In a push to Mumbai’s longest urban tunnel project, India’s largest TBM lowered for Thane–Borivali twin tunnel

The Thane-Borivali project involves constructing two parallel three-lane tunnels stretching 11.8 km beneath the Sanjay Gandhi National Park (SGNP). Once completed, the tunnels will link Ghodbunder Road to the Western Express Highway, reducing the current 60- to 90-minute commute to roughly 15 minutes.

Officials described the project as one of the most challenging undertaken in the Mumbai Metropolitan Region due to the sensitive ecology of the SGNP, the need for near-zero surface disturbances, and the requirement for continuous monitoring of geological shifts during excavation.

To meet these conditions, MMRDA has opted for advanced Single Shield TBMs designed to handle variable rock strata and high overburden. Two TBMs — ‘Nayak’ and ‘Arjuna’, procured from German manufacturer Herrenknecht’s Chennai facility- will be used to carve out the tunnels.

Work fronts of twin tunnel project

Casting yard operations: The Thane casting yard is fully operational, supplying precast segments for tunnel ring lining. The Borivali yard is under preparation and expected to begin operations in the coming months.

Land acquisition and rehabilitation: Acquisition is near completion on the Thane side, while rehabilitation of project-affected households in Borivali continues. Officials said delays in PAP shifts had slowed early construction, but progress has picked up in recent weeks.

Shaft construction: The Thane launching shaft, one of the deepest urban shafts in the region, has been excavated with controlled blasting and stabilisation measures to minimise vibration and noise.

The Borivali shaft is expected to reach its final depth next year.

The twin tunnels will house three lanes each, including an emergency lane, and will feature cross-passages every 300 metres for evacuation. Safety systems include an advanced ventilation network, firefighting lines, smoke detection, CCTV-based monitoring and LED signage for driver guidance.

Recognising the sensitivity of the SGNP span, MMRDA has deployed real-time environmental monitoring, vibration control systems, and groundwater regulation to prevent ecological disturbance. “The design and implementation have been planned to ensure zero encroachment and minimal impact on the forest cover,” an official said.

Once operational, the Thane–Borivali Twin Tunnel is expected to divert a substantial share of east–west traffic, easing load on the Ghodbunder corridor, Aarey Colony roads, and the Dahisar–Kandivali belt. The project is projected to reduce fuel consumption and emissions by cutting idling time for thousands of daily commuters.

Officials said the successful lowering of the TBM cutter head marks the start of the tunnelling phase, which will advance simultaneously from both ends. “This is a major milestone that signals Mumbai’s readiness to take up challenging underground mobility projects,” an MMRDA official said.

The project, part of a broader push to expand urban mobility infrastructure, is expected to reshape connectivity across the northern suburbs and significantly cut travel time for lakhs of commuters.