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Ice work if you can get it

technical & practice - With the shortlist due soon for a new building at the British Antarctic Survey's Halley station, we look at earlier challenges

The five stations run by the British Antarctic Survey (BAS), which has carried out most of the British scientific research work on and around the Southern Continent during the past 60 years, operate in some of the harshest conditions to be found on Earth.

Of the three BAS stations in Antarctica itself - Halley, Rothera and Signy - Halley is the furthest south and experiences the severest weather conditions. Temperatures seldom rise above zero and are commonly around -10¦C at the height of summer and below -40¦C in winter. About 1.2m of snow fall every year and winds blow at up to 150km per hour.

The station, founded in 1956 and named after the astronomer Edmund Halley, sits on the Brunt Ice Shelf, which is attached to the Antarctic land mass but floats on the sea. It travels about 700m westwards a year.

This location, about 16km from the Weddell Sea, gives frequent clear views of the Aurora Australis, particularly during the three winter months when the sun does not rise above the horizon. The station is operational throughout the year and has about 16 staff who work through the winter, and a further 50 who stay during the summer.

There have been five sets of buildings at Halley since the base opened, and one of the biggest problems faced by all of them has been snow build-up.

The combination of snow quantity, low temperature and drifting results in any structure on the Brunt Ice Shelf being buried relatively quickly, and the first four stations at Halley were all designed to allow for this. The first two stations comprised fairly traditional buildings with pitched roofs built directly on the ground, while for Halley 3 and 4 the buildings were housed in tubes (steel in the case of Halley 3 and wood for Halley 4) to provide greater strength and insulation. All four designs required the buildings to be accessed and interconnected by ramps and shafts as the snow enveloped them. When Halley 1 was abandoned after 10 years, it was 14m below the surface.

The essentially subterranean existence produced by building directly on the surface in the interior of Antarctica prompted a number of attempts to find an alternative. In 1969, Australia opened a new station with buildings elevated on scaffolding, which lasted for 20 years. However, this was built on rock, not on a floating ice shelf. In 1982, Germany built a small station on a jackable platform. BAS adopted the same solution for Halley 5, the current station, which came into operation in 1990.

Designed for BAS by the German company Christiani and Nielson, the original Halley 5 consisted of three separate buildings on jackable legs set initially between 4m and 5.5m above the surface. The biggest of the three buildings, known as 'Laws', is 900m 2 and contains living, sleeping and technical-support spaces supported on 20 legs, while the other two, measuring 140m 2 and 185m 2, house laboratories. All three structures are built of prefabricated panels and have flat roofs and triple-glazed, nonopening windows.

Generators running on aviation fuel provide electric power, with heat recovered from their cooling systems used to create comfortable working conditions for the staff and also to heat the 15,000 litre-capacity snowmelt tank that provides all the station's water. The above-surface design concept has brought several benefits, particularly improved accessibility and a more normal working and living environment for staff.

In order to keep the platforms clear of the snow, which can drift several metres annually around the structures, they are lifted each year by electric screw jacks and reattached to the steel support legs, to which extensions are bolted. At the same time, the support legs are realigned to correct for distortion caused by differential movement of the ice shelf below.

Parky space While the three main structures for Halley 5 were being built, BAS was already considering the design of a garage and servicing facility for the vehicles at the station. On this occasion it was decided to mount the building on skids, so that it could be towed by bulldozers and relocated on top of the snow once or twice a year, as necessary. The detailed design for the building was carried out by Yorkshirebased consulting engineer Bennett Associates, and it was built by VM Fabrications, also from Yorkshire.

The completed building, which came into use in 1993, is 16m long, 9m wide and 6m high, and is able to house vehicles weighing up to 15 tonnes. The main access doors provide an opening approximately 5m x 5m. It is fully self-contained and includes heating, ventilation, water, electric power and compressed-air supplies, provision for waste water and oil, and also various workbenches, storage and lifting equipment. An internal temperature between +10¦C and +15¦C can be maintained, despite external temperatures as low as -55¦C.

In order to allow the building to be moved from one position to another on the ice shelf before it becomes icebound, the garage has been mounted on a pair of skids, 19m long x 0.6m wide, with low-friction coatings. The skids are fully integrated with the structure to increase mechanical strength, and the building overall is designed to be extremely rigid so it retains its squareness, resisting torsional deflection, despite being towed over uneven ground. It weighs around 55 tonnes and can be pulled by bulldozers once the skids have been broken free of the ice by inflatable airbags.

Bennett designed the garage in modular form with the minimum number of components and fixings, so that it could be handled and assembled easily by staff at the Halley base. No special tools were needed, and fixings were a convenient size to work with, given that staff wear thick gloves virtually all the time when outdoors at Halley. The building itself and all the services and fittings have been designed for minimal maintenance because of the cost of transporting materials to the Antarctic and the difficult working conditions.

When Halley 5 was built it was designed to accommodate about 40 people - 20 year-round staff and another 20 or so in the summer. With the higher than planned number of summer visitors, steel-framed insulated fabric structures were used to provide extra accommodation. However, these had a relatively short life and were costly and time-consuming to keep in a usable condition.

In 1994, following the success of the garage, BAS commissioned Bennett Associates and VM Fabrications to design and build a permanent, self-contained structure with sleeping accommodation and mess-room facilities, complete with power and heating, furnishings, catering equipment and storage. This was again to be mounted on skids so it could be relocated as necessary.

Measuring 17m long x 8m wide x 6m high, the Drewry building provides accommodation for 30 people on two levels, with the ground floor housing the cooking and dining areas, clothing and food storage, WCs, laundry and the plant room, while the bedrooms are on the first floor. The internal temperature can be maintained between 17¦C and 20¦C.

The building weighs 45 tonnes, including all fixtures and fittings, and is usually relocated twice a year. The design and size of the skids and the relocation procedure are very similar to those for the garage. Because of the short Antarctic summer and the need to minimise disruption to the base's work, BAS set a target time for assembly, fit-out and commissioning of 14 days and also specified that no single item could weigh more than 1,500kg.

Before the building was packed for shipping, it was fully assembled and approved by BAS. It was first used during the 1994-95 season.

Elsewhere in the Antarctic, the concept of jackable buildings is still regarded as the optimum solution and is being used by the US National Science Foundation in a £100 million project to replace its Amundsen-Scott station at the South Pole. By employing snow-drift control, the designers of these new buildings believe they will only need to be lifted twice during their projected 25-year life.

Mark Pickering is a freelance journalist. Photographs supplied by the British Antarctic Survey, Cambridge. For further information, call 0114 266 4668

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