The tunnel is 13 metres below the riverbed and 33 metres below ground level. (File)
India's first underwater metro in Kolkata, an example of 'Atmanirbhar Bharat', for which a challenging task was done by Indian engineers, is expected to be open for commuters by the end of 2023.
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)
Tunnels under the bed of river Hooghly, running 32 metres below water level is considered to be an engineering marvel.
"This is India's first underwater railway system which has been introduced in between Hooghly River. It will start from Howrah Maidan station, but you will be able to get this opportunity to travel beneath the river from Howrah Maidan to Mahakaran metro station," Kaushik Mitra, Chief Public Relations Officer of Eastern Railway told ANI.
The tunnel is 13 metres below the riverbed and 33 metres below ground level.
When asked about the date for underwater route commercial use, Mr Mitra revealed they aim for December 2023.
Talking about the project, General Manager Civil, Kolkata metro rail cooperation limited Sanjay Banerjee said the entire project is 16.55 km and it is partly elevated and partly underground.
"The challenges were many but the main challenge was a city like Kolkata which has heavily built-up areas and working with existing buildings requires careful planning," Mr Banerjee said.
On the indegenisation of the project, he said, "We have obtained advice from a foreign consultant but everything else is done by Indian companies. Part of the underground project is functional from Phoolbagan to Sealdah and Esplanade to Howrah Maidan we are planning to open by the end of 2023."
"We have used our indigenous technology, our Indian engineers have worked very hard and it is an example of Atmanirbhar," Aditya Choudhary CPRO of South Western Railways said.
The corridor passes below the river Hooghly between Mahakaran and Howrah Metro Station. This feature makes it the first underwater (Subaqueous tunnel) rail system under a major river in India.
The tunnel across the river has been built in a record 66 days-time which connects the Howrah station complex on the western bank to Armenian Ghat on the eastern bank. The tunnel is located 350 meters downstream of Rabindra Setu (Howrah Bridge).
The twin tunnel system was executed by Earth Pressure Balancing Tunnel Boring Machines which were launched from Howrah Maidan and were retrieved at Esplanade station after completing the work in the single drive of 3.65 KM. The tunnel passes through pre-dominantly stiff clayey silt.
The length of the tunnels below the river is 520 meters with a depth of 16 meters below the river bed at the deepest location.
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