SINGAPORE - A construction firm and two senior employees have been convicted over the 2017 Pan-Island Expressway viaduct collapse that left one worker dead and ten injured.

Or Kim Peow (OKP) Contractors was found guilty on Friday (Jan 22) of failing to take reasonable measures to ensure their safety, following a 60-day trial.

Project director Yee Chee Keong, 51, and project engineer Wong Kiew Hai, 32, were convicted of recklessly endangering the men after failing to call for all work to be stopped even when cracks on crucial brackets were spotted.

They also faced a charge of obstructing the course of justice after deleting messages and photographs relating to the accident and lying to the authorities.

In the early hours of July 14, 2017, the uncompleted viaduct in Upper Changi Road East collapsed, causing the death of Chinese worker Chen Yinchuan, 31, and injuring ten others. The 11 workers, who were on the affected deck slab, plunged several metres amid metal bars, concrete and machinery as the superstructure broke down.

The technical cause of the collapse was the failure of the temporary corbels supporting the viaduct. Corbels are thicker brackets that act as support structures.

Four individuals and main contractor OKP were charged in 2018 in relation to the incident. The four were Yee and Wong; Indonesian Robert Arianto Tjandra, 47, the engineer who prepared building work plans for the viaduct; and Leong Sow Hon, 62, the accredited checker for its construction.

Tjandra and Leong were dealt with in 2019, while OKP was previously fined $10,000 for carrying out unauthorised strengthening works on the permanent corbels of the viaduct. OKP, however, claimed trial for the charge under the Workplace Safety and Health Act (WSHA).

The prosecution said there were warning signs in the lead-up to the collapse, as well as on the night before. These included multiple, repeated instances of cracks appearing on the corbels, which OKP, Yee and Wong ignored.

On June 30, 2017, two weeks before the collapse, cracks appeared but were not properly dealt with. OKP failed to inform the Land Transport Authority (LTA), which was the developer, and did not conduct a proper risk assessment review.

On the day of incident, 40 minutes before the collapse, Wong discovered much more serious cracks and called Yee. But neither made the decision to stop work at the site.

LTA representatives on-site, who saw the cracks at around 3.15am, felt shocked and worried. They asked Wong twice to stop work. But by the time he agreed to issue the order, it was too late.

The prosecution said OKP, Yee and Wong failed to safeguard the workers through their acts and omissions. "The obvious and necessary decision to take to ensure the workers' safety would have been to evacuate the workers and stop work pending investigations," it said in its submissions.

"There was ample time, about 40 minutes, for OKP, Yee and Wong to react and stop work upon their discovery of the cracks, but they did not do so."

After the collapse, Yee deleted his messages with Wong and lied to the authorities that he gave the order for work to stop but there was no time to do so before the collapse.

Similarly, Wong deleted his messages and the photographs he took of the cracks from his phone, and also lied that he had ordered work to stop.

In his verdict on Friday, Senior District Judge Ong Hian Sun said the cracks were an obvious sign of danger to the safety of the workers.

"OKP failed to call for a stoppage of works despite having ample time to do so," he said.

"Instead of stopping works immediately, (Wong and Yee) waited for further instruction and put the safety and lives of the workers on the deck slab at risk."

He added that Wong and Yee formulated a plan to lie to the authorities shortly after the collapse, and their deletion of messages obstructed the course of justice and hindered the trial.

"Wong's and Yee's lies corroborated their guilt," he said.

Tjandra pleaded guilty in November 2019 to three of five charges under the Building Control Act and the WSHA. Two other charges were taken into consideration during sentencing. He was jailed for 86 weeks, or slightly more than a year and nine months, and fined $10,000.

Leong pleaded guilty in June 2019 to failing to check the detailed structural plans and design calculations in accordance with regulations under the Building Control Act. One count of falsely certifying that he had carried out the required checks was considered during sentencing. He was jailed for six months and his appeal against the sentence was dismissed by the High Court in October last year. The cases against OKP, Yee and Wong have been adjourned for sentencing on April 8 and 9.

OKP, as a repeat offender, could be fined up to $1 million.

For recklessly endangering the workers, Yee and Wong each face a jail sentence of up to two years, a fine of up to $200,000 or both. They could each also be jailed for up to seven years and fined for obstructing justice.