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Corps Set to Launch McNary, Lower Snake Dredging

by Staff
Columbia Basin Bulletin - October 7, 2002

The U. S. Army Corps of Engineers' Walla Walla District plans to perform routine maintenance dredging this year on the lower Snake River and McNary Reservoir on the Columbia River following final approval its long-term Dredged Material Management Plan and Environmental Impact Statement.

The Corps, in cooperation with the U.S. Environmental Protection Agency, developed the plan for the navigation channel maintenance over the past four years at a cost of $3.5 million. The recommended alternative combines maintenance dredging, beneficial use of dredged materials, and raising levees.

Brig. Gen. David A. Fastabend, the Corps' Northwestern Division commander signed the Record of Decision for the plan on Sept. 27. The plan focuses on managing dredged material removed from the four reservoirs on the lower Snake River and McNary reservoir on the Columbia River.

The Corps' first dredging activity under the plan is proposed for this winter. The Corps will dredge the navigation channel at the confluence of the Snake and Clearwater rivers, several port facilities in the Lewiston-Clarkston area, several recreation facilities in Lower Granite and Little Goose reservoirs, navigation lock approaches to Lower Granite and Lower Monumental Dams, and other areas.

Adaptive management is incorporated as part of the plan.

"Opportunities to use dredged material cannot always be anticipated, so a process to continue the environmental coordination will go on through the next 20 years," said Jack Sands, project manager.

"One of the beneficial uses of dredged material includes in-water disposal to create shallow water sand bars along shorelines of the Lower Granite reservoir," Sands said. "The creation of this habitat has the potential to restore some of the conditions of the lower Snake River prior to dam construction, and is expected to provide benefits to some of the salmon species listed for protection under the Endangered Species Act by providing resting and rearing habitat for juvenile salmon prior to their downstream migration to the ocean."

As part of the plan, the Corps is proposing raising some levees to maintain recommended flow capacity.

"Extensive coordination would be completed before this work could begin," said Sands.

The 14-foot deep and 250-foot wide navigation channel through these reservoirs has historically been dredged in some locations. These reservoirs are part of an inland navigation system that provides slackwater navigation from the mouth of the Columbia River near Astoria, Ore., to port facilities on the Snake and Clearwater rivers in Clarkston, Wash., and Lewiston, Idaho. Ports and marinas reimburse the Corps for the costs incurred for dredging their facilities.

For more information on the Corps' Dredged Material Management Plan/Environmental Impact Statement, visit .

Corps Set to Launch McNary, Lower Snake Dredging
Columbia Basin Bulletin, October 7, 2002

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