But the ACT government says the case has highlighted ''some areas for improvement'', and is looking at tighter monitoring of potential polluters and tougher powers for the Environment Protection Authority.

The groundwater at the former Koppers plant remains contaminated with the carcinogen hexavalent chromium, a chemical made notorious by the Erin Brockovich case.

Koppers allowed the chemical to reach 2430 times the safe limit by 2007, and failed to send in a string of groundwater monitoring results between 1998 and 2005, sometimes for entire years.

The EPA never disciplined the multinational corporation for the pollution or the missing test results, and it failed to conduct annual compliance checks of its legally binding 2002 environmental authorisation until 2005, the year the plant closed.

The government has now released the results of ''urgent testing'' - conducted after Fairfax Media raised questions about the case - that confirm the pollution has not spread off the 20-hectare block in Hume.

It has also asked the new owner of the land to conduct on-site tests as soon as possible, and Environment Minister Simon Corbell has asked the EPA to work with the company to ensure the pollution is ''actively managed'' into the future.

Mr Corbell reassured Canberrans that there is no risk to human health or the environment. ''The advice to me from the EPA is clear and unequivocal: there is no presence of chromium 6 in the groundwater at the off-site bore,'' he said.

Greens MLA Shane Rattenbury wrote to Mr Corbell last week expressing his concern about the contamination and asking what had been done in response, particularly about the EPA's enforcement of reporting requirements.

Mr Rattenbury said a continuing review of the ACT's environment laws must take the issues identified in the Koppers case into account.

''I will be monitoring this closely to ensure this happens,'' Mr Rattenbury said.

''We need to get clarity on whether the shortcomings in the Koppers matter were a result of legislative gaps, inadequate processes in the EPA, or inadequate resourcing to do the job properly,'' he said.

Mr Corbell said the government had already been looking at legislative reform as part of the review of the 1997 Environment Protection Act.

It is considering changes that would allow the environment watchdog to act when there is the ''potential for harm'' - rather than ''actual harm'' - of the environment.

It is also looking at giving the EPA more flexibility to deal with potential polluters that fail to comply with reporting requirements.

The new testing was conducted by an independent laboratory given samples taken on March 21, after the EPA was first approached on the issue, but before revelations about the pollution were published.

The results are available online.