According to the Hindustan Times, US-based professional services firm Louis Berger (now part of WSP) undertook a detailed project report in March 2020 for the country’s National Highways and Infrastructure Development Corporation.
When completed, it will be India’s first underwater tunnel and will span a river whose banks can be more than 5 miles (8km) apart during the rainy season.
Located close to the border with China, the tunnel will have huge strategic and military importance given it will provide year-round connectivity between Assam and Arunachal Pradesh. Existing bridges across the river are seen by the Indian military as easy targets for enemy fire.
Approval for the tunnel comes at a time of growing tension between India and China following a recent skirmish in which 20 Indian soldiers were killed.