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Successful Remediation of over 110,000m³ of Acid Sulfate Soils at the Newcastle Rail Project

January 12, 2023
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The Newcastle Rail Project was a 38 hectare development in Newcastle, New South Wales. During the soil surveys, potential acid sulfate soils in excess of 110,000m³ were identified.

Acid sulfate soils (ASS) are a type of soil that contains iron sulfides (commonly pyrite) that, when exposed to oxygen and water, can produce sulfuric acid. This acidification process poses several dangers to the environment, particularly in coastal regions. In Australia, ASS is a significant concern due to its prevalence and potential impacts on ecosystems, agriculture, infrastructure, and water quality.

The dangers of acid sulfate soils include:

1. Soil and Water Acidification: When ASS are disturbed or exposed, such as through land development or drainage, the sulfide minerals react with oxygen and water, leading to the release of sulfuric acid. This acidification damages the soil structure, decreases fertility, and lowers pH levels, making the soil unsuitable for many plants. Acidic runoff can also contaminate water bodies, harming aquatic organisms and affecting drinking water supplies.

2. Toxic Metal Release: Acidification of ASS can mobilise toxic heavy metals, such as aluminum, iron, and manganese, which are bound to the soil particles. These metals can be released into water systems, leading to water pollution and potential ecological damage. Elevated levels of heavy metals can be harmful to aquatic life and may bioaccumulate in the food chain, posing risks to human health.

3. Damage to Infrastructure: Acid sulfate soils can corrode infrastructure components made of concrete, steel and other materials. The acidity corrodes metal structures like pipes, bridges and buildings, leading to structural degradation and increased maintenance costs. This can have significant economic implications for coastal regions where ASS are prevalent.

4. Environmental Impact: ASS have the potential to impact ecosystems and biodiversity. The acidification can disrupt natural habitats and negatively affect the growth and survival of native flora and fauna. Acidic conditions can also alter microbial communities in the soil, impacting nutrient cycling and overall ecosystem functioning.

In Australia, acid sulfate soils are widespread, particularly in coastal regions, estuaries and floodplains. These soils have been formed over thousands of years as a result of geological processes and changes in sea levels. The country’s extensive coastline and diverse ecosystems make the management and prevention of ASS impacts crucial.


EESI created and implemented a remediation plan that involved the delineation of soils and coal wash material. The contaminated material was neutralised with lime and then tested to ensure the potential acid sulfate soils had been treated.

Due to the careful management by the EESI team, stage 1 of remediation for this major project has been successfully completed.


Thanks to EESI’s efficient acid sulfate soil (ASS) remediation process and swift turnaround time, the Newcastle Rail Project was able to proceed with their planned activities without any delays.

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The Environmental Earth Sciences International Group acknowledges the Traditional Custodians of country throughout Australia and their connections to land, sea and community. We pay our respect to their Elders past, present and emerging and extend that respect to all Aboriginal and Torres Strait Islander peoples today.