Acid Sulfate Soils

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What are Acid Sulfate Soils?

Acid Sulfate Soils (ASS) are typically found in soils that contain iron sulfides. When these soils are exposed to oxygen, either through activities like excavation or the lowering of the groundwater table, the iron sulfides can oxidize. This process results in the production of sulfuric acid.

ASS is prevalent in coastal areas, particularly those with a rich history of organic matter. When these soils are disturbed and exposed, the resultant runoff can impact stormwater, groundwater, and even our natural aquatic systems. This acidic runoff can alter the pH balance of the waters it enters, increasing metal concentrations and diminishing the water’s natural buffering ability.

Acid Sulfate Soils Assessment

Depending on local acid sulfate soils mapping and the planned depth and method of excavation, local councils may require an Acid Sulfate Soils Assessment as part of a development application.

ENV’s dedicated team of environmental scientists kickstart the assessment process with a comprehensive desktop study. This study encompasses a review of existing acid sulfate soil maps, an evaluation of the proposed work, and potential impacts on soil and groundwater.

Following this, our experts engage in more detailed analyses. This involves drilling boreholes with our specialised acid sulfate soils drilling equipment, setting up groundwater monitoring wells, and taking acid sulfate soil samples at different depths to comply with regulatory standards.

Post-collection, these samples undergo preliminary in-field screening. This is succeeded by rigorous acid sulfate soils testing in a laboratory. The findings are then compiled and analysed in a comprehensive report to ascertain if there’s a need for an Acid Sulfate Soils Management Plan (ASSMP).

Management of Acid Sulfate Soils

If an ASSMP is deemed necessary, ENV’s environmental consultants and engineers will craft a tailored treatment strategy. This strategy aims to preclude any potential on-site and off-site repercussions. Our in-house environmental remediation team ensures that the strategy is not only cost-effective but also feasible. Their responsibilities include:

  • Coordinating the treatment and beneficial reuse of Acid Sulfate Soils, pending regulator approval
  • Overseeing the acid sulfate soils liming
  • Managing the transportation of acid sulfate soils
  • Handling the acidic surface water treatment
  • Managing acid sulfate soils groundwater treatment

Acid Sulfate Soils Validation:

The validation process, often initiated during or after the construction phase, aims to verify if the pre-established criteria (such as liming rate and water quality discharge pH) have been met and if there’s a need for additional treatment.

As part of this validation, ENV’s consultants frequently collect samples of soil and water, in alignment with the guidelines set in the Acid Sulfate Soils Management Plan. These findings are then relayed to both the client and regulators as necessary.

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