These apply to large, complex projects with the potential for significant impacts on the environment, such as major landfills. Proponents must prepare a Terms of Reference, which serves as a work plan to guide and focus the preparation of an environmental assessment. Environmental Assessments require approval from the Minister of the Environment and Cabinet under the Environmental Assessment Act.

Not all undertakings subject to the Environmental Assessment Act need to go through the individual environmental assessment process. Projects that are carried out routinely and have predictable and mitigable environmental effects may fall into groups or “classes” and therefore do not warrant an individual environmental assessment.

Ontario currently has 10 approved Class Environmental Assessments that cover routine activities related to such things as municipal road, sewage and water infrastructure, highway construction and maintenance, forest management activities, conservation authorities works and other public sector activities.

The environmental assessment rules for these types of projects are set out in the Electricity Projects Regulation, and vary depending on the environmental impacts and the type and size of the project.