Modi to unveil India's 1st underwater metro tunnel in Kolkata on Wednesday

PRIME Minister Narendra Modi is set to inaugurate India's first under-river metro tunnel in Kolkata on Wednesday. The tunnel, constructed beneath Kolkata's Hooghly River, will establish a connection between Howrah Maidan and Esplanade.

Key points on the Hooghly River underwater tunnel

• Kolkata Metro's Howrah Maidan-Esplanade section has India's first transportation tunnel beneath the Hooghly River.

• It is part of the East-West Metro, a 16.5 km stretch connecting Howrah on the west bank of Hooghly to Salt Lake City on the east bank. This marks India's first instance of trains running underwater.

• Executed by the Kolkata Metro Rail Corporation Limited (KMRCL), 10.8 kms of the stretch is underground, while 5.75 km is elevated on a viaduct.

• It aims to alleviate traffic congestion in the historic city of Kolkata, which has a history spanning 300 years while contributing to the reduction of vehicular pollution.

• Howrah metro station, part of the section, will be the deepest metro station in India.

• The metro is set to cover the 520-meter stretch under the river Hooghly in a remarkable 45 seconds, Live Mint reported.

• While the Esplanade-Sealdah stretch awaits completion, the Salt Lake Sector V to Sealdah stretch is already operational. The entire East-West alignment, spanning 16.6 km, is expected to commence commercial operations between Salt Lake Sector V and Howrah Maidan by June-July.

Kolkata got India's first metro, 40 years back

Kolkata Metro, India's first metro system and the fifth in Asia, began partial commercial service on October 24, 1984. It covered a distance of 3.40 km with five stations between Esplanade and Netaji Bhavan, according to the metro website.

Idea for an underwater train tunnel dates back to the British era

Harley Dalrymple-Hay, a Bengal-born British engineer, envisioned an ambitious 10.6km underground railway connecting Kolkata and Howrah over a century ago, BBC reported. The plan included a tunnel beneath the Hooghly River and 10 stops. However, due to funding challenges and concerns about the city's soil properties, the project was never realised, it added.

Later, in 1928, CESC, the city's electricity supply company, approached Harley to build a tunnel under the Hooghly for power cables. He accepted the challenge and the tunnel became Kolkata's first underwater tunnel in 1931, serving to transmit power cables between Kolkata and Howrah, the news report said.

It is still in use, albeit for power cables rather than trains.