A company that has been ordered to clean up chemical pollution from a 1970s industrial dump in southern Sydney says it has already met all its responsibilities.

BIS Cleanaway, formerly owned by Brambles, ran the industrial dump at Lucas Heights until 1980.

A Brambles spokesman says a clean-up was completed by 1989, after the Federal Government ordered that it be remediated.

New South Wales Environment Department spokesman Niall Johnston says heavy metals and petrochemicals have been a problem at the site for a decade.

"We've taken samples of those seeps showing levels of contaminants of come concern," he said.

"Of course it does have the potential to affect the local environment."

Mr Johnston says the latest clean-up has been ordered because the company would not do it voluntarily.

But Brambles argues it has met its responsibilities, and is reviewing the Department's order with lawyers.