What caused the under-construction metro pier in Bengaluru to fall?

It remains a mystery as to why the reinforcement cage of the under-construction metro pier swayed, buckled and eventually gave away, killing a woman and her toddler son in HBR Layout on Tuesday morning.

Was it the cage’s enormous weight? Or was its height?

Authoritative sources in the Bangalore Metro Rail Corporation Limited (BMRCL) said the weight and height make the cage unwieldy but not unmanageable. “We have erected heavier and taller cages than this,” a source said.

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The cage in question, a circular column made of TMT bars, weighed 30-40 tonnes and was 16.5 metres tall. “Given the size, it needs support, which is provided by scaffolding and then by guy-wires (metal ropes),” the source said.

When the cage gave way, at least six labourers were working on top of it to remove the scaffolding and tie the guy-wires. “Everything was fine until then. Our engineers had inspected the site just an hour earlier, found everything was in order and moved to the next location,” the source told DH.

As the labourers were removing the scaffolding, the cage encountered an imbalance and one of the guy-wires gave away. “We don’t know how,” the source explained. The labourers jumped down to save themselves.

While the incident has sparked questions about safety at metro sites, the source insisted that the BMRCL “rigorously” follows the method statement, a document that details how every work should be carried out.

“Every stage of the work is checked, first by the contractor’s safety engineers and then by our engineers and an independent agency,” the source explained. “Every activity is carried out only after the approval comes.”

The BMRCL has formed an internal inquiry committee consisting of chief engineers from the safety, quality and work departments. The report is expected in three days. Separately, it will ask the civil engineering department of the Indian Institute of Science (IISc) to do an independent investigation.

While BMRCL boss Anjum Parwez said that the contractor (NCC Ltd) would be issued a notice, a source said the company might get away with meagre fines.

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As per the contract, the company can be fined Rs 5 lakh per fatal incident and Rs 10 lakh for the second incident.

Large companies usually subcontract the work. A spokesperson for NCC Ltd promised to connect DH to the top brass but didn’t respond later.

Metro goes incommunicado

Namma Metro took more than seven hours to issue a statement on the tragedy, drawing further criticism. It promised to pay Rs 20 lakh to the victims’ family and bear their medical expenses. “BMRCL is deeply saddened by the unfortunate incident and stands with the distressed family,” the statement said.

Shadow on airport line

The tragedy occurred on the 38.44-km KR Puram-Airport metro line under Phase 2B, which is being constructed by the Hyderabad-based Nagarjuna Constructions Company (NCC) Ltd in three packages: Benniganahalli (KR Puram)-Kempapura, Kempapura-Yelahanka Air Force Station, and IAF Station to Airport. The cost is Rs 9,583.54 crore.

Chief Minister Basavaraj Bommai last month announced the airport line would be ready by “December 2023” but metro officials say that deadline is impossible. The accident is likely to cause further delay.

The BMRCL has so far erected just 30% of the over 1,000 piers necessary for the airport line. The viaducts are currently being cast in the yard. Work on stations will start afterwards.

Phase 2B will connect to the 19.75-km Phase 2A, which runs from KR Puram to Silk Board.