Posted on February 27, 2020
Purchasing the future, a Custom-Built Water Injection Dredge for the North Carolina State Ports Authority, Wilmington & Morehead City, North Carolina
Joe Wagner, PE, D.NE[1], Leah DeLeon, PE[2]
ABSTRACT: The North Carolina State Ports Authority (NCSPA) seeks to maintain the authorized depths at all berths, channels, and turning basins of each of the state’s port facilities year-round, thus maximizing vessel tonnage capabilities. The NCSPA has engaged Wood Environment and Infrastructure Solutions, Inc. (Wood) to provide water injection dredge (WID) purchase services for the Port of Morehead City and the Port of Wilmington.
[1] AssociateDredging Engineer, Wood Environment and Infrastructure Solutions, 6256 Greenland Road, Jacksonville, FL USA 32258 Phone: (904) 391-3741 E-Mail: joseph.wagner@woodplc.com
[1] Marine Engineer, Wood Environment and Infrastructure Solutions, 6256 Greenland Road, Jacksonville, FL USA 32258 Phone: (904) 391-3731 E-Mail: leah.deleon@woodplc.com
NCSPA Port of Morehead City
The WID methodology utilizes hydrodynamic principles in a cost-effective approach compared to conventional dredging techniques such as trailing suction hopper dredges, cutter head dredges, and clamshell dredges. Material suspended in the bottom of the water column by WID activities will be fine-grained sediments that have deposited above the authorized project depths. This technique utilizes water from the upper water column of the project site. High volumes of low-pressure water are pumped through a series of nozzles on a horizontal jet bar to disrupt the internal friction and cohesive properties of the sediment to create a fluidized soil layer (density current). This fluidized layer of sediment remains close to the bottom and moves out of the project area into a higher energy system allowing for natural deposition downstream.
The primary benefit of water injection dredging methodology is that the NCSPA does not have to remove the disturbed sediments from the system, which serves to reduce typical costs associated with the NCSPA’s dredging, transporting, dewatering, handling, and storage of dredged material.
Please note that the use of WID methodology NCSPA will not remove any sediment from the waterbody. Instead, all sediment will be carried naturally along the water-sediment interfaceduring an ebb tide cycle. The amount of material relocated from the wharves and channels depends on the duration between maintenance dredging events. NCSPA anticipates that it will use this dredging method as a supplement to the annual dredging performed by the US Army Corps of Engineers (USACE), and the WID is expected to be used between ten (10) to fifteen (15) times annually during the prescribed environmental dredging windows for both port facilities.
Optimally, the WID needs to be efficiently transported between the Port of Wilmington and the Port of Morehead City (approximately 100 miles by land, and 100 miles by sea) to work within seasonal dredging limitations.
The NCSPA has regulatory authorizations in hand for maintenance dredging, including the use of water injection dredging as a primary maintenance dredging technique. These regulatory authorizations allow for dredging during the environmental window of August 1st to March 31st in the Port of Wilmington and during the window of October 1st to January 31st in the Port of Morehead City.
Although the NCSPA was open to purchasing a standardized model WID, if the vessel and its appurtenances meet the specific needs of the facilities served by the NCSPA, none currently exist in the limited US WID market. Thus the NCSPA needs to purchase a custom-built vessel that will fully satisfy the dredging needs of both ports serviced while leveraging local markets and marine design expertise. The NCSPA’s final choice in dredge designer/manufacturer was weighted based on technical criteria, utility, and economy.
The WID will be designed for storage at the NCSPA’s Wilmington facility during the off-season. Logistics of procurement, transportation, and demonstration were all part of the NCSPA criteria for manufacturer selection. Ease of operation, training requirements, and onboard software integration with existing NCSPA data analysis capabilities were all considered in the procurement of a WID. The selected manufacturer/designer is asked to provide the following:
• WID 3-Part Demonstration Plan
– Delivery of the fully equipped WID to the NCSPA Port of Wilmington dockside.
– Execution of a Port operator’s training program
– Demonstration of a full dredge cycle during ebb tides at the Port of Wilmington.
– Demonstration of WID transportation from the Port of Wilmington to the Port of Morehead City.
– Demonstration of a full dredge cycle during ebb tides at the Port of Morehead City.
– A complete report summarizing the Contractor’s executed proof of concept, including pre- and post- dredge hydrographic survey data.
– Modification of the WID plan, as necessary, and handover to NCSPA.
• Commissioning/Procurement Plan
• Operations and Training Plan
• Maintenance Plan
• Service Life Estimation based on Design Operating Conditions
The selected manufacturer/designer will demonstrate that the design has leveraged local markets for raw materials and expertise. The NCSPA is seeking a cost breakdown for commissioning, delivery, training, and demonstration. The following cost line items are requested of bidders:
- Design and Manufacture of WID (with all required appurtenances and onboard analysis equipment included)
- Shipment of Vessel to NCSPA (Wilmington, NC)
- Demonstration of WID
- Wilmington Demonstration
- Transport to Morehead City Demonstration
- Morehead City Demonstration
- Operator Training
