A toxic cancer-causing chemical is leaking into the Parramatta River in Sydney’s west from a shipping container facility, forcing a major decontamination of the area.

The Patrick’s site on the Camellia peninsula, near Rosehill Racecourse, has been found to be leaking the chemical Chromium VI, posing a risk to people and marine life.

The chemical was made famous by US environmental activist Erin Brockovich, Fairfax newspapers said.

On Friday the NSW Department of the Environment and Climate Change issued a formal notice on the property, which will force a major decontamination to be undertaken.

Workers at the shipping container facility told Fairfax that they had repeatedly raised concerns about the site after seeing bright green puddles in the yard and nearby after rain.

“We wanted to know what was wrong with it,” former worker Gary Hayton said.

But Patrick says dust tests and urine tests over the past 18 months have shown there was never any threat to staff.

“All testing has confirmed that there is no dangerous exposure to employees, and in fact have been well below the regulated limits,” the company said.

The contamination source was an old chrome factory next to the racecourse, Fairfax said.

Local state Liberal MP Michael Richardson said the NSW Government had known about the contamination for years, and had acted too slowly to clean up the problem.

“The government has known about this for years, and you can only describe the pace of the clean up as glacial,” he told Fairfax.

“We knew the toxic plume was spreading under the peninsula. It’s too little, too late.”