How Kolkata is creating history with India’s first underwater metro- Explained

Kolkata is set to welcome India's first underwater metro train which will allow commuters to travel across the Hooghly river which separates West Bengal's capital from Howrah. The metro authorities undertook a trail run on 12 April from Howrah Maidan to Esplanade, with only officials and engineers on board. The underwater metro line is expected to be open for commuters by the end of 2023.

“Trial runs between Howrah Maidan and Esplanade station will be conducted for the next five to seven months, following which regular services on this stretch will begin,” Metro Railway general manager P Uday Kumar Reddy said.

How Kolkata is planning to operate an underwater metro line?

The authorities have constructed a tunnel under the river Hooghly with an internal diameter of 5.55 meters and external diameters of 6.1 meters. The construction of the tunnel is completed with the help of a tunnel-boring machine (TBM). The German-made TBMs named Prerna and Rachna finished the task in a record 66 days.

According to an official quoted by the news platform TheIndianExpress, the authorities took multiple measures to prevent water inflow and leakages in the tunnel. The concrete mixes composed of fly-ash and micro-silica are used to avoid the permeability of water.

The task was particularly daunting as the areas around the area of underwater tunneling had many historic buildings and the authorities had to make sure that the buildings don't receive any damage as part of the process.

Kolkata underwater metro: Part of East-West Metro Corridor

The East-West Metro Corridor in Kolkata includes a tunnel that spans 520 meters and connects the IT hub of Salt Lake Sector V in the east to Howrah Maidan in the west, crossing the river. By taking this metro route, the travel time between Howrah and Sealdah can be reduced to 40 minutes compared to 1.5 hours by road, which will also help alleviate traffic congestion at both ends.

The tunnel is located 13 meters below the riverbed and 33 meters below the surface level. According to reports, the tunnel comprises four stations - Esplanade, Mahakaran, Howrah, and Howrah Maidan - and it will take only 45 seconds to traverse it.