Will Digging Tunnel Road Spell Environmental Disaster for B'luru?

Using bentonite with tunnel boring machines may lead to waterlogging, groundwater contamination, warn experts

- RISHITA KHANNA @ Bengaluru

WILL the proposed Tunnel Road between Hebbal and Silk Board Junction spell an environmental catastrophe for Bengaluru?

Experts warn so, especially if the road would be dug using Slurry Tunnel Boring Machines (TBMs).

Now the state government sources have confirmed the plan to deploy TBMs. The TBM method will flood excavation sites with bentonite slurry, a type of clay primarily known for its exceptional water absorption and swelling properties, forming a gel-like substance when hydrated.

In Bengaluru's hydrology, this dense clay can seep into aquifers, choke stormwater drains, and coat lake beds with an impermeable layer, blocking natural groundwater recharge. Urban planners warn that once bentonite contamination occurs, the damage is nearly irreversible and will lead to locking the city into decades of waterlogging and water scarcity.