The civic body has written to Chief Minister Devendra Fadnavis seeking approval to launch the machine and officials said they aim to begin work once approval is received.
The project is pegged at Rs 140 billion (Rs 140 bn) and is intended to provide a direct east-west link between Goregaon and Mulund, connecting the western suburbs with the Eastern Express Highway.
The GMLR spans 12.2 km and its most complex component is a 6.65 km twin tunnel that will begin near Film City and pass below the Sanjay Gandhi National Park.
The alignment will run under forested terrain, hillocks and the Tulsi and Vihar water catchments before emerging near Khindipada in Mulund.
Two TBMs are in place to carry out the subterranean excavation and are expected to excavate a combined length of 4.45 km, while assembly of the second machine continues.
The first machine on the northern alignment will form the carriageway for traffic travelling from Goregaon towards Mulund and the second will serve the opposite direction.
A tunnel boring machine operates through a rotating cutter head fitted with teeth, spokes and protrusions that cut through soil and rock as the machine advances, enabling continuous mechanised tunnelling in varied ground conditions.
The first consignments of the Japanese-made machines arrived in July 2025 and officials have proposed naming the two machines Tulsi and Vihar, with a formal request submitted to Municipal Commissioner Ashwini Bhide.
The broader GMLR programme is scheduled for completion by 2028 and is divided into four phases encompassing road widening, flyover construction and elevated interchanges.
The second phase includes the TBM-driven tunnels and western suburb flyovers, followed by a road-over-bridge at Nahur and an elevated flyover with clover-leaf interchanges up to Airoli.
With assembly nearing completion and approvals pending, the civic body has moved into the tunnel excavation phase that will determine the pace of subsequent works.