More than a year after a tsunami devastated Japan, killing thousands of people and washing millions of tons of debris into the Pacific Ocean, the U.S. government and West Coast states don't have a cohesive plan for cleaning up the rubble that floats to American shores.

There is also no firm handle yet on just what to expect.

The Japanese government estimates that 1.5 million tons of debris is floating in the ocean from the catastrophe. Some experts in the United States think the bulk of that trash will never reach shore, while others fear a massive, slowly-unfolding environmental disaster.

"I think this is far worse than any oil spill that we've ever faced on the West Coast or any other environmental disaster we've faced on the West Coast" in terms of the debris' weight, type and geographic scope, said Chris Pallister, president of a group dedicated to cleaning marine debris from the Alaska coastline.

David Kennedy, assistant administrator for the National Oceanic and Atmospheric Administration's National Ocean Service, told a U.S. Senate panel last month that in most cases debris removal decisions will fall to individual states. Funding hasn't been determined.

U.S. Sen. Mark Begich, D-Alaska, and other West Coast political leaders, have called that scenario unacceptable, saying tsunami debris poses a pending national emergency. "If this was a one-time event all at once, we'd declare it an emergency and we'd be on the ground like that," he said, during the hearing he led.

One astonishing example of how the unexpected can suddenly appear occurred Wednesday in Oregon when a concrete and metal dock that measured 66 feet long, seven feet tall and 19 feet wide, washed ashore a mile north of Newport. A Japanese consulate official in Portland confirmed that the dock came from the northern Japanese city of Misawa, cut loose in the tsunami of March 11, 2011.

"I think that the dock is a forerunner of all the heavier stuff that's coming later, and amongst that heavier stuff are going to be a lot of drums full of chemicals that we won't be able to identify," Pallister said.

His group, Gulf of Alaska Keeper, works in the same region devastated by the Exxon Valdez oil spill, which dumped 11 million gallons of oil into Prince William Sound in 1989.

Tsunami debris is tough to monitor. Winds and ocean currents regularly change, while rubbish can break up. Some trash, like fishing gear, kerosene and gas containers and building supplies, can be tied to the tsunami only anecdotally. But in other cases - a soccer ball and a derelict fishing boat in Alaska and a motorcycle in British Columbia, for example - items have been traced back to the disaster through their owners.

NOAA projects the debris having spread over an area roughly three times the size of the contiguous United States, but can't pinpoint when or how much might eventually reach the coasts of Alaska, Washington, Oregon, California and Hawaii.

An independent group of scientists and environmental activists are scheduled to sail aboard the "Sea Dragon" from Japan Saturday to an area north of the Hawaiian islands, with plans to zigzag through the debris, document what's floating and try to determine what might reach the West Coast.

"You have a unique experiment," said Marcus Eriksen, a researcher at the Algalita Marine Research Institute in Long Beach, who is leading the expedition. "You have entire homes and all their contents ... anything you may find in a Japanese home could be floating in the ocean still intact."

Seattle-based oceanographer Curtis Ebbesmeyer, who has been tracking ocean trash for 20 years, predicts the main mass of tsunami debris will reach the U.S. coast from Northern California to southeast Alaska as early as October, with the beginning of fall storms.

Cleanup plans should be finalized no later than September, Ebbesmeyer cautioned. There may also be sensitive issues to be decided, he said, including how to deal with any human remains or personal mementos.