Case Study of Exxon Valdez oil spill?

Answer 1

At 12:04 am on March 24, 1989, an oil tanker known as the Exxon Valdez ran aground on the Bligh Reef off the coast of Alaska. The ship was carrying 53,094,510 gallons of oil at the time, and approximately 10.8 million gallons of the total spilled into the Prince William Sound, with devastating effects. While this spill no longer ranks among the top 50 in the amount of oil spilled, the destruction it wreaked on the pristine surrounding environment has won it a lasting stance as the number one spill in the world in terms of damage caused. The number of direct animal fatalities is impossible to ascertain, as most carcasses sink. However, the best estimates are around 250,000 seabirds, 2,800 sea otters, 300 harbor seals, 250 bald eagles, up to 22 killer whales, and uncountable billions of salmon and herring eggs. And as these only compromise the outright deaths from the spill, the true damage counts would have been much higher.

The exact cause of the spill has been difficult to pinpoint. Numerous factors have been identified, ranging from excessive fatigue and workload on the part of the Third Officer piloting the ship at the time of the crash to failure of the ship's master (who may have been under the influence at the time) to properly man the deck to failure of Exxon to provide a sufficient crew (the tanker was crewed by only 19 men) to failures on the parts of the U.S. Coast Guard to provide effective vessel traffic services. Regardless of the exact placement of the blame, however, individuals and organizations worldwide have recognized a failure to observe sufficient caution, a complacency that was immediately revoked in the aftermath of the spill.

Steps were taken to mediate the effects of the spill quickly after the impact occurred. Booms were completely deployed around the ship 35 hours after the grounding occurred. On March 25 and 26, Exxon conducted successful burn and dispersant tests. An estimated 15,000 to 30,000 gallons of oil were collected in the burn test and were reduced to easily collectable residue with an estimated 98% efficiency on March 25, and oil dispersants were deployed on the 26th. However, on the evening of the 26th a large storm arose, with the consequence of converting much of the oil into mousse. As neither burning nor dispersants are effective on oil in the form of mousse, the use of both methods was discontinued.

As it became clear that the spill was not containable, more booms were deployed to protect fish hatcheries and salmon streams, which were identified as having the highest priority for protection. Other methods of open water oil reclamation and cleanup included skimmers and sorbents, but both these mechanical methods were accompanied by costs in the forms of manpower and high amounts of waste produced, and so neither was entirely effective. Despite everyone's best efforts, the oil spread 460 miles, with 1,300 miles of coastline showing impacts.

Cleanup of any spill is not a simple process, and that fact has been made painfully clear in the case of the Exxon Valdez. The matter is further complicated by the consideration that the cleanup itself is a disturbance to the organisms present in beach habitats. A 1996 study takes the view that both the spill and the cleanup are a part of the same "pulse perturbation", a one-time short-term alteration of some component of an ecological system. While both prior and subsequent studies rather sharply contradict the idea that oil spills are only a short-term perturbation, the same study is correct to recognize the dangers inherent in many of the cleanup methods employed after the Exxon Valdez leaked its toxic cargo into the sound.

The main methods used in the cleanup of the Exxon Valdezspill were high pressure water treatments, both hot and cold, bioremediation, and mechanical cleanup. While all of these have their prices, the high pressure water treatments arguably may cost more than they provide. High pressure water treatments consist of workers spraying the beaches with hoses to wash the oil-laden water down to be scooped up or absorbed by special oil-absorbent materials. When hot water was used, it essentially cooked some of the smaller organisms present on the beaches. And even when cold water was employed, the sheer force of the water would often clear organisms and substrate along with the oil. The mortality rate of mussels went up by 20 times in high pressure water treated areas, and mean species diversity was reduced by over 50% in sample 0.25 m2 quadrats. A further 75% mortality of clams resulted when oil dispersant was added to hot water in this treatment. There is even some speculation that sediments disturbed in the process will smother subtidal organisms, although there is not specific research to back claim. High pressure water treatments generally remove an estimated 15% to 27% of oil cover on rocks. In summary, though, recovery at sites cleaned by high pressure water treatments often occurred more slowly than at non-cleaned sites, in comparison with pristine habitats.

Bioremediation has been considered to generally be both more effective and less harmful than high pressure water treatments. Bioremediation is the degradation of petroleum products by microorganisms. To encourage the growth of these naturally occurring organisms, fertilizers were added to many oiled shorelines with promising results, and bioremediation was generally pronounced a success beaches where the oil cover was not too thick. However, further investigations suggest that the attempted eutrophication by the input of fertilizer did not occur, nor were microorganism counts significantly elevated by that input. One study even suggests that bioremediation may help to reduce oil when applied early after a spill, but that the effectiveness of this approach, especially considered in combination with the potentially deleterious effects the fertilizer input could be having in the subtidal zone, is questionable.

In total, there were more than four summers of dedicated cleanup efforts before the attempts were called off. Even after the tens of thousands of workers, hundreds of boats, planes, and helicopters, and approximately $2.1 billion spent by Exxon alone in the cleanup, however, there are still oiled beaches present on the Alaskan coast today. Furthermore, it has since been recognized the wave action from winter storms likely contributed more to the cleaning of the beaches than the entirety of the human efforts combined.

It is difficult to assess the extent of recovery after oil spills, as typically there is a lack of baseline data, describing the status of the oil-impacted habitats prior to the spill. A 2001 study attempts to define a new set of qualifications to determine the level of recovery of the Exxon Valdez spill site, as well as other spill sites worldwide. Using parallelism between oiled and unoiled sites, the study considered the extent (both in physical length and time span) of oil coverage and the presence of algae, intertidal epibiota, and infauna to assess recovery. The study concluded most species were showing definite signs of recovery, although most had still not reached the levels of abundance of unoiled control sites. Eight years later, the area is still not considered entirely recovered. The Exxon Valdez Oil Spill Trustee Council's official assessment of the status of injured resources and services lists ten indicator species/resources (including killer whales, mussels, intertidal communities, and sediments) as still recovering and highlights two (the Pacific Herring and Pigeon Guillemots) as showing no significant recovery since the time of the spill. The assessment also takes into consideration the economically and aesthetically important human services disrupted by the spill, and finds them all to still be in a status of incomplete recovery.

The Exxon Valdez has been repaired, and is today used to ship oil across the Atlantic under its new name, the Sea River Mediterranean. The tanker has, however, been prohibited by law from ever returning to the Prince William Sound.