Aurora Environmental consultants have worked on several projects on Acid Sulfate Soils (ASS) sites where early involvement and assessment has allowed risks potentially posed by ASS to be considered and mitigated as part of the design process in a cost effective manner.
Acid Sulfate Soils (ASS) are soils, sediments and peats that occur naturally in low lying land and coastal regions of Western Australia. These materials contain iron sulphide minerals that are prone to producing acidity in the form of sulphuric acid when exposed to oxygen.
Disturbance of materials that are ASS or have the potential to be ASS can have significant environmental and economic impacts on environmental receptors such as waterways and wetlands, and man-made infrastructure. The acidity produced can also cause the accelerated dissolution of possible contaminants such as heavy metals into groundwater, thereby causing contamination that may require subsequent management.
If not disturbed then ASS can be benign. However, if development activities such as soil excavation and dewatering in areas that are ASS prone cannot be avoided, then assessment of the risk of disturbance is important. Early assessment of a site is critical to ensure that risks can be considered as part of the development design.