“Overall Project Purposes” Under CWA § 404(b) May Include Multiple Interconnected Objectives

1. Introduction

This published Tenth Circuit decision arises from a long-running fight over Denver Water’s “Moffat System Collection Project,” a $600 million (possibly higher) expansion of Gross Reservoir achieved by raising Gross Dam 131 feet to add roughly 77,000 acre-feet of storage. The project required a Clean Water Act (“CWA”) § 404 permit because construction placed dredge or fill material into waters of the United States at the base of the dam in South Boulder Creek. Because issuance of a § 404 permit is a “major Federal action,” the U.S. Army Corps of Engineers (“Corps”) also prepared a multi-volume Environmental Impact Statement (“EIS”) under NEPA.

Environmental organizations (Save the Colorado and others) challenged the Corps’ 2017 permit and EIS, and the district court agreed, vacating the EIS/ROD/permit and permanently enjoining reservoir enlargement activities (including water diversion). By the time of appeal, Denver Water had completed major construction, but could not fill the expanded reservoir due to the injunction.

The appeal presented three central merits issues under the APA’s arbitrary-and-capricious standard:

• Purpose definition: whether the Corps impermissibly defined the project’s purpose too narrowly by combining multiple needs (firm yield increase and system imbalance/vulnerability mitigation), thereby excluding otherwise “practicable” alternatives.
• Cost: whether the Corps’ planning-level cost approach (capital-cost estimate plus a 50% contingency multiplier) was arbitrary.
• Climate change: whether the Corps acted arbitrarily by declining to quantitatively model climate-change effects on streamflow and project feasibility given scientific uncertainty.

Thresholdly, Denver Water argued mootness because the § 404-authorized fill discharge was complete. The Tenth Circuit rejected constitutional mootness, finding potential partial relief remained available (e.g., additional mitigation or permit conditions).

2. Summary of the Opinion

On the merits, the court held:

• The Corps’ purpose formulation was lawful and not arbitrary or capricious; it could incorporate interconnected needs into a single purpose-and-need statement.
• The Corps reasonably relied on a 50% multiplier for contingent costs at the screening stage; the methodology was supported by consultant review and record documentation.
• The Corps reasonably discussed climate change qualitatively and explained why quantitative modeling was not “generally accepted” or sufficiently reliable for the required determinations; deference is especially appropriate for technical/scientific judgments.

3. Analysis

3.1 Precedents Cited

The opinion is heavily shaped by recent Supreme Court NEPA guidance and the Tenth Circuit’s administrative-law doctrines of deference, finality, and mootness, as well as out-of-circuit CWA § 404 purpose cases.

A. NEPA “procedural” role and judicial deference

• Seven Cnty. Infrastructure Coal. v. Eagle County, 605 U.S. 168 (2025): The court relied on this Supreme Court decision for two related propositions: (i) NEPA is procedural—meant “to inform agency decisionmaking, not to paralyze it”; and (ii) courts owe “substantial deference” to agency NEPA compliance judgments. This framing bolstered the court’s reluctance to second-guess the Corps’ technical treatment of costs and climate change.
• Dep't of Transp. v. Pub. Citizen, 541 U.S. 752 (2004): Cited for NEPA’s EIS/FONSI structure and baseline procedural requirements, reinforcing that NEPA’s function is disclosure and informed decision-making rather than substantive outcomes.

B. Purpose definition under CWA § 404(b) alternatives analysis

• Greater Yellowstone Coal. v. Flowers, 359 F.3d 1257 (10th Cir. 2004): Used to support that the Corps must account for the applicant’s project objectives in the alternatives analysis, and is not confined to a generic, maximally broad purpose.
• Sylvester v. U.S. Army Corps of Eng'rs, 882 F.2d 407 (9th Cir. 1989): Quoted as the cautionary principle that agencies cannot define a project “in order to preclude the existence of” practicable alternatives. The Tenth Circuit distinguished this concern on the record, emphasizing that many alternatives survived initial screening (and not all required dam expansion).
• Del. Riverkeeper Network v. U.S. Army Corps of Eng'rs, 869 F.3d 148 (3d Cir. 2017) and Friends of Santa Clara River v. U.S. Army Corps of Eng'rs, 887 F.3d 906 (9th Cir. 2018): Cited for textual support that “overall project purposes” can be plural and encompass multiple aims, reinforcing the Tenth Circuit’s reading as consistent with other circuits.

C. Deference limits: regulation interpretation and scientific judgments

• Kisor v. Wilkie, 588 U.S. 558 (2019): The court rejected reliance on Auer deference because it found § 230.10(a)(2) unambiguous. Kisor supplies the controlling rule: agency deference to regulatory interpretation applies only when a regulation is genuinely ambiguous.
• Nat'l Audubon Soc'y v. U.S. Army Corps of Eng'rs, 991 F.3d 577 (4th Cir. 2021) and W. Watershed Project v. U.S. Bureau of Land Mgmt., 76 F.4th 1286 (10th Cir. 2023): Invoked to underscore judicial deference to agencies’ technical/scientific modeling choices and methodology selection when adequately explained.

D. “Clearly demonstrate” and the LEDPA framework under § 404(b)

• Hillsdale Env't Loss Prevention, Inc. v. U.S. Army Corps of Eng'rs, 702 F.3d 1156 (10th Cir. 2012): Central to the court’s treatment of the non-water-dependent presumption. The panel emphasized that “clearly demonstrate” does not authorize courts to redo the LEDPA analysis. Rather, the Corps must take a “hard look” and reach a “meaningful conclusion based on the evidence.”

E. Mootness and finality doctrines shaping reviewability

• Rio Grande Silvery Minnow v. Bureau of Reclamation, 601 F.3d 1096 (10th Cir. 2010) and WildEarth Guardians v. Pub. Serv. Co. of Colo., 690 F.3d 1174 (10th Cir. 2012): Cited for the core constitutional mootness inquiry and burden allocation.
• Caddo Nation of Okla. v. Wichita & Affiliated Tribes, 877 F.3d 1171 (10th Cir. 2017) and Airport Neighbors All., Inc. v. United States, 90 F.3d 426 (10th Cir. 1996): These cases provided the NEPA/CWA completion-of-project mootness framework and the “partial relief” principle that saved jurisdiction here.
• Rocky Mountain Wild v. Dallas, 98 F.4th 1263 (10th Cir. 2024), W. Energy All. v. Salazar, 709 F.3d 1040 (10th Cir. 2013), and Ausmus v. Perdue, 908 F.3d 1248 (10th Cir. 2018): Used to address the administrative-remand rule and the “practical-finality” exception—important because the district court’s “remand with vacatur” plus permanent injunction could have made appellate review effectively unavailable.
• Winzler v. Toyota Motor Sales U.S.A., Inc., 681 F.3d 1208 (10th Cir. 2012): Cited for prudential mootness, though the panel declined to reach it after resolving the merits.

3.2 Legal Reasoning

A. Textual separation of “basic purpose” and “overall project purposes”

The decision’s most durable contribution is its reading of 40 C.F.R. § 230.10(a) as containing two distinct purpose concepts:

• “Basic purpose” (used in § 230.10(a)(3)) asks whether the activity is “water dependent” (i.e., whether it must be sited in special aquatic sites to fulfill its essential function).
• “Overall project purposes” (used in § 230.10(a)(2)) supply the lens for practicability, including cost, technology, and logistics.

The court anchored this distinction in (i) the presumption that different regulatory wording has different meaning, (ii) ordinary dictionary definitions, and (iii) the regulation’s plural phrase “overall project purposes,” which the court treated as strong textual evidence that multiple purposes may be considered. Context also mattered: water-dependency is a coarse, threshold inquiry; alternatives analysis requires a more granular articulation of what the applicant is trying to achieve.

Practical implication: Applicants (and the Corps) may lawfully articulate interconnected, multi-part objectives without being forced into a single generalized purpose that would open the alternatives set to projects that meet only one component of the applicant’s integrated problem.

B. Deference posture under CWA “clearly demonstrate” and NEPA review

The panel emphasized that even where the non-water-dependent presumption applies—requiring the Corps to “clearly demonstrate” the LEDPA—judicial review remains deferential. The question is whether it was arbitrary and capricious for the Corps to find it had clearly demonstrated LEDPA, not whether the court independently agrees with the LEDPA conclusion.

Under NEPA, the court leaned on Seven Cnty. for “substantial deference,” reinforcing that NEPA does not authorize courts to demand maximal modeling sophistication so long as the agency reasonably explains its choices and considers the relevant factors.

C. Cost methodology: planning-level estimates are permissible when explained

The Corps’ early-stage screening involved hundreds of alternatives and limited design detail, making project-specific precision impracticable. The panel credited record evidence that:

• the Corps did not “blindly adopt” Denver Water’s approach;
• a third-party consultant reviewed the method and found it useful for comparing alternatives (even if not suitable as a final budget);
• supporting documentation explained why contingent costs were estimated via a multiplier and why 50% was a reasonable aggregation of typical subcomponents.

The court’s reasoning effectively validates a common EIS/§ 404 practice: using uniform, transparent, planning-level cost assumptions to compare many alternatives, particularly where greater precision is impossible without committing to designs the screening process is meant to avoid.

D. Climate change: qualitative discussion plus a reasoned explanation can suffice

The Corps acknowledged potential climate effects (earlier peak runoff, reduced flows), explained why translating warming into incremental streamflow impacts lacked a “generally-accepted scientific method,” and described model/data uncertainty (particularly for Colorado hydrology). The court treated this as a technical judgment within agency expertise and deferred.

Notably, the court also accepted the Corps’ response that increased yield was not solely dependent on Moffat Tunnel peak capacity because part of the yield would come from reoperation of Denver Water’s broader system, and the record cited decades of data and independent analysis.

E. Mootness: project completion does not moot if partial relief remains

Even though the fill discharge was complete, the court held the case was not constitutionally moot because a remand could still produce “some effect in the real world,” including additional mitigation measures or strengthened permit conditions addressing ongoing or future impacts (e.g., environmental harms associated with remaining work and operation/filling).

3.3 Impact

A. A clearer, more applicant-sensitive purpose standard in the Tenth Circuit

The opinion strengthens the Corps’ (and applicants’) position that “overall project purposes” may reflect multiple integrated objectives—so long as they are related and explained. This will matter in water-supply, energy, and transportation permitting where applicants often face coupled problems (capacity, redundancy, reliability, resilience).

B. Litigation focus likely shifts from “too narrow purpose” to record support

By anchoring purpose definition in text and plural phrasing, the decision may narrow the set of successful “purpose too narrow” challenges. Future plaintiffs may instead focus on whether the agency (i) genuinely evaluated a reasonable range of alternatives under the chosen purposes, or (ii) used “interconnected needs” as a pretext to exclude workable solutions.

C. Cost and climate modeling challenges face a higher “explanation” hurdle, not a “do more modeling” right

The court’s approach signals that challengers must identify a clear methodological failure—an ignored relevant factor, an internal inconsistency, or an explanation contrary to the record— rather than simply arguing that more granular costing or quantitative climate modeling would have been preferable.

D. Post-construction NEPA/CWA suits remain live where ongoing operational relief is plausible

The mootness holding underscores that completion of a discrete construction activity does not automatically foreclose judicial review if agencies retain authority to impose additional mitigation or conditions that could reduce continuing harm.

4. Complex Concepts Simplified

• § 404(b) permit (CWA): Federal authorization required to discharge dredged or fill material into covered waters (e.g., wetlands/streams).
• LEDPA: “Least environmentally damaging practicable alternative”—the Corps must choose (or permit) the alternative that is feasible (considering cost/technology/logistics) and minimizes aquatic harm.
• Water-dependent vs. non-water-dependent: If a project’s basic purpose requires being in the water (e.g., a marina), it is water-dependent; if not, it is non-water-dependent and faces a presumption that less damaging alternatives exist.
• EIS / ROD (NEPA): The EIS analyzes significant environmental effects and alternatives; the Record of Decision documents the agency’s final choice and rationale.
• Arbitrary and capricious (APA): A deferential review standard asking whether the agency considered relevant factors, explained itself, and stayed within reasoned decisionmaking.
• Constitutional mootness vs. prudential mootness: Constitutional mootness is jurisdictional (no effective relief possible); prudential mootness is discretionary (relief possible but not worth it). The court found constitutional mootness absent and bypassed prudential mootness.
• Auer/Kisor deference: Courts may defer to an agency’s interpretation of its own ambiguous regulation, but only if the regulation is genuinely ambiguous and other Kisor requirements are met. Here, the court found no ambiguity.

5. Conclusion

Save The Colorado v. Graham is a consequential Tenth Circuit decision for CWA § 404(b) permitting and NEPA review in infrastructure cases. It clarifies—on textual grounds—that “overall project purposes” under 40 C.F.R. § 230.10(a)(2) may encompass multiple interconnected objectives, distinct from the “basic purpose” used for water-dependency. It also reinforces strong APA deference to agency methodology choices on cost and climate analysis when the agency meaningfully addresses the issues and explains the limits of available data and models.

Bottom line: in the Tenth Circuit, challengers will face an uphill climb when arguing that the Corps must collapse a multi-objective project into a single generalized purpose, or that agencies must quantitatively model climate impacts despite acknowledged scientific uncertainty—so long as the record reflects a reasoned explanation and a “hard look.”