The Turkish Transport Ministry announced that the tender for the world's first three-level underwater tunnel, to be constructed under the Bosphorus Strait in Istanbul, would be held on December 23.
Earlier this year, the Turkish government announced the new mega project, which is expected to ease the city's extreme traffic congestion.
The sub-sea tunnel will have three levels -- a two-deck motorway and a metro line.
Previously, the Ministry of Transportation, Maritime, and Communication had announced the tender for the “three level big Istanbul Tunnel Project" would be held on December 14.
In a new statement, the ministry said the tender for study, design and engineering services would be held 10 days later.
The 31-kilometer-long tunnel project had already been approved by the ministry of Environment and Urbanization.
According to the file presented, the 31-kilometer-long metro system between İncirli (European side) and Söğütlüçeşme (Asian side) will be divided into three segments. The highway integrated into the metro line will be 16,150 kilometers long and divided into five segments, between the TEM Highway Hasdal Junction and Ümraniye Çamlık Junctions.
With the implementation of the project, railway systems on the European Side of Istanbul will be 15,000 meters long, the three-level tunnel will be 6,500 meters long, and the section on the Asian side will be 9,500 meters long, equaling 31 kilometers of railway systems in total.
The diameter of the three-level tunnel will be 16.8 meters and the tunnel will be built 110 meters under the sea and the water depth in the area that the tunnel will cross under the Bosphorus will be 60-65 meters.
The three-level segment, which includes both the metro and the highway, will be 6.5 kilometers long, and 14 stations will be located on the metro line between İncirli-Söğütlüçeşme.
The tunnel project, which is estimated to cost USD 3.5 billion, will enable 40-minute travel from İncirli to Söğütlüçeşme and a 14-minute journey by car from Hasdal crossroads to the Ümraniye Çamlık crossroad via high speed metro line.
At the end of the of the project, the world first 3-level tunnel will integrate nine different urban train systems with a fast metro track, which is used approximately by 6.5 million passengers on a daily basis.
After London, Istanbul has the oldest underground urban line in the world; the funicular line, Tünel, still operating today first took passengers in 1875. Construction on the modern metro network began in 1989, with the Marmaray Tunnel (the Bosphorus undersea railway tunnel) connecting the Asian and European metro lines opening in October 2013. The Metro operates from 6 am to approximately 0:30 am every 7–10 minutes; during peak-hours the intervals reduce to 5 minutes.
Meanwhile, the construction of the Eurasia Tunnel, another undersea tunnel that will also link Istanbul's European and Asian sides, is underway and expected to launch for operation in 2016.
In mid-August, Istanbul Mayor Kadır Topbaş announced two new metro lines, in another step toward a long-lasting solution to Istanbul's extraordinary traffic.
