Acid sulfate soil management

Acid sulfate soils occur in about 40,000 square kilometres of Australia’s coastal zone. During the last major sea level rise new coastal landscapes formed through rapid sedimentation. Bacteria in these organically rich waterlogged soils converted sulfate from tidal waters and iron from the sediment into iron pyrite. When exposed to air, the sediments oxidise and produce sulphuric acid.

The entire floodplain below Kempsey to South West Rocks is underlain by extensive estuarine deposits that include potential and actual Acid Sulfate Soil (ASS) It is estimated that some 31,000 ha of floodplain below Kempsey is underlain by high risk ASS that is either at or near the surface.

The DLWC ASS Hotspot program (Project Managed by KSC and overseen by the MRFP) has been developed to reduce the intensity, frequency and duration of acidic water discharges into receiving water bodies. In addition restoring current scalded (no vegetation) areas to productive pastures is also a goal of the program.

The Collombatti-Clybucca area lies within the Lower Macleay Floodplain and the Upper Maria River – Connection Creek area lies within the Hastings River catchment and both were nominated as two of the seven initial Acid Sulfate Soils Hot Spot Areas. In September 2001 KSC and the DLWC initiated the Collombatti – Clybucca and Upper Maria River – Connection Creek ASS Hot Spot project. The aim of the projects was to implement remediation strategies to reduce the frequency, intensity and durations of acid water discharge events.