From a helicopter, the wave-washed beach looks as if the worst oil spill in U.S. history had never touched it.

Silvery sticks of driftwood poke through a deep blanket of snow, and smooth gray pebbles roll in the surf under the gaze of a bald eagle perched in a shoreside spruce.But the view doesn't impress Joe Bridgman of the Alaska Department of Environmental Conservation. Dashing out as the chopper lands, he digs into the cobble beach and quickly finds what he knew he would.

"Oil," he says. "Smell it?"

The pungent odor of petroleum wafts through the air as the hole turns black with crude oil, an oozing remnant of the 10.8 million gallons spilled into Prince William Sound last March 24 by the tanker Exxon Valdez.

Bridgman scoops up a shovelful of gravel, lugs it to the water's edge and dumps it in. A rainbow sheen of oil spreads across the water.

"Hundreds of gallons of oil are locked up under this beach," he says. "And this isn't isolated. There are hundreds of beaches all over the sound that are still oiled, and the oil is slowly bleeding out.

"The beaches can look beautiful at the surface, but you can dig down, in this case just a few inches below the surface, and find lots of oil. Now, is that a threat or isn't it?"

A year after the wreck of the Exxon Valdez, the question clings like the oil under this Perry Island beach. Certainly, the worst is over; thousands of dead birds no longer wash up on shorelines as they did last summer.

But assessing the continuing damage wrought by the nation's most extensive - and expensive - oil spill has just begun. As a growing slick of lawyers haggles over who is to blame, Exxon Corp. and government agencies debate how to clean up what's left and scientists track wildlife populations' first steps on the long road to recovery.

Any hope of a quick solution faded last summer as oil from the Exxon Valdez spread across 1,100 miles of Alaska's wild southern coast.

A cleanup army of 12,000 workers polished rocks by hand, blasted beaches with hot water and sprayed fertilizer to promote the growth of oil-eating microbes.

But when Exxon suspended its $2 billion cleanup in mid-September, it had recovered only 5 percent to 9 percent of the oil spilled, state officials estimate. About 20 percent to 40 percent is believed to have evaporated. That leaves 50 percent to 75 percent of the oil in the water, on the ocean bottom or on beaches.

Some was soaked up by unwilling sponges: the seabirds, eagles and sea otters whose carcasses now lie frozen in five vans in an Anchorage storage yard, awaiting their day as physical evidence in court.

Workers found more than 1,000 dead otters, a sizable chunk of the spill area's total population of 15,000 to 22,000.

Many of Prince William Sound's 3,000 bald eagles also suffered; at least 151 died, most poisoned by scavenging the oily remains of some of the 34,400 dead seabirds recovered.

Those numbers alone make the Valdez spill the most lethal ever, but scientists say the actual death count is much higher, estimating that up to 90 percent of the seabirds caught in oil sank from sight or drifted out to sea.

Exxon notes the spill did not wipe out any species and says surviving animals and birds will rebuild populations. But that may take up to 70 years for some hard-hit seabird colonies, U.S. Fish and Wildlife Service researchers say.

"We never claimed that the spill put any animal on the endangered species list, but that's missing the point," said Fish and Wildlife spokesman Bruce Batten. "It's still the greatest human-caused wildlife disaster that this agency knows about."

Oily carcasses were an obvious measure of the spill's impact, but victims also included less visible members of the ecosystem, such as young salmon and tiny intertidal creatures.

Assessment studies for these populations are not finished, and even preliminary findings are hard to come by - researchers have been told by lawyers to save their findings for court, where it seems nearly everyone involved in the spill is headed.

Capt. Joseph Hazelwood, skipper of the Exxon Valdez, is on trial this month in Anchorage on charges including criminal mischief and drunken driving of his vessel, and a federal grand jury recently issued criminal indictments against Exxon, starting a case that could take years to finish.

Exxon already faces more than 150 civil lawsuits.

Fishermen sued because of lost seasons. Tour-boat operators sued because fewer people wanted to cruise an oiled sound. The state sued, claiming the company was negligent in responding to the spill, only to be countersued by Exxon, which claimed state officials hindered the use of chemical dispersants that could have broken up large quantities of oil early on.

Information about the spill is filtered through this litigious atmosphere, making much of it suspect. Exxon distributes before-and-after pictures of cleaned beaches; Bridgman and other state officials, accusing Exxon of "myth-making," eagerly make room for journalists on flights to oiled beaches.

State officials cite an October survey that showed 117 miles of shoreline remained moderately or heavily oiled, with oil more than two feet deep in some spots. They say observers flying over the sound still report 15 to 20 oil sheens bleeding off beaches daily.

Exxon officials, meanwhile, say their winter monitoring of 64 sites shows wind and waves have scoured away, on average, more than half the surface oil left in September, and up to 80 percent of the buried oil.

"From a layman's point of view, what's left out there is really insignificant," said Exxon scientist Andy Teal.

Both the state and Exxon figures may be accurate, but even the best studies of the spill's effects are mere snapshots of a rugged, sparsely populated region the size of New Jersey, Maryland and Delaware combined.

The Coast Guard has declared some sort of cleanup must resume May 1, but nobody has committed to how much or what kind. Decisions will be made after another survey of beach conditions next month.

In general, exposed beaches eroded by winter storms appear to have fared the best, but surface oil remains thick in many sheltered coves and estuaries.

Areas with oil hidden beneath the surface, such as the Perry Island beach Bridgman visited, may prove the most troublesome. State officials believe many of those beaches would benefit from intensive work, such as digging up gravel, tumbling it in rock-washing machines and replacing it.

While that would kill nearly all living organisms, it would provide a clean slate for populations to rebuild, said Steve Provant, the Department of Environmental Conservation's spill coordinator.

But Exxon officials say such intrusive techniques could do more harm than good.

Some federal authorities are inclined to agree, recalling last summer's heavy-handed invasion of the Alaska wilderness.

Frightened animals had to flee repeatedly from buzzing helicopters, and cleanup crews left behind tons of plastic boom material, absorbent pompons and other litter on previously pristine beaches. Even scientists made their mark, painting rocks with flourescent paint and tying orange plastic flagging to trees.

"You can see these things a mile away, and they're in areas where people otherwise would be having a quality wilderness experience," said Nancy Lethcoe, a sailboat-tour operator in Valdez.

Lethcoe remembers a Prince William Sound where you could stand on a lonely beach and feel you were the first human ever there. It was a place where the world still felt big. Now the world seems suddenly smaller, civilization's reach extended by the greasy fingers of an oil spill.

Lethcoe said she'll leave the blaming to the lawyers. When she goes out on the sound these days, she focuses on nature's recuperative powers. It works until she discovers that oil has found another of her favorite hideaways.

"When I know an area is oiled, I can brace myself," she said. "But when I find an area that wasn't supposed to be oiled, it brings back the whole trauma of the spill. It brings back the pain."