Acid Sulfate Soil Management

Earth Systems provides specialist expertise in the management of acid sulfate soil (ASS) and related water quality issues. From identification and characterisation of high-risk soil types and environments, through to prevention, control and treatment, Earth Systems has been providing solutions for ASS-related issues on varying scales to a diverse range of clients for almost 20 years.

Acid sulfate soil (ASS) forms naturally in both coastal and inland settings under highly reducing conditions in saturated organic-rich sediments where there is a source of sulfate and iron.
In these sediments, microbally mitigated sulfate reduction results in the formation of iron sulfides, including pyrite (FeS2).
When exposed to air, either by natural means (lowering water table, drought, seasonal evaporation, erosion) or anthropogenic activity (development/excavation, agriculture, drainage development), the iron sulfides oxidise, resulting in low pH (acid) drainage and the formation of secondary iron-rich oxides, hydroxides and sulfate salts. Without appropriate management, ASS has the potential for significant environmental, human health and economic impacts, including:

  • soil acidification;
  • acid (low pH) and metalliferous drainage;
  • toxic H2S, SO2 and volatile organic sulfur compound emissions;
  • infrastructure corrosion (steel and concrete structures); and
  • reduced agriculture and aquaculture productivity.

Services Provided

Part of a satellite image used by Earth Systems to assist in preparation of an EMP for a major mining project.

Regulators and mine operators are now developing a better understanding of the impacts of AMD on the environment, infrastructure and the short- and long-term viability of mining operations. Accurate identification, characterisation and prediction of AMD is essential to understand and manage AMD risks and to develop appropriate prevention, control and, if necessary, treatment options for both short- and long-term mine management. Significant advances have been made over the past decade in our understanding of AMD and the ways in which it can be managed.
Earth Systems provides specialist expertise in all aspects of the iden­tification, characterisation, prevention, management and treatment of ASS and the associated acid and metalliferous drainage, including:

  • ASS audits, including ASS risk assessment and management system audits throughout all phases of project development.
  • Baseline studies and impact assessments associated with the disturbance/dewatering of ASS and potential acid generation.
  • Development of rehabilitation strategies.
  • Development of comprehensive site-specific ASS manage¬≠ment, prevention and monitoring strategies that can be inte¬≠grated with existing development or rehabilitation planning.
  • Identification, geochemical characterisation and classification of soils, including static and kinetic geochemical testwork, sulfur chemistry/speciation and acidity generation rate deter¬≠mination (OxCon testwork).
  • Water quality assessment and monitoring, including sampling protocols, total acidity and acidity load assessment, analytical data assessment and treatment reagent requirements.
  • Computer-based modelling and assessment of ASS potential including site water balances, acidity/contaminant load bal¬≠ances and geochemical equilibrium modelling.
  • Design/implementation of site-specific ASS prevention, con¬≠trol and treatment strategies, including contract treatment options.
  • Leading-practice environmental training workshops for regula¬≠tors, managers, supervisors and operators on ASS management.

Project Experience

  • Key authors for the Australian Federal government‚Äôs Managing AMD handbook.
  • Technical input into the Victorian government‚Äôs ASS Policy.
  • Identification, characterisation, prediction and management of ASS at sites throughout Australia and southeast Asia.
  • Provision of ASS services to a major port infrastructure project.
  • Provision of ASS services to the agricultural sector, including ASS management strategies for a 50,000 ha sugar cane planta¬≠tion in Eastern Sumatra.
  • Provision of ASS services to governments and authorities to assist with the management of acid drainage, including the environmentally sensitive Mekong Delta, Vietnam and Lower Lakes & Lower Murray Regional Irrigation Authority, South Australia.
  • Development of software tools to facilitate ASS management (eg. AMD Audit, ABATES, AMDact).
  • Development of the OxCon method, a, kinetic geochemical test for quantifying sulfide oxidation and acidity generation rates.
  • Design, construction and installation of passive and active treatment systems for ASS sites in the mining, agriculture, industry and infrastructure/urban development sectors.

For more information or to discuss our range of environmental Management and Assessment services please contact Earth Systems at [email protected]

Recent News

Report for The International Network for Acid Prevention

26 May 2020

Earth Systems in collaboration with Okane Consultants, released a report providing new insight into ensuring low polluting mine operations, and more successful mine closure outcomes.

The report reviews conventional mine rock stockpile construction methods, and summarises improved construction technologies that are available to help improve water quality from mine wastes. Continued efforts to implement these technologies will help quantify their environmental and economic benefits.


Earth Systems Melbourne Office
4/290 Salmon Street                         Port Melbourne, VIC 3207                 Australia

Tel: +61 (0) 3 9810 7500
Fax: +61 (0) 3 9853 5030
[email protected]