PM unveils India's first underwater metro in Kolkata: All you need to know

West Bengal’s Kolkata welcomed India’s first underwater metro train today.

Prime Minister Narendra Modi inaugurated the Howrah Maidan-Esplanade section, which is constructed beneath the mighty Hooghly River.

After the inauguration programme, the Indian leader also took a metro ride from Esplanade to Howrah Maidan along with school children.

Here’s all we know about the historic project.

India’s first underwater metro tunnel in Kolkata

The East-West Metro corridor’s 4,965-crore Howrah Maidan-Esplanade section is home to India’s first transit tunnel beneath a major river, reported CNBC-TV18.

The 4.8-kilometre underwater metro stretch is part of the 16.6-kilometre-long East-West Metro corridor between IT hub Salt Lake Sector V and Howrah Maidan.

The section includes the Howrah Metro Station, which is the country’s deepest metro station. The portion crosses the Hooghly River, which has the cities of Kolkata and Howrah located on its east and west banks, respectively.

According to The Indian Express, implemented by Kolkata Metro Rail Corporation Limited (KMRCL), the three metro sections were approved by the Ministry of Railways at an estimated cost of Rs 8,575 crore.

By addressing Kolkata’s air pollution and traffic congestion, the project hopes to create a more efficient and sustainable metropolis, as per Hindustan Times.

The underground corridor, which runs beneath the Hooghly River between Howrah Maidan and Phoolbagan, makes up 10.8 kilometres of the 16.6 kilometres East-West Metro. The remaining distance is comprised of an elevated corridor.

Howrah Maidan, Howrah Station Complex, and BBD Bagh (Mahakaran) are the three stations that will be part of the underwater metro segment, as per Indian Express. Notably, the entire route has 12 stations.

According to Times Now, the tickets for the underwater metro is likely to start at Rs 5 for the first two kilometres and can go up to Rs 50, depending on the distance.

The trains will have an operational speed of 80 kilometres per hour and will cover the half-kilometre stretch under the Hooghly in about 45 seconds.

“We are expecting a daily ridership of seven lakh,” Kolkata Metro Railway general manager Uday Kumar Reddy said to ANI.

In April 2023, Kolkata Metro made history by operating a rake via a tunnel beneath the Hooghly River for the first time in the nation, as per CNBC-TV18.

The Taratala-Majerhat metro link and the Kavi Subhash-Hemanta Mukhopadhyay metro link are the other two sections of the metro project. The government claims that the three parts will aid in traffic reduction on the roads and offer seamless, simple, and comfortable connectivity.

Other technical facts

The diameter of the tunnels beneath the Hooghly is 6.1 metres on the outside and 5.55 metres on the inside, reported Indian Express.

For the segments, fly ash and micro silica-based concrete mixtures have been utilised to reduce water permeability.

The newspaper quoted a technical expert involved in the project as claiming that the interior walls are made of premium M50-grade reinforced concrete segments, each measuring 275 millimetres in thickness. These segments were cemented together using an intricate grouting technique.

Between April and June 2017, two German tunnel boring machines (TBMs) broke through the layer in a record-breaking 66 days. In 2017, the first machine crossed the river in May, and the second in June.

The idea for the underwater tunnel

Researchers say that the British originally proposed the idea of an underwater transit system along the lines of London in 1921, as per CNBC-TV18.

An ambitious 10.6-kilometre underground railway linking Kolkata and Howrah was the brainchild of British engineer Harley Dalrymple-Hay, who was born in Bengal, more than a century ago, according to the BBC.

10 stops and a tunnel beneath the Hooghly River were part of the design.

Nevertheless, the project was never completed because of financial difficulties and worries over the quality of the city’s soil, the report continued.

“The idea did not see the light of day as soil tests did not yield positive results. They were forced to abandon the idea and the project plan was shelved,” Aloke Kumar, Associate Professor of IIM-Calcutta, told PTI.

Harley was contacted later, in 1928, by CESC, the city’s energy supply company, to construct a power cable tunnel beneath the Hooghly.

According to the news report, he accepted the challenge, and in 1931 the tunnel became the first underwater tunnel in Kolkata, carrying electricity lines between Howrah and Kolkata.

Though not for trains anymore, it is still in operation for electricity cables.

The country’s first-ever metro in Kolkata

Kolkata Metro, India’s first metro system and the fifth in Asia, began partial commercial service on 24 October 1984, as per HT.

It covered a distance of 3.40 kilometres with five stations between Esplanade and Netaji Bhavan, according to the metro website.

With inputs from agencies