NEPA’s Proximate-Effects Limit and the “No Incremental Impact” Safe Harbor: Fifth Circuit Clarifies Scope, Preservation, and Climate Analysis in Indigenous Peoples v. U.S. Army Corps of Engineers

Introduction

This appeal arises from a high-stakes challenge to a U.S. Army Corps of Engineers permit authorizing dredging and in-water disposal to expand the Enbridge Ingleside Oil Terminal on the Texas Gulf Coast. Plaintiffs—two Indigenous groups (Indigenous Peoples of the Coastal Bend and the Karankawa Kadla Tribe of the Texas Gulf Coast) and a local association (Ingleside on the Bay Coastal Watch Association)—contended that the Corps’ Environmental Assessment (EA) under the National Environmental Policy Act (NEPA) and public-interest review under the Clean Water Act (CWA) failed to take a sufficiently “hard look” at environmental impacts, including seagrass destruction, community noise/light, oil-spill risks, cumulative effects, and climate change. The district court granted summary judgment to the Corps and the terminal owner (Enbridge Ingleside Oil Terminal, LLC), and the Fifth Circuit affirmed.

This opinion sets out three especially consequential holdings:

Preservation: NEPA objections tied to increased vessel traffic were forfeited because Plaintiffs did not raise them during the agency’s notice-and-comment period; an appellant must also list as an “issue” the district court’s adverse forfeiture ruling in the opening brief (not just argue around it), or the forfeiture stands.
Scope and Cumulative Impacts: In an EA, the Corps may limit review to the proximate effects of the permitted action; if the agency finds “no incremental impact” (due to mitigation) it need not conduct an extensive cumulative-impacts analysis—reaffirming Atchafalaya Basinkeeper and distinguishing O’Reilly.
Climate: NEPA’s “hard look” obligations regarding greenhouse gases are satisfied by discussing the direct effects of the permitted dredge-and-fill activity; the court declined to require the Corps to analyze downstream emissions from end-use combustion or increased exports.

Summary of the Opinion

Judge Willett, writing for a unanimous panel (Judges Jones, Willett, and Engelhardt), affirmed the district court’s judgment upholding the Corps’ EA and Finding of No Significant Impact (FONSI). The court:

Rejected the government’s argument that Plaintiffs waived their “scoping” challenge; Plaintiffs’ briefing below sufficiently preserved the contention that the Corps should have analyzed certain effects. But the court agreed with Enbridge that all arguments predicated on “increased vessel traffic” were forfeited because Plaintiffs did not raise them in the agency comment process and did not properly present a challenge to the district court’s forfeiture ruling in their opening appellate brief.
Upheld the Corps’ impacts analysis under NEPA and the CWA, including its weighing of benefits/costs, its incremental and cumulative-impacts determinations (given robust mitigation), and its “public interest review.”
Held that NEPA did not require an EIS because the EA reasonably addressed the Council on Environmental Quality’s significance factors and supported a FONSI.
Confirmed that the Corps’ climate discussion satisfied NEPA; the court declined to adopt out-of-circuit requirements to quantify or analyze downstream end-use emissions.

Analysis

Precedents Cited and How They Shaped the Decision

Motor Vehicle Manufacturers Ass’n v. State Farm (U.S. 1983): Reiterated the deferential APA standard—courts do not substitute their judgment, but ask if the agency considered relevant factors and articulated a rational connection between facts found and choices made. This anchored the panel’s posture of deference.
United States v. Olano (U.S. 1993): Distinguishes “waiver” (intentional relinquishment) from “forfeiture” (failure to timely assert). The opinion uses Olano to frame its preservation analysis.
Rollins v. Home Depot (5th Cir. 2021) and related cases: Applied Fifth Circuit preservation rules—failure to raise issues below or to brief them adequately on appeal results in forfeiture; issues not raised in the opening brief are forfeited.
Atchafalaya Basinkeeper v. U.S. Army Corps of Engineers (5th Cir. 2018): Critical NEPA precedent. If an EA reasonably finds no incremental impact due to mitigation, an extensive cumulative-impacts discussion is unnecessary. The panel applies that approach to uphold the Corps’ abbreviated cumulative analysis.
O’Reilly v. All State Financial Co. (5th Cir. 2023) (unpublished): Clarifies Atchafalaya’s limits. Where an EA acknowledges incremental impacts, a truncated cumulative analysis is improper. The panel distinguishes O’Reilly because the EA here found no significant incremental impacts and described compensatory mitigation to reach “no net loss.”
City of Dallas v. Hall (5th Cir. 2009): An EA is a “rough-cut, low-budget” document used to decide whether an EIS is needed. The panel leverages Hall to reject calls for EIS-level detail in the EA.
Sierra Club v. Sigler (5th Cir. 1983): Plaintiffs’ reliance on Sigler’s cost-benefit dicta faltered. The court explained Sigler addressed EISs, relied on then-extant “worst-case” analysis later eliminated by CEQ and the Supreme Court (Robertson), and predates Corps-specific NEPA regulations. Thus, Sigler’s stringency is inapposite to today’s EA practice.
Robertson v. Methow Valley Citizens Council (U.S. 1989) and CEQ’s 1986 rulemaking: Confirmed the elimination of “worst-case” analysis; relevant to limiting Sigler and endorsing modern, pragmatic NEPA review.
Center for Biological Diversity v. U.S. Army Corps of Engineers (11th Cir. 2019): The panel expressly aligns with the Eleventh Circuit that the Corps may describe a project’s purpose and benefits without chasing “the chain of causation to the ends of the earth.” The costs and benefits analysis need only match the scope of proximately caused effects under NEPA; remote downstream effects need not be quantified simply because the agency referenced broader benefits.
Kentuckians for the Commonwealth, Inc. v. U.S. Army Corps of Engineers (6th Cir. 2014): Supports the idea that a single document can “serve many functions,” allowing the Corps to calibrate scope for different legal tasks—narrow under NEPA, broader for the CWA public interest review—without cross-pollinating every downstream inquiry.
National Ass’n of Home Builders v. Defenders of Wildlife (U.S. 2007): Even if an agency’s reasoning is less than ideal, courts uphold if the “agency’s path may reasonably be discerned.” The panel uses this to acknowledge that while more detail is sometimes desirable, NEPA demands reasoned—not perfect—explanations.

Legal Reasoning

1) Preservation: Scoping Not Waived; Increased-Vessel-Traffic Arguments Forfeited

The court carefully parsed preservation doctrines:

Scoping: Plaintiffs sufficiently preserved the scoping dispute by arguing that effects from vessel traffic (oil spills; seagrass; community noise/light; cumulative and climate impacts) should have been analyzed—even if they did not expressly use the word “scoping.” Thus, no waiver at the district court stage.
Increased Vessel Traffic: Those same vessel-traffic-based theories were forfeited because Plaintiffs did not present them during the agency’s notice-and-comment process. Critically, the panel emphasized an appellate practice point: because the district court held forfeiture, Plaintiffs had to list that adverse ruling as an “issue presented” in the opening brief under FRAP 28. They did not, and arguments first raised in reply are too late. The result is a double lock: arguments dependent on increased vessel traffic are out of the case.

2) NEPA Impacts Analysis: Proximate Effects and Coextensive Review

On the merits, the court held the Corps’ impacts analysis was reasonable:

Scope of Effects Under NEPA: The Corps’ NEPA regulations (33 C.F.R. pt. 325, App’x B § 7(b)(3)) require that the scope of impacts and alternatives analysis be aligned with the scope used for benefits—but only as to effects proximately caused by the permitted action. Adopting the Eleventh Circuit’s reasoning, the court rejected a rigid coextensiveness rule requiring the Corps to evaluate remote downstream costs simply because it referenced broader project benefits.
Oil Spills and Pollutants: Independent of vessel-traffic claims, the EA explicitly acknowledged oil-spill risks and found them negligible; it also concluded the project could reduce pollutants by limiting vessel near-shore time. Those determinations were within the Corps’ discretion.

3) CWA Public-Interest Review: Flexible, Not Data-Heavy

The Corps’ CWA regulations (33 C.F.R. § 320.4) require a “public interest review” balancing reasonably foreseeable detriments against benefits, including economics and public and private need. The court held:

The Corps adequately weighed the project’s benefits (e.g., accommodating larger vessels; energy availability) against detriments (wetlands impacts), documented public comments, and made the specific CWA finding that benefits outweighed harms.
Nothing in the CWA requires particularized econometric or quantitative cost-benefit modeling in an EA; the Corps’ qualitative balancing sufficed.
Using one document (the EA) to perform both NEPA and CWA functions does not force the Corps to adopt the broadest scope everywhere; scope can be tailored to each statute’s requirements.

4) Incremental and Cumulative Impacts: The Atchafalaya “No Incremental Impact” Safe Harbor

NEPA requires agencies to consider cumulative impacts—i.e., the impact of the action’s incremental contribution added to other past, present, and reasonably foreseeable future actions. The court:

Reaffirmed Atchafalaya Basinkeeper: If the EA reasonably finds that mitigation will eliminate or neutralize incremental impacts (e.g., “no net loss” of aquatic resources), an extensive cumulative-impacts analysis is not required.
Distinguished O’Reilly: There, the Corps acknowledged incremental effects such as habitat loss and traffic but still eschewed cumulative analysis—error. By contrast, this EA found only temporary effects, explained re-establishment of organism populations, imposed compensatory mitigation, and concluded “no net loss” in the watershed.
Parallel CWA Requirement: Because the CWA’s cumulative-effects review is functionally similar—and Plaintiffs identified no meaningful difference—the same analysis sufficed for the CWA.

5) Climate Change: Proximate, Not Downstream, Effects

The EA’s “Climate Change” section found only negligible greenhouse-gas (GHG) releases from dredging/filling and associated construction equipment, weighed against national energy/security goals. The court held:

Within the Fifth Circuit, NEPA’s “hard look” at climate requires discussing relevant factors and explaining the decision. The Corps met that standard.
Out-of-circuit decisions urging analysis of downstream end-use emissions (e.g., from exported petroleum products) are not binding; the court expressly declined to adopt them here.
In any event, Plaintiffs’ downstream-climate and vessel-traffic theories were forfeited.

6) No EIS Required: CEQ Significance Factors Addressed

Applying CEQ’s significance factors, the court concluded the FONSI was reasonable:

Controversy: Public opposition and agency comments urging an EIS do not alone make effects “highly controversial”; the Corps responded to comments and explained mitigation.
Unique Geographic Characteristics: The EA recognized seagrasses and wetlands and adopted compensatory mitigation; this factor was analyzed.
Uncertainty/Unknown Risks: Plaintiffs’ argument hinged on absent vessel-traffic data; those claims were forfeited and otherwise undeveloped.
Connected/Cumulative Actions: The EA specifically discussed other dredging projects, including Corpus Christi Ship Channel expansion, and found cumulative impacts insignificant given mitigation.
Public Health/Safety: Oil-spill risk, noise, and light were either addressed or predicated on forfeited vessel-traffic theories; nothing compelled an EIS.

Impact

This opinion has significant practical and doctrinal consequences for NEPA/CWA litigation in the Fifth Circuit:

Preservation Imperative: Stakeholders must raise specific impact theories (e.g., vessel-traffic externalities, downstream emissions) during the agency’s comment period or risk categorical forfeiture. On appeal, any adverse preservation ruling must be identified as an “issue presented” in the opening brief.
Scope Discipline Under NEPA EAs: Agencies can describe broad purposes and benefits without undertaking globalized analyses of remote consequences. Proximate effects govern NEPA scope in EAs. This rejects attempts to bootstrap downstream effects into an EA based solely on statements about project benefits.
Mitigation-as-Safe-Harbor: Where an EA reasonably finds that mitigation eliminates incremental effects (e.g., no net loss of aquatic resources), the Corps may forego an exhaustive cumulative-impacts discussion. This reinforces the strategic value of early, enforceable mitigation commitments.
Climate Litigation: The court’s refusal to require downstream GHG analysis in this context marks a divergence from some out-of-circuit approaches. In the Fifth Circuit, agencies may satisfy NEPA by addressing the direct, proximate climate effects of the permitted activity—especially in an EA.
Unified Documents, Tailored Analyses: Agencies may use a single document to satisfy multiple statutes while tailoring scope to each law (narrow under NEPA, broader for the CWA’s public interest review). Practitioners should not assume a broad benefits discussion under the CWA forces an expansive NEPA analysis.

Complex Concepts Simplified

NEPA: EA vs. EIS
- EA: A concise document to decide if impacts are significant. If not, the agency issues a FONSI and stops.
- EIS: A full-dress, detailed review required only if significant impacts are likely.
“Hard Look”: NEPA requires reasoned consideration of relevant environmental factors—not the most exhaustive possible analysis—and a rational explanation.
Waiver vs. Forfeiture
- Waiver: Intentional relinquishment (e.g., abandoning an argument in briefing).
- Forfeiture: Failure to timely raise an issue (e.g., not commenting during notice-and-comment; not listing an adverse ruling as an “issue” in the opening brief).
Scoping: Early NEPA decision about what effects are “in” or “out” of the analysis based on causation and reasonableness; here, proximate effects of dredging and construction were “in,” remote vessel-traffic externalities were largely “out.”
Incremental vs. Cumulative Impacts
- Incremental impact: The project’s own additional effect.
- Cumulative impact: The incremental impact added to other past, present, and foreseeable actions.
- Key rule: If mitigation eliminates incremental effects (no net loss), the agency need not undertake an extensive cumulative analysis.
CWA Public Interest Review: A balancing under 33 C.F.R. § 320.4 of benefits and reasonably foreseeable detriments, including economics and environmental concerns; it does not mandate a formal cost-benefit calculus.
Proximate Effects vs. Downstream Effects: NEPA focuses on effects closely caused by the agency action. Agencies need not trace distant chains of causation, especially in an EA.
Climate Analysis in EAs: In the Fifth Circuit, discussing direct GHG implications of the permitted activity with a reasoned explanation typically suffices; downstream end-use emissions analyses are not automatically required.

Conclusion

Indigenous Peoples v. U.S. Army Corps of Engineers fortifies three core principles in the Fifth Circuit’s NEPA/CWA jurisprudence. First, preservation is paramount: objections must be aired in agency comments and, on appeal, adverse rulings must be distinctly identified as “issues” in the opening brief. Second, scope is bounded by proximate causation: an EA need not chase remote downstream effects, and a finding of “no incremental impact” (supported by concrete mitigation) permits a streamlined cumulative-impacts discussion. Third, climate analysis in an EA may be modest and focused on direct effects of the permitted activity; the court declined to impose an out-of-circuit duty to quantify downstream end-use emissions.

For agencies and project sponsors, the decision validates pragmatic, mitigation-forward EAs and confirms flexibility to tailor analyses to statutory requirements. For challengers, it underscores the need to (1) participate specifically and thoroughly during notice-and-comment, (2) focus NEPA critiques on proximate, preserved effects, and (3) carefully frame appellate issues from the outset. In the broader legal landscape, the Fifth Circuit’s alignment with a proximate-effects orientation and its reaffirmation of Atchafalaya’s “no incremental impact” safe harbor will shape permitting and litigation strategies for energy and infrastructure projects across the Gulf Coast and beyond.