Challenges in Locating the Tunnel Entrance

The rescue operation at Trishuli 3A Hydropower Station faced an initial hurdle in locating the tunnel entrance, which had been buried by an avalanche after last week’s flash flood on the Nepal-Tibet border. The flood has so far killed 1,300 people and rendered the scene nearly unrecognizable.

Arnold Dix, president of the International Tunnelling and Underground Space Association, who has been advising Nepal’s hydropower authorities, said the entrance to the tunnel, previously up the hill, was now underground. He explained that they used engineering techniques, old topographic maps, satellite imagery, helicopter footage, and surface markers like power poles to triangulate the entrance’s likely position and start digging.

Clearing the Obstacles

Once the entrance was found, the next challenge was to locate the survivors; Rescuers had to deal with through a tunnel completely blocked by mud and rocks, some larger than cars. To clear the path, they used explosives, something Dix said they would ‘normally never do because of the risk of blowing up people [trapped in the tunnel] and blowing ourselves up.’

Dix credited the Nepalese army for managing the explosions with precision to avoid destabilizing the tunnel, though At the same time, they discovered that the tunnel was still full of water. Using excavators and pumping machines, rescuers dug trenches from the tunnel to the river outside to drain the water.

Finally, they created a passageway, ‘a tiny tunnel the size of a person,’ through the debris at the top of the tunnel. The advantage of this location, according to Dix, is that the original tunnel’s roof can serve as the new tunnel’s roof, reducing the risk of flooding.

Successful Rescue and Ongoing Efforts

In the early hours of Friday morning, rescuers heard what they believed were voices, though they called out, ‘don’t worry, we’re here to rescue you,’ and heard a faint ‘okay’ in response. Shortly after, they pulled out Sanjaya Shah and Kabir Maharjan, who were alive.

With dozens of people still thought to be trapped inside the tunnel, the work is far from over. Dix estimated that they had dug about 60 meters from the entrance and would need to dig another 150 meters to reach the hydropower station located deep inside the mountain. The team is hoping that the flood debris did not reach the station, as it could have been hit by rocks, mud, or flooding.

Rescuers continue to face significant dangers. ‘Up ahead, even now, we might run into water which would drown the people tunnelling,’ Dix said. ‘And we also have the risk of another flood outside happening, so water could come from behind. So there’s the risk of facing water on both ends.’ However, the team is now hopeful after Friday’s successful rescue.

‘It’s a big relief, that we are on the right track,’ Dix said. ‘And it gives us renewed energy that our thinking [on how to conduct the rescue] works… we have never done something like this before.’

Dix said the team is now heading towards what he called the ‘Goldilocks zone,’ which would be ‘more friendly to life.’ This zone is at the uppermost level of the hydropower station where there is some space where survivors may be located. ‘We got two people out. If we were playing at a casino, some might say it’s time to walk away, but we say game on, time to take on the house.’