KNIGHT ISLAND - Mike Angaiak crouches on his knees on the rocky beach at Snug Harbor, scraping the bottom of a sandy pit with a trowel.
Finding nothing, he fills the pit with sand and rocks and moves on to a spot about six feet away. Angaiak tosses aside rocks and boulders and starts to dig another hole. But this time, the sand beneath the rocks is brown and oily.
"Ugh," he says as he lifts an oiled rock from the freshly dug hole and sniffs it. "You can smell it."
Angaiak, from the Prince William Sound village of Chenega Bay, is part of a crew of eight working on this stretch of shoreline at Snug Harbor. Crews are spending the summer searching for oil that remains from the Exxon Valdez spill more than a dozen years ago.
"There's no rocket science to finding it," said Jeff Short, a research chemist with the National Marine Fisheries Service, the agency conducting the shoreline survey.
Human efforts in the years immediately following the spill, as well as tidal action and storms, have washed away much of the oil, and the sound has largely recovered. But pockets of pollution remain.
"It's been a big surprise," Short said. "Most people, including us, would have thought it would be gone by now."
The last time Prince William Sound beaches were surveyed for surface oil was in 1993. While that type of on-the-ground survey was helpful in assessing the need for cleanup, it was not useful in producing an estimate of the oil remaining in the sound, Short said.
Snug Harbor is 55 miles southwest of Bligh Reef, where the Exxon Valdez ran aground, gushing 11 million gallons of crude oil into the waters of Prince William Sound on March 24, 1989.
A 1994 study by the fisheries service estimated that about 70 percent of the spilled oil had evaporated into the air or biodegraded in the ocean or on shore, and 14 percent had been recovered through cleanup efforts.
About 13 percent - 1.4 million gallons - was estimated to remain in the mud, sand and sediments in the Gulf of Alaska and Prince William Sound. About 2 percent, or 217,000 gallons, was thought to remain on beaches. Short describes that study as an educated guess, based upon the behavior of oil.
Back at Snug Harbor, as the water laps the shore in this quiet cove, the environmental disaster that blanketed beaches with oil and killed thousands of birds and marine mammals seems a world away.
But as the workers move across the beach with shovels and picks they find spots where oil has soaked into the sand. The work is backbreaking, time-consuming and tedious, and the crew puts in long days, the hours dictated by the tides.
"Some beaches are easier than others," said Mandy Lindeberg, the field chief supervising the project.
Just a few days earlier and about 18 miles north of here, the crew scrambled over wet, mossy boulders in the shadow of a dense spruce forest at Northwest Bay on Eleanor Island. The beach looks idyllic, but tiny black globules of oil can be found under rocks and floating in the tidal pools.
"It's really the topography that dictates how long the oil is going to stay," said Lindeberg.
As of mid-June, the crew had dug about 2,500 pits on randomly selected beaches oiled by the spill. By the end of summer about 8,000 pits will have been dug and examined for oil.
The workers have encountered oil about 8 percent of the time on beaches that had been heavily oiled, Short said. Whenever the workers find oil, they map the size and location of the oil patch. The amount of oil will be estimated by sampling.
From that information, Short will estimate the oil remaining in Prince William Sound, without having to examine all of the beaches. He expects his study to be completed in about a year.
Any oil found would have a 90 percent chance of having come from the Exxon Valdez, Short said.
Exxon Mobil Corp. spokesman Tom Cirigliano would not comment on the study, but he said Exxon worked on cleaning up the oil until state and federal officials called a halt.
"There were certain areas of Prince William Sound that the state and the federal governments determined that no further cleaning should take place because the cleaning would cause more harm to the environment than the natural cleaning of oil," Cirigliano said.
"Of course there are places in Prince William Sound where, if you look hard enough, you can find Valdez oil," he said.
Fisheries service officials say the amount of oil found so far is not likely to have detectable effects on fish or wildlife. But an estimate of the amount of pollution that remains will help resource managers and scientists decide if further study or monitoring is needed.