NEW DELHI: The government is exploring the option of constructing a strategic tunnel under the Brahmaputra river in Assam for unhindered movement of military vehicles.The tunnel would be located on the upstream of the Brahmaputra near Tezpur in Assam, connecting north and south banks of the river, top government officials said. Its length is expected to be 12-15 km and may have both rail and road networks or just the latter, depending on construction difficulties and gradient.The main reason for planning such a tunnel is that the strategic bridges connecting different areas in Assam and Arunachal Pradesh and along the Line of Actual Control (LAC) with China are vulnerable to interference by the northern neighbour, the officials said. They claimed the tunnel would ensure complete protection to military convoys. As depth and course of the Brahmaputra keep changing, the most likely option is to construct the tunnel under the river bed, the officials said.“We are exploring the option of having a tunnel under the Brahmaputra. It will be anywhere on the upstream of the Brahmaputra near Tezpur, connecting north and south banks of the river,” said an official. “It could be rail or road link, or both, and will be about 12-15 km long. It could, most likely, be under the bed, because the channel changes.”A detailed project report is still to be conducted, but a map survey has already been done. Another official said: “The tunnel is possible and we have the capability to go 20-30 m under the bed or even deeper.”The official said a construction survey will throw more light on whether both rail and road networks are possible. “The gradient for both are different, especially for rail.”Since the Brahmaputra is the main obstacle to troop movement from south to north banks and further towards Arunachal, the tunnel will ensure unhindered connectivity to RALP (‘Rest of Arunachal Pradesh’ in Army’s parlance).Existing bridges, such as the Deopani Bridge between Arunachal’s Lower Dibang Valley and Upper Dibang Valley with Assam, remain exposed to enemy missiles. Other such structures are: the Dhola Sadiya Bridge across the Lohit river, linking Tinsukhia in Assam with Roing in Arunachal, and the Bogibeel Bridge connecting Pasighat with Dibrugarh.