Comprehensive, Perth-Based Acid Sulfate Soil Services

What is Acid Sulfate Soil?

Acid sulfate soils (ASS) are naturally occurring soils and sediments containing iron sulfides, most commonly pyrite. When ASS are disturbed and exposed to air, the iron sulfides in the soil react with oxygen and water to produce a variety of iron compounds and sulfuric acid. Initially a chemical reaction, this process is accelerated by soil bacteria.

The resulting acid can release other substances, including heavy metals, from soil and into groundwater and the surrounding environment. This contamination can lead to significant environmental and structural issues, including soil degradation, water contamination and infrastructure damage.

ASS are commonly disturbed by activities such as:

• Construction and Development: Infrastructure projects such as roads and tunnels, as well as other major earthworks, can expose ASS to air and trigger acidification.

• Agricultural Practices: Drainage of wetlands for farming can lower the water table, leading to the oxidation of previously submerged sulfide minerals.

• Groundwater Extraction: Excessive pumping can reduce groundwater levels, exposing ASS to atmospheric oxygen.

What are the Risks of Acidic Soil?

Acidic sulfate soils present risks that affect everything from local ecosystems to the structural integrity of infrastructure projects.

Soil Degradation

The most profound effect of acid sulfate soils is soil degradation. Sulfuric acid lowers soil pH to create highly acidic conditions, in turn mobilising toxic materials like aluminium and iron into the soil. This degrades the quality of the soil, leading to consequences such as:

• Loss of Soil Fertility: The acidic conditions disrupt nutrient availability, making plant growth more difficult and reducing wider agricultural productivity.

• Structural Damage to Soil: Acidification can break down soil aggregates, leading to increased erosion and reduced water-holding capacity.

• Release of Toxic Metals: Mobilised metals can contaminate groundwater and surface water, posing risks to human health and aquatic life. This applies to water used for drinking and irrigation.

Contamination of Groundwater

Sulfuric acid can percolate through the soil process and enter groundwater systems. This ability to rapidly contaminate ground water can cause ASS to:

• Acidify Groundwater: The oxidation of sulfides lowers the pH of groundwater. This shift can disrupt the natural balance of aquatic ecosystems and render the water unsuitable for agricultural, industrial or potable uses.

• Mobilise Heavy Metals: Acidic conditions increase the solubility of elements such as cadmium, lead, arsenic and aluminium. If present in the soil, these materials can leach into the groundwater, posing significant health risks to people and wildlife.

• Degrade Water Quality: Contaminated groundwater can exhibit reduced oxygen levels and elevated concentrations of dissolved metals. Such degradation can harm aquatic life and compromise the usability of the water for other applications.

Environmental and Financial Consequences

Poor ASS management can lead to a host of financial and environmental consequences for business owners and developers:

• Expensive remediation works to treat ASS occurences

• Project delays caused by ASS occurences

• Difficulties securing planning permission

• Corrosion of concrete and steel (compromising the integrity of infrastructure)

• Degradation of ecosystems

What WA industries can be Affected by Acid Sulfate Soils?

Insufficient or nonexistent ASS management can lead to severe financial repercussions across various sectors and industries:

• Agriculture: Soil acidification will renderi land unproductive, causing crop failures. Farmers may face decreased yields and increased costs to rehabilitate their soil.

• Infrastructure: ASS can corrode concrete and steel structures, compromising the integrity of buildings, bridges and pipelines. The costs of repairing or replacing damaged infrastructure can be substantial.

• Fisheries and Aquaculture: Acidic runoff from disturbed ASS can lead to fish kills and loss of biodiversity in aquatic ecosystems, adversely affecting the commercial and recreational fishing industries.

• Property Development: Unanticipated ASS issues can halt construction projects, leading to delays and increased expenses for soil treatment. In turn, this will make proving compliance a more difficult, lengthy and expensive process.

How can Acid Sulfate Soils be Managed and Treated?

As a proudly West Australian company, West Soil & Water offers a range of soil management services tailored to the unique environment of Perth and surrounding regions. We conduct:

1. Baseline Investigations: WSW carries out investigations to determine the presence, extent and severity of ASS on your site. This information is used as a foundation for future planning and monitoring.

2. Acid Sulfate Soil Management: Across Western Australia, we develop and implement acidic sulfate soil management plans (ASSMPs) to ensure potential risks are identified and managed proactively. These plans outline strategies for soil handling, treatment and monitoring throughout the lifecycle of a project.

3. Acid Sulfate Treatment: We tailor treatment solutions to sites in Western Australia, suiting the needs of each individual project.

4. Soil Monitoring: For Western Australian projects, we monitor our treatment solutions to be sure of their long term efficacy.

Management Strategies You Can Implement Yourself

Whilst WSW always recommends engaging an experienced environmental consultant to assist in managing acid sulfate soils, there are some steps you can take to identify potential contamination before it occurs:

1. Desktop Assessment: Review your existing surveys and records to determine if the proposed site is known for ASS occurrence. You can use the Atlas of Australian Acid Sulfate Soils for useful information.

2. Site Inspection: Conduct a thorough on-site evaluation, looking for visual indicators such as soil colour changes, unusual vegetation patterns or soil disturbance.

3. Soil Sampling and Testing: Collect soil samples from various locations across the site and complete testing to determine pH levels.

4. Consultation with Experts: Engage environmental consultants to interpret data and provide recommendations. Professionals can offer insights into potential risks and management strategies tailored to the specific site conditions.

Create an Acid Sulfate Soil Management Plan with West Soil & Water

Effective acid sulfate soil management is essential to prevent environmental degradation, infrastructure damage and costly remediation efforts. By identifying risks early, implementing appropriate treatment solutions and adhering to best-practice management strategies, businesses and developers can mitigate the impact of ASS on their projects.

West Soil & Water provides tailored investigation, management and monitoring services across Western Australia, ensuring compliance and long-term stability. If you are interested in an ASSMP, baseline investigation or treatment solution, please contact WSW to speak with one of our specialist consultants. You can reach us at sam@westsoilandwater.com.au or on 0424 021 264.