In the process of issuing a dredge and fill permit under section 404 of the Clean Water Act, the US Army Corps of Engineers (Corps) prepared an Environmental Assessment (EA). It then issued a finding of no significant impact (FONSI) based on the EA. When a federal agency issues a FONSI, it does not need to prepare a more detailed Environmental Impact Statement (EIS).
Opponents of the permit sued, claiming the EA was inadequate and did not meet the legal criteria for issuing the FONSI. After the district (trial level) court rejected the challenge, the opponents appealed to the 5th Circuit, which determined the EA was inadequate and remanded and vacated the permit.

Cannot Use Checkboxes without Comment
The 5th Circuit said the EA was inadequate because the Corps used “checkboxes” in the EA without comment or analysis as to some aspects of the project.

Multiple Incremental Impacts May Have Significant Cumulative Impact
The 5th Circuit also clarified the terms “incremental impact” and “significant impact” when used in an EA. The Court said that although a single project’s impact may only be “incremental,” the cumulative impact of the project must still be considered along with “other past, present, and reasonably foreseeable actions.” The Court noted that the Corps has fielded over eighty permit applications in an area within three miles of this project. Even if all these other projects have only an incremental impact, the Corps must also examine if the cumulative impact of all of them may be “significant.”

On remand, the Corps must prepare an EA with sufficient evidence and analysis. Only then can the Corps (and a reviewing court) determine if an EIS is required.

To see the opinion https://www.ca5.uscourts.gov/opinions/unpub/22/22-30608.0.pdf