Water blight: On the Srisailam tunnel cave-in.
Scientific risk assessment prior to undertaking tunnel work is a must.
Barely a week after the remains of nine coal miners were recovered at the end of a 44-day operation, from a coal mine that had flooded in Assam in early January, a disaster of similar contours, this time in Nagarkurnool, Telangana, is in the making. A portion of the Srisailam Left Bank Canal tunnel, which is under construction, collapsed on February 22, 2025 leaving eight workers trapped. What is known so far is that a three-metre section of the roof collapsed due to water seepage. The roof collapse eventually led to the tunnel crumbling over a stretch of eight metres. Despite nine specialised rescue teams, drawn from the Centre and the State governments, working round-the-clock, no significant progress has been made so far on ascertaining the condition of the workers and in devising an optimal rescue plan. So far, the playbook that is being experimented with seems to be inspired by the successful rescue work in the Silkyara Tunnel collapse in Uttarkashi, Uttarakhand, in November 2023, where a portion of the four -kilometre-long tunnel that was being constructed collapsed, stranding 41 workers. It took a 16-day operation that started out with a variety of approaches, including drilling horizontally, and later on vertically, from both ends of the tunnel to reach the stranded workers. In the end, key breakthroughs were achieved by a team of ‘rat hole’ miners from Assam, who use manual excavation methods that are considered hazardous and deemed illegal.
The key difference between the Silkyara episode and the one in Srisailam is the presence of water. There were 70 workers in the tunnel when a deluge of water and muck suddenly began to gush inside. Barring the eight, the rest escaped, with 13 of them sustaining injuries. However, in the subsequent days, it is the torrential flow that has proved to be a barrier to rescue operations. The history of tunnel-linked disasters globally shows that while rare, they can often be catastrophic. A large proportion of these accidents, studies show, are due to a rupture in aquifers (underground water channels). It is to determine such risks that extensive studies are commissioned to understand the sub-surface geology of a site. A report by the Uttarakhand disaster management authority on the Silkyara episode says that there was insufficient analysis of the rock formations at Silkyara but also that a complete picture of structural deformities cannot be known before tunnelling. While the rescue of the trapped personnel at the Srisailam tunnel is paramount, there has to be a proper investigation by the authorities on the reasons for the collapse and action taken, if evidence emerges of tardy pre-tunnelling analysis.