SLBC Tunnel Project To Use Drill-And-Blast Method, Faces Environmental Hurdles Under Amrabad Tiger Reserve

The Telangana government is prepared to convert the Srisailam Left Bank Canal (SLBC) tunnel project from the Tunnel Boring Method (TBM) to the more aggressive Drill-and-Blast Method (DBM), which could have a substantial environmental impact. This decision comes as the state works to construct the remaining portion of the 19.94-kilometer-long tunnel, which runs beneath the ecologically important Amrabad Tiger Reserve.

To proceed with the new excavation strategy, the state is attempting to obtain required forest clearance from the Union Ministry of Environment, Forest, and Climate Change (MoEFCC) in compliance with the Forest (Conservation) Act of 1980. A detailed proposal is being produced by the State Forest Department. Technical teams have been entrusted with making a compelling case for using the drill-and-blast approach, which may require minimal surface-level interventions - a sensitive subject given the tunnel's placement beneath a protected wildlife reserve.

The project will also require clearance from the National Board for Wildlife (NBWL), as it involves activity beneath a critical tiger habitat. Officials said the NBWL Standing Committee will carefully review the state's wildlife mitigation plan, which must include strategies like controlled blasting to minimize the impact on wildlife and habitat.

In line with statutory requirements, the Telangana government is also committed to compensatory afforestation and payment of Net Present Value (NPV) for the diversion of forest land. However, identifying suitable non-forest land for afforestation remains a significant challenge, authorities noted.

So far, 13.93 kilometers of the tunnel have been excavated from the Srisailam reservoir side. A remaining 6.01-kilometer stretch-crucial for linking the two tunnel sections-still awaits completion. This segment includes the area where a tunnel collapse previously occurred at the 14th kilometer, exposing geological issues such as shear zones, unstable rock formations, and water seepage.

To address these challenges, a team from the National Institute of Rock Mechanics (NIRM) recently inspected the collapsed stretch, which has been marked as a 'no-go zone.' The institute is now studying the 43-meter collapse site and evaluating conditions in the remaining stretch where drilling is expected to resume shortly.