Author: Alex Conacher

Today the British Antarctic Survey’s Polar Science Programme is invaluable to solving some of the most significant problems facing the world. Its research facilities are all in remote and inhospitable locations meaning that as well as conducting research in all fields from atmospheric science to marine ecosystems, BAS is also an extensive logistics and supply machine. It operates cargo ships and planes, and all manner of support vessels and other infrastructure. One of its main bases and logistics hubs in Antarctica is Rothera Research Station.

Rothera is a centre for biological research and a hub for supporting deep-field and air operations. It’s built on a rocky point at the southern tip of Adelaide Island to the west of the Antarctic Peninsula. That’s about 1,850km south of the Falkland Islands. The island is 140km long, mountainous and heavily glaciated. In the summer it can reach a balmy 5°C, but its coastal location means it is spared the worst of the Antarctic temperatures, dropping to a moderate -20°C in the winter. The 100-strong summer team and 22 personnel who form the winter skeleton crew share the landscape, depending on the season, with penguins, gulls, elephant seals, orcas and even humpback whales.

RRS Sir David Attenborough 

Most people arrive at Rothera by air, landing at the air strip in the rugged Dash-7 aircraft. But the majority of supplies have been delivered by special BAS logistics vessels to Biscoe Wharf, which was built in 1992. But as the wharf approached 30 years of use, iceberg strikes and inclement weather had begun to take their toll, and the wharf was showing signs of wear. That, and a very special ship would need new facilities if it were to dock at Rothera. The RRS Sir David Attenborough needed deeper water and a longer wharf to unload its cargo. “It’s all about how do we get people there safely, look after them well when they’re there, and then help them to carry out the essential science that we need, which helps us understand our planet a lot better,” says David Seaton, head of construction at BAS. He is a civil engineer and is responsible for delivering infrastructure projects for the organisation, which he joined around six years ago. “In 2014, the government announced that they were going to be funding a new polar research vessel, which is now called the RRS Sir David Attenborough,” explains David. “And at the time, it was appreciated that there was a need to develop the infrastructure at Biscoe Wharf to be capable of taking this new ship.”

The Sir David Attenborough is one of the most advanced polar research vessels in the world, and its £200 million price tag represents the UK government’s largest investment in polar science since the 1980s. It will support science in extreme environments, as well as provide direct logistical support to BAS bases. Its specifications are breath taking at 129m long and 24m wide for a mass of 15,000 t. It can operate at sea for up to 60 days or to a range of 19,000 nautical miles at a 24 kph cruising speed, which is enough for a return trip from Rothera all the way to the UK. It can break ice up to 1m thick at a speed of 5.6 kph… it has bow and stern thrusters for dynamic positioning in challenging conditions. It has a crew of 30, accommodation for 60 scientists and is equipped with aerial and subsea robotic drones.

Boaty McBoatface

It has a special place in the British imagination, when the poll to name the ship went viral. The Great British public voted to call it “Boaty McBoatface”. While it was decided that this was inappropriate for such an important and serious piece of kit, the event still fired public interest in polar research. In the end, they did name one of the robotic submarines “Boaty McBoatface”. 

David explains the plans to accommodate the new ship. “What the new wharf has replaced is a smaller wharf called the Biscoe Wharf. And this was put in by a Canadian company Paley construction who BAS contracted about 30 years ago when they built the runway,” he says.

The runway was about 900m long and the Biscoe Wharf was about 60m, which David says was about the limit of the abilities of the Rothera site at the time. “Because at Rothera, the seabed slopes off very steeply. The rock is quite difficult, it’s very hard, but it’s highly fractured. So it’s quite difficult to actually build a wharf on the edge of this cliff, under water.” 

The new wharf is 14m longer reaching a total of 74m out to sea, and although it doesn’t sound like much, the sea becomes deep enough for the Sir David Attenborough to dock. It is a significantly bigger structure. About 14m in total height at the very end. So what enabled the modern team – which comprised BAM Nuttall, Ramboll and Sweco to build it? “We had bigger cranes and excavators. So we had 29-metre-long boom excavators, which were bigger than they had in those days, there were a couple of 300 tonne crawler cranes as well. So that’s some really quite big plant, which allowed us to get that extra reach,” says David. 

Plant that due to the expense of transportation, has to stay in Rothera for the duration for the project, which lasts several seasons and is carefully ‘winterised’ – involving packing and oiling – to make sure it survives the harsher months during which there are no construction works.

Avoiding pollution

The structure itself has to be constructed in a way that enables the site to be returned to its original condition. “It’s a gravity structure tied back to a retaining wall. And the actual pinning into the existing seabed floor is really just to resist a bit of uplift force. So they’re relatively small connections,” explains David.  “At some point in the future, we will have to remove this and it means that we will be able to remove this pretty much completely.”

The main elements are steel sheet piles and beams and tie rods. Rock was quarried locally. So there was no foreign material in terms of the fill brought in it was all indigenous rock. Such works have to undertake an incredible amount due diligence around biosecurity and environmental impact. Even something as commonplace as cardboard is a known problem and might carry insects or spores. A ship might even be carrying something even worse; rats. A few years ago South Georgia spent a large amount of money eradicating a rat infestation. 

The project also has to be careful about the people it brings – accommodation is at a premium, and so niche skills can be prohibitive to source. But all of this has been enabled by the skill of the engineers, rigorous planning and a progressive contract structure that is also relevant to work in less unique environments.

All of this means that designing in Antarctica is surprisingly different to designing structures back at home. And the solutions are often counterintuitive. Bruce Wulff, is the project manager for Ramboll, which has a 10-year framework agreement to provide early design work for the British Antarctic Survey’s projects. “There’s not so many Antarctic specialists out there in the world. And there’s not always design codes to follow either. But luckily, the clients, BAS have been in Antarctica for over 60 years,” says Bruce. This means that their client has a great deal of know how on how to transport, build, operate, and maintain buildings in the polar regions. They are also aware of how the weather and the sea ice and the icebergs behave. “So when designing structures in the south, we have to spend a lot of time listening, which is basically what we did for the first two years listening and learning from BAS.”

Iceberg behaviour 

Stewart Cragie, is technical director and design lead for Sweco, which worked in partnership with Bam Nuttall to build the wharf. He says that BAS expertise informed them on a range of challenges they would face on the ground… for example, the make-up of icebergs. “The behaviour and movement of icebergs for the wharf was an extremely significant part of the development design. But also the conditions that we can expect with the sea ice,” he says. Something which surprised the team was that the sea ice is actually different in Antarctica, to that in the Arctic because it has very low salinity in the upper water column. The significance of a low salinity content is a higher freezing temperature. “But it also means that the performance of that ice is different,” says Stewart. “Ice characteristics change over the number of years that it’s been in existence. So first year ice is much softer than mature ice. So if we’re just dealing with something that’s going to end up with sea flow ice, then the crushing forces at a lot lower than if it’s glacial ice that’s coming in in large lumps.” 

So an iceberg impact transmits a greater pressure, than flow ice impact, for example and this can be taken into account in elements in the structure, based on the type of ice it is likely to encounter.

More generally, Bruce and Stewart have developed a series of philosophies for designing a structure in the polar region. Bruce says that it must be easy to maintain and robust. “What you’ve got down there is basically a very small village in Rothera, you know, 100 people in the summer 20 people in the winter, you don’t want to be creating a structure that is going to be very time consuming, or expensive to maintain, or indeed require very specialised skillset,” he says.

This means that a sustainable balance has to be found between innovation and simplicity. Elements that require specialist technicians are no good.  Stewart adds three design criteria, that it must be practical, predictable and repeatable. “It means you front-load, the design and the planning to assess in constructability terms, how you’re going to put something together in Antarctica,” says Stewart. The design and construct team sits together, and take the challenges that they know, and introduce them intro an environment that they do not know. 

“What’s the challenges we know that we’ll need to address? What are the ones that are new and introduced by what we’ll see in Rothera. And then how do we make this design practical in that environment?” says Stewart. “And then we came up with a selection where we opted for one in particular, and then we went into a very thorough assessment of the elements within that structure that we would need to focus on, where we could remove the most risk. And then how we could turn it into a task that happens again, and again. So that’s the predictable repeatable part of it.” 

Modular construction

The structure itself is modular. A series of 20 steel frame boxes, 10 along the front of the wharf and 10 along the back. To reduce complexity of installation on site, the number of bolted connections were minimised and were prefabricated in yards in the UK, before being shipped out. Fewer and larger connections was the rule. At the site itself, three teams worked in a kind of assembly line. A team on the wharf installing the boxes, a team working further up the site constructing the boxes in assembly jigs, and a team further up supplying the assembly jigs with steel. 

“Most people’s idea of Antarctica is that it’s very far away and very remote,” says Bruce. “And that’s key to a lot of what we’re talking about here as well in that we’ve got to get it right first time, you know, sort of value over costs in that if you if you haven’t got every single nut and bolt on the ship, or if you suddenly realise that something doesn’t quite fit when you get down there. It’s very costly and very timely to, you know, to mobilise some more equipment or some more people.”

Sheet piles protect the side of the frame and it is rock filled, provide passive resistance to small iceberg strikes. So the strike impact is taken by the rock matrix and is not relying on the bending moment capacities of the steel. “Similar to the old existing design, there was a mid-wall retaining wall and a back wall retaining wall that the front sheet vault was tied to. And then it was, you know, some small piles drilled into the seabed as well, just to pin it to the ground and stop any uplift,” says Bruce.

The old wharf had to be able to resist loads from icebergs weighing 7,000-8,000 tonnes, which is roughly the weight of the older vessels that docked at Rothera. This is because icebergs displacing more would ground out, hitting the bottom of the seabed and stopping, before they impacted the wharf. A lucky quirk of nature and the location. In any case, the structure was able to resist these impacts passively, although requiring maintenance now and then. The new wharf at Rothera reaches 14m further out and will allow the 15,000 tonne Sir David Attenborough to dock. This also puts it in the path of far larger, 15,000 tonne icebergs travelling at a knot, or 1.8 kph.

Deeper water, larger icebergs

Stewart explains that the only distress the existing wharf had shown was significant deformation of the corners, which were due to a spread collision. “We were pushing into this structure out about 7-8 metres further into deeper water from where the previous structure had been, therefore putting it into a flow channel of larger icebergs, so the risk of damage was multiplied quite significantly from the massive structures that could hit the existing Wharf. And this is something you just will not find in textbooks is how to absorb the impact of a large iceberg into a structure.” 

There are structures remotely at sea that can deflect icebergs and have foundation structures that can withstand that, but Rother Wharf will be taking the impacts squarely. There is nowhere to deflect the iceberg to. “15,000 tonnes hitting something that is quite an impact. So the way that a normal marine structure would absorb pressures like that is have a fendering system in the front.”

And as it deflects, it creates a reaction force through the absorption material that’s in the fendering system. And then that effectively slows and transfers the load. And then it will steadily push back. A bit like the bumper on your car. Unfortunately the team could not have anything attached to the wharf due to the risk of it being swept away or damaged by ice flows in winter. The team had to do something special. “So we designed the whole berthing face to deflect and therefore, it would pass the force of the impact, pass the steel into the stone mass behind it,” says Stewart. “So it would make the structure behave like a sandbag, rather than, like a rigid structure.”

The expectation then is once it does deflect, it’ll only deflect a very small amount, measured in centimetres at most. The design intent is that then over time, if you do get a deflection the sea coming in a structure creates a hydraulic compaction of the material that’s within it. So that hydraulic compaction is then expected to bring the structure back into its position to then absorb the next deflection. The iceberg collisions happen very occasionally. A big one maybe once every few years. Small icebergs hit regularly and the passive resistance will take care of that, but the larger ones will activate this system. “And therefore the structure can find its balance, again, just through the one you know the action of the tide, creating hydraulic compaction within the structure to bring it back to its starting position,” says Stewart.

Managing the unknown

Martha McGowan is project manager for contractor Bam Nuttall. Her role was to deliver the wharf successfully, safely and on time.  This meant that she had get to grips with the unusual environment probably more than anyone else. It began with pre-deployment training at the BAS facility in Cambridge. “And then the journey in itself was quite incredible, to be honest,” says Martha. 

“Generally there are a couple different ways to get in there. People go on commercial flights all the way to Punta Arenas in the south of Chile. You can also go via the MOD flights from Brize Norton in the UK, to the Falklands. Or you could go by ship takes a little bit longer then and then once you’re there, there’s the BAS aircraft called the dash seven, which takes you there last final bit. That’s a little I think it’s a four-propeller plane,” she remembers.

It is not a memory that Martha is likely to forget. “The pilot told us once that it can run off fewer than four propellers, and one of them cut out. I’ll remember that afternoon for the rest of my life.”

Martha already knew that the work couldn’t be completed in one construction season, which lasts six months. “The first one was the end of the Antarctic kind of summer, I would say roughly sort of November to April or November to May time. And that was when our team was out there. So it was the end of 18/19. Then November 19/20. And yeah, the majority of the team needed to be there for the for the full five, six months to deliver the works. 

The first big event after getting established on station was the arrival of the materials and plant. 

“I would say 95-98% of all the materials and plant were on that first commercial ship so that we could offload it onto the structure before we dismantled. And we no longer had a main berth for a couple of years. So it was a bit of pressure to make sure that everything was there on that ship! And I think there was about four and a half thousand tonnes of kit on the ship. And that all needed to be offloaded.”

Of coursethis is not a commercial port with stevedores and forklifts and staff to unload the ship, the job falls down to the people who are already there, like everything else. It was a 24 hour operation over a couple of weeks. So how did Martha approach the iceberg risk during construction?

“We knew it was a risk. A pretty low probability, high impact risk if it did happen. Some of these icebergs, you know, people describe them as big as football pitches. And it’s hard to imagine until you see some of them offshore.”

And Martha did see one. “I remember one evening, one of the things that people used to do for recreation was just go for a walk up and down the runway, and they got to the end of the runway, which was just beside the new structure.” Martha’s heart sank. “There was a pretty big iceberg kind of floating about looking as if it was heading for the partially built structure. And that was when it was in its most fragile state. I looked up at our foreman and was on the hill, and he was looking at it and one of our gangers was across the other side, and he had his eye on it. And so I thought there’s not much any of us can do about this.”

Thankfully it didn’t hit the structure.

Long term contracts

Many of the challenges for this project came from the extremes of the environment, but the challenges forced the teams involved to turn to a progressive approach to achieve success. And it all started with a requirement for longer-term contracts than usual. Here is David from BAS again to explain. “A lot of places, including the government funded projects are very keen on having competitive tension, and they’re always wondering about value for money. And so generally speaking on the government funded projects, you can only place them for up to four years.” 

Whereas some of BAS’s projects take the better half a decade to complete, due to the short working window, the logistical constraints and the need to winterise. This means longer contracts. “But the bigger thing is that because we are delivering projects, fully integrated with the BAS normal operations, we need to make our partners part of BAS. And that’s very difficult if your partners are chopping and changing all the time,” he says.

It’s also difficult if you’ve got more than one supplier for items. “So we argued very hard that the best model for us was to have one technical advisor, and one construction partner. And, you know, after a bit that was accepted because of the particular environment, we’re working in the logistical challenges, the biggest risks that this was a sensible thing to do,” 

To place long-term single-source contracts. Because the cost landscape is different for such a remote site. “By far, the biggest extra cost we would have on any project would be if we’ve got to go back and fix things, if it doesn’t work, it costs us a lot of money to go back and fix them. So we do a lot more planning than projects would normally do back in the UK.”