OLYMPIA - Washington state has renewed its approval that allows the U.S. Army Corps of Engineers to proceed with annual maintenance dredging of the navigation channel at the mouth of the Columbia River.

The "401 certification" is issued under the federal Clean Water Act and certifies that the state's water quality standards will be met during dredging and disposal.

Annual maintenance dredging allows the river navigation channel to be kept at federally authorized depths of up to 55 feet by removing restrictive shoals made up of naturally occurring sedimentary material. The project will remove four to five million cubic yards of material from approximately six miles of the navigational channel in the river mouth. The material will be placed in a variety of in-water "disposal" sites.

Routine maintenance dredging in the river mouth differs from the proposal to deepen the river channel, which has yet to receive environmental approvals from Washington.

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