SLBC tunnel work to resume with new alignment, bypassing collapse site

The SLBC tunnel project in Telangana remains stalled past the July-end deadline, months after a deadly roof collapse. Authorities plan to bypass the fault zone, but delays continue amid geological challenges, safety concerns, and political criticism of the Congress government.

Hyderabad: The Srisailam Left Bank Canal (SLBC) tunnel project, a critical irrigation initiative in Telangana, remains stalled even by July end, the deadline set to resume work.

Following the tragic roof collapse on February 22, which claimed two lives and left six workers missing, uncertainty loomed over the fate of the project. The incident, occurring in a fault zone between chainage 13.88 and 13.9 km, has forced a major overhaul of the project’s execution.

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Authorities have decided to permanently abandon the vulnerable fault zone, where a three-meter roof cave-in exposed weak rock integrity previously flagged by a seismic wave report.

Work to resume 100 metres ahead of accident site
To circumvent the unstable geology, the Irrigation Department has planned to resume tunnel excavation 100 metres ahead of the roof collapse site. This new alignment avoids the need for fresh environmental clearances, as it poses no ecological impact, officials claimed.

The tunnel boring machine (TBM), severely damaged in the accident, will be entombed within the tunnel, with some parts deemed irretrievable as in the case of the bodies of the six missing workers. Moving forward, conventional excavation methods will replace the TBM due to the challenging Nallamala Hills geology, comprising 60% quartzite and 40% granite.

The project’s contractor, Jaiprakash Associates, has drawn flak for ignoring seismic warnings about the absence of solid rock in the fault zone. A senior irrigation official, speaking anonymously, noted that while government pressure to expedite work is common, the contractor’s oversight contributed to the disaster.

Expert consultations with the National Geophysical Research Institute (NGRI) and Geological Survey of India (GSI) are underway to mitigate further risks. An aerial LIDAR survey is also planned to ensure precision in the revised approach. The government’s effort is to complete the 44-km tunnel, with 35 km already excavated, by December 2026.

However, despite plans to resume work by July end, progress remains halted, raising doubts about meeting the deadline.

The SLBC, conceived in 1983 to channel Krishna River water from the Srisailam Reservoir to drought-prone areas, has faced decades of delays due to geological, financial, and technical challenges. Opposition parties have accused the Congress-led government of mismanagement, intensifying political tensions.

• Vulnerable fault zone will be permanently closed
• Excavation work will resume 100 metres ahead of roof collapse
• Damaged TBM to be abandoned and entombed within tunnel
• Conventional methods to be used to address challenging geology
• NGRI, GSI guiding revised plan to be supported by aerial LIDAR survey