There are not many more remote places on earth than Marion Island. It sits in the Roaring Forties, some 2,180km southeast of Cape Town, South Africa and 2,300km north of the Antarctic coastline. At 18km by 22km, it is the larger of the Prince Edward Islands group; Prince Edward Island itself lies 19km to the northeast.
The average temperature is 5 deg C, but often falls to minus 12 deg C. The average rainfall a year is 2,300mm and wind speeds can reach up to 80 knots.
Marion Island was annexed by South Africa in 1947. The initial motive was to set up a weather station, but since then a significant scientific and meteorological research station has evolved on the island – part of a whole network of stations across Antarctica and the sub-Antarctic islands.
Over the past 50 years, various buildings have been erected, using different technologies, scattered around and connected by slippery walkways. Many of them have deteriorated to the extent that they now need to be replaced.
Construction of a new research station began in 2003, and is now half way through. It is not an easy project. There is no port on the island. Staff and supplies are transferred by helicopter from a supply ship that makes occasional visits. Building materials and equipment must come the same way.
In addition, the fragile ecology of the island must be respected. The island is South Africa’s only active volcano and last erupted in 2004. It is also home to thousands of penguins, albatrosses, and other sea birds.
The new base will have a total built area of 8,406 sq m. Of this, 4,543 sq m will be buildings that house the functional accommodation requirements. The rest of the area will comprise of covered grid areas, heavy duty and light duty access grids, and covered walkways and bridges. Whereas before it was a difficult task simply moving between the various buildings of the island’s research station, the modern purpose-built station that replaces it will have laboratories, sleeping quarters, offices, canteens, social areas and store rooms all connected to a single hub. The whole facility is built on a galvanised steel grid platform supported by piles that are just 100mm diameter. The piles were driven by hand through the soft surface layer, then clay, until they reached the lava rock beneath. Because the depth of the lava’s surface varied so much, pile lengths varied from virtually zero to 14m.
As with the piles, structural elements are designed to be small enough to be handled and installed without lifting equipment. The new structures are made from prefabricated sections and clad with GRP panels. Every element is numbered (to show where they go in the finished structure) and put onto the supply ship in the appropriate order, for transporting to the site by helicopter. Logistics is everything on this job.
The marshy terrain and the environmental regulations governing the island mean that no motorised construction equipment can be used, explains Michael Murphy, project manager for the South African government’s National Department of Public Works.
There is one exception allowed, however. A pair of rubber-tracked Unic mini-crawler cranes was brought in to help out. These Unic UR-A376CL models have a maximum rated capacity of 2.9t at 2.4m. The six-section boom gives a maximum working radius of 14.3m.
On Marion Island, the Unic cranes only operated on the building platforms, where their 3,530kg weight was within the allowable loading limits. When they were needed on a different part of the site, they were dismantled into three sections, and transported by helicopter – which is how they got onto the island in the first place.
“With the exception of minor adjustments to certain parts of the hydraulic system, caused by vibration, due to long operating hours and severe weather conditions, the cranes have proved very practical and extremely effective,” Michael Murphy reports. “Both cranes operate in these adverse weather condition, and can withstand wind speeds up to 30 knots (± 60km/h) before they become unsafe to handle.”
The construction period was restricted to five months of the year, because of the availability of the supply ship. This five-month period was divided into two sessions, comprising a two-month period between March and May and a three-month period between August and last month. For the rest of the time the cranes were mothballed.
