Assignment Task:
First, go to the U.S. Environmental Protection Agency (EPA) website on the National Environmental Policy Act (NEPA) and skim it, paying particular attention to the section about Categorical Exclusion (CE) under the "The NEPA Process" section.
Then do a web search on the terms "categorical exclusion." Then you might want to add "NEPA" and any agency that you are interested in, since you now know that each agency deals with CEs differently. Some examples of agencies might be: Bureau of Land Management, Forest Service, Department of Energy, Department of the Army, any state Department of Transportation, and many, many others! You are looking for information regarding how that agency tends to use CEs and at least one case where they have been applied.
Summarize in a detailed post what you have learned. Be sure to tell us what agency you picked, outline their CE policy, and detail a specific case where they applied it. Does the case you found where they were used seem appropriate or not? If you had been the regulator in charge would you have applied CE in this case?