Monday 19th Nov, 2018

SPECIAL REPORT: Port Design, Construction and Dredging

WHEN 600 people living in a remote archipelago rely on sea transport as their lifeline to the outside world, it is a big concern when their one and only wharf falls into dangerous disrepair.

This is what happened in New Zealand’s Chatham Islands.

The archipelago of 10 islands is 770km from the nearest city, Wellington, and has only two inhabited islands: Pitt Island and Chatham Island.

Residents rely on sea transport to receive essential supplies from the mainland and beyond, as well as to export goods – mostly fish and agricultural products.

Chatham Island’s Waitangi Wharf is the only cargo-handling facility in the islands, making it an essential lifeline. But, the wharf was built in the early 1900s and had become severely degraded.

The wharf’s upgrade project started when the NZ Department of Internal Affairs, on behalf of the Chatham Island Council and Chatham Enterprise Trust, requested that the Memorial Park Alliance – comprising NZTA, HEB, Downer, Tonkin + Taylor and AECOM – deliver the essential upgrade works.

Tonkin + Taylor design manager and senior civil engineer Mark Foster presented a paper on the project at the recent Coasts & Ports Conference held in Cairns.

He said the archipelago was strategically important for New Zealand, its surrounding waters are home to rich fisheries, and has a land area of about 1000 square kilometres, about the size of urban Auckland.

“But only 600 people live there, it’s incredibly remote and they’re a hardy bunch,” he said.

“They don’t call themselves Kiwis, they call themselves Wekas, which is another flightless bird.”

Mr Foster said 60% of the islands’ GDP comes from the fishing industry, and 30% of the population is employed in fishing, and there is also significant farming activities on the islands.

Waitangi Wharf – the islands’ only connection to mainland New Zealand – was built in the 1900s, and Mr Foster said it was particularly critical now because all the fuel for power generation on the islands is imported via the wharf.

“The island would not survive without the wharf,” he said.

Before the project started, the community had been advocating for the wharf to be not just repaired, but also upgraded.

Mr Foster said the wharf could have fishermen unloading their catch at the same time livestock are loaded onto a ship for export.

“Hygiene-wise, mixing sheep and cows with fish was not a great idea, so there was definitely a drive to provide some separation,” he said.

Another issue with the wharf was that the berth was frequently unsafe due to weather.

“When we first started the project anecdotally it sounded like the wave climate was making the berth unsafe 15% of the time,” Mr Foster said.

“But, once we got some data and did some analysis, we found that 66% of the time the wharf had unsafe loading and unloading conditions just because of the roll coming through.”

The wharf upgrade project, which cost a grand total of $58m, included a 180m breakwater (made of 4000 xblocs), 9500 square metres of port operations area, a 105m cargo wharf, a 60m fishermen’s wharf and holding area and tanks for 100 cattle.

It comes as no surprise that the project presented some unique challenges in terms of logistics and also in terms of community engagement.

“How do you get materials to build a $58m wharf when you don’t have a quarry on the island? One of our geologists scoured the island for rock and found us two quarry sites,” Mr Foster said.

“We also had to negotiate with the landowners for the quarry sites, also we had to get some land for a construction site to make concrete.”

Nearly all equipment and materials had to be shipped to the island, which made it necessary for logistics to be considered from the very beginning of the project.

An early design for the breakwater required 5 tonne-10 tonne rock, but finding suitable rock wasn’t available on the island, the project designers decided to use Xblocs.

Mr Foster said many options were tested out in terms of breakwater length as designers worked to find the sweet spot where the cost and effectiveness converged.

Testing of a model of the planned breakwater was carried out at the Sydney Water Research Laboratory.

“We did some physical model testing to prove and verify the model, also in the lab we did physical model testing around the construction aspects of the project,” Mr Foster said.

“There is a small but consistent wave climate out there, and the constructors were quite keen to understand how it was going to form during construction, we sent a construction manager to the lab where we were carrying out the research and he spent a bit of time in there playing around with the lab, getting an understanding of how things were going to behave.”

Throughout the initial phases of the project, the designers and construction team worked together to figure out what could actually be transported to the island, and therefore what could be used to build the wharf.

“At one moment we thought we were going to have to build a ramp to land the barge, so we thought we were going to first have to send a small barge over to build the ramp – it was a bit of a logistical nightmare,” Mr Foster said.

Once the wharf was designed and the nightmares tamed, the issue of personnel had to be considered; the wharf wasn’t going to build itself – there needed to be 30 to 40 staff on the island during the construction.

The solution: rent all the houses available on the island and build temporary accommodation units.

And, this brings us to another issue: working with the island residents.

“Any project has an impact on the community, that’s for sure, but when your workforce suddenly increases the island’s population by 5%, you’ve got to be really cognisant of what you’re doing,” Mr Foster said.

“We increased the road traffic from the quarry to the site by something like 25 times from what it was before.”

But, in the end, the Wekas understood the importance of their port and the wharf upgrade, an awareness that Mr Foster said was lacking in bigger cities.

“I’ve seen in Auckland any port development project is scoffed at by the community and people can be very anti-port development,” he said.

“At Waitangi, the fact that the port is so visible to the community and it’s such an important part of their life, even though they could see that there would be some negative short-term impacts of the project, they got the bigger picture and they were very supportive of this project, and they got what was needed.

“There’s an opportunity there in tying communities and people to the importance of their ports,” Mr Foster said.

“Ports of Auckland is probably equally important to the Aucklanders as the Port of Waitangi is to the Chatham residents, but no one really gets that.”

Construction is ongoing and is expected to be completed by December 2017.

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