Bullet train: Bids invited for India’s first undersea tunnel

VADODARA: The National High Speed Rail Corporation Limited (NHSRCL) has issued tender for India’s first undersea tunnel, which is part of the ambitious Mumbai-Ahmedabad bullet train corridor.
The bullet train which will cover a distance of 508 km between Mumbai and Ahmedabad has a 21 km underground corridor from BKC to Kalyan Shilphata in Maharashtra. Of this, 7km is under the Thane creek, with 1.8 km of it to be built under the sea bed and the remaining under the mangroves marshland on either side of the creek.

The tender which was released on Tuesday is for construction of tunnelling works including testing and commissioning for double line high speed railway using tunnel boring machine (TBM) and new Austrian tunnelling method (NATM) for the project.

Going by the tender, the work has to be completed within 1,280 days or 3.5 years. A team of engineers from NHSRCL, RITES Ltd and Japan’s Kawasaki Geological Engineering had carried out a geo-technical investigation of the undersea tunnel area last year. The team had carried out a static refraction technique (SRT) survey to study the seabed structure. It involved firing a high-energy sound wave towards the seabed from below the surface of the water and mapping the refracted sound wave to determine the density of the rock under the sea bed. The final report was submitted last year.

Clearing air over the environmental clearances required for the project, NHSRCL officials said that India’s apex institutes including the Zoological Survey of India (ZSI), the Mangroves Survey of India (MSI) and the National Institute of Oceanography (NIO) have studied environmental impact of the project in the said area. “ZSI in its report had stated that there is minimal disturbance to the wildlife in this region. There will be no mangroves being cut in this area as it will be an undersea (underground) tunnel 20 to 40 metres below the ground (sea level),” said a NHSRCL official.

“All environment related clearances from the respective authorities including the Coastal Regulation Management Authority, the National Board of Wildlife and the forest department are either received or authorities have principally agreed for the approval,” the official said. Last month, NHSRCL had invited bids for 237km out of 50-km-long project – which was the biggest ever contract for civil construction in the country.