What are the hazards?

Different hazards are posed by different kinds of acid sulphate soil (sulphidic or potential acid sulphate soils, raw acid sulphate soils and ripe acid sulphate soils). There are hazards on site, and hazards from acid drainage and floodwaters.

The most severe hazards are presented by raw acid sulphate soils that are actively generating sulphuric acid and which have further reserves of acidity in the form of oxidisable sulphides.

Corrosion of steel pipework on a sugar cane plantation, Queensland.

Engineering hazards include corrosion of steel and concrete, low bearing strength and uneven subsidence, very high permeability of undisturbed muds but low permeability and slow consolidation of reworked material, and the blockage of drains by ochre.

In addition to chemical hazards, there are physical limitations. Root development is restricted so water reserves in the subsoil are not available to the crop. Soil ripening is arrested, so the soil remains soft and saline at shallow depth.

In the case of sulphidic soils, the hazards associated with acidity are potential hazards and will not materialise unless the soils are drained or excavated. However, sulphidic soils are commonly saline, and sulphidic clays and peats are also unripe (soft and of low bearing capacity).