Detailed Site Investigation

Summary

A Detailed Site Investigation (DSI) is an intrusive environmental investigation undertaken to assess the nature, extent and significance of contamination at a site. A DSI builds on the findings of a Preliminary Site Investigation and involves targeted soil, groundwater, surface water or vapour sampling to inform risk assessment and decision-making.

DSIs are commonly required to support development applications, remediation planning and regulatory approvals where contamination is known or suspected.

Definition

A Detailed Site Investigation is a structured assessment that involves intrusive investigation, sampling and laboratory analysis to characterise contamination and assess risks to human health, the environment and proposed land use.

A DSI is typically designed to confirm the presence or absence of contaminants of concern, define their distribution and concentrations, and provide sufficient data to determine whether remediation or management is required.

Why Detailed Site Investigations Matter

From a risk management perspective, a DSI provides the data needed to move from identification of potential contamination to informed decision-making.

Without a DSI, contamination risks may be poorly defined, leading to uncertainty in planning approvals, inappropriate remediation strategies or unforeseen issues during construction. A properly scoped DSI allows risks to be assessed against relevant criteria and land-use scenarios.

DSIs also play a critical role in regulatory processes. Councils, regulators and auditors commonly rely on DSI findings when determining whether land is suitable for its intended use or whether remediation is required. Inadequate investigation can result in requests for further work, approval delays or rejection of reports.

For project delivery, a DSI helps inform earthworks planning, waste classification, groundwater management and remediation scope, reducing uncertainty and cost risk later in the project.

When a DSI Is Typically Required

A Detailed Site Investigation is commonly required where:

• A Preliminary Site Investigation has identified potential contamination

• Development or rezoning is proposed on land with a history of contaminating activities

• A change to a more sensitive land use is planned

• Contamination is identified during construction or excavation

• Regulatory authorities request detailed assessment to support approvals

DSIs are typically tailored to site-specific risks and proposed land use.

Typical Components of a DSI

While the scope varies depending on site conditions and regulatory requirements, a DSI commonly includes:

• Development of a sampling and analysis plan

• Intrusive soil, groundwater or vapour investigation

• Laboratory analysis of contaminants of concern

• Assessment of contaminant distribution and concentrations

• Human health and environmental risk assessment

• Recommendations regarding remediation or management

The investigation is designed to be proportionate to the level of risk.

Legislative and Regulatory Context

Detailed Site Investigations are undertaken in accordance with environmental protection legislation, planning requirements and recognised technical guidelines.

In New South Wales, DSIs are commonly required to support development applications under planning legislation and are assessed against EPA and industry guidance. Similar expectations apply in other Australian jurisdictions.

Regulators expect DSIs to be technically robust, transparent and clearly linked to risk assessment outcomes.

How We Can Help

Confluence Environmental undertakes Detailed Site Investigations as part of broader contaminated land and environmental assessment services.

Our DSI services typically include:

• Scoping and design of site-specific investigations

• Soil, groundwater and vapour sampling and assessment

• Risk-based interpretation of analytical results

• Clear reporting to support planning and regulatory review

• Integration of findings with remediation and validation strategies

We focus on delivering DSIs that are defensible, proportionate and aligned with approval pathways.

Related Terms and Concepts

• Contaminated Land

• Environmental Site Assessment

• Preliminary Site Investigation

• Remediation Action Plan

• Site Validation

• Waste Classification

• Groundwater Investigation

• Acid Sulfate Soils