NHPC knew of risks at Sikkim tunnel before deadly July blast, documents show

In the afternoon of July 20, a blast resounded through a tunnel being constructed in Sikkim’s Namchi district. Workers said that the force of the blast threw them around two metres, and that almost immediately, they could smell gas.

The explosion took place in the head-race tunnel of the 500-MW Teesta VI hydropower project being constructed by NHPC, a public enterprise. Such tunnels are the main channels that route water from a river, and lead it to turbines to generate power, before channeling the water back to the river.

The explosion occurred after a “sudden burst of suspected methane gas trapped inside the rocks which led to an explosion generating dense fumes and toxic gases”, the company said in a press release.

While some workers on site escaped the explosion, 25 others were trapped after it triggered a rockfall and blocked the tunnel’s opening. Rescue operations began immediately and concluded on the third day. There were no survivors.

The company’s press release stated that it was carrying out a “detailed investigation” to “ascertain the cause of the incident”.

But while findings of the investigation are yet to be released, company documents that Scroll has examined show that NHPC had been aware of the presence of methane on the site since at least January.

A document prepared by...

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