Hurricane Resiliency Considerations and Wave Modeling of Four Berths for LNG Powered Cruise Vessels

Abstract: The south coast of Grand Bahama Island, located approximately 50 miles from Florida, is being developed into a cruise ship destination by Carnival Corporation. This location in Bahamas requires deepwater port infrastructure to accommodate cruise ship calls due to the lack of a protected port. The area is subject to frequent coastal storms including the historic 2019 Category 5 Hurricane Dorian. Therefore, development of marine infrastructure in the region poses design and constructability challenges. This paper describes the hurricane resiliency considerations adopted in the design of the new port capable of serving 4 XL class LNG powered vessels and accommodating up to 4 million cruise guests yearly at full buildout.

The primary marine components of the dog-legged port include two cruise berths totaling 2,750 linear feet and two trestle segments totaling 2,000 linear feet. The project layout limits the footprint of dredging which was executed as a standalone procurement ahead of the design-build execution of marine construction. The berths are spatially laid out to allow two-phased construction with two active berths, facilitate barge-to-ship refueling of the four LNG-powered cruise vessels, provide pragmatic operational berthing/mooring conditions, and accommodate coastal loading triggered by the low deck elevation set to accommodate passenger gangways from the cruise ship doors. To develop an accurate assessment of hurricane resiliency, the project team analyzed each of the two berths and two trestle segments to 1000-years of synthetic hurricanes derived from historical wind and wave data. The modeling confirmed that the orientation of the structures with respect to the wind and wave directions and water-depth related wave breaking effects had tremendous impact on hurricane induced loading. The modeling results were used to optimize the deep foundation elements including the cost-and-schedule sensitive drilled rock sockets and simplify the constructability of the precast superstructure units. To maximize the limited construction windows triggered by wave exposure, the design-build team mobilized on two separate fronts including adopting a top-down based approach to construct the precast structure. The marine construction is expected to be completed in 2024 with the port will being operational in 2025.

How does this project / topic contribute to the advancement of the industry and profession?: The project illustrates the importance of master planning and executing adequate site-based studies for developing a safe and guest friendly cruise port located in a beautiful but exposed environment. With the lack of protected ports, port developers are forced to design/construct port infrastructure in exposed locations. The design and construction approach are to address survivability of the infrastructure with exposure to severe tropical cyclones on a regular basis.

Does the project / topic implement new and innovative techniques, materials, technologies, and delivery methods?: The project is being executed via a negotiated phase-wise design-build delivery mechanism. Wave exposure is assessed via probabilistic numerical assessment of 1000 years of synthetic hurricanes developed based on historical data. Adopting this numerically intensive effort was paramount in significantly optimizing the design and providing the necessary hurricane resiliency to the project. The industry continues to evolve with the analysis of wave forces on marine structures to provide for a balanced design that is cost-effective given the exposure to the infrastructure to deep water.

What was the most challenging aspect of your project / topic and how did you handle it to ensure success?: Providing resiliency of the project elements against hurricane events was a very challenging aspect as it required very extensive numerical modeling based on historical data and synthetic generation of extreme events. The other challenging aspect was to configure the layout to allow construction with 2 berths available at all times not only for guest transfer but also for LNG refueling.

Who is the target audience for this paper?: The target audience is cruise line operators, port master planners, coastal and resiliency engineers and experts, and specialty marine contractors.