In the fifth and sixth centuries AD, Constantinople was the center of the world. Built at the mouth of the Bosporus Strait, it connected the Black Sea to the Mediterranean and linked Europe and Asia. The commerce, politics, and culture of much of the planet swirled around the basilicas and markets. Named for the first Christian Roman emperor, the city was the capital of Byzantium and the prize of marauding armies, from Crusaders to Huns.
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The region is still a crossroads. But now it's Istanbul, not Constantinople — a megalopolis of 10 million people that straddles East and West. And everyone has a car. Two traffic-clogged bridges cross the Bosporus, and auto exhaust chokes the streets and eats away historic architecture. The city has aboveground rail lines and a vestigial subway system, but hardly anyone rides them. So a decade ago, the Turkish government announced that it would fulfill the ancient dreams of sultans, with an ambitious plan to dig a tunnel under the strait.
In fact, the Turks are trying to remake how people get around — and through — the city. The $3 billion Marmaray Project (named for the body of water just outside the strait and the Turkish word for rail) will consist of 48 miles of new railroad, 37 rebuilt train stations aboveground and three new ones below, and eight miles of tunnel connecting Istanbul's western, European side to the Asian east. Most of that underground rail line will be chewed through bedrock by digging machines wider than a 747. But one mile will be different, immersed beneath the shifting bed of the Bosporus. It'll be the deepest such tunnel in the world, under 180 feet of water and 15 feet of earth, made of 11 steel-and-concrete sections that can be as long as 440 feet and weigh 18,000 tons.
When it's finished in 2012 — currently two years behind schedule — the project will change how the continents connect. Rail travelers (and rail cargo) currently have to transfer to a ferry for a three-hour journey across the city; that'll drop to less than two hours. Ideally, the tunnel will also relieve some of the pressure on those bridges. And when the Marmaray Project is integrated into a planned railway through Azerbaijan, Georgia, and Turkey, you'll be able to hop on a train in London, wave at the Hagia Sofia, and step off days later in Beijing.
The project is ambitious enough to worry even the most experienced engineers, but its location could give a seismologist night sweats. All this work is taking place just 12 miles from the North Anatolian Fault, Eurasia's version of the San Andreas. Since AD 342, it has seen more than a dozen huge quakes that each claimed more than 10,000 lives. Two in 1999 together killed 18,000 people. Worse, over the last century the tremors have marched steadily west, toward Istanbul and the strait.
There's another problem: The hub of this tunnel system sits on one of the greatest historic treasures of the classical world. In 2005, the dig ran into the remains of a fourth-century Constantinople port, Portus Theodosiacus. It's smack on top of what'll be an underground station on the new train line. Researchers are rushing to preserve the find, including what seems to be the only Byzantine naval vessel ever discovered, and that's preventing the contractors from starting in earnest.
Delays to the tunnel's progress are expensive — $1 million a day in lost revenue. Yet Turkey can't afford to run roughshod over the delicate archaeological discovery. The country has been trying to get into the European Union for decades, and destroying priceless ancient artifacts doesn't exactly endear you to the Western world. Steen Lykke, project manager for Avrasyaconsult, the international consortium that's overseeing construction, sums it up: "I can't think of any challenge this project lacks."
"You see this?" Claus Iversen, Avrasya consult's supervisor of marine works, waves a yard-long piece of rebar curved at one end like a shepherd's crook. His voice echoes inside a half-built tunnel section as he picks his way over the steel lattice that makes up the floor and part of the walls. "We have two guys in a building over there making a million of these. One bends, the other welds."
Here at the Tuzla Shipyard just outside the city, construction workers will insert huge ballast tanks into each completed segment and cap their ends with steel doors — waterproof bulkheads. Then the segments will be put on barges and floated out to the Sea of Marmara.
Once they're in position, the barge crews wait for the current to slow to less than 5 feet per second — any faster and they won't be able to safely drop the tunnel segment. When they're ready, the crews will angle the segment into the current (making it slightly more streamlined) and flood the tanks. The segment will sink, bound to the barge by steel cables that the crew controls like puppeteers. "My friends joke that I'm building concrete submarines," Iversen says.
On the bottom, divers will release the cables after the segment is in place and connect it by hand to the ones already sunk. Inside the tunnel, workers will pump the water out of the ballast tanks and dismantle them, along with the steel bulkheads. There are only two segments in place so far, and they are connected to the surface by a 6-foot- diameter access hatch. All the pieces of the doors and the tanks will get carried out that way, making room for two parallel train tracks.
Meanwhile, digging the parts of the tunnel under the city isn't going smoothly. Much of the substrate is either soft or rotten. "We don't talk about the rock as solid," Lykke says. "It's more like bricks piled at an angle with grease in between them." Avrasya consult is using just about every tunnel- digging technique humans have invented to make the project work — even the controversial New Austrian Tunneling Method. Designed for unstable soil, it involves using spray-on concrete called shotcrete to solidify the ground around the tunnel. Tunnels dug this way have an unnerving tendency to collapse during construction, as one did in Munich in 1994, killing four and injuring 27. There haven't been any problems yet in Istanbul.
Even more ominous than the frequency of earthquakes along the 745-mile-long North Anatolian Fault is the pattern. At their most basic, quakes happen when two moving sides of a fault squeeze together. As stress builds, the fault ruptures and the ground shakes. Most of the time that relieves the stress and the fault quiets down, like champagne going flat after a dramatic cork-popping. Sometimes, though, a temblor relieves stress on one part of the fault but increases it farther down the line. Geologists call this process stress transfer, and it can lead to a string of tremors repeating like seismic dominoes. That might be why quakes along the New Anatolian have been getting closer and closer to Istanbul over the last 100 years. Since the 1939 Erzincan earthquake in eastern Turkey (magnitude 7.9), Big Ones have been migrating west. Geologists calculate that the chances of the city getting hit by a quake topping 7.0 in the next 30 years are as high as 77 percent.
The tunnel's engineers are preparing for the worst. Squishy, waterlogged soil like the stuff they're digging through can liquefy during a quake, basically turning to quicksand. So builders are infusing the sand layers with a thin mortar of industrial grout down to 80 feet below the seabed. The walls of the tunnel will have both a steel shell, often used in the US, and a waterproof concrete layer, which is popular in Europe. Each is independently watertight. The whole thing will be long and narrow enough to flex "like a straw in gel" during a tremor, Lykke says.
The underwater tube will connect at both ends to tunnels being bored from each side of the city; they are supposed to be done next year. At the joint between rock and water will be a giant rubber and steel gasket that'll let the structure shift without breaking during a quake. And if everything goes to hell and the tunnel gets breached, floodgates at these joints will slam down to isolate the tube and keep the train stations on either side from filling with water. The Marmaray builders say their design will withstand a 7.5 quake, bigger than the one that all but leveled Kobe, Japan, in 1995.
"Tunnels are like buildings with very thick walls," says Geoffrey King, director of the tectonics lab at the Centre Nationale de la Recherche Scientifique's Institut de Physique du Globe de Paris. "That's the ideal way to earthquake-proof a building." Of course, he adds, no system is perfect. "I wouldn't like to be in such a tunnel during an earthquake."
The hub of the Marmaray Project is mostly underground, the size of three football fields. Yenikapi Station will be the second stop on the European side, just over a mile from Istanbul's historic Blue Mosque in the old center of the city. The tunnel-boring machines start at Yenikapi, pass by Sirkeci Station — the deepest one, where builders are using the New Austrian method — and then hit the water.
Before construction started, archaeologists surveyed the site to see what was there. This is Istanbul, after all — a 2,700-year-old city where you can't bury a cat without unearthing something older than the US. The builders expected a few artifacts, maybe an old foundation or two. But in 2005, they found a shipwreck. Then they found a massive limestone block. And stumbled upon another. And another — a line of 20 blocks extending 80 feet. It was the remains of mighty Portus Theodosiacus, lost for 1,000 years and, experts agree, the greatest nautical archaeological find in modern history.
Today, station contractors work on the foundations in carefully prescribed areas, alongside hundreds of hard-hat-wearing archaeological workers swinging picks and pushing wheelbarrows amid thousands of years of history. "It's a virtual museum of ancient shipbuilding technology," says Cemal Pulak of Texas A&M and the Institute of Nautical Archaeology. He's an expert in early wooden-shipbuilding techniques and a researcher on the dig. On a walk through its maze of trenches, platforms, flooded pits, and dirt paths, he stops briefly to point at an orange sliver poking out of the dirt. "Hmm," he says, "human bone."
The scope of artifacts is overwhelming. Some date back to the 6th millennium BC, the oldest settlements ever uncovered in Istanbul. Pottery fragments, shells, and pieces of bone litter the ground. Blue milk crates full of everything from amphorae to horse skulls are stacked head-high near trailers that serve as temporary offices. And somewhere in a storage facility are nine human heads, found in a bag.
But the most important discoveries have been ships — fishing boats, transport vessels, cargo carriers, and what seems to be a Byzantine warship, the first ever found, all from the 7th to 10th centuries. Most of the wrecks are incredibly well- preserved, thanks to oxygen-squelching sand and silt that filled the harbor. But extracting and preserving them is an arduous process involving years of injections of polyethylene glycol, a stabilizing polymer. "All the lignins and tannins have been leached out," Pulak says, standing in front of an ancient wooden hull. "If you just dried it out, it would turn to dust."
The engineers are getting impatient with all this history. The dig forced Yenikapi Station to be redesigned, which meant pushing back other elements of construction. "Honestly, is this an archaeology project or are we tunneling?" Iversen says. "We have meetings sometimes where we end up talking about the archaeological dig for half the time." When he tells locals about the new completion date for the project, they often respond with a cynical "Yeah, yeah." Contractors wonder why they should heed the construction schedule when the excavations have already caused years of delays. "Lots of equipment is just sitting around," he says.
Archaeological field manager Metin Gökçay says there is no time limit on their work, although my interpreter's eyebrow rises as he translates this. "The work comes first," G k ay says. "I know how to deal with people." He's about to retire, he says, so he doesn't have to worry about getting fired.
The project is byzantine — there's no other word for it. And all that complexity means tensions are high. Access to the site, once open to reporters, has become more and more restricted. It took me months to get permission to talk to the scientists; the government appears terrified of being publicly embarrassed.
Under the pressure, the archaeologists are barely keeping it together. Pulak says his group is "almost on nonspeaking terms" with another team from Istanbul University's conservation department, which he thinks is too inexperienced at digging up ships. The squabbles have gotten too much for him. He says this summer is likely his last season at the dig. He's heading home to teach, fleeing a project marked by "lots of politics and lots of egos."
Turkey must finish the tunnel, but it can't just bulldoze the ancient port. The country's bid to enter the European Union — pending for 40 years, since even before it was called the EU — has been held up in large measure by questions about human rights and democracy. Showing sensitivity to other cultures by honoring the heritage the past represents is good PR on that front. But to prove it is a Western-style state, Turkey also has to display a certain facility with high tech and big engineering, which means completing the project. Indeed, one of the main arguments against admitting Turkey to the EU has always been that the country isn't exactly in Europe. Geographically speaking, though, if you build the tunnel, the country is suddenly at least as tightly connected to the mainland as the UK is.
Historically sensitive modernization is not impossible. Greece managed to build a metro through the heart of Athens, remodeling that classic metropolis without destroying its foundations. But in Turkey, the outcome of this tug-of-war between past and present is still uncertain.
None of that tension is visible on the surface waters of the Bosporus. Instead, there's just the day-to-day action of one of the world's busiest shipping lanes. Boats and ships of every sort — ferries, cargo ships, tankers, fishing boats, luxury yachts — pass back and forth. Cruise ships the size of skyscrapers rest in port. And 800 feet off the Asian side, there's a small yellow platform, metal, surrounded by a heavy railing lined with flashing yellow lights and fitted with a warning bell the size of a basketball. In the center is the access shaft to the tunnel. It's the only way in or out, and it's so far from the shore that it feels like a shipping accident waiting to happen. "We're used to the North Sea," Iversen says. "Always, safety first."
Until the tunnel borers meet the water, the platform is the only link between the tunnel and the surface world. And right now that connection feels awfully vulnerable.
Julian Smith (email@example.com) is a writer in Portland, Oregon.