Corps of Engineers releases Mud Mountain Dam Fish Passage Project Environmental Assessment

Published May 6, 2015

SEATTLE – Pursuant to the National Environmental Policy Act, the U.S. Army Corps of Engineers has released the Environmental Assessment and Finding of No Significant Impact for Mud Mountain Dam Fish Passage Project.  

The EA describes the proposed project, the likely effects on the environment, the alternative actions considered, and the project’s positive benefits to the watershed and fish listed under the Endangered Species Act in the project area.  The draft EA was open to public comment from March 19 to April 17, 2015.  The Corps received comments from nine entities, which were generally supportive of the project; the Corps appropriately addressed each comment in Appendix C of the EA. The FONSI documents the Corps’ determination that it is not necessary to prepare an Environmental Impact Statement for the proposed action.

The Mud Mountain Adult Fish Passage Facility is mitigation for the loss of fish passage due to the construction of Mud Mountain Dam, which was completed in 1941.  The project is in Pierce and King counties near the cities of Enumclaw and Buckley at River Mile 24.3 on the White River.  The White River is a tributary of the Puyallup River and enters the Puyallup about 10 miles above the river’s mouth at Tacoma on Commencement Bay, Puget Sound.    

The project replaces a 100-year-old barrier structure and a 70-year-old fish trap; construction is scheduled to be completed in 2020.  The replacement is designed to pass more than 1 million fish annually to ensure fish are passed in a safe, timely and effective manner. 

To implement the actions recommended by the National Marine Fisheries Services in their October 7, 2014, Biological Opinion, the Corps has undertaken interim repairs to the existing fish trap facility and barrier.  The Corps has already completed some repairs to the flashboards on the barrier structure with additional repairs scheduled to begin June 2015 to further reduce injury to fish from contact with the barrier structure.  Repairs will be coordinated to minimize interference with adult fish returning to the White River, particularly the biannual pink salmon run, which normally occurs in late August through early October during odd numbered years.

The planning and design of the new facility has been a collaborative effort using a Regional Design Team with representatives from the Corps, the National Marine Fisheries Service, U.S. Fish and Wildlife Service, Muckleshoot Indian Tribe, Puyallup Tribe of Indians, Washington Department of Fish and Wildlife, and Cascade Water Alliance.

The EA and FONSI are available on the Seattle District website at: 

Mud Mountain Dam Fish Passage Environmental Assessment

Mud Mountain Dam Fish Passage Appendix A-C

Mud Mountain Dam Fish Passage Appendix D

Mud Mountain Dam Fish Passage Appendix E and F

Tanya King

Release no. 15-015