Workplace incident on the Majura Parkway overpass, which runs parallel to the Sylvia Curley Bridge on the molonglo River. A pile driving rig appears to have had a malfunction.

Workplace incident on the Majura Parkway overpass, which runs parallel to the Sylvia Curley Bridge on the molonglo River. A pile driving rig appears to have had a malfunction. Photo: Graham Tidy

An incident in which a piece of machinery was knocked off alignment at a Canberra worksite on Wednesday morning was just the latest dangerous development at the site, the local building union says.

But principal contractor Fulton Hogan has defended its safety record at the Majura Parkway project, saying more than 500,000 man hours were worked at the site to the end of last year without any staff requiring medical treatment.

Work on the 11.5-kilometre, $288 million, four-lane Majura Parkway, which will link the Federal and Monaro highways, began a year ago and is due to be completed in 2016.

A pile driving rig appears to have had a malfunction on the Majura Parkway overpass, which runs parallel to the Sylvia Curley Bridge.

A pile driving rig appears to have had a malfunction on the Majura Parkway overpass, which runs parallel to the Sylvia Curley Bridge. Photo: Graham Tidy

ACT Work Safety commissioner Mark McCabe said employees were using a pile-driving machine next to the Sylvia Curley Bridge joining the Monaro Highway and Moreshead Drive in Fyshwick on Wednesday morning when it struck solid rock, throwing it off alignment. He said investigators had visited the site and decided that the incident did not pose a danger to workers. But CFMEU ACT secretary Dean Hall said it had the potential to endanger the lives of those working around it.

Mr Hall said there had been a range of safety problems from the start of the project and he accused Fulton Hogan of trying to hide incidents and dangerous near misses. The union representative said vehicles being driven by workers on the site had rolled over in November and December last year and last week a woman traffic controller working on the project had been struck by a car driven by a member of the public.

"At the moment the only thing that's preventing serious injuries and fatalities out there is luck,'' he said. ''Sooner or later when they roll the

dice … they're going to be in trouble, they're going to kill someone.''

Mr Hall said Fulton Hogan had a policy of hiding accidents from the public view by surrounding the scene of an accident with big trucks.

He also accused a subcontractor on the project, Canberra-based company Hewatt, of conducting a drug and alcohol test on workers on Tuesday in breach of its agreement with the union.

Representatives of Fulton Hogan said in a statement that the company's safety procedures had been implemented on Wednesday, which ensured the incident at the Molonglo River was not critical and project personnel were unharmed.

The traffic controller being struck by a motorist was a non-construction-related accident as it was committed by a member of the general public, the statement said. The incident is under criminal investigation by the Australian Federal Police.

Fulton Hogan said the company was committed to providing a workplace that keeps staff, customers, visitors, subcontractors, suppliers and the public safe at all times.

The company did not merely meet the minimum legal standards for workplace safety but actively promoted a culture of prioritising safety above all else, it said.

"Fulton Hogan have worked closely with all stakeholders in the project to date inclusive of the CFMEU and we will continue to fully engage with all the stakeholders as the project moves forward," it said.

Hewatt owner and managing director Geoff Hewatt confirmed compulsory drug and alcohol testing had been carried out at the Majura Parkway site on Tuesday, but he denied it was in breach of an agreement with the CFMEU.

Mr Hewatt said his staff were made aware when they signed their employment contracts that they could be subject to random drug and alcohol testing and he said he was very confident that the Majura Parkway site was safe.

Mr McCabe said Fulton Hogan had good safety procedures in place but WorkSafe ACT was working with it on how it supervised workers to ensure they complied with them. He said he was aware of incidents involving vehicles at the site, a couple of which inspectors were looking at closely.

Mr McCabe said the Majura Parkway was a complex project and generally the safety record at the site had been pretty good.