Bogue Inlet AIWW Crossing

PROJECT BACKGROUND

 

Dredging maintenance activities at and near Bogue Inlet and the Atlantic Intracoastal Waterway (AIWW) are divided into two separate scopes of work. The actual navigation project associated with Bogue Inlet extends from the Atlantic Ocean northward through the ocean bar and traverses to the AIWW via the connecting channel depicted on Figure 1. This is considered as the “Bogue Inlet Navigation Project”.

 

View Graphic: Figure 1 - Site Location Map

 

The authorized channel dimensions fluctuate from -6 to -8 foot mean low water to widths ranging from 90 to 150 foot wide, with a total length estimated at 20,000 feet. The U.S. Army Corps of Engineers (Corps) has traditionally maintained (dredged) the project utilizing the government fleet of sidecast dredges (Merritt and Fry) and to a lesser extent, their special use split-hull dredge (Currituck) in the 1980s. The Fry has recently been decommissioned and a new split-hull dredge, the Murden has been added to the government fleet.  The Corps is authorized to follow the deep water channel at the time maintenance activities are conducted. The area referred to as the ocean bar, which encompasses the most seaward 7,000 foot of the project, underwent significant modifications in 2005 as the Town of Emerald Isle and State of N.C. financed the repositioning of the inlet thalweg (deep water channel) to a central position within the Bogue Inlet floodway, equidistant between Bogue Banks to the east and Bear Island (Hammock’s Beach State Park) to the west.

 

The sidecast dredge does not have the capability to place dredged material on the beach or in upland disposal sites, but rather “sprays” the shoal material approximately 100 – 150 foot to the port or starboard side of the vessel and away from the channel. Consequently, maintenance work provides short-term navigation benefits with an expectation that repeated dredging will be necessary to keep the channel at safe navigable depths. The Corps has historically dredged the connecting channel several times per year as needed, depending on shoaling conditions and the availability of government-owned sidecast dredges. 

Figure 1 also depicts the area where the Bogue Inlet Project and AIWW confluence, known as the inlet crossing. Although the Corps has environmental clearances to utilize the government fleet to maintain this reach of the AIWW, they prefer to utilize industry pipeline dredges on a 2-3 year basis. The dredged shoal material is pumped to the westernmost oceanfront shoreline of Emerald Isle indicated as the disposal area in Figure 1. The average dredged volume placed along the beach per event is approximately 45,000 cubic yards (~3,750 dump truck loads of material) and this scope of work is designated under the N.C. AIWW line item within the Corps operation & maintenance account (Table 1). The AIWW has an authorized depth of -12 foot mean low water with varying widths along the N.C. corridor.

 

View Graphic: Table 1 - Historical Dredged Volumes

 

There are several important differences in the dredging methodologies and accounting framework for the scopes of work at Bogue Inlet and its confluence with the AIWW. The ocean bar/connecting channel work (i.e., Bogue Inlet proper) is; (a) executed by the government side-cast fleet with no beach or upland disposal, (b) is performed 2 - 4 times a year, and (c) is under its own line item (Bogue Inlet) within the Corps accounting structure. Conversely, the inlet crossing work is; (a) executed by means of contract pipeline dredge with beach disposal, (b) is maintained infrequently every 2 – 3 years, and (c) is under a separate line item designated for the N.C. AIWW. Also, there are a total of eight inlet crossings across the State and this cluster of projects, along with other shallow draft projects, are usually maintained under a single or series of dredging contracts. The eight crossings along the AIWW in N.C. include from north to south; Bogue, Bear to Brown, New River, Topsail Creek, Shinn Creek, Carolina Beach, Lockwoods Folly, and Shallotte inlet crossings. Because a pipeline dredge is used, the disposal area for each crossing involves an upland or beach target site. A comprehensive navigation project map for N.C. is available here.

 

Project Scope of Work for 2014

 

The next cycle of maintenance work at the Bogue Inlet AIWW crossing that includes concurrent beach nourishment is scheduled for winter 2013-14 and is part of a larger contract including the Lockwoods Folly and Shallotte Inlet Crossings.  The contract was awarded to Southwind Construction and is expected to take between January 1 and March 31, 2014 to complete starting at the northernmost inlet crossing (Bogue) and progressing southwards to Lockwoods Folly and eventually concluding at Shallotte Inlet.    

 

Similar to the 2006 and 2010 inlet crossing work, The Town of Emerald Isle (EI) received regulatory clearances to place the dredged shoal material from the AIWW inlet crossing near the inlet shoreline at the Point rather than the oceanfront disposal area traditionally utilized for inlet crossing work (see Fig. 2 below). The estimated volume associated with the Bogue Inlet AIWW crossing for 2013-14 is approximately 50,000 cubic yards. The proposed fill template for the nourishment reach will be determined “on the fly” as a balance is struck between; (a) the actual volume of sand that is pumped to the Point shoreline, (b) the volume of sand that is lost as part of the hydraulic delivery process (i.e., fine-grained sediments lost to the template), (c) existing bathymetry and shoreline configuration at the time of nourishment, and (d) the area that is desired to be filled.

 

View Graphic: Fig. 2 - Scope of work (2014)
Photo Gallery: 2/7/2014
Photo Gallery: 1/27/2014
Photo Gallery: 1/21/2014

View Graphic: Scope of Work (2009-10)
Photo Gallery: 2009-10

View Graphic: Scope of Work (2006)
Photo Gallery: 2006