33,797 hectares of land within the Manning Valley has been identified as being affected by potential acid sulfate soils (ASS). 4,500 hectares has been identified as ASS hot spots by the NSW Government.
ASS are sediments naturally occurring in estuarine and floodplain areas, which were once high in organic matter (such as old mangrove forests and other wetlands).
These sediments occur below the water table and when left in place are not a problem. When removed from a waterlogged state, such as during excavation or as a result of drainage (lowering the water table), these sediments oxidise and the passage of water through the material creates acid run-off or leachate that can contaminate surface and ground water.
In addition to the acid nature of the water, it also carries increased levels of aluminium and other metals, which can be toxic to aquatic flora and fauna and those species living in bottom sediments. The impact on fish stocks and oyster production can be significant.
For those wanting to develop land that may be affected by ASS and require planning advice, we have prepared a fact sheet to help you.
For more information about ASS visit the NSW Primary Industries website.