Acid Sulfate Soils

What Are Acid Sulfate Soils?

The term Acid Sulfate Soils (ASS) is used to describe sulfide-rich, natural soils, sediments and peat deposits, which can lead to the formation of sulfuric acid as a result of material disturbance and exposure to the atmosphere.

ASS are typically situated in wet, anaerobic (low oxygen or ‘reducing’) environments and are present along much of the NSW coast and within inland river or swamp systems.

They can become disturbed during excavation and broad-scale drainage works or as a result of groundwater dewatering. These activities expose the sulfide minerals to air, which cause oxidation of the sulphide minerals, leading to the formation of sulfuric acid.

Acid Sulfate Soil Problems

If left unmanaged the sulfide oxidation process can make the groundwater acidic, causing naturally-occurring heavy metals (such as iron, aluminium, arsenic and copper), to be leached from the soil and transported to surface water bodies.

This can lead to adverse impacts on vegetation, aquatic organisms (including ‘fish kills’), as well as causing damage to steel and concrete structures such as pipes, culverts, bridge piers or retaining walls.

Acid Sulfate Soil Assessment & Management

EI provides the following acid sulfate soils services:

  • Field assessment of potential and actual acid sulfate soils;
  • Advice on the handling, treatment and disposal of acid sulfate spoil (excavated ASS materials);
  • Assessment and management of water quality impacts;
  • Management of areas affected by acid sulfate soils, including remediation of impacted sites; and
  • Development of acid sulfate soil management plans (ASSMPs).