It defines the search area
Within the APE, the agency must make a reasonable and good-faith effort to identify historic properties that may be affected.
APE Explorer: An analysis of 60 energy projects and the scope of their NHPA Section 106 review areas
Under Section 106 of the National Historic Preservation Act, every federally permitted project gets a historic-preservation review. Federal agencies begin by setting an Area of Potential Effects, or APE — the zone around the project that the agency must examine for impacts on historic properties, including visual impacts. There is no standard APE radius, and projects can receive wildly different zones to evaluate.
The APE for Revolution Wind, an offshore wind farm, extended 40 miles around the entire lease area, totaling more than 5,000 square miles. The SunZia transmission line's APE included everything visible within 5 miles of any project component along its 550-mile route. That definition meant an APE that spans up to 5,500 square miles, more than twice the size of Delaware. The total APE for a recent gas pipeline project was about 2 square miles. Reforming NHPA to right-size the APE is a clean-energy win by helping clean energy and transmission projects get built faster.
Why the gap: review scope scales with visibility. An APE is not just the project footprint. Alongside the zone of ground disturbance, agencies add a visual-effects zone extending as far as the project can be seen. Wind turbines and transmission towers are tall by necessity, so their visual APEs stretch for miles. Gas pipelines are buried and compressor stations are low-profile, so their APEs typically end at half a mile or where line of sight is blocked.
Why that matters: A larger APE can mean more research, consultation, property evaluations, time, and litigation risk.
Depicted is the present condition; hovering or tapping reveals the “adverse effect” that distant wind turbines from the Lava Ridge Wind Project — inside the red circle — would have on the Minidoka historic property.
Section 106 is a procedural law: it requires agencies to consider effects on historic properties, but it does not require preservation, mitigation, or any other particular outcome. An overlarge APE adds delay, work, and expense — and even influences whether projects are proposed at all.
Within the APE, the agency must make a reasonable and good-faith effort to identify historic properties that may be affected.
A wider area can bring more properties, preservation offices, Tribes, local governments, and other consulting parties into the review.
More identification, eligibility decisions, effects analysis, and negotiation can increase cost, delay, and exposure to litigation.
Each ring shows the median indirect or visual APE distance for a project category. A 40-mile radius encloses about 5,000 square miles — larger than Los Angeles County. A half-mile radius encloses about 0.8 square miles — about three-fifths of Central Park.
Agencies aren't trying to burden clean energy in their NHPA administration. Because visual review is pegged, by regulation, to how far a project can be seen (and clean-energy infrastructure is tall), a facially neutral rule produces much larger review areas for these projects.
A review system that scales with visibility exposes renewable energy generation and transmission to longer delays and greater litigation exposure. These are the projects a clean-energy buildout requires. Treating these projects fairly doesn't require ignoring all visual effects on historic properties. The question for Congress is whether the geographic scope and legal consequences of that consideration are clear, consistent, and proportionate to effects on actual historic properties.
Congress can make APE determinations more consistent and proportionate while preserving review of genuine effects on historic properties. Reform benefits clean energy projects most: gas and LNG review areas are already small, so setting maximum APE scope changes little for them. The gains from each reform below go overwhelmingly to wind, solar, and transmission projects.
Establish a bright-line limit on visual APEs — such as three miles — or direct the Advisory Council on Historic Preservation to adopt such a limit by regulation as they have done for tall FCC-permitted telecom infrastructure.
Treat a visual change as adverse only when it materially diminishes a documented characteristic that makes a property eligible for the National Register, measured against the property's existing setting.
Limit Section 106 effects to those directly, proximately, and causally attributable to the discrete federal undertaking, rather than cumulative or regional effects of independent actions.
Entire land- and seascapes — including the 500–600-square-mile Nantucket Sound — have been treated as single historic properties. Require parties to identify the specific character-defining features that make such a property eligible, and limit adverse-effect findings to material impairment of those features.
APE reform is one part of a broader Section 106 agenda. The full proposal also addresses deadlines, mitigation, litigation remedies, and SHPO/THPO capacity.
Read the full reform proposal →Start with how the reviews ended, then compare the geographic reach of indirect or visual review and the acreage reported for direct review or survey.
Share of projects whose public record shows adverse-effect findings, MOAs, treatment plans, or equivalent mitigation obligations.
The 38 projects whose public Section 106 or NEPA documents state an indirect or visual distance, ranked. Every figure above two miles belongs to a clean-energy project except Rio Grande LNG's 12-mile indirect study area, which its EIS does not describe as a defined APE.
38 projects with a stated distance, in statute miles
Search the underlying evidence register. Source descriptions and page references are reproduced as coded; missing public evidence is not treated as zero burden. Download the evidence register.
All 60 project reviews — search or filter by category
| Project | Type | Agency | Direct APE / survey | Indirect / visual APE | §106 outcome | Source |
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This first-pass pilot dataset covers 60 federal energy-project reviews, primarily from January 1, 2021 through June 27, 2026, plus several earlier comparators. It draws from FERC environmental reviews for gas and LNG projects; BOEM findings and agreements for offshore wind; and BLM agreements, treatment plans, and environmental reviews for wind, solar, and transmission projects.
Section 106 requires agencies to take into account an undertaking's effects on properties listed or eligible for the National Register of Historic Places, in consultation with Historic Preservation Officers, Tribes, and the Advisory Council on Historic Preservation. It is procedural — it requires consideration and consultation, not preservation or any particular result. Within the APE, the agency must make a reasonable and good-faith identification effort, evaluate identified properties that have not already been evaluated, and assess adverse effects where historic properties may be affected.