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Acid Sulphate Soils

Acid sulphate soils (ASS) are naturally occurring soils, sub marine sediments or organic substrates one example is peat these formations are formed under waterlogged conditions. These soils contain iron sulfide minerals (predominantly as the mineral pyrite) or their oxidation products.

If left undisturbed below the water table, ASS are benign. However if the soils are drained, excavated or exposed to air by a lowering of the water table, the sulfides react with oxygen to form sulfuric acid.

ASS undergo a chemical reaction known as oxidation releasing toxic quantities of heavy metals to the local eco system and often with compound effects to the environment.

Release of this sulfuric acid from the soil can in turn release iron, aluminum and other heavy metals (particularly arsenic) within the soil. Once mobilized in this way, the acid and metals can create a variety of adverse impacts on the environment: killing vegetation, seeping into and acidifying ground water and surface water bodies, killing fish and other aquatic organisms, creating algae blooms. The effect on buildings and other structures is that bricks and mortar crumble concrete and steel to the point of failure.

One of the effects of this reaction can be shrinkage of volume and this can cause subsidence and damage to surface structures such as bridges, buildings and roads.

To avoid the possibility of this happening there a 5 main courses of action to consider

  1. Minimising disturbance
  2. The uses of Trenchless Technology wherever possible
  3. Neutralisation by mixing/stabilizing a chemical neutralizer into the effected soil
  4. Reclaiming land
  5. Water cover

Often the scope of many Construction projects mean minimising disturbance is not possible and therefore neutralisation is the only project management technique available. ASS are neutralised using lime, the amount of lime required is determined by analysing a sample of soil to calculate actual acidity and relating the amount of lime required to be added to effectively neutralise the soil.

Agricultural lime is commonly used and there are other liquid and powder reagents available such as hydrated lime, mixtures of hydrated lime and agricultural lime and also lime slurries.

As a specialist treatment contractor we provide the equipment and know-how to treat polluted and problem soils such a PASS (Potential Acid Sulphate Soil). We do this using a range of products and reagents. We are efficiently achieving this by having a through understanding of the technical requirements of treatment process, as well possessing state-of-the-art treatment equipment.

We neutralize ASS by using a machine we developed called the TERRAFORMA-300

acid sulphae soils

 The Terraforma-300 works by striping, and immediately treats the soils before it is affected.

The Department of Environment classification PASS (potential acid sulphate soils), vary in the potential probability of how toxicity is measured. Grading is graded low, med through to high. Detailed mapping is available to display this information.

Up until recently the Department of the Environment specified that PASS had to be back filled within 18 hours. They have now amended this directive to say that ASS have to be treated immediately.

Unlike other systems the TERRAFORMA-300 system treats the PASS immediately at first contact making the TERRAFORMA -3-00 the preferred system to surface mine PASS.


Main Office

Office: Trenchless
15 Dillington Pass Landsdale
Western Australia, 6027

email: jrj[at]
Phone: 0400 660 664

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BP demands a high level of performance in all aspects of projects. In addition to completing works effectively and efficiently, contractors must adhere to strict safety regulations; be able to adapt to sometimes difficult and challenging conditions; and conduct themselves in a professional and courteous manner.


Amcon We have found Trenchless Utilities to provide an efficient service as well as being well versed in project issues such as Health and Safety and Quality Control issues.

Reliance Industries

Reliance Industries Over the last two and one half years we have been getting to know Mr Johnson and his intrepid Trenchless team and they have done a marvelous job of teaching us how to use these 100+ HDD machinery, for the sake of your country men

Contact Information

Phone: (08) 6305 0093
Mobile: 0400 660 664
Office: 15 Dillington Pass, Landsdale
Western Australia, 6065

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Trenchless Utilities is Certified by CM3  for its safety systems which is assessed by GreencappNAA – one of Australia’s leading specialists in health and safety risk management

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