Columbia-Pacific Northwest Region

Conconully Safety of Dams Modification Project Environmental Assessment

Final Environmental Assessment

Aerial view of Conconully Dam, Okanogan Project, Washington

The Bureau of Reclamation published the final environmental assessment for the Conconully Safety of Dams Modification project on Nov. 20, 2025. The preferred alternative addresses issues important to public safety and the long-term functionality of the facilities and includes constructing a stability berm on the downstream face of the dam, which will be supported by deep soil mix reinforcement columns. Additionally, the outlet works would be upgraded 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

Final Environmental Assessment

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