Workers using high-pressure, hot-water washing to clean an oiled shoreline
There was use of a dispersant, a surfactant and solvent mixture. A private company applied dispersant on March 24 with a helicopter and dispersant bucket. Because there was not enough wave action to mix the dispersant with the oil in the water, the use of the dispersant was discontinued. One trial explosion was also conducted during the early stages of the spill to burn the oil, in a region of the spill isolated from the rest by another explosion.[clarification needed] The test was relatively successful, reducing 113,400 liters of oil to 1,134 liters of removable residue, but because of unfavorable weather no additional burning was attempted. The dispersant Corexit 9580 was tried as part of the cleanup. Corexit has been found to be toxic to cleanup workers and wildlife while breaking down oil.
Mechanical cleanup was started shortly afterwards using booms and skimmers, but the skimmers were not readily available during the first 24 hours following the spill, and thick oil and kelp tended to clog the equipment.
Exxon was widely criticized for its slow response to cleaning up the disaster and John Devens, the mayor of Valdez, has said his community felt betrayed by Exxon's inadequate response to the crisis. More than 11,000 Alaska residents, along with some Exxon employees, worked throughout the region to try to restore the environment.
Clean-up efforts after the Exxon Valdez oil spill
Because Prince William Sound contained many rocky coves where the oil collected, the decision was made to displace it with high-pressure hot water. However, this also displaced and destroyed the microbial populations on the shoreline; many of these organisms (e.g. plankton) are the basis of the coastal marine food chain, and others (e.g. certain bacteria and fungi) are capable of facilitating the biodegradation of oil. At the time, both scientific advice and public pressure was to clean everything, but since then, a much greater understanding of natural and facilitated remediation processes has developed, due somewhat in part to the opportunity presented for study by the Exxon Valdez spill. Despite the extensive cleanup attempts, less than ten percent of the oil was recovered and a study conducted by NOAA determined that as of early 2007 more than 26 thousand U.S. gallons (98 m3) of oil remain in the sandy soil of the contaminated shoreline, declining at a rate of less than 4% per year.
Both the long-term and short-term effects of the oil spill have been studied. Immediate effects included the deaths of, at the best estimates, 100,000 to as many as 250,000 seabirds, at least 2,800 sea otters, approximately 12 river otters, 300 harbor seals, 247 Bald Eagles, and 22 orcas, as well as the destruction of billions of salmon and herring eggs. The effects of the spill continued to be felt for many years[quantify] afterwards. Overall reductions in population were seen in various ocean animals, including stunted growth in pink salmon populations. The effect on salmon and other prey populations in turn adversely affected killer whales in Prince William Sound and Alaska's Kenai Fjords region. Eleven members (about half) of one resident pod disappeared in the following year. By 2009, scientists[who?] estimated the AT1 transient population (considered part of a larger population of 346 transients), numbered only 7 individuals and had not reproduced since the spill, this population is expected to die out. Sea otters and ducks also showed higher[quantify]death rates in following years,[quantify] partially because they ingested prey from contaminated soil and from ingestion of oil residues on hair due to grooming.
Some twenty years after the spill, a team from the University of North Carolina found that the effects were lasting far longer than expected. The team estimates some shoreline Arctic habitats may take up to thirty years to recover. The spill occurred on March 24, 1989.[clarification needed] Exxon Mobil denies any concerns over this, stating that they anticipated a remaining fraction that they assert will not cause any long-term ecological impacts, according to the conclusions of 350 peer-reviewed studies. However, a NOAA study concluded that this contamination can produce chronic low-level exposure, discourage subsistence where the contamination is heavy, and decrease the "wilderness character" of the area.