TBM Dhruv completes Final Tunnel Breakthrough for Mumbai Metro Line 7A

Mumbai, India (Metro Rail Today): In a major milestone for Mumbai Metro Line 7A, J Kumar Infraprojects Ltd. on Monday (14th July 2025) celebrated the breakthrough of Tunnel Boring Machine (TBM) Dhruv at the Airport Colony Shaft, marking the completion of all mainline tunneling works on the 3.17 km underground section between Gundavali and Chhatrapati Shivaji Maharaj International Airport (CSMIA).

TBM Dhruv (T60), a Ø6.68m dual-mode Terratec machine, had previously been used on Mumbai Metro Line-3 (Aqua Line) by the J Kumar–CRTG JV between 2018–2021. It was refurbished at J Kumar’s Ghodbunder Road yard before being redeployed in November 2023 from the shaft at CSMIA Terminal 2 Station.

Over the past 19 months, the machine constructed a 1.65 km up-line tunnel to the Airport Colony Ramp, passing over Line-3’s twin tunnels and under key urban infrastructure including the Sahar Elevated Access Road (SEAR) and critical utilities.

This is the first and only breakthrough for TBM Dhruv on this project. Its parallel TBM, T62 (Disha), had completed tunneling of the down-line tunnel in April 2025, also at the Airport Colony Shaft. With Dhruv’s arrival, mainline tunneling works on Line 7A are now complete, with only cross-passages pending before full civil completion.

Mumbai Metro Line-7A is a crucial underground extension of the operational Red Line (Line-7). The Mumbai Metropolitan Region Development Authority (MMRDA) had awarded the ₹1,998 crore Package CA-48 to J Kumar Infraprojects in September 2019. The package includes:

• Construction of the underground ramp and twin tunnels

• Two underground stations at Airport Colony and CSMIA Terminal 2

• A viaduct connecting to the elevated Line-9 extension

Once completed, Line-7A will provide interchange connectivity with Line-3 (Aqua Line) at Terminal 2, and eventually with the upcoming Line-8 (Gold Line) to Navi Mumbai International Airport.

With tunneling now completed, the focus will shift to system installations, station architectural finishing, and safety testing. Given Mumbai’s complex urban environment and project execution timelines, Line-7A is expected to be operational no sooner than Q3 2027.