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Removable Spillway Weirs:
Which Dams Should Get Them First?

by Barry Espenson
Columbia Basin Bulletin - October 29, 2004

The group charged with setting spending priorities for fish passage improvements at federal mainstem hydro projects was asked last week whether they might want to put the Columbia River's McNary Dam ahead of the Snake's Little Goose facility for installation of so-called "removable spillway weirs" -- a new surface bypass technology.

The question came up as state, federal and tribal fish managers and federal action agencies representatives mulled the project proposal list for an as-yet undetermined Columbia River Fish Mitigation Program budget. The multi-agency group convenes as the System Configuration Team to help guide implementation of mainstem hydrosystem actions deemed necessary to improve fish survivals.

The Corps of Engineers' John Kranda on Oct. 21 noted that the "action agencies' " Updated Proposed Action suggests that lower Columbia River passage improvements should in most cases have priority.

That document advises that the hydro projects with the lowest juvenile passage survival should receive attention first, but said that improvements at the Columbia's Bonneville, The Dalles, John Day and McNary dams would benefit all species originating above Bonneville. Lower Snake improvement would benefit only Snake River fall and spring/summer chinook (, sockeye) and steelhead.

According to the UPA, lower Columbia improvements could benefit up to 11 stocks out of the 13 that are either listed or proposed for listing under the Endangered Species Act, including the three (four) wild Snake River stocks.

The draft UPA was released by the Bonneville Power Administration, Corps of Engineers and Bureau of Reclamation at the end of August. It includes a long list of hydrosystem improvements as well habitat and hatchery work that is all intended to mitigate for impacts of hydro operations on listed salmon and steelhead.

A draft biological opinion was released by NOAA Fisheries at the same time with the conclusion that the proposed operations do not jeopardize the survival of any of the listed species. A final BiOp is due by Nov. 30 to replace the 2000 document. That BiOp's no-jeopardy conclusion was declared invalid by U.S. District Court Judge James A. Redden in May 2003.

Fish and wildlife managers had early this summer indicated that they would like to see the RSWs installed first at Lower Monumental and Little Goose to allow an evaluation of survival through the four lower Snake River dams for fish that migrate in-river vs. those that are collected and transported to the Columbia estuary aboard barges.

An RSW has been in place at Lower Granite Dam for three years and one will be installed at Ice Harbor in time for next spring's juvenile salmon outmigration.

Biological testing at Lower Granite has shown that the RSW is five times more efficient at attracting juvenile salmon and steelhead than traditional spill, effectively passing more fish with less water. The studies have also shown that the fish don't hesitate or delay as long before passing the structure, making them less vulnerable to predators and allowing to them stay closer to their natural migration timeline.

The test also show that survival through the RSW is as good or better than traditional spill -- the passage route managers say results in better smolt-to-adult returns than transportation or in-river migration with passage through turbines or mechanical bypass.

The RSWs are also attractive from a financial standpoint because they require a lesser amount of spill. Spilled water is considered foregone power, and revenue, generation.

The SCT had earlier planned tentatively to schedule installation of an RSW at Lower Monumental in time for the 2007 outmigration and at Little Goose before the spring of 2008. The SCT project prioritization now earmarks $2.8 million to do the necessary modeling planning for the Lower Monumental RSW.

A priority ranking -- based on preferences of Idaho, Oregon and Washington, tribal, NOAA Fisheries and U.S. Fish and Wildlife Service preferences -- placed the Little Goose and McNary RSW projects third and fourth out of more than 50 projects vying for funding in fiscal year 2005. An earlier list penciled in $50,000 to launch scoping of the McNary project and $1.7 million to begin Little Goose plans and specs.

Kranda suggested that perhaps the Little Goose and McNary projects, and their 2005 budgets, be flip-flopped with the goal of installing a first RSW at McNary in 2008, a second in 2009 and that the Little Goose project be pushed back until perhaps 2010. The draft UPA and BiOp have set as a goal to have surface bypass technology installed where feasible at all Columbia/Snake hydro projects by 2014.

The Ice Harbor RSW construction and spring/summer biological evaluation is the biggest planned expenditure within the 2005 Columbia River Fish Mitigation Program budget this year at $14.1 million. Congress has not yet approved a CRFMP budget but the Corps, which implements the program, has had available about $70 million in recent years.

Russ Kiefer argued against a shift in the RSW construction schedule, noting that lower river salmon populations generally fare better than the Snake River stocks. He predicted that increasing the number of fish migrating in-river would bring the greatest gains for Snake River fish.

"There may be problems at McNary but it seems to us that the Snake River projects have greater problems," he said.

Kranda suggested that perhaps an alternate spill scheme could be devised for Little Goose that would allow more in-river passage until the time comes for RSW installation. Meanwhile, he asked the SCT to consider McNary, "where it (RSW technology) benefits the most species."

Tom Lorz of the Columbia River Inter-Tribal Fish Commission said that the tribes had been told that a full-scale evaluation of in-river vs. transportation survival -- something long-sought -- would not take place until RSWs were installed throughout the lower Snake system. The draft BiOp suggests that test would begin in 2007 or 2008. (bluefish asks: What is the justification for this delay?)

The test "is important to everybody," Kranda said, and "ideally we'd want the whole system in place." But planning requirements and finances most likely wouldn't allow the Corps to complete more than one project per year.

The Bonneville Power Administration's Kim Fodrea said the action agency's hydro team needed to study the proposed shift in schedule more closely before offering an opinion. notes that juvenile survival through spillway passage at Little Goose is estimated to be 100%. Very little further spillway survival benefit is possible at Little Goose. Ice Harbor, however, has substantial spillway mortality.

Related Pages:
Install Removable Spillway Weirs at All Corps Dams by John McKern, Columbia Basin Bulletin,10/29/4

Barry Espenson
Removable Spillway Weirs: Which Dams Should Get Them First?
Columbia Basin Bulletin, October 29, 2004

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