Permanent structures used in the construction of a Pan-Island Expressway (PIE) viaduct near Upper Changi were so inadequate that they could have collapsed under the weight of a full traffic load and caused an unimaginable number of casualties.
Deputy Public Prosecutor Yang Ziliang told the court yesterday that 61-year-old engineer Leong Sow Hon, who was appointed by the Land Transport Authority as an accredited checker, had failed to go through the detailed plans and design calculations for permanent corbels, or support structures.
Permanent corbels are reinforced concrete structures that are critical in the stability of a viaduct. They allow the load on a flyover to be transferred to the columns.
Leong's deceit could have resulted in "high potential harm", said DPP Yang. "Investigations have revealed that the permanent corbels were inadequately designed... out of the 10 permanent corbels, eight of them were inadequately designed for the total load, including traffic, upon completion of the viaduct."
Of the eight, five of the corbels were unable to support the weight they were supposed to be designed for. The remaining three, said DPP Yang, would have shown significant cracks with a full traffic load, leading to a collapse.
"If the viaduct collapsed after it had been constructed and opened to traffic, the casualties caused would be unimaginable," the DPP added.
Leong, the managing director of Calibre Consulting Singapore, pleaded guilty yesterday to failing to check the detailed structural plans and design calculations of the viaduct building works in accordance with regulations under the Building Control Act.
One count of falsely certifying that he had carried out the required checks will be taken into consideration during sentencing. Leong is so far the only person involved in the case to plead guilty.
His actions were discovered only after temporary structures at the incomplete viaduct gave way on July 14, 2017. The collapse resulted in the death of 31-year-old Chinese worker Chen Yinchuan. Ten other workers were injured in the incident.
As the final checker, Leong's job was to go through the detailed plans and design calculations for the permanent corbels. But he admitted to not evaluating, analysing or reviewing the structural design in the plans and failing to perform original calculations for all permanent corbels.
Although he initially claimed he had performed the original calculations for the corbels and found them to be adequate, Leong was unable to provide evidence.
In fact, no calculations were performed for both permanent and temporary corbels during the submissions stage of building works.
The cases involving the main contractor, Or Kim Peow Contractors, and four other men allegedly linked to the incident are still pending.
They are the qualified person from subcontractor CPG Consultants, Robert Arianto Tjandra, 46; project engineer Wong Kiew Hai, 31; and project director Allen Yee, 49 - both from Or Kim Peow Contractors - as well as its group managing director Or Toh Wat, 51.
Yesterday, DPP Yang urged District Judge Hamidah Ibrahim to sentence Leong to at least nine months in jail. He added: "The seriousness of the harm risked, the likelihood of that harm arising and the number of people likely to be exposed to the risk of that harm are all high."
Those convicted of the offence under the Act can be jailed for up to two years and fined up to $100,000.
Defence lawyer Lim Lian Kee pleaded for his client to be fined $25,000, adding that a jail sentence was not justified. Mr Lim also told the judge that the collapse in 2017 was caused by the temporary corbels, not the permanent ones.
Or Kim Peow Contractors has been replaced by Hwa Seng Builder, which clinched the deal to complete the stalled project for $95.6 million last year. The viaduct was supposed to be completed by the first quarter of next year, but is now expected to be ready by the first half of 2022.
Leong's case has been adjourned to July 5.