The Exxon Valdez oil spill in 1989 was a major environmental disaster in U.S. history. It prompted an unprecedented cleanup effort in a remote, ecologically sensitive region. This article details the techniques employed to mitigate its extensive environmental impact.
The Exxon Valdez Incident Context
On March 24, 1989, the oil tanker Exxon Valdez struck Bligh Reef in Prince William Sound, Alaska, spilling approximately 11 million gallons of crude oil into its pristine waters. The collision tore open its hull. Its remote location complicated initial response efforts. The spill threatened a region abundant with salmon, sea otters, seals, and seabirds, affecting an estimated 1,300 miles of coastline, with about 200 miles heavily oiled.
Primary Cleanup Techniques Deployed
Cleanup efforts involved traditional and experimental techniques to address widespread contamination. Mechanical cleanup, utilizing booms and skimmers, began shortly after the spill. Booms corralled the oil, while skimmers physically removed it. However, their effectiveness was limited by thick oil and kelp clogging equipment, and they were not readily available in the critical first 24 hours. This method recovered about 8.5% of the original spill volume in 1989.
High-pressure hot water washing was a controversial technique for cleaning rocky shorelines. Crews sprayed hot water directly onto oiled rocks, effective in loosening the tar-like crude oil. However, this method damaged intertidal marine life, removing or debilitating organisms. Its use was later determined to have caused more harm than the oil itself in some instances, by cooking small organisms.
Manual cleanup involved thousands of workers and volunteers. This process included wiping oil from rocks, using absorbent materials, and collecting oiled debris by hand. Over 11,000 Alaska residents and Exxon employees participated in these efforts for several years. This approach was essential for areas inaccessible to larger equipment and sensitive habitats.
Chemical dispersants were considered to break down oil into smaller droplets for natural degradation. Their use was limited and debated due to environmental impact concerns. A trial application was discontinued due to insufficient wave action to mix the dispersant with the oil.
Bioremediation involved applying fertilizers to shorelines to stimulate naturally occurring oil-eating microbes. These microbes, which degrade hydrocarbons, broke down crude oil more quickly with added nutrients like nitrogen and phosphorus. This method was used for heavily oiled shorelines and light-to-moderately oiled areas, proving effective in accelerating oil removal in some locations.
Challenges and Limitations of Cleanup Efforts
Cleanup faced significant obstacles due to Prince William Sound’s remote location and harsh weather. The rugged Alaskan coastline made access difficult, requiring extensive use of helicopters, planes, and boats for personnel and equipment transport. Severe weather, including storms and cold temperatures, frequently hampered operations and sometimes forced their suspension.
The specific properties of the crude oil also presented considerable challenges for recovery. The oil, extracted from Prudhoe Bay, tended to emulsify into a sticky, persistent mousse when mixed with water. This emulsification made the oil harder to recover with mechanical skimmers, as it clogged equipment, and it increased the oil’s persistence in the environment.
Initial lack of preparedness and readily available equipment further limited the immediate response. Despite existing contingency plans, the scale of the spill overwhelmed the available resources, leading to delays in deploying effective containment and recovery tools. This shortage of equipment and trained personnel hindered the initial efforts to contain the rapidly spreading oil.
Decisions regarding cleanup techniques also had to balance effectiveness with potential harm to the delicate environment. For instance, while hot water washing removed oil, it also caused damage to the intertidal ecosystem, leading to prolonged recovery times for marine life in those areas. Environmental sensitivity required careful consideration of which techniques could be applied without causing additional long-term damage.
Natural Recovery and Ongoing Monitoring
Despite the extensive cleanup operations, a significant amount of oil remained in the environment, particularly buried in sediments and within the subsurface of beaches. This lingering oil, though a fraction of the original spill, remained toxic and continued to affect wildlife for decades, degrading at a far slower rate than initially anticipated. Studies conducted years later still found oil in a patchy distribution beneath beach surfaces, especially in areas where it was sequestered from natural weathering processes.
Ecosystem recovery has been a slow and gradual process for various species and habitats in Prince William Sound. While some populations, such as sea otters and bald eagles, showed signs of recovery over time, others, like certain killer whale pods and herring populations, experienced prolonged impacts or did not fully rebound to pre-spill levels even decades later. This demonstrates the long-term ecological consequences of such a large-scale disaster.
Extensive scientific monitoring and research continued for many years after the initial cleanup. The Exxon Valdez Oil Spill Trustee Council and organizations like NOAA conducted long-term studies to assess the environmental impacts, track the recovery of injured resources, and understand the fate and persistence of the spilled oil. This ongoing monitoring has provided valuable insights into ecosystem resilience and the long-term effects of oil pollution.