Acid Sulfate Soils

Summary

Acid Sulfate Soils (ASS) are naturally occurring soils or sediments that contain sulphide minerals which, when disturbed, produce sulfuric acid that can damage land, water and infrastructure. Proper identification, investigation and management are critical for environmental consulting, land remediation and regulatory compliance in Australia.

Definition

Acid Sulfate Soils (ASS) are soils or sediments containing reduced inorganic sulphur compounds (e.g., iron sulfides) that, when exposed to air or drained, can oxidise and generate sulphuric acid, leading to adverse environmental and structural outcomes.

Why It Matters

In the field of Australian environmental consulting, land remediation and compliance, dealing with acid sulfate soils is vital for several key reasons:

• Environmental risk and liability: When ASS are disturbed—through excavation, dewatering, drainage or fill importation—the oxidation of sulphides can lead to acidification of soil and groundwater, release of heavy metals (such as aluminium, arsenic, cadmium), fish kills, ecosystem damage and deterioration of water quality.

• Infrastructure and land-use impacts: Acidic leachate from ASS can corrode concrete, steel and other infrastructure, compromise foundations, pits and walls, and create long-term maintenance and liability burdens. 

• Regulatory and compliance gateway: Many state jurisdictions (for example NSW Environment Protection Authority, WA’s Department of Water and Environment Regulation) require specific investigation, management and reporting when ASS are present or likely. 

• Integration with remediation and earthworks: For redevelopment, remediation or large earth-works projects, acid sulfate soil risk sits alongside contamination, geotechnical, groundwater and fill-reuse issues. Often it requires a dedicated investigation and management plan as part of broader services (for example through a Remediation Action Plan or Geotechnical Investigation).

• Cost-effectiveness and timely approvals: Early recognition and management of ASS risks prevent expensive remediation works, project delays, regulatory enforcement and unexpected costs.

When It’s Required

Knowing when acid sulfate soils must be considered is essential for planning, compliance and project delivery.

Common triggers

• Excavation, dewatering or drainage works in low-lying coastal, estuarine or floodplain settings where sulphidic materials may exist beneath shallow groundwater tables.

• Redevelopment of former marine/estuarine land or zones mapped for ASS (for example via the Atlas of Australian Acid Sulfate Soils or state-specific mapping). For example, WA planning guidelines require self-assessment and reporting when land is in “high to moderate” ASS risk zones.

• Bulk earthworks, changes to groundwater regime or imported fill that may expose or alter the oxidation state of sulfidic materials, leading to acid generation.

• Infrastructure or civil works that penetrate below the water table or disturb saturated sediments containing sulphides, such as piling, tunnelling or major drainage.

• Regulatory/approval conditions: Many development consents or infrastructure approvals include ASS investigation or management conditions. State guidelines (e.g., for NSW, QLD, SA) set out investigation and management thresholds.

Legislative & regulatory context

• In NSW, the Protection of the Environment Operations Act 1997 and associated guidelines direct management of ASS. 

• In Western Australia, the Environmental Protection Act 1986 and WA’s Planning Guidelines – Acid Sulfate Soils require submission of ASS investigations or management plans before site works. 

• Nationally, the National acid sulfate soils guidance: a synthesis document provides overarching frameworks and links to state manuals.

How We Can Help‍

At Nova Group Pacific, we deliver integrated environmental consulting services that support land remediation, development and approval workflows across Australia. Our acid sulfate soil (ASS) services are designed to identify, assess and manage risk early — ensuring compliance, protecting the environment and avoiding costly project delays.

Our support includes:

• Desktop risk screening & mapping: We review ASS-risk mapping and historical land-use to identify need for investigation early in your project lifecycle.

• Site investigation & sampling design: We design and oversee ASS investigations (including soil and groundwater sampling, sulphide/acid base accounting testing) in line with state-specific and national guidelines.

• Management plan development: If ASS is present or likely, we prepare a dedicated Acid Sulfate Soils Management Plan which links to remediation, design and monitoring strategies.

• Monitoring, validation & documentation: We assist with implementation of monitoring programs, verification of mitigation performance and preparation of regulatory-ready documentation.

• Integrated services: Our ASS work links with related services such as soil & waste classification, remediation action plans, geotechnical investigations and groundwater monitoring wells.

Managing acid sulfate soils effectively is more than a regulatory requirement — it safeguards land, water, infrastructure and future land use. Through early screening, robust investigation and integration with remediation and compliance frameworks, you can strengthen project outcomes and reduce risk.

Contact Nova Group Pacific today to address acid sulfate soil risks early, avoid delays and ensure alignment with best-practice environmental management from assessment to approval and beyond.

Related Terms and Concepts

• Soil & Waste Classification – classification of excavated materials; ASS disturbance often requires this classification.

• Geotechnical Investigation – subsurface investigations for earthworks and remediation, overlapping with ASS risk assessment.

• Groundwater Monitoring Wells – monitoring groundwater quality and levels; important when ASS may mobilise acid or metals into groundwater.

• Remediation Action Plan – when ASS impacts are identified, the remediation strategy may incorporate ASS management and material handling.

• Environmental Site Assessment (ESA) – umbrella environmental assessment that may identify ASS risks as part of broader land-use change or redevelopment.