A paper presented at the 10th International Cold Regions Conference, 16-19 August 1999, The Mountain Club on Loon, Lincoln, New Hampshire, USA Elevated Station Design for the South Pole Redevelopment Project at Amundsen-Scott South Pole Station William D. Brooks, AIA1 Abstract Historically, the facilities of the Amundsen-Scott South Pole Station have been designed as below-surface structures. Within several seasons of their initial construction on the surface, they drift over with snow and except for pedestrian and vehicular access points which are manually cleared, remain buried. Despite the potential advantages of facilities designed to remain elevated above the snow surface, such construction has until now, been limited to smaller ancillary buildings. To remain permanently above-surface, structures at the pole must be designed to overcome both the localized snow drifting issues that they cause, and the annual accumulation of snow at the site. The current redevelopment of the Amundsen-Scott South Pole Station represents the most ambitious attempt by any nation to establish a significant above-surface facility in an environment such as the South Pole. This paper will discuss the rationale for the development of permanent above-surface facilities at the South Pole Station, examine previous examples of such structures that have been, or are currently operational in Antarctica, and review the features of the new Amundsen-Scott Station that qualify it as being state-of-the-art in South Pole elevated station design. 1 Director of Architecture, Ferraro Choi And Associates Ltd 733 Bishop Street, Honolulu, HI 96813-4016 http:\\www.ferrarochoi.com 1 Background The first International Geophysical Year, conducted in 1957-58, triggered the construction of numerous research stations in Antarctica. By 1980, there were 34 year-round stations maintained by 12 different countries: Argentina (8), USSR (6), United Kingdom (4), United States (4), Chile (3), Australia (3), Japan (2), South Africa (1), New Zealand (1), Poland (1), and France (1). The majority of these stations are located along Antarctica’s coastline and constructed on grade using traditional cold regions techniques. Some Stations, however, have been established on the permanent ice shelfs or further inland on the interior plateau, most notably the U.S. Amundsen-Scott Station, which is located at the geographic south pole. For these non-coastal stations, Antarctica’s environmental conditions pose significant challenges, and traditional cold regions construction techniques are seldom adequate to cope with them. The primary challenges for stations located on the ice shelfs or further inland is annual snow deposition. With no frost cycle, snow accumulates year after year, ultimately burying structures built on the surface. Strong prevailing winds often hasten the burial process by contributing drifting snow on and around structures. To overcome this problem several countries have experimented with innovative above-surface “elevated” stations, initially constructed 3 to 5 meters above the snow surface, and often incorporating a means of periodically raising the buildings to keep ahead of the ever accumulating snow. The redevelopment of the U.S. Amundsen-Scott Station, currently in the beginning phases of construction, will include the largest and most ambitious example of an elevated station in Antarctica. Scheduled to be fully operational in 2005, with a winter-over population of 50, the new station will set the standard for many years to come. The next several sections of this paper gives a brief history of elevated stations constructed in Antarctica to date, followed by a discussion of the Amundsen- Scott station’s design. Old Casey Station (66° 17’S, 110° 32’ E) Although a number of Antarctic coastal stations have employed the idea of a pier- foundation to allow for the seasonal scouring and control of drifting snow, the first emergence of a truly “elevated” station was Australia’s Casey Station. Located on the shore of the Bailey Peninsula in Vincennes Bay, Casey Station was constructed to replace Wilkes Station, approximately two kilometers away, and became operational in 1969. Originally a U.S. station, Wilkes had been constructed in a topographic hollow. Over the years, snow that didn’t melt built up around the buildings and eventually buried them. Accordingly, one of the objectives of the Casey Station design team was to permanently control the problem of drifting snow, and therefore, not repeat the experience at nearby Wilkes. 2 The design of the new 20 person station by the Australian Antarctic Division staff involved a long row of thirteen inexpensive modular buildings elevated 3 meters above the surface on scaffold piping. As a result of wind tunnel testing during the design, the row of buildings was oriented at right angles to the prevailing wind and connected together by a single walkway covered by semi-circular corrugated galvanized steel siding on the windward face. The visual effect was that of an elevated tunnel, rounded on the windward side and squared off on the leeward side. Winds were channeled below the elevated structure and effectively scoured the snow away, eliminating drifting problems as hoped. Figure 1: Old Casey Station Now referred to as “Old Casey Station”, it was replaced in 1989, after 20 years of effective service and scouring, by the current New Casey Station. Interestingly, New Casey Station is constructed on-grade, in the traditional cold regions manner. Snow drifting at the new station has been controlled by careful placement of the buildings in non-drift high areas and periodic grooming. The unique design of Old Casey was not repeated, but not because it hadn’t performed as planned. It had actually performed so well that it was never necessary for personnel to expose themselves to the elements. This luxury was later perceived as a possible cause of lower productivity. Filchner Station (77° 03’ S, 50° 03’ W) As Old Casey was approaching the last several years of its occupancy, Germany was implementing a new approach to overcoming snow drifting and deposition on the opposite side of the continent. In 1982, they completed construction of a small above surface summer station for up to twelve personnel on the Filchner-Ronne Ice Shelf in the southern portion of the Weddell Sea. The ice shelf site of the Filchner 3 Station was characterized by an annual snow accumulation of approximately half a meter, strong winter winds, and seaward drift of the ice shelf on the order of 1000 meters per year. The German designers’ solution to overcoming the annual snow deposition was to place their modular accommodations atop a jackable structural platform on steel columns. The platform was initially elevated 3 to 4 meters above the snow surface. Every 2 to 3 years, the platform was lowered to the surface using a system of winches and cables, the columns were extended by approximately 1 meter, and then the platform was rehoisted to its new height. The entire process took 3 to 4 days, and continued to work effectively until February of 1999 when a several thousand square meter portion of the ice shelf calved and took Filchner with it (unmanned at the time). The station has since been removed from the iceberg and is in storage. Figure 2: Filchner Station Halley V (75° 35’ S, 26° 22’ W) The success of the Filchner Station’s jackable platform concept did not go unnoticed. In 1982, the same year that Filchner became operational, the British Antarctic Survey (BAS) had constructed and opened the third replacement of Halley Station (Halley IV) about 1000 kilometers from Filchner, on the Brunt Ice Shelf off of Coats Land. The site conditions on the Brunt Ice Shelf were severe. Annual snow deposition was on the order of 1.5 meters, gale force winds were common 180 days out of the year, and the annual seaward movement of the ice shelf was approximately 850 meters. From the station’s inception in 1957 with Halley I, structures were designed to withstand being buried and station life was essentially subterranean. The life expectancy of each new replacement station was only 8 to 10 years. Weary of living below the surface and hopeful of reducing the ever-increasing costs of rebuilding an entirely new station every decade, the BAS determined to change 4 tactics and design Halley V as an elevated station based upon the jackable platform concept at Filchner. Retaining Christiani and Nielson of Hamburg for the design, Halley V was completed and became operational in 1992. The 1,255 square meter station for 30 personnel was the most ambitious elevated facility in Antarctica at the time. It consists of three separate buildings on jackable platforms, set 300 meters apart from one another at the three points of an equilateral triangle site plan. Each platform is set initially 4 to 5 meters above the surface. The working facilities on the platforms are created from an interconnected series of prefabricated building modules. The largest facility (The Accommodation Building) is approximately 930 square meters and contains the living, working, and technical support spaces. The smaller two buildings are roughly 140 and 185 square meters, and contain laboratories. As a result of wind tunnel testing at the Cold Regions Research Engineering Laboratory (CRREL), the long axis of each building is oriented parallel to the prevailing winds in an effort to minimize any platform level drifting which would impact exterior pedestrian activity and access. Unfortunately, this orientation has had the adverse effect of aggravating drifting below the platform at the leeward end of each complex. Figure 3: Halley V Halley V contends with a much greater annual snow deposition and drifting problem than either Filchner or Old Casey. As a result, jacking must be performed annually. Similar to Filchner, the platforms are lowered to the surface, the columns are extended (in this case by 2 meters), and the platforms are then raised to their restored heights and the cycle begins again.