SOS argued TCEQ effectively “collapsed” Tier 2 into Tier 1 by focusing only on existing uses and failing to conduct a distinct Tier 2 water‑quality analysis. The Court disagrees, noting:

• There is substantial overlap between Tier 1 and Tier 2, because both protect existing uses and water quality sufficient to support those uses.
• Nevertheless, TCEQ’s order expressly referenced both:
  • Maintenance of existing uses; and
  • Absence of “significant degradation of water quality” and protection of waters exceeding fishable/swimmable quality.
• Findings such as:
  • FOF 78 (antidegradation ensures no impairment of uses and no degradation of water quality),
  • FOF 88 (antidegradation satisfied because DO will be maintained at levels supporting healthy aquatic life and phosphorus limits will protect high‑quality waters), and
  • FOF 90 (Tier 2 review confirmed no significant degradation is expected and existing uses will be maintained)
  demonstrate a dual focus consistent with both tiers’ text.

The Court also notes TCEQ was not required to parrot the precise phrase “no more than a de minimis extent” in its findings, so long as the substance of that standard was applied—which, in the Court’s view, it was.

IV. Standard of Review and Deference to TCEQ

A. Substantial Evidence and Arbitrary‑and‑Capricious Review

Under APA §§2001.171 and 2001.174, the reviewing court may not substitute its judgment for the agency’s on the weight of the evidence. It must reverse or remand only if the agency’s decision:

• Violates the law,
• Lacks substantial evidence, or
• Is arbitrary or capricious or an abuse of discretion.

Relying on cases such as Mireles, Ammonite Oil & Gas, and NEISD v. Riou, the Court reiterates that:

• Substantial evidence review is a “reasonableness” or “rational basis” test, not a correctness test.
• Agency findings and decisions are presumed valid; the burden is on the challenger (here, SOS) to overcome the presumption.
• Courts may not re‑weigh expert testimony or substitute their policy preferences for those of the agency in its field of expertise.

Arbitrariness review is distinct: the court asks whether the agency:

• Failed to consider mandatory factors,
• Considered irrelevant factors,
• Reached a completely unreasonable result, or
• Failed to follow its own rules.

SOS framed much of its attack as arbitrariness based on alleged misapplication of antidegradation rules, but given the Court’s acceptance of TCEQ’s whole‑water reading, that contention fails.

B. Crediting TCEQ’s and the City’s Experts

The ALJ’s PFD expressly found TCEQ’s and the City’s experts “more compelling and reliable” than SOS’s experts, who lacked experience with Texas’s water‑quality standards and models (such as QUAL‑TX). The Court emphasizes:

• This is precisely the kind of technical weighing of evidence entrusted to the agency and its fact‑finder, not to the courts.
• The district court erred in treating certain nutrient‑increase projections as “undisputed” and outcome‑determinative when the ALJ had declined to credit those projections, and the court of appeals rightly corrected that error.

As to DO, one City model showed a possible 4.87 mg/L at the discharge point, while:

• TCEQ’s modeling under worst‑case conditions showed DO staying at or above 5.0 mg/L; and
• All modeling assumed a higher discharge volume (995,000 gpd) than the final permitted volume (822,500 gpd), making TCEQ’s results conservative.

Under substantial evidence review, TCEQ was not required to accept the lowest modeled value over its own analyses.

C. The Prima Facie Case and Burden‑Shifting in Contested‑Case Hearings

Under Gov’t Code §2003.047(i‑1)–(i‑3) and 30 TAC §80.17(c), once the administrative record is admitted:

• There is a prima facie case that the draft permit:
  • Meets all state and federal legal and technical requirements, and
  • Will protect human health, safety, the environment, and property.
• The protestant must rebut that presumption by evidence that the draft permit violates a specifically applicable legal requirement.

The Court notes that SOS’s reading of Water Code §26.027 and APA §2001.141, if adopted, would invert this structure by forcing TCEQ to affirmatively make detailed compliance findings for every conceivable legal standard in every order. That would conflict with §2003.047’s presumption and burden‑shifting design and is therefore rejected.

V. The APA §2001.141 “Underlying Facts” Requirement

A. Basic vs. Ultimate Findings

APA §2001.141(b) requires a final order to include separately stated:

• Findings of fact, and
• Conclusions of law.

Section 2001.141(d) adds that when a finding of fact is stated in “statutory language,” the order must also provide “a concise and explicit statement of the underlying facts supporting the finding.”

Texas case law (notably Charter Medical–Dallas and Western Texas Utilities) distinguishes between:

• Basic facts (underlying facts)—concrete, specific factual determinations (e.g., discharge volume, baseline pollutant levels); and
• Ultimate facts—inferences drawn from basic facts that typically mirror statutory or rule‑based criteria (e.g., “the project is needed,” “the permit protects water quality”).

If an ultimate fact is expressed in statutory language embodying a legislatively mandated criterion, the agency must articulate underlying facts sufficient to allow a reviewing court to see how the ultimate conclusion was reached.

B. Preservation: Specific Objections Required

The Court holds that SOS forfeited its APA findings challenge by failing to raise it with adequate specificity in its motion for rehearing before TCEQ. Drawing on Hooks and BFI Waste Systems v. Martinez, it explains:

• A party must identify which findings are allegedly incomplete and what underlying facts are missing.
• Generalized assertions that an order lacks “underlying facts” are insufficient; they deprive the agency of a fair opportunity to correct or explain any deficiency.

SOS’s rehearing motion contained only generalized complaints; its detailed articulation of the supposedly “minimally required findings” (e.g., baseline and post‑discharge levels of nutrients and DO, percentage change, explicit de minimis determination) appears for the first time in judicial briefing, too late to preserve error.

C. Are the Antidegradation Findings “Statutory Language”? No.

Even assuming preservation, the Court concludes §2001.141(d) is not triggered here because TCEQ’s antidegradation findings are not “set forth in statutory language.”

Key points:

• The “statutory language” clause refers to findings that restate text actually contained in a statute, particularly legislatively mandated criteria that an agency must apply.
• In Charter Medical–Dallas, the enabling statute required the agency to consider specific criteria in deciding whether to issue a certificate of need; findings mirroring those statutory criteria had to be supported by underlying facts.
• By contrast, Water Code §26.027(a)–(b) simply authorizes TCEQ to issue or deny discharge permits and to refuse permits that would “violate the provisions of any state or federal law or rule.” It does not:
  • Enumerate specific criteria that must be found to issue a permit; or
  • Require TCEQ to make individual, negative findings that a permit does not violate each and every law or rule.
• TCEQ’s antidegradation standards are found in its rules (30 TAC §307.5) and IPs, not in the Water Code itself.

Thus, the Court holds that:

• Antidegradation‑related findings (e.g., that no significant degradation is expected, existing uses will be maintained, DO levels will support healthy aquatic life) are regulatory, not statutory, and so do not fall within §2001.141(d).
• Requiring underlying facts whenever an agency applies its rules (instead of only when it restates statutory criteria) would vastly expand the APA requirement beyond the legislature’s intent.

D. Avoiding Absurd and Unworkable Results

The Court also invokes the canon against absurd results. If SOS’s reading of §26.027 and §2001.141 were adopted:

• TCEQ would effectively have to include detailed, underlying fact findings demonstrating compliance with every applicable federal and state law and rule in every permit order.
• This would be administratively unmanageable and conflict with the presumption and burden structure in §2003.047, which assumes the permit is valid unless the protestant proves a specific legal violation.

The Court therefore rejects SOS’s construction as unreasonable and inconsistent with the statute’s design.

It concludes that TCEQ’s order:

• Satisfies §2001.141(b) by separately stating findings of fact and conclusions of law; and
• Includes sufficient factual detail—in the findings themselves and the incorporated ED responses—to apprise the parties and courts of the basis for TCEQ’s antidegradation determinations.

VI. Precedents and Authorities Cited

A. Texas Administrative Law and TCEQ Cases

• Dyer v. TCEQ, 646 S.W.3d 498 (Tex. 2022).
  Cited to confirm that under Gov’t Code §2003.047(m), TCEQ may revisit the SOAH record, reweigh the evidence, and amend the ALJ’s proposed findings so long as it stays within the record and explains its changes. This reinforces TCEQ’s authority to adopt and adjust the PFD, which it did here with only minor modifications.
• TCEQ v. Maverick County, 642 S.W.3d 537 (Tex. 2022).
  Provides the interpretive principle that courts must apply the plain text of agency rules without adding or subtracting substantive terms—a principle the Court uses to refuse SOS’s attempt to rewrite “water quality” as “any individual parameter.”
• Wood v. TCEQ (Tex. App. 2015, no pet.).
  Supports the proposition that antidegradation can be assessed using narrative, qualitative criteria without requiring quantified evidence for every impact, consistent with TCEQ’s approach here.
• TCEQ v. City of Waco, 413 S.W.3d 409 (Tex. 2013).
  Recognizes that qualitative standards (e.g., “too much” of a constituent) involve subjective judgment, contrasting with rigid numeric thresholds. This aligns with the Court’s acceptance of a narrative antidegradation assessment.

B. Standard‑of‑Review Cases

• Mireles v. Texas Department of Public Safety, 9 S.W.3d 128 (Tex. 1999). – Used to frame substantial evidence review as a rational basis inquiry.
• Ammonite Oil & Gas Corp. v. Railroad Commission, 698 S.W.3d 198 (Tex. 2024). – Cited for the modern articulation of substantial evidence deference.
• N.E. ISD v. Riou, 598 S.W.3d 243 (Tex. 2020). – Emphasizes that courts must not usurp agency adjudicative authority.
• PUC v. Texas Industrial Energy Consumers, 620 S.W.3d 418 (Tex. 2021). – Reaffirms the presumption of validity for agency decisions.
• City of El Paso v. PUC, 883 S.W.2d 179 (Tex. 1994) & PUC v. Gulf States Utilities, 809 S.W.2d 201 (Tex. 1991). – Outline arbitrariness standards (failure to consider required factors, consideration of irrelevant ones, unreasonable results, or violation of agency rules).

C. APA and Fact‑Finding Cases

• Texas Health Facilities Comm’n v. Charter Medical–Dallas, Inc., 665 S.W.2d 446 (Tex. 1984). – Foundational case defining when “underlying facts” are required: when the agency’s findings use statutory criteria mandated by the legislature.
• Texas Health Facilities Comm’n v. Presbyterian Hospital North, 690 S.W.2d 564 (Tex. 1985). – Application of Charter; agency’s recitation‑style findings and conclusory statements were insufficient.
• Western Texas Utilities Co. v. Office of Public Utility Counsel, 896 S.W.2d 261 (Tex. App.—Austin 1995, no writ). – Clarifies the distinction between basic and ultimate facts and when underlying facts must be provided.
• Hooks v. Texas Department of Water Resources, 645 S.W.2d 874 (Tex. App.—Austin 1983, writ ref’d n.r.e.). – Held that generalized complaints about omitted findings are insufficient to preserve error; specific omissions must be identified in the motion for rehearing.
• BFI Waste Systems of North America, Inc. v. Martinez Environmental Group, 93 S.W.3d 570 (Tex. App.—Austin 2002, pet. denied). – Similar preservation holding; also notes that not every ultimate fact requires detailed supporting findings.

D. Federal Environmental Cases

The Court distinguishes the federal authorities SOS cites:

• County of Maui v. Hawaii Wildlife Fund, 590 U.S. 165 (2020). – Interprets when discharges through groundwater require NPDES permits; not about state antidegradation methodologies.
• Arkansas v. Oklahoma, 503 U.S. 91 (1992). – Concerns interstate water pollution and federal‑state coordination, not Texas’s internal implementation standards.
• Kentucky Waterways Alliance v. Johnson, 540 F.3d 466 (6th Cir. 2008). – Addresses EPA’s approval of state rules that categorically exempt certain discharges from Tier 2 review; not about whole‑water vs parameter‑based approaches.
• Greater Yellowstone Coalition v. EPA, 2013 WL 1760286 (D. Idaho). – Involves a state’s attempt to use an automatic 10% assimilative‑capacity exemption from Tier 2; not an issue here.

These cases deal with different structural challenges or federal approval of state programs. None dictate the internal form of Texas’s Tier 2 test, especially where EPA has expressly approved TCEQ’s approach.

VII. Key Legal Concepts Simplified

A. Antidegradation Tiers

• Tier 1: Protects existing uses and the water quality sufficient to support them. No degradation allowed that would impair those uses.
• Tier 2: Applies to waters cleaner than fishable/swimmable. Prohibits more‑than‑de minimis lowering of water quality even if uses remain unimpaired, unless necessitated by important economic or social development (an exception not invoked here).
• Tier 3: Protects “outstanding national resource waters” from almost any degradation; not at issue in this case.

B. Narrative vs Numeric Criteria

• Numeric criteria are specific numbers (e.g., DO ≥ 5.0 mg/L) that must be met.
• Narrative criteria are general prohibitions (e.g., “no excessive algal growth that impairs uses”), requiring expert judgment and contextual evaluation.

Texas uses both. Numeric criteria are used heavily in modeling, but final antidegradation conclusions are often narrative and integrative.

C. Assimilative Capacity

“Assimilative capacity” is essentially the room a water body has to accept additional pollutants without violating standards. A large assimilative capacity means that modest increases in pollutant load might have no practical effect on uses or water quality.

Texas’s IPs:

• Use assimilative‑capacity percentages as screening tools, not automatic legal thresholds; and
• Exclude DO from certain generic assimilative‑capacity screens, reflecting DO’s sensitivity and complexity.

D. “De Minimis” Changes

“De minimis” changes are too small to matter in a regulatory sense—so minor that they do not meaningfully lower water quality or impair uses. The Court:

• Does not fix a numeric benchmark for what is de minimis; and
• Affirms TCEQ’s discretion to judge de minimis in context, based on expert evidence and site‑specific conditions.

E. Substantial Evidence

Substantial evidence does not mean the most or even more than half of the evidence; it means:

• Some reasonable amount of relevant evidence that a reasonable mind could accept as sufficient to support the agency’s conclusion,
• Even if there is conflicting evidence pointing the other way.

The reviewing court:

• Looks at the record as a whole,
• Does not re‑weigh evidence or assess credibility, and
• Asks only whether the agency’s decision has a rational basis in the evidence.

VIII. Likely Impact of the Decision

A. For TCEQ and Future Permitting

• The Court explicitly validates TCEQ’s long‑standing practice of assessing antidegradation on a waterbody‑by‑waterbody, qualitative basis, informed by multiple parameters.
• TCEQ is not required to adopt parameter‑based per se rules for what counts as “degradation,” nor to treat any more‑than‑de minimis shift in a single parameter as automatically disqualifying.
• As long as TCEQ:
  • Follows its promulgated rules and IPs,
  • Builds a record with modeling and expert testimony showing no more‑than‑de minimis lowering of water quality overall, and
  • Articulates its reasoning in findings and responses to comments,
  its Tier 2 determinations will be difficult to overturn under substantial evidence and arbitrariness review.

B. For Municipalities and Permit Applicants

Cities and other applicants gain greater clarity:

• They can rely on TCEQ’s established modeling and qualitative methodologies knowing the Supreme Court has endorsed them.
• They should still expect stringent effluent limits and mitigation measures (e.g., low‑nutrient limits, disinfection, flow and infrastructure conditions) as TCEQ tailors permits to satisfy Tier 1 and Tier 2.
• Demonstrating efforts to reduce or nearly eliminate discharges (e.g., beneficial reuse, storage expansions) strengthens the case that permitted discharges will not significantly lower water quality.

C. For Environmental Organizations and Opponents of Permits

The decision significantly raises the bar for challengers:

• Showing predictive increases in individual pollutants or decreases in DO is no longer sufficient by itself to prove a Tier 2 violation.
• Challengers must instead marshal expert testimony and site‑specific evidence showing that:
  • The overall water quality of the segment will be measurably lowered more than de minimis, and/or
  • Existing uses will be impaired despite compliance with numeric criteria.
• To attack agency findings under the APA, opponents must:
  • Identify specific omitted findings and underlying facts in their motions for rehearing before the agency; and
  • Focus on statutory criteria where §2001.141(d) applies, not merely regulatory standards.

Strategically, environmental groups may increasingly:

• Direct energy toward rulemaking (seeking changes in the text of §307.5 or the IPs) rather than only permit challenges; and
• Develop richer biological, ecological, and site‑specific evidence to show that certain waters warrant Tier 3‑like treatment or stricter criteria.

D. For Texas Administrative Law Generally

The decision reinforces several broader themes:

• Textualism in rule interpretation: Courts will adhere to the plain language of agency rules and resist importing unstated federal guidance concepts.
• High deference in technical domains: Agencies like TCEQ get significant leeway in modeling, expert judgment, and narrative standards.
• Constrained scope of APA §2001.141(d): The “underlying facts” requirement remains focused on statutory criteria the Legislature has mandated, not every regulatory standard an agency applies.
• Strict preservation demands: Parties must carefully use motions for rehearing to identify both legal and factual issues with specificity, or risk forfeiture on judicial review.

IX. Conclusion: Key Takeaways

Save Our Springs Alliance, Inc. v. TCEQ & City of Dripping Springs crystallizes two important doctrinal points in Texas environmental and administrative law:

1. Whole‑Water Antidegradation Standard.
   Tier 2 antidegradation under 30 TAC §307.5 focuses on “lowering of water quality” as an integrated concept, not on isolated numeric changes in particular parameters. TCEQ is entitled to:
   • Evaluate multiple parameters (DO, nutrients, bacteria, etc.),
   • Apply narrative and qualitative criteria,
   • Use assimilative‑capacity and other screens as guides rather than automatic rules, and
   • Exercise context‑specific expert judgment in deciding whether any lowering of water quality is more than de minimis.
2. Limited APA “Underlying Facts” Obligation.
   TCEQ’s antidegradation findings are not findings “set forth in statutory language,” and therefore do not trigger APA §2001.141(d)’s requirement for explicit statements of underlying facts, beyond the substantial factual detail already provided in the order and incorporated responses to comments. Moreover, challengers must timely and specifically raise any alleged omissions via motion for rehearing to preserve such issues for judicial review.

In upholding the Dripping Springs permit, the Court confirms TCEQ’s considerable discretion to balance environmental protection with municipal needs under its EPA‑approved framework, while simultaneously reinforcing deference to agency expertise and insisting on disciplined statutory and rule‑based analysis in judicial review. For practitioners, regulators, and stakeholders, this decision sets a clear precedent: challenges to water discharge permits must engage directly with TCEQ’s holistic conception of “water quality,” rather than relying solely on parameter‑level changes or generic appeals to federal policy.