Buried questions, Pg8

Key Highlights:

• At least 15 workers died and several others were trapped after a suspected methane burst in an under-construction tunnel of the Teesta Stage-VI hydroelectric project in Sikkim’s Namchi district.
• The incident occurred at a project site managed by NHPC Limited, a public-sector undertaking.
• NHPC Limited has initiated a detailed investigation into the incident.
• The Teesta Stage-VI hydroelectric project is a 500 MW run-of-river scheme located in Sirwani village, Sikkim.

Tunnel Blast.jpg

Detailed Insights:

• The accident highlights the inherent dangers of underground excavation in the Himalayan belt, a seismically active zone with young and heavily fractured rock prone to compressed gas pockets.
• The Teesta Stage-VI project was acquired by NHPC Limited in 2019 after its original private developer, Lanco Teesta Hydro Power Ltd (LTHPL), faced insolvency.
• This tragedy follows other recent incidents, including an explosion at an illegal coal mine in Meghalaya and a tunnel collapse in Uttarakhand in 2023 that trapped 41 workers.
• The region's vulnerability was tragically demonstrated in October 2023, when a Glacial Lake Outburst Flood (GLOF) from the South Lhonak lake destroyed the Teesta-III dam and caused over 100 fatalities downstream.
• The incident underscores the critical need for stringent safety protocols, proper risk assessment, and functional gas-detection and ventilation systems in such projects.
• There is a call for a thorough, independent review to ascertain whether conditions attached to the project’s environmental clearance were strictly met.

Key Concepts Involved:

• Methane: A colorless, odorless, flammable gas, often found trapped in geological formations, posing an explosion hazard in underground excavations.
• Seismically Active Zone: Regions prone to frequent earthquakes due to tectonic plate movements, leading to fractured and unstable geological structures.
• Glacial Lake Outburst Flood (GLOF): A sudden release of water from a glacial lake, often caused by the collapse of natural dams, leading to catastrophic downstream flooding.
• Environmental Clearance: A mandatory regulatory approval required for development projects to assess and mitigate their potential environmental impacts.
• Run-of-River (RoR) Scheme: A type of hydroelectric project that harnesses the natural flow of a river without requiring a large reservoir, minimizing environmental impact but often having fluctuating power output.