Columbia-Pacific Northwest Region

Conconully Safety of Dams Modification Project Environmental Assessment

Final Environmental Assessment
FONSI-Decision Record

Aerial view of Conconully Dam, Okanogan Project, Washington

The Bureau of Reclamation published the finding of no significant impact and decision record for the Conconully Safety of Dams Modification project on March 13, 2026. The final environmental assessment was published on Nov. 20, 2025. The project proposes to reduce the seismic risks of dam failure, provide water deliveries and flows for irrigators and endangered species, and maintain additional benefits for recreation and fish and wildlife habitat.

Reclamation selected a modified Alternative C alternative for implementation. The modified Alternative C alternative would implement all project components of Alternative C in addition to the boat ramp described under Alternative B. The selected alternative includes constructing a stability berm on the downstream face of the dam, supported by deep soil mix reinforcement columns. It also includes upgrading the outlet works by extending, lining and reinforcing water conveyance components, and by installing modern water control systems and facilities—including multiple state-of-the-art valves and a new valve house.

These modifications are intended to:

• Address public safety concerns and ensure the long-term functionality of the facilities.
• Implement cost-effective measures to reduce long-term performance risks, in line with Reclamation’s public protection guidelines.
• Maintain water deliveries and flows for irrigators and endangered species.
• Continue supporting recreation and fish and wildlife habitat

Finding of No Significant Impact and Decision Record

03/2026	Conconully Safety of Dams Modification Project Finding of No Significant Impact and Decision Record PDF 636KB
10/2025	Conconully Safety of Dams Modification Project Final Environmental Assessment PDF 31MB

Final Resource Reports and Memos

10/2025	Air Quality Memo PDF 312KB
10/2025	Geology Memo PDF 211KB
10/2025	Land Use Memo PDF 200KB
10/2025	Public Health and Safety Memo PDF 1.97MB
10/2025	Socioeconomics Memo PDF 254KB
10/2025	Transportation Memo PDF 208KB
10/2025	Utilities Memo PDF 1.48MB
10/2025	Vibration Memo PDF 1.77MB

News Releases

6/2025	Reclamation seeks public comment on draft environmental document for Conconully Dam safety modifications
8/2024	Reclamation seeks public comment on Conconully Dam modifications