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Guidelines for Defining the Area of Potential Effects (APE)


Section 106 of the National Historic Preservation Act requires federal agencies to define and document the Area of Potential Effects (APE) in consultation with the State Historic Preservation Office (SHPO).  This requirement applies to any federal undertaking and should take place early in the environmental review process.  The South Carolina SHPO also uses Section 106 procedures as guidelines for consultation in certain state regulatory processes.

In the Section 106 process, the federal agency, or a representative of the federal agency, must identify historic properties and determine the effect of the proposed project on them.  Thus, the reason for defining an APE is to determine the area in which historic properties must be identified, so that effects to any identified properties can, in turn, be assessed.  (Historic properties are buildings, structures, objects, sites, and districts with significance in American history, architecture, archaeology, engineering, and culture.  These properties may be listed in or eligible for the National Register of Historic Places.)


Definition
According to 36 CFR 800.16(d), the Area of Potential Effects is the geographic area or areas within which an undertaking may directly or indirectly cause changes in the character or use of historic properties, if such properties exist.  The area of potential effects is influenced by the scale and nature of the undertaking and may be different for different kinds of effects caused by the undertaking.

Determining APE is a hypothetical process that considers the interplay of the three factors in bold.

Geographic Area
The project setting is an important factor in defining the APE.  Varying combinations of geographical location, topography, soils, vegetation, and other environmental factors increase or decrease the likelihood of a project having physical, visual, and auditory effects on historic properties.

Consider how various environmental factors influence the APE:

  • Is the setting a rural or urban area?
  • Is the surrounding landscape wooded? open fields? hilly? flat?
  • What is current land use—developed or agricultural?
  • If developed, how? Industrial, residential, commercial?  Define size and
    scale of development.
  • What are the views from the project area and toward the project area?

Example:  With the update and expansion of the Blue River Hydroelectric Plant, the Light Bulb Power Company plans to install a new transmission line running from the plant to its substation 15 miles to the north. The line would run through a small state forest, agricultural land and the Green Land community. Part of the agricultural property that the line intersects belongs to Farmer Smith. His home was constructed in the 1880s and is part of a large farm complex.



APE: The project will have not only a direct effect on the transmission line corridor and the associated construction with the towers and lines, but it will indirectly affect the viewshed all along the corridor.  The APE changes due to the topography of the area and the land use (flat agricultural land vs. forested areas).

Scale and Nature of the Undertaking
The scope of the project greatly affects the effort required to identify historic properties, and thus the way an APE is defined.

Consider different aspects of the scale and nature of undertaking when defining the APE:

  • If new construction—how large, how many stories, and how many square feet?
  • What is the extent of the ground disturbance? Are access roads or staging areas needed?
  • Are additions to or demolition of an existing building involved?
  • Is rehabilitation involved—entire building or just a few elements?
  • What is the scale of new construction in relation to the surrounding setting?

Example:  The Department of Housing and Urban Development will rehabilitate a home at 456 Lovely Street in the Pretty Heights Neighborhood. HUD plans to repair the exterior siding, install new windows, and renovate the interior with new flooring, paint and appliances.


APE:  The project will directly affect the home at 456 Lovely Street.  Indirect effects could include the impact of the rehabilitation of the home on the surrounding neighborhood.

Effects
The effects a project might have on historic properties vary with the setting and the scale and nature of the undertaking.  Consider these examples of effect when defining an APE and remember that effect can be direct or indirect, beneficial or adverse:

  • Physical changes to the area—actual takings, ground disturbance
  • Visual changes, including changes to the appearance of buildings, structures, sites, or districts.  Also changes in view sheds.
  • Changes to existing pedestrian and traffic patterns.
  • Changes in land use.

Example:  The United States Postal Service plans to build a new Post Office in Boomtown. The USPS purchased two vacant homes on the corner of Main and Oak Streets—right in the middle of downtown. The new location is between the downtown commercial historic district and the Shady Acres Neighborhood historic district.  The USPS plans to demolish the two vacant homes for the new 4000-square-foot facility with a loading dock, which will be in operation 24 hours a day. 


APE: For this project, the area of potential effect would include the direct effects to the property on which the building would be constructed (including the two 1940s residential structures and the potential for archaeological sites).  The project also could indirectly affect the surrounding neighborhoods through the proposed site work, the lighting of the building, an increase in noise, the design and size of the building, and the proposed increase in traffic around the new facility.

Key Points to Remember about the APE

  • The federal agency, in consultation with the SHPO and/or Tribal Historic Preservation Office, establishes the Area of Potential Effects (APE) in which identification efforts will occur.
  • The APE is defined before identification actually begins, so it may not be known whether any historic properties are within the APE.
  • The APE should include
    • all alternative locations for all elements of the undertaking
    • all locations where the undertaking may result in ground disturbance
    • all locations from which elements of the undertaking (e.g. structures or land disturbance) may be visible or audible; and
    • all locations where the activity may result in changes in traffic patterns, land use, public access, etc.
  • An APE may include areas that are not contiguous to the project tract, and may not be the same area of effect defined under the National Environmental Policy Act (NEPA).

Example:  Light Bulb Power Company wants to build an addition to its hydroelectric facility on the Blue River. The addition would increase the hydroelectric facility’s electrical output.  Upstream from the plant is a known archaeological site from the early days of settlement in the area. Across the Blue River from the Power Company site is the Blue River Bluff Historic District.


APE: The APE includes the direct effect of the proposed addition and the indirect effect to the surrounding environment and the viewshed from the facility to nearby properties.  The indirect APE would encompass views of the site from across the river as well as views of the site from the river.

The Next Step – Identification 
The Identification process begins once the APE has been clearly defined.  Cultural resources surveys are often required as part of the identification process.  Archaeological surveys are generally limited to the project footprint, whereas the survey area for above ground resources--such as buildings, structures, sites, districts, and landscapes--may be larger, taking into account the potential for visual, auditory, and other effects.

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