From this story in Time:
It's no floating garbage patch, but a 165-ton fishing dock is certainly a shocking thing to observe rolling in with the waves. The concrete and steel dock washed ashore Tuesday at Oregon's Agate Beach, a hulking monstrosity the size of a train car measuring 66 feet long. A small plaque on the dock gave the name of the manufacturer in Tokyo, who helped Oregon officials trace the docks to the fishing town of Misawa, in northern Japan. Four docks were ripped from the town's shoreline during the March 2011 tsunami, and before Tuesday, only one had resurfaced.