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Lingering Oil
Updated 2014

Oil Remains: The Persistence, Toxicity, and Impact of Exxon Valdez Oil

NOAA Lingering Oil Report (Jan 2010)

Visitors today experience the spectacular scenery and wildlife of Prince William Sound and the North Gulf of Alaska. However, one of the most stunning revelations of Trustee Council-funded monitoring over the last ten years 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.

This was not expected at the time of the spill or even ten years later. 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.

Oil from the <em>Exxon Valdez</em> persists in a shallow pit dug on a beach in Prince Willaim Sound, summer 2004. In 2001, researchers at the Auke Bay Laboratories, NOAA Fisheries, conducted a survey of the mid-to-upper intertidal in areas of the sound that were heavily or moderately oiled in 1989. Researchers dug over 9,000 pits, at 91 sites, over a 95-day field season. Over half the sites were contaminated with Exxon Valdez oil. Oil was found at different levels of intensity from light sheening; to oil droplets; to heavy oil where the pit would literally fill with oil. They estimated that approximately 16,000 gallons (60,000 liters), of oil remained. The survey also showed a trend of an increasing number of oiled pits as they surveyed lower into the intertidal zone, indicating that there was more oil to be found lower down the beach. In 2003, additional surveys determined that while the majority of subsurface oil was in the mid-intertidal, a significant amount was also in the lower intertidal. The revised estimate of oil was now more than 21,000 gallons (80,000 liters). Additional surveys outside Prince William Sound have documented lingering oil also on the Kenai Peninsula and the Katmai coast, over 450 miles away.

The amount of Exxon Valdez oil remaining substantially exceeds the sum total of all previous oil pollution on beaches in Prince William Sound, including oil spilled during the 1964 earthquake. This Exxon Valdez oil is decreasing at a rate of 0-4% per year, with only a 5% chance that the rate is as high as 4%. At this rate, the remaining oil will take decades and possibly centuries to disappear entirely.

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