Preparing Successful No-Effect and No-Adverse-Effect Section 106 Determinations: A Handbook for Transportation Cultural Resource Practitioners (2025)
Chapter: 5 Challenges Involving Indirect, Reasonably Foreseeable, and Cumulative Effects
CHAPTER 5
Challenges Involving Indirect, Reasonably Foreseeable, and Cumulative Effects
Challenge Summary
Respondents to the online survey and the follow-up interviews identified several challenges in identifying and applying indirect, reasonably foreseeable, and cumulative effects:
- Defining and identifying what are indirect and cumulative effects and the nature of these effects on different types of historic properties; for example, cumulative effects on linear resources such as historic roads and irrigation ditches or canals, where the project intersects with only small sections of the resource;
- Determining the time range for reasonably foreseeable effects and determining how far back cumulative effects should be considered;
- Determining the tipping point to reach a cumulative Adverse Effect; and
- Lack of understanding of some agencies, project proponents, and the public about these types of effects.
Here is a sample of some of the statements made by the online survey and interview respondents in relation to these challenges:
- “The severity of indirect effects is harder to gauge, and it can be more difficult to relate the impacts of the indirect effect to specific areas of integrity.”—SHPO Respondent
- “The aspects of integrity most often indirectly affected by projects (setting, feeling, and association) are more subjective and intangible than effects on materials, workmanship, and design. Cumulative effects are always a challenge; there are no guarantees that any action will have a definitive and quantifiable reaction.”—State DOT Respondent
- “Cumulative effects are very challenging because they can be nearly impossible to quantify, particularly if my agency is making changes to a setting or landscape that has already been altered by others (e.g., my agency is giving money to a local government for streetscape improvements, but that local government has already constructed a project or two to modernize elements of a historic streetscape). At what point is the work a cumulative Adverse Effect, and who gets left holding that bag? At what point is it death by a thousand cuts? How do you quantify whether moving heavy truck traffic off a historic main street will result in an economic loss and business closures versus perhaps creating a safer, ultimately more walkable, attractive, and vibrant downtown because heavy traffic has been moved? Unless we know of actual upcoming future projects, it can be hard to imagine potential future scenarios and then determine with any degree of accuracy if those scenarios could have a cumulative Adverse Effect.”—State DOT Respondent
Overcoming the Challenges
The online survey and follow-up interviews identified several approaches to addressing these challenges in the context of determining effects:
- To assess indirect effects, understand what people in a community value.
- Think about the long term and imagine what the area will look like 5 or 10 years after a project is built.
- Share with the SHPO and other consulting parties what the state DOT knows about future projects in an area and consider whether adding the current project to what is planned for the area may have a cumulative effect or lead to another finding.
- Provide consulting parties and the public with examples of similar projects, specifically, data showing results of certain types of impacts, such as vibration or audible effects from rock blasting.
One SHPO respondent described the following process developed to address projects affecting historic irrigation systems:
We have a memo for irrigation resources that if your project requires piping of an open canal and that section within your APE would become a noncontributing segment of the canal, that would be an Adverse Effect. We have that in place because we couldn’t wrap our heads around the cumulative effects of all the canal projects. So, we looked at it holistically and have every project that impacts the canal in a way that would be an Adverse Effect. You could almost apply the same concept to [historic] roads.
Two state DOTs discussed the construction of roundabouts and their potential to have a cumulative effect on historic roads. The challenge with assessing the cumulative effects was deciding when it was appropriate to make a finding of No Adverse Effect versus Adverse Effect. The state DOTs noted that, individually, a roundabout is not typically considered an Adverse Effect; however, a tipping point might eventually be reached when so many intersections were converted and a design element of the historic road was lost in the process (without ever having been considered an Adverse Effect in the past). To address these issues, the two state DOTs provided the following approaches:
- Use a holistic approach on the evaluation of effects on historic roads.
- Include procedures for assessing effects on linear resources in updates to statewide programmatic agreement.
- Complete statewide historic highway studies with National Register evaluations.
NCHRP Project 25-25/Task 43, “Guidance on Legal Sufficiency Criteria for Adequate Cumulative and Secondary Impacts Analysis in EIS Documents,” reviewed, analyzed, and documented materials needed to produce legal sufficiency criteria for state DOT practitioners on conducting analyses of indirect effects and cumulative impacts in the context of NEPA reviews. The study looked at federal and state guidance, published literature, court decisions, and environmental impact statements (EISs). The product of this study was a guide for state DOT practitioners and others involved in project development and review. The guide presents some approaches for addressing the challenges encountered in identifying and assessing indirect and cumulative impacts, which are instructive in the context of Section 106 reviews (Cambridge Systematics 2008). For example, in terms of both indirect and cumulative impacts, the guide provides the following, which mirrors some of the approaches used by Section 106 practitioners discussed earlier:
Proper scoping is one of the most important steps that practitioners can take in developing an indirect effects and cumulative impacts assessment methodology. This is important in order to be sure that everyone agrees on which resources need to be analyzed under [indirect effects and cumulative impact assessments]. This is an important opportunity to learn about any issues or concerns that may be specific to that area and to be sure that they are taken into consideration and discussed thoroughly upfront to minimize the possibility of disagreements on methodology. Resource agencies have important information to add to the methodology at this point in the process and their knowledge should be utilized to help determine resources and define a study area that is appropriate. Complete collaboration is one of the best ways to be sure that all possible issues have been considered, and to minimize the likelihood of disagreements as early as possible in the process. Documenting the results of this collaboration and coordination is of the utmost importance. (Cambridge Systematics 2008)
The guide also provides some detailed approaches for identifying and measuring cumulative impacts:
The future analysis year used in the cumulative impact assessment should have a logical basis, such as the future year used for regional transportation and land use plans. The future analysis year should be the same as the indirect effects assessment for clarity. Some cumulative impact assessments establish an explicit analysis timeframe for examining “past actions.” A formal historical temporal boundary is not strictly necessary based on case law, as long as the discussion of resource trends summarizes the important effects of past actions on the health of each resource. If it is decided to establish a formal timeframe for looking at past actions, the timeframe should be at least 10 years and be based on a development event that was important in shaping the current land use of the study area (e.g., opening of major regional employer, major transportation project, or other turning point). (Cambridge Systematics 2008)
“Attachment A: Definitions and Translations” in CEQ and ACHP’s NEPA and NHPA: A Handbook for Integrating NEPA and Section 106 begins with the following statement:
The Advisory Council on Historic Preservation (ACHP) advises Federal agencies to coordinate compliance with Section 106 of the National Historic Preservation Act (NHPA) and the procedures in the regulations implementing Section 106, “Protection of Historic Properties” (36 C.F.R. Part 800), with steps taken to meet the requirements of the National Environmental Policy Act (NEPA). The ACHP recommends that participants in the Section 106 process and NEPA practitioners familiarize themselves with the vocabulary of the two processes in order to better understand the relationship between the requirements and to realize opportunities to avoid unnecessary duplication of effort. (CEQ and ACHP 2013)
CEQ and ACHP also state, in the introduction to the handbook, that it is “intended to help practitioners take advantage of opportunities to coordinate NEPA and Section 106 compliance procedures to improve environmental reviews.” The highlighted overlap and similarities concerning approaches to address the challenges associated with indirect, reasonably foreseeable, and cumulative effects reinforce the value of such coordination among NEPA and Section 106 practitioners. Furthermore, this coordination includes outreach, engagement, and consultation with Section 106 consulting parties, NEPA stakeholders, and members of the public.
