U.S. Coast Guard A dock is seen washed up on a beach at Washington's Olympic National Park on Tuesday.

Officials on Wednesday were figuring out how to reach and then examine a massive dock that made landfall on a remote, rugged beach in Washington state. First sighted six days ago, the dock wasn't spotted again until Tuesday afternoon when a Coast Guard helicopter crew located it.

"They were out in challenging conditions looking for a needle in a haystack, and they found it," Gov. Chris Gregoire said in a statement.

The next step is to reach the site "to evaluate the massive dock for any potential invasive aquatic species that may have 'hitchhiked' while it was drifting in the ocean, to evaluate the dock’s origins, and to develop a response," Washington's Marine Debris Task Force stated.

The dock is sitting on a rocky beach inside Olympic National Park, between La Push and the mouth of the Hoh River. Officials will determine the size of the dock once they reach it.

Crew aboard the "Lady Nancy" fishing boat first sent the Coast Guard a photograph of the dock on Friday, saying it was taken about 16 nautical miles northwest of Grays Harbor, Wash.

It is not known yet whether the dock is from Japan's 2011 tsunami, but one similar to it washed ashore in Oregon last June. That 66-foot-long dock is the largest tsunami item to have made it to the West Coast so far.

Another dock was seen off Oahu, Hawaii, in September but it is also not known if that is the same one that washed ashore Tuesday.

Japan estimates the tsunami swept about 5 million tons of debris into the Pacific, and that two-thirds of that sank quickly. Some of the remaining 1.5 million tons are heading for West Coast shores.

Through Last Thursday, the National Oceanic and Atmospheric Administration said it had received 1,432 debris reports, of which 17 were confirmed as definite tsunami debris.

NOAA asked that anyone sighting any large marine debris report it to DisasterDebris@noaa.gov.

The trash accumulating in the Pacific Ocean – scientists estimate there are 1.5 million tons of tsunami debris alone -- is arriving on the West Coast. NBC's Miguel Almaguer reports.

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