Darwin Airport has been accused of disregarding measures to prevent toxic PFAS chemicals flowing into waterways.

Investigators from the Federal Department of Infrastructure for the corporation responsible, Airservices Australia, also failed to act on problems with wastewater disposal at the site, even after “repeated indications of non-compliance”.

The review was sparked by a whistleblower firefighter who said PFAS chemicals had been “covertly dumped” from the site.

The report found “non-conformances that may have had potential adverse impacts on the environment”, but has not found any breaches of the Federal Airports (Environment Protection) Regulations, and did not recommend sanctions against Airservices Australia.

It called on Airservices to expand its environmental monitoring program to cover routine testing of surface and groundwater, and to undertake a risk assessment of PFAS leaching from the fire training ground.

Darwin Airport is still transitioning to a PFAS-free foam and is due to be finished sometime in mid-2019.

“Airservices did not monitor stormwater quality or act on the recommendations [from regular audits] with regards to assessing the risk of releasing wastewater to stormwater [drains],” the report found.

“Additionally, Airservices did not respond to issues identified in the audit and assurance reports that indicated Darwin personnel were not operating in accordance with national directives and local instructions.

“Such repeated indications of non-compliance should have triggered intervention.”

Airservices has responded, saying the company “takes its environmental management responsibilities very seriously”.

“Airservices has already implemented improvements that address the majority of issues identified and is acting on the report's other recommendations,” the spokesperson said.

“Of the eight allegations investigated, six were disproven or unsubstantiated, and there were no regulatory breaches identified.”