SINGAPORE – Structural cracks were found about a month before an uncompleted viaduct near Upper Changi Road collapsed and caused the death of one worker and injuries to 10 others.

On Thursday (Aug 1), the court heard that cracks were first found on June 16, 2017 before more were discovered on June 30. The Pan-Island Expressway viaduct collapsed on July 14, 2017.

The public prosecutor said the cracks were discovered when girdles, which form the part of the viaduct which was to be cast, were placed on them.

The cracks were found on permanent corbels – which are support structures – at pier 41, and later on pier 42 as well.

The area between the piers was to have been the longest span of the viaduct.

By early July, it emerged that the cracks, which were assessed to be structural in nature, were the result of inadequate corbel widths defined during the design stage of the construction.

The corbel widths for piers 41 and 42 were allegedly inadequate for the load the support structures were supposed to bear, and the design for corbel widths at eight other piers were also allegedly inadequate, with some at only a quarter of their required strength.

Deputy Public Prosecutor Yang Ziliang said in his opening statement on Thursday that “eight out of the 10 piers with permanent corbels would have developed significant structural cracks leading to sudden brittle failure and collapse when the viaduct was opened to traffic”.

The court heard that Robert Arianto Tjandra of subcontractor CPG Consultants became aware of the errors by early July 2017 but he did not inform Or Kim Peow Contractors (OKP), the main construction company behind the project.

He also did not redesign the corbels but attempted instead to take remedial steps on-site, including strengthening the supporting structures – steps which were allegedly illegal and proved futile.

When concrete was poured to cast the span of viaduct between piers 41 and 42 on the early morning of July 14, 2017, the viaduct collapsed.

Besides Tjandra, OKP’s project director Allen Yee, project engineer Wong Kiew Hai and executive director Daniel Or Toh Wat are also on trial over the collapse.

Yee and Wong are charged with not stopping work despite knowledge of the errors, and for obstructing justice by deleting WhatsApp messages and photos relating to the cracks.

Tjandra faces five charges in total.

OKP was fined $10,000 on Tuesday for carrying out unauthorised strengthening works on the corbels while accredited checker, Leong Sow Hon, was sentenced to six moths’ jail on July 4.

Leong, who was appointed checker by the Land Transport Authority, is the managing director of Calibre Consulting Singapore.

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