By Shishir Prashant 
PrashantNews
From NTPC’s 520 Mw Tapovan Vishnugaad project in Uttarakhand to NHPC’s Teesta Stage VI dam in Sikkim, the tunnelling projects remain challenge owing to unpredictable behaviour of the ground strata particularly in the highly fragile zones of the Himalayas.
The latest Sikkim Tunnel tragedy has only highlighted the risks faced by workers engaged in various tunnel constructions in difficult mountain terrains.
The rescue operation at the under-construction Head Race Tunnel (HRT) of NHPC’s Teesta Stage-VI Hydroelectric Project in Sikkim was concluded on Thursday with the recovery of bodies of all the 25 personnel trapped inside the tunnel.
“An unfortunate incident occurred on July 20, 2026, inside the under-construction Head Race Tunnel (HRT) of Teesta Stage-VI Project after sudden burst of suspected methane gas trapped/embedded inside the rocks which led to explosion generating dense fumes and toxic gases.,” NHPC said in a statement.
The rescue operation was carried out with the coordinated support of the District Administration, National Disaster Response Force (NDRF), State Disaster Response Force (SDRF), Ministry of Power, Ministry of Home Affairs, Ministry of Defence, Government of Sikkim, Government of West Bengal, NHPC, Coal India Limited, Patel Engineering Limited, Eastern Coalfields Limited, Western Coalfields Limited, local authorities and several other agencies.
The Sikkim disaster comes less than three years after the Silkyara tunnel accident in Uttarakhand, where 41 workers remained trapped for 17 days before being rescued in a massive multi-agency operation. Before the Silkyara tunnel mishap, dozens of workers were killed inside the underground tunnel of NTPC’s 520 Mw Tapovan Vishnugad project following the Rishikganga deluge in 2021.
The three incidents have intensified concerns over the growing number of tunnel projects being undertaken across the Himalayan states to improve road connectivity and strategic infrastructure.
Experts have repeatedly warned that the Himalayan region is geologically young and highly fragile, requiring rigorous safety assessments, scientific planning and strict adherence to engineering standards before and during construction. The latest tragedy is expected to renew calls for comprehensive safety audits and stronger oversight of ongoing and future tunnel projects.
Reacting to the incident, social activist Anoop Nautiyal expressed deep concern over the recurring tunnel accidents in the Himalayas. In a statement, he said, “In the din of Delhi, we have lost sight of the 25 people who died in an under-construction tunnel in Sikkim. As I feel the pain of the bereaved families and offer my deepest condolences, I ask about the future of tunnels in the Himalayan states of our country.”
Referring to the 2023 Silkyara tunnel accident in Uttarakhand, Nautiyal said that while tunnels improve connectivity, “they cannot come at this human cost.” He noted that beyond announcing ex gratia compensation, there appears to have been little discussion on accountability or course correction. Stressing that many more tunnels are planned across the Indian Himalayan Region, he said there should be “no shortcuts with security and safety”, calling for stronger safeguards to prevent such tragedies from recurring.
Before any construction work takes place, risk assessment should be undertaken after identification of likely hazards and for each risk occurrence an estimate of the possible resulting consequences should be determined. Based on that assessment appropriate risk mitigation and control measures should be taken to control or minimise the risks. On-going risk assessment will be needed during the construction phase, particularly if design changes are made or unforeseen ground conditions encountered, said a top engineer of the Indian railways which is constructing the Rishikesh-Karanprayag rail project which is mostly underground. The 125.20-km long project includes 17 tunnels.