Before approving a development project regulated by legislation, an approval authority (for example, a municipality) may require an archaeological assessment of all lands that are part of the project.

Assessments are required when the land has either:

  • a known archaeological site
  • the potential to have archaeological sites

Archaeological assessments must be carried out by licensed archaeologists. We publish a list of all archaeologists licensed in Ontario.

Archaeological potential criteria

Areas of archaeological potential are areas of a property that could contain archaeological resources.

Non-specialists, such as approval authorities or development proponents, can use Ontario’s checklist for determining archaeological potential to help identify areas of archaeological potential on lands being developed.

What prompts an assessment

Here are some reasons that an archaeological assessment may be required:

  • Land development: for housing subdivisions and other land development projects, the approval authority under the Planning Act is usually the municipality where the new subdivision is located. The municipality will include the requirement for an archaeological assessment as one of the conditions for development approval. This is to make sure the developer meets their legal obligations under the Ontario Heritage Act.
  • Environmental assessments: public development projects such as hydro corridors, highways, or sewer construction take place under the Environmental Assessment Act directly or through a Class Environmental Assessment. In many cases, an environmental assessment determines the need for an archaeological assessment, which is then completed as part of the overall environmental assessment process.
  • Land use activities: such as quarrying, forest harvesting, pipeline installation and others.
  • Infrastructure Ontario: the Ontario government, through Infrastructure Ontario, has its own environmental assessment process, including archaeological assessment, for lands owned by the province.

Stages of an assessment

During the first three stages, the consultant archaeologist will:

  • discover any archaeological resources on the lands being developed
  • evaluate the cultural heritage value of any archaeological resources found on the property
  • recommend the most appropriate strategies for conserving archaeological sites prior to land development activities

The consultant archaeologist will recommend a fourth stage — mitigation of development impacts — where warranted.

Not all stages will be necessary for all projects.

Stage 1: background study and property inspection

The archaeologist determines whether there is potential for archaeological sites on the property.

They review geographic, land use and historical information for the property and the relevant surrounding area, visit the property to inspect its current condition and contact the ministry to find out if there are any known archaeological sites on or near the property.

A Stage 2 assessment is required when the consultant archaeologist identifies areas of archaeological potential.

Stage 2: property assessment

The archaeologist surveys the land to identify any archaeological resources on the property.

For a ploughed field, they will walk back and forth over it looking for artifacts on the surface. In forests, overgrown pasture areas or any other places that cannot be ploughed, they will dig parallel rows of small holes, called test pits, down to sterile subsoil at regular intervals and sift the soil to look for artifacts.

They may use other strategies if properties are paved, covered in fill or have deeply buried former topsoils (such as floodplains or former sand dunes).

The archaeologist will determine whether any archaeological resources found are of sufficient cultural heritage value or interest to require Stage 3 assessment.

Stage 3: site-specific assessment

The consultant archaeologist determines the dimensions of the archaeological site, evaluates its cultural heritage value or interest and, where necessary, makes recommendations for Stage 4 mitigation strategies.

To this end, they conduct further background research and fieldwork that expands the information gathered in Stage 2.

They map the spatial limits of a site and acquire further information about the site's characteristics by excavating one-metre by one-metre square test units across the site.

Based on circumstances, some sites (for example, ones that have been paved or are deeply buried) may require specialized methods of assessment.

The archaeologist will determine whether any archaeological sites have sufficient cultural heritage value or interest to require Stage 4 mitigation of development impacts.

Stage 4: mitigation of development impacts

This stage involves implementing conservation strategies for archaeological sites.

Determining the best approach for conserving the site may include reviewing possible strategies with the development proponent, the municipality or other approval authority, Indigenous communities, and other heritage stakeholders.

Conserving archaeological sites does not mean stopping development.

Conservation can involve putting long-term protection measures in place around an archaeological site to protect it intact. The site is then avoided while development proceeds around it. This is called protection in situ and is always the preferred option for mitigation of development impacts to a site.

If protection is not viable, mitigation can involve documenting and completely excavating an archaeological site before development takes place.

Long-term avoidance and protection

Unless long-term protection measures are in place, an archaeological site is not considered truly protected.

The archaeologist will recommend an avoidance and long-term protection strategy. Ontario's Heritage Tool Kit outlines long-term protection measures, such as:

  • restrictive covenants on title
  • zoning by-law amendments
  • the transfer of ownership to a municipality or other public land-holding body


If circumstances do not allow a site to be protected in situ, the site may be excavated before construction begins.

The purpose of excavation is to remove artifacts while documenting the site through measurements, maps, drawings and photographs.

Reporting after an assessment

After completing an archaeological assessment, the archaeologist submits a report to this ministry. We review the report to ensure:

  • the licensed archaeologist met the terms and conditions of their licence, including the ministry's requirements for fieldwork and reporting
  • any archaeological sites found were properly conserved