Comprehensive Acid Sulfate Soil Assessments and Investigations - Sydney

Acid Sulfate Soils (ASS) — also written as acid sulphate soils — are a common trigger for Sydney councils where low-lying floodplains and estuaries occur, including around Botany Bay, Cooks River, Georges River, Parramatta River, and Sydney Harbour foreshore areas. If unmanaged, ASS can stall a Development Application (DA), complicate bulk earthworks, and increase construction costs.

Confluence Environmental provides Preliminary Acid Sulfate Soil Investigations, desktop reviews, and site-based assessments for development projects across Greater Sydney. Our DA-ready soil reports are practical, fast, and prepared in accordance with NSW EPA guidance and local council requirements.

Sydney Acid Sulfate Soil Assessment Services

Preliminary Investigation & Desktop Review

• Review of Sydney council Class 1–5 acid sulfate soil risk mapping.

• Section 10.7 Planning Certificate checks for ASS or contamination notations.

• Historic land use review, aerial photography, hydrology, and elevation modelling across Sydney’s estuarine floodplains.

• Identification of site-specific triggers for further investigation.

Field Investigation & Soil Testing – Sydney

• On-site site walkover and inspection by an experienced Sydney environmental consultant.

• Targeted boreholes/test pits in mapped or at-risk areas.

• Field screening: pH (field pHF), pH after oxidation (pHFOX), electrical conductivity (EC).

• Groundwater observations where relevant to proposed excavation depths.

• Laboratory analysis at a NATA-accredited facility:

  • SPOCAS suite (TAA, TPA, TSA, ANC).

  • CRS testing where required.

  • Acid Base Accounting (ABA/NAPP) for net acidity and lime demand.

Reporting & Risk Assessment

• Clear documentation of current Sydney site conditions and potential ASS sources.

• Identification of areas of environmental concern (AECs).

• Preliminary risk assessment of contaminant sources, pathways, and receptors.

• A concise conceptual site model (CSM).

• Recommendations on whether a management plan or Stage 2 detailed investigation is required.

When Will Sydney Councils Ask for an ASS Assessment?

You may be required to submit an acid sulfate soil assessment or preliminary investigation if:

• Your site is mapped in Class 1–5 ASS areas (e.g. Botany Bay, Parramatta River, Georges River, or Sydney Harbour floodplains).

• Proposed works involve excavation below the water table, trenching, dewatering, or bulk earthworks in mapped zones.

• Council issues a DA information request or condition requiring an Acid Sulfate Soil Management Plan (ASSMP).

Beyond Assessment – Management Plans & Dewatering

Where assessments confirm the presence of PASS or AASS, we also prepare:

• Acid Sulfate Soil Management Plans (ASSMPs): Construction-ready documents with excavation controls, lime treatment, monitoring, and verification.

• Dewatering Management Plans: Treatment train design (settlement → neutralisation → polishing), discharge criteria, monitoring programs, and NATA laboratory testing.

Learn more about Management Plans and Dewatering ➝

Why Choose Confluence Environmental in Sydney?

• Sydney-based consultants with proven experience in acid sulfate soil assessments for DAs across multiple councils.

• Trusted DA-ready reports that Sydney councils accept without back-and-forth.

• Complete service from desktop review to field investigation, soil testing, and management plans.

• Competitive pricing, clear scopes, and responsive turnaround.

📞 Call 0493 042 642 or request a fast quote for Acid Sulfate Soil Assessments, Investigations, and Soil Testing in Sydney, Botany Bay, Parramatta River, Georges River, and surrounding metropolitan areas.