Ground penetrating radar has also been used to check for obstacles.
Only 10-12 metres of drilling is left for rescuers to reach the 41 construction workers trapped in the Uttarakhand tunnel for the 13th day now, but giving a timeframe for the rescue is difficult because unexpected hurdles have been delaying the work, senior officials said on Friday afternoon.
There may be light at the end of the tunnel after all, however, as ground penetrating radar has revealed that there are likely to be no major metal obstacles for the next five metres that will be drilled in the next few hours. The officials also said that, if all goes well, pushing in two more pipes may be enough to reach the labourers.
Addressing a press conference, Additional Secretary Technical, Road and Transport, Mahmood Ahmed and Uttarakhand Secretary Neeraj Khairwal, who is the nodal officer for the rescue operation, said the auger machine hit a metal pipe on Thursday evening which wrapped itself around the drilling blades. They said many hours had to be spent repairing the machine's blades, strengthening the platform on which the machine is operating and removing the metal girders and pipes which were obstructing the operation.
Mr Ahmed said that, before drilling resumes, some welding will need to be done, which will take about two hours. He explained that the welding process is a complicated one and needs to be done carefully so that the area being welded stays strong.
Explaining one reason for the delay, Mr Khairwal said, "Since 4 pm yesterday to now, time was spent strengthening the platform, which had moved. The mouth of one of the 800 mm pipes that had been pushed in by us had narrowed and we actually had to cut about 1.2 metres of it. Three metres of pipe had been pushed in yesterday in addition to the 45 metres before, but 1.2 metres of this had to be cut because the auger would not have been able to proceed further."
The distance covered by the pipes is currently 46.8 metres because 1.2 metres had to be removed.
Mr Khairwal said cutting the pipe as well as vertical pipes from the tunnel's ceiling that were obstructing the drill took seven to eight hours and while people thought that the auger machine had broken down, that was not the case. In the meantime, a team of ground penetrating radar experts was called in and one of their men took 45 minutes to travel inside the pipes for 45 metres and take their measuring machine inside.
"The narrowing of the end of the pipe meant they could not say this with 100% accuracy but what they are expecting is that there is no continuous metal object, like girders, pipes and metal plates, in the next 5.4 metres. They have pointed out some other hurdles, but this is good news," he emphasised.
The bigger 700 mm auger is going to be used now that the pipe has been cut, Mr Khairwal said, adding that the hope is that the work will be completed at the earliest. "The first hour of drilling after the welding is done will be critical," he said.
Mr Ahmed said, if all goes well, pushing in and welding two pipes with a length of 6 metres each should be enough to "break through" to the workers but this is an assumption based on their assessments. He cautioned, however, that obstacles and hurdles can still appear at any point.
To a question on whether teams could reach the workers by Saturday morning, the official said it could happen even sooner if everything goes smoothly.
The under-construction tunnel in Uttarkashi is part of the ambitious Char Dham project, a national infrastructure initiative to enhance connectivity to the Hindu pilgrimage sites of Badrinath, Kedarnath, Gangotri, and Yamunotri. The labourers got trapped when a portion of the tunnel had collapsed on November 12.