The Mumbai Metropolitan Region Development Authority’s (MMRDA) Orange Gate–Marine Drive Urban Road Tunnel project has achieved a major tunnelling milestone, with the south-bound Tunnel Boring Machine (TBM) successfully crossing beneath seven operational Central and Harbour Railway tracks without affecting train operations.
The complex underground operation was carried out beneath one of Mumbai’s busiest railway corridors, with railway services continuing uninterrupted above the tunnelling zone.
24x7 Monitoring Ensures Safe TBM Operation Beneath Railway Corridor
According to MMRDA, the operation was executed under 24x7 instrumentation and survey monitoring, along with stringent railway safety protocols and close coordination with Central Railway and the Commission of Railway Safety.
The successful crossing marks an important engineering achievement for the project, which involves constructing twin underground road tunnels connecting Orange Gate with Marine Drive.
The tunnel is being constructed in challenging urban and coastal geological conditions and requires the TBM to pass beneath existing transport infrastructure, including railway corridors and Mumbai Metro Line 3.
Main tunnelling drive began earlier this year
The TBM, launched by Chief Minister Devendra Fadnavis and Deputy Chief Minister and MMRDA Chairman Eknath Shinde on December 3, 2025, is described as India’s largest slurry shield TBM deployed for an urban road tunnel.
Following its launch, the machine underwent a series of preparatory operations, including lowering and connecting its backup system to the TBM shield, completing hydraulic and electrical connections and calibrating flowmeters, densitometers and pressure sensors. A probe drill unit was also installed and tested.
The initial drive began on January 8, 2026, with temporary rings being erected. Permanent ring erection commenced on January 26, while the initial drive was completed on January 31.
The TBM transitioned to the main drive on February 26, with the main tunnelling operation commencing on February 28.
By March 26, the machine had excavated 70 metres of the planned 3,720-metre drive.
7-km twin tunnel project
The Orange Gate–Marine Drive project comprises twin tunnels spanning more than 7 km. The first tunnel under construction is around 3.45 km long and reaches depths of up to 52 metres.
The alignment passes beneath major existing transportation infrastructure, making construction particularly challenging in the densely built-up city.
Once completed, the project is expected to bring the travel time between Orange Gate and Marine Drive down to around five minutes. It will also provide an important east-west road connection, with integration with the Coastal Road and Atal Setu.
The underground link is expected to help reduce congestion on surface roads, while also lowering fuel consumption and vehicular emissions.
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