A 165 ton dock constructed of concrete, metal and tires ripped away during the 2011 Japan tsunami was washed up over 8,000 miles away on the Oregon coast.

The dock, so large it was initially mistaken for a barge, carries a plaque stating it was part of the port of Misawa. Waves from the tsunami reached at least nine feet in Misawa.

Two other docks from the same port are missing at sea.

Oregon Senator Ron Wyden is asking those tracking the debris to focus their efforts as something as big as a dock could damage or sink ships. Other large pieces of debris have caused risk to American vessels like an unmanned Japanese ship that had to be sunk by the Coast Guard in April as it drifted toward Alaska.

The dock has tested negative for radiation but scientists fear that invasive marine creatures could have attached themselves to the dock and could infest the ocean floor. Oregon State University researchers have found at least one starfish native only to Japan clinging to the structure. They are unable to determine if other non-native animals reached American shores or the impact on the native wildlife.