Ontario's Environmental Assessment Act requires an environmental assessment of any major public sector undertaking that has the potential for significant environmental effects. This includes public roads, transit, wastewater and stormwater installations.
Environmental assessments determine the ecological, cultural, economic and social impact of the project. Environmental assessment is a key part of the planning process and must be completed before decisions are made to proceed on a project. The act does not apply to major private sector projects unless so designated by regulation.
The act exists to "provide for the protection, conservation, and wise management of Ontario's environment". The act mandates clear terms of reference, focused assessment hearings, ongoing consultation with all parties involved - including public consultation - and, if necessary, referral to mediation for decision.
The Environmental Assessment Act also establishes a "Class Environmental Assessment" process to streamline the planning of municipal projects - including some road, water, and sewage and stormwater projects.