An internal report prepared by the subcontractor working on the Wayanad tunnel project had warned that a slope at the North Portal could collapse at any time, weeks before a landslide killed six people at the site on Tuesday. The geological and geotechnical assessment found that the hillside above the proposed tunnel entrance was already showing serious signs of instability.

The report was prepared by Dilip Buildcon Limited and signed by its senior geologist Raju Sagar, Geological Survey of India official A Ramesh Kumar and Authority Engineer Dr H K Singh of Turkish Engineering Consulting and Contracting. Engineers who inspected the site between June 3 and June 11 found a layer of loose, silty soil around 35 metres deep on the left side of the portal, sitting above harder rock and vulnerable to heavy rainfall.

According to the report, the slope was already showing signs of failure during the inspection. Engineers observed widening cracks across several levels, earth slumping along the cut benches, muddy water seeping from the slope and cavities developing inside the soil. They also reported hearing underground water flowing between support levels, indicating that internal erosion could be weakening the hillside from within and potentially triggering a sudden collapse.

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The report identified the left-hand slope as significantly more dangerous than the right and warned that continued rainfall could lead to sudden slope failure at any time. Drainage holes installed to reduce water pressure were reportedly not functioning properly in several areas, while early-warning instruments such as piezometers had not been installed. The monitoring system in use was also found to be failing to accurately reflect the visible distress on the ground.

Engineers recommended several urgent safety measures, including the construction of gabion retaining walls, protective covering for exposed soil, tarpaulin sheets running from the top to the bottom of the slope and lined drainage channels to divert rainwater. The report also called for testing soil nails and drainage systems under saturated conditions and recommended relocating a nearby concrete-mixing plant whose weight and vehicle movement were considered additional risks to the slope.

Officials linked to the project said work at the North Portal was stopped after the report and maintained that heavy rainfall, rather than trial blasting conducted on June 5, 6 and 11, was the main cause of the instability. The contractor said work would not resume until a government-appointed expert committee is satisfied with safety measures. The report was prepared before the District Collector’s June 20 stop-work order, raising further questions about whether the recommended protections were implemented before the fatal landslide.

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