Expert Panel Expresses Concerns Over Bengaluru Tunnel's Project Report

An expert committee comprising senior engineers and specialists has raised serious objections to the Detailed Project Report (DPR) for the proposed Hebbal-Silk Board underground tunnel, calling it incomplete, unrealistic, and undercosted.

The report was submitted to the Karnataka government in May, warning it of significant design, environmental, and financial shortcomings.

The DPR was prepared by Rodic Consultants Pvt. Ltd., following feasibility studies by Altinok Consulting Engineering Inc. and Lion Engineering Consultants Pvt. Ltd. It was accessed by environmentalist Dattatreya Devar through an RTI.

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The 18.5-kilometer-long tunnel, proposed by the Greater Bengaluru Authority (GBA) to ease north-south traffic congestion, is planned to run parallel to the metro corridor, connecting Hebbal, Mekhri Circle, Race Course, Lalbagh, and Silk Board.

Key Findings Of The Panel

Environmental concern: A proposed tunnel shaft falls inside Lalbagh Botanical Garden, a protected green zone.

Alignment issue: The tunnel's route runs almost parallel to the metro line, raising duplication and viability concerns.

Traffic design flaw: Entry and exit ramps near key junctions could intensify congestion instead of reducing it.

Drainage and flood risk: The stormwater drainage plan is incomplete, and the diversion of Hebbal nallah was termed "unrealistic."

Geological uncertainty: Only four of 27 planned boreholes were tested; the panel recommends Electrical Resistivity Tomography (ERT) to detect underground aquifers and ensure stability.

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Overdesigned and undercosted: DPR proposes 3+3 lanes, though projections justify 2+2 lanes. Crucial costs like grouting, muck disposal, and O&M were left out, while a 306 crore TBM provision lacks justification. The panel advised a 10-15% cost increase to account for these omissions.

Safety gaps: The report lacks adequate detailing for fire safety, ventilation, and cross-passage design, which are critical for a long underground structure.

DPR Remains Deficient In Geological, Cost Aspects...

While the GBA accepted most consultant explanations, the expert panel concluded that the DPR remains deficient in key technical, geological, and cost aspects.

The panel recommended a thorough revision, including updated surveys and financial estimates, before proceeding.