Q Why did the Land Transport Authority (LTA) award the contract to build the PIE-TPE viaduct to Or Kim Peow (OKP) Contractors? Was it based on OKP's lowest bid?
A With a bid of $94.6 million for the tender, OKP submitted the lowest bid for the Design and Build contract in November 2015, which was 27 per cent lower than the next lowest bid of $129.7 million by Yongnam Engineering.
But an LTA spokesman said it considers more than just price in assessing tender proposals, citing other "quality aspects", such as the relevant experience of the participating contractors, their safety management systems and practices, track record, project-specific technical, risk management and resource management proposals.
"All these quality aspects would be considered together with the price proposal to determine the award of the tender," he added.
For all construction tenders, the price-quality method is used by agencies as a framework. The price-quality weighting used for Design and Build projects before January last year is between 60:40 and 70:30.
An OKP spokesman said that despite its lower bid relative to the competition, there was "no compromise on the project's safety".
"With more than 50 years' track record in the industry, we are committed to ensuring project quality and workplace safety for projects that we undertake. For every tender bid that we participate in, we will evaluate and submit a bid which we feel is competitive and offers us reasonable profit margins."
Q Why was OKP, which was given 25 demerit points by the Ministry of Manpower (MOM) and blacklisted for three months earlier this year, allowed to work on a government project?
A In September 2015, OKP was involved in an incident in which one worker was killed and four injured after they fell more than 6m from a dislodged platform. The firm was found to have breached the Workplace Safety and Health Act for failing to ensure the working platform erected was safe for use.
According to the MOM website, 25 demerit points are issued to contractors for an accident that leads to death of one person. The points were given this January after the firm was prosecuted in court.
The Straits Times understands that when OKP was awarded the tender, its involvement in the 2015 fatal incident was still being investigated. OKP and one of its site supervisors were convicted of safety breaches only last Tuesday.
Firms that accumulate 25 points will be blacklisted for three months, which bars the contractor from bringing in foreign workers as all work passes will be rejected by MOM during the blacklist period.
They will still be allowed to renew passes for existing workers.
But Lian Beng construction manager Shie Chee Hwa said being on the MOM blacklist has the effect of limiting the firms' ability to tender for new projects. He said: "They will face more targeted and unannounced spot checks for their existing projects too, which can be several times in a month."
But he added that firms can still bid for public sector projects with their existing workforce, though they would have the spectre of the blacklist hanging over them.
Q Why did the corbels holding up the rest of the structure give way?
A The use of corbels in building elevated roads is a standard practice here and around the world, said Mr Chong Kee Sen, former president of the Institution of Engineers, Singapore.
Corbels are support structures designed to hold only a temporary load at the early construction stage, sharing the load with the rest of the scaffolding. When the concrete in the rest of the structure has set, it becomes self-supporting and most of the load is lifted from the corbels, he said. "During construction, corbels are designed to factor in the amount of load that engineers foresee it will carry during this phase, with around 10 per cent tolerance for the typical load it is expected to take."
Foreseeable activities include the weight of the concrete as well as all additional manpower and equipment needed on top of the structure. The task of calculating the load factors falls on the designers or engineers, which in this case will refer to CPG Consultants.
Mr Chong said corbels can fail in scenarios such as ground movements, overloading or design flaws, though he warned against jumping to conclusions before the investigations are complete.
Q What are the measures in place to prevent workplace deaths?
A While there have been 21 workplace deaths this year, only four occurred in the construction sector. There were 66 workplace accidents last year.
MOM conducts more than 6,000 worksite inspections every year, with some firms selected more than others, its spokesman said.
Those found with safety breaches will be taken to task, as "employers bear primary responsibility for managing risks at work and have to take full ownership of the safety and health matters of their employees".
In OKP's case, MOM officers had stepped up inspections on OKP's worksites after the 2015 accident.
Said the spokesman: "Our officers identified minor WSH (workplace safety and health) infractions on OKP's worksites, and have worked with OKP to rectify them immediately."
The last time MOM inspected OKP's worksite at the flyover viaduct was on April 3 - the day before it was removed from the blacklist, he revealed. At the time, the beams and deck slabs had not been installed at the site where the accident occurred. No infringements were found, said the spokesman.
Q Why did LTA stop work at all its worksites for half a day, and what was done during this time?
A All public road and rail worksites under LTA had to observe a "safety time-out" on Friday after the accident, according to its statement.
The Straits Times understands that the time-out ended around 1pm after all contractors carried out a voluntary review of their safety practices.
The Workplace Safety and Health Council has led several planned safety time-outs after a spate of accidents or dangerous occurrences. A time-out differs from a stop-work order, which only MOM can issue and was meted out on the Upper Changi Road East site on Friday.
Correction note: This story has been edited for clarity.