"About 7 km of the 21 km long tunnel will be undersea. We need to know the strata which is good enough for the tunnel to cross through," Achal Khare, MD National High-Speed Rail Corporation Limited said, reported news agency ANI.
"We have dug 66 boreholes about 250 metres apart from each other. To know the strata between these boreholes, we have got equipment from a Japanese Company, which is doing the work for us," Achal Khare further said.
Talking about the challenges Khare said-"The work here can be done only during high tides because the ground is very slushy. So working period is limited to only 4-5 hours. It is tough to control the boat along the Central Line which takes people to and fro, so Japanese have trained one of us to control it."
"We're aiming to complete project by 15th August 2022, which is the mandate given to us. The underwater tunnel will be started next year and will be completed by the end of 2022," he informed.
"Project is funded by Japanese Loan. 81% of the fund is being given by Japanese side. The loan is at a concessional rate of 0.1% for period of 50 years. It is a very generous term," he said.
About Mumbai–Ahmedabad high-speed rail corridor
The Mumbai–Ahmedabad high-speed rail corridor (bullet train) is an under-construction high-speed rail line and it will connect the cities of Ahmedabad, Gujarat and Mumbai in Maharashtra. The corridor will be India's first high-speed rail line, the construction of which began on 14 September 2017 as per schedule.
On 15 August 2022, the first bullet train is scheduled to leave for its first run and the corridor will use E5 Series Shinkansen, and will be operated by JR East.
Most of the corridor will be elevated except for a 21 km underground tunnel. The tunnel will be between Thane and Virar, of which 7 km will be undersea.