All new roads lead to tunnelling machines?

Tunnel boring machines (TBM) are a highly-mechanised Earth Pressure Balance (EPB) device that are used around 20-25m below the ground to construct tunnels with a circular cross-section.

The 17 tunnel boring machines (TBM) brought to the city to create two tunnels for Colaba-Seepz Metro-3 may be used to create underground tunnels for four other road projects too.

Fifth tunnel breakthrough package 7 of Mumbai Metro 3 at Chhatrapati Shivaji Maharaj International Airport. (Pramod Thakur/Hindustan Times)

Good use for machines? Not really, say Opposition corporators, who claim the Brihanmumbai Municipal Corporation (BMC) and state administration are “manufacturing the demand” under the “influence of Metro-3’s TBM contractors”. The BMC and state, however, maintain the proposed projects are needed for the city.

TBM is a highly-mechanised Earth Pressure Balance (EPB) device that is used around 20-25m below the ground to construct tunnels with a circular cross-section. Of the 17 TBMs, each costing around ₹100 crore, four were brought from Delhi, while the remaining were imported from China. As of August 2, the MMRC has completed 31km of one-way tunneling, while the remaining 50% will be done in two years.

In the meantime, the contractors want the TBMs to be put to use for some other projects, so the machines are utilised and also monetised, Opposition corporators alleged. “There are whispers that a few people are pushing to divert the TBMs for the BMC’s proposed tunnelling projects. This should not happen. The BMC should conduct a feasibility study before going ahead with tunnelling. I am not against development, but it should happen, only if there is genuine demand. Demand should not be created by lobbyists,” said Ashraf Azmi, a Congress corporator.

The four other projects include the two underground ones at Juhu and Mahalaxmi, which were given a push in a meeting with municipal commissioner Praveen Pardeshi, citing traffic congestion. The BMC also recently floated bids for construction of the Goregaon-Mulund Link Road, for which TBM could be used. The technology can also be used for sewage water tunnels proposed in the city. Further, the Maharashtra State Road Development Corporation (MSRDC) headed by the Shiv Sena has also proposed Borivli-Thane tunnel below the Sanjay Gandhi National Park, which may be built using the TBM.

Ravi Raja, senior Congress corporator and leader of Opposition in the BMC, said there is no need for the corporation to look at so many road projects when the state has planned 13 Metro corridors. “Is the BMC looking at the feasibility of these tunnels? Mumbai already saw severe flooding this monsoon owing to Metro works. These projects will spell disaster,” he said.

Another Congress Corporator Javed Juneja, said, “Tunnel road projects are definitely an upgrade, but why are we failing at basic infrastructure even today? Our roads get flooded and are full of potholes after two days of heavy rain. Why not invest money and time on improving them?”

Sanjay Darade, chief engineer, bridges department of BMC, who attended the meeting where additional tunnels were proposed, was not available for a comment. “There is no question of creating demand. Tunnel projects will be taken up after preparing feasibility report, considering the financial and technical viability,” said an official from BMC.

Yashwant Jadhav, Shiv Sena corporator and BMC’s standing committee chairman, said, “I don’t have knowledge of any such thing. I can’t comment on it.”

Anil Gaikwad, chief engineer of MSRDC, also plans to make tunnels using TBMs for the Borivli-Thane project. “The institute has suggested using TBMs instead of rock-blasting to minimise the impact on the wildlife in the park,” he said, adding global tenders for the project will be floated shortly. “As this is a road project, we might not be able to use the TBMs currently in use for Metro-3,” Gaikwad said.

The project involves a six-lane tunnel from Magathane in Borivili to Tikuji-ni-wadi in Thane.

An engineer working for a private firm involved in construction of Metro-3 said, “A TBM being used for Metro-3 can be definitely used for other road projects. However, the diameter of the tunnel may vary, which can be adjusted.”

Explaining the logic, he said, “I am not involved in the finances and mobilisation of construction machinery, but it is obvious that the cost of transportation of TBMs, which weighs anywhere more than 600 tonnes, is very high. If the next assignment is in the same city, the mobilisation expenditure comes down and the profit ratio increases.”