Mud Mountain Dam, WA (Fish Passage Facility)


The existing fish passage facility is six miles downstream of Mud Mountain Dam (MMD). The system is comprised of a barrier structure (owned by Cascade Water Alliance (CWA)) which prevents upstream fish passage, a fish trap (owned by the Corps), and the fish release site (owned by the Corps) above the dam.  An upstream trap and haul system around MMD was agreed upon in 1948 by the U.S. Army Corps of Engineers (Corps) and the Washington State Department of Fisheries as means to satisfy a mitigation requirement for the construction of the dam. The system maintains fish runs past MMD, which include Endangered Species Act (ESA) listed species since their listing, and allows the Muckleshoot Indian Tribe to gather brood stock for its adjacent hatchery. The current fish trap is 62 years old and the barrier structure was built in the early 1900s. The barrier structure requires frequent maintenance and repair via a cooperative agreement with CWA compromising an ever increasing proportion of MMD's Operations and Maintenance Funding (~20%). The fish trap and haul facility is aged but currently performs to its original design standards, though it does not meet modern fish trap criteria. In 2013 four trucks conducted a 24/7 operation from mid-August to mid-October to ensure passage of all fish that entered the trap facility.


The components of the current facility each have risks associated with their age and condition, to include personnel safety. The Seattle District completed a Letter Report in Fiscal Year 2013 using current Construction General funding to address replacement of the barrier structure as the highest priority risk. Though all system components, including the fish trap, are in need of maintenance, the barrier structure is prioritized for replacement because its current condition is a known threat to the reliability of fish passage and represents a critical environmental, economic, and safety liability. In Fiscal Year 2013 the Corps re-initiated ESA consultation with the National Marine Fisheries Service because continued maintenance of the existing barrier structure constitutes an impact on listed species that was not considered in the 2007 Biological Opinion (BiOp). NOAA Fisheries released a BiOp in October 2014 with proposed Reasonable and Prudent Alternatives (RPAs) to avoid jeopardy to Chinook, steelhead and killer whales. The RPAs include:
 - Operational changes for downstream fish passage through the outlet tunnels to achieve 95 percent smolt survival (ongoing)
 - Interim repairs to the existing fish barrier (completed in 2015)
 - Design, construct and operate a new fish barrier and collection facility to provide safe, timely and effective upstream passage for ESA listed species

Issues and Other Information

The Corps of Engineers and NOAA Fisheries are working together to carry out measures to safely pass ESA listed fish upstream and downstream of Mud Mountain Dam.  The Seattle District will continue to engage with resource co-managers (Muckleshoot Indian Tribe, Puyallup Tribe of Indians, and Washington Department of Fish and Wildlife and other stakeholders) as we move forward on design and into construction.

Mud Mountain Dam Fish Passage Facility Video