An Environmental Impact Study (EIS) assesses how a proposed development will affect natural heritage features such as wetlands, woodlands, watercourses, and species habitat, and what buffers and mitigation are required. It is triggered when a site is on or adjacent to a natural feature or a conservation authority regulated area. It is prepared by an environmental consultant or biologist, is often tied to seasonal field surveys, and frequently establishes a development limit and buffer that reduces the buildable area.
The Environmental Impact Study is the study most likely to be governed by the calendar. Many of its field surveys, breeding birds, amphibians, rare plants, can only be done in specific seasonal windows. Miss the window and the study waits a full year, which is why an EIS discovered late is one of the most expensive scheduling mistakes in Ontario development.
An Environmental Impact Study evaluates the ecological features on and around a site, wetlands, woodlands, watercourses, significant wildlife habitat, and species at risk, and assesses whether and how the proposed development can proceed without unacceptable impact. It establishes the limits of development, required buffers, and mitigation or restoration measures.
The EIS is closely tied to conservation authority regulation and to provincial natural heritage policy. Where a Provincially Significant Wetland, a species at risk, or a regulated watercourse is present, the study must satisfy both the municipal official plan natural heritage policies and the conservation authority’s permitting requirements.
An Environmental Impact Study is triggered by proximity to a natural feature, including:
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Check my site →An Environmental Impact Study is prepared by an environmental consultant, typically an ecologist or biologist, often supported by specialists for species-at-risk or wetland delineation. Municipalities and conservation authorities expect the author to hold relevant professional standing and to have conducted field surveys in the correct seasonal windows.
A complete Environmental Impact Study typically contains:
| Factor | Typical range | What drives it |
|---|---|---|
| Consultant fee | $10,000 to $50,000+ | Feature complexity, species at risk surveys, and number of field seasons |
| Preparation time | Weeks to a full field season | Seasonal survey windows can force a wait of up to a year |
| Municipal review | Municipal and CA review, months | Circulation to commenting agencies and revision cycles |
The buffer an EIS establishes is removed from developable area and cannot usually be built on, so the study directly sets the effective site yield. Because surveys are seasonal, commission the EIS at the very start of the project or risk losing a construction year.
Requirements vary by watershed and by the natural heritage policies in each official plan. The Toronto and Region Conservation Authority, Credit Valley Conservation, Lake Simcoe Region Conservation Authority, and others each map regulated areas and apply their own buffer standards. Provincial layers, the Greenbelt Plan, Oak Ridges Moraine Conservation Plan, and Niagara Escarpment Plan, add further constraints where they apply, and a single site can fall under several regimes at once.
An Environmental Impact Study (EIS) assesses how a proposed development will affect natural heritage features such as wetlands, woodlands, watercourses, and species habitat, and what buffers and mitigation are required. It establishes the limits of development and is prepared by an environmental consultant or biologist, often based on seasonal field surveys.
An Environmental Impact Study is triggered when a site is on or adjacent to a natural feature or a conservation authority regulated area: wetlands, woodlands, watercourses, species-at-risk habitat, or a Natural Heritage System. Sites near the Greenbelt, Oak Ridges Moraine, or Niagara Escarpment frequently require one.
An Environmental Impact Study typically costs between $10,000 and $50,000 or more, driven by the complexity of the natural features, whether species-at-risk surveys are needed, and how many field seasons the work requires. Seasonal survey windows can significantly extend the timeline.
Much of the field work in an EIS, breeding-bird, amphibian, and rare-plant surveys, can only be done in specific seasonal windows. If the project starts after a window closes, the study may have to wait until the following year to complete those surveys, which is why an EIS should be commissioned at the very beginning of a project.
An Environmental Impact Study is reviewed by the municipality against its official plan natural heritage policies and by the conservation authority under its regulated-area permitting. Where provincial plans such as the Greenbelt or Oak Ridges Moraine apply, those policies add another layer of review.
PreBuildIQ identifies every required study, including the Environmental Impact Study, for any Ontario address in 60 seconds, with the trigger and terms of reference for your specific municipality.
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