Mavala—the Tunnel Boring Machine (TBM) which earned its reputation for digging the country’s first ever undersea twin tunnels in Mumbai is soon to be deployed for a new assignment aimed at improving Mumbai’s connectivity.

According to civic officials, Mavala will be used for boring underground twin tunnels that will connect Orange Gate with Marine Drive. These tunnels will commence near the Eastern Freeway drop at Orange Gate and will extend towards the western side of the island city. This proposed project has been taken up by Mumbai Metropolitan Region Development Authority (MMRDA) and the contract for executing the project has been awarded to Larsen and Toubro (L&T).

The Maharashtra Coastal Zonal Management Authority (MCZMA) also gave its nod to MMRDA last year for going ahead with this project.

The proposed 6.5–km tunnels will each be able to accommodate two lanes along with one emergency lane and pedestrian walkway.

Earlier, Mavala was used for digging twin tunnels of 2.07 km each, as part of BMC’s ambitious Mumbai Coastal Road Project (MCRP). These tunnels extend between Marine Drive and Priyadarshini Park (PDP) and run beneath the Arabian Sea and Girgaon Chowpatty beach, thus becoming the nation’s first undersea tunnel.

The digging of the MCRP tunnel was completed on May 30 last year, taking the Mavalas a little more than two years to finish digging the two tunnels. The TBM at present is dismantled and stationed at the Priyadarshini Park site of MCRP where it is undergoing routine maintenance checks.

“During the MCRP tunnel boring operation, the spokes of the cutter head underwent wear and tear which are being scrutinised and repaired. Since the machine had to cut through complex geological components, such wear and tear is a normal phenomenon,” said an official.

The diameter of the coastal road tunnels are 11 metres each and the proposed diameters of the Orange Gate to Marine Drive tunnel is also 11 metres. “The tunnel diameter of both projects is the same, and the executing agency of both projects is also the same, that is L&T. Therefore, this same machine will be used in the project, as other TBMs currently deployed for different projects like Mumbai Metro, are smaller in size, and don’t fit the requirement of the diameter. Also, the TBM is in a good and workable condition,” the official said.

The MMRDA tunnels are being planned to ensure seamless connectivity between the east and west coast of south Mumbai and will provide direct connectivity towards and from Eastern Freeway, Marine Drive and MCRP.

Manufactured by China Railway Construction Heavy Industry Corp (CRCHI), the TBM was named ‘Mavala’ after Chhatrapati Shivaji Maharaj’s mountain warfare experts hailing from the indigenous Koli and Kunbi communities. Weighing more than 2,800 tonnes and 12.19-metre diameter, Mavala is the largest TBM that has been used to dig a tunnel in the history of India.

Mavala arrived from Shanghai in April 2020 to Mumbai’s Jawaharlal Nehru Port. The massive machine was dismantled and brought to Priyadarshini Park in 17 trucks.

Thereon, BMC assembled the TBM and brought it to the launching site in a 200-wheel self-propelled transporter and freight wings. Civic officials said it took them three months to assemble the entire TBM.

Followed by much fanfare, the boring of the first tunnel of MCRP began in January 2021 and the digging was completed in January the next year. Later, mining for the second tunnel was begun in April, 2022 and by April 2023 it was completed. During this course the TBM continuously mined through complex geological elements like breccia, basalt and shale.