The Herrenknecht S-391 TBM reached its target shaft in Istanbul. At its deepest part the tunnel route runs 135 m below the sea straits water level. The Russian construction company OAO Mosmetrostroy and the tunnelling machine excavated this challenging section safely. The first mechanically- excavated tunnel beneath the Bosporus was built in only 13.5 months.

The ‘Melen 7’ tunnel is the key element of a large scale project to secure an improved long term water supply for the huge city of Istanbul, which today is home to more than 10 million inhabitants. This water is not only required on the European side of Istanbul as a drinking water supply, but is also urgently needed for agriculture and regional industries.

For this purpose, the river Melen has been dammed on the Asian side, 170 km outside the gates of the city. From this high-rainfall area, the water will be channelled to Istanbul in several stages.