Land contamination occurs when dangerous chemicals are present in the soil matrix that do not occur naturally. Invariably, contamination has resulted from inadvertent spillage and leakage (e.g. accidental spills, storage tank failures, contaminated runoff, etc.) during operations involving hazardous chemicals. But more alarmingly, much of the contamination has resulted from the dumping of waste materials.

Common contaminants include:

Stringent environmental legislation, advances in processing technology, environmental safety improvements and development of economically and ecologically sustainable practices to utilise wastes have all served to decrease the rate of generation of more contaminated land. But the problem of what to do with the existing tracts of highly contaminated land remains a major challenge.

Like most developed nations, Australia has extensive contaminated land problems. In most cities there are large tracts of land that lie idle because of the presence of toxic substances in the soil. It is only in the last decade that the true extent of the problem has been realised.

There are an estimated 150 former gasworks sites in Australia requiring remediation. Independent reviews suggest that there are in excess of 7,000 contaminated sites in the state of NSW with a total clean-up cost of two billion dollars.

Victoria's clean-up costs are estimated to be of a similar magnitude. In Western Australia a report by the Auditor-General in November 2002 stated that the State Government could not afford to clean up the "thousands of contaminated sites" even if it knew where they all were. Clean-up costs for the whole country - using current technology - are estimated at between five and eight billion dollars!