Extraordinary circumstances are unique situations presented by specific proposals, such as characteristics of the geographic area affected by the proposal, scientific controversy about the environmental effects of the proposal, uncertain effects or effects involving unique or unknown risks, and unresolved conflicts concerning alternate uses of available resources within the meaning of section 102(2)(E) of NEPA. In the event of extraordinary circumstances, a normally excluded action will be the subject of an additional environmental review by the Agency to determine the potential of the Agency action to cause any significant adverse environmental effect, and could, at the Agency's sole discretion, require an EA or an EIS, prepared in accordance with subparts C or D of this part, respectively.

Significant adverse environmental effects that the Agency considers to be extraordinary circumstances include, but are not limited to:

Any violation of applicable Federal, state, or local statutory, regulatory, or permit requirements for environment, safety, and health.

Siting, construction, or major expansion of Resource Conservation and Recovery Act permitted waste storage, disposal, recovery, or treatment facilities (including incinerators), even if the proposal includes categorically excluded waste storage, disposal, recovery, or treatment actions.

Any proposal that is likely to cause uncontrolled or unpermitted releases of hazardous substances, pollutants, contaminants, or petroleum and natural gas products.

An adverse effect on the following environmental resources:

Historic properties;

Federally listed threatened or endangered species, critical habitat, Federally proposed or candidate species;

Wetlands (Those actions that propose to convert or propose new construction in wetlands will require consideration of alternatives to avoid adverse effects and unwarranted conversions of wetlands. For actions involving linear utility infrastructure where utilities are proposed to be installed in existing, previously disturbed rights-of-way or that are authorized under applicable Clean Water Act, Section 404 nationwide permits will not require the consideration of alternatives. Those actions that require Section 404 individual permits would create an extraordinary circumstance);

Floodplains (those actions that introduce fill or structures into a floodplain or propose substantial improvements to structures within a floodplain will require consideration of alternatives to avoid adverse effects and incompatible development in floodplains. Actions that do not adversely affect the hydrologic character of a floodplain, such as buried utility lines or subsurface pump stations, would not create an extraordinary circumstance; or purchase of existing structures within the floodplain will not create an extraordinary circumstance but may require consideration of alternatives to avoid adverse effects and incompatible development in floodplains when determined appropriate by the Agency);

Areas having formal Federal or state designations such as wilderness areas, parks, or wildlife refuges; wild and scenic rivers; or marine sanctuaries;

Special sources of water (such as sole source aquifers, wellhead protection areas, and other water sources that are vital in a region);

Coastal barrier resources or, unless exempt, coastal zone management areas; and

Coral reefs.

The existence of controversy based on effects to the human environment brought to the Agency's attention by a Federal, tribal, state, or local government agency.