Section 106: Step Four

Section 106 of the National Historic Preservation Act requires a review of any Federal project that could potentially impact a historic property. There are four steps in the Section 106 compliance process. This page outlines how to complete Step Four of the process. There are similar separate pages for Step One, Step Two and Step Three. Be sure to check them out!


To complete STEP FOUR, answer this question:

If you have determined that the undertaking will have adverse effects on historic properties you need to notify the Advisory Council on Historic Preservation (ACHP) of the adverse effect finding by providing them with the same information that was submitted to SHPO/THPO in Step 3. In addition to notifying the ACHP of the adverse effect finding, the notice shall invite the ACHP to participate in the resolution of adverse effects when:

  • The agency official wants the ACHP to participate; and/or
  • The undertaking has an adverse effect upon a National Historic Landmark; and/or
  • A programmatic agreement will be prepared.

One of ACHP’s primary functions in the 106 process is to review federal and federally assisted, funded, licensed or approved undertakings after the project has been commented upon by SHPO and/or THPO. While the regulations require notifying the ACHP and inviting them to participate if certain criteria are met, the ACHP usually only gets involved in complex or controversial consultations. However, you must notify ACHP whenever an undertaking will adversely affect historic properties, and you must seek ACHP review in event of a disagreement with the SHPO/THPO.

The Advisory Council shall advise the agency and consulting parties whether it will participate within 15 days of receipt of the notice.

When adverse effects on historic properties cannot be avoided, some typical mitigation measures would be to:

When developing mitigation measures for adverse effects on historic properties, it is important to use the Secretary of Interior Standards for the Treatment of Historic Properties. The standards are intended to promote responsible preservation practices through four treatment approaches including preservation, rehabilitation, restoration, and reconstruction. It is a good idea to involve the SHPO/THPO and other consulting parties in the development of mitigation measures as you work on a Memorandum of Agreement.

Memorandum of Agreement

An adverse effect is usually resolved through the preparation of a memorandum of agreement (MOA).

The MOA outlines agreed-upon measures that the agency will take to avoid, minimize, or mitigate the adverse effects. If ACHP is not part of the consultation, then the MOA is executed between NPS and SHPO/THPO and filed with ACHP. When ACHP is involved in the consultations, the MOA is executed among NPS, SHPO/THPO, and ACHP. With the successful negotiation of an MOA, 106 compliance is complete and the park may proceed with the project.

Signatories to a MOA (usually at a minimum NPS, SHPO/THPO, and, if participating in the consultations, ACHP) contribute to the process or solution or have some responsibility under the MOA. Other consulting parties may be invited to sign and concur in the MOA, but only the signatories, including invited signatories, can amend or terminate the MOA.

If, after consultation, the NPS, SHPO/THPO, and the ACHP are not able to resolve Adverse Effects it may be determined that further consultation will not be productive and terminate consultation. Any party that terminates consultation shall notify the other consulting parties and provide them the reasons for termination in writing. If the agency terminates consultation, then it shall request Advisory Council comments, which the agency should consider before implementing the undertaking.

The ACHP offers a MOA Template

The ACHP offers guidance on agreement documents.


Advisory Council on Historic Preservation: The Advisory Council on Historic Preservation strives to ensure federal agencies implement their work in harmony with the National Historic Preservation Act. The ACHP has published regulations that guide federal agencies and other participants in the Section 106 process.
National Historic Landmark (NHL): A district, site, building, structure, landscape, or object of national historical significance designated by the Secretary of the Interior under authority of the Historic Sites Act of 1935 and entered in the National Register of Historic Places. These places are exceptional because of their abilities to illustrate U.S. heritage. Today, we have almost 2,600 NHLs in the United States.
Section 106 Agreement Document: A Memorandum of Agreement (MOA) or Programmatic Agreement (PA) is a legally binding document that commits an agency both by statute and by federal regulation to carry out the undertaking in accordance with the terms of the agreement in satisfaction of its responsibilities under Section 106. The MOA or PA serves three main purposes: (1) to specify the alternatives or mitigation agreed to by the signatories; (2) to identify who is responsible for carrying out the specified measures; and (3) to serve, along with its implementation, as evidence of the agency’s compliance with Section 106 of the NHPA.
Secretary of the Interior’s Standards and Guidelines: The Secretary of the Interior’s Standards for the Treatment of Historic Properties are common sense historic preservation principles in non-technical language. They promote historic preservation best practices that will help to protect our nation’s irreplaceable cultural resources..
Mitigation: Rectifying the impact by repairing, rehabilitating, or restoring the affected resource. Reducing or eliminating the impact over time by preservation and maintenance operations during the life of the action or compensating for the impact by replacing or providing substitute resources or environments (i.e., “off-site mitigation”).


Watch an interview with Jeff Durbin, National Section 106 Compliance Program Manager, as he explains Step Four of the 106 Process.

Audio Description Video for Step Four
Step Four Video Transcript

If there is a failure to agree, the ACHP comments, makes a decision and Section 106 Compliance is complete. If there is a resolution through MOA, then the Section 106 Compliance process is complete.

Write a Review

  1. Very good presentation and summation of the 106 process and its importance to historic preservation. I suggest this course be made mandatory as part of basic NPS training for all staff permanent and seasonal.


  2. Well done presentation of the 106 process and it’s importance to historic preservation. Having a real life example to educate the viewer really makes this a valuable learning lesson of the 106 process.

  3. This was a reasonable explanation as to what Section 106 is intended to do.
    It is good to know that there are processes in place to help protect our cultural resources.


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  5. So its not 100% clear what happened after the adverse effect? The ACHP did not engage, but what was the next step with the SHPO? It sounds like they wrote an MOA? What was the content of the MOA? Did they consider that roofs are essentially sacrificial and cyclic maintenance (replacing roofs) is a normal process for any building? Replacing in kind is the best way to go, and there are now asphalt shingles that last more than 5 or 15 years! OR they could modify the design to add another membrane layer under the shingles to increase the life of the roof. I think more discussion of the technical issues of heritage asset management would be helpful here.


  6. This series represents a good overview of the 106 process and helps me to better understand what parties should be involved and when. It also poses the 106 process as a functional process that is not as threatening or scary as some might make it out to be.


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  8. What an excellent example of the process – especially in regard to consultation and the weighing of potential determination of adverse effect vs alternative options of material, if appropriate.

  9. Great video series of Sec. 106 4-Step Process using the CCC shingled houses of VA Prince William Forest as a case study. I like especially liked J. Durbin’s presentation of how Adverse Effects” are handled and the possible involvement of the ACHP.

  10. Glad that the Park followed the appropriate S106 process. However, I question the claims of the shingles’ comparative lifespans and their use as the main argument for installing a composite shingle in lieu of historically appropriate wood. The lifespan of a cedar shingle roof can be up to 50 years with a good product, installed correctly, maintained periodically, and not in an extreme environment, such as marine. The comment in the video that a wood roof would need to be replaced “every 5 or 6 years” is perhaps derived from information provided by the composite shingle manufacturer, or is confused with asphalt shingle roofs, the cheaper versions of which do have a shorter lifespan than both cedar and composite.

    I am currently replacing a cedar shake roof that has lasted 45 years. I don’t know the composite shingle product they used but, unless recyclable again, if it contains any recycled plastic it will end up in a landfill in 50 years decomposing for a couple of centuries – green only in the short term. Finally, these “new technology” products have not been tested for as long as the traditional materials and the projected lifespans for composites (20-50 years) are less trustworthy than that for say cedar (30-50 years), which has been in use for centuries.


  11. Thanks for the informative video and reflection of the process. I would also reflect other people’s comments here on the final choice, as cedar shingles and other types of natural products can last just as long as the composite and are much easier to maintain, and lave a better life cycle than the composites. Though I understand that this learning space was about looking at the whole process, it may be better to include a more thought through case study.


  12. The Prince William Park case was an effective example of Adverse Effects and their mitigation. It was readily apparent that the newer “engineered material” was superior and met the overall goal of preservation of the property. The Park had done the right thing in finding an example of how it looked after it was aged, and arguably, it seems, that diminished the Adverse Effect over time for a win-win.


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  14. Again, very interesting. I think the selection of a real-world example that selected a design solution that resulted in a finding of adverse effect (that was mitigated, somehow) was a very smart move for a tutorial.

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