Locals call the coral-ringed lagoon on the north coast of Jamaica Glistening Waters. As night falls, bioluminescent plankton light the shallows. Oyster Bay is believed to be one of only four lagoons in the world where such a spectacle occurs. Not surprisingly, Jamaica’s National Environmental Protection Agency (NEPA) keeps a protective eye on it – and it is within this environment that a pier was built to serve a new generation of cruise ships. We were involved since the project’s inception, advising on navigation, engineering and environmental protection.
The facility was to be designed to simultaneously accommodate two future generation cruise ships, each with a capacity of up to 6,600 passengers. At the time the largest vessel had a 4,400 passenger capacity, making the design ships much larger than any previous development, requiring greater terminal and harbour space.
Our role covered all phases of the development from feasibility through planning and preliminary design to construction supervision and environmental monitoring. At project concept stage our brief included conducting a feasibility study incorporating an environmental impact assessment, full bridge navigation simulation work, planning of the marine works, conceptual design, and capital cost and programme estimates.
Following this our scope extended to development of outline designs for the marine and infrastructure works, preparation of tender documents and management of the tender process for the design and build contract. We then provided on site supervision and duties under the role of the Reviewing Engineer, review of contractor’s designs and technical assistance throughout construction.
Optimising harbour layout
Dredging on any scale changes the flow of currents, with potential ecological impacts. And there was the question of what to do with spoil. This was answered by building a triangular promontory to berth ships against. The shape of the promontory and design of berth layouts were developed with the aid of real time ship simulation in the UK and at the internationally renowned Star Centre in Miami, USA. Real time full bridge ship simulation involved creating a computer model of a proposed port - wave, wind and marine current data were fed into it, making it possible for a pilot to steer a virtual ship into port, assessing the layout and effects of sea and weather on manoeuvrability.
Berth configurations selected for the trials all involved minimum coral removal to widen the navigable channel, while limiting dredge volumes. Simulation of initial layouts revealed that the proximity of the promontory to the reef posed problems: to avoid collision with the quay, ships would have had to move through the navigation channel at very slow speeds. This would make steerage difficult, posing a risk that cross-winds might blow vessels onto the reef. To improve navigability, the channel through the coral reef was realigned slightly and the approach layout modified to create more manoeuvre space, but without increasing the total dredge area.
Protecting the coral reef
Given the terminal's location in the environmentally important Oyster Bay, the scale of the development, and the quantum of dredging required, we needed to ensure environmental impacts were kept to a minimum. To do this, in collaboration with NEPA, our environmental team conceived and specified a programme of coral and sea grass relocation that was incorporated into the project’s licence applications and tender documentation. By putting forward and following through with these impact mitigation initiatives together with an extensive monitoring regime, out of a total dredging and reclamation area of 320,000 m2 we were able to avoid the loss of:
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150,000 pieces of coral over an area of 100,000 m2 through relocation and creation of artificial reefs.
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25,000 m2 of sea grass from within the bay through relocation and planting grass obtained from dedicated donor sites.