Corps May Treat State §401 Certifications as Conclusive and Use Post‑Issuance LEDPA Conditions in §404 Pipeline Permitting

Introduction

In Appalachian Voices v. United States Army Corps of Engineers (6th Cir. Apr. 4, 2025), environmental organizations Appalachian Voices and Sierra Club petitioned for review of the U.S. Army Corps of Engineers’ decision to issue a Clean Water Act (CWA) §404 permit to Tennessee Gas Pipeline Company, L.L.C. (TGP) for its 32‑mile Cumberland Pipeline across several Tennessee counties. The pipeline would traverse rocky terrain and require 149 stream crossings, as well as impacts to ponds and wetlands. Petitioners alleged violations of the Administrative Procedure Act (APA) in five principal respects: (1) failure to require trenchless Horizontal Directional Drilling (HDD) or otherwise select the least environmentally damaging practicable alternative (LEDPA) at each water crossing; (2) unlawful delegation to TGP of the LEDPA choice for rock removal, including blasting; (3) improper reliance on Tennessee’s §401 water quality certification; (4) improper reliance on an NPDES permit; and (5) failure to evaluate cumulative effects.

The case sits at the intersection of the Clean Water Act’s §404 dredge-and-fill program, §401 state water quality certifications, and the Natural Gas Act (NGA) regime under which FERC issues certificates of public convenience and necessity after environmental review. Here, TGP received (i) a §401 certification from the Tennessee Department of Environment and Conservation (TDEC), (ii) a FERC certificate following a multi‑agency Environmental Impact Statement (EIS) concluding that the project would not result in significant environmental impacts, and (iii) the Corps’ §404 permit with special conditions governing construction, waterbody crossings, and rock removal.

Summary of the Opinion

Applying deferential APA review, the Sixth Circuit denied the petition and upheld the Corps’ §404 permit. The court held:

The Corps reasonably determined that broad deployment of HDD was not a practicable alternative in the Western Highland Rim’s geology and slopes, and it was not required to conduct a pre‑construction, crossing‑by‑crossing LEDPA selection where the administrative record contained crossing‑specific information and the permit imposed enforceable conditions to ensure least‑impactful methods are used.
The Corps permissibly relied on post‑issuance permit conditions—including a requirement to use the “least impactful trenching technique practicable” and a pre‑approval requirement for any blasting—to satisfy the LEDPA mandate for rock removal.
Under 33 C.F.R. §320.4(d), the Corps could treat TDEC’s §401 water quality certification as conclusive evidence of compliance with applicable effluent limits and water quality standards; the Corps need not duplicate the state’s §401 analysis.
Even assuming any misstatement about the existence or timing of an NPDES permit, the Corps’ turbidity and suspended solids findings were independently supported by record evidence and best‑management practices; the court would not “flyspeck” the analysis.
The Corps adequately evaluated cumulative impacts and reasonably concluded that effects would be temporary and not significant such that compensatory mitigation was unnecessary.

Detailed Analysis

Precedents and Authorities Cited and How They Mattered

APA standard of review: The court emphasized “extremely narrow” review and the “zone of reasonableness,” citing FCC v. Prometheus Radio Project and Motor Vehicle Manufacturers v. State Farm. The Corps’ decision stands if it reasonably considered relevant issues and explained its path.
§404(b)(1) Guidelines (40 C.F.R. §230.10 and §230.11): The Corps must deny a discharge if a practicable alternative with less adverse impact exists. For special aquatic sites, there is a presumption of practicable alternatives; the Corps found that TGP rebutted that presumption for widespread HDD due to geology, slopes, and risk of inadvertent drilling fluid returns, as well as cost/time impracticability.
Post‑issuance mitigation and permit conditions: The court relied on Sixth Circuit precedents Sierra Club v. Slater and Kentucky Riverkeeper, confirming that the Corps may condition permits on future actions to minimize impacts. Here, special conditions mandated least‑impactful techniques and Corps approval before blasting, allowing the Corps to satisfy LEDPA without predetermining each crossing’s method.
§401 certification as conclusive: 33 C.F.R. §320.4(d) provides that state certifications of compliance with applicable effluent limitations and water quality standards “will be considered conclusive.” The court endorsed the Corps’ reliance on TDEC’s §401 certification, citing federalism principles (International Paper v. Ouellette) and cases recognizing states’ retained authority in pipeline projects (e.g., Mountain Valley Pipeline; Sierra Club v. State Water Control Board). City of Olmsted Falls was invoked to avoid duplicative or second‑guessing review of state determinations.
Harmlessness/anti‑flyspecking: The court relied on El Puente (D.C. Cir.) and Wolverine Pipe Line (6th Cir.) to reject vacatur based on an arguable misreference to an NPDES permit where other, independent reasons supported the Corps’ findings on turbidity and suspended solids.
Other Clean Water Act/NGA scaffolding: The opinion canvassed Sackett, SWANCC, Rapanos, Gwaltney, and Friends of Crystal River for CWA purpose and structure; PennEast, Schneidewind, and related cases for NGA jurisdiction; and Kentuckians for the Commonwealth, Coeur Alaska, and Cundiff for §404 implementation and environmental consequences analysis.

The Court’s Legal Reasoning, Issue by Issue

1) LEDPA and Trenchless Alternatives at Water Crossings

Petitioners argued the Corps was required to perform a crossing‑by‑crossing LEDPA determination (with a presumption favoring trenchless methods such as HDD for special aquatic sites). The Corps instead conducted a programmatic alternatives analysis grounded in:

Geotechnical realities of the Western Highland Rim—steep slopes and fractured bedrock increasing the risk of inadvertent drilling fluid returns (frac‑outs), necessitating higher drilling pressures for HDD, and thus elevating environmental risk.
Practicability factors under §230.10(a)(2)—cost, logistics, and timing, including significantly longer construction‑related disruption to nearby residents if HDD were widely required, compared to brief, dry open‑cut crossings.
Crossing‑specific tables in the record detailing dimensions, substrate, location, and potential impact for all waterbodies; the Corps required dry/open‑cut methods with flow diversions to avoid contact with stream water and limit sediment resuspension, while reserving HDD for specific crossings where justified.

Holding: The Corps reasonably explained why widespread HDD was not a “practicable alternative” and why the permitted approach satisfied LEDPA without a pre‑construction, crossing‑by‑crossing determination. The presence of detailed crossing‑level information and the imposition of enforceable permit conditions were key to this conclusion.

2) Rock Removal and Alleged Unlawful Delegation (Blasting)

Petitioners claimed the Corps unlawfully delegated the LEDPA choice for rock removal by allowing TGP to select among methods during construction, including possible blasting. The court rejected this argument because the permit contained binding special conditions:

TGP must “select the least impactful trenching technique practicable.”
Blasting is prohibited unless TGP provides advance written notice and obtains the Corps’ approval.

Under Sixth Circuit precedent, the Corps may satisfy §404(b)(1) through enforceable post‑issuance conditions and mitigation requirements. The court treated these conditions as the mechanism by which the Corps ensured LEDPA compliance at the point of execution, particularly given variable site conditions encountered during construction.

3) Reliance on TDEC’s §401 Water Quality Certification

Petitioners urged the Corps to independently verify compliance with state water quality standards rather than rely on TDEC’s §401 certification. The court held that:

33 C.F.R. §320.4(d) makes state §401 certifications “conclusive” as to compliance with applicable effluent limitations and water quality standards.
Requiring the Corps to re‑adjudicate state water quality standards compliance would be duplicative, cumbersome, and inconsistent with federalism principles and Congress’s design for state participation in §401 review.
The court declined to impose a “roving mandate” upon the Corps to second‑guess substantive state conditions, echoing American Rivers v. FERC.

Notably, TDEC later modified its state Aquatic Resource Alteration Permit (ARAP) to authorize limited additional impacts and expressly waived §401 authority for those new impacts. The court did not view that modification or waiver as undermining the Corps’ reliance on the original §401 certification for the §404 decision.

4) NPDES Permit Reference and Turbidity/Suspended Solids Findings

The Corps’ analysis of suspended particulates and turbidity referenced an NPDES permit that, according to petitioners, did not yet exist at the time of the Corps’ memorandum. The court declined to vacate on that ground because other, independent reasoning adequately supported the Corps’ conclusions:

Use of coffer dams and flow diversions to isolate the work area (i.e., dry crossing techniques).
Short duration of crossing activities (typically one to two days).
Implementation of erosion and sediment control best management practices.
TDEC’s finding that temporary increases in turbidity and total suspended solids would not violate water quality standards or cause long‑term effects.

The court refused to “flyspeck” for minor deficiencies where the overall reasoning was sound and supported by the record.

5) Cumulative Effects

Petitioners contended that the Corps ignored cumulative effects from multiple crossings on the same streams. The court pointed to the Corps’ §230.11(g) cumulative effects analysis, which found effects to be temporary and not significant, obviating compensatory mitigation. Because the agency’s path of reasoning could “reasonably be discerned,” the cumulative impacts analysis satisfied the APA.

What This Decision Clarifies and Why It Matters

Conclusive effect of state §401 certifications in §404 decisions: Within the Sixth Circuit, the Corps may treat a state’s §401 certification as conclusive regarding compliance with applicable effluent limitations and water quality standards (33 C.F.R. §320.4(d)), and is not obliged to duplicate the state’s determinations. This reinforces state primacy in water quality judgments within the §401 process, while streamlining federal §404 review.
LEDPA can be satisfied via enforceable permit conditions: The Corps need not always pre‑select a method at each crossing ex ante. Where the record contains crossing‑specific data, and the permit includes binding conditions requiring the “least impactful” method and reserving agency approval for riskier techniques (e.g., blasting), LEDPA may be satisfied through post‑issuance implementation.
Programmatic alternative analysis is permissible amid consistent geologic constraints: The Corps may reasonably reject widespread HDD where region‑wide geotechnical factors (slopes, fractured bedrock) elevate risks and costs, even if HDD is used at select crossings. A “HDD‑everywhere” alternative can be deemed impracticable.
Harmless‑error approach to ancillary permit references: An arguable misreference to an NPDES authorization will not compel vacatur where the substantive environmental findings are independently supported; courts will not invalidate agency decisions for minor errors in an otherwise reasonable analysis.

Potential Impact

On Future §404 Pipeline and Linear Infrastructure Permitting

Expect increased reliance on special permit conditions to operationalize LEDPA at the construction phase, especially in variable geologic settings.
Applicants should assemble robust, crossing‑level data tables (dimensions, substrate, flow, habitat) and demonstrate why particular techniques (HDD vs. dry open cut) are or are not practicable at scale, documenting geotechnical risks like frac‑outs.
States’ §401 certifications become even more pivotal; developers should engage early with state agencies to ensure complete records supporting state water quality findings that the Corps can treat as conclusive.
Challengers face a heightened burden: where the record shows reasoned consideration of alternatives and cumulative effects, courts are unlikely to disturb the Corps’ judgments under the APA.

On Federal–State Interplay and Federalism

The ruling reinforces the cooperative federalism design of the CWA: states retain a meaningful, determinative role in §401 certifications, and the Corps respects that role in §404 decisions.
State ARAP/§401 modifications and waivers can coexist with federal §404 approvals; clarity in the administrative record about the scope of any waiver or modification remains important.

On Administrative Law Doctrine

The opinion amplifies the “zone of reasonableness” and anti‑flyspecking approach. Minor imperfections do not doom an agency action if the reasoning and record support the outcome.
It also illustrates how post‑issuance conditions can serve as lawful mitigation and compliance mechanisms under §404, consistent with existing Sixth Circuit precedent.

Complex Concepts Simplified

Clean Water Act §404 permit: Authorization by the Corps to discharge dredged or fill material into “waters of the United States” at specified sites, often needed for stream and wetland crossings.
§401 water quality certification: A state’s confirmation that a federally permitted project will comply with applicable effluent limitations and state water quality standards; states can grant, condition, deny, or waive certification.
§404(b)(1) Guidelines and LEDPA: EPA’s binding guidelines require denial if a practicable alternative with less aquatic impact exists. “Practicable” accounts for cost, technology, and logistics. For “special aquatic sites,” alternatives are presumed practicable unless rebutted.
HDD vs. dry open‑cut: HDD drills beneath a waterbody to avoid in‑channel disturbance but may risk “frac‑outs” (unintended drilling fluid releases), especially in fractured bedrock. Dry open‑cut temporarily diverts stream flow around the work area to minimize turbidity and sediment resuspension during trenching.
Post‑issuance mitigation/conditions: Binding permit conditions that control how a project must be built (e.g., least‑impactful methods, agency approval before blasting). Courts allow the Corps to rely on these to ensure compliance with LEDPA and minimize impacts.
Cumulative effects: The combined impacts from multiple discharges or crossings considered together; agencies must evaluate whether these aggregate effects are significant and whether mitigation is required.
APA arbitrary‑and‑capricious review: A highly deferential standard; courts uphold agency action if the agency considered the important issues, examined the relevant data, and articulated a rational connection between facts and decision.

Conclusion

Appalachian Voices v. U.S. Army Corps of Engineers fortifies two practical pillars of §404 permitting in the Sixth Circuit. First, it confirms that the Corps may treat a state §401 certification as conclusive as to compliance with applicable effluent and water quality standards, avoiding duplicative federal review of state determinations. Second, it approves the use of enforceable, post‑issuance permit conditions to satisfy LEDPA obligations, particularly where site conditions vary and the agency has compiled crossing‑specific data and a reasoned alternatives analysis.

Coupled with the court’s adherence to deferential APA review and resistance to “flyspecking,” the decision signals that well‑documented programmatic alternatives analyses, tailored permit conditions, and robust state participation through §401 will together support §404 approvals for linear infrastructure traversing challenging terrain. For project sponsors, the opinion underscores the value of early geotechnical assessments, state agency engagement, and condition‑driven construction planning. For opponents, it highlights the need to identify truly material analytical gaps rather than incremental or formalistic errors.

Bottom line: In the Sixth Circuit, the Corps can lean on state §401 certifications and on special permit conditions to ensure that the least‑impactful, practicable methods are used in the field—without having to pre‑adjudicate every crossing—so long as its reasoning is grounded in the record and consistent with the §404(b)(1) Guidelines.