The technical bids were opened for the construction of a 21-km tunnel, having 7-km of length under water, as part of the Mumbai-Ahmedabad high speed rail line, popularly known as the bullet train project. For the C-2 package between Bandra-Kurla Complex in Mumbai and Shilphata in the Thane region, two proposals have been received from Afcons Infrastructure Limited and Larsen & Toubro Limited, according to a National High Speed Rail Corporation Limited. The financial bids will be available following the technical review, an official noted. The tunnel, which will have a diameter of 13.1 metres and will be a single-tube twin-track structure, will be built between 25 and 40 metres underground, according to NHSRCL, the organisation in charge of the complex project. Three tunnel boring machines (TBMs) will construct 15.42 kilometres of the structure's 20.37 kilometres, while the remaining 4.96 kilometres of the structure will be constructed using the New Austrian Tunnelling Method (NATM). “The tunnel will cross Thane creek and the survey work under the creek was done using underwater static refraction technique and was successfully completed. The NHSRCL has showcased facade designs of Bandra Kurla Complex, Virar, Boisar, and Thane stations in Maharashtra”, an official said.