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The excavation of a tunnel joining Europe and Africa, deep below the Strait of Gibraltar, could start as early as next year. This follows the recent commissioning by Spain and Morocco of detailed engineering studies. BY PETER KERVILLE  Veteran Swiss tunnel engineer Giovanni Lombardi has been called in by the governments of Spain and Morocco to draw up a project outlining how work could proceed towards creating the only direct physical link between the two continents – a tunnel under the Strait of Gibraltar.
Lombardi, at eighty years of age, is unlikely to see the completion of his dream. He has built many tunnels in Switzerland and was recently called in to redesign the Mont Blanc tunnel after 41 people died in a fire there in 1999. Exploratory tunnelling could start after Lombardi’s report is handed in next year. It will be based on recent detailed studies of the geological patterns under the strait. “We are just beginning the work, but I would say this is more difficult than the Channel Tunnel,” he predicts. “The main difference is the depth of the sea, but the geological conditions are also different.” Giovanni Lombardi says that actual construction of the 40 kilometre twin rail tunnel could take fifteen years from when preliminary studies and the exploration tunnels were finished. Spanish engineers involved in the project have said that if no major geological or technical problems arise rail passengers could be travelling to and from Africa by 2025. The link is projected to consist of twin rail tunnels with a service tunnel between, and the viability is based on forecasts of carrying nine million passengers in the first year of operation, rising to eleven million after 10 years. It could also carry eight million tonnes of goods in 2025, and this aspect of the project seems highly positive, since Morocco is a very substantial supplier of fresh produce to Western Europe. The so-called ‘Garden of Africa’ has huge irrigation areas that run down the western side of the Atlas Mountains, fed by rivers collecting rain from moisture-laden winds blowing in from the Atlantic. A final decision on whether the tunnel will be excavated, however, depends on both financing and political will. The border between Morocco and oil-rich Algeria is currently closed, for example, thereby reducing potential traffic. There are no firm costings for the tunnel as yet, but estimates made several years ago put the minimum price at more than five billion Euros (NZ$9.23 billion). The 49.1 kilometre Channel Tunnel, although relatively easier to build, eventually cost almost fifteen billion Euros, and has been a financial basket case almost since it commenced operations. If the tunnel to Africa was linked to the existing high-speed rail line at the southern Spanish city of Seville, the travel time between Madrid and Tangier could be as short as four hours. Spain first began studying the idea of a transcontinental tunnel in the 1970s. A joint Spanish-Moroccan body was founded in 1991, inspired by the building of the Channel Tunnel, to start surveying the seabed under the strait. Those studies have been hampered, however, by sea conditions in the strait. Engineers have had to invent new boring methods in order to cope with the fierce underwater currents at a point where the Atlantic Ocean meets the Mediterranean Sea. They have already decided that the tunnel cannot cross the narrowest part of the strait because, at 900 metres, it is too deep. A rail tunnel at that point, between Spain’s Punta Canales and Morocco’s Cirea Point, would have to start too many kilometres inland so that the gradient would not be too difficult for trains to climb. The current proposed route for the new tunnel lies to the west, where the seabed is, at 300 metres, relatively shallow. Even that is much deeper, however, than the Channel Tunnel where the seabed lies just 50 metres below the waves. As a result, the gently sloping tunnels will emerge at least 4.8 kilometres inland from the coast on either side. The mooted tunnels would be 38.7 kilometres long with 28 kilometres running some 400 metres under sea level. They would not carry road traffic owing to a perceived risk of accidents and also because of ventilation difficulties, according to Lombardi. The strong currents and depth mean that bridges have been ruled out as a way of connecting the two continents. Some engineers, however, favour the idea of building a huge barrage that would also control water flow into and out of the Mediterranean. The geological layers under the Strait of Gibraltar are horizontal, meaning that the tunnel has to cross through many different rock strata. “That is quite a complex geological situation,” says Lombardi. Underwater clay deposits that have recently been discovered near the Moroccan coast have further complicated the project. Lombardi said he would also have to take into account a history of earthquakes in the region, including the 1960 quake in the Moroccan city of Agadir and the 1755 quake centred near Lisbon. That earthquake caused huge damage in the area and killed 50,000 people in the Portuguese capital, not too far distant from the tunnel site. It all may sound very ambitious, but comparable plans are on the drawing boards. The longest tunnel currently planned would connect Lyon in France and Turin in Italy, completely eliminating the barrier of the Alps with its extensive foothills. Apparently this is a serious proposal that won’t be completed until between 2015 and 2020. Contractor Vol.31 No.5 June 2007 |