Detailed Site Investigation

Definition

A Detailed Site Investigation (DSI) is a comprehensive, intrusive site assessment that builds on the findings of a PSI. It involves soil, groundwater, surface water, or air sampling to confirm the presence, type, extent, and concentration of contamination. The results are compared against environmental guidelines to assess potential risks to human health and the environment.

Why It Matters

A DSI provides the factual, scientific basis for remediation planning and regulatory approvals. Without a DSI, contamination risks may remain undefined, delaying projects or leading to non-compliance. For developers and landowners, a DSI is the critical bridge between identifying a potential issue and implementing a targeted, cost-effective remediation strategy.

When It’s Required

• Following a PSI: When contamination is suspected or confirmed.
  
• Regulatory Compliance: To meet environmental protection authority (EPA) requirements.
  
• Remediation Planning: Before designing a Remediation Action Plan (RAP)‍
• Site Closure: As part of validation for previously remediated land.