The National Historic Preservation Act (NHPA) is the cornerstone of historic preservation at the Federal level in the United States. The law establishes a Federal policy of stewardship of historic places, explaining that “the spirit and direction of the Nation are founded upon and reflected in our historic heritage,” and that this heritage should be preserved as part of our community life. The Act goes on to state that the preservation of this irreplaceable heritage is in the public interest and there must be mechanisms in place to preserve this heritage in the face of development and growth, particularly when they are linked to federal actions.

The NHPA clearly states that Congress’s primary objective is to achieve a balance between historic preservation and development.

It shall be the policy of the Federal Government … to … use measures, including financial and technical assistance, to foster conditions under which our modern society and our prehistoric and historic resources can exist in productive harmony …. (National Historic Preservation Act, Section 2)

Compliance with Section 106 of NHPA is a critical requirement of Federal transportation projects. This section of the law, as its implementing regulation, 36 CFR 800, notes, “seeks to accommodate historic preservation concerns with the needs of Federal undertakings through consultation among the agency official and other parties with an interest in the effects of the undertaking on historic properties….” (36 CFR 800.1(a))

As can be seen in this quote from the regulation, consultation is at the heart of the Section 106 process. Consultation is a “process of seeking, discussing, and considering the views of other participants, and, where feasible, seeking agreement with them regarding matters arising in the section 106 process” (36 CFR 800.16(f).

In addition to the NHPA, there are other important laws and regulations that address historic preservation issues and federal projects. These include:

    • Section 4(f) of the U.S. Department of Transportation Act
    • National Environmental Policy Act of 1969 (NEPA)
    • Archaeological Resources Protection Act of 1979 (ARPA)
    • Native American Graves Protection and Repatriation Act of 1990 (NAGPRA)

Information on the National Environmental Policy Act can be found in the NEPA Process section of this website. Section 4(f) of the U.S. Department of Transportation Act and its relationship with Section 106 is briefly described below. ARPA and NAGPRA, for the most part, apply to actions on federal and tribal lands. Transportation projects located on federal or tribal lands, therefore, must comply with these laws and their implementing regulations. Information on these two latter laws is provided in the ARPA regulation and the NAGPRA regulation.

Section 106 of the National Historic Preservation Act

Section 106 requires federal agencies to take into account the effects of their undertakings on historic properties and afford the Advisory Council on Historic Preservation (ACHP) an opportunity to comment on the effects of the undertaking. The regulation implementing Section 106 of NHPA is 36 CFR 800. The outcome of the Section 106 process, as laid out in the regulation, is not predetermined. Rather, it is the interaction among the participants involved in this consultative process that determines the outcome, although the final decisions are made by the Federal agency.

Undertakings requiring compliance with Section 106 include projects and programs that are funded, permitted, licensed, or authorized by a federal agency, both on and off federal lands. Historic properties are sites, buildings, districts, structures, or objects listed in or eligible for listing in the National Register of Historic Places. The National Register is used as the standard for defining those historic places worthy of preservation and protection. These historic places include archeological sites, bridges and roads, buildings, designed landscapes such as parks, and places of religious and cultural significance to Native American tribes, Native Hawaiian organizations, and other traditional communities.

The Advisory Council on Historic Preservation is an independent federal agency that advises the President and Congress on historic preservation matters, encourages the preservation of historic properties through review of federal agency programs and projects, and promotes the preservation of historic properties by providing training, developing guidance, and assisting the public. The ACHP also has the authority to issue regulations for Section 106 compliance.

Participants in the Section 106 Process

Federal agencies are at the center of the Section 106 process. They have the responsibility under the law and the regulation for ensuring that the Section 106 compliance process is completed. For projects involving multiple Federal agencies, one agency often will serve as the “lead” Federal agency, taking responsibility for Section 106 compliance and consulting with the other agencies as needed. For highway projects, this is generally the Federal Highway Administration (FHWA), with much of the day-to-day work being conducted by transportation agencies. Even though they delegate the day-to-day work to transportation agencies, FHWA has the responsibility for carrying out the Section 106 process and the authority to make all decisions. FHWA can only assign its responsibility and authority to a state following the assumption of responsibility provisions established in Sections 6004 and 6005 of the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU) and the Moving Ahead for Progress in the 21st Century Act (MAP-21). However, the FHWA cannot delegate government-to-government consultation with tribes.

The Advisory Council on Historic Preservation participates in the Section 106 process based on the criteria in Appendix A of 36 CFR 800. The ACHP generally participates in the process when the undertaking will have substantial impacts on important historic properties, will be highly controversial, or will have issues of concern to tribes and Native Hawaiian organizations. In addition, the Federal agency requests the ACHP to participate in the Section 106 consultation process when an undertaking will adversely affect a National Historic Landmark.

The other participants in the Section 106 process are referred to as consulting parties. These include State Historic Preservation Officers (SHPOs), who serve as the state’s representative in the process, and Tribal Historic Preservation Officers (THPOs), tribal officials approved by the National Park Service to fulfill the role of the SHPO on tribal lands. When an undertaking is on tribal lands, the federal agency consults with the THPO, and if a tribe has no THPO, the agency consults with a designated tribal representative and the appropriate SHPO. For undertakings off tribal lands, the agency consults with all federally-recognized tribes and Native Hawaiian organizations that attach religious and cultural significance to properties that may be affected by the undertaking.

Additional consulting parties include, but are not limited to, local governments, applicants for federal funds permits or licenses, and individuals and organizations with a demonstrated legal or economic interest in, or concern about historic properties that may be affected by the undertaking. The agency also has an obligation to inform and involve the public. Transportation agencies are generally involved in the Section 106 process as applicants for federal funds, permits, or approvals. Even though the FHWA may formally delegate their day-to-day Section 106 compliance activities to the transportation and other agencies, the latter is still considered a consulting party under the Section 106 process.

The Basic Steps in the Section 106 Process

The Section 106 process consists of four steps. In Step 1, the agency initiates the Section 106 process by first determining if its action is an undertaking that falls under the purview of Section 106, and whether or not the action has the potential to affect historic properties. If the action is an undertaking that has the potential to affect historic properties, then the agency initiates consultation with the appropriate SHPO, THPO (if appropriate) and other consulting parties.

The second step involves the identification of historic properties within a project’s area of potential effects (APE). An APE is the area within which a project may directly or indirectly cause changes in the character or use of historic properties, if such properties exist. Since many properties have not been identified and evaluated for National Register listing, agencies must make a reasonable and good faith effort to identify such properties within the APE and then evaluate their eligibility for listing in the National Register. When an unevaluated property is found, the agency evaluates the property using the processes established in 36 CFR 60 and National Register Bulletin 15 to determine whether the property meets the criteria of eligibility and has sufficient integrity to convey its historic significance.

The agency requests the concurrence of the State Historic Preservation Officer (or Tribal Historic Preservation Officer if the property is on tribal lands) with the agency’s evaluation, and if the SHPO or THPO concurs, the property is treated, for the purposes of Section 106, as eligible for listing in the National Register.If no historic properties are found in the APE or if properties are found but the project will not affect the properties, the agency makes a finding of no historic properties affected. This formal finding is made in consultation with the Section 106 consulting parties. A finding of no historic properties affected completes the Section 106 process.

If there are historic properties within the APE and the agency determines that its project may affect one or more of these properties, the federal agency evaluates the nature of these effects and determines whether or not the effect is adverse. The evaluation of adverse effects is step three in the Section 106 process, and as with all steps in the process, is completed in consultation with the consulting parties, particularly the SHPO and/or THPO. The agency determines whether its project will diminish those qualities that make any of the properties eligible for listing in the National Register. If the project will diminish these qualities in one or more properties, the agency makes a finding of adverse effect; if not, the agency makes a finding of no adverse effect. A finding of no adverse effect completes the Section 106 process.

If the agency finds there will be an adverse effect, it must complete step four, in which the agency works with the Section 106 consulting parties to resolve the adverse effects on historic properties. Resolution of adverse effects may involve redesigning a project to avoid or minimize impacts to properties. If avoidance is not possible, then the agency will implement actions to mitigate these impacts. Actions that the parties agree upon to resolve adverse effects are codified in a Memorandum of Agreement (MOA), which is a legally binding agreement among the federal agency, the SHPO and/or THPO, and the ACHP. The other consulting parties may also be invited to sign the document. Once the agreement is signed by all appropriate parties and the agreement is filed with the ACHP, the Section 106 process is completed. The agency’s Section 106 responsibilities are fulfilled when the MOA’s stipulations are implemented.

Flexibility in the Section 106 Process

Creative Mitigation

As noted above, the outcome of the Section 106 process is not predetermined. It is the interaction among the participants involved in this consultative process that determines the outcome (with the Federal agency making the final decision). As a result, there are many opportunities for creative and innovative approaches to fulfilling the requirements of Section 106. This is especially the case in resolving adverse effects.

Resolution of adverse effects is often treated as a mechanical process, using well-established, standard approaches such as archaeological data recovery (i.e. archaeological excavations) or photographing and documenting a historic building that will be destroyed as a result of an undertaking. Several state FHWA offices, transportation agencies, and SHPOs, however, are using non-standard, innovative approaches to resolving adverse effects. These approaches are often referred to as creative mitigation. Creative mitigation can result in better project and historic preservation outcomes, and has greater public benefit than standard approaches. Examples of creative mitigation include assisting in the development of local historic preservation plans and ordinances, developing educational materials and web sites, purchasing properties containing historic properties, or developing historic property management plans as a supplement to, or even in lieu of, standard mitigation.

Section 106 Program Alternatives

The four basic steps described in the previous section are the standard approach to Section 106 compliance. The ACHP’s regulation, however, allows Federal agencies to fulfill their Section 106 responsibilities through a variety of alternative approaches. These approaches are described in 36 CFR 800.14. FHWA has used two of these alternative approaches: programmatic agreements and exempted categories of undertakings.

Programmatic agreements (PAs) can be used to establish to establish a custom-designed Section 106 process for an agency program, for common types of undertakings (such as routine maintenance), and when a category or group of projects results in similar and repetitive effects on historic properties. PAs replace case-by-case Section 106 consultation and compliance with a programmatic approach. PAs are negotiated between the ACHP and Federal agency in consultation with SHPO(s), tribes, and other agencies. Public involvement is included as part of the development of these PAs.

A PA might, for example, provide a list of agency actions that are excluded from any additional Section 106 review because these actions have been repeatedly demonstrated to have no effect on historic properties. This type of PA is often referred to as a “minor projects PA.” A PA can also establish a standard treatment for dealing with historic properties that are repeatedly encountered during an agency’s undertakings, such as historical archaeological sites of a specific type and time period.

State FHWA division offices and transportation agencies have developed a wide variety of state-specific PAs. These range from PAs listing minor projects excluded from additional Section 106 review to PAs that delegate the majority of SHPO review authority (as delineated in 36 CFR 800.4 to 800.6) to the state DOT. Examples of these PAs can be found in the Center for Environmental Excellence’s Programmatic Agreements Library and Programmatic Agreement Toolkit.

Interstate Highway Exemption

As the Interstate System approached its 50th anniversary (2006), transportation and historic preservation officials realized that the system could be determined eligible for listing in the National Register, and thus subject to the requirements of Section 106, in addition to Section 4(f). As a result, federal transportation agencies would have to assess the affects of a large number of actions, involving all components of the Interstate. In March 2005, the ACHP, working with FHWA, approved an exemption that relieves Federal agencies from taking into account the effects of their actions on the Interstate Highway System. The ACHP Exemption Regarding Historic Preservation Review Process for Effects to the Interstate Highway System excludes certain individual elements and structures of the system that are already listed or already determined eligible for listing in the National Register, and elements and structures that have national or exceptional significance. FHWA also developed a state-by-state list of elements and structures of national or exceptional significance.

The exemption also states that “[e]ach Federal agency remains responsible for considering the effects of its undertakings on other historic properties that are not components of the Interstate Highway System (e.g., adjacent historic properties or archaeological sites that may lie within undisturbed areas of the right of way)…”

SAFETEA-LU (Section 6007) also exempts the majority of the Interstate Highway System from consideration as an historic site under Section 4(f) of the Department of Transportation Act. Section 4(f) will still apply to individual elements and structures of the system that are already listed or already determined eligible for listing in the National Register, and elements and structures that have national or exceptional significance. Additional information is available in FHWA’s Interstate Highway Exemption Guidance.

Additional Information on Section 106

For additional information, please see Section 106 Section on the ACHP website and the Center for Environmental Excellence by AASHTO’s Practitioner’s Handbook, Consulting Under Section 106 of the National Historic Preservation Act.

Section 4(f) of the Department of Transportation Act

Section 4(f) of the Department of Transportation Act includes provisions prohibiting the FHWA and other federal transportation agencies from using land from a historic site of national, state, or local significance (in addition to publicly owned parks, recreation areas, and wildlife and water fowl refuges) unless there is no feasible and prudent alternative to the use of this land, and the action includes all possible planning to minimize harm to the property, resulting from this use. FHWA policy defines an historic site as a property listed in or eligible for listing in the National Register of Historic Places. Section 4(f) applies to archeological sites that are on or eligible for the National Register and that warrant preservation in place, including those sites discovered during construction. Section 4(f) does not apply if FHWA determines, after consultation with the SHPO/THPO, that the archeological resource is important chiefly because of what can be learned by data recovery and has minimal value for preservation in place. The decision on eligibility and significance is made in consultation with the appropriate SHPO and/or THPO.

When a transportation project permanently incorporates land from an historic property, Section 4(f) applies, even if there is a no adverse effect finding under Section 106. Section 4(f) requirements are satisfied, however, if the impact to the historic property is found to be de minimis (see below). If a project does not incorporate land of a historic property but results in an adverse effect finding, FHWA assesses the proximity impacts of the project to determine if there is a constructive use. For a constructive use to occur on a historic property, the features or attributes that contribute to the National Register eligibility of the property must be substantially impaired (i.e., as noted in FHWA’s Section 4(f) Policy Paper, “…the value of the resource in terms of its of its Section 4(f) significance will be meaningfully reduced or lost. . . constructive use determinations will be rare”).

FHWA policy states that when there is a use of a historic property, plans to minimize harm usually consist of measures that resolve a project’s adverse effect, as defined under the Section 106 regulation. These measures are agreed upon by the FHWA, SHPO and/or THPO, the transportation agency, and if they are participating in the Section 106 consultation, by the Advisory Council on Historic Preservation.

FHWA has established nationwide programmatic Section 4(f) evaluations as an alternative to preparing individual evaluations. Programmatic evaluations streamline the documentation, approval process, and interagency coordination. Two of the nationwide programmatic Section 4(f) evaluations deal explicitly with historic properties. One covers minor involvements with historic properties, the second, use of historic bridges. Links to these two programmatic evaluations are provided below.

SAFETEA-LU amended Section 4(f), allowing the requirements of this statute to be satisfied by making a determination of de minimis impact. For historic properties, the de minimis criteria are defined as “no adverse effect” or “no historic properties affected” findings as defined in 36 CFR 800. Prior to making a de minimis impact determination, FHWA must consult with the consulting parties on these Section 106 findings, and must have written agreement with the findings from the appropriate SHPO and/or THPO. FHWA must also inform the SHPO or THPO (and the ACHP if it is participating) of its intent to make a de minimis impact determination based on their concurrence with the no adverse effect or no historic properties affected findings.

For additional information, link to AASHTO Practitioners Handbook #11: Complying with Section 4(f) of the U.S. DOT Act. In addition, link to FHWA’s Section 4(f) pageSection 4(f) Policy Paper and Tutorial.

Section 6(f) Land and Water Conservation Fund Act

The Land and Water Conservation Fund Act (LWCFA) of 1965 (16 USC 4601-4 et seq.) was enacted to establish a funding source to assist the States and Federal agencies in meeting present and future outdoor recreation demands and needs. Federal assistance (funding) from the act is authorized to the States for the planning, acquisition, and/or development of needed land and water resources or utilized, directly, by Federal agencies for the acquisition and development of “certain lands.” Text of the LWCF Act and the associated regulations at 36 CFR Part 59.1 can be found at

The LWCF Act is administered by the Department of the Interior (DOI)/National Park Service (NPS) which, in turn, delegates many of the roles and responsibilities to a department within each state, whose Secretary then serves as the State Liaison Officer.

Section 6(f) of the act requires that all properties “acquired or developed, either partially or wholly, with LWCF funds” must be maintained as such in perpetuity. Section 6(f)(3) states that those properties acquired or developed with LWCF funds shall not be converted to a use other than public outdoor recreation without the approval of the Secretary of the DOI, acting through the National Park Service and at the request of the state delegate/State Liaison Officer.

Section 6(f) of the Act prohibits the conversion of property acquired or developed with LWCF grants to a non-recreational purpose without the approval of the Department of the Interior’s National Park Service. Section 6(f) further directs DOI to assure that replacement lands of equal fair market value, location, and usefulness are provided as conditions to such conversions. Consequently, where conversions of Section 6(f) lands are proposed for highway projects, replacement lands will be necessary.

There is an overlap between Section 4(f) and Section 6(f). Lands acquired and/or developed with LWCF funds are generally public parks or recreation areas, and therefore, are both Section 4(f) properties and subject to the requirements of Section 6(f). In identifying Section 4(f) properties, it is important to determine whether Section 6(f) LWCF funds were used to purchase all or part of the Section 4(f) property, or to develop a specific part of the property.

The statute (LWCF Act) states that replacement land “of at least equal fair market value and or reasonably equivalent usefulness and location” be provided where Section 6(f) property or features are converted to other uses. Therefore, when considering mitigation for a resource that is both a Section 4(f) property and a Section 6(f) resource, those mitigation measures should take into consideration the Section 6(f) requirements in addition to the Section 4(f) requirements, so that both statutes can be addressed.

Bridge Preservation

Our nation’s historic bridges are visible examples of over 200 years of innovative structural engineering design and material technology. They range from rare 17th-century bridges such as the Frankford Avenue Bridge in Philadelphia to examples of 20th century technology like the 1931 George Washington suspension bridge in New York City, the 1932 concrete Rouge River Bridge in Oregon, and the 1920s and 1930s bascule bridges in downtown Chicago. Historic bridges are also a part of our country’s transportation infrastructure, and therefore, an important component of any effort to maintain and preserve the nation’s highway bridge transportation assets. Bridge preservation is a critical issue among transportation professionals.

Transportation agencies are required to consider the effects of their undertakings on a wide range or cultural resources, including historic bridges, as part of their responsibilities under Section 106 of the National Historic Preservation Act (NHPA) and the National Environmental Policy Act (NEPA). Historic bridges that are listed on or eligible for listing on the National Register of Historic Places are also considered Section 4(f) properties under the Department of Transportation Act. Compliance with these different statutes requires, as an initial step, determining whether or not a bridge is eligible for listing in the National Register and therefore considered historic. To address this issue, the FHWA’s Highway Bridge Replacement and Rehabilitation Program includes a provision requiring each state to complete a statewide historic bridge inventory. Most states have completed their inventories and several have recently or are currently updating their inventory.