Isabela Bridge engineer calls for forensic probe, denies design flaw

The structural engineer behind the collapsed Cabagan-Santa Maria Bridge in Isabela has refuted allegations that a design flaw was to blame for the incident, emphasizing that the structure was built in compliance with the Bridge Code of the Philippines.

In an interview with DZRH, Engineer Alberto Cariloria Cañete, the bridge's original designer and author of the 1997 and 2015 Bridge Code of the Philippines, defended the integrity of his design, stating that the collapse was primarily caused by overloading and not a faulty blueprint.

Cañete revealed that he designed the 990-meter bridge in 2012 and 2013, incorporating an efficient arch geometry that has long been proven effective since Roman times. 

“I used an efficient arch geometry in the design because arches have long been proven to be strong since Roman times,” Cañete explained in Filipino. “The arch is what supports the bridge, and that’s what makes my design economical.”

The engineer emphasized that if there was truly a design flaw, the collapse should have occurred on the first arch, not the tenth. He pointed out that the dump truck, which weighed 102 tons including its load, managed to cross nine arches before the structure collapsed on the tenth arch.

The construction of the bridge began in November 2014 and was completed on 1 February 2025, costing a total of P1.225 billion. Cañete clarified that the bridge was originally designed under the 1997 Bridge Code, but by 2015, new standards were introduced, increasing force requirements for bridges. To comply, the first eight arches of the bridge were retrofitted to meet the 2015 standards.

He stressed that his role was limited to designing the bridge and that he had no involvement in the construction or materials used, as per Department of Public Works and Highways (DPWH) policy.

Calls for forensic investigation

Responding to President Ferdinand Marcos Jr.’s earlier statement attributing the collapse to a design flaw, Cañete refused to engage in any blame game. Instead, he urged authorities to conduct a forensic engineering investigation to determine the real cause of the collapse.

“This is similar to when an airplane crashes. You don’t immediately conclude the cause until you retrieve the black box and conduct a thorough investigation,” Cañete explained. “The same should apply here. We need to analyze the design and inspect the construction through forensic engineering.”

The engineer also expressed his willingness to cooperate with the investigation to clear his name, as his reputation was being dragged into the controversy despite the absence of official findings.

“It’s important that we be careful about what we conclude. There should be a forensic engineering investigation to analyze the design and construction before releasing a final report,” he said.

As investigations continue, overloading remains the primary cause identified for the bridge collapse. The DPWH-Cagayan Valley earlier confirmed that the dump truck carrying 102 tons significantly exceeded the bridge's load capacity, triggering the collapse.