Manali, July 9 : The construction of one of the world's most challenging motorways - the Rohtang Pass highway tunnel - in the Himalayas of Himachal Pradesh is likely to be completed by 2020, according to the project engineers.
However, a daunting task ahead is to make the snow avalanche-prone roads, located at altitudes ranging above 3,000 metres and leading to the tunnel, safe for the motorists as well as accessible round the year.
For this, Chandigarh-based Snow and Avalanche Study Establishment (SASE) has designed mechanical structures to ensure the safety of motorists by countering avalanches on both ends of the tunnel that remain under snow even during peak summer.
The 8.8-km long horseshoe shaped tunnel - the world's longest motorable tunnel 3,000 metres above sea level, under the 3,978-metre Rohtang Pass in the Pir Panjal range - has 45 avalanche-prone spots and aims to provide all-season connectivity to the landlocked Lahaul Valley from the picturesque resort town of Manali.
Engineers of SASE, a Defence Research and Development Organisation (DRDO) laboratory, said that self-escape snow galleries have been designed for the safety of motorists after studying the local dynamics of avalanches like force and velocity.
It is for the first time that SASA has designed snow galleries.
SASE Scientist Rajesh Verma told IANS that three snow galleries are under construction at the tunnel's south portal from the Dhundi side.
The length of a gallery varies from 40 metres to 130 metres and would be constructed before the tunnel completion.
He said the other mechanical structures on the 12-km stretch towards the south portal are five deflector steel walls and a bridge to withhold an avalanche.
Likewise, a 250-m long catch dam is under construction towards tunnel's north portal to check erosion of falling debris along the road.
Official said sensors would be installed along both roads to monitor the behaviour of the snow and flashfloods round the year.
The most ambitious and expensive undertaking of its kind, the excavation of the tunnel was completed in October 2017. Now the civil engineering work is on.
An engineer involved in the tunnel construction told IANS that electrical and ventilation works are in progress.
"The tunnel most likely to be made operational by May-June 2020," he added.
The project is being undertaken by the Border Roads Organisation (BRO), a wing of the Defence Ministry, in collaboration with Afcons, a joint venture with Strabag AG.
Official sources said the tunnel had missed its February 2015 deadline owing to tough geographical conditions in the Himalayas along with harsh climatic conditions, besides a limited working season of six months in the tunnel's north portal.
But the delay of almost five years will face a cost overrun of Rs 2,000-2,500 crore.
Taming the glacial-fed Seri rivulet inside the tunnel was one of the biggest challenges for the engineers.
It's a tributary of the Beas river and the tunnel alignment is crossing beneath the rivulet.
Situated in the Pir Panjal ranges, the Rohtang Pass highway tunnel will provide ample room for two-way traffic and is designed to cater to a maximum vehicular speed of 80 km per hour.
Upon completion, it will also be a boon for the cold deserts of Lahaul Valley, where over 20,000 people remain cut off from the rest of the country in winter owing to the closure of the Rohtang Pass.
Besides reducing road distance by approximately 46 km and saving travel time of five hours between Manali and Keylong, headquarters of Lahaul-Spiti, 3,000 vehicles can ply per day in the tunnel under any weather condition.
The completion of the Rohtang tunnel is a key element in the Defence Ministry's attempts to make the entire 475 km-long Manali-Keylong-Leh highway, used by the armed forces to reach forward areas in Ladakh bordering China and Pakistan, motorable round the year, officials said.
The strategic importance of the Manali-Leh link was realised by the Indian government almost two decades ago when, during the Kargil conflict, Pakistan tried to cut off the Srinagar-Leh road in a bid to restrict road access to Ladakh.
Currently, the movement of armed forces to the forward areas in Ladakh from the Manali side, which doesn't fall within the firing range of Pakistani forces, is feasible only from June to mid-December.
(Vishal Gulati can be contacted at firstname.lastname@example.org)