The 165-tonne structure made of concrete, metal and tyres, and
studded with starfish and barnacles, arrived on a beach south-west of
Portland, Oregon.
It has tested negative for radiation, but scientists say a host of invasive marine species may have hitched a ride.


Police are guarding the dock while officials decide what to do with it.



“Start Quote
If this crossed the Pacific Ocean and
it's this big, that means that just about anything of our worst
nightmares could cross the Pacific Ocean”

Kirk Tite
Local resident

A plaque on the 20m-long (66ft)
structure, which was first mistaken for a barge, shows it came from the
port of Misawa in northern Japan.
It has taken 15 months to drift across the Pacific to Agate
beach since the earthquake and resulting tsunami shook it loose. Two
other docks from the same port are still missing.