India's first under water tunnel will connect Kolkata and Howrah

Work on the  first underwater metro tunnel in the country commenced in April when a gigantic Tunnel Boring Machine (TBM) began cutting deep inside the bed of the Hooghly river. It is expected to be ready by the end of July. Two tunnels running parallel will connect the twin cities of Howrah and Kolkata located on either side of the Hooghly. The tunnels are being dug at a depth of 30 metres below the earth’s surface and 13 metres below the riverbed. The 520 metres long twin tunnels are part of  the much-awaited ₹ 8,900 core East West Metro project that will connect Salt Lake Sector V in the eastern part of Kolkata to the Howrah Maidan across the river. The  East West Metro route will be made up of 16.6 km, of which 5.8 km is on an elevated corridor and 10.8 km will run underground. The 520-metre tunnels under the river are part of the 10.8 km underground stretch. About 250 people are working day and night on the tunnels. Alongside, a dense concrete layer is being used to seal the tunnel, prevent the subsidence of earth, and stop seepage of water which is a primary concern for the engineers working on any water tunnel.