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OIL SPILL FACTS >
Lingering Oil
The western portion of Prince William Sound was the most heavily oiled in 1989 and oil on some beaches remains a serious concern for residents of Prince William Sound who traditionally use these areas for hunting, fishing, and gathering. Exxon Valdez oil penetrated deeply into cobble and boulder beaches that are common on shorelines throughout the spill area, especially in sheltered habitats that don’t receive much winter storm action. Cleaning and natural degradation removed much of the oil from the intertidal zone, but visually identifiable surface and subsurface oil persists at many locations. A 1989-90 survey of nearly 5,000 miles of shoreline documented oil on approximately 1,300 miles of beach. The oiling was considered heavy or medium on 200 miles of shoreline. The remaining 1,100 miles of oiled shoreline were considered to have light or very light oiling. When crews returned to the beaches in 1993, they found hundreds of sites that contained substantial oil deposits.
In 1998, preliminary analysis of targeted sites showed that the cleanup method was largely effective in removing the visible surface oil. But it had little effect on the large deposits of oil beneath rocks and overburden. Winter storms rearranged the beaches, exposing large quantities of oil that never received treatment. NOAA’s Auke Bay Lab found no biological injury due to the cleanup. The most recent survey of lingering oil was conducted in the intertidal zone of Prince William Sound in Summer 2001 by NOAA’s Auke Bay Lab. The survey covered roughly 8,000 meters of shoreline. Ninety-six sites were randomly selected from the total number of oiled beaches assessed during previous Trustee Council surveys. The survey results indicate a total area of approximately 20 acres of shoreline in Prince William Sound are still contaminated with oil. Oil was found at 58 percent of the 91 sites assessed and is estimated to have the linear equivalent of 5.8 km of contaminated shoreline. Buried or subsurface oil is of greater concern than surface oil. Subsurface oil can remain dormant for many years before being dispersed and is more liquid, still toxic, and may become biologically available. A disturbance event such as burrowing animals or a severe storm reworks the beach and can reintroduce unweathered oil into the water. Results of the 2001 survey showed that the oil remaining on the surface of beaches in Prince William Sound is weathered and mostly hardened into an asphalt-like layer. The toxic components of this type of surface oil are not as readily available to biota, although some softer forms do cause sheens in tide pools. The survey raised the possibility of continuing low level chronic effects of the Exxon Valdez oil spill, although measurable population effects would be very difficult to detect in wild populations. If there are continuing effects, it would be most likely restricted to populations residing or feeding in the isolated oil pockets. Sea otters and harlequin ducks fall into this category. Researchers have been monitoring these populations’ poor recovery in heavily oiled areas since the 1989 spill. The 2001 shoreline survey has provided new insights for possible sources of continued oil contamination. This has stimulated future studies that will focus on the bioavailability of the oil and its impacts on species such as sea otters, harlequin ducks, and their intertidal prey. For more detail on the Summer 2001 shoreline survey, click here: http://www.afsc.noaa.gov/Quarterly/jas2001/feature_jas01.htm
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In 1997, eight years after the oil spill,
villagers from Chenega Bay returned to nearby beaches to clean some
of the most heavily-oiled sites. Under the guidance of the Alaska
Department of Environmental Conservation, the crew of mostly-local
residents applied a chemical agent to the weathered oil at five
sites, along about one-half mile of beach on LaTouche and Evans
islands. They used PES-51, a citrus-based product from the oil of
oranges and lemons. PES-51 binds to the oil and floats, allowing
both the chemical agent and the oil to be collected through the use
of oil-absorbent pads.
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