As the final piles go in on a giant cruise ship berth in Lyttelton Harbour, there's concern long-term damage to local Hector's dolphins could become apparent.
Hector's dolphin. (File image). Photo: Gary Webber/ 123rf
Residents and researchers who worry the noisy construction work has affected the dolphins' hearing and behaviour, vow they'll keep trying to hold Lyttelton Port Company accountable, after a year and a half lobbying against its work.
The company says there's been no damage to the dolphins, thanks to its constant monitoring and "world-class" protection marine mammal management plan.
However, Christchurch resident Genevieve Robinson has clocked up five presentations to the Banks Peninsula Community Board about what she sees as shortcomings in that plan.
She said her views were shared by scientists and even some people working on the project who she had talked to.
"Lyttelton Port Company - and Lyttelton Port - it's the only industrial harbour in the world that holds daily dolphin visits. They're in a position of great privilege and they should respect that," she said.
The marine mammal management plan involves constant acoustic monitoring under the water, and one marine mammal observer watching dolphin activity from above the water at all times.
Blue Planet Marine Scientist Lesley Douglas helped organise the observers and said they were watching to see if a marine mammal came within a certain distance of the piling activity.
"Depending on exactly what was going on with the piling, they'd either need to shut the piling down or stop it from starting up, until the marine mammals were at a distance outside of what we term mitigation zone," she said.
Environment and planning manager Kim Kelleher said to date, work had been put on hold about 100 times because of that happening - a feat she described as "pretty amazing" for a large construction project.
She said before the project started, the berth was completely redesigned to minimise impacts on sea life - and there was no evidence of the Hector's dolphins being scared off or harmed.
"We're incredibly proud of raising the bar in New Zealand, for the standard of ensuring marine mammals are protected on construction jobs. We went to great lengths to work with specialists," she said.
Lyttelton Harbour. Photo: 123RF / Gary Webber
But Otago University professor of marine science Steve Dawson said the company could have tried noise-reducing methods like screw pile driving, or bubble curtains, if it really wanted to minimise the impacts.
It had considered screw pile driving but eventually deemed it unsuitable.
Dawson has also helped with studies linking marine piling to a significant drop in numbers of nearby Hector's dolphins, and finding adverse effects on their breeding and feeding behaviour - even when the marine piling was on a much smaller scale.
He believed even the best marine observers wouldn't be able to spot every dolphin.
"The fact that they might have stopped the pile driving 100 times in that period suggests to me that there an awful lot of times dolphins were close enough to potentially damage their hearing, that they didn't know they were there and they didn't stop the piling and that the hearing on those animals could be compromised."
Robinson said this could set a poor precedent for other companies.
However, Kelleher was confident the cruise ship berth had changed the marine projects that were approached in New Zealand for the better.
Lyttelton Port Company said there were about 20 piles to be installed by April and it would take about four to six intermittent days of work to put them in.
The berth is due to be finished by the next cruise ship season, starting in October.