LYTTELTON Port of Christchurch’s new cruise berth is being designed with dolphin safety in mind.
LPC chief executive Peter Davie said the welfare of Hector’s dolphins, present in Lyttelton Harbour, had been a major priority when considering the construction methods for the new cruise berth.
“We have worked with designers, engineers and marine mammal experts to develop a cruise facility that reduces effects on marine mammals,” he said.
“To manage any other effects, we will also implement New Zealand’s most comprehensive marine piling management and monitoring program. We are fully aware of the effect underwater noise from piling can have on dolphins. This was a key reason for the wharf’s redesign.”
Mr Davie said LPC had worked with its consultant AECOM’s acoustic engineers, who confirmed that the new design significantly reduced underwater noise.
“Modelling shows underwater sound energy per pile is 100 times less and the potentially affected area of the harbour has reduced by over 90%,” Mr Davie said.
“The original design of the cruise ship berth called for piles 1200 mm in diameter; however, further acoustic modelling revealed that the effects of noise from piles this size on Hector’s dolphins would be very difficult to manage, therefore we have redesigned the wharf accordingly.”
Mr Davie said reducing the size of the wharf reduced underwater noise levels, and the piles now being used are 900 mm in diameter, reducing pile-driving noise underwater.
“Due to the deep and soft muds and instability of the land during earthquakes, there were limited piling options available,” he said.
“LPC and our design engineers, BECA, considered all piling options, including screw piles, which would not feasibly be able to provide the strength required to create a seismically resilient wharf that is able to berth larger cruise vessels. Driven tubular steel piles are the most feasible option for wharfs in Lyttelton, such as the cruise berth,” Mr Davie said.
LPC has collected more than a year’s worth of data on the movement of dolphins around the harbour using four acoustic monitoring buoys.
This year LPC installed four additional acoustic monitoring buoys adjacent to the cruise berth – and installed additional underwater devices to record the total level of noise in the harbour. This will help evaluate the level of noise due to piling.
Peter Davie said: “As with any expansion project, our priority is to ensure we achieve a balance of what is best for the environment, our community and the growing regional economy.”
According to the WWF, Hector’s dolphins are endemic to New Zealand, with a total population of about 7000 in three populations around the South Island, with a subspecies, Māui dolphin, in the North Island.