New Delhi, The National High Speed Rail Corporation Limited (NHSRCL) is yet to float the tenders for the undersea tunnel for Mumbai-Ahmedabad Bullet train project. Seven Indian companies have shown interest for the construction of the underground station at BKC, Mumbai in the pre-bidding stage, officials said on Monday.

A NHSRCL official told IANS, "The tenders for the undersea tunnel is yet to be floated."

The bullet train project will have a 21-km long underground corridor from BKC to Kalyan Shilphata in the state of Maharashtra, of which around 7 km will be underground corridor under the Thane creek. Of this, a 1.8 km long section will be developed under the sea bed, while the remaining part of the stretch is to be built under the mangroves marshland on either side of the creek.

The official said that for the tunnelling work, which includes testing as well as commissioning for double-line high speed railway for the project using tunnel boring machine (TBM) and a new Austrian tunnelling method (NATM) is yet to be floated.

A geo-technical investigation of the undersea tunnel area was carried out earlier by a team of engineers from NHSRCL, RITES and Japan's Kawasaki Geological Engineering firm.

In order to study the sea bed structure, a static refraction technique (SRT) survey was carried out by the team, which involved firing a high energy sound wave towards the seabed from below the water surface as well as mapping the refracted sound wave in order to determine the density of the rock under the sea bed. The team had also submitted the final report with the NHSRCL.

The official further said seven Indian companies had participated in the pre-bid meeting for constructing the underground station at BKC.

The official said that the tender for the construction of the underground station at BKC has been floated and bids are invited till February 19, 2021.

The official said that the C1 tender for construction of the underground station, NIT was issued on November 20, 2019.

Last year, the NHSRCL awarded civil contracts for the construction of 64 per cent of MAHSR alignment which includes five HSR stations at Vapi, Billimora, Surat, Bharuch, Anand/Nadiad, train depot at Surat and one mountain tunnel of 350 metres.

The bullet trains are expected to run at 320 km per hour, covering the 508-km stretch in about two hours. Trains plying on the route take over seven hours and planes about an hour.

Prime Ministers Narendra Modi and then Japanese Prime Minister Shinzo Abe on September 14, 2017 had laid the foundation stone for the Rs 1.08 lakh crore ($17 billion) HSR project.