, NHC would make use of the
IDMMS as authorized by the NC Division of Coastal Management (NCDCM) Permit 50-16,
expiration date 12/2025. However, the October availability of the USACE hopper dredge would
place the proposed maintenance event outside NHC's IDMMS environmental window.
Understanding the USACE's dredge plant forecasting challenges and as an operational
precaution, NHC is requesting an approximate 30-day early entrance environmental window
exception. In support of the exception request, NHC is providing supplemental documentation as
previously requested by the NC Division of Coastal Management (NCDCM), the NC Division of
Marine Fisheries (NCDMF) and the National Marine Fisheries Service (NMFS).
Supplemental Documentation
Statement of purpose and need specific to this event:
• Maintaining CBI as an ocean accessible route from Myrtle Grove Sound and adjacent
NHC estuarine areas;
• Responding to shoaled conditions and the USCG's mandated year-round aids to
navigation (ATONs) access and
• Implementing a resource conservation and adaptive dredge material management
alternative, the IDMMS.

Dredge and management schedule for proposed work:
• For planning purposes, an approximate 2-day maintenance event is being used as an
event marker;
• The Murden will be mobilizing from Radio Island to the USACE's Cape Fear River,
Wilmington yard in October and
• CBI maintenance dredging is targeted for the same period followed by the Murden's
demobilization to the Eagle Island maintenance yard and then the Northeast.
IDMMS:
• The IDMMS deposition capacity is below;
• The last IDMMS usage was in March 2021 and
• A post -construction survey and summary will be provided.
IDMMS
NHC Placement -Borrow Area
ESTIMATED PLACEMENT CAPACITY:
AS OF AUGUST 30, 2021
248,289 CY @ 14FT
BOX CUT
Volume estimate of IDMMS placement:
• Ensuring no navigational effects within the CBI Atlantic Intracoastal Waterway Crossing,
the IDMMS accepting capacity tracking will continue. The natural infilling of the
IDMMS and the USACE's position to its continued use as the Carolina Beach coastal
storm damage reduction project's historical borrow site will challenge NHC's inlet/beach
regional sediment management and programmatic approaches. Considering the 30
August 2021 calculated available capacity, NHC is preparing full use of the IDMMS for
this opportune inlet maintenance dredging event.
• The USACE's Coastal Engineering opinion of the IDMMS deposition capacity is being
requested;
• The dredge event is marked for approximately 2 days at 12-hour days. If the Murden
were to produce 24 hours of dredging at —200 cubic yards/hour, the volume managed
would be approximately 4,800 cy, well within the August 2021 surveyed available
capacity.

IDMMS most recent sand recycling:
• The last recycling/reuse of beach quality sand from the IDMMS occurred in early 2019
and was scheduled again for FY22. The latest CBRA interpretation, the USACE's
response and their offshore borrow mandate will impact NHC's future IDMMS
considerations and regional sediment management approaches.
Forecast of next disposal event planned for the IDMMS:
• As per the USACE's upcoming shipyard visits and the fleet's US East Coast
responsibilities, the USACE will continue abbreviated but repetitive visits within NC's
shallow draft inlets;
• The US East Coast scheduling of the USACE's dredge fleet is completely a USACE
responsibility;
• In efforts to meet the USCG's mandate for the buoy tender Bayberry's access, CBI
maintenance is tentatively targeted every eight to ten weeks and
• NHC prefers and requests the USACE's special purpose dredges using the IDMMS,
resulting in improved operational efficiency (reduced dredge plant travel time), improved
sediment management (pre -staged recycling from the IDMMS) and reduced
environmental effects (avoiding surf -zone nearshore nursery areas, nearshore turtle
staging areas as well as whale migration routes).
Given the USACE's special purpose dredge fleets' schedules/timelines and in keeping with the
NCDCM Major Permit 50-16, NHC is requesting the agencies accept this transmittal as NHC's
pre -construction IDMMS communication.
NHC thanks all for your consideration!
H. Layton Bedsole Jr., REM
Shore Protection Coordinator
New Hanover County