The term "significant impact" means substantial adverse damage to the physical environment. An initial study is prepared to assess a project's potential for causing environmental damage. The initial study will use the state's CEQA implementation guidelines which contain a list of the types of projects which generally cause environmental damage. Examples of projects on the state's list are any which: substantially pollute water supply; use prime farmland for non-agricultural purposes; or cause substantial flooding, erosion or siltation.
The CEQA analysis relies upon independent judgment to decide whether a project may have the potential to cause substantial environmental harm. The CEQA process also evaluates local circumstances not considered by the state when developing its impact list. Sometimes, significant impacts are identified which can be eliminated or significantly reduced using various strategies. In these cases, impact reduction strategies (mitigation measures) will be recommended rather than stating that expected damage is potentially significant.
If significant impacts are expected, an environmental impact report (EIR) will be required. During that process, damage will be assessed and quantified so that scientifically based findings of significant impact can be accurately reported.