The 17-day-long operation that ended on Tuesday evening with the rescue of 41 workers trapped in the under-construction Silkyara-Barkot tunnel marked the culmination of a mission that went through its share of peaks and troughs.

Since November 12, authorities deployed a spate of plans to bore through a 57m-thick wall of debris to free the men, even as one technique after another failed to yield results. Eventually, a spirited team of “rat miners” manually drilled through the rubble and freed the trapped workers, a successful final chapter in a nerve-wracking process.

The rescue operation began on November 12, when authorities from the National Disaster Relief Force (NDRF) put into use excavator machines to scoop out the debris. Within a day, the machines had carved through 21 of the 57m of debris. But that plan met its first hurdle within a day, when a fresh cave-in wiped out a third of those gains and added seven metres more rubble to the wall.

Amid fears that the continued use of excavators could potentially cause more damage during an already precarious situation, authorities began hunting for a fresh strategy on November 14.

They turned to auger machines – corkscrew-like devices with rotary blades at the front — to drill through the stubborn wall of rock and concrete.

As the machine cut through the rock, authorities kept inserting 800-900mm-wide steel pipes that would serve as exits for the trapped workers. But this machine hit its first hurdle just two metres in, snapping against the hard stone.

Then, officials turned to a more powerful US-made auger machine that was flown in from Delhi on November 15. It reached Uttarkashi the next day and by November 17, it had cleared out 22m of debris. But this machine snagged as well, with its blades dented by the hard wall.

Still, authorities persisted with the auger machine, even as they planned contingencies: Drilling vertically in two spots to enter the tunnel from above, through a hill; drilling horizontally from the side of the hill; and digging in from the other end of the tunnel.

At this point, more agencies were drafted into the operation, including ONGC, which were adept at hydel missions.

Meanwhile, rescuers continued to push in pipes to supply the trapped workers with food, medicines, other essential supplies, telephone lines, as well as an endoscopic camera to establish video contact.The auger machine drilled away, leaving promising signs for the rescue at times, boosting hopes among officials and workers. At others, however, the machine seemed to wilt in the face of the barrier.

Eventually, the auger was wrecked on November 22, with a quick-fix helping restart on November 24, but only briefly. In the end, it got caught in the rescue pipes, threatening to damage the entire operation. The machine had drilled through 46.8m of the tunnel before it had to be discarded.

Authorities then turned to a last-resort: Sending in “rat-hole miners” with hand-held tools to manually chip away at the 12-odd metres that remained between the trapped workers and freedom.

This was the move that paid off, in the end. Within two hours of the rat miners entering the pipe (7pm on Monday), they had carved out 0.9m of the debris. On Tuesday evening, 24 hours later, the 12 miners emerged victorious, as all 41 men were pulled out on wheeled trolleys — scarred, but safe and secure.