Drilling for Bullet Train by next March

Mammoth drills are expected to pierce the earth in Mumbai for India's first Bullet Train by March next year. Project executor National High-Speed Rail Corporation Limited, which is still acquiring land for the rail link between Mumbai and Ahmedabad, has called tenders for tunnelling work between Bandra-Kurla Complex and Shilphata.

The development comes close on the heels of Rs 10,000 crore being set aside in this year's Union Budget for the high-speed rail estimated to cost Rs 1.08 lakh crore.

The tenders, floated a few days ago, pertain to two legs of the construction for which August is the deadline. One, an underground railway station at BKC; two, a double line from BKC via Thane and Palghar districts in Maharashtra. For the works, tunnel boring machines will go 30-45 metres deep into the earth, drilling through basalt rocks, even under the Thane creek, thus kicking off the project.

Together, the tunnels will be 26 kms long, and the single longest one will run 21 kms underneath the Thane creek. The closest it will come to the creek's abyss will be about 10 metres, marking the route's deepest point.

"We will open the tenders after September. It will take a few months to select the contractor. If all goes to plan, then the work can start at the end of this financial year," said Achal Khare, the managing director of NHSRCL.

Senior railway officials looped in on the project said tunnelling will be carried out at BKC, Vikhroli, Savli and all the way till Shilphata. The tunnels will be 17.5 metres in diameter, or twice the size of the metro rail tunnels being dug across the megapolis. Nearly 13 metres of the width will be occupied by two parallel tracks, running up and down through the city towards Gujarat.

Three tunnel boring machines (TBMs) and three New Austrian Tunnelling Method (NATM) machines will be pressed into service for the task.

"We anticipate generating 40 lakh cubic metres of muck from the tunnelling work. It will be used to level Parsik Hill and plant trees, as the area has lost much of its green cover over the years," said an official. Incidentally, more than 53,000 trees will have to be sacrificed for the rail, as the government informed the Rajya Sabha last week.

Tough to crack

Drilling the tunnels is not a tough job. It is creating a three-to-four-storey underground station at the bustling commercial hub of Bandra Kurla Complex that the NHSRCL is worried about. The G-block, where the station will come up 30 metres below, is surrounded by skyscrapers occupied by multinational companies, private banks and other commercial offices. On the same land, the Mumbai Metropolitan Region Development Authority (MMRDA) will be constructing the International Financial Services Centre.

Sources said that vertical excavation on reclaimed land is a concern, as drilling should not weaken the buildings there. "We have already begun work of checking the physical condition of buildings in BKC," said a senior railway official.

Furthermore, since BKC is near the Mithi River, it would be difficult to drill down here as soil would be softer. This work alone will generate 8 lakh cubic metres of muck, whose disposal is a big question. Construction of the station itself will require a humongous 2.5 lakh cubic metres of cement and 75,000 tonnes of steel.

"There is limited space for constructing this railway station as Metro rail work is underway parallelly. The Metro rail yard is also there. Then there is a 45-metre wide road in the middle which sees continuous traffic," said a rail official.

There are about 30 utility conduits – gas, water, sewer pipes, electrical and communication lines — passing underground, besides other things. There is also a petrol pump. All of this will have to be shifted.