While uploading documents to the Cubit NEPA Library, I researched 30 transportation EIS and EAs from various states that were published in 2009 or early 2010, focusing on the indirect impact section of the documents. The chart below shows what types of indirect impacts the documents discussed.
What I learned from my unscientific Indirect Impacts survey:
- Almost 100% of documents noted that the proposed project would indirectly impact land usage. Since the documents I studied were all transportation projects, this is not surprising.
- Traffic indirect impacts encompassed almost 70% of the researched documents. Again, the documents I studied were infrastructure projects so long-term traffic effects should be prevalent, but did not necessarily need mitigation.
- 47% of the documents addressed socioeconomic indirect effects. Perhaps the number of documents that were concerned with this issue wasn’t higher, because some proposed projects were in rural locations and not near existing residents.
- Water Resources, Wetlands, and Biological indirect impacts were prevalent in about the same percentage of documents. Maybe the percentages aren’t higher because some agencies encompassed these effects within the broader category of land use.
- A mere 13% of the documents addressed air quality as an indirect impact.
A Closer Look at the Indirect Impact Section:
The most ambiguous part of exploring possible indirect impacts is the requirement for the effects to be “reasonably foreseeable.” Even the guidelines for analyzing potential indirect impacts aren’t very clear. What if an area’s population grows dramatically within the next ten years, regardless of whether or not an improvement is made to an existing roadway? NEPA documents are supposed to address indirect impacts of all of the proposed alternatives, including the no-build alternative where no changes would be made. But after doing my research, I’ve discovered that some documents don’t separate the analysis of indirect and direct effects, or they just analyze direct and cumulative impacts without delving into studying indirect impacts separately. Perhaps because indirect impacts are very difficult to distinguish from direct impacts or already existing or future conditions, agencies don’t spend as much time analyzing them. In conclusion, indirect impacts are difficult to predict but must be addressed.