Rohtang tunnel excavation, an engineering marvel, set to pick up speed

Manali (Himachal Pradesh), Nov 2 (IANS) The excavation of the Rohtang tunnel, one of India’s most strategically important infrastructure projects, is likely to pick up speed after missing its February 2015 deadline.

Of the 8.8-km horseshoe shaped Rohtang tunnel, an engineering marvel that will ensure all-weather connectivity to landlocked Lahaul Valley from Manali, about 5.2 km has been dug since work commenced in November 2011. Over 600 men and more than a dozen Indian and European engineers have been working day and night to excavate the tunnel, located at altitudes ranging between 3,053 and 3,080 metres on both sides, despite prevailing sub-zero conditions.

Engineers finally foresee the end of the loose strata that slowed down its construction for almost three years. A geological surprise in the form of a glacial-fed rivulet that sprung up in 2012 during work in the tunnel below the 3,978-m Rohtang Pass is still posing a challenge because of water seepage and fragile strata. But it has now been largely contained.

“We are close to covering the 600-metre highly fragile strata on the south portal (towards Manali) side. As per surveys, a solid rock is coming after 20 metres. The seepage and inflow of the Seri rivulet in the tunnel have been largely controlled,” project Chief Engineer Brigadier Manoj Kumar, who is associated with the Border Roads Organisation (BRO), told IANS.

The Seri is a tributary of the Beas river and flows down the mountain.

Kumar said in an interview that once the hard rock surfaces, the excavation would automatically pick up speed.

The project is estimated to be commissioned by 2019, and both ends of the tunnel — south and north portals — will meet by July 2017, he added.

The Rs.1,495-crore tunnel’s foundation stone was laid by Congress president Sonia Gandhi on June 28, 2010, in the picturesque Solang Valley.

Official sources told IANS that the delay in tunnel construction will mean a cost overrun of Rs.500-600 crore. The project is being built by the BRO in collaboration with Strabag-Afcons, a 60:40 joint venture between Strabag SE of Austria and India’s Afcons Infrastructure Ltd.

The north portal of the tunnel that lies towards the Lahaul Valley in Lahaul-Spiti district has already experienced snowfalls.

Kumar said work on the north portal would be stopped by mid-November because of the onset of heavy snowfall by then. However, work on the south portal towards Dhundi, 25 km from Manali, will continue during winter.

“The highest elevation in the tunnel that lies towards the north portal has been dug successfully. On that side, we encountered geological surprises in the shape of hot water springs and emission of toxic gases.

“But they were on a smaller stretch. They raised the temperature inside the tunnel,” he added.

The south portal is prone to flash floods and snow avalanches.

To counter them, the Snow and Avalanche Study Establishment (SASA) has designed several avalanche-control structures, including four snow galleries and eight snow bridges. One gallery has been constructed that was hit by a snow avalanche in February.

While a snow gallery would allow the avalanche to pass overhead without affecting the traffic inside, a snow bridge prevents the snow mass from rolling down the slope or break its flow.

Once ready, the Rohtang tunnel will be a boon for the cold deserts of Lahaul Valley, where over 20,000 people remain cut off from the rest of India in winter owing to the closure of the Rohtang Pass, a major attraction for both domestic and foreign tourists and located 52 km from Manali.

Besides reducing road distance by approximately 46 km and saving travel time of about four hours, the tunnel will open up new vistas of trade and tourism and generate jobs for the locals. The tunnel will provide ample room for two-way traffic and is designed to cater to a maximum vehicular speed of 80 km an hour.

(Vishal gulati can be contacted at vishal.g@ians.in)

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