Scientist urges noise control at new port berth
A dolphin expert is urging the Lyttelton Port Company to use much quieter screw piling for its new cruise berth to reduce the impact on both marine mammals and local residents.
Otago University professor of marine science Steve Dawson said screwing the piles into the seabed would make next to no noise compared with using a hammer to drive them up to 100 metres deep.
A company that specialises in piling says technology to install screw piles of the size needed in Lyttelton is available, and could be a cheaper option.
Last week Lyttelton Port Company (LPC) said a resource consent application for the berth had been put on hold while it addressed concerns about the impact on the protected dolphins, but it would not say whether screw piles were being considered.
LPC would not say whether it was considering screw piles.
‘‘Once the work has progressed on the cruise ship berth we’re happy to share the details at the appropriate time,’’ development manager John O’Dea said.
Dawson said up to 60 dolphins were routinely present in the harbour over summer and they frequently came up very close to the wharves.
When he and master’s degree student Eva Leunissen monitored the impact of pile driving noise during repairs to Cashin Quay in 2014 and 2015, they found it led the endangered species to avoid the area for significant periods.
Though it was impossible to say what the long-term effect would be, Dawson said piling could drive the dolphins into areas where they risked being caught in nets.
‘‘It wouldn’t normally be thought of as OK to deny an endangered species part of its normal habitat,’’ he said.
‘‘I would have thought that, given the sensitivity around this, and the need for LPC to at least appear to be a reasonably environmentally aware good corporate citizen, they would want to take every step they could.’’
Resource consent documents filed with Environment Canterbury for the proposed berth said driving 60 piles up to 1.2 metres in diameter could take 12 months.
Dawson said that although methods were available to muffle the noise, which travelled five times faster in water than in air, it was difficult to achieve.
‘‘You are hitting this enormous steel tube with an enormous steel weight and it literally rigs like a bell, and that’s the kind of sound that is going into the water.’’
Piletech engineering manager Mike Abbott said his company was approached by consultants working for the port company about 18 months ago to discuss screw piles, which were faster, quieter and potentially cheaper to install.
Piletech had a relationship with a Japanese company that could bring its own rig and screw piles, which had potential to be cheaper, Abbott said.
"It wouldn't normally be thought of as OK to deny an endangered species part of its normal habitat." Professor Steve Dawson