'Vertical drilling more time consuming'

Efforts are also being made to create a vertical escape passage, officials said. A big drilling machine was moved towards the hill above the tunnel on Saturday morning where two lowest elevation spots have been identified by experts for vertical drilling. A 1.5-km access road to the top of the tunnel has already been built by the Border Roads Organisation (BRO) as the option of vertical drilling has been on cards for some time.

Vertical drilling is a more time-consuming and complicated option which demands more exactitude and caution due to narrower space available on top of the tunnel roof, international tunnelling expert Arnold Dicks had said a few days ago.