Cruise berth re-designed to minimise noise impacts on Hector’s Dolphins
Lyttelton Port Company (LPC) Chief Executive Peter Davie today re-confirmed that the welfare of Hector’s dolphins, present in Lyttelton Harbour, has been a major priority when considering the construction methods for the new cruise berth.
Peter Davie said, “We have worked with designers, engineers and marine mammal experts to develop a cruise facility that reduces effects on marine mammals. To manage any other effects, we will also implement New Zealand’s most comprehensive marine piling management and monitoring programme.
“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. We are very happy to meet with any organisation or individual to take them through the very careful and detailed assessment we have undertaken to ensure our plans do not adversely impact any marine mammals in Lyttelton Harbour.
“Throughout the design process we have worked with our consultant AECOM’s acoustic engineers, who confirmed that the new design has 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%,” says Peter Davie.
“The original design of the cruise ship berth called for piles 1200mm 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.
“Reducing the size of the wharf has significantly reduced underwater noise levels. The piles being used are now 900mm in diameter, which significantly reduces the pile driving noise underwater.”
The new, significantly smaller wharf design, does not require resource consent for construction, as it is within the regulations of the Lyttelton Port Recovery Plan. However, LPC has applied for consent to allow the larger cruise ships to berth at the wharf, and to undertake minor dredging works. This consent is currently in progress with Environment Canterbury (ECan).
“Due to the deep and soft muds and instability of the land during earthquakes, there were limited piling options available. LPC and our design engineers, BECA, did consider 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,” says Peter Davie.
LPC’s Chief Engineer Neil McLennan says he confirmed with New Zealand’s main screw pile contractor and specialist that screw piles would indeed be unsuitable for the cruise berth.
Even though consent isn’t required, LPC will implement similar marine mammal mitigation measures that were developed and approved in the hearing process of the new container wharf at Te Awaparahi Bay.
This month piling commenced on land, with piling in the sea commencing in September and strict environmental controls will be enforced.
The Port is working with Marine Mammal Expert and Researcher, Dr Deanna Clement, to finalise a Marine Piling Management Plan to further mitigate the remaining levels of underwater effects on Hector’s dolphins, such as:
Soft starts with power gradually increased at the beginning of the day and after any break in piling. This will allow marine mammals to vacate the area before the full energy is applied to the pile.
- A safety zone around the works with designated and trained observers helping to ensure marine mammals are detected within the safety zones. If a marine mammal is spotted within the zone, piling cannot be undertaken.
- Establish appropriate measures to log dolphin sightings.
- Control all vessel movements in proximity to marine mammals.
Using four acoustic monitoring buoys, LPC, with the help of the Styles Group and Vision Environment, has been able to collect more than a year’s worth of data on Hector’s dolphins’ movements around the Harbour – day and night, in both fair and inclement weather conditions.
Dr Deanna Clement describes the acoustic monitors like a microphone under the sea, as they listen to the frequencies that Hector’s dolphins echolocate at, which tend to be comparatively high.
This year LPC installed four more 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.