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The Columbia River navigation channel begins at the Columbia River bar and continues five miles upriver at a depth of 55 feet and a width of 2,640 feet. After which, it maintains a depth of 40 feet and a width of 600 feet for 100 miles to the Portland Harbor. The channel passes under the Astoria Bridge, with a vertical clearance of 208 feet and a horizontal clearance of 1070 feet, and the Longview Bridge, with vertical and horizontal clearances of 198 feet and 1085 feet, respectively.
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