Twenty years after the Exxon Valdez spilled 11 million gallons of crude oil in Alaska's Prince William Sound, oil persists in the region and, in some places, "is nearly as toxic as it was the first few weeks after the spill," according to the council overseeing restoration efforts.
"This Exxon Valdez oil is decreasing at a rate of 0-4 percent per year," the Exxon Valdez Oil Spill Trustee Council stated in a report marking Tuesday's 20th anniversary of the worst oil spill in U.S. waters. "At this rate, the remaining oil will take decades and possibly centuries to disappear entirely."
The council's findings come two decades after the March 24, 1989 disaster, when the single-hulled Exxon tanker hit a reef, emptying its contents into Alaskan waters. The spill contaminated more than 1,200 miles of shoreline and killed hundreds of thousands of seabirds and marine animals.
Captain convicted of misdemeanor
The council, made up of three state and three federal appointees, was created to administer the $900 million that Exxon paid to settle lawsuits filed after the accident, which also resulted in criminal charges against the ship's captain, Joseph Hazelwood.
Hazelwood, was accused but then acquitted on a charge of being drunk at the time. He was, however, convicted of negligent discharge of oil, a misdemeanor, and sentenced to a $50,000 fine and 1,000 hours of community service.
In the weeks and months following the spill, thousands of people tried to clean up the contamination. But two decades later, oil persists and is estimated to total around 20,000 gallons, according to the council. One of the lessons learned is that a spill's impacts can last a long time in a habitat with calm, cold waters like Prince William Sound, the council said.
"Following the oil and its impacts over the past 20 years has changed our understanding of the long-term damage from an oil spill," the council stated. "We know that risk assessment for future spills must consider what the total damages will be over a longer period of time, rather than only the acute damages in the days and weeks following a spill."
"One of the most stunning revelations" from studies over the last decade, the council said, "is that Exxon Valdez oil persists in the environment and, in places, is nearly as toxic as it was the first few weeks after the spill."
As a result, some sea otter populations as well as bird species have been slow to recover. Overall, some 200,000 seabirds and 4,000 otters were thought to have died from the contamination.
Oil found 450 miles away
Moreover, surveys "have documented lingering oil also on the Kenai Peninsula and the Katmai coast, over 450 miles away," according to the council.
None of that was expected "at the time of the spill or even ten years later," it added. "In 1999, beaches in the sound appeared clean on the surface. Some subsurface oil had been reported in a few places, but it was expected to decrease over time and most importantly, to have lost its toxicity due to weathering. A few species were not recovering at the expected rate in some areas, but continuing exposure to oil was not suspected as the primary cause."
It turns out that oil often got trapped in semi-enclosed bays for weeks, going up and down with the tide and some of it being pulled down into the sediment below the seabed.
"The cleanup efforts and natural processes, particularly in the winter, cleaned the oil out of the top 2-3 inches, where oxygen and water can flow," the council said, "but did little to affect the large patches of oil farther below the surface."
Sea otter concerns
That area is also biologically rich with mussels, clams and other marine life that help sustain sea otters and ducks.
"Sea otters usually have very small home ranges of a few square kilometers," the council said. "In these small ranges, it is unlikely that the otters are avoiding areas of lingering oil when foraging.
As a result, "while overall population numbers in western Prince William Sound have recovered, local populations in heavily oiled areas have not recovered as quickly."
There is a plus side to the foraging by otters, since digging in oiled areas does release the contaminants to the water, where they are diluted and dispersed.
The American Bird Conservancy issued its own warning, stating that while many bird species have recovered several significant ones have not.
The spill killed 5-10 percent of the world's population of Kittlitz's Murrelets, the group said, a species whose numbers declined 99 percent from 1972 to 2004.
"Prior to the spill, the rate of decline was 18 percent per year, but since 1989 that rate has increased to 31 percent," the group stated. "The growing impact of global warming in the Arctic and the melting of glaciers, caused by the burning of oil and other fossil fuels, may also be a factor in this decline."
Two other species cited are: the Pigeon Guillemot, whose populations have steadily declined throughout the sound since the spill; and the Marbled Murrelet, which has not met the recovery objective of a stable population.
The group cited a faster transition to double-hulled oil tankers as the best protection for wildlife. Single-hulled tankers are still allowed in U.S. waters until 2015.
"A similar requirement for double-hulled tankers needs to be made globally to protect birds and other wildlife from future spills," said Michael Fry, the group's conservation director. "Additional marine reserves and no-go zones for tankers during sensitive breeding and staging seasons should also be implemented to protect the most vulnerable species."