PIE viaduct collapse: Engineer did not check support structures

Key structural elements of a viaduct being built in Changi were so inadequate that a collapse would have been inevitable.

And even though his failure to check these elements did not lead to it, engineer Leong Sow Hon's oversight could have caused unimaginable casualties, Deputy Public Prosecutor Yang Ziliang told the court yesterday.

A section of the viaduct linking the Tampines Expressway and Pan-Island Expressway collapsed in the early hours of July 14, 2017, killing Chinese worker Chen Yinchuan, 31, and injuring 10 others.

Temporary structures outside of Leong's purview had given way, causing the collapse.

But DPP Yang said Leong, who was the accredited checker for the project, did not evaluate, analyse or review the structural design and failed to perform original calculations for the viaduct's permanent corbels, essential for support and overall structural stability.

If the 1.8km-long viaduct was constructed as originally designed, eight out of the 10 corbels would have failed.

Yesterday, Leong, 61, pleaded guilty to an offence under the Building Control Act.

He admitted to failing to check the detailed structural plans and design calculations of the viaduct building works in accordance with regulations. Another charge of falsely certifying he had carried out the checks was taken into consideration.

Permanent corbels are reinforced concrete structures that allow load on the viaduct's eight flyovers to be transferred to supporting columns.

DPP Yang said five were unable to support the weight they were designed for and would have collapsed during construction.

Three others would have had significant structural cracks with a full traffic load, leading to sudden brittle failure and subsequent collapse.

Said the DPP: "If the viaduct collapsed after it had been constructed and opened to traffic, the casualties caused would be unimaginable."

Calling for a nine-month jail term, he said Leong's breach of statutory duty was serious and could have resulted in "high potential harm".

Appointed by the Land Transport Authority, Leong was personally responsible for double checking plans and calculations but was "derelict in his non-delegable duties", said DPP Yang.

Leong initially claimed he had done the independent calculations and found the permanent corbels to be adequate but could not provide evidence.

He admitted to his deceit only after his engineers confessed.

FINE

Leong's lawyer Tai Chean Ming sought a $25,000 fine.

He said no actual harm had been done, emphasising the 2017 collapse had nothing to do with the permanent corbels.

Mr Tai said Leong was responsible for more than 280 elements along the viaduct, and apart from the corbels, had checked the remainder.

None of the cases involving accredited checkers in the last two or three decades led to prison terms, Mr Tai added, arguing jail would not have an additional deterrent effect.

Leong is expected to be sentenced on July 5 and faces up to two years' jail or a fine of up to $100,000.

The managing director of Calibre Consulting Singapore is the first person involved in the collapse to plead guilty.

Cases involving the main contractor, Or Kim Peow Contractors, and four other men allegedly linked to the incident are still pending.

The men are: the qualified person from subcontractor CPG Consultants, Robert Arianto Tjandra, 46; and from Or Kim Peow Contractors, project engineer Wong Kiew Hai, 31, project director Allen Yee, 49, and group managing director Or Toh Wat, 51.