Feature BUILDING TOMORROW'S INFRASTRUCTURE Finally Connected Turkey’s Marmaray Subway Tunnel Fulfills a 150-Year-old Dream for Istanbul 1 NOAM KATZ from the Japanese government, Tokyo-headquartered Taisei Corporation entered a joint venture with ITUATED at the crossroads between Europe Turkish companies that began work on the tunnel in and Asia, Istanbul is divided by the waters of August 2004. Sthe Bosphorus Strait. Yet on October 29, 2013, The Marmaray tunnel claims two world firsts: a railway tunnel underneath the strait finally linked the deepest undersea immersed tube tunnel (an the two sides, a century and a half after railway underwater tunnel composed of concrete segments engineers first envisioned steam trains crossing and steel plates, constructed elsewhere and then the gap. Before the Marmaray tunnel, people either sunk into place on the seabed), and the first successful spent up to two hours crossing by car on congested docking between a rectangular immersed tunnel and suspension bridges or took a thirty-minute ferry conventional round tunnels being extended from ride. By contrast, trains on the new underwater rail land. For the undersea tunnel, since depth restrictions conduit make the crossing in just four minutes. for the train stations at both ends precluded the The Turkish government embarked on the use of tunnel-boring machines, a ship battled the ambitious Marmaray Project in the late eighties to tricky currents of the Bosphorus to lower sections of alleviate traffic congestion and reduce air pollution prefabricated tunnel into trenches in the ocean floor caused by car emissions. The goals were to upgrade sixty meters below the surface. After the sections twenty kilometers of tracks on Istanbul’s European were submerged, engineers carefully joined the side and forty kilometers on the Asian side, introduce 1.4-kilometer undersea tunnel to the tunnels above new rolling stock and control systems, and construct the ground, maintaining maximum differences of just a tunnel under the strait. With financial assistance ten centimeters. 10 | highlighting japan 1 The bright and shining environs at Yenkapi Station 2 A look at the construction site on the surface 3 The Marmaray tunnel is the world’s deepest immersed tube tunnel 4 The tunnel completion ceremony 2 3 4 Takashi Imaishi, the acting general manager in the five years. Nevertheless, “we learned new things about Civil Engineering Department of Taisei Corporation’s Istanbul’s history,” says Imaishi, citing the remains of a international operations headquarters, was directly cargo ship from the Roman period found intact, which involved in the project. The demanding technical provided historians with valuable clues to historical requirements notwithstanding, what Imaishi trade routes. Some of these artifacts are now showcased remembers the most are the challenges that cultural in Yenikapı Station’s open museum. norms presented. According to Imaishi, Japanese construction “This was the first time we’d done business in companies like Taisei are well-suited for these kinds Turkey, and the regulations and business sense were of projects because they possess in-house research completely different from Japan,” he says, explaining laboratories and designers, in contrast to foreign how the local approach to work in accordance with construction companies that typically contract out for Turkish religious customs meant that “we couldn’t research and design. He says this allowed for a more proceed on a Japanese schedule.” flexible response to unexpected requests during the The project’s location posed significant headaches as Marmaray Project. Expertise in earthquake-resistant well. Istanbul’s lengthy history has led to excavations construction was also an asset, since the undersea that unearthed historical sites from the Ottoman, tunnel had to be built to last a hundred years. Byzantine, Roman and Grecian periods, along with Imaishi says ridership on the new subway is high and even older artifacts dating back up to 8,500 years. passengers appreciate the savings in both time and cost, Archeological surveys performed each time ruins were although operation is still limited. The tunnel already discovered brought construction to a standstill, and represents not only better access in Istanbul, but also a ultimately delayed the project’s completion by nearly testament to the power of Japanese technology. DECEMBER 2014 | 11.