“Overall Project Purposes” May Encompass Multiple Interrelated Objectives Under CWA § 404(b) Alternatives Review

I. Introduction

Save The Colorado v. Graham (10th Cir. Sept. 15, 2026) arises from a long-running dispute over Denver Water’s Moffat System Collection Project, a major water-supply initiative to expand Gross Reservoir by raising Gross Dam 131 feet. Because the dam expansion required placing fill in South Boulder Creek, Denver Water needed a Clean Water Act (“CWA”) § 404 permit from the U.S. Army Corps of Engineers (“Corps”). The Corps issued the permit in 2017 after a fourteen-year process and an EIS prepared to satisfy both CWA and NEPA requirements.

Environmental organizations—Save the Colorado and others—challenged the permit and NEPA documents, arguing the Corps unlawfully: (1) defined the project purpose too narrowly (thereby excluding practicable, less-damaging alternatives), (2) used an inadequate cost methodology, and (3) failed to quantify climate-change impacts on project feasibility and streamflows. The district court agreed, vacated the permit/EIS/ROD, and permanently enjoined enlargement of the reservoir (including tree removal and water diversion).

On appeal, the Tenth Circuit reversed—both clarifying how “overall project purposes” may be framed under the § 404(b)(1) Guidelines and reinforcing the deference owed to agency technical judgments on cost and climate analysis under the APA/NEPA framework.

II. Summary of the Opinion

  • Mootness: The case was not constitutionally moot even though the authorized fill discharge was complete, because a remand could still yield partial relief through additional mitigation measures or strengthened permit conditions.
  • CWA § 404(b)(1) “purpose” holding: The Corps may define “overall project purposes” to include multiple related, applicant-specific objectives. “Overall project purposes” is distinct from “basic purpose”; the plural text supports multiple purposes.
  • Cost analysis: The Corps did not act arbitrarily or capriciously in using a 50% contingency multiplier to estimate comparative costs at the screening stage.
  • Climate change: The Corps reasonably discussed climate risks but declined to adopt quantitative modeling due to uncertainty and lack of generally accepted methods for correlating incremental temperature changes to specific streamflow/reservoir impacts in the region.
  • Disposition: The court reversed the district court, vacated the permanent injunction, and remanded with instructions to enter judgment against plaintiffs.

III. Analysis

A. Precedents Cited

1. NEPA’s function and deference

  • Seven Cnty. Infrastructure Coal. v. Eagle County, 605 U.S. 168 (2025)
    The panel relied on Seven Cnty. for two core propositions: (i) NEPA is procedural—meant “to inform agency decisionmaking, not to paralyze it,” and (ii) judicial review of NEPA compliance requires “substantial deference to the agency.” This framing supported the court’s unwillingness to require more granular cost precision or mandatory quantitative climate modeling where the record showed reasoned agency engagement.
  • Dep't of Transp. v. Pub. Citizen, 541 U.S. 752 (2004)
    Cited for baseline NEPA doctrine regarding when an EIS is required versus a FONSI, anchoring the Corps’s decision to proceed with a full EIS here and underscoring NEPA’s procedural architecture.

2. Alternatives analysis under the CWA § 404(b)(1) Guidelines

  • Hillsdale Env't Loss Prevention, Inc. v. U.S. Army Corps of Eng'rs, 702 F.3d 1156 (10th Cir. 2012)
    This is the opinion’s primary in-circuit anchor for the “clearly demonstrate” requirement applicable to non-water-dependent projects under 40 C.F.R. § 230.10(a)(3). The panel emphasized that “clearly demonstrate” does not require the reviewing court to be convinced in the first instance; rather, the question is whether it was arbitrary and capricious for the Corps to find it had clearly demonstrated LEDPA status after taking a “hard look” and reaching a “meaningful conclusion based on the evidence.”

    Hillsdale also supported the court’s mootness analysis: even after construction milestones, remand can still matter because new information could lead to revised decisions and additional mitigation.
  • Greater Yellowstone Coal. v. Flowers, 359 F.3d 1257 (10th Cir. 2004) and Sylvester v. U.S. Army Corps of Eng'rs, 882 F.2d 407 (9th Cir. 1989)
    These cases frame the Corps’s duty to consider the applicant’s objectives in alternatives analysis, while also warning agencies not to define a project so narrowly that alternatives are preordained. The panel used this line of authority to validate a purpose definition that is applicant-informed but still leaves room for real alternatives—pointing to the Corps’s screening record (34 alternatives remaining; only 10 involving Gross Reservoir expansion) as evidence against “purpose as pretext.”
  • 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 the significance of the plural phrasing “overall project purposes,” supporting the conclusion that multiple purposes may be considered.

3. Administrative law standards and technical judgments

  • Am. Wild Horse Campaign v. Raby, 144 F.4th 1178 (10th Cir. 2025) and New Mexico ex rel. Richardson v. Bureau of Land Mgmt., 565 F.3d 683 (10th Cir. 2009)
    These cases supply the opinion’s articulation of arbitrary-and-capricious review: failure to consider an important aspect, contradiction of evidence, implausible explanations, failure to consider relevant factors, or clear error of judgment.
  • Utahns for Better Transp. v. U.S. Dep't of Transp., 305 F.3d 1152 (10th Cir. 2002) and Habitat Educ. Ctr., Inc. v. U.S. Forest Serv., 673 F.3d 518 (7th Cir. 2012)
    Used to reinforce that agencies need not generate “extraordinarily detailed” cost estimates at early stages and must retain discretion about when to stop gathering data and proceed.
  • 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)
    These cases support deference to agency scientific and technical judgments—here, the Corps’s decision not to rely on quantitative climate-streamflow models given uncertainty, data limitations, and model variability in Colorado’s mountainous regions.

4. Mootness and “partial relief” in environmental cases

  • Rio Grande Silvery Minnow v. Bureau of Reclamation, 601 F.3d 1096 (10th Cir. 2010) and Wyoming v. U.S. Dep't of Agric., 414 F.3d 1207 (10th Cir. 2005)
    Provide the “real world effect” test for mootness: whether present relief would have some effect outside the courtroom.
  • Audubon of Kan., Inc. v. U.S. Dep't of Interior, 67 F.4th 1093 (10th Cir. 2023)
    Cited for redressability and the principle that it must persist throughout litigation.
  • WildEarth Guardians v. Pub. Serv. Co. of Colo., 690 F.3d 1174 (10th Cir. 2012)
    Cited for the burden of establishing mootness resting on the party asserting it.
  • 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)
    Central to the holding that completion of a project does not automatically moot NEPA/CWA challenges if some remedy (including operational constraints or mitigation) remains available.
  • Sierra Club v. U.S. Army Corps of Eng'rs, 803 F.3d 31
    Quoted for the proposition that even after construction, courts can still order partial relief such as enjoining operation pending further analysis; this reinforced the panel’s conclusion that mitigation and permit-condition changes are still meaningful relief.
  • Winzler v. Toyota Motor Sales U.S.A., Inc., 681 F.3d 1208 (10th Cir. 2012) and Sierra Club, Inc. v. Bostick, 787 F.3d 1043 (10th Cir. 2015)
    Address prudential mootness. The court acknowledged the doctrine but declined to reach it because it resolved the case on the merits.

5. Appellate jurisdiction and practical finality

  • 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 navigate the administrative-remand rule. Even assuming the district court’s “remand with vacatur” typically would not be final, the court applied the practical-finality exception because a permanent injunction could make issues effectively unreviewable.
  • Save the Colorado v. Spellmon, 50 F.4th 954 (10th Cir. 2022)
    Included as litigation history and jurisdictional context (earlier reversal of dismissal based on the mistaken view that a FERC-related issue controlled).

6. Interpreting regulatory text; limits on deference

  • Ysleta Del Sur Pueblo v. Texas, 596 U.S. 685 (2022) and Henson v. Santander Consumer USA, Inc., 582 U.S. 86 (2017)
    Cited for the interpretive presumption that different wording generally reflects different meaning—supporting distinct meanings for “basic purpose” and “overall project purposes.”
  • Kisor v. Wilkie, 588 U.S. 558 (2019)
    Used to reject any need for Auer deference because the regulation was deemed unambiguous; the panel also noted the EPA’s interpretation had shifted by January 2026 to align with the court’s reading.

B. Legal Reasoning

1. The core interpretive move: “basic purpose” vs. “overall project purposes”

The opinion’s doctrinal centerpiece is its interpretation of 40 C.F.R. § 230.10(a)(2) and § 230.10(a)(3). The Corps treated:

  • “basic purpose” as the irreducible objective used to decide water dependency (here: “to provide supplemental water supply”); and
  • “overall project purposes” as a more specific articulation that may reflect multiple applicant goals (here: increasing firm yield to the Moffat system and addressing system imbalance/overreliance on the South System).

The Environmental Groups urged a single-purpose approach: once the Corps identified the “basic purpose” as increased water supply, it had to treat that as the “overall project purposes” as well. The Tenth Circuit rejected that equation as textually unsound for three principal reasons:

  1. Different terms, different meanings: invoking the general presumption against surplusage/variation-in-language principles.
  2. The plural matters: “overall project purposes” (plural) naturally contemplates multiple purposes.
  3. Functional context: water-dependency analysis requires only a general purpose; practicability/alternatives analysis requires a more precise account of what the project aims to accomplish.

Critically, the court did not hold that any applicant-stated objective may be accepted uncritically. Instead, it found this particular bundling reasonable because the Corps explained the two needs were “interconnected,” and failing to address either would “jeopardize” Denver Water’s ability to meet projected demand.

2. Purpose definition is constrained by the record—“not preordained” alternatives

The opinion also responds to a common CWA/NEPA litigation theme: that agencies define a purpose so narrowly that only the applicant’s preferred project survives. The panel treated this as an evidentiary and process question, not a slogan. It highlighted the Corps’s screening results (34 alternatives after step one; only 10 requiring Gross expansion) to show the purpose definition did not operate as a de facto lock.

3. Cost methodology: comparative screening vs. budgeting precision

On costs, the court emphasized the posture and function of cost estimation within alternatives screening. The Corps used a “relative development cost” approach: capital costs (“rough order of magnitude”) plus contingent costs estimated at 50% of capital costs. The court found the Corps adequately explained why particularized estimates were “implausible” at early stages across 303 proposals, and why a standardized multiplier—validated by comparisons and third-party review— was suitable for comparative evaluation even if not for final budgeting.

4. Climate change: discussion required; quantification not always required

The court treated the climate issue as part of “logistics”/feasibility and NEPA effects analysis, but concluded the Corps reasonably:

  • identified potential climate impacts (earlier peak flows, reduced volumes);
  • explained how those impacts could affect diversion timing and yield;
  • assessed modeling uncertainty and data limitations; and
  • declined quantitative modeling due to lack of “generally-accepted” methods and high regional variability.

The key move is not that climate change is irrelevant; rather, it is that the APA/NEPA standard asks whether the agency’s explanation is reasoned and record-based, not whether the court would demand more modeling. The panel reinforced that scientific disputes in the record do not license a court to “second-guess” an agency’s technical assessment when the agency has given a rational explanation.

5. Mootness: the continuing relevance of mitigation and permit conditions

The opinion’s mootness analysis is practically important for “too-late-to-stop-construction” cases. Even though the specific fill discharge was complete, the court held a remand could still produce meaningful relief through added mitigation or tightened special conditions. This preserves judicial review where post-permit project phases (like reservoir filling/diversion and ancillary environmental impacts) remain.

C. Impact

  • Purpose-and-need drafting under § 404(b)(1): Within the Tenth Circuit, applicants and the Corps gain firmer footing to frame “overall project purposes” as multiple, interrelated objectives—so long as the agency can explain their interconnection and the record shows the definition does not artificially eliminate alternatives.
  • Litigation posture in large infrastructure permitting: Challengers will face a higher hurdle when arguing that multiple project goals must be separated into distinct “projects” for alternatives analysis, especially where the agency documents integrated system needs.
  • Cost screening methodologies: The decision approves, at least on these facts, standardized comparative-cost tools (like contingency multipliers) at early screening stages, reducing the leverage of arguments demanding fine-grained, alternative-specific costing before narrowing the field.
  • Climate analysis under NEPA/CWA practicability: The holding suggests agencies may survive review without quantitative climate modeling where uncertainty, data limits, and model variability are documented—provided the agency acknowledges climate risks and offers a reasoned justification for methodological choices.
  • Mootness in post-construction disputes: The “partial relief” analysis strengthens the ability of plaintiffs to keep claims alive even after substantial completion, while simultaneously giving agencies and applicants a litigation roadmap: demonstrate that remaining relief would be marginal or speculative (prudential mootness), or win on the merits with deference.

IV. Complex Concepts Simplified

  • § 404(b) permit / fill material: The CWA treats placing rock/soil (“fill”) into federally regulated waters as pollution unless authorized by a permit. A dam expansion often requires such fill in streams or wetlands.
  • LEDPA (Least Environmentally Damaging Practicable Alternative): The Corps may permit a discharge only if no other alternative is both (i) practicable and (ii) less harmful to aquatic ecosystems (and without other significant adverse environmental consequences).
  • Non-water-dependent project presumption: If a project’s basic purpose does not require being in water (unlike, say, a marina), the regulations presume less-damaging practicable alternatives exist unless the Corps clearly demonstrates otherwise.
  • “Basic purpose” vs. “overall project purposes”: “Basic purpose” is the irreducible aim used to decide if the project must be in/near water. “Overall project purposes” are the more detailed objectives used to judge whether alternatives are practicable.
  • NEPA EIS: An Environmental Impact Statement is a disclosure document: it must analyze significant impacts and reasonable alternatives, but it does not force the agency to pick the least damaging option.
  • Arbitrary-and-capricious review: Courts do not decide whether the agency made the “best” choice; they decide whether the agency considered relevant factors, explained itself, and stayed within the bounds of reasoned decisionmaking.
  • Constitutional vs. prudential mootness: Constitutional mootness asks whether any court-ordered relief can still help. Prudential mootness asks whether relief is so limited that deciding the case is not worth it (a discretionary doctrine).

V. Conclusion

Save The Colorado v. Graham establishes an important clarification for CWA § 404(b)(1) alternatives analysis in the Tenth Circuit: the Corps may define “overall project purposes” to include multiple, interconnected applicant objectives, distinct from the project’s “basic purpose.” The decision also underscores robust deference to agency judgments on comparative cost methodologies and on whether quantitative climate modeling is warranted, so long as the agency acknowledges the issue and explains its methodological choices in the record.

Practically, the opinion strengthens agency flexibility in framing purpose-and-need and in conducting early-stage screening for large infrastructure projects, while signaling to challengers that successful attacks will require showing not merely that more analysis was possible, but that the agency’s choices were irrational, unexplained, or record-contradicted under the APA’s demanding standard.