Workers start cutting up tsunami dock that washed ashore in Ore.

With a crowd of spectators lounging in lawn chairs and snapping photos, workers Wednesday started cutting up the boxcar-sized Japanese dock that was torn away from a fishing port by last year's tsunami and washed up on an Oregon beach.

The plan is to cut the 165-ton concrete dock into five slices, like a loaf of bread, using a piece of equipment called a wire saw. If all goes well, the work should be finished by today, leaving nothing but a depression in the sand until the ocean waves fill the beach back in again.

"We really are trying to keep in mind that this came from a massive disaster in Japan and try to treat it with the respect it deserves," Scott Korab, director of business development for Ballard Diving and Salvage of Vancouver, Wash., said over the low rumble of the wire saw and the roar of the wind.

"We are trying to complete the job in a safe and timely manner, and make sure we are giving the public all the time they need to get some last photos of everything as well," he said.

The pieces will be lifted by a crane onto flatbed trucks. The trucks drive over the soft sand on a temporary roadway of planks and steel plates. Biologists will check the bottom of each slice for invasive species. The pieces, one to a truck, will be driven to the Portland suburb of Sherwood for dismantling.

The dock washed ashore on Agate Beach north of Newport, Ore., on June 5.

An 11-foot piece bearing a mural of blue waves that mysteriously appeared on the dock in the past week will be cut off and returned to Newport for use in a memorial to be erected somewhere yet to be determined, Korab said.

The Oregon Historical Society has asked for a piece, as has a museum at the University of Oregon, said Parks Department spokesman Chris Havel.

Korab's company won the contract from the department with a bid of $84,155.

Workers dug around the dock to the bottom, then snaked a PVC pipe through the wet sand underneath and threaded the cutting wire through. Then they hooked it up to a motor and pulleys on top of the dock that keep the wire running continuously in a loop, cutting through the mass of concrete and rebar. Workers have a diagram of the dock to plot the best path for cutting.

The 60-some spectators, kept about 150 feet away by a fence of safety tape, were a new element for the workers, Korab said.

"We have people kind of camping out as if this was a parade. People brought their lawn chairs and are finding logs to sit on, watching it all unfold," he said. "We usually are doing things under the radar."

The dock became an international sensation after coming to rest in Oregon. A commemorative plaque showed it was one of four owned by Aomori Prefecture that broke loose from the port of Misawa on the northern tip of the main island during the 2011 tsunami.

Joe Kruger, a retired construction superintendent from Albany, Ore., drove over with his wife to watch the spectacle. He was looking forward to seeing the crane lift one of the pieces onto a truck.

"Until that happens, there isn't going to be much," he said. "That concrete sawing is pretty dull."

His wife, Suzette Hughes, said they were at the beach just a few miles away the day the dock washed up, but didn't learn about it until they got home. She collected pieces of pumice from the beach after the 1980 Mount St. Helens eruption, missed the 1970 attempt to dispose of a dead whale by blowing it up with dynamite, and remembers her grandmother having to go to higher ground when the 1964 Alaska earthquake generated a tsunami that hit the Oregon Coast.

"We love the beach," she said.

There will be no souvenirs for onlookers this time, Korab said. The wire saw makes a very clean cut, and everything will be hauled away.

Scientists have warned that the 1.5 tons of seaweed, mussels, barnacles and starfish attached to the dock represented a significant threat from invasive species. Volunteers scraped it all off, buried it above the high water line, and sterilized the dock with torches.

The dock is the biggest single piece of tsunami debris so far to float some 5,000 miles across the Pacific and wash up on North America's shores. An abandoned fishing boat that appeared off Alaska was sunk. A motorcycle in a shipping crate appeared on a remote island off British Columbia and went to a museum. A soccer ball reached Alaska. And officials are keeping an eye on what appears to be a barge floating off the coast of Washington.

The Japanese government estimated 1.5 million tons of debris was washed into the ocean, but it remains uncertain how much remains afloat. The National Oceanic and Atmospheric Administration says the debris covers an area of the North Pacific roughly three times the size of the contiguous U.S. More is expected to wash ashore over the next several years.

The dock's commemorative plaque is being kept in a safe by the Parks Department until authorities decide whether to return it to Japan or give it to a museum in Oregon, Havel said.

Many in the crowd Wednesday wanted to know why the dock wasn't just left on the beach, said Oregon Department of Fish and Wildlife spokesman Brandon Ford.

"It seems like the consensus is, `Gee, we ought to just leave it,"' he said. "Then we say, `No, this is a natural area. We don't want to leave a big piece of trash in something like Yellowstone Park.' Then they say, `Oh, we understand that."'