By 2023, Mumbai will be home to India's first undersea tunnel, part of the city's Rs 12,000 crore Coastal Road project.The Coastal Road project is an under construction 22.2-kilometre freeway that would run along Mumbai's western coastline connecting Marine Lines in the south to Kandivali in the north.

KEY HIGHLIGHTS:

=> The 2.07 kilometre tunnel, which will have two lanes, will be 10 to 70 metres deep sub-surface. These lanes will be bored between Priyadarshini Park and Chhota Chowpatty at Marine Drive.

=> The tunnels, having a circumference of 11 metres each, would be earthquake-resistant and have a life span of more than 120 years. The tunnels will have three lanes on each side and will get a coat of reflective paint to ensure adequate lighting.

=> In case of disaster, 13 cross tunnels would be opened up. Of the 13, seven cross tunnels would be for vehicles and six for human movement.

=> The drainage system includes drains along the carriageway with fire traps located every 50 metres to collect seepage, fire hydrant discharge and oil spillage from vehicles.

=> A novel ventilation system called Saccardo will be installed inside the tunnel to monitor emission levels. The system will shoot an air jet through large ventilation fans to drive out the fumes in the desired direction.

=> The tunnel is being made using 'Malva', India’s biggest Tunnel Boring Machine (TBM). Soldiers of 17th Century Maratha king Chhatrapati Shivaji Maharaj were called 'mavlas'. The machine, which is operated by a team of 30 people, has a diameter of 12.19 metres.

=> At 20 metres below the sea bed, Mumbai’s undersea tunnel is being constructed at a relatively shallow depth. In comparison, the English Channel Tunnel at its deepest point is 75 metres below the sea bed, while Japan’s Seikan Tunnel lies over 100 metres below the seabed.

=> According to the Brihanmumbai Municipal Corporation (BMC) officials, once completed, the Coastal Road will cut down the travel time between south and north Mumbai, decongest existing roads and reduce the air and noise pollution levels.