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KITTERY, ME (April 11, 2022) The Los Angeles-class submarine USS Cheyenne (SSN 773) passes through the newly procured entrance structure that closes in the Superflood Basin. The Basin allows, for the first time, Los Angeles-class submarines to be docked in Portsmouth Naval Shipyard's Dry Dock #1 without the use of buoyancy assist cans by flooding to a higher water surface elevation than the adjacent river to provide adequate clearance between the bottom of the dry dock and the submarine's keel. (U.S. Navy photo by Jim Cleveland)
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