PROVIDENCE, R.I. — In the wake of any large oil spill, everyone from local residents to fishermen and tourism officials is reassured by the sight of jumpsuited workers cleaning up area beaches.
But new damage estimates from a mid-January spill in Rhode Island have highlighted the limitations of modern oil-spill cleanup technology.
The latest figures from the state's Department of Environmental Management raise the estimated number of lobsters killed in the 800,000-gallon spill from the thousands to the hundreds of thousands. Experts say that numbers could still rise.
That comes as bad news to the lobstermen who work the Harbor of Refuge, which has been as quiet as a fog-bound airport since the state banned lobstering in a 250-square-mile area in the wake of the spill.
Since the tanker Exxon Valdez spilled 11 million gallons of crude oil into Prince William Sound in Alaska seven years ago, oil cleanups have become a symbol of environmental correctness to citizens who want to see something done. Yet news of the damage here has led many residents to question their effectiveness.
''It's a little like Humpty Dumpty,'' says Fred Massie, of Save the Bay, a local environmental group that mobilized some 1,000 volunteers during the Rhode Island spill. ''Once that eggshell breaks, it's hard to put back together again, and it's a losing battle to recover the oil. In the worst-case scenario, some of it is window-dressing, and I think we have to be honest about that.''
The Coast Guard estimates that 16 percent of the Rhode Island slick, or 129,000 gallons, was removed from local waters. Recovering as little as 10 percent is generally considered a success, according to Coast Guard cleanup supervisors.
In many of the major spills since the Valdez, little or no oil has been recovered.
When the tanker Aegean Sea struck the rocks on Spain's northwest coast in 1992, foul weather made containment impossible. Officials eventually set the oil ablaze as a last-ditch effort to minimize the impact. A month later, the tanker Braer gushed 21 million gallons of crude oil off the Shetland Islands, but a hurricane swept the slick away, and scientists are still trying to determine where the oil went. No one thinks recovery - primarily a small-craft, inshore effort - could have been undertaken in a hurricane.
In Rhode Island, the barge North Cape beached in 20-foot seas on Moonstone Beach on Jan. 19, and the thunderous surf swirled oil throughout the water column. Rather than floating, it was dispersed in a cloud that moved invisibly beneath the swells. Samplings by the Environmental Protection Agency found oil at depths of 50 feet. Helicopters could not track it. Skimmers could not catch it.
Even in normal weather, capturing waterborne oil is difficult, as it spreads rapidly on dynamic, moving seas.
One of the first steps in mopping up oil spills is to place booms, buoyant ribbons of plastic, around leaking ships. Since petroleum normally floats on sea water much like corn oil on vinegar, the goal is to trap the oil and recover it with skimmers, ships that inhale oil and hold it in tanks. Empty barges are then brought in, and the remaining shipboard oil is removed before it too spills into the environment. Removing oil from leaking vessels is one of the most effective cleanup procedures, Coast Guard officers say.
Efforts also continue beyond the leaking vessels. Booms are wrapped around sensitive habitats, such as Rhode Island's salt ponds. Skimmers crisscross free-floating slicks before the slicks foul more wildlife or strike another coast.
On shore, work crews fight coastal damage. In many ways the Rhode Island effort was typical: A rescue center treated oil-coated birds. Miles of booms snaked around marshes. And four skimmers combed the water near the grounded barge.
Spill supervisors are aided by aerial observation, weather reports, and computer modeling, which together help predict a slick's path. Protective efforts begin ahead of the slick's arrival.
Finally, bioremediation can augment natural processes to ease environmental damage.
In Alaska, scientists claimed to reduce hydrocarbon concentrations by 44 to 90 percent by spreading fertilizer to accelerate the growth of bacteria that attack hydrocarbons such as oil.
All of these are expensive, labor-intensive solutions, and the efforts rarely meet public expectations.
''It's just all show,'' says Robert Lyons, who owns the Ocean House Marina, just west of where the North Cape struck. ''Some of it ... didn't do a ... thing.''
Coast Guard Lt. Timothy Pavilonis goes further: ''You go into these tidal zones, where there's a foot or so of water, and your equipment can drive the oil into silt and do more harm than help.'' In some cases, if it's left on the surface ''where people don't think that it looks nice,'' it may go away more quickly, he says. ''But sometimes that's hard to make the public understand.''
Complicating containment of the Rhode Island spill was the fact that the southwest coast of Rhode Island is dotted with eight saltwater ponds, which draw in ocean water through narrow raceways. Their entrances run like rivers during tidal changes.
Booms, which become ineffective when currents exceed 0.7 knots, could not keep oil out. Recovery has now been left to natural processes.