DPWH says severe overloading proximate cause of Isabela bridge collapse

The third span of the 990-meter Cabagan-Santa Maria Bridge in Cabagan, Isabela, came crashing down along with a dump truck. Four other vehicles which also crossed the newly completed bridge at that time were damaged, injuring six people. Photo by Villamor Visaya Jr.

MANILA, Philippines — While the unique design of the Cabagan-Sta Maria Bridge might have contributed to its collapse, the Department of Public Works and Highways (DPWH) insisted that severe overloading is the cause of the bridge’s fall.

READ: Isabela bridge collapse a question of measurement or accountability

Speaking at the Senate sub-panel on blue ribbon’s hearing held Wednesday, Public Works and Highways Secretary Manuel Bonoan presented the findings of his agency’s special committee tasked to probe the incident that led to the collapse of the Isabela bridge.

“From the submitted documentation, the DPWH’s special investigation committee submits that the Cabagan – Sta. Maria bridge is the first of its kind — both locally and internationally due to its non-typical arch support scheme which involved a suspended deck system,” said Bonoan.

“Unfortunately, there was no document submitted to the special investigation committee that exhibit how the bridge designer arrived at his design of an arch-truss bridge. This unique design might have caused complications and contributed to the collapse of the bridge,” he added.

According to Bonoan, the bridge’s design is unique, so it would need “accurate detailing of connections, anchorages, elaborate construction methodology and provision of redundant members to reduce the risk of collapse of the suspended deck system.”

`Segmental construction’

“To further complicate the matter, the programs of work for the bridge provided for the construction of the complete span, whereas the invitation of the bid only directed segmental construction,” he said.

While the design may have contributed to the bridge’s fall, DPWH said it submits that severe overloading is the proximate cause of the collapse.

“While it has been established that the proximate cause of the collapse of the bridge is the passage of overloaded trucks — however, in principle the bridge may have experienced failure in structural members, but the collapse should not have occurred,” said Bonoan.

The DPWH chief said they were informed that on February 26, trucks loaded with cargo traversed the bridge.

“The following day, the very same trucks again traversed the bridge. When it collapsed, we have a certain gross vehicle weight of the truck to be at 89.63 metric tons which is well beyond the maximum allowable gross vehicle weight of 45 tons pursuant to Republic Act 8794 — thus, the overloading of trucks and repeated passage induced fatigue in the bridge and may have caused the collapse,” he added.

On February 27, the Cabagan-Sta Maria Bridge collapsed when a dump truck carrying quarried stones exceeding the 45-ton weight limit attempted to cross.

At least six people were injured and four vehicles were damaged in the incident.

The bridge had been completed just weeks earlier on February 1, 2025 at a cost of P1.22 billion.