A massive landslide sliced a chunk of a hill whose debris destroyed portions of NHPC’s Teesta-V hydro project at Singtam in Sikkim on Tuesday morning.

The landslide that occurred around 7.30am was captured on video by residents of Amalay, a village situated on an opposite hill.

The 510MW run-of-the-river power project, commissioned in 2008, has an underground powerhouse with the transmission line set-up overground.

“The overground set-up has suffered extensive damage,” said a source.

The dam on the Teesta river and the allied infrastructure at Balutar in Singtam had been damaged by a glacial lake outburst flood (GLOF) on the intervening night of October 3 and 4, 2023.

The hydro project has not been functional since then and the reconstruction is on.

“Almost 80 per cent of the work in the powerhouse area had been completed,” said the source.

A.K. Dash, executive director of the project, said: “We had suffered major damage last year and reconstruction was being undertaken. We were hoping to resume (power production) by March-April (next year),” said Dash.

Tuesday’s landslide is expected to stretch the deadline.

“We are currently assessing the damage,” said Dash when asked about the loss. A technical team from Delhi will visit the site to assess the situation and recommend measures for restoring the NHPC site.

The local people, however, alleged that the underground tunnel through the hill might have triggered the landslide.

“A total of 17 houses have developed cracks. Six families have been shifted as their houses are in danger of being pulled downhill,” said a resident of Dipudara village.

Tushar Nikhare, district collector of Gangtok, visited the site along with other officials. “The families have been shifted to the NHPC guest house at Balutar which has been identified as a relief camp,” said an administrative source.

Dipudara sits atop the hill where the landslide occurred. “There is a tunnel underneath our village and this has triggered the landslide,” alleged a resident of Dipudara.

The road between Singtam and Mangam has also been damaged by the landslide at Dipudara.

The Sikkim department of mines and geology has been instructed to conduct a detailed investigation of the landslide and suggest short-term and long-term measures for the restoration.

A study condcuted by the Central Water Commission in 2015 had warned that most of the hydropower projects on the Teesta river were highly vulnerable to GLOFs.