Washington Court Requires Explicit Leakage Monitoring in CWA § 401 Certification

Key Takeaways

• What Happened: On September 21, 2026, the Washington Court of Appeals in Columbia Riverkeeper v. Pollution Control Hearings Board, (Wash. Ct. App. Sept. 21, 2026), largely upheld a Clean Water Act (CWA) Section 401 water quality certification for the proposed Goldendale Energy Storage Project, a proposed 1,200-megawatt pumped-storage hydroelectric facility, but set aside the certification on one issue. The court held that the certification did not explicitly require monitoring and reporting to detect leakage from the project’s closed-loop system and tunnels.
• Who’s Impacted: Developers and operators of federally licensed or permitted projects requiring Section 401 water quality certification in Washington, particularly hydropower, energy storage, and other projects involving underground infrastructure, groundwater, or potential seepage pathways, as well as projects requiring a CWA Section 404 dredge-and-fill permit.
• Next Steps: Applicants should confirm that Section 401 certifications and incorporated monitoring plans expressly identify required monitoring and reporting for potential discharge pathways. Evidence that a project can or will monitor a potential discharge may not suffice if the certification itself does not explicitly set forth that requirement. Applicants should also be aware that EPA has proposed rules that, if adopted, will impose significant limits on the scope of state authority under Section 401.

Court Largely Upholds Certification for Goldendale Energy Storage Project

Under CWA Section 401, any development that would result in any discharge into a waterway within a state must obtain a certification from the relevant state, which the state may grant, deny, or condition. In this case, the Court of Appeals reviewed the Washington Department of Ecology’s (Ecology) Section 401 water quality certification for the proposed Goldendale Energy Storage Project. The project would operate as a closed-loop pumped-hydropower energy storage system near the Columbia River in Klickitat County, Washington, on a site proposed for pumped-hydro storage for many years. Water would move between upper and lower reservoirs through underground tunnels and a powerhouse. The lower reservoir would sit on the site of the former Goldendale aluminum smelter with existing contamination concerns.

Ecology issued the Section 401 certification in May 2023. Columbia Riverkeeper and the Confederated Tribes and Bands of the Yakama Nation challenged the certification before the Pollution Control Hearings Board (PCHB), which affirmed it in January 2025.

On appeal, Riverkeeper and the Yakama Nation raised several issues, including whether the project could leak into groundwater connected to the Columbia River and whether the certification included adequate conditions and monitoring requirements. The Court of Appeals rejected most of those challenges, finding that PCHB adequately evaluated the project and identified sufficient evidence that leakage is unlikely due to the project’s double-lining design.

Substantial Evidence Supported Ecology’s Conclusion That the Project Was Designed to Avoid Leakage

The challengers relied heavily on the project’s Environmental Impact Statement, which had assumed that approximately 100 acre-feet of water per year could leak from underground project infrastructure. PCHB, however, credited later evidence developed during the Section 401 certification process. Experts testified about design measures intended to prevent or minimize leakage, including reservoir liners, leak-detection systems, pressure grouting, reinforced concrete or steel tunnel liners, and other construction techniques.

The Court of Appeals concluded that substantial evidence supported PCHB’s finding that the project was designed to avoid leakage and that any seepage would likely be nominal. The court emphasized that PCHB could consider evidence available at the time of its hearing and was not limited to assumptions made earlier in the environmental review process.

That conclusion also affected the challengers’ argument under County of Maui v. Hawaii Wildlife Fund. The U.S. Supreme Court held in County of Maui that the CWA can apply when a discharge through groundwater is the “functional equivalent” of a direct discharge to navigable waters. The Washington court concluded that PCHB did not need to conduct that analysis here because substantial evidence supported its finding that the project would not result in significant leakage to groundwater and that any potential contamination would not reach the Columbia River.

For Section 401 applicants, the decision underscores the value of developing a detailed technical record during the permitting process. Early environmental-review assumptions may not control if later engineering and technical information supports different conclusions.

Monitoring Commitments Must Appear in the Certification

The court reached a different conclusion concerning monitoring for leakage from the project’s tunnels.

PCHB had found that the project’s closed-loop design would allow the operator to monitor for leakage by comparing expected water losses from evaporation and mitigation discharges with actual system losses. An Ecology witness also testified that the project could monitor seepage. But the Court of Appeals found a critical gap: neither the Section 401 certification nor the project’s water quality monitoring plan expressly required the operator to monitor and report changes in water quantity that could indicate tunnel leakage.

The court therefore held that evidence did not support PCHB’s finding that tunnel leakage would be monitored and reported. The court set aside the certification only on that issue and remanded the matter so Ecology and the PCHB could impose monitoring and reporting requirements that could detect leakage from the tunnels.

This distinction is important for Section 401 permit applicants. A technical record showing that monitoring is feasible, contemplated, or expected does not necessarily substitute for an enforceable permit condition requiring that monitoring. Applicants should consider whether their certifications and incorporated plans clearly specify:

• What potential discharge or leakage pathways must be monitored.
• What parameters must be measured.
• Where and how monitoring must occur.
• How frequently monitoring must occur.
• What results must be reported to the certifying agency.
• What follow-up actions apply if monitoring identifies unexpected leakage or water quality impacts.

Aligning the permit language with the technical record can reduce disputes over whether monitoring obligations actually apply.

Court Declines to Extend San Francisco v. EPA NPDES Holding to Section 401

The challengers also argued that a certification condition prohibiting violations of applicable water quality standards conflicted with the U.S. Supreme Court’s 2025 decision in San Francisco v. EPA. In San Francisco, the Supreme Court held that EPA could not impose certain “end-result” conditions in a National Pollutant Discharge Elimination System permit under Section 402 of the Clean Water Act. The Court focused in part on how those conditions interacted with Section 402’s statutory permit shield.

The Washington Court of Appeals declined to extend that holding to the Section 401 certification. It noted that San Francisco addressed Section 402 permits and did not decide whether similar provisions were permissible or sufficient under Section 401. Accordingly, the decision leaves Ecology room to use water quality-based conditions in Section 401 certifications while reinforcing the need for specific monitoring provisions where the record identifies potential uncertainty.

Importance of the Decision for Washington’s Energy Transition

Along with the Federal Energy Regulatory Commission’s recent decision to grant a 40-year license to the Goldendale project, the Court of Appeal’s decision is a significant step toward the beginning of construction at a site that has been proposed for pumped storage for at least two decades. A significant expansion of energy storage capacity in the Pacific Northwest is critical to achieving Washington’s climate and decarbonization goals, which include the Climate Commitment Act’s goal of reducing the state’s GHG emissions to 90 percent below 1990 levels by 2050 and the Clean Energy Transformation Act’s goal of eliminating GHG-emitting power resources from Washington’s electric sector by 2045. Meeting these goals will require a major expansion of energy storage, both to integrate larger amounts of variable wind and solar resources onto the grid and to reduce pressure on an already-strained electric transmission system. Pumped storage is particularly important because it provides longer-term energy storage not available from current utility-scale battery storage technologies. And the Goldendale project is a major step forward in this respect because it is located in the Columbia Gorge, the heart of the Northwest’s wind energy industry. 

Next Steps for Section 401 Applicants

Project proponents should review Section 401 certifications together with their supporting monitoring plans, rather than treating those documents separately. Where the administrative record discusses a potential discharge pathway, applicants should confirm that the final certification clearly addresses how the project will detect, monitor, and report it. Applicants should also maintain a record explaining how project design changes or more refined technical information affect assumptions made during earlier environmental review. This decision shows that later-developed evidence can support an agency’s conclusions, but the operative certification must still include the monitoring requirements needed to support those conclusions.

With an office in Seattle, Beveridge & Diamond’s water, energy, and litigation lawyers advise clients on Clean Water Act permitting, Section 401 water quality certifications, administrative appeals, and environmental review for complex infrastructure and energy projects. For more information on this development, please contact the authors.