Uttarkashi tunnel rescue: After major setback, rescuers begin vertical drilling
The Indian Army has also been tasked with carrying out the manual drilling operation to remove the metal obstructions in the Silkyara tunnel in the final phase of the rescue operations
After facing multiple setbacks time and again as the American auger drilling machine suffered irreparable damage, rescuers on Sunday began vertical drilling atop the hill to evacuate the 41 workers trapped inside the Silkyara-Barkot tunnel in Uttarkashi since November 12 morning.
The blades of the auger machine, which was being used for drilling, hit a metallic grinder in the rubble of the collapsed rubble and broke down and got stuck in the rescue pipes which were being pushed through the debris to create a passage, putting a halt to the rescue operations for the third time in 15 days.
The vertical drilling machine arrived at Silkyara on Saturday evening and was prepared overnight to commence the drilling on Sunday morning.
Officials are now shifting focus to two alternatives — manual drilling through the remaining 10 to 12-metre stretch of the rubble or drilling down 85 to 90 metres from the top of the mountain.
“We have now come to a stage where we started working on 2-3 more options since yesterday (Saturday). The Satluj Jal Vidyut Nigam Limited (SJVNL) is doing vertical drilling of a 12-metre diameter for us for the evacuation of trapped men. We identified spots where the drilling could be better...The drilling of almost 15 metres is complete, and 86 metres has to be done. We think that this will be completed in 100 hours (next four days) if there is no obstacle. One machine can only drill for 45 metres. We will have to change the machine,” Mahmood Ahmad, additional secretary, ministry of road transport and highways of India and managing director of National Highways & Infrastructure Development Corporation Limited (NHIDCL), said while addressing a press conference here on Sunday.
SJVN Limited is a joint venture between the government of India and the government of Himachal Pradesh. The company has been involved in the construction and operation of several hydroelectric power plants in India, with a focus on the Himalayan region.
The Rail Vikas Nigam Limited (RVNL) has also been asked to do a horizontal drilling for 180 metres, but that involves risks, officials aware of the development said.
“The machinery has arrived. The concrete bed is about to be ready. We will start this drilling on November 28. It can take 12-14 days to complete at a rate of 12 metres per day,” Ahmad said.
“The Thermal Power Corporation Limited (THDC) is doing a drilling from Barkot side. They have already created a drift of 10 metres. They have to drill for 483 metres. It can take a long time,” Ahmad said, adding he also spoke with the chairman and managing director of THDC to know if they have any other equipment which can drill at a faster rate.
When asked if vertical and manual drilling would be done simultaneously, Neeraj Khairwal, Uttarakhand government secretary, said, “We have also consulted experts to know about the hazards if the work on different plans is undertaken simultaneously. Sensors have been installed to monitor vibrations. If working on one plan will hamper another, we will take a call.”
Responding to a question about the escape passage, Ahmad said, “The same question is in our mind as well. A committee has been constituted…we will come to findings. However, our priority is to rescue 41 trapped men.”
An RVNL official involved in the rescue operation on the condition of anonymity said that drilling from the hilltop may impact the stability of the tunnel.
“There is a risk of the tunnel collapse or further structural damage, especially if the construction of the tunnel was not completed or if the tunnel is not adequately supported…maintaining communication between the drilling team and the trapped workers inside the tunnel is crucial,” he said.
On the possible risks in vertical drilling, Khairwal said, “All geologists have given their recommendations to us. But 100% assurance is not possible about anything. Each and every aspect is being looked into.”
“As you know, the auger machine failed, and we are having many technical difficulties in getting the auger out of the pipe. That is going much faster this morning as plasma cutters have come. Brave men are going in there in a pipe with plasma cutters and cutting it piece by piece…..The progress is faster this morning,” international tunnelling expert Arnold Dix told media persons on Sunday.
He added, “We are less than 10 metres away (from the trapped men). But it is as if it could be a thousand kilometres away. Because we still exactly don’t know what’s in there. We don’t know if it is girders or it is machines. We have used ground penetrating radar (GPR). We have been very conservative making sure no one is hurt. We do not want to jeopardise the men on the other side as well.”
The vertical drilling has commenced, and if all goes to plan, this will be the final phase of the operation, he said.
Meanwhile, the Indian Army has also been tasked with carrying out the manual drilling operation to remove the metal obstructions in the Silkyara tunnel in the final phase of the rescue operations.