About 10 people were killed, and 15 remain trapped after the under-construction tunnel at Samardung Jholungey in Sikkim’s Namchi district collapsed after an explosion.
The state government issued an update saying that, as per information received from the Namchi district administration regarding the ongoing search and rescue operation at the NHPC Teesta Stage VI Hydropower Project, Samardung, “nine fatalities have been reported so far." The number is expected to rise as rescue efforts continue.
About 25 workers, including officials of the Hydropower project, were trapped inside the ADIT -3 tunnel.
The project features two tunnels spanning 13.8 km and 13.7 km.
Rescue operations have been severely hampered by the presence of carbon monoxide, low oxygen levels, poor visibility and the narrow tunnel passage, making it difficult for rescue personnel to reach the trapped workers.
According to preliminary reports, the explosion which caused the tunnel to collapse was believed to have happened after the crew reportedly made an attempt to vent the naturally forming methane gas in the tunnel. The suspected methane gas is believed to have been emanating from the underground strata or rock formations. The gas reportedly was trapped about 1.5 kilometres inside the tunnel.
The explosion caused the landslide that blocked a section of the tunnel and trapped the crew inside. It also generated dense fumes and toxic gases.
Workers heard the sound of the explosion at around 1:04 pm.
However, the gas that's currently being detected in the tunnel is carbon monoxide, NDRF Deputy Commandant Vivek Kumar said. He said that while the methane gas has not been confirmed, its presence cannot be ruled out in the mountains due to the presence of fossil fuel deposits.
The tunnel is part of the Teesta Stage VI hydroelectric project proposed in the Sirwani village.
It is based on the run-of-the-river model and was set to use flowing water from the river to generate electricity without the help of a reservoir.
The 500 MW project is expected to be operational by September 2029. The project is set to generate about 2,400 million units (MUs) of electricity annually, and is expected to contribute significantly to the energy needs of the Northeast region
