The remediation work was project managed by Hunter and Central Coast Development Corporation.

In a statement this week Property NSW said PFAS was detected at low levels and concentrations identified had not triggered a requirement to notify the Department of Planning or the NSW Environment Protection Authority.

But a former Department of Planning chief risk officer who was sacked several weeks after warning of potential PFAS liability risks to the state because of the remediation works said he did not believe the department was adequately assessing its PFAS risk exposure.

He warned the department the HCCDC was possibly liable for any potential spread of the PFAS from the site because of the remediation works.

His employment was terminated in October under legislation allowing senior executives to be sacked for no reason, and after recommending entities reporting to the department should not only advise if they still held PFAS contaminants, but if they have ever had foam and if so, where was it used?

The department denied he was sacked because of the PFAS issue.

In a letter to the whistleblower on October 12 the department confirmed potential contamination at a Hunter Development Corporation managed site but said there was no liability for the department to include in its financial statements.

The department also rejected that there was a potential risk issue linked to alleged PFAS use in national parks.

Water, not PFAS agents, are used to combat fires in parks. All potential PFAS issues in relation to facilities, on parks or otherwise, have been advised to the Environmental Protection Authority as the lead government agency on PFAS matters, the department wrote.

The sacked former chief risk officer, who blocked the use of a PFAS chemical 10 years ago while manager of the corporate risk unit for Fire and Rescue NSW because of the potential risks, said he recommended a more comprehensive assessment of the departments potential PFAS risks because of his knowledge of its widespread use in the past.

A Property NSW spokesperson said original soil and groundwater contamination investigations of the Mayfield site in the 1990s did not include PFAS. Testing early this year was done for completeness, a spokesperson said.

Property NSW is currently completing a detailed remedial works program at the former BHP Steelworks property at Maitland. Per and poly fluoroalkyl substances (PFAS) were identified in groundwater on the site at concentrations less than half the applicable criteria, the spokesperson said.

An independent audit of the remediation works has confirmed the process is suitably managing the low concentrations of PFAS identified on the property.

Control of the BHP site was returned to Property NSW on November 20 after the most recent remediation works were completed.

A HCCDC spokesperson referred questions about the remediation work and the Mayfield site to Property NSW.