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9.2.7 Historical Spills that Used or Informed NEBA Processes

The literature contains many examples of accidental and intentional research related spills in non-Arctic areas that have produced information that is relative to NEBA assessments.  Spills conducted for research purposes have allowed for observation of response strategy impacts and long term recovery rates in controlled environments.  In some instances, NEBA has been used to guide response actions during actual spills, and its benefits have been well documented.  Examples are provided below. A. Experimental: Baffin Island tests in northern Canada

The Baffin Island Oil Spill (BIOS) field-based experiment examined the acute and long-term effects of crude oil and dispersed oil released to separate embayments of Baffin Island in 1980.   The untreated oil dispersion simulated an oil slick moving onshore from a blowout situation (producing oil at 1000 m3/d or approximately 15 m3); chemically dispersed oil concentrations were based on typical oil concentrations beneath dispersed oil slicks (averaging 10 µg/g after dispersant application).  Faunal groups assessed included infauna, epibenthos, macroalgae, and under-ice meiofauna in the vicinity of nearshore, landfast ice; endpoints included mortality, growth and community metrics (e.g. species abundance and diversity).  An additional bay was observed for the same endpoints to serve as a reference site.  Inter-annual patterns were established for the reference bay and the authors concluded that only minimal effects could be attributed to oil.  Some short-term behavioral patterns and a reduction in urchin densities (due to emigration) was observed as a consequence of dispersed oil exposure; oil had a possible minor effect on the reproductive viability of Spio sp. of polychaetes.  No adverse effects to biomass, number of species and reproductive condition of macroalgae were noted.  Observations of the under-ice communities noted some evidence of a stimulatory effect of oil on harpacticoid adults and copepodites, and on cyclopoid nauplii, whereas a dispersed oil exposure maintained for 5 h indicated that harpacticoid adult copepods showed greater immediate response than did copepodites.  The community structure at the reference site was composed of: copepods = 92.3%; nematodes= 4.0%; and polychaetes = 3.2%.  Natural weathering of the oil was observed periodically for twenty years.  By 1989, there was approximately an 80% reduction in oiled area; further reductions occurred by 2001 and lingering oil was less than 5%.  Much of that reduction was attributed to photo-oxidation and biodegradation (Cross WE 1987, Cross and Thomson 1987, Cross et al. 1987a, Cross et al. 1987b). B. Experimental: TROPICS study

The Tropical Investigations in Coastal Systems (TROPICS) study began in 1983/84 near Bocas del Toro, Panama.  The study involved dosing of two sites, containing intertidal mangroves and subtidal seagrass-coral zones, with both dispersed and non-dispersed oil.  The treated areas were monitored periodically for 25 years.  The study found that plots treated with dispersed oil recovered to near reference level conditions within 10 years, whereas sites treated with undispersed oil exhibited long term disruption after 25 years (DeMicco et al. 2011).  The results provided useful scientific data that can support future NEBA projects in tropical, nearshore environments. C. Tanker: Braer Spill

In 1993, during heavy weather conditions (Beaufort force 10 and 11 winds, 55 – 74mph), the tanker Braer ran aground in the Shetland Islands, and released 84,700 tons of crude oil.  During the early and late stages of the spill response, chemical dispersants were applied from DC-3 aircraft but the winds were prohibitively strong during most of the response.  All of the oil eventually dispersed but it was estimated that chemical dispersion accounted for only 2 – 3% of the total spill volume, with natural dispersion accounting for the rest due to the high sea state and the specific oil type (Gullfaks crude).  A comprehensive and prolonged monitoring program following the incident found that dispersed oil concentrations were high (50 ppm) in the vicinity of the wreck, and persisted for several days.  Ten days after the incident, dispersed oil concentrations were 5 ppm.  Background levels were found after 60 – 70 days.  Fisheries were very important to the local economy, and while some impacts did occur, they were localized, and far less than expected.  The incident provided a comparison of the relative expected toxicity of dispersed vs. non-dispersed oil. D. Tanker: Sea Empress spill

The Sea Empress ran aground in 1996 in the entrance to Milford Haven, in Pembrokeshire, U.K., spilling 72,000 tons of light crude oil and 480 tons of heavy fuel oil.  The response action included spraying 446 tons of dispersant from 6 DC-3 aircraft.  Approximately one half to two thirds of the 37,000 tons of oil that was estimated to have dispersed was attributed to the addition of chemical dispersants.  While environmental impacts were significant, they were less than was expected based on the size of the spill.  Tradeoffs of environmental impacts associated with the use of chemical dispersants were identified and taken into account for the nearshore use of dispersants.  As a result, the overall environmental impact of the spill was thought to have been reduced. E. Well Blowout: Montara spill (also known as the West Atlas Spill)

The Montara oil spill (2009) resulted from a well blowout located approximately 180 km west of Australia, in the Timor Sea.  Estimates of the spill release rate ranged from 400 to 2000 bbl per day, and the spill lasted a total of 74 days.  Based on computer simulation, using the OILMAP model, it was shown that the spill had the potential to impact sensitive areas such as Ashmore Reef, Cartier Island, and Western Australian wetlands.  A NEBA was conducted to evaluate the potential impact of response strategies including mechanical recovery and use of chemical dispersants.  The NEBA considered the demonstrated benefits of use of chemical dispersants as a first response option for the Sea Empress Spill.  The results of the NEBA concluded that the potential for surface oil impacts would be significantly reduced by the use of chemical dispersants.  Consequently, provisions for spraying dispersants from a vessel onto fresh oil (less than two days old) were incorporated into the Incident Action Plan (IAP).  The NEBA further recommended use of mechanical recovery and natural recovery for certain situations where dispersant use would not result in a net environmental benefit.