Mill Creek Project O&M SEA

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The U.S. Army Corps of Engineers, Walla Walla District (USACE) has completed a Supplemental Environmental Assessment (SEA) in accordance with the National Environmental Policy Act (NEPA) associated with the Mill Creek Flood Control Project 1975 Operations and Maintenance (O&M) Environmental Impact Statement (EIS).

The SEA replaced the 2018 Mill Creek O&M Supplemental Environmental Impact Statement (SEIS) because concerns and issues of likely significance to the O&M of the Project were addressed and resolved in the Mill Creek General Investigation Study. This change was coordinated with Northwestern Division environmental staff and the USACE Office of Counsel. The Notice of Intent (NOI) to prepare a SEIS is being withdrawn. The appendices refer to the SEIS however are applicable to the SEA. The purpose of the SEA is the continuation of the O&M of the Mill Creek Project (Project) for the authorized purposes of flood risk management, as required by the original Project authorization (Public Law (PL) 75-761) and applicable regulations, and recreation (PL 78-534), while addressing environmental effects and avoiding or minimizing effects to Endangered Species Act-listed fish and associated critical habitat and incorporating operational and structural changes. The purpose is to maintain flood risk management and recreational missions, while protecting natural and cultural resources at the Project. While preparing the SEA, USACE did not identify any impacts that would significantly affect the quality of the human environment. Full compliance with NEPA has been achieved and the SEA and the signed FONSI are posted here.