- inappropriate disturbance is a threat to our environment

Dig, dewater, dump - disturbing ASS threatens the environment

Acid sulfate soils (ASS) are soils and sediments that contain iron sulfides. They occur naturally in Western Australia and are harmless when left in a waterlogged, undisturbed environment.

However, when exposed to air, through drainage or excavation, the iron sulfides in the soil react with oxygen and water to produce iron compounds and sulfuric acid. This acid can release other substances, including heavy metals, from the soil and into the surrounding environment and waterways.
Off site impacts include:

• fish kills
• damage to fisheries and aquaculture industries
• harm  to tourist resources such as fishing grounds, swimming areas and recreational waterways
• damage to infrastructure - corrosion of concrete and steel pipes, building  foundations and bridges

Activities with the potential to disturb ASS must be managed carefully to avoid environmental harm.

Acid sulfate soils in Western Australia

• Acid sulfate soils in WA - ASS are widespread in low-lying coastal areas of Western Australia. This links to further information on ASS materials in this State.
• ASS risk maps - you can check the ASS risk in your area by viewing risk maps developed by DEC.
• Guidelines / fact sheets - DEC has produced a series of fact sheets and guidelines to assist you with the identification, investigation and management of ASS in WA.
• DEC forms / calculation tools - projects where ASS materials may be disturbed require an acid sulfate soil management plan and completion of related forms.  This links to the DEC forms and tools to:
  • calculate pumping rates and times for dewatering in ASS areas
  • gauge the quantity of lime required to treat ASS
• Planning requirements - WA Planning Commission (WAPC) is responsible for land use planning and land development in the State. This links to the WAPC website for advice and guidance on rezoning, subdividing and developing land that contains ASS.
  A WAPC Acid Sulfate Soils Self-Assessment Form and Clearance of Conditions Report must be submitted to DEC as a condition of approval for planning proposals in high to moderate ASS risk areas.
• Technical reports - produced by DEC and other agencies.
• ASS survey in Perth metro region, Swan Coastal Plain The Department of Environment and Conservation undertook a second stage of the acid sulfate soils (ASS) mapping program between 2008 and 2010. The purpose of the project is to validate the predictive ASS risk within the Perth metropolitan area.
• Experimental Oxidisation of Bassendean Sands The primary purpose of this study is to determine the adequacy of the current action criterion for managing the sandy soils of the BDS. These sands have low sulfur content while producing extremely now pHFOX values. The experimental study carried out natural soil oxidation to determine the rate of acid generation from Bassendean sands with less than 0.03%S.

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