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On March 5, 2026, the Wyoming Department of Environmental Quality (WDEQ) issued a Clean Water Act Section 401 Water Quality Certification for the Black Canyon Hydro, LLC Seminoe Pumped Storage Project near Rawlins, Wyoming.
Section 401 of the Clean Water Act provides states with authority to review and certify that discharges proposed under federal permits or licenses will protect the state’s water quality. The WDEQ’s issuance of the Section 401 certification fulfills Black Canyon Hydro, LLC’s obligation to obtain this certification in accordance with federal and state requirements. WDEQ’s 401 certification is only one of many permits, licenses, or authorizations that Black Canyon Hydro, LLC will need to obtain for the project, and WDEQ’s certification only pertains to the state’s authority to review and certify with conditions that the project will meet state water quality standards. Black Canyon Hydro, LLC will need to obtain all other applicable permits, licenses, or authorizations that are required by local, state, and federal laws or regulations.
The issuance of the certification follows WDEQ’s review of Black Canyon Hydro, LLC’s request for state certification of the Federal Energy Regulatory Commission Hydropower License (Project No. 14787) and U.S. Army Corps of Engineer’s Individual Permit (NWO-2022-01415) for the Seminoe Pumped Storage Project to ensure the project complies with Chapter 1, Wyoming Water Quality Rules (Wyoming Surface Water Quality Standards). The project is a 972-megawatt pumped hydro energy storage facility that involves the construction of a new upper reservoir near Seminoe Reservoir along with a water conveyance and maintenance tunnel system, underground powerhouse, access bridge, and transmission corridor. Normal project operations would involve cycling water between the upper reservoir and Seminoe Reservoir to generate power, with daily cycling volumes dependent on utility needs and overall grid demand.
Discharges of dredged or fill material during construction will affect 0.16 acres of Kortes Reservoir (for the access bridge), 2.0 acres of Seminoe Reservoir (for the inlet-outlet structure and associated rockfill blanket), and 1.48 acres of wetland (for the upper reservoir). To minimize impacts to surface water quality, best management practices, including installation of a sediment curtain and a bubble wall around the inlet-outlet construction area, will be implemented.
During project operations, discharges of water used for power generation may temporarily influence water quality in Seminoe Reservoir, Kortes Reservoir, and the North Platte River’s “Miracle Mile” segment below Kortes Dam. This influence is primarily due to short-term temperature changes during drought conditions and resuspension of a marginal volume of reservoir bed sediment during project startup. The “Miracle Mile” segment is designated as an Outstanding Resource Water under Wyoming Surface Water Quality Standards, which requires the existing quality at the time of its designation to be maintained and protected. To address these influences before they occur and ensure compliance with Wyoming Surface Water Quality Standards, an adaptive management plan was developed. This plan, which includes monitoring, threshold-triggered operational restrictions and protections, feedback loops, and reporting, is integrated as enforceable conditions of the certification.
On January 2, 2026, WDEQ released the draft 401 water quality certification, draft adaptive management plan and associated technical and modeling reports for a 30-day public comment period. The WDEQ held an in-person public meeting in Casper on January 21, 2026 and a virtual public meeting on January 28, 2026 to receive additional public comment. WDEQ considered all comments received during the public comment period and made revisions to the draft certification in response to public comments before issuing a final decision on the certification.
Final Certification
Final Adaptive Management Plan
Response to Comments
Written Comments Received by WDEQ
Para español, visite deq.wyoming.gov. Americans with Disabilities Act: special assistance or alternative formats will be made available upon request for individuals with disabilities. Please provide at least fourteen (14) days before the close of the public comment period for such requests.
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