The largest oil spill in U.S. history was even bigger than previously thought, at least in terms of the amount of coastline that was oiled, scientists report in a new study. The findings shed new light onto the BP Deepwater Horizon disaster in the Gulf of Mexico, which began six years ago Wednesday.
Scientists from the federal government's National Oceanic and Atmospheric Administration and several private research companies found oil along 1,313 miles (2,113 kilometers) out of 5,930 miles (9,545 kilometers) of surveyed shoreline after the spill, an increase of 19 percent from previously published estimates. That makes the disaster the largest marine oil spill in history by length of shoreline oiled, the team reported in the journal Marine Pollution Bulletin.
The spill released millions of barrels of oil into the Gulf over 87 days, from April 20 to July 15, 2010, in a dramatic event that shocked the world. Some of the oil was recovered, burned, or dispersed at sea, while some washed up on the shorelines of Louisiana, Alabama, Mississippi, Florida, and Texas.
To estimate the complete extent of the oil's reach, the scientists pored over all the available ground-based data on the area, including recent data from cleanup efforts. The team members hope their work will provide a more clear picture of the spill and help managers better predict and understand future accidents.
The scientists found the majority of the oiling in Louisiana, with significant oiling in Mississippi, Alabama, Florida, and, to a lesser extent, Texas.
The team also found that the oiled shoreline was roughly evenly split between beaches (46 percent) and coastal wetlands (52 percent), with the remaining 2 percent being all other shoreline types. Most of the wetlands were in Louisiana.
The behavior of that oil in the shoreline environment has been complex, the team adds. Some was removed or treated by cleanup crews, some degraded naturally, some soaked into the soil, and some remains at the surface. Additional oil was also deposited months after the initial spill, due to the drifting of currents.
Environmentalists have argued that all that oil has had a lasting impact on the Gulf, even as initial fears of mass die-offs didn't materialize.
"The impacts on dolphins, sea turtles, and many other species are still being felt today," Collin O’Mara, president and CEO of the National Wildlife Federation, says in a statement this week.
The National Wildlife Federation says more than three-quarters of pregnant bottlenose dolphins in the oiled areas failed to give birth to a viable calf in the years since the disaster. Between two and five trillion larval fish and 8.3 billion oysters are estimated to have been lost, resulting in a substantial impact to the region's fishery. Threatened gulf sturgeon and Bryde's whales are also thought to have been harmed.
About 30 percent of the oil thought to have been spilled is still unaccounted for, with the industry hotly debating the issue with conservationists. Some scientists think it must have sunk to the ocean bottom, where it may be harming communities there, but efforts to find it have proven elusive.
BP finalized a $20.8 billion settlement last October in response to the spill, representing the largest pollution penalty in U.S. history.
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Deepwater Horizon oil spill
We see it on the news every day, usually in snippets and soundbites. Now you can learn the details of the BP Oil Spill, a disaster that is anticipated to eclipse that of the historic Exxon Valdez.Researched and written by Boston University professor Cutler J. Cleveland, this comprehensive news story will take you through each step of the spill from how it happened and what’s being done to stop it, to the ecological and environmental impacts and what the government proposes to to.
This story first appeared in The Encyclopedia of Earth
The Deepwater Horizonoil spill (also known as the Gulf of Mexico Oil Spill or the BP Oil Spill) is a large ongoing oil spill caused by an explosion on the Deepwater Horizon offshore oil platform 40 miles southeast of the Louisiana coast on April 20, 2010. Most of the 126 workers on the platform were safely evacuated, and a search and rescue operation began for 11 missing workers. On April 22, 2010 The Deepwater Horizon sank in about 5,000 feet (1,500 m) of water; on April 23, 2010 the U.S. Coast Guard suspended the search for missing workers. All are presumed dead.
BP was the principal developer of the Macondo Prospect oil field where the accident occurred. The Deepwater Horizon, owned by Transocean Ltd., was under a contract with BP to drill an exploratory well. BP was the lessee and principal developer of the Macondo Prospect oil field in which the rig was operating. At the time of the explosion, BP and Transocean were in the process of closing the well in anticipation of later production. Halliburton had recently completed cementing casings in the well.
The U.S. Government has named BP as the responsible party in the incident and will hold the company accountable for all cleanup costs resulting from the oil spill. BP has accepted responsibility for the oil spill and the cleanup costs but indicated that the accident was not their fault as the rig was run by Transocean personnel.
The sinking of the platform caused crude oil to gush out of the riser — the 5,000-foot pipe that connects the well at the ocean floor to the drilling platform on the surface. Attempts to shut down the flow, first estimated at about 1,000 barrels of oil a day, failed when a safety device called a blowout preventer could not be activated. On April 28, 2010 government officials said there were three leaks and the well was spilling over 5,000 barrels of oil a day — over 200,000 gallons — nearly a mile below sea level. The exact spill flow rate is uncertain and is part of an ongoing debate. Some independent estimates made in the initial days of the accident put the spill rate in the range of 20,000 to 100,000 barrels per day. By May 22, one month after the Deepwater Horizon sank, a spill rate of 5,000 barrels per day would have released about 150,000 barrels; a spill rate of 100,000 barrels per day would have released about 3.2 million barrels.
By the Numbers
- The largest oil spill in U.S. waters is the 1989 wreck of the Exxon Valdez, which released about 250,000 barrels (10.8 million gallons) of crude oil into Prince Williams Sound in Alaska.
- In 2005, Hurricane Katrina caused a spill of eight million gallons of refined oil products in to the Gulf of Mexico that caused significant damage to ecosystems and wildlife.
- In 1979-80, the Ixtoc 1 exploratory well operated by the PEMEX, the Mexican national oil corporation, experienced a blowout and ultimately released about 3.3 million barrels (140 million gallons) of crude oil into the Bay of Campeche in Mexico. Ixtoc did not cause major onshore damage.
The oil slick produced by the Deepwater Horizon oil spill has covered as much 16,000 square miles (41,424 square kilometers), an area about twice the size of the state of New Jersey, with the exact size and location of the slick fluctuating from daily depending on weather conditions. In the weeks following the accident, scientists discovered enormous oil plumes in the deep waters of the Gulf of Mexico. The discovery suggested that that the leak from the broken undersea well could be worse than estimates that the government and BP have given.
The surface slick threatens the ecosystems and the economy of the entire Gulf Coast region, especially Louisiana, Mississippi and Alabama. The U.S. Fish and Wildlife Service reported that up to 32 National Wildlife Refuges could potentially be affected by the spill. Concerns have also been raised about the environmental impacts of chemical known as dispersants that have been used to dissipate the oil slick. By May 21,2010 the National Oceanic and Atmospheric Administration (NOAA) had banned fishing in almost 20% of federal waters, or 48,005 sq mi (124,333 sq km) of the Gulf.
With oil still flowing from the leak one month after the accident, it was clear that the oil industry’s impressive ability to extract oil from ever deeper offshore environments had not been accompanied by an equally effective capability to predict and respond to accidents. As drillers pushed the boundaries, regulators didn’t always mandate preparation for disaster recovery or perform independent monitoring. Documents and testimony from Congressional hearings revealed a series of potential failures and warning signs at the well site in the hours leading up to the rig explosion, as well as questions that had been raised years earlier about the reliability of deepwater technology and the ability of the industry to deal with “worse-case scenarios.”
Deepwater Horizon was an ultra-deepwater, dynamically positioned, column-stabilized, semi-submersible mobile offshore drilling unit (MODU). The rig was 396 feet (121 m) long and 256 feet (78 m) wide and could operate in waters up to 8,000 feet (2,400 m) deep, with a maximum drill depth of 30,000 feet (9,100 m). Built by Hyundai Heavy Industries in South Korea and completed in 2001, the rig was owned by Transocean Ltd. and leased to BP until September 2013. At the time of the explosion, the rig was on BP’s Mississippi Canyon Block 252, referred to as the Macondo Prospect, in the United States sector of the Gulf of Mexico, about 41 miles (66 km) off the Louisiana coast. The rig commenced drilling in February 2010 at a water depth of approximately 5,000 feet (1,500 m). The well was planned to be drilled to 18,000 feet (5,500 m), and was to be plugged and abandoned for subsequent completion as a subsea producer.
Explosion and fire
The fire aboard the Deepwater Horizon reportedly started at 9:45 p.m. CST on April 20, 2010. Survivors described the incident as a sudden explosion that gave them less than five minutes to escape as the alarm went off. Video of the fire shows billowing flames, taller than a multistory building. After burning for more than a day, Deepwater Horizon sank on April 22, 2010.
The precise cause of the explosion and fire that led to the oil spill are under investigation. Transocean, Ltd., representatives said workers had been performing their standard routines with “no indication of any problems” just prior to the explosion. At that time the rig was drilling but was not in production, however production casing was being run and cemented at the time of the accident. Once the cementing was complete it was due to be tested for integrity and a cement plug set to temporarily abandon the well for later completion as a subsea producer. Halliburton said that it had finished cementing 20 hours before the fire erupted. Interviews with rig workers suggest that a bubble of methane gas escaped from the well and shot up the drill column, expanding quickly as it burst through several seals and barriers before exploding. Transocean chief executive Steven Newman stated: “there was a sudden, catastrophic failure of the cement, the casing or both.”
Casualties and rescue efforts
At the time of the explosion there were 126 people aboard the Deepwater Horizon platform; of these, 115 individuals were evacuated. Most of the workers took diesel-powered fiberglass lifeboats to the M/V Damon B Bankston, a workboat that BP had hired to service the rig; some were then lifted from the workboat by helicopter to regional trauma centers. The United States Coast Guard launched a rescue operation involving two cutters, four helicopters and a rescue plane.
Magnitude of the spill
On Friday, April 23, 2010 two remotely operated underwater vehicles (ROVs) began scanning the riser to determine if there were any leaks. The discovery of two leaks was made Saturday morning. BP, and the Coast Guard initially reported that about 1,000 barrels of oil per day were coming from the leaks on the riser. On April 28, 2010 NOAA estimated the leak was likely 5,000 barrels (210,000 US gallons) per day due in part to the discovery of a third leak. The 5,000 barrel per day figure remained a BP and government doctrine for a month after the accident.
On May 12, 2010, BP released a 30 second video clip of the leak taken by a camera mounted to an ROV, which ignited a debate over the magnitude. At the request of Senator Bill Nelson (Florida) and Barbara Boxer (California), BP released four more videos. Multiple scientists reviewed the videos, remotely sensed data, and information on the subsurface plume, and concluded that the leak rate was much higher than what BP and the government had reported. In a U.S. Congressional testimony on May 19, 2010, Steve Wereley, a professor of mechanical engineering at Purdue University, reviewed the independent leak rate assessments and reported a range of 20,000 to 100,000 barrels per day. These estimates are far greater than the rate of 5,000 barrels per day cited by BP and the U.S. government. At the higher leak rates, it would take a few days, at most a week, for the spill to exceed the Exxon Valdez oil spill’s record.
On May 21, 2010, the New York Times published the estimates made by a group of independent scientists. The group included Steve Wereley from Purdue University, Ian R. MacDonald, an oceanographer at Florida State University, John Amos, a geologists and remote sensing expert with Skytruth.org, and Timothy Crone, a marine geophysicist at Lamont-Doherty Earth Observatory, Columbia University. Contrary to BP’s claim that the spill rate was impossible to measure, this group argued that there are at least two ways to measure the rate of the spill. The first method uses computer image analysis of satellite photos and data to measure the spread and thickness of oil on the ocean surface. Remote sensing images examined by Amos and MacDonald indicated that at least 26,500 barrels of oil have been reaching the surface each day.
The second method is to measure flow rates at the site of discharge using optical image analysis. Using video released by BP, Wereley and Crone estimated 60,000 to 75,000 per day. The scientists acknowledge that because the video released was of poor quality, and information regarding the image scene is sparse, the uncertainties in these measurements are large.
Note that these estimates pertain only to the oil coming from the broken riser pipe resting on the ocean floor. There is also a second leak point on the top of the blow-out preventer. While the magnitude is unknown it will only increase the estimate of the total flow escaping.
These scientists conclude that the discharge is at least 40,000 barrels per day and could be as much as 100,000 barrels. Their assessments suggest that BP’s stated worst-case estimate of 60,000 barrels has been occurring all along.
For the first month after the spill, BP and the government repeatedly rejected estimates higher than 5,000 barrels per day, arguing that there is no way to accurately estimate the flow coming out of the pipe. Instead, they relied on measurements of oil on the sea surface made by the Coast Guard and NOAA. But on May 20, 2010, BP acknowledged that the spill rate was greater than 5,000 barrels per day because its own recovery effort was capturing that amount and more was still leaking out. BP’s admission bolstered criticism that the government had been lax in measuring the true extent of the spill and its impacts. Confusion over the spill rate was heightened on May 21, 2010 when BP backed off of its statement that it had begun siphoning up 5,000 barrels per day, saying instead that the recovery rate was about 2,000 barrels per day.
On May 20, 2010, Jane Lubchenco, head of NOAA, said that a government task force is working “around the clock” to determine the actual flow rate. On May 21, 2010, Admiral Thad Allen, the National Incident Commander for the Deepwater Horizon Response team, formally established the Flow Rate Technical Team, a multi-agency federal effort to determine oil flow rates from the BP spill. BP continued to maintain that third-party estimates did not factor in the amount of natural gas escaping from the well or the damage to the riser and drill pipes after the April 20 explosion, factors that could depress the amount of oil escaping.
BP has refused to permit scientists to send equipment to the ocean floor that would establish the leak rate with high accuracy.
BP was subject to intense pressure and criticism that it was impeding independent scientific inquiry into the leak. Rep. Edward J. Markey (Massachusetts) sent a request to BP America’s CEO Lamar McKay to release more video footage. Bowing to this pressure, BP announced on May 19, 2010 that there will be a live feed of the oil spill made publicly available on the web–an oil gusher webcam. BP said they would release the feed, which went live on May 20, 2010 at the web site of the U.S. House of Representatives’ Select Committee for Energy Independence and Global Warming. Heavy traffic caused the web site to crash.
Geographic extent of the spill
Extent of surface oil
Estimates of the extent of the surface oil slick were derived from data on wind and ocean current forecasts, as well as analysis of aerial photography and satellite imagery from a variety of sources. Using these data, New York Times produced a daily map of (1) the “observed extent” where oil was visible on the surface of the water during aerial surveys of the Gulf, and (2) the “probable extent” of the oil slick as estimated by NOAA of where oil is most likely to travel. The extents may vary widely from day to day because of changes in wind patterns and ocean currents. One month after the accident, the surface slick covered an area of about 16,000 square miles (41,424 square kilometers), an area about twice the size of the state of New Jersey.
By May 12, 2010, the Louisiana Department of Wildlife and Fisheries (LDWF) had confirmed shoreline impact at the South Pass and Whiskey Island. On May 18, 2010, Louisiana officials confirmed that surface oil had reached and penetrated the marsh ecosystems at the Head of Passes, the region where the main stem of the Mississippi River branches off into three distinct directions at its mouth in the Gulf of Mexico: Southwest Pass (west), Pass A Loutre (east) and South Pass (center). By May 20, 2010, the Louisiana Department of Environmental Quality had confirmed shoreline impact on the Chandeleur Islands, Whiskey Island, Raccoon Island, South Pass, East Fourchon/Elmers Island, Grand Isle, Trinity Island, Brush Island, and the Pass a Loutre area. Marsh Island was added on May 23. On May 20, NOAA, set the total amount of Louisiana shoreline with oil impact at 34.52 miles; by May 23 the affected coastline was more than 65 miles.
The arrival of the oil onshore was different than the iconic images from the Exxon Valdez spill where crude oil from a tanker spilled onto the surface of an enclosed body of water close to a rocky, static shoreline. Instead, the BP spill is pouring millions of gallons from the floor of the Gulf 5,000 feet below into an open sea, and 50 miles from the nearest land, which is composed of broken marshes, river deltas, open bays and barrier islands. The oil arrived in thin lines on the Louisiana coasts, and some scientists have predicted a series of “rolling skirmishes” that will last for months, if not years, even after the well is finally capped.
On May 19, NOAA concluded that some portion of the oil had reached the Loop Current in the form of “light to very light sheens.” The Loop Current is a warm ocean current in the Gulf of Mexico that flows northward between Cuba and the Yucatán peninsula, moves north into the Gulf of Mexico, loops west and south before exiting to the east through the Florida Straits. Once in the Loop Current, oil could be carried into the Florida Keys and the Atlantic Ocean.
Extent of oil in the water column
On May 12, scientists at the National Institute for Undersea Science and Technology (NIUST) discovered large oil plumes in the deep waters of the Gulf of Mexico, including one as large as 10 miles long, three miles wide and 300 feet thick in spots. The plumes were recorded at depths of 1,000–1,400 meters. Initial reports suggested that the plumes are depleting the oxygen dissolved in the water column, which could pose a threat to marine life forms at varying trophic levels.
A month after the accidents, some scientists criticized the government for failing to conduct an adequate scientific analysis of the damage and for allowing BP to obscure the spill’s true scope. They point to a 2003 study by the National Academy of Sciences, which suggested that the oil in a deepwater blowout could break into fine droplets, forming plumes of oil mixed with water that would not quickly rise to the surface. Critics charge that NOAA should have been better prepared to assess the fate and transport of oil below the surface.
Attempts to stop the leak
BP’s engineers sought to cut off the leak by activating the blowout preventer (BOP), a massive five story, 450 ton stack of shut-off valves, rams, housings, tanks and hydraulic tubing that sits on top of the well. The BOP is designed to quickly shut off the flow of oil or natural gas by squeezing, crushing or shearing pipe if there is a sudden, unexpected spike in pressure. This procedure failed. Early speculation suggested that gas hydrates formed in the BOP, causing it to malfunction. A gas hydrate is a crystalline solid consisting of gas molecules, usually methane, each surrounded by a cage of water molecules. It is similar to ice, except that the crystalline structure is stabilized by the guest gas molecule within the cage of water molecules. Gas hydrates are common when gas and water mix, and are found on the ocean floor where there are low temperatures and high pressure.
On May 7, 2010, BP maneuvered a 98-ton steel containment dome over the worst of the leaks, and planned to funnel the oil through a pipe to the surface, where it would be collected by a drill ship. This procedure failed when the dome’s opening was clogged with gas hydrates.
The first significant success at reducing the release of oil came on May 17, 2010 when robots inserted a four-inch diameter Riser Insertion Tube Tool (RITT) into the Horizon’s riser (21-inch diameter pipe) between the well and the broken end of the riser on the seafloor in 5,000 feet of water. The RITT was expected to work like a straw, sucking the leaking oil into a tanker waiting on the surface where the oil would be separated and then shipped ashore. BP initially stated that the RITT was recovering 5,000 barrels per day, but on May 21, 2010, BP reduced that estimate, stating that the device was recovering an average of about 2,200 barrels of oil a day. Additional oil continued to flow from the leaks. BP subsequently reported that from the period between May 17th to May 23rd, the daily oil rate collected by the RITT had ranged from 1,360 barrels of oil per day (b/d) to 3,000 b/d, and the daily gas rate has ranged from 4 million cubic feet per day (MMCFD) to 17 MMCFD. The oil is being stored and gas is being flared on the drillship Discoverer Enterprise, on the surface 5,000 feet above.
A longer plan is to complete so-called relief wells that will intercept the existing wellbore at approximately 16,000 feet below the sea floor. Once that is accomplished, heavy fluids and cement can be pumped downhole to kill the well. BP estimates this process will take at least 90 days. On May 2, 2010, BP began drilling the first deep-water intercept relief well, which is located one-half mile from the Macondo well, in a water depth of roughly 4,990 feet. A second relief well was begun on May 16.
BP assumed responsibility for the initial clean up and mitigation efforts. According to BP Chief Executive, Tony Hayward, “we are taking full responsibility for the spill and we will clean it up and where people can present legitimate claims for damages we will honor them.” On April 28, the U.S. military announced it was joining the cleanup operation.
The U.S. government established a “unified command” structure to coordinate the response to the spill. The stated purpose of the unified command is to link the organizations responding to the incident and to provide a forum for those organizations to make “consensus decisions.” The Deepwater Horizon Unified Command include BP, Transocean, and the following federal agencies: Minerals Management Service, NOAA, the Environmental Protection Agency (EPA), Homeland Security, the Coast Guard, the Department of the Interior, the Department of State, the Department of Defense, the Fish and Wildlife Service, the National Park Service, the U.S. Geological Survey (USGS), the Centers for Disease Control (CDC) and the Occupational Safety and Health Administration (OSHA).
As of May 21, the Unifed Command identified these resources employed to respond to the spill:
- Total response vessels: 1,150
- Total boom deployed: more than 2.4 million feet (regular plus sorbent boom)
- Oily water recovered: more than 10.2 million gallons
- Dispersant used: more than 785,000 gallons
- Overall personnel responding: more than 22,000
- 17 staging areas are in place and ready to protect sensitive shorelines, including: Dauphin Island, Ala., Orange Beach, Ala., Theodore, Ala., Panama City, Fla., Pensacola, Fla., Port St. Joe, Fla., St. Marks, Fla., Amelia, La., Cocodrie, La., Grand Isle, La., Shell Beach, La., Slidell, La., St. Mary, La.; Venice, La., Biloxi, Miss., Pascagoula, Miss., and Pass Christian, Miss.
On April 28, BP performed the first controlled burn of surface oil, also known as an in situ burn. Fire booms, U-shaped devices that are towed behind two boats and used to pull oil away from the main spill for safe burning, can be used when seas are below 3 feet and when sufficient amounts of oil can be “corralled.” Controlled burns continued to be used at the Deepwater Horizon spill site through mid-May, 2010 when conditions were right. This represents the first on-water in-situ burning at a spill since the 1989 test burn during the Exxon Valdez oil spill, which was the first time a fire-resistant boom was used at a spill. The amount of oil burned at the Deepwater Horizon spill site is unknown.
The EPA and Coast Guard approved the use of dispersants, a group of chemicals designed to be sprayed onto oil slicks to accelerate the process of natural dispersion. The dispersants used in the Deepwater Horizon clean-up are Corexit 9500 and Corexit EC9527A, also known as deodorized kerosene. The EPA has pre-approved both for emergencies that are three nautical miles (roughly five kilometers ) off the shoreline and in water depths greater than 30 feet (10 meters). In the weeks following the spill, surface dispersants were applied by aerial means by BP and various federal agencies. By May 22, 2010, 715,000 gallons of total dispersant had been deployed—630,000 on the surface and 85,000 subsea—by far the largest ever use of dispersant in a U.S. oil spill.
Corexit 9500 is known in prior scientific studies to pose a high level of toxicity to primary producer biota in the water column; in addition, it has been shown to accelerate the uptake of certain likely carcinogenic minority components present in petroleum such as napthalene. The dispersants used are approximately 10,000 times more lethal to biota than crude oil itself. Corexit 9500 and Corexit EC9527A, manufuctured by an Illinois company, both contain 2-butoxyethanol, a chemical known to cause respiratory and skin irritation effects in humans. These dispersants have been banned for use by the United Kingdom, due to known biological effects on people and natural systems.
Oil spill dispersants do not actually reduce the total amount of oil entering the environment.1 Rather, they change the inherent chemical and physical properties of oil, thereby changing the oil’s transport, fate and potential effects. Small amounts of spilled oil naturally disperse into the water column, through the action of waves and other environmental processes. The objective of dispersant use is to enhance the amount of oil that physically mixes into the water column, reducing the potential that a surface slick will contaminate shoreline habitats or come into contact with birds, marine mammals, or other organisms that exist on the water surface or shoreline. Conversely, by promoting dispersion of oil into the water column, dispersants increase the potential exposure of oil to fish and bottom dwelling biota such as clams or oysters. Dispersant application thus represents a conscious decision to increase the risk to one component of the ecosystem (e.g.,the water column) while reducing the load on another (e.g., coastal wetland). Decisions to use dispersants, therefore, involve trade-offs between decreasing the risk to water surface and shoreline habitats while increasing the potential risk to organisms in the water column and on the seafloor.
A 2005 study by the National Research Council (NRC) on the ecological effects of dispersants concluded that there is insufficient scientific data to assess the net effect of chemical dispersants on marine and coastal ecosystems. The NRC stated: “In many instances where a dispersed plume may come into contact with sensitive water-columns or benthic organisms or populations, the current understanding of key processes and mechanisms is inadequate to confidently support a decision to apply dispersants.” EPA Administrator Lisa Jackson acknowledged this point in a testimony before the U.S. Senate Committee on Environment and Public Works on May 18, 2010, when she stated “…the long term effects of dispersants on aquatic life are unknown…”
During the first weeks of May, BP applied dispersant at the sea floor during EPA-sanctioned tests. On May 7, 2010, after having deployed approximately 15,354 gallons of subsea dispersants, EPA halted subsea dispersant operations, awaiting additional test results in order to resume. Initial studies by EPA indicated that the subsurface application of approximately 10,000-15,000 gallons of dispersants have the equivalent effect on the oil as the surface application of approximately 50,000 gallons of dispersant. Thus, in principle, the subsurface application of dispersants is more efficient than surface application and could result in less dispersant being released into the environment.
On May 15, 2010, the U.S. Coast Guard and the EPA authorized BP to use dispersants undersea. Government officials stated that preliminary testing results indicate that subsea use of the dispersant is effective at reducing the amount of oil reaching the surface – and can do so with the use of less dispersant than is needed when the oil does reach the surface. Some scientists are concerned that this practice may contribute to the formation of the underwater oil plume by shaping the oil into smaller droplets. On May 17, U.S. Rep. Edward J. Markey (Massachusetts) sent a letter to EPA Administrator Lisa Jackson asking EPA to respond to concerns about the potential ecological impacts of dispersants.
On May 19, 2010, the EPA informed BP that the company had to immediately identify and use less-toxic forms of chemical dispersants, suggesting that federal officials were concerned that the unprecedented use could pose a significant threat to the Gulf of Mexico’s marine life. On May 20, 2010, the EPA began to post data from BP on the company’s monitoring and sampling programs on the EPA web site. Some of the monitoring parameters include: 1) identification of dispersed oil, 2) oil droplet size, 3) dissolved oxygen (DO) and other physical characteristics such as conductivity, temperature and depth (CTD) and, 4) toxicity information.
On May 20, 2010, BP told the EPA that it cannot find a safe, effective and available dispersant to use instead of Corexit, and will continue to use that chemical application to help break up the spill. BP told EPA that Sea-Brat 4, a proposed alternative dispersant, was rejected in part due to concern that it may degrade to a nonylphenyl, a suspected endocrine disruptor.
Some environmental scientists have criticized BP for keeping secret some of the “alternative” chemical ingredients it is using in the oil spill dispersants in its May 20 response to EPA. The EPA says BP and several of the dispersant manufacturers have claimed some sections of BP’s dispersant response contain confidential business information (CBI). EPA stated that “by law, CBI cannot be immediately made public except with the company’s permission,” and that the “EPA is currently evaluating all legal options to ensure that the remaining redacted information is released to the public.”
Construction of sand berms
Louisiana state officials proposed the construction of about 80 miles of sand berms along barrier islands and wetlands to capture oil from the spill. The proposed berms would run along the Chandeleur Islands chain, along federal and state wildlife refuges at the mouth of the Mississippi River, and would block oil from entering back bays and wetlands to the west of the river, all the way to the Isles Dernieres near the center of the state. The idea is that the oil would collect behind these walls of sand so cleanup crews could suck it up before it reaches the marshes.
The plan requires a permit from the U.S. Corps of Engineers and from the the U.S. Coast Guard which oversees the government response. If approved, the government could force BP to pay an estimated $350 million for berm construction. But federal officials and some scientists expressed concern about the plan. Some experts question whether dredging companies could build up the barrier islands quickly enough to save the marshes. There is also concern that the kind of sand berms envisioned in the plan might wash away quickly after a couple of storms, wasting scarce sand in the region. In addition, the underwater borrow pits proposed by the state could be too close to the berms, and thus could cause greater erosion to existing barrier islands or other environmental problems.
The feasibility and cost of the berm project is a point of contention between state and local officials. On May 23, 2010, Louisiana Attorney General Buddy Caldwell sent a letter to the U.S. Army Corps of Engineers advising them that the State of Louisiana was within its rights to rebuild barrier islands in order to combat the Gulf of Mexico oil spill if the Federal government did not do so first. Caldwell advised Lt. Gen. Robert L. Van Antwerp, commanding general of the Corps, that under the U.S. constitution the federal government does not have the legal authority to deny a state the right to conduct such emergency operations to protect its citizens and territory.
Paying for the clean up
The Oil Spill Liability Trust Fund (OSLTF), established in the Treasury, is available to pay the expenses of federal response to oil pollution under the Federal Water Pollution Control Act, and to compensate claims for oil removal costs and certain damages caused by oil pollution as authorized by the Oil Pollution Act of 1990 (OPA). The law requires that disbursements under the OSLTF be recovered from responsible parties liable under OPA when there is a discharge of oil to navigable waters. Aggressive collection efforts are consistent with the “polluter pays” public policy underlying the OPA. BP and Transocean have been named as responsible parties, although all claims are being processed centrally through BP.
The OPA requires that responsible parties pay the entire pricetag for cleaning up after spills from offshore drilling, including lost profits, destroyed property and lost tax revenue, but the statute caps their liability for economic damages at $75 million. In a letter addressed to Homeland Security Secretary Janet Napolitano and Interior Secretary Ken Salazar on May 16, 2010, BP Chief Tony Hayward said the company believes claims related to the spill will exceed the limit. Howard stated that “we are prepared to pay above $75 million on these claims and we will not seek reimbursement from the U.S. Government or the Oil Spill Liability Trust Fund.”
Democratic legislators tried to speed a bill through Congress that would increase the liability cap for oil spills from $75 million to $10 billion. Bill S.3305, the “Big Oil Bailout Prevention Liability Act” would have capped BP’s liability at $10 billion, even if damages from the spill surpass that amount. The bill was killed on May 13, 2010 by Sen. Lisa Murkowski (R-Alaska), a key oil industry ally.
On May 24, 2010, BP announced the cost of the response to date stood around $760 million, including the cost of the spill response, containment, relief well drilling, grants to the Gulf states, settlements and federal costs. BP stated that as of May 24, 23,000 damage claims have been filed and 9,000 have already been paid.
Transocean, the world’s largest offshore drilling contractor which owned the Deepwater Horizon, filed papers in a Houston court on May 20, 2010, seeking to limit its legal liability to $27 million.
The negative effects of oil on organisms and ecosystems is well-documented. Oil causes harm to wildlife through physical contact, ingestion, inhalation and absorption. Floating oil can contaminate plankton, which includes algae, fish eggs, and the larvae of various invertebrates. Long term damage to lower trophic levels is difficult to assess, but could pose ecological risks in the Gulf of Mexico for years, based upon interference with metabolic functions of thousands of species; benthic organisms in the inner and outer continental shelves could be affected from oil coating of substantial portions of the ocean floor. Birds can be exposed to oil as they float on the water or dive for fish through oil-slicked water. Oiled birds can lose the ability to fly and can ingest the oil while preening. Sea turtles such as loggerheads and leatherbacks can be impacted as they swim to shore for nesting activities. Turtle nest eggs may be damaged if an oiled adult lies on the nest. Scavengers such as bald eagles, gulls, raccoons, and skunks are also exposed to oil by feeding on carcasses of contaminated fish and wildlife.
Oil has the potential to persist in the environment long after a spill and have long-term impacts on fish and wildlife, interacting with the environment. Long-term effects on birds and marine mammals are less understood, but oil ingestion has been shown to cause suppression to the immune system, organ damage, behavioral changes, skin irritation and ulceration.
The area affected by the Deepwater Horizon oil spill has some of the world’s most productive marine and coastal ecosystems. Southern Louisiana contains about 40% of the nation’s coastal wetlands. These wetlands provide a range of goods and services, including flood control, water purification, storm buffer, wildlife habitat, nursery grounds for aquatic life, and recreational areas. Louisiana wetlands have been heavily degraded by human activity. In particular, marsh has been lost–converted to open water–for decades due to oil and gas development, dredging and levee construction for navigation and flood control. Louisiana has lost 1,900 square miles of land since the 1930’s. Between 1990 and 2000, wetland loss was approximately 24 square miles per year- that is the equivalent of approximately one football field lost every 38 minutes. Degradation by oil of the marsh grass, that is essential for holding sediment in place, could accelerate wetland loss.
The location of the spill site is in the ocean zone known as the Bathypelagic, a depth which has pressure as great as 160 atmospheres and temperatures of merely a few degrees Celsius. This depth is almost devoid of sunlight and hence offers virtually no primary production, but there are a variety of bioluminescent and soft muscled creatures, many of which we know little about. Due to pelagic mixing, the crude oil will migrate vertically and affect all depths of the waters of the Gulf of Mexico, including the shallower waters, which are rich in biodiversity and biological productivity.
Scientists familiar with the Gulf of Mexico cite a number of concerns about the timing of the spill:
- Breeding Season: Invertebrates, sea turtles, and birds will be facing the brunt of the spill just as they are laying eggs or caring for them in important wildlife areas.
- Trans-Gulf Migration Season: Tens of millions of birds cross the Gulf of Mexico from the Yucatan Peninsula and South America to the U. S. Gulf Coast (Texas to Florida). The spill occurred near the peak of the Trans-Gulf Migration Season.
- Hurricane Season: A big storm could complicate recovery and cleanup efforts and spread oil throughout the Gulf. The first of June is the official start of hurricane season. NOAA and others are predicting a particularly rough year for Atlantic storms.
- La Niña: Moderate El Niño conditions are expected to dissipate by June. That phenomenon, which means warmer Pacific waters, creates so-called wind shear in the Atlantic that helps break up hurricanes as they form. So without El Niño, June storms might be more likely to form. In its place, say several climate models, is a La Niña period, which means warmer temperatures in the southern areas of the United States and generally more powerful storms.
The U.S. Fish and Wildlife Service identified 32 National Wildlife Refuges at risk from the Deepwater Horizon oil spill that line the coasts of Louisiana, Mississippi, Alabama and Florida. Of particular concern are Refuges in the Southeast Louisiana (SELA) Refuges Complex, including Breton National Wildlife Refuge, the second oldest refuge in the country. The coastal wetlands in this complex support some of the nation’s most abundant wildlife, including nesting wading birds and seabirds, passerine birds (songbirds), raptors, as well as wintering shorebirds and waterfowl. For example, coastal wetlands are relied on by all 110 neo-tropical migratory songbird species— as many as 25 million can pass through the area each day during the breeding season.
The wetlands in the Refuges and other coastal regions also support a diversity of fish and shellfish species, including Speckled trout, redfish, flounder, blue crabs and shrimp. These coastal wetlands are extremely important nursery areas for both fresh and saltwater fish species. Endangered and threatened species at risk from the spill include West Indian manatees, whooping cranes, Mississippi sandhill cranes, wood storks and four species of sea turtles.
Widespread impacts on wildlife were observed beginning the week of May 16. On May 21, federal wildlife officials said they had recovered 186 sea turtles and more than 60 birds they believed may have been affected by the spill. All but a few of the sea turtles were found dead, as were 43 of the birds. They also said 18 dolphins were stranded on shore since the spill. None had oil on their skin. It was not known at the time whether these deaths were directly attributable to the spill. By way of comparison, the Exxon Valdez oil spill killed between 350,000 and 600,000 birds, along with thousands of sea otters and other marine creatures.
Some wildlife biologists believe that many more wildlife probably have been killed by the oil, but have been unaccounted for as their bodies have sunk in the open ocean, or been eaten by scavengers.
The possible impacts of crude oil and chemical dispersants in the open waters of the Gulf of Mexico are largely unknown and extremely difficult to assess. Another area of concern is the Pinnacles Region, an extensive deep (~100 m) reef tract on the Mississippi-Alabama outer continental shelf (OCS). Most of these formations are fossil reefs that are no longer actively accreting, and do not support true reef-building algae or corals. They nonetheless support a well-developed community of reef-dependent and reef-associated organisms and a relatively diverse population of fish and fauna when compared to surrounding soft sediments.
Several events leading up to the Deepwater Horizon oil spill may be germane in understanding the context of this incident. These matters include trends in deepwater drilling in the Gulf of Mexico; permit processing; and preparedness steps.
The Wall Street Journal reports that in the year 2009, deepwater drilling in the Gulf of Mexico increased over 2008 (and the average for the previous ten years) by fifty percent, or a jump of 150 million barrels per annum of crude oil. The New York Times on May 13 reported that over 300 offshore drilling permits had been issued by the U.S. government without proper approval by NOAA in the year prior to the incident. The New York Times elaborated: “Federal records indicate that these consultations ended with NOAA instructing the minerals agency that continued drilling in the gulf was harming endangered marine mammals and that the agency needed to get permits to be in compliance with federal law,”
In February 2009, BP filed a 52 page exploration and environmental impact plan for the Deepwater Horizon with the U.S. Minerals Management Service, who monitors offshore drilling for the federal government. The plan stated that it was “unlikely that an accidental surface or subsurface oil spill would occur from the proposed activities” and that “due to the distance to shore (48 miles) and the response capabilities that would be implemented, no significant adverse impacts are expected”.
Based upon BP’s simplistic assertion, the Interior Department exempted BP’s Gulf of Mexico drilling operation from a detailed environmental impact analysis in 2009. On April 6, 2009 the Minerals Management Service gave BP’s lease at Deepwater Horizon a “categorical exclusion” from the National Environmental Policy Act.
Questions about Blowout Preventers
The Deepwater Horizon blowout preventor (BOP) was not equipped with a remote control shut-off failsafe switch required in two other major oil-producing nations as last-resort protection against underwater spills. Both Norway and Brazil require such a device, which costs about $500,000. U.S. Federal regulators had exempted the Deepwater Horizon from having such a remote shut-off switch partially on the grounds of the costliness of the device (less than one percent of the Deepwater Horizon capital cost).
The failure of the BOP was foreshadowed by a 2003 paper by Deepwater Horizon owner Transocean that highlighted problems with hydraulic components of BOP control systems across the industry and suggested equipment was being rushed into the field with limited testing. Other studies had noted that a part of the BOP called a shear ram —the last line of defense that is intended to cut and close a drill pipe when all else fails — can’t always slice through the thick pipe used in deepwater drilling. A 2004 study commissioned by federal regulators found that only three of 14 newly built rigs had shears powerful enough to cut through pipe at the equipment’s maximum water depth.
In 2001, the U.S. Minerals Management Service proposed rules that would have required emergency backup control systems on BOP systems. The proposed rules were not yet law at the time of the Deepwater Horizon accident.
Questions About Cementing
An Associated Press report published on May 24, 2010 suggested that lax federal regulation oil well cementing–a suspected cause of the accident–contributed to the disaster. Federal regulators don’t regulate what type of cement is used, leaving it up to oil and gas companies, who are “urged” to simply follow guidelines of the American Petroleum Institute, an industry trade group. Far more stringent federal and state standards and controls exist on cement work for roads, bridges and buildings. Reports by the MMS named cementing as a factor in 18 of 39 well blowouts at Gulf rigs from 1992 to 2006, and five of nine out-of-control wells in the year 2000 were related to cementing problems.
Timeline of key actions
The Coast Guard responded to the explosion and fire on April 20, 2010, treating the event as a Search and Rescue (SAR) operation. The next day, on April 21, 2010, the Coast Guard continued its search for the missing eleven people.
Concurrent with the SAR, efforts began to assess the containment of the oil release. The federal government’s response to such an event as governed by the National Contingency Plan (NCP) a blueprint for responding to both oil spills and hazardous substance releases. Pursuant to the NCP, the Administration named Rear Admiral Mary Landry the Federal On-Scene Coordinator. A Regional Response Team was established, including representatives of the Coast Guard, Department of Homeland Security (DHS), Department of Commerce (DOC)/NOAA, Department of the Interior (DOI) and the EPA, as well as state and local representatives.
In the weeks following the spill, a number of government probes were announced into the Deepwater Horizon explosion and oil spill. These included probes by the Marine Board of Investigation (Coast Guard and Minerals Management Service), Interior Department Outer Continental Shelf Safety Board, National Academy of Engineering, House Energy and Commerce Committee, House Oversight and Government Reform Committee, and House Natural Resources Committee.
On April 22 a National Response Team (NRT), an organization of 16 federal departments and agencies responsible for coordinating emergency preparedness and response to oil and hazardous substance pollution events, convened its first daily meeting with leadership from across the federal government. Participants in the meeting included the White House, U.S. Coast Guard, the Department of Defense, DHS, DOC, DOI and EPA, among others.
On April 23, 2010, the Unified Area Command was formally stood up in Robert, La., after three days of informal operations and planning. The U.S. Coast Guard announced that the Deepwater Horizon rig had been found upside down approximately 1,500 feet northwest of the blowout preventer at the wellhead. At 5 p.m., the Coast Guard suspended the search for the 11 missing workers.
On April 29, Department of Homeland Security Secretary Janet Napolitano declared the event a Spill of National Significance (SONS), indicating that the government would designate more forces to contain the spill. This designation also led to the naming of U.S. Coast Guard Commandant Admiral Thad Allen as the National Incident Commander on May 1, 2010, which provided additional authority and oversight in leveraging government assets to combat the spill.
The Council on Environmental Quality and the Department of the Interior announced a review of the National Environmental Policy Act procedures for the Minerals Management Service (MMS), the bureau in DOI that manages the nation’s natural gas, oil and other mineral resources on the outer continental shelf (OCS). The review will examine the MMS NEPA procedures for OCS oil and gas exploration and development.
OnMay 17, 2010, the Small Business Administration deployed staff to Louisiana,Mississippi, Alabama and Florida to meet individually with business owners, answer questions about the Economic Injury Disaster Loan program, issue loan applications, and provide help in completing the loan forms via business outreach centers.
On May 21, 2010, President Barack Obama issued an Executive Order that created the National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling. The Commission will be chaired by former two-term Florida Governor and former Senator Bob Graham and former Administrator of the Environmental Protection Agency William K. Reilly. The seven member commission was intended to be bipartisan with “broad and diverse representation of individuals with relevant expertise.” No currently serving government employees or elected officials will sit on the commission.
The Obama Deepwater Horizon Oil Spill Legislative Package
President Barack Obama sent a legislative package to Congress on May 12 whose purpose was to “continue expeditiously, speed assistance to people affected by this spill, and strengthen and update the oil spill liability system to better address catastrophic events.” The package proposed funding for small business loans, oil spill unemployment assistance, nutrition assistance, disaster relief for fishermen and communities, and grants to state and local communities. The President’s plan would fund the U.S. Food and Drug Administration to monitor and respond to the environmental impact of the oil on seafood fished from the gulf and surrounding areas. It also increased funding to the Secretary of the Interior for additional inspections, enforcement, studies and other activities that are outside of those recoverable from the responsible parties or the Oil Spill Liability Trust Fund. The bill would extend the time allowed by statute for the Minerals Management Service to review and approve oil and gas lessee exploration plans to allow additional time for the required review. The legislation would also provide funding to the EPA and NOAA for various environmental studies that improve the federal response to the spill.
The Obama bill would raise the statutory expenditure limitation for the Oil Spill Liability Trust Fund from $1 billion to $1.5 billion and the cap on natural resource damage assessments and claims from $500 million to $750 million. The proposal would also raise the caps on liability for responsible parties, and increase the tax that oil companies pay to finance the Oil Spill Liability Trust Fund from 8 cents per barrel (per 42 gallons) to 9 cents per barrel starting this year.
Reorganization of the Minerals Management Service
In the wake of the Deepwater Horizon accident, the Minerals Management Service came under heavy criticism for alleged conflicts of interest among its competing missions. The agency was tasked with collecting royalties from oil and gas produced on federal lands and issuing energy leases; at the same time it also is responsible for policing offshore drilling and setting regulations for the industry. Indeed, in the wake of the spill President Barack Obama noted a “cozy relationship” between federal regulators at the MMS and the industry they police.
On May 19, Interior Secretary Ken Salazar announced a plan for breaking the MMS into three separate bureaus:
- The Bureau of Ocean Energy Management, which would be responsible for development of conventional and renewable energy resources on the outer continental shelf.
- The Office of Natural Resources Revenue, which would be responsible for collecting and distributing royalties from oil and gas produced on federal lands and waters.
- The Bureau of Safety and Environmental Enforcement, which would be tasked with broadly overseeing energy production and imposing safety and environmental regulations on all offshore energy activities.
Criticism of the Administration Response
A month after the accident, the Obama administration came under increasingly sharp criticism for underestimating the size of the discharge, for the lack of transparency in its response efforts, and for being too easy on BP and the oil industry. Scientists have been especially critical of the Administration for not forcing BP to fund and make publicly available more data from subsurface analysis of the leak, aerial surveillance of the ocean surface, the extent and impact of the subsurface oil plume, and the fate and impact of chemical dispersants. Scientists criticized the EPA for not releasing its finds from offshore water sampling, and they questioned why NOAA was so slow to investigate the magnitude of the spill and the damage it is causing.
The Response by Congress
The U.S. Congress reacted swiftly to the accident, holding nine hearings and three briefings on the oil spill in the first few weeks, with many more planned. A month after the accident, 10 different House and Senate committees were probing the Deepwater Horizon disaster. The hearings were part political theater, but they also produced important breakthroughs in the investigation. For example, Reps. Henry Waxman, D-Calif., and Bart Stupak, D-Mich., used their leadership roles on the House Energy and Commerce Committee to persuade BP and Transocean to turn over timelines and test data from the damaged well. Rep. Ed Markey, D-Mass., used his committee chairmanship to successfully pressure BP to release live video of the leak. Hearings in the House also helped pressure EPA to force BP to investigate alternatives to its choice of dispersants to break up the oil
The economic impacts from the spill originate in the communities affected by the spill, but then ripple throughout the entire nation. Fisherman in areas closed to fishing, or whose catch are harmed by the spill, feel the immediate effects, as do hotels, restaurants and other businesses that are tied to tourism, conventions and recreation in the Gulf Coast. The reduction in the harvest of oysters, shrimp and other seafood caused prices to rise sharply in the weeks following the spill, which in turn caused food prices to rise in restaurants as far away as New York City. The mere threat of oil caused thousands of hotel cancellations in the run-up to the usually hectic Memorial Day weekend.
Florida’s Department of Tourism tried to alleviate public concern about its beaches by posting information about Florida’s destinations on its Web site in real time with beach Webcams, Twitter feeds and photos. Gov. Charlie Crist said he had secured $25 million from BP to finance the tourism advertising campaign after an initial $25 million went to disaster preparation and response.
The oil spill clean-up also generates economic benefits. Cleanup crews and reporters covering the spill have replaced oil field workers and fishermen in some hotels and restaurants, and some fishermen could use their boats in spill clean up.
The Department of Energy announced that its national laboratories were working with the Department of Homeland Security’s National Infrastructure Simulation and Analysis Center (NISAC), which is modeling the economic costs and societal impact of the oil spill on energy and other industries in the Gulf and along the coast to support the response efforts of the National Incident Commander and the Unified Area Command. NISAC is a modeling, simulation, and analysis center within DHS that leverages national expertise to address infrastructure protection.
The Deepwater Horizon disaster is widely expected to send insurance costs higher for deepwater drilling.
1 This section is drawn directly from a National Research Council (2005) report.
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The Deepwater Horizonoil spill (also known as the Gulf of Mexico Oil Spil or the BP Oil Spill) is a large ongoing oil spill caused by an explosion on the Deepwater Horizon offshore oil platform 40 miles southeast of the Louisiana coast on April 20, 2010. Most of the 126 workers on the platform were safely evacuated, and a search and rescue operation began for 11 missing workers. The Deepwater Horizon sank in about 5,000 feet (1,500 m) of water on April 22, 2010. On April 23 the U.S. Coast Guard suspended the search for missing workers who are all presumed dead.
BP was principal developer of the Macondo Prospect oil field where the accident occurred. The Deepwater Horizon, owned by Transocean Ltd., was under a contract with BP to drill an exploratory well. BP was the lessee and principal developer of the Macondo Prospect oil field in which the rig was operating. At the time of the explosion, BP and Transocean were in the process of closing the well in anticipation of later production. Halliburton had recently completed cementing of casings in the well. The U.S. Government has named BP as the responsible party in the incident and will hold the company accountable for all cleanup costs resulting from the oil spill. BP has accepted responsibility for the oil spill and the cleanup costs but indicated that the accident was not their fault as the rig was run by Transocean personnel.
The sinking of the platform caused crude oil to gush out of the riser — the 5,000-foot pipe that connects the well at the ocean floor to the drilling platform on the surface. Attempts to shut down the flow, first estimated at about 1,000 barrels of oil a day, failed when a safety device called a blowout preventer could not be activated. On April 28, government officials said there were three leaks and the well was spilling over 5,000 barrels of oil a day — over 200,000 gallons — nearly a mile below sea level. The exact spill flow rate is uncertain and is part of an ongoing debate. Some independent estimates made in the initial days of the accident put the spill rate as in the range of 20,000 to 100,000 barrels per day. By May 22, one month after the Deepwater Horizon sank, a spill rate of 5,000 barrels per day would have released about 150,000 barrels; a spill rate of 100,000 barrels per day would have released about 3.2 million barrels.
The largest oil spill in U.S. waters is the 1989 wreck of the Exxon Valdez, which released about 250,000 barrels (10.8 million gallons) of crude oil into Prince Williams Sound in Alaska. In 2005, Hurricane Katrina caused a spill of eight million gallons of refined oil products in to the Gulf of Mexico that caused significant damage to ecosystems and wildlife. In 1979-80, the Ixtoc 1 exploratory well operated the PEMEX, the Mexican national oil corporation, experienced a blowout and ultimately released about 3.3 million barrels (140 million gallons) of crude oil into the Bay of Campeche in Mexico. Ixtoc did not cause major onshore damage.
The oil slick produced by the Deepwater Horizon oil spill has covered as much 16,000 square miles (41,424 square kilometers), an area about twice the size of the state of New Jersey, with the exact size and location of the slick fluctuating from day to day depending on weather conditions. In the weeks following the accident, scientists discovered enormous oil plumes in the deep waters of the Gulf of Mexico. The discovery suggested that that the leak from the broken undersea well could be worse than estimates that the government and BP have given.
The surface slick threatens the ecosystems and the economy of the entire Gulf Coast region, especially Louisiana, Mississippi and Alabama. The U.S. Fish and Wildlife Service reported that up to 32 National Wildlife Refuges could potentially be affected by the spill. Concerns haver also been raised about the environmental impacts of chemical known as dispersants that have been used to dissipate the oil slick. By May 21 the National Oceanic and Atmospheric Administration (NOAA) had banned fishing in almost 20% of federal waters, or 48,005 sq mi (124,333 sq km) of the Gulf.
With oil still flowing from the leak one month after the accident, it was clear that the oil industry’s impressive ability to extract oil from ever deeper offshore environments had not been accompanied by an equally effective capability to predict and respond to accidents. As drillers pushed the boundaries, regulators didn’t always mandate preparation for disaster recovery or perform independent monitoring. Documents and testimony from Congressional hearings revealed a series of potential failures and warning signs at the well site in the hours leading up to the rig explosion, as well as questions that had been raised years earlier about the reliability of deepwater technology and the ability of the industry to deal with “worse-case scenarios” of accidents.
Deepwater Horizon was an ultra-deepwater, dynamically positioned, column-stabilized, semi-submersible mobile offshore drilling unit (MODU). The rig was 396 feet (121 m) long and 256 feet (78 m) wide and could operate in waters up to 8,000 feet (2,400 m) deep, to a maximum drill depth of 30,000 feet (9,100 m). Built by Hyundai Heavy Industries in South Korea and completed in 2001, the rig was owned by Transocean Ltd. and leased to BP until September 2013. At the time of the explosion, the rig was on BP’s Mississippi Canyon Block 252, referred to as the Macondo Prospect, in the United States sector of the Gulf of Mexico, about 41 miles (66 km) off the Louisiana coast. The rig commenced drilling in February 2010 at a water depth of approximately 5,000 feet (1,500 m). The well was planned to be drilled to 18,000 feet (5,500 m), and was to be plugged and abandoned for subsequent completion as a subsea producer.
Explosion and fire
The fire aboard the Deepwater Horizon reportedly started at 9:45 p.m. CST on April 20, 2010. Survivors described the incident as a sudden explosion that gave them less than five minutes to escape as the alarm went off. Video of the fire shows billowing flames, taller than a multistory building. After burning for more than a day, Deepwater Horizon sank on April 22, 2010.
The Deepwater Horizon ablaze on April 21, 2010. Credit: U.S. Coast Guard.
The Deepwater Horizon before the disaster. Credit: Transocean.
Coast Guard vessels fighting the fire on the Deepwater Horizon. Credit: U.S. Coast Guard.
Video image of oil and gas flowing from the broken pipe on the ocean floor. Credit: National Public Radio.
Growth of the ocean area covered by the surface oil slick. Data from Skyrtuth.org.
Satellite image of the surface oil slick May 17, 2010. Credit: Center for Southeastern Tropical Advanced Remote Sensing.
A typical blowout preventer.
A controlled burn of surface oil from the Deepwater Horizon spill. Credit: U.S. Coast Guard.
Aerial application of chemical dispersant to surface oil from the Deepwater Horizon spill. Credit: U.S. Coast Guard.
Shoreline modification in Louisiana to reduce the impact of surface oil on wetlands and beaches. Credit: U.S. Coast Guard.
An oiled sea turtle rescued by wildlife biologists on the coast of Louisiana. Credit: State of Louisiana.
Pelicans in the Breton National Wildlife Refuge. Credit: U.S. Fish and Wildlife Service.
ooms protecting the coast of Louisiana from of surface oil from the Deepwater Horizon spill. The reddish material on the water is oil. Credit: State of Louisiana.
Oil soaking the hands of a rescue worker. Credit: State of Louisiana.
Shrimp harvest in coastal Louisiana Credit: State of Louisiana.
The Deepwater Horizon ablaze on April 21, 2010. Credit: U.S. Coast Guard.
The Deepwater Horizon before the disaster. Credit: Transocean.
Coast Guard vessels fighting the fire on the Deepwater Horizon. Credit: U.S. Coast Guard.