Another worker has been seriously hurt at the trouble-plagued Forrestfield Airport rail link project in Perth, suffering severe chemical burns that caused the skin on his feet to peel off.
Work safety authorities confirmed the man was on night shift in late June when he stood in water containing a substance that caused burns to his feet.
The CFMMEU told AAP the 64-year-old was standing in the contaminated water for seven hours and when he removed his socks, skin peeled off.
Western Australia state secretary Mick Buchan said the "toxic slurry" was higher than his boots and he required an ambulance.
"It's not acceptable for any worker anywhere to be made to stand in water for hours on end," Mr Buchan said in a statement.
"This project has been a disgrace from the start and there will be more avoidable injuries on this job unless our state government stops imagining that cheap equals good value."
WA Premier Mark McGowan said work safety authorities had carried out a large number of inspections.
"We are doing our best to make it safe," Mr McGowan told reporters.
"WorkSafe and the state government are doing everything we can, in conjunction with the union, in conjunction with the company, to make it as safe as possible."
The part-federally funded project is a joint venture between Italy's Salini-Impregilo and Perth-based NRW Holdings, and includes an 8km tunnel under the Swan River.
In July last year, a 26-year-old New Zealand man was left in a critical condition after being struck by a flailing hose at the behind-schedule project.
In September, a leak in a tunnel-to-tunnel cross passage created a sink hole and damaged a 26-metre section of one tunnel.
The man who suffered the burns has been discharged from hospital and will likely need ongoing treatment, the union said.
