Why the Thane-Borivli tunnel under Sanjay Gandhi National Park (SGNP) is Mumbai’s most daring engineering feat yet

The Thane-Borivli twin tunnel project is entering its most challenging phase — boring through the eco-sensitive Sanjay Gandhi National Park (SGNP). The work will begin in the coming weeks under the supervision of the Wildlife Institute of India (WII), Dehradun, to ensure minimum environmental disturbance. (PHOTO CREDIT: AI)

Implemented by the Mumbai Metropolitan Region Development Authority (MMRDA) and executed by Megha Engineering and Infrastructures Ltd (MEIL), the project aims to significantly reduce travel time between Thane and Borivli. The construction has a completion target of late 2029 and has now gained momentum after the monsoon slowdown. (PHOTO CREDIT: AI)

The excavation of the Thane shaft, needed to lower two Tunnel Boring Machines (TBMs) from Chennai, is nearing completion. These TBMs are expected to start operations soon, advancing steadily through the hilly terrain beneath SGNP once the ramp setup is fully ready for deployment. (PHOTO CREDIT: AI)

Officials said each TBM would progress at an average speed of 11 metres per day at a depth of around 60 metres. The machines are equipped with advanced technology designed to limit vibrations and prevent surface disruption, ensuring that tunnelling remains safe for both wildlife and surrounding areas. (PHOTO CREDIT: AI)

Since the tunnel runs below SGNP, special care is being taken to protect its wildlife. The Wildlife Institute of India (WII) will oversee the entire drilling process, monitoring and recording its environmental effects. Strict safeguards have been implemented to maintain ecological balance throughout the construction phase. (PHOTO CREDIT: AI)

Land acquisition at the Thane end is almost complete, with rehabilitation of affected families progressing at Borivli. Authorities have emphasised fair compensation and resettlement for residents impacted by the project, ensuring that development takes place alongside proper social responsibility and local cooperation. (PHOTO CREDIT: AI)

The casting yard at Thane is fully operational, while work on the Borivli yard is ongoing. These yards will produce concrete tunnel segments that will be installed as boring progresses. After delays during the monsoon, production and logistics activities have now resumed at full capacity. (PHOTO CREDIT: AI)

Once finished, the 11.8-kilometre twin tunnel will link Ghodbunder Road in Thane with the Western Express Highway in Borivli. The direct underground route is expected to cut the current 90-minute journey between Mumbai’s eastern and western suburbs to only 15 minutes, easing congestion dramatically. (PHOTO CREDIT: AI)

Each tunnel will have three lanes — including one emergency lane — and cross-passages every 300 metres for safety. Additional features will include modern ventilation systems, fire-fighting mechanisms, smoke detectors, and LED signboards that provide real-time updates to drivers for smooth and safe travel. (PHOTO CREDIT: AI)

Authorities have assured that the project’s execution focuses on balancing development with environmental protection. The use of modern TBMs, minimal surface impact, and close wildlife supervision make this one of India’s most eco-sensitive infrastructure projects, blending technology with sustainability goals for long-term urban mobility. (PHOTO CREDIT: AI)