Stabilisation and solidification techniques are used to reduce the mobility and availability of organic and inorganic contaminants in soil to allow site redevelopment. The technique can be undertaken either ex-situ using homogenisation techniques or in-situ using rotary augering techniques.

There are various processes that may be used to achieve the remedial targets including the use of cementitous materials, organophilic clays and specialist propriety additives. The technique is suitable for various soils types even heavy clays. Treatable contaminants include heavy metals, polynuclear aromatic hydrocarbons, petroleum hydrocarbons, cyanides and PCBs.

The fundamental mechanisms that are involved in stabilisation are:

• Encapsulation – contaminants are physically trapped in the matrix of the stabilised material.
  
  
• Absorption and adsorption – the contaminants and agents in the solid matrix are electrochemically bonded.
  
  
• Precipitation – contaminants are precipitated from their aqueous form thus reducing their potential to leach;
  
  
• Detoxification – chemical reactions occur to detoxify contaminants to less toxic species i.e. reduction of chromium (VI) to chromium (III).
  
  
• Stabilisation/solidification requires a relatively small area to undertake the treatment and the treatment period is also timely compared to other techniques.