PIE viaduct collapse: Project staff did not stop works despite finding cracks, says prosecution

Yee and Wong, along with their employer Or Kim Peow Contractors (OKPC), are contesting the charges laid against them under the Workplace Safety and Health (WSH) Act and the Building Control (BC) Act. (PHOTO: SCDF)

SINGAPORE — Two men working on a segment of the Pan Island Expressway (PIE) viaduct in Changi that collapsed in 2017 had allowed work on the project to continue despite spotting cracks in two key load-bearing structures more than 30 minutes before the incident.

This was revealed in the prosecution’s opening statement on Thursday (1 August), the first day of trial for Yee Chee Keong, 49, and Wong Kiew Hai, 31.

Despite discussing and taking photographs of the cracks, Yee, who was project director, and Wong, a project engineer, did not put a stop to works being done. In doing so, they also ignored the advice given by a Land Transport Authority (LTA) site supervisor.

Yee and Wong, along with their employer Or Kim Peow Contractors (OKPC), are contesting the charges laid against them under the Workplace Safety and Health (WSH) Act.

OKPC is accused of failing to look after the safety and health of its employees, while Wong and Yee are each accused of recklessly endangering the safety of others by failing to call a stop to the works after the cracks were found.

The two men are also contesting one charge each of intentionally obstructing the course of justice by deleting a shared WhatsApp conversation that may have contained material relevant to the case.

Also on trial is Robert Arianto Tjandra, a consultant tasked with supervising the viaduct project and making plans for the building works. He faces one charge under the WSH Act and four under the Building Control Act.

OKPC’s executive director, Daniel Or Lay Huat is representing the firm for the trial.

Cracks found a month before collapse

All parties currently on trial were involved in the project for the design, construction and completion of a 1.8km-long viaduct from the Tampines Expressway to the Pan-Island Expressway and Upper Changi Road East.

Part of structure collapsed at about 3.30am on 14 July 2017, killing one work and injuring 10 workers.

Deputy Public Prosecutor Kristy Tan said on Thursday that OKPC had been awarded the viaduct contract by the Land Transport Authority on 23 November 2015.

She noted that the prosecution would be calling witnesses to testify that on 16 June 2017, OKPC’s employees discovered cracks on the face of a corbel – a type of concrete weight-bearing structure.

Yee had also been aware of the cracks and OKPC’s technical director Yeung Chun Keung will be testifying that he assessed the cracks on site, said the prosecution. However, OKPC did not inform Tjandra of the cracks at the time they were found.

On 30 June 2017, another OKPC employee found cracks on a different corbel and immediately reported them to Yee. Yeung again assessed the cracks on site and told Yee to get Tjandra to check on their adequacy.

Design flaws not communicated

On 3 July, Tjandra instructed his company’s design engineers to check on the adequacy of the design of the corbels for the project.

According to the prosecution, they discovered that wrong measurement had been used in the corbels’ design.

As a result of the error, the team found that the existing corbels were not suited for bearing the loads they were meant to support. While Tjandra initially been unaware of the design error, he also failed to tell OKPC of the flaw when he discovered it in early July.

Instead, Tjandra sent Yee a revised schedule for casting works on part of the viaduct section that eventually collapsed.

Workers could have been saved if work stopped

On the night of 14 July, OKPC proceeded with the scheduled casting works, starting at 1.30am. At about 2.53am, cracks on one side of the section’s corbels were spotted by workers onsite, including Wong.

“These cracks were clearly serious enough to (cause) alarm. The sight of them prompted Wong to have telephone conversations with Yee, who was off-site, about the cracks. Wong also sent photographs of the cracks to Yee via WhatsApp,” said the prosecution.

However, neither Yee nor Wong halted the works, despite the urgings from an LTA supervisor at the site.

“Had the works been promptly halted, the workers could have been out of danger as soon as they crossed over to the adjacent (section),” added the prosecution.

At around 3.25am to 3.30am, the cracked corbels gave way, resulting in the structure’s collapse.

Chinese national Chen Yinchuan, 31, was pronounced dead at the scene at 4.35am. The other 10 workers suffered injuries ranging from abrasions to lacerations and fractures.

“Tellingly, Wong and Yee deleted the WhatsApp conversation between them shortly after the collapse. They did so in haste to bury their responsibility, in the knowledge that their dilatory conduct had had grave consequences,” said the prosecution.

DPP Tan said it will also call on expert witnesses to testify that the cracked corbels were not designed to bear the weight that they were placed under at the time of the collapse. Yeung will be the trial’s first prosecution witness.

The current tranche of the trial is set to continue until 8 August.

On Wednesday, all three charges against OKPC's group managing director Or Toh Wat, were withdrawn. The company was also fined $10,000 on Tuesday over a separate charge of carrying out unauthorised strengthening works on the viaduct’s permanent corbels.

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