The containment, dispersal, and removal of oil in the Gulf of Mexico following the 2010 Deepwater Horizon oil spill employed a variety of techniques executed by private, volunteer, and governmental organisations. While most of the oil drilled off Louisiana is a lighter crude, the leaking oil was of a heavier blend which contained asphalt-like substances. According to Ed Overton, who heads a federal chemical hazard assessment team for oil spills, this type of oil emulsifies well. Once it becomes emulsified, it no longer evaporates as quickly as regular oil, does not rinse off as easily, cannot be broken down by microbes as easily, and does not burn as well. "That type of mixture essentially removes all the best oil clean-up weapons", Overton said.
On 6 May 2010, BP began documenting the daily response efforts on its web site. On 28 April, the US military joined the cleanup operation. The response increased in scale as the spill volume grew. Initially, BP employed remotely operated underwater vehicles (ROV's), 700 workers, 4 airplanes, and 32 vessels. By 29 April 69 vessels, including skimmers, tugs, barges, and recovery vessels, were in use. By 4 May 2010, the United States Coast Guard (USCG) estimated that 170 vessels, and nearly 7,500 personnel were participating, with an additional 2,000 volunteers assisting. These volunteers help build relief walls, burn the oil, clean the water and other affected bodies of water such as marshes, beaches, and shorelines, clean contaminated equipment and vessels, and were involved in both land and water response outreach.
In summer 2010, approximately 47,000 people and 7,000 vessels were involved in the response works. By 3 October 2012, federal response costs amounted $850 million, most of them reimbursed by BP. As of January 2013, 935 response personnel were still involved in response activities in the region. For that time BP's costs for cleanup operations exceeded $14 billion. The oil drill was finally sealed on 15 July 2010.
Containment
The response included deploying many miles of containment boom, whose purpose is to either corral the oil, or to block it from a marsh, mangrove, shrimp, crab, and/or oyster ranch, or other ecologically sensitive areas. Booms extend above and below the water surface and are effective only in relatively calm and slow-moving waters. More than of containment booms were initially deployed to protect the coast and the Mississippi River Delta. By the next day, that nearly doubled to , with an additional staged or being deployed. In total, during the crisis one-time use sorbent booms and of containment booms were deployed.
Some lawmakers have questioned the effectiveness of the booms, claiming that there was not enough boom to protect the shoreline and that the boom was not always installed correctly. Billy Nungesser, president of Plaquemines Parish, Louisiana, said the boom "washes up on the shore with the oil, and then we have oil in the marsh, and we have an oily boom. So we have two problems". According to Naomi Klein, writing for The Guardian, "the ocean's winds and currents have made a mockery of the lightweight booms BP has laid out to absorb the oil." Byron Encalade, president of the Louisiana Oysters Association, told BP that the "oil's gonna go over the booms or underneath the bottom", and according to Klein, he was right. Rick Steiner, a marine biologist who closely followed the clean-up operations, estimated that "70% or 80% of the booms are doing absolutely nothing at all". Local officials along the gulf maintained that there was a scarcity of boom, especially the heavier "ocean boom". BP, in its regional plan, says that boom is not effective in waters with waves more than three to four feet high; waves in the gulf often exceed that height. One report commented that the response to this disaster was mainly focused on surface level clean-up instead of deep sea clean-up, prolonging the response time. And as we can see from the controversy over the booms, not all response efforts were effective.
Louisiana barrier island plan The Louisiana barrier island plan is a project initiated by Louisiana to construct barrier islands in the Gulf of Mexico protecting the coast of Louisiana from contamination by crude oil escaping from the Deepwater Horizon oil spill. On 27 May 2010, acting on an application by the Louisiana Coastal Protection and Restoration Authority, the United States Army Corps of Engineers offered an emergency permit to the state to commence work.Corps decision on state's emergency permit request Posted on Thursday, 27 May 2010 by the New Orleans District of the Army Corps of Engineers, accessed 19 July 2010
The berms are 325 feet wide at the base and 25 feet wide at their summits, rising 6 feet above mean high water level.Page 13 Document prepared by the Army Corps of Engineers detailing the emergency permit issued May 27, 2010, accessed 19 July 2010 If fully built, the system would have been 128 miles long. In May 2010 the federal government issued permits to construct 45 miles. BP agreed to pay the estimated $360 million initial cost."Louisiana constructing islands in the gulf to aid in oil cleanup" article by David A. Fahrenthold in The Washington Post 19 July 2010, accessed 19 July 2010
Critics of the project maintained that it would be expensive and ineffective: involving use of over 100 million yards of dredged material, costing $360 million, and taking 6 months to build. Issues include the length of time necessary to construct miles of berm and the anticipated effects of both normal and storm erosion on the structures."Slosh and Berm: Building Sand Barriers off Louisiana's Coast to Hold Back Oil Spill Has Low Probability of Success" David Biello in Scientific American 8 June 2010, accessed 19 July 2010 It is alleged by critics that the decision to pursue the project was made on a political basis with little input from the scientific experts."Sand berms partially political" article by Amy Wold in The Advocate (Louisiana) 11 July 2010, accessed 19 July 2010
After the BP well was capped on 15 July 2010, construction of the berms continued and was still underway in October 2010. The $360 million project was being financed by BP and being built under the supervision of the Army Corps of Engineers. If completed, and no further funding obtained, following modification of the project by the state, there would be a total of 22 miles of berm. As of October 2010 opposition to the project was growing and Thomas L. Strickland, assistant interior secretary for fish and wildlife and parks had called for re-evaluation of the project."Louisiana Builds Barriers Even as Oil Disperses" article by John Collins Rudolf in The New York Times 21 October 2010, accessed 22 October, 3010
On 1 November 2010, it was announced by Louisiana Governor Bobby Jindal and BP that a revised agreement between them provided that $100 million of the remaining $140 million would be used to convert completed berms into artificial barrier islands by widening them and adding vegetation and the remaining funds used to finish up ongoing berm work. A total of 17 million cubic yards of sand had been dredged by November 2010, 12 million from the Mississippi River; 8.5 million cubic yards had been used to build the berms, the remainder being stockpiled.
The presidential commission concluded in December 2010 that the $220 million sand berms captured a "minuscule amount" of oil () and proved "underwhelmingly effective" as well as "overwhelmingly expensive". Of the $360 million BP gave for the berms, Louisiana plans to spend $140 million to turn the 36 miles of berms into barrier islands.
Dispersal
The spill was also notable for the volume of Corexit oil dispersant used, as well as the methods of application which that time were "purely experimental". Although usage of dispersants was described as "most effective and fast moving tool for minimizing shoreline impact", this use of dispersant was questioned at the time and its effects continue to be questioned and investigated. Altogether, of dispersants were used; of this were used subsea at the wellhead.
Choice and composition of Corexit
Corexit EC9500A and Corexit EC9527A were the principal dispersants employed. The two formulations are neither the least toxic, nor the most effective, among the EPA's approved dispersants. Twelve other products received better toxicity and effectiveness ratings, but BP says it chose to use Corexit because it was available the week of the rig explosion. Critics contend that the major oil companies stockpile Corexit because of their close business relationship with its manufacturer Nalco.
Environmental groups attempted to obtain information regarding the composition and safety of ingredients in Corexit through the Freedom of Information Act but were denied by the EPA. After Earthjustice sued on behalf of the Gulf Restoration Network and the Florida Wildlife Federation, the EPA released a list of all 57 chemicals in the 14 dispersents on the EPA's National Contingency Plan Product Schedule. The dispersants used contain propylene glycol, 2-butoxyethanol, and dioctyl sodium sulfosuccinate.
Earthjustice and Toxipedia conducted the first analysis of the 57 chemicals found in Corexit formulas 9500 and 9527 in 2011. Results showed the dispersant could contain cancer-causing agents, hazardous toxins and endocrine-disrupting chemicals.Pensacola News Journal: Archives The analysis found "5 chemicals are associated with cancer; 33 are associated with skin irritation from rashes to burns; 33 are linked to eye irritation; 11 are suspected of being potential respiratory toxins or irritants; 10 are suspected kidney toxins; 8 are suspected or known to be toxic to aquatic organisms; and 5 are suspected to have a moderate acute toxicity to fish".
Method and extent of use
Over 400 sorties were employed to spray dispersants over the spill. In early May 2010, four military C-130 Hercules aircraft, normally used to spray pesticides or fire retardant, were deployed to the Gulf of Mexico to spray dispersants. More than half of the of chemical dispersants were applied at the wellhead under the sea. This had never previously been tried but due to the unprecedented nature of this spill, BP along with the USCG and the EPA, decided to use "the first subsea injection of dispersant directly into oil at the source".
Dispersants are said to facilitate the digestion of the oil by microbes. Mixing the dispersants with the oil at the wellhead would keep some oil below the surface and in theory, allow microbes to digest the oil before it reached the surface. Various risks were identified and evaluated, in particular that an increase in the microbe activity might reduce the oxygen in the water. The use of dispersants at the wellhead was pursued and NOAA estimated that roughly of oil were dispersed underwater.
By 12 July 2010, BP had reported applying of Corexit on the surface and underwater (subsea). By 30 July 2010, more than of dispersant had been used, mostly Corexit 9500.
Dispersant use was said to have stopped after the cap was in place. Marine toxicologist Riki Ott wrote an open letter to the EPA in late August with evidence that dispersant use had not stopped and that it was being administered near shore. Independent testing supported her claim. New Orleans-based attorney Stuart Smith, representing the Louisiana-based United Commercial Fisherman's Association and the Louisiana Environmental Action Network said he "personally saw C-130s applying dispersants from [his] hotel room in the Florida Panhandle. They were spraying directly adjacent to the beach right at dusk. Fishermen I've talked to say they've been sprayed. This idea they are not using this stuff near the coast is nonsense."
Environmental controversy over Corexit