grande policecontraste

Response at sea

imprimer
SpillsDeepwater HorizonArchives > Response at sea

The main strategy deployed by the Americans for this pollution was to prevent the oil from reaching the coast, particularly at sensitive areas in Louisiana.

To do so, in addition to oil recovery at sea, two other techniques were used: the classic method of dispersion and the far less common method, particularly upon such as large scale, of burning.

Recovery

The deployment of a gigantic armada was one of the many examples of exorbitance illustrated by the response to this spill. By the end of July, over 4,000 ships and 540 barges had been mobilised, including a barge used to deploy over 750 skimmers of all types.


Number of vessels onsite
(Source: Deepwater Horizon Response)
(click to enlarge)


At the beginning of July, the 335 metre-long supertanker A Whale, altered at the expense of the Taiwanese owner, conducting recovery trials at sea. The tanker is able to pump off a mixture of oil and water, then separate off the water, transferring the oil onto another vessel and discharging the water into the sea. After a series of non-conclusive tests, BP did not contract this vessel for its response efforts.



Quantity of oil-water mix recovered
(Source: Deepwater Horizon Response)
(click to enlarge)


By the end of July, the Americans declared that they had recovered 13, 000 m3 of water and oil emulsion, containing unknown quantities of water.

Recovery operation at sea by trawling (Source: Transport Canada)
Recovery operation at sea by trawling © Transport Canada

Dispersion

Such an immense quantity of dispersant has never before been used. It is also worth noting that, in the modern history of spills, such favourable conditions have never been encountered: a continuous flow of crude oil in very deep waters, promoting wide dissemination of the dispersed oil.

The treatment is applied here mainly by plane, near where the oil rises to the surface. In early July, the volume of dispersant spread at the surface exceeded 4,000 m3.

To make the most of this deep water column (1,500 m) and disperse oil where it rises to the surface, the Americans innovated by injecting over 3,000 m3 of dispersant into the wellhead. Meanwhile, a major system designed to measure the oil concentration in the water mass was set up to assess the effects of this technique in the environment.



Quantity of dispersants (in m3)
(Source: Deepwater Horizon Response)
(click to enlarge)

Burning

On 28 April, in situ burning trials using fire booms were conducted. Due to strong prevailing winds, attempts had to be called off for several days.

On 5 and 6 May and also on 17, 18 and 19 May, favourable weather conditions allowed responders to conduct successful controlled burning operations.

Following static, temporary burning operations conducted at the beginning of operations, a dynamic burning technique was implemented, consisting of gradually concentrating the oil to continue to fuel the fire using a fire boom towed by two vessels working together. The operation was conducted by trained fishermen but the technique remained dangerous.

At the end of July, 411 controlled burning operations enabled 42,000 m3 of oil to be dispersed into the atmosphere. Observations showed that the combustion residues sank rapidly.


Last update: 4/08/10

Emergency hotline: +332 98 33 10 10 - 24h/24
© www.cedre.fr