An Ecosystem Services Approach to Assessing the Impacts of the Deepwater Horizon Oil Spill in the Gulf of Mexico (2013) / Chapter Skim
Currently Skimming:
4 Oil Spill Response Technologies
4 Oil Spill Response Technologies
Pages 71-102
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From page 71... ...
, stormy weather, or lack of equipment and manpower, natural attenuation might be the only option available. This chapter reviews the suite of spill response technologies used during the DWH oil spill event, discusses how they were applied in response to the spill, presents the effectiveness and risks associated with their use, and, where possible, assesses their potential impacts on the GoM ecosystem and its services.
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From page 72... ...
section deals with natural attenuation -- the natural bitmapped, uneditable Understanding of the efficacy of response technologies used during the DWH oil spill is rapidly evolving, and papers and reports continue to be published. The results presented in this 72
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From page 73... ...
have estimated that the use of dispersants helped to keep 500,000 barrels of the DWH oil away from the highly productive and sensitive coastal areas, but there is no feasible way to verify this estimate. When an oil slick is sprayed with dispersant and exposed to mixing energy, typically from wave action, some of the oil is broken up into small droplets, which may then become entrained in the water column (Li et al., 2008, 2009a,b; Lunel, 1995)
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From page 74... ...
to (the) product." The report further stated that "ingredients are not considered to cause chemical sensitization; the dispersants contain proven, biodegradable and low toxicity surfactants." The use of chemical dispersants at the DWH oil spill site was regulated under the Clean Water Act.
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From page 75... ...
4-3 Dispersant Application Methods R02473 bitmapped, uneditable Chemical dispersants are most often sprayed directly onto a surface oil slick from an airplane or ship. During the DWH oil spill response, chemical oil dispersants were also injected directly into the stream of oil and gas flowing from the damaged wellhead located 1,522 m below the surface of the ocean.
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From page 76... ...
The algorithm gives a reasonable fit to their laboratory studies as well as several other relevant studies. This algorithm suggests that dispersant application in the DWH oil spill dramatically reduced the droplet size.
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From page 77... ...
. Corexit concentrations of 1 to 10 milligrams per milliliter, which were likely encountered during the actual dispersant application, promoted the biodegradation of DWH oil in laboratory tests, but also caused significant reductions in production and viability of the hydrocarbon degraders, Acinetobacter and Marinobacter (Hamdan and Fulmer, 2011)
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From page 78... ...
Toxicity and Bioaccumulation of Dispersed Oil, Dispersants, and Surfactants Although a great deal of work has been done under controlled laboratory conditions to evaluate the toxicity of chemical oil dispersants and dispersed oil in the marine environment, differences in results have been observed because of factors such as species-specific sensitivity, the particular dispersant formulation used, and experimental conditions (George-Ares and Clark, 2000)
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From page 79... ...
. Microcosm experiments performed in situ in North Inlet Estuary near Georgetown, South Carolina, using DWH oil and a Texas crude oil noted a decrease in chlorophyll a in phytoplankton as crude oil concentration increased from 10 to 100 microliters per liter (Gilde and Pinckney, 2012)
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From page 80... ...
Dispersant application during the DWH oil spill occurred at a time when birds in the Gulf region were nesting. Some birds and their eggs may have been exposed to oil, Corexit, or dispersed oil.
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After the DWH oil spill, the EPA issued a number of directives (EPA, 2010) regarding the monitoring of the efficacy of subsurface oil dispersant injection and the fate and transport of dispersed oil and operational shutdown criteria.
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From page 82... ...
These facts may be weighed when considering the net environmental benefit to having used disper sants to respond to the DWH oil spill. Dispersant Degradation During the DWH Oil Spill The Operational Science Advisory Team (OSAT, 2010)
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BOX 4.1 Fate of Chemically Dispersed Oil from the Ixtoc I Oil Spill The Ixtoc I well blowout in the Bay of Campeche in the southern GoM off Mexico in 1979-1980 in 50-m water depth expelled about 150 million gallons of oil (more than half of that attributed to the DWH oil spill) , yet 5 years later there appeared to be little evidence of residual toxicologi cal impacts (Aldhous and McKenna, 2010)
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From page 84... ...
Although the media expressed fears that the oxygen depletion within the water column in the vicinity of the Macondo wellhead might cause hypoxic conditions or anoxic "dead zones" and threaten marine organisms, the maximum depletion observed was 40 percent, whereas 60 percent is considered detrimental to fish (Walsh, 2011)
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From page 85... ...
. Summary of Dispersant Use During the DWH Oil Spill Response About 1.8 million gallons of dispersant were used during the DWH oil spill response, of which about 42 percent was injected at the wellhead (Federal Interagency Solutions Group, 2010)
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From page 86... ...
The short- and long-term impacts of dispersants and dispersed oil from the DWH oil spill on the food web and other GoM ecosystem services are still undetermined (see Chapter 5 for discussion of specific examples)
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From page 87... ...
Fire-resistant booms are the obvious choice to contain the oil. In Situ Burning During the DWH Oil Spill ISB was selected as a response technology during the DWH event because of the need to supplement skimming operations to capture more oil, the fact that the oil slick was initially far from populated areas, and the understanding that controlled ISB could be conducted safely and effectively to eliminate large volumes of oil with minimal environmental impact (Allen et al., 2011)
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From page 88... ...
within 5 to 24 km from the wellhead, and therefore, that oil did not impact shallow waters, shorelines, and sensitive coastal resources. In comparison to other technologies, according to the oil budget calculator (Figure 4.1)
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From page 89... ...
Several technical innovations led to in situ burning being the most successful re sponse method in terms of removing oil from the sea surface offshore (estimated to be as high as 300,000 barrels or 6 percent of the total volume of oil spilled) and thus keeping oil away from sensitive coastal habitats.
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From page 90... ...
However, given the diluted and dispersed nature of the DWH oil spill, skimmers were only able to capture between 75,000 to 300,000 barrels of oil. Nonetheless, skimming prevented this oil from reaching sensitive coastal ecosystems and impacting the services they provide.
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. The extent of impacts from the berm operations conducted during the DWH oil spill is unknown.
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A sorbent boom is typically anchored parallel to the shoreline to absorb oil slicks as they wash toward the shore. Use of Booms During the DWH Oil Spill During the DWH oil spill, booms were extensively used to protect sensitive coastal marshes and were later removed.
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From page 93... ...
Hydrology Modification via Mississippi River Diversions The Davis Pond Freshwater Diversion was built in 2004 to reduce salinity throughout the length of Barataria Bay, enhance fisheries, and add additional nutrients and sediment to the area wetlands.8 The diversion was opened by the state of Louisiana on April 30, 2010, during the DWH oil spill to prevent oil from contaminating the marshes of Barataria Bay (Bianchi et al., 2011)
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From page 94... ...
TREATMENT OF SHORELINE OILED BY THE DWH OIL SPILL Technological efforts offshore do not entirely contain the oil. Oil at sea very often will impact coastal shores if sensitive shorelines are not far away, and if ocean currents are likely to move oil slicks or dispersed oil to those areas.
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, and jetties were treated after the DWH oil spill through manual removal of bulk oil, followed by washing using a range of temperatures and pressures (Santner et al., 2011)
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From page 96... ...
Although one small-scale demonstration in Escambia, Florida, led to an initial decision against surf washing because of strong longshore currents, sediment drift, and little residual oil (Owens et al., 2011) , operations were resumed at a later date to treat residual oil in the beach sediments.
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. In the case of the DWH oil spill, it has been suggested that oiled Gulf Coast marshes will recover by natural attenuation because prior research has demonstrated their intrinsic resilience (DeLaune and Wright, 2011)
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From page 98... ...
, and 4,000 birds are thought to have died as a consequence of the DWH oil spill (Service, 2010)
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From page 99... ...
Enhanced OMA production by surf-washing operations has now been recognized as a strategy to remove oil stranded within beach sediments (Lee et al., 1997, 1999; Lunel et al., 1996, 1997; Owens, 1999; Owens and Lee, 2003; Swannell et al., 1999; see section, "Treatment of Shoreline Oiled by the DWH Oil Spill," subsection "Surf Washing")
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From page 100... ...
and the associated wave surge, to which additional cleanup activities were applied, the fate of this residual oil was left to natural attenuation. The DWH oil spill highlighted the significance of natural oil degradation.
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From page 101... ...
. SUMMARY A number of spill response technologies and techniques were applied during the DWH oil spill, including direct recovery from the wellhead, skimming, in situ burning, chemical dispersion, flushing (river diversion)
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From page 102... ...
Most decisions regarding the application of spill response technologies after the DWH oil spill were based on NEBA,11 and they were made in consideration of the best available information at the time. The immediate goal of the response technologies applied during the DWH oil spill was to prevent oil from reaching sensitive coastal habitats.
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