All You Need To Know About India's First Underwater Metro Tunnel

Underground tunnelling is a noticeable construction feature across the world. Thames Tunnel in London, is the oldest existing underwater tunnel which was opened in 1843. Many emerging economies have begun to realise the huge potential underground spaces possess, for providing connectivity between cities. Creation of an underwater passageway is an innovative and intelligent solution for the sustainable development of infrastructure.  

Kolkata will be the first city in India, to have an underwater tunnel. While the construction work for the country's first underwater metro tunnel, to be built near river Hooghly in West Bengal's Howrah, is already completed, it is expected to be operational by June 2019. Here's an update on the story.

Facts about the country's first underwater metro tunnel

Two parallel tunnels has been constructed along the route of the upcoming Rs 9000-crores East-West Metro project that will link Salt Lake Sector V in the east, to Howrah Station in the west. To be built 13 metres below the riverbed and 30 metres below the earth's surface, the 520-metre tunnel structures, will run on either side of the Hooghly river and will connect the twin cities of Kolkata and Howrah.

Howrah is a bustling area and a large number of commuters travel from the station located here. Completion of the metro project, including the launch of the two tunnels, will give a major boost to the regional connectivity and will consequently, enhance the real estate growth prospects.

Construction facts about the tunnel project

• Six out of the twelve stations on the metro route will be built on a 10.8-kilometre long underground corridor. The diameter of the tunnel is 5.5 metres and the distance between the parallel tunnels, will vary along the stretch.

• Around 250 people have been deployed at the site and construction is in progress, using the German-made Tunnel Boring Machine. To tackle the challenges of collapsing of earth, soil erosion or water seepage, the tunnel segments will be sealed, with a thick layer of concrete.

• The Kolkata Metro Railway Corporation Limited, is taking efforts to address issues of structural damage caused to some popular heritage buildings like the Howrah District Library located near the site because of the digging activities. Measures to widen the foundation of the structure and grouting of the soil, have been undertaken. Authorities are devising plans to prevent damage to other buildings in the vicinity that include the Currency Building, an Italian structure built in 1830s and two Jewish Monuments - the Maghen David Synagogue and the Beth-El Synagogue.

• The idea of an under-river tunnel was conceptualised way back in 1984 under the rule of Prime Minister Indira Gandhi, during the construction of the metro project but could not be undertaken due to lack of funds.

• The Japan Bank of International Cooperation (JBIC) and Indian Railways have funded the second phase of the metro railway expansion project, with a total cost of Rs 50 billion.