U.S. Army Corps of Engineers (Corps) officials met with fisheries experts May 8, to begin working on NOAA’s Biological Opinion (BiOp) recommendations to offset effects to Endangered Species Act (ESA) listed fish and Orcas from the operation and maintenance of Howard A. Hanson Dam (HAHD). Participants included the Muckleshoot Indian Tribe, NOAA Fisheries, Washington State’s Departments of Ecology and Fish and Wildlife, King County and Tacoma Water officials.
NOAA Fisheries officials issued a BiOp February 15, requiring the Corps to complete a downstream juvenile fish passage facility at the dam on the Green River, 21 miles east of Auburn, Washington. The BiOp included other recommendations including one to convene a meeting with agency officials “on or before February 2020” to discuss flow management to supplement instream flows. Additional meetings are also required to discuss fish passage design and monitoring, and establish protocols to reintroduce fish upstream of HAHD.
“We’re acting as quickly as we can on the BiOp because improving fish passage and protecting fish habitat on the Green River is a Corps priority,” said Corps fish biologist and ESA Coordinator Dr. Fred Goetz. “Each agency’s ultimate goal is improving fish passage and habitat on the Green River.”
Each agency’s role in that effort can be different, however, because each agency has different authorities and missions. For instance, HAHD missions include flood risk management, fish conservation, municipal and industrial water supply and ecosystem restoration. “Those are the dam’s congressionally authorized missions,” said Goetz. “Our authorities may limit what we can do. However, knowing what is important to our partners gives us a starting point to see what operational changes we may be able to make over time.”
In the end, completing a downstream fish passage facility at HAHD will provide access to critical habitat above HAHD for ESA-listed Puget Sound Chinook salmon and steelhead. The BiOp also addressed ESA-listed southern resident killer whales, the only endangered killer whale population in the United States. Chinook salmon are their primary food source, and reduced spawning and rearing habitat is a limiting factor for Puget Sound Chinook salmon.
Tacoma Water has managed an operating facility in the Green River watershed for more than 100 years. HAHD is three miles upstream of Tacoma Water’s Headworks diversion dam, where water from the Green River is diverted by Tacoma Water. The Headworks diversion dam was built prior to the Corps’ dam, and Tacoma Water has the requirement to transport adult fish upstream past both dams when downstream passage is completed.
Seattle District finished HAHD construction in 1961 and operates the earthen, rock-filled dam, controlling reservoir water levels and regulating Green River flow for flood risk reduction in the winter and flow-augmentation, releasing additional water for salmon habitat, during low-flow periods.
HAHD flood risk reduction operations have helped avoid an estimated $21 billion in flood damages in the heavily-populated Green River Valley. Augmentation, releasing water when the river historically ran dry, typically happens summer through fall and is primarily for fish conservation, ensuring enough water is flowing for aquatic resources, including spawning and rearing salmon.