Bengaluru tunnel road faces Lalbagh concern: GSI flags risk from Shaft-4 construction

Geological Survey of India expert panel submits study to Karnataka High Court, calls for a fresh review of the tunnel design, underground conditions and construction methods The proposed Bengaluru tunnel road project from Silk Board to Hebbal has come under fresh scrutiny after a Geological Survey of India (GSI) expert committee submitted its study report to the Karnataka High Court. The report has raised concerns about the possible impact of underground construction on the geological formation at Lalbagh. While the committee has not stated that the tunnel project will definitely damage Lalbagh, it has identified potential risks and called for additional studies and extremely careful construction. The GSI has said the existing tunnel design, geological assessment and proposed construction methods require serious reconsideration before the work progresses. Also Read: Coffee, tea prices set to rise in Bengaluru? Cup may soon cost ₹2-3 more A major concern highlighted by the expert panel is the excavation required to construct the tunnel. The use of explosives during certain stages of construction could have an impact on the ancient rock formation beneath and around Lalbagh. The rock formation already contains natural cracks. According to the concerns raised in the study, construction-related vibrations could potentially cause some of these existing cracks to widen. Such changes could affect the stability of portions of the rock. The concern is not restricted to the geological formation alone. The committee has also pointed to the possibility of an impact on historical structures located nearby, including the Kempegowda Tower. The underground rock structure can contain even small cracks, but these can become important when water movement, underground pressure and vibrations act through them. If construction activity increases these cracks, some portions of the rock could become weaker. One of the key areas identified by GSI is Shaft-4, which is located close to the Lalbagh geological monument. Also Read: 180 live Indian star tortoises seized in Bengaluru; One arrested The tunnel project requires several shafts to be created to bring the Tunnel Boring Machine (TBM) underground and facilitate its operation. Shaft-4 has been specifically identified by the GSI panel as an area requiring serious attention because of its proximity to the geological formation. The proposed construction method for the shaft could involve drill and blast work. Under this method, explosives are used to break the rock and create a deep shaft. It is this aspect that has raised particular concern. The GSI has warned that vibrations generated during the construction of Shaft-4 could affect the existing fractures inside the rock. The vibrations could potentially widen those cracks or weaken the stability of certain portions of the geological formation. Because of these concerns, the expert panel has recommended that the location of Shaft-4 be examined again by an independent technical committee. It has also suggested exploring the possibility of shifting the shaft as far away as practically possible from the geological monument. However, the GSI report does not conclude that the tunnel project will certainly cause damage to Lalbagh. Also Read: Vegetable prices surge in Bengaluru: Beans, carrot, onion and garlic turn costlier Instead, the committee has identified the possibility of geological risks and stressed that additional investigation and highly cautious construction practices are required before proceeding. The issue had already become a matter of concern for Bengaluru South MP Tejasvi Surya, who had objected to the tunnel road project over its potential impact on Lalbagh. A case was subsequently filed before the Karnataka High Court in connection with the concerns. Tejasvi Surya had sought a detailed study of the geological conditions by experts from the Geological Survey of India. Following this, the court directed that the GSI expert committee's study report be submitted before it. The latest report has now been placed before the court, bringing the geological concerns surrounding the tunnel project into sharper focus. The proposed tunnel road is planned to connect Silk Board to Hebbal, passing through a significant stretch of Bengaluru. The project is intended to provide an underground road connection across the city, but the GSI findings have highlighted the need to carefully assess its impact on sensitive geological and historical locations. The report therefore puts the focus particularly on Shaft-4 near Lalbagh, the existing fractures in the rock, possible vibrations from excavation and blasting, underground water movement and pressure, and the potential effect on nearby heritage structures. For now, the GSI's position is one of caution rather than a declaration that Lalbagh will be damaged. Its recommendation is for more detailed geological assessment, a fresh technical examination of Shaft-4 and a review of the proposed construction approach before work proceeds in the sensitive area.