Remediation methods for contaminated areas

Different soil and groundwater remediation methods are suitable for different contaminated sites. When choosing a method, it is important to take into account the risk assessment and conduct remediation according to the risk posed by contamination of the area. Factors affecting the choice of remediation method include:

  • soil types
  • number, type, extent, concentrations and location of contaminants
  • groundwater and surface water conditions
  • property features, such as the proximity of buildings and their intended use
  • economic, social and environmental impacts of a project (sustainability)
  • available time
  • budget and costs
  • objectives set out in the PIMA decision.

A number of complementary methods may be used for remediation if: the soil or groundwater has been contaminated with several different contaminants; there are high concentrations of contaminants or they vary widely; or the properties of the soil make it difficult to treat.

In some cases, risk management is sufficient in a contaminated area, which will not actually be remediated, but instead the concentrations and migration of hazardous substances are monitored or restricted to control risks. This is sometimes also referred to as restoration.

The actual remediation can be conducted without excavating soil on site (in-situ), by excavating and treating soil or groundwater on site, or by transferring soil or groundwater to another site for treatment. During in-situ remediation, normal activities within the area can typically be continued without disruption.

Remediation method:

  • soil replacement and isolation 
  • biological remediation 
  • chemical remediation 
  • physical remediation
  • thermal remediation
  • other methods, such as screening

Soil replacement is by far the most common method of remediation. Contaminated soil is excavated and replaced with clean soil. The contaminated soil is transported to a treatment plant with an environmental permit. Contaminants in the soil and excavated soil can also be isolated, thus preventing their spread and migration into the environment. However, isolation does not remove hazardous substances from the soil.