Have you ever wondered how a train can run underwater? It sounds like something from a movie, but now it has become a reality. India’s first underwater metro tunnel has been completed in Kolkata and was opened to passengers in 2024. This unique project was built under the Hooghly River, and its technology and design are truly amazing.

Where is this tunnel located?
This tunnel is part of the Kolkata Metro East-West Corridor. Under the Hooghly River, this tunnel connects Howrah and Mahakaran (Secretariat) metro stations. This means that traveling directly from Howrah to the heart of Kolkata by metro is now just a matter of minutes.

What is the journey like underwater?
Traveling through the tunnel is a unique experience. When the train passes underwater, you won’t see the outside view, but it’s thrilling to know that the Hooghly River is flowing above your head. The entire underwater section is approximately 1.4 kilometers long, and the train crosses it in just 45 seconds.

How was this tunnel built?
A ‘Tunnel Boring Machine’ (TBM) was used to build this tunnel, specifically designed for underwater work. The machine cuts through soil on one side and covers it with concrete from behind to prevent water from entering.
The tunnel’s thickness is so strong that even the immense water pressure has no effect. ‘Waterproofing technology’ has been used, eliminating any risk of water leakage.

Why is this project special?
This is the country’s first underwater tunnel. Before this, a metro had never run underwater in India. Previously, traveling from Howrah to Kolkata took a long time due to traffic, but now the journey will be completed in just a few minutes. Carrying out such a massive engineering project underwater is extremely difficult, but it was made possible by a team of Indian and foreign engineers working together.

Focus on passenger convenience
Modern metro stations have been built at both ends of the tunnel, equipped with lifts, escalators, air conditioning, and full security arrangements. The trains are fully automated and controlled by an automatic control system, with special attention given to passenger comfort, including ample space, cleanliness, and ventilation.

Kolkata Metro East-West Corridor

The Kolkata Metro East-West Corridor is a major expansion of the city’s metro rail network, connecting the Howrah Maidan station on the west bank of the Hooghly River with the Salt Lake Sector V IT hub on the east. Its construction, which began in 2009, was a significant engineering challenge as it includes India’s first underwater metro tunnel, running beneath the Hooghly River. The line was partially opened in 2020 and is designed to drastically reduce travel time across the city.

Hooghly River

The Hooghly River is a vital distributary of the Ganges River in West Bengal, India, flowing past the city of Kolkata. Historically, it was a major shipping artery for European colonial powers, including the British East India Company, whose first settlement was established on its banks. Today, it remains a crucial commercial waterway and a sacred site for Hindu rituals.

Howrah metro station

Howrah metro station is a major underground station in Kolkata, India, serving as the western terminus of the East-West Metro corridor. It was constructed beneath the historic Howrah railway station, one of the oldest and busiest in the country, and provides a crucial modern transit link. The station’s development involved significant engineering challenges due to its location near the Hooghly River.

Mahakaran metro station

Mahakaran metro station is a key station on the Dhaka Metro Rail’s MRT Line 6 in Bangladesh, located in the city’s central business and government district near the Secretariat. It was developed as part of the country’s first mass rapid transit system, which began commercial operation in late 2022, to alleviate the city’s severe traffic congestion. The station’s name, “Mahakaran,” refers to the nearby Bangladesh Secretariat, the administrative heart of the government.

Secretariat metro station

The Secretariat metro station is a major transportation hub in Bucharest, Romania, located on the city’s M1 line. It was opened in 1979 and is named for the nearby Palace of the Parliament, which was historically known as the House of the People or the Republic’s House during the communist era. The station primarily serves the massive government building and the surrounding administrative district.

Tunnel Boring Machine

A Tunnel Boring Machine (TBM) is a colossal piece of excavating equipment used to construct tunnels with a circular cross-section through various ground conditions. While not a single site, its history is defined by its development in the 19th century, with the first successful TBM used by Marc Isambard Brunel to build the Thames Tunnel in London. This technology has since revolutionized underground construction for metros, railways, and roadways worldwide.

underwater metro tunnel

The underwater metro tunnel is a modern engineering marvel that allows subway systems to traverse beneath bodies of water. The first such tunnel was the 1896 Glasgow Subway, which crossed beneath the River Clyde, though the concept was pioneered even earlier with the Tower Subway under the River Thames in London (1870). These tunnels are complex feats of construction, often built using tunnel boring machines or immersed tube methods to create a sealed passage through challenging subaqueous environments.

Kolkata

Kolkata, formerly known as Calcutta, is the capital of India’s West Bengal state and was the capital of British India until 1911. Founded as an East India Company trading post in 1690, it grew into a major port and a center for education, science, culture, and politics. The city is renowned for its colonial architecture, vibrant arts scene, and as the home of iconic figures like Mother Teresa and Rabindranath Tagore.