The term “Significant Impact" means substantial damage to the physical environment. Harmful changes to land, water, air, biological resources, wildlife, mineral resources, noise levels, and cultural resources are examples of physical impacts which are to be avoided whenever possible. Projects that substantially pollute the water supply, use prime farmland for nonagricultural purposes, cause substantial flooding, erosion, or affect rare and endangered species generally result in significant adverse impacts upon the environment. In some cases, generally accepted or adopted thresholds of significance are used.
If thresholds are exceeded, a determination of significant impact is made. Independent judgment and local circumstances also come into play in deciding whether a project may have the potential to cause substantial environmental harm. During the evaluation process, impacts will be assessed and quantified so that scientifically based findings of significant impact can be accurately reported. Sometimes, significant impacts are identified which can be eliminated or significantly reduced using various mitigation measures.