After the death of a worker at is Wagerup alumina refinery five years ago, Alcoa is facing fines of up to $200,000.
While cleaning a flash tank at the refinery in September 2009, Paul Fry fell 25m to his death through a manhole.
My Fry was employed by Transpacific Industrial Solutions who was contracted by Alcoa to clean the tanks.
According to Prosecutor John OíSullivan from the State Solicitors' office , Mr Fry was stood down for two weeks in 2006 for ignoring procedure, using a ladder to enter the bottom of a tank through a manhole.
After his death, pieces of scaffolding were installed across manholes to stop employees from entering them.
The first incident involving Mr Fry should have been eliminated, Mr OíSullivan said.
He informed the court manholes were an accessible attraction for employees who need to check the progress of their work.
He said the company should also have recognised that "where employees are engaged for 12 hours carrying out dirty, physically demanding and repetitive work, they may not be on their game".
In 2012, Transpacific was fined $170,500 over the incident for breaking Federal work safety law.
Defence Lawyer Sam Vandongen said Alcoa employees were not allowed on site while the tanks were being cleaned.
He argued Transpacific employees were the ìexpertsî and they had not alerted Alcoa to the hazard.
"It is a case of deliberate entry," he said.
Alcoa faces a fine of up to $200,000 when the sentence is handed down later this week.