NOAA Fisheries officials issued a Biological Opinion (BiOp) February 15, requiring the U.S. Army Corps of Engineers complete a downstream fish passage facility at Howard A. Hanson Dam (HAHD) on the Green River, 21 miles east of Auburn, Washington.
Completing the project will provide critical habitat for Endangered Species Act (ESA)-listed Puget Sound Chinook salmon and steelhead. The BiOp also addresses 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.
Almost half of the Green River’s suitable and historical Chinook salmon spawning and rearing habitat, about 100 river and stream miles, is above Tacoma Water’s Headworks diversion dam and HAHD in the Upper Green River basin. Tacoma’s diversion dam was built 50 years before HAHD.
A downstream fish passage and additional water storage project for Tacoma Water were congressionally authorized in 1999. The Green River serves as Tacoma Water’s primary water supply. Construction began in 2003 on the fish passage which is authorized as an ecosystem restoration feature. Work stopped on the passage project in 2011 because costs were projected to exceed congressionally authorized funding limits and require reauthorization to attain more funding.
“Improving fish passage at Howard Hanson Dam is a priority for the Corps,” said Seattle District Commander Col. Mark Geraldi. “This is a project we’ve been working on. NOAA Fisheries’ BiOp provides us crucial guidance and design criteria to follow as we forge ahead.”
Under Section 7 of the ESA, federal agencies must consult with NOAA Fisheries on activities that may affect ESA-listed species. These inter-agency consultations are designed to help federal agencies in fulfilling their duty and ensure their actions do not jeopardize the continued existence of a species, or destroy or adversely modify designated critical habitat. NOAA Fisheries’ Office of Protected Resources issues Biological Opinions.
HAHD missions include flood risk management, fish conservation, water supply and ecosystem restoration. The last three missions are balanced while its pool elevation fluctuates about 100 feet spring through fall. Juvenile Chinook salmon tend to stay in the surface water during outmigration, so a downstream fish passage facility will have to collect fish at a variety of elevations as the reservoir changes.
“This creates a number of challenges when designing and constructing a fish passage project,” said Geraldi. “Science has progressed and there are now projects with similar, though not exact, conditions we can study. We’ll take full advantage of the latest science as we reevaluate the previous design and move forward.”
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, 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.
For more than 90 years, Tacoma Water has managed the Green River watershed. HAHD is three miles upstream from Tacoma Water’s Headworks diversion dam, where water from the Green River is diverted by Tacoma Water. The diversion dam was built prior to the Corps dam and Tacoma Water has the requirement to transport fish upstream past both dams.
For its part on the Green River, Tacoma Water has already completed an upstream fish passage facility and are poised for the Corps to complete the downstream passage facility. Both organizations have also been working together, completing fish habitat projects upstream in anticipation of salmon being returned to the watershed Tacoma Water oversees above HAHD.
"We know from experience that reopening upstream access to important spawning and rearing habitat makes a world of difference for fish," said Kim Kratz, Assistant Regional Administrator of the Oregon/Washington Coastal Office in NOAA Fisheries’ West Coast Region. “We’re optimistic that new fish passage at Howard Hanson Dam, with continued habitat restoration in the more developed lower and middle Green River, will boost fish populations toward recovery. That will in turn support tribal treaty fishing rights, and benefit critically endangered southern resident killer whales.”
NOAA Fisheries also issued a BiOp in October 2014 for the Seattle District’s Mud Mountain Dam (MMD) on the White River near Enumclaw, Washington. Among NOAA Fisheries’ recommended improvements for MMD was installing an effective upstream fish passage to replace one built in the 1940s that was outdated and undersized for current fish runs.
“We received funding for the Mud Mountain Dam Fish Passage Facility and then began construction in 2018 on a new $112 million trap and haul facility,” said Geraldi. “The Corps’ regional design team for this massive project included more than 150 employees from three Corps districts and two architecture and engineering firms. We will use that knowledge to address passage at Howard. However, completing a Howard Hanson facility will also require funding to start again and additional congressional authorization to begin construction.”
For more than 15 years, the Corps has also been supporting fish habitat by placing woody debris and gravel into the Green River downstream of Tacoma Water’s facility. Corps employees collect large logs and other woody debris as it floats downstream before it can enter and possibly damage the dam’s intake or tunnels. This debris is transported downstream and reintroduced into the river for salmon habitat. The wood is carried by the river and has improved river habitat as far downstream as Auburn. Adding the gravel has increased suitable spawning habitat from the Tacoma diversion dam to the Green River Gorge, an area heavily used by spawning Chinook salmon.