The death toll in a methane explosion inside the tunnel under construction for the Teesta Phase VI Hydel project in Sikkim, south Bengal, rose to 13 on Wednesday after another body was recovered, while 12 workers remained missing, officials said.
Rescue teams battled toxic gases, mud and poor visibility to search for survivors. “The conditions are very bad inside. It is very dark and hot inside. The tunnel is full of toxic gases like methane and carbon monoxide. The floor of the tunnel is full of mud and our legs often got stuck,” said a member of the rescue team of Coal India Ltd.
A total of 25 workers working inside the Adit-3 of the 15-km-long tunnel in Namche district, which connects the barrage at Siwarni to the power station at Tarkhola in south Sikkim, were trapped on Monday. An official at the National Hydroelectric Power Company (NHPC), who requested to remain anonymous, said, “The explosion was caused by a possible leak of methane gas. The methane gas was likely trapped in a pocket in the rock that was being excavated by a tunnel boring machine. When the machine collided with that pocket, the gas leaked out and caused the explosion.”
Namchi Superintendent of Police Sonam Bhutia said: “We recovered one more body on Wednesday which took the death toll to 13. At least 12 people are still missing. Rescue teams from the National Disaster Response Force (NDRF) and Coal India Limited are still working at the site.”
Members of the Coal India Limited (CIL) rescue team claimed to have spotted at least eight more bodies inside the tunnel on Tuesday. The bodies have not yet been recovered. The Namche district administration was unable to verify the allegations as of Wednesday evening.
“Our gas detectors are equipped to detect and measure the levels of four gases – hydrogen sulphide, oxygen, methane and carbon monoxide. During the rescue operations, we detected high doses of methane and carbon monoxide. Normally, the site is evacuated if the lower explosive limit of these gases reaches 20%. But the levels of carbon monoxide and methane are much higher in the tunnel, making work difficult,” said an official working at the site.
Rescuers have to enter the tunnel wearing self-contained breathing apparatus, which helps maintain a constant supply of oxygen during long-range rescue operations. Each device weighs approximately 15 kg.
Another official said: “During tunneling, a lot of mud, silt and water comes out. It is pumped out. But since the explosion damaged equipment and pipelines, it was not possible to pump out the mud and water, and thus the ground became muddy and water accumulated in pockets, which hampered rescue operations.”
People familiar with developments at the accident site said that search and rescue operations were suspended for some time due to the accumulation of water and mud at the site. But it resumed after a few hours.
The rescuers who entered the scene said that it was very difficult to walk because their legs were stuck in the mud, and every time they had to rely on something to pull their legs out, making the rescue operations more difficult and difficult.
“We have deployed earth bulldozers,” an official said. “Our engineers are repairing damaged pipes so that water and mud can be pumped out and rescuers can enter. Rescuers wear 15-kg masks and respirators equipped with oxygen cylinders to go inside the dark tunnel and search for survivors and bodies.”
