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Investigate a site

Last updated on April 17, 2025

A site investigation helps you learn a property's history, find out if it is contaminated and if contamination has spread to other properties. Contaminants found in soil, water, vapour or sediment can be harmful to human health and the environment. 

Site investigation is an important step in cleaning up sites. It provides a foundation to begin cleaning up or managing contaminants.

For information about who is responsible for completing site investigation:

  • Consult the Environmental Management Act, Division 3– Liability for Remediation
  • Get advice from a qualified professional (QP) or environmental lawyer who is familiar with contaminated sites legislation

Determine if you need to conduct a site investigation

You must conduct a site investigation if: 

OR

  • A director of waste management has ordered you to complete one

You can do an investigation at any time for any reason, such as part of due diligence:

  • Before selling a property
  • If you suspect contaminants have moved to another property nearby
  • After a spill
  • If you need financing from a lender

Investigate a site to find out if it is contaminated

Preliminary site investigation

You must hire a Qualified Professional (QP) if you need to investigate a site and determine whether it's contaminated. A QP will start by conducting a Preliminary Site Investigation (PSI). A PSI is completed in 2 stages.

Stage 1

During this stage, a QP will:

  • Search existing records for information about a property, for example, by using the Site Registry or reviewing older municipal directories to determine the nature of previous businesses on the property
  • Interview people who have previously worked on, or owned, the property
  • Determine the areas at the property where contamination may have been introduced into the sub-surface (these are referred to as "Areas of Potential Environmental Concern" or "APECs" and the associated "Potential Contaminants of Concern" or "PCOCs")

Stage 2

During this stage, a QP will:

  • Conduct a field investigation to collect and analyze samples of soil, water, vapour or sediment to confirm if contamination is present
  • Identify the general location and degree of the contamination

The QP compares results from the investigation to numerical standards in the Contaminated Sites Regulation (CSR) to see if contaminants meet or are above acceptable levels.

If no contamination is present, you can apply for a determination that the site is not contaminated. If a QP discovers contamination during a PSI, they'll conduct a detailed site investigation to get more information.  

Detailed site investigation 

If needed, a QP will conduct a Detailed Site Investigation (DSI) by collecting additional samples of water, soil, vapour or sediment to confirm: 

  • The location, extent, and degree of the contamination

QPs can use this information to determine potential risks to humans and the environment and develop a remediation plan. 

A site investigation might uncover contamination migration. This is when substances from your property spread to a neighbouring property. If this happens, make sure you meet all requirements connected to contamination migration. 

Protocols and guidance for qualified professionals

This section provides protocols and guidance on how to conduct site investigations.

Protocols are legally required technical and administrative procedures. Guidance documents provide ministry expectations for undertaking the various aspects of site investigation but are not legally binding. 

For more information about legal requirements, review the Environmental Management Act and Contaminated Sites Regulation. 

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Protocols for site investigation

 

Guidance for site investigation

 

Contact information

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