Work begins on Mumbai’s deepest road tunnels

Chief minister Devendra Fadnavis on Tuesday inaugurated the launch of the tunnel boring machine (TBM) for one of the twin tunnels that will connect Orange Gate and Marine Drive in south Mumbai

Mumbai: Work has begun on Mumbai’s deepest road tunnels, which will run 50 metres below ground at their lowest point. Chief minister Devendra Fadnavis on Tuesday inaugurated the launch of the tunnel boring machine (TBM) for one of the twin tunnels that will connect Orange Gate and Marine Drive in south Mumbai. The second TBM is expected to arrive within a fortnight, officials said.

Mumbai, India. Dec 03, 2025 - The first Tunnel Boring Machine (TBM) for the Orange Gate to Marine Drive tunnel road project was launched in the presence of Chief Minister Devendra Fadnavis and Deputy Chief Minister Eknath Shinde at the front area, Princes Dock in Mumbai, India. Dec 03, 2025. (Photo by Raju Shinde/HT Photo) (Raju Shinde)

The 9.96-km twin tunnels, expected to be ready by December 2028, will reach their maximum depth beneath Chhatrapati Shivaji Maharaj Terminus (CSMT). Estimated to cost ₹8,056 crore, the project is expected to cut travel time between Orange Gate and Marine Drive by 15-20 minutes, according to officials.

According to officials from the Mumbai Metropolitan Region Development Authority (MMRDA), the depth of the tunnels would be anywhere between 12 metres and 50 metres. At CSMT, the tunnels will pass below the existing pedestrian subway that links the railway station to the Metro 3 station, which is 24-27 metres underground.

“This road tunnel will save 700 structures from getting impacted by the project, many of them heritage ones,” said Fadnavis at the TBM inauguration. “The upcoming coastal road tunnel between Orange Gate and Marine Drive in south Mumbai will save thousands of hours for thousands of people. This tunnel is expected to be ready by December 2028, but I have asked MMRDA to complete it by June 2028.”

The TBM, similar to the one used in the coastal road project, has been supplied by construction company Larsen & Toubro, the project’s contractor. The underground road tunnels will have approaches connecting Orange Gate, near the Eastern Freeway, to Marine Drive on Netaji Subhash Chandra Bose Road.

The nearly 10-km project includes around 7 km of underground roads and will pass beneath densely populated areas, crossing the Central and Western railway lines as well as Metro 3. Each tunnel will have two 3.2-metre-wide lanes and a 2.5-metre emergency lane, with a speed limit of 80 km/h. Cross passages will be provided every 300 metres for safety, along with fire-resistant systems, lighting, and a transport system for efficient traffic management.

The tunnels will integrate with both the coastal road corridor and Atal Setu.