The partial collapse of the Silkyara-Barkot tunnel in Uttarkashi on November 12, which resulted in the entrapment of 41 workers on the Silkyara side for 17 days before their successful rescue on Tuesday, was not an isolated event. In fact, the 4.5 km-long two-lane bidirectional tunnel, the longest on the Char Dham all-weather road project, had encountered a series of similar incidents in the past five years. Official connected with the tunnel construction said, "the tunnel had faced numerous cavity collapses due to the challenging geology of the region and significant rock deformation".