ACID SULPHATE SOILS

Dinglebird Environmental offers comprehensive and professional consultation on Acid Sulfate Soils (Acid Sulphate Soils), investigation, management, compliance and remediation. Land development in WA must consider the potential presence of Acid Sulfate Soils (Acid Sulphate Soils) and development in areas of Acid Sulfate Soils (Acid Sulphate Soils) risk must be managed appropriately. Many development approvals are conditional on regulatory acceptance of Acid Sulfate Soils (Acid Sulphate Soils) Investigations or Management Plans (ASSMP).

The spelling of sulphate varies within Australia (and even within Dinglebird Environmental’s office!), and for the purpose of search engine optimisation we have included both spellings each time – it’s like an “each-way bet.” Apologies for the doubling-up.

Acid Sulfate Soils (Acid Sulphate Soils) are naturally occurring waterlogged soils that contain pyrite or other iron sulphide minerals. These soils are found in low-lying coastal areas, especially next to estuaries. Acid Sulfate Soils (Acid Sulphate Soils) are also often found adjacent to some wetlands elsewhere on the Swan Coastal Plain, and near salt lakes or seasonally waterlogged land in inland areas of the state.

Acid Sulfate Soils (Acid Sulphate Soils) are generally harmless if not disturbed. However, if exposed to the air by lowering of the water table (e.g. dewatering, drainage, excavation or excessive pumping of groundwater), the pyrite will react with oxygen from the air to form sulfuric acid and sulfate minerals, releasing them into the soil and groundwater, often in harmful quantities. Acid Sulfate Soils (Acid Sulphate Soils) groundwater is highly polluting and toxic to wildlife, and therefore requires careful management to achieve government compliance. The acid produced by this reaction can release aluminium, nutrients, and heavy metals (such as arsenic) previously held in the soil matrix.

If houses or other urban infrastructure are built directly on Acid Sulfate Soils (Acid Sulphate Soils) that are being exposed to oxygen, there is a risk that structural damage to houses will occur. The structural damage may be caused by chemical reactions of sulfuric acid and sulfate minerals with concrete, which reduce its strength. The upward and outward forces generated by swelling soils beneath houses may also cause concrete floors to heave upwards by several centimetres, may crack walls, and may distort door and window frames. This often makes it difficult to open and shut doors and windows in houses that are being damaged by pyrite oxidation.

Generally, structural damage to houses by pyrite is caused by a combination of chemical and physical factors of Acid Sulfate Soils (Acid Sulphate Soils). These structural problems can be expensive to repair, and require specialised engineering techniques to be used so that problems do not recur.