The tunnel, which traverses sensitive areas, including a tiger reserve, a wildlife sanctuary, and protected forests, was started in 2005 by JP Associates using ‘double shield’ tunnel boring machines (TBMs).
Nalgonda: After nearly two decades of delays, the 43.9-km tunnel for the Srisailam left bank canal (SLBC) project remains incomplete amid technical glitches, escalating costs and bureaucratic inertia.
The tunnel, which traverses sensitive areas, including a tiger reserve, a wildlife sanctuary, and protected forests, was started in 2005 by JP Associates using ‘double shield’ tunnel boring machines (TBMs).
This equipment was chosen as it could cut through 60 per cent of the tunnel’s route, comprising blocky, layered shale and quartzite, enabling simultaneous excavation and lining.
However, damage to the TBMs’ bearings — primarily as they navigated a complex shear zone —stalled operations for over a decade, contributing to a steep rise in the project’s cost from `2,259 crore to `4,776 crore.
The stalled works also fuelled a dispute between the earlier BRS government and JP Associates.
A SLBC engineer reported that 20.5 km of the tunnel had been excavated from one end and 14 km from the opposite side, leaving a challenging 9.5-km section plagued by significant groundwater seepage.
Efforts to revive the project gained momentum under the Congress government. In August 2024, minister Komatireddy Venkata Reddy, while on a tour of the United States, met Robbins Tunnel Boring Machine Company’s CEO Lok Home in Ohio and secured an agreement for supply of critical TBM bearings to resume drilling operations.
One bearing arrived at the Nagarkurnool site and was installed on a TBM, allowing work near Domalapenta to resume on February 18. The second bearing, which reached Chennai, is set to be transported to the outlet near Dindi in Nalgonda.
