In 1989, the Exxon Valdez spilled 10.8 million gallons of oil into Alaska’s Prince William Sound. Twelve years after the spill, oil could still be found on half of the 91 randomly selected beaches surveyed. Three species of cormorant, the common loon, the harbor seal, the harlequin duck, the pacific herring and the pigeon guillemot still have not fully recovered. More than 21,000 gallons of crude oil remain, according to a 2007 National Oceanic and Atmospheric Administration report. Just scratch the surface of many beaches, and the thick crude oil is evident beneath.
In November 2005, approximately 1.9 million gallons of oil was released into the Gulf of Mexico when tank barge DBL 152 struck the submerged remains of a pipeline service platform that collapsed a few months earlier during Hurricane Rita. The double-hulled barge was carrying approximately 5 million gallons of slurry oil, a type of oil denser than seawater, which meant as the thick oil poured out of the barge, it sank to the seafloor. As could be expected, an environmental assessment showed that fish and organisms living on or near the ocean floor (such as worms, clams, and crabs) were injured by the oil that sank to the bottom of the Gulf of Mexico. That submerged oil impacted approximately 45,000 acres of ocean floor. More than 7 years later, no cleanup of this oil resting on the ocean floor has even been attempted. In March 2013, NOAA released the Damage Assessment and Restoration Plan for the DBL 152 incident, which suggests that restoration in the form of mitigation is possible for this oil spill. The plan outlines injuries to natural resources and proposes a restoration project to implement estuarine shoreline protection and salt marsh creation at the Texas Chenier Plain National Wildlife Refuge Complex in Galveston Bay, Texas.
Oh, and you just may have heard of the Deepwater Horizon disaster in the Gulf of Mexico in April 2010 where approximately 210 million gallons of oil were released. Despite a massive cleanup effort by the US Coast Guard and private contractors, millions of gallons of oil remain either unaccounted for or, like the oil from DBL 153, deposited on the ocean floor. The environmental and human health impacts will likely be felt for many years.
So, how long does it take to clean up an oil spill? Nobody knows.