Phase 2 Detailed Site Investigations (DSI)

At Atlas Engineering and Technology Group, our Phase 2 Detailed Site Investigations (DSI) provide the hard evidence you need to understand the nature and extent of contamination on your site through targeted sampling, laboratory analysis, and clear reporting.

Where a Phase 1 Preliminary Site Investigation identifies potential contamination, a Phase 2 DSI confirms whether contamination is actually present, how severe it is, and what it means for your project.

Our Sydney-based environmental team delivers rigorous investigations that support development approvals and remediation planning.

What Is a Phase 2 DSI?

A Phase 2 Detailed Site Investigation is an intrusive, quantitative assessment that tests the conclusions of a Phase 1 PSI. It involves the physical collection and laboratory analysis of soil, groundwater, soil vapour, and other media to determine:

  • Whether contamination is present.
  • What contaminants are present and at what concentrations.
  • Where contamination is located — horizontally and vertically.
  • How contamination may migrate and what risks it poses.
  • Whether the site is suitable for its intended use.

Our investigations are carried out in accordance with NSW EPA guidelines.

When Do You Need a DSI?

A Phase 2 DSI is required when:

  • A Phase 1 PSI has identified potential areas of environmental concern.
  • Council or the EPA requires confirmation of site condition as part of a development application.
  • A change of land use to a more sensitive purpose (e.g. residential, childcare, education) is proposed.
  • Known or suspected contamination must be quantified for remediation or management.
  • Due diligence for property transactions requires confirmation of environmental liabilities.
  • A validation baseline is needed prior to redevelopment or remediation.

Our Phase 2 DSI Process

1. Sampling & Analysis Plan (SAP)

Building on the conceptual site model from the Phase 1 PSI, we design a targeted sampling and analysis plan that addresses each potential area of environmental concern, defines sampling locations and depths, and identifies the appropriate analytical suite.

2. Intrusive Field Investigation

Our experienced field team undertakes intrusive works, which may include:

  • Soil sampling via hand augering, drilling, or test pitting.
  • Installation of groundwater monitoring wells and groundwater sampling.
  • Soil vapour and ground gas assessment.
  • Field screening using photoionisation detectors (PID) and other instruments.
  • Assessment for asbestos-containing materials.

All works are conducted with full chain-of-custody documentation to maintain sample integrity.

3. Accredited Laboratory Analysis

Samples are analysed at accredited laboratories for the relevant contaminants of potential concern, which may include:

  • Heavy metals.
  • Total recoverable hydrocarbons (TRH) and BTEX.
  • Polycyclic aromatic hydrocarbons (PAHs).
  • Organochlorine and organophosphorus pesticides (OCPs/OPPs).
  • Asbestos.
  • Per- and polyfluoroalkyl substances (PFAS).
  • Volatile and semi-volatile organic compounds.

4. Data Assessment & Conceptual Site Model Refinement

We compare results against the relevant NEPM health and ecological investigation and screening levels, refine the conceptual site model, and characterise the nature, extent, and risk of any contamination identified.

5. Reporting & Recommendations

We deliver a comprehensive, defensible DSI report that:

  • Documents the investigation methodology and findings.
  • Delineates the extent of contamination.
  • Assesses risks to human health and the environment.
  • Provides a professional opinion on site suitability for the proposed use.
  • Recommends remediation, management, or further assessment where required.

Possible Outcomes of a DSI

  • Site suitable for use: contamination is absent or within acceptable levels for the proposed land use.
  • Remediation or management required: a Remediation Action Plan (RAP) and/or further works are recommended to make the site suitable.
  • Further assessment needed: additional delineation or specialist assessment is recommended to fully characterise the site.

Why Choose Atlas Engineering and Technology Group?

  • Experienced Environmental Professionals Rigorous, evidence-based investigations aligned with NSW EPA requirements.
  • Integrated Expertise As a multidisciplinary group offering Geotechnical, Environmental, and Testing services, we combine intrusive investigation capability with in-house technical support.
  • NATA-Accredited Testing Reliable, legally robust analytical results.
  • Local Knowledge Sydney-based, with deep familiarity with NSW planning frameworks and regional geology and hydrogeology.
  • Defensible Reporting Reports prepared to withstand scrutiny from councils, the EPA, accredited site auditors, and other stakeholders.
  • Responsive Service We work to your project timelines to keep your development moving.

Related Services

  • Phase 1 Preliminary Site Investigations (PSI)
  • Remediation Action Plans (RAP)
  • Contaminated Land Remediation & Validation
  • Soil & Groundwater Sampling
  • Hazardous Materials Surveys
  • Waste Classification

Get in Touch

Need to confirm and quantify contamination on your site? Contact the environmental team at Atlas Engineering and Technology Group today to discuss your Phase 2 Detailed Site Investigation requirements and request a quote.