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Corps Dredging of Federal Navigation Channel
Completed for Snake, Clearwater Rivers, Two Ports

by Staff
Columbia Basin Bulletin, February 27, 2015

This dredge started work on Monday to remove a shoal near the lock entrance to Ice Harbor Dam on the lower Snake River. The U.S. Army Corps of Engineers announced Thursday that maintenance dredging of problem areas in the federal navigation channel, and at two port berthing areas, has been completed in the Snake and Clearwater rivers.

The dredging involved the removal of accumulated sediment that has been interfering with navigation. Dredging was performed to meet a current immediate need to re-establish the federal navigation channel to its congressionally authorized dimensions of 250 feet wide by 14 feet deep at Minimum Operating Pool elevation. Dredging began Jan. 12.

Maintenance dredging was completed this year in accordance with the Corps' comprehensive Programmatic Sediment Management Plan during the annual winter in-water work window, Dec. 15 through Feb. 28, when salmonid fish are less likely to be present in the river.

Maintenance dredging last occurred in the lower Snake River navigation channel in the winter of 2005-2006.

"Navigation on the lower Snake River is now safer," said Lt. Col. Timothy Vail, Walla Walla District commander. "We considered potential alternatives, determined dredging was the only effective short-term tool for addressing problem sediment that had accumulated to the point of interfering with navigation, and successfully completed maintenance dredging during the designated winter work window."

Dredging initially took place at the downstream lock approach of Ice Harbor Dam, then later on the Lower Granite Lock and Dam pool at the confluence of the Snake and Clearwater rivers in the Lewiston-Clarkston area, including Port of Lewiston and Port of Clarkston berthing areas.

The ports obtained their own dredging permits and paid for dredging of their berthing areas.

Dredged materials were used to construct additional shallow-water fish habitat near Knoxway Canyon (River Mile 116), about 23 miles downstream of Clarkston, Wash.

Corps' Northwestern Division Commander, Brig. Gen. John S. Kem, signed two Records of Decision on Nov. 14, 2014, for 1) the PSMP and 2) a current "immediate need" action (dredging. The RODs are based on consideration of reasonable alternatives and evaluation of potential environmental effects contained in the PSMP Final Environmental Impact Statement.

The PSMP describes a strategy for managing sediment accumulation that interferes with existing authorized purposes of the Corps' four lower Snake River dam and reservoir projects (Ice Harbor, Lower Monumental, Little Goose, and Lower Granite) in southeastern Washington and north central Idaho.

The Corps in mid-November awarded a $6,745,150 contract for its share of the immediate needs maintenance dredging that was just completed. The Corps estimated that that work would involve the removal of from 422,000 to 500,000 cubic yards of sediment.

The Corps decisions were contested in federal court. Judge James L. Robart of the U.S. District Court for the Western District of Washington, in early January declined to issue an injunction to stop the Corps immediate needs dredging project. The court is expected to consider the full merits of the case itself later this year. The lawsuit also challenges the legal validity of the PSMP.

Last November, non-profit environmental law firm Earthjustice, representing Idaho Rivers United, Pacific Coast Federation of Fishermen's Associations, Institute for Fisheries Resources, Washington Wildlife Federation, Sierra Club and Friends of the Clearwater, joined with the Nez Perce Tribe to file a complaint challenging the two Corps dredging RODs.

For more information about the PSMP, see the Walla Walla District website at

Related Sites:
Judge Rejects Preliminary Injunction To Halt 'Immediate Needs' Lower Snake Dredging Columbia Basin Bulletin, 1/9/15

Related Sites:
New Phase Begins in Legal Battle Over Future Dredging of Lower Snake Navigation Channel by Staff, Columbia Basin Bulletin, 2/20/14

Corps Dredging of Federal Navigation Channel Completed for Snake, Clearwater Rivers, Two Ports
Columbia Basin Bulletin, February 27, 2015

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