Rescuers at Silkyara tunnel have crossed the 50-metre mark and they need to dig through around 10 metres of rubble using rat-hole mining technique to bring out the 41 workers trapped there for the last 16 days.
Twelve rat-hole mining experts are involved in the horizontal excavation through the last 10 or 12-metre stretch of debris of the collapsed portion of the under-construction tunnel on Uttarakhand's Char Dham route.
This drilling was earlier carried out by a huge auger machine that got stuck in the rubble on Friday at around 47 metres.
"We have just crossed 50 metres," L&T team leader Chris Cooper told PTI on Tuesday. It raises hopes of an early evacuation as rescuers have to go only up to 10 metres to make a breakthrough.
However, the speed of the operation depends on whether or not the rescuers encounter any hurdle in the course of excavation which has often been hampered by something or the other.
WATCH: First visuals of manual drilling inside collapsed Silkyara tunnel
A skilled team of workers is doing muck removal by hand using the rat hole mining technique while the 800-mm diameter pipe is being inserted by the auger machine through the rubble.
Praveen Yadav, who is involved in cutting and removing the hurdles from the debris, said 51 metres have been drilled.
A worker from the Trenchless company, which is pushing the pipes with the auger machine, said if no hurdles are faced, some good news could be expected by this evening.
Rat-hole mining is a controversial and hazardous procedure in which miners in small groups go down narrow burrows to excavate small quantities of coal.
Uttarakhand government's nodal officer Neeraj Khairwal made it clear that the men brought to the site were not rat-hole miners but people who are experts in the technique.
They are likely to be divided into teams of two or three. Each team will go into the steel chute laid into the escape passage for brief periods.
Rajput Rai, a rat-hole drilling expert, said one man will do the drilling, another collects the rubble with his hands and the third places it on a trolley to be pulled out.
