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Biop Says Corps Must Provide Downstream Salmon Passage At Upper Green River Dam

What goes up must come down, and in the case of King County’s Green River, that requires building downstream fish passage infrastructure at Howard Hanson Dam.

AN ARMY CORPS OF ENGINEERS AERIAL IMAGE SHOWS HOWARD HANSON DAM ON THE UPPER GREEN RIVER. A BIOP REQUIRES THAT DOWNSTREAM FISH PASSAGE BE BUILT AT THE FACILITY TO AID ESA-LISTED CHINOOK, STEELHEAD AND ORCAS. (COE)

Earlier this month, federal fishery overseers issued a new biological opinion that found the Corps of Engineers had to help ESA-listed juvenile Chinook and steelhead get from the 100 miles of spawning and rearing habitat above the project to the waters below there.

That “Reasonable and Prudent Alternative” to collect the young fish would not only improve the viability of both populations but also help out the region’s starving orcas.


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“Because (Puget Sound) Chinook salmon are an essential prey base for Southern Residents … the higher (Puget Sound) Chinook salmon abundance provided by access to the upper watershed would also contribute to the survival and recovery of killer whales,” NOAA’s biop states.

Downstream passage would also build upon Tacoma Water’s existing facilities that can provide a lift for returning adult salmon and steelhead arriving at the utility’s diversion dam 3 miles below the reservoir, as well as link in with fish habitat work being done in the lower, middle and upper reaches of the Central Cascades river that drains into Seattle’s Elliott Bay as the Duwamish.

“Assuming 75% of the annual production upstream from (Howard A. Hanson Dam) would survive passage and be recruited into the adult population were safe and effective downstream passage provided, we estimate that an additional 644 natural origin spawners would return to the Green River from production areas upstream of HAHD. Adding the potential production from the upper Green River to the 1,288 spawners returning from production downstream from HAHD gives a total Green River escapement of 1,932 natural origin spawners returning to the Green River. About 36% of the Chinook salmon returning to the Green River are harvested,” the biop states.

In a press release, the Engineers’ Seattle District Commander Col. Mark Geraldi said that improving fish passage at its project is “a priority” for the federal agency.

“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,” Geraldi said.

WITH THE GREEN-DUWAMISH IDENTIFIED AS A KEY SOURCE OF CHINOOK FOR PUGET SOUND ORCAS, PLANS ARE IN THE WORKS TO NOT ONLY INCREASE HATCHERY PRODUCTION BUT PROVIDE ACCESS AROUND A PAIR OF DAMS FOR RETURNING ADULTS TO GET TO THE UPPER WATERSHED AND SPAWN. (ANDY WALGAMOTT)

Essentially, the biop tells the Corps to get back to work on a project they began in the early 2000s after consulting with NOAA, spent tens of millions of dollars drawing up, but then “abandoned its commitment to construct them” as Congressional funding ran out in 2011 and wasn’t reauthorized.

That led to a reopening of consultations and downstream fish passage being left out of the Corps’ 2014 biological assessment for operating the project.

NOAA found that that was likely to harm kings, steelhead and orcas and instead came up with the biop’s RPA and a target of February 2031 for the Corps to have the new facility’s bugs worked out and be operating for that spring’s smolt outmigration.

“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,” said Kim Kratz, a NOAA Assistant Regional Administrator, in a press release.

Congress will need to provide the funds for the Corps, which is also spending $112 million trap-and-haul facility at Mud Mountain Dam, in the next major watershed to the south of the upper Green.