Mumbai’s Thane Borivali Twin Tunnel Project Gains Momentum as India’s Largest Hard Rock TBM Begins Work

Mumbai’s ambitious Thane Borivali Twin Tunnel project has reached an important construction milestone with the deployment of India’s largest single-shield hard-rock tunnel boring machine (TBM). The development marks significant progress on one of the country’s most technically challenging urban transport projects and is expected to transform connectivity across the Mumbai Metropolitan Region.

The twin tunnel project will connect Ghodbunder Road in Thane with the Western Express Highway in Borivali through an underground corridor running beneath Sanjay Gandhi National Park. Once completed, the project is expected to reduce travel time between the two locations from nearly one hour to around 15 minutes, offering substantial relief to daily commuters and commercial traffic.

The project consists of two parallel tunnels, each measuring about 10.25 kilometres in length with a diameter of 12.2 metres. Every tunnel will feature two traffic lanes along with an emergency lane, while cross passages will be constructed at regular intervals to improve operational safety. Engineers are using advanced tunnel boring technology to minimise surface disruption and improve construction efficiency.

A major highlight of the project is the deployment of the tunnel boring machine named Nayak, recognised as India’s largest hard rock TBM. The machine has been specially designed to excavate through the region’s difficult basalt rock formations. A second TBM, Arjuna, is also being prepared for excavation work, allowing construction on both tunnel bores to progress simultaneously.

Construction activities have accelerated after authorities completed the clearance of more than 500 structures required for the launch shaft on the Borivali side. Rehabilitation work for project-affected residents has also progressed, allowing engineers to begin full-scale tunnelling operations after several years of planning, approvals and preparatory work.

The Thane Borivali Twin Tunnel is among India’s most complex urban infrastructure projects because the alignment passes beneath the protected Sanjay Gandhi National Park. Extensive geological studies, environmental assessments and specialised engineering techniques have been incorporated into the project to reduce ecological impact while ensuring structural safety.

Beyond improving daily travel, the tunnel is expected to strengthen logistics movement across Mumbai by easing congestion on existing arterial roads. Faster connectivity between Thane and Mumbai’s western suburbs could improve access to residential, commercial and industrial districts, supporting long-term urban development across the metropolitan region.

Infrastructure experts believe projects such as the Thane Borivali Twin Tunnel demonstrate India’s growing capability in executing technically advanced underground transport infrastructure. The adoption of world-class tunnelling equipment, digital monitoring systems and modern construction practices reflects the country’s increasing focus on delivering large-scale mobility projects that support future urban growth.

As excavation progresses, the tunnel project is expected to become a benchmark for underground road infrastructure in India, showcasing how engineering innovation can alleviate congestion and improve connectivity in one of the nation’s busiest metropolitan regions.