Corps to dredge river

Following intensive U.S. Army Corps of Engineers review, the corps’ Northwestern Division Commander, Brig. Gen. John S. Kern, signed two Records of Decision Nov. 14 for the Lower Snake River Final Programmatic Sediment Management Plan and a current “immediate need” action (dredging) to reestablish the authorized dimensions of the Lower Snake River federal navigation channel.

The first signed decision was for the long-term, comprehensive plan for managing sediment accumulation that interferes with existing authorized purposes of the corps’ lower Snake River dam and reservoir projects. The affected authorized project purposes are navigation, recreation, fish and wildlife conservation and flow conveyance. The corps evaluated potential environmental effects of a range of sediment management alternatives and developed measures for addressing future problem sediment.

The second signed decision was for a current “immediate need” action to re-establish two areas of the federal navigation channel: the navigation lock approach at Ice Harbor Dam and at the confluence of the Snake and Clearwater rivers to authorized dimensions of 14 feet deep by 250 feet wide at minimum operating pool. Maintenance dredging last occurred in the lower Snake River navigation channel in the winter of 2005-2006.

The corps plans to dredge during the first available winter “in-water work window,” Dec. 15 to Feb. 28, when salmonid fish are less likely to be present in the river. The corps plans to use the dredged material to create shallow-water habitat for juvenile salmon at Snake River mile 116, just upstream of Knoxway Canyon and 23 miles downstream of Clarkston, or about eight and a half miles upstream from Lower Granite Dam.

The dredging will have no impact on Port of Wilma because that side of the river is scoured out naturally by the flow of the river.

In addition, the corps issued Clean Water Act Section 404 and Rivers and Harbors Act Section 10 permits to the Port of Lewiston and Port of Clarkston for berthing area maintenance dredging.