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On the night of November 28, relief spread across India as videos circulated on social media of 41 construction workers emerging from Uttarakhand’s Silkyara-Barkot tunnel. The workers had been trapped for 16 days after part of the tunnel collapsed. The videos showed the workers being wheeled out through a pipe that had been inserted through the rubble. As one worker left the tunnel, he almost leapt in joy, raising his hands in the air and laughing.

Around 1,200 kilometres away, watching the videos on my laptop, I felt a surge of joy too. But that feeling subsided quickly and the emotions that had lurked for most of the preceding two weeks returned – frustration and dismay at what had led to this disaster.

It has long been known that the Himalayan geography is unsuitable for large infrastructure projects like hydropower dams and tunnels. That makes it increasingly troubling each time such projects result in disasters, or near-disasters as in Silkyara. This year alone, Scroll has reported on and followed several such events – including Sikkim’s glacial lake outburst flood, which damaged three hydroelectric dams, Joshimath’s subsiding lands and several landslides in Solan triggered by the widening of roads to four lanes.

To learn more about the Silkyara tunnel project, I accessed a pre-feasibility report prepared by a geological consultant for the highway project of which the tunnel is a part. The report sought to analyse the geology and rock types of the region where the tunnel was to be built. Excerpts of this report were also included in the 2018 detailed project report prepared by Technocrats Advisory Services and submitted to the Ministry of Road Transport and Highways. The report noted that there were “huge successions” of “fine grained sandstone-siltstone-slates-shales” and a 40-metre-wide “shear zone” in the project area.

To navigate these technical terms, I sought help from Yaspal Sundriyal, professor at the Hemwati Nandan Bahuguna Garhwal University.

Sundriyal explained that a shear zone within a mountain refers to a portion made up of a mass of crushed rock. Such zones are commonly found in the Himalayan range, and the thicker a shear zone, the higher the chances that that section of the mountain will be unstable. “A 40-metre-wide shear zone is a lot!” Sundriyal said.

Another geology report, prepared by Navyuga Engineering Company, which is constructing the tunnel, stated that the tunnel’s site “coincides with a major tectonic boundary known as the main central thrust”. This thrust is a geological fault line that runs through the Himalayas and is tectonically active, making construction near it risky.

Given that such information was available, “at least we should have an estimate of the minimum damage that can happen and prepare for it accordingly”, Sundriyal added. Indeed, the detailed project report itself noted this. It stated that risks should be “minimised by proper investigations” and that the tunnel’s design should be based on the results of these investigations.

But once a portion of the tunnel collapsed, it quickly became clear that the company was ill-prepared to drill through to reach the trapped workers. The work needed auger machines, which can bore horizontally through a mountain without significantly disturbing the surrounding mass. These were airlifted from Delhi, but broke within two days; then, replacements had to be flown in from Indore. On November 25, a member of the National Disaster Management Authority informed the media that those had broken too and that broken parts had to be extracted from the debris. Only then could the next phase of the rescue – manual digging – commence.

Geologists I spoke to repeatedly noted that the greatest lapse was the absence of an escape passage. According to the detailed project report, “tunnel guidelines” mandate that any tunnel longer than 1.5 km “must have an escape passage for emergency conditions”. Such a passage is essentially a smaller tunnel parallel to the main one, which can be accessed at regular intervals and can be used as an emergency escape route, as well as for tunnel maintenance. These are mandated globally. Under both European and United States standards, tunnels must have such passages every 300 metres.

The Silkyara-Barkot tunnel did not have such a passage – though the company’s own documents suggest that it had been part of the project’s plan. When the National Highway and Infrastructure Development Corporation called for proposals for the construction, it invited tenders specifically for “construction operation and maintenance of the tunnel with escape passage”.

Even the detailed project report referred to such a passage, recommending that the most “cost effective” proposal would be a single tunnel with an escape passage of 3.5 metres by 4.5 metres.

In fact, the detailed project report lays out three possible plans for construction, and rules out one that would have been the least expensive and quickest to construct because it did not have an escape tunnel, and would therefore be against “tunnel guidelines”.

“Such smaller tunnels have to be constructed as and when those parts of the tunnel are constructed,” a former NHIDCL civil engineer told me, requesting anonymity. Yet, a panel member who investigated the collapse said that the tunnel did not have any such escape passages.

A report in The Times of India noted, “After detailed discussion during the pre-bid meeting for the project, it was recorded that the egress tunnel was not required, sources said.” Officials told the newspaper that in this instance, “there was no need for such provision as the single tube is divided into two interconnected corridors by a partition wall”.

The 41 workers were brought to safety after a multi-agency operation that is being described as the “most significant rescue operations in recent years”. Afterwards, their families were busy with celebrations. When I phoned the brother of Subodh Kumar, one of the workers, I could hear sounds of people chatting excitedly and songs in the background – he told me that a havan was underway. “We are eagerly waiting for him to return,” he said.

The workers are coming home, and the cameras and journalists have left the tunnel, as have the rescuers, and visiting politicians.

For now, a “safety audit” of the tunnel will be conducted, and construction will soon resume. Varun Adhikari, an engineering geologist involved in the rescue operations, told me that “till the investigation is completed” he could not comment on why no escape tunnel had been built and whether there were any plans to build one now. For now, it remains unclear what will change on the ground.