Manual horizontal digging will start soon in addition to the ongoing top-down drilling to rescue the 41 trapped workers in the Silkyara tunnel in Uttarkashi, the NDMA said on Monday.
Manual drilling was resorted to as the auger drill -- a corkscrew-like device with a rotary blade at the front end -- which drilled up to 46.8 metres busted as it hit several hurdles on the way and got entangled in a girder in the debris.
"The broken blades of the auger machine have been fully retrieved. There were some obstacles while retrieving the broken part, but the damage has been fixed.
"Now, the manual drilling technique will be employed by today evening with the help of Indian Army engineers, rat miners, and other technicians," National Disaster Management Authority (NDMA) Member Lt Gen (retd) Syed Ata Hasnain told reporters in New Delhi.
Hasnain further said there will be a team of six members who will work in groups of three.
Vertical and manual horizontal drilling are the two methods on which rescue efforts are being focused at the moment. Work on the other options, such as horizontal drilling from the Barkot end of the tunnel is also underway.
A total of 86 metres have to be drilled vertically to prepare an escape passage. Pipes of 1.2 metres in diameter have to be laid vertically through the top of the tunnel on which work began on Sunday as a second option to reach the stranded labourers.
"Around 32 metres of vertical drilling has been done by SVNL. RVNL is working on another pipeline which will become a vertical 'lifeline' and it has been inserted up to 75 metres. The estimated depth is around 86 metres," he said.
He further said the government is fully committed to the safe rescue of all the 41 workers who have been trapped in the tunnel since November 12.
When asked about the timeline, Hasnain said, "It is very difficult to suggest any timeline for completion of rescue operations. Once the manual digging starts in the evening, we will able to say something tomorrow morning."
He noted that manual digging may face some obstacles.
"Once we are able to overcome them, progress will be fast," the NDMA member said, adding that however, "We cannot give any estimate" for the completion of the rescue operation and that both private and public agencies are involved in the rescue operations.
The NDMA member said according to a meteorological report, a yellow alert has been issued by IMD which means light rains can occur in 24-48 hours.
"But there is no possibility that work will be hindered because of this," he added.
Officers of various agencies such as NHIDCL, RVNL, SJVNL, ONGC, THDC, CIMFR, BRO, GSI, international experts and several private agencies briefed the Principal Secretary about the rescue works being carried out by their agencies.
Prime Minister's Principal Secretary PK Mishra, Home Secretary Ajay K Bhalla and Uttarakhand Chief Secretary S S Sandhu also took stock of the ongoing rescue operations. Hasnain said that Mishra has directed the authorities to ensure all medical facilities for trapped workers as "difficulties could increase with the passage of time'.
According to an official statement, Mishra advised the agencies to conduct the rescue operation with the utmost safety of men and machinery as well as with a fast pace of execution
Mishra emphasised that the Government of India would provide all types of support to various agencies/organisations of the country for this rescue operation, the statement added.
