“Some days, the temperature dropped to minus 42 degrees with wind chill thanks to 25 knot winds. They were very challenging conditions. We were rugged up, but any part of your skin that's exposed instantly freezes,” says the Christchurch-based engineering geologist.
"It can be difficult to think in such extreme conditions, so it was important we kept up the communication - taking the time to step back and run through how we’d complete our drill tasks.”
Latasha was working with Antarctica New Zealand and a crew from Websters Exploration and Drilling to understand more about ground conditions for the replacement of the Ross Island Wind Energy Network. The three existing wind turbines which power Scott Base and the United States’ McMurdo Station are set to be replaced with three larger, more powerful ones as part of the Scott Base Redevelopment Project .
All up, the team drilled seven holes near where the new turbines will be sited. They encountered lots of ice and basalt – an extremely hard volcanic rock.
“We were investigating the stability of the ground, what it’s made of, and weaknesses that will need to be considered when loading massive turbines onto it,” says Latasha.
Working four-hour shifts before heading back to base for warmth and food, the team used a drilling technique that saw super-cooled compressed air forced down drill pipes to extract core samples. The method keeps the drill bit cold and the core frozen. They encountered several significant ice lens’ - a geological phenomenon where layers of crystal-clear ice form between deposits of rock.
“From a geological perspective, we're interested in that rock / ice interaction. We’re looking at the implications of having ice in the ground, what that does to the ground when it’s loaded, and how it might influence the turbines and their foundations,” says Latasha.
“Volcanic deposits follow their own pathways. They aren't uniform, so being able to pinpoint ground conditions in the area is extremely important. The ice and glacial history add another level of complexity.”
Standing in the teeth of savage Antarctic storms, the forces acting on the new turbines will be immense. To stay upright, they need to be well anchored. For this reason, the team also installed some trial ‘anchors’ – fixing them in place with low-temperature cement / grout and a special blend of sand and water.
No thanks to the weather and fractured ground, the team experienced good and bad days on-site. They managed to drill twelve metres in one day – but there was a three-day period where they could only eke out three metres.
Their core samples are now back in New Zealand being tested and analysed. Information from the drill programme will be used to help decide where to place the turbines. It will also help WSP’s foundation designers craft suitably strong and stiff structures.
Latasha enjoyed the drilling process, but her trip wasn’t all ‘boring’! On Scott Base’s Sunday rest days, she got the rare opportunity to meet a waddle of emperor penguins, tour historic Scott’s Hut, and learn how to bridge cracks in sea ice on an all-terrain Hägglund vehicle. She even had a quick chat with Prime Minister Jacinda Ardern who happened to be visiting at the same time.
More information about the Ross Island Wind Energy Upgrade can be found here on Antarctica New Zealand’s Scott Base Redevelopment website. More information about WSP’s work at Scott Base is here.