TÜV SÜD has been involved in the project as a consultant since 2012, which is when Valentina Monaco began her work here. Monaco, who has a degree in railway engineering, has regularly been flying from her office in Graz, Austria, to Istanbul to inspect designs, speak with project technicians and to critically evaluate installed facilities. As the only woman among dozens of men, she’s often had to assert herself—something she’s been very successful at—and vetoed things when engineering offices were too adventurous in their planning. She also learned to speak Turkish during this time, along with the five other languages she’s fluent in. And she has earned a great deal of respect due to her professional expertise and experience—on large railway projects in Italy and Mexico among others.
Right now, however, Monaco has turned her back on a good dozen subway technicians and is trekking by foot into one of the tunnel tubes. “My most important work tool is my feet,” she jokes. “And my eyes, naturally.” She’s using them to scan the track bed for potentially loose areas. She stops at a rail mounting. Monaco bends down, pulls at a bolt with her hands, pulls out a small spade and scrapes away some rust. Finally she draws a cross in white chalk next to the bolt and types a note on her smartphone. Later she’ll send a Marmaray Metro employee to this spot to tighten the bolt. About 1,100 meters further along there is a sliding steel door that connects the two tubes of the tunnel across the Bosphorus. The door must always remained closed to prevent smoke, poisonous gases or fire from getting into the other tube in the case of an accident or fire. Yet at the same time the door should be very easy to open so that passengers can get to safety if needed. Monaco grabs the handle with both hands, first pulls and then pushes the door open. She walks through it, releases the door and watches it close automatically. “Works,” she murmurs.
As Monaco continues walking along the edge of the track bed, she passes a spot where the gray of the tunnel wall is a different color than the rest: “This is where the individual elements were connected to one another,” she explains. This is related to the special construction method used for the Marmaray Tunnel. The connecting tunnels on the European and Asian mainland were built by means of normal excavation, advancing with gigantic drilling machines. The tunnel’s central element, the passage stretching beneath the sea, was built using immersed tube construction. Eleven tunnel elements up to 135 meters long were prefabricated on land and towed out on transport ships. As freighters sailed by to the left and right—around fifty thousand pass through the strait annually—construction workers slowly flooded the elements and precisely placed them in a trench dug into the floor of the Bosphorus. After connecting the individual pieces, workers pumped the water out of the entire tunnel and then covered the outside of it with dirt.
An earthquake struck the region east of Istanbul in 1999. Measuring 7.4 on the Richter scale, it caused buildings and bridges to collapse, killing nearly twenty thousand people. Experts suspect that the next big quake could directly impact Istanbul itself. Just a few miles outside the metropolis is the North Anatolian Fault, where the Anatolian Plate is sliding in fits and starts past the Eurasian Plate, regularly rocking the region with tremors. For this reason, the Marmaray Tunnel has been engineered to withstand a quake up to a magnitude of 7.5.
And what if water began flooding the tunnel? “In that case, it can be evacuated within minutes and hermetically sealed,” Monaco says. She’s standing in front of one of the four floodgates, smartphone in hand. On her command, a warning signal sounds, and then a yellow steel wall slowly slides down from above through this cross-section of the tunnel. Signaling equipment retracts out of the way of the floodgate. Monaco times how long it takes before the gate comes to a grating halt, locking into place on the track bed. “The system effectively prevents the ingress of water from reaching the subway stations,” she says.
Early in the morning, just before six o’clock and many miles later, Monaco steps outside of the Üsküdar subway station into the city. Istanbul’s Metro will be resuming operations in just a few minutes. Dawn is beginning to break, and the sun will rise in a good half hour. Monaco briefly watches a freighter, but then her gaze comes to rest on the lighted suspension bridge, which has spanned the Bosphorus since 1972. She takes a deep breath of the fresh morning air—and for quite some time continues watching the water’s smooth surface, beneath which she spent the night wandering back and forth.