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APPENDIX B Case Studies Although experience gained in treating large marine of} spins from tanker accidents should give additional insight into the fac- tors governing dispersant effectiveness, the few documented cases are disappointing. Field studies of accidental major of! spills where dispersants were used generally- provide incomplete or equivocal in- formation because less than half of the spilled of! was sprayed and the studies usually did not distinguish between exposure to dispersed of] and undispersed oil. Nevertheless, at least two studies following ma- jor spills focused on waters where of} was dispersed: the Main Pass Block 41 Platform C and Stop ~ spills in the Gulf of Mexico. Other spins that were studied, including the Amoco Cacliz (Spooner, 1978), the UrquioZa (Gundiach et al., 1978), and the Florida (Sanders et al., 198~), offer little useful data with which to evaluate the ecological effects of dispersant use. Only a brief review of relevant facts are included here. TOURED CANYON, 1967 The effects of the massive use of dispersants to clean up the large of} spin resulting from the Torrey Canyon accident were studied by Smith (1968) and Southward and Southward (1978), among others. 317
318 APPENDIX B Ten thousand tons* (about 75,000 bbl) of first-generation toxic dis- persants were applied to 14,000 tons (about 105,000 bbl) crude of} stranded on rocky coastline in Cornwall, England. The of} alone was not very toxic, although some mortality of limpets and barnacles occurred. Use of dispersants, however, caused extensive mortalities of animals and algae, proportional to dispersant dose. The widely reported "rapid" recovery of shorelines following the spin was largely not true: recolonization of affected areas followed a natural suc- cession pattern, but at a slower rate. Recovery was slowest where exposure to of! and dispersant was highest and 10 years later was still not complete in some areas. Herbivores were affected more than plants, and some community structures were altered. The major problem may not have been the dispersants them- selves, but the way in which they were used. Clearly, their major purpose was aesthetic, not ecological. The objective was to remove visible oil from shorelines, without regard for ecological consequences. The results from the Torrey Canyon spill are a major reason for concern about the toxicity of dispersants. The surfact~nts were in aromatic hydrocarbon solvents, which are fairly effective in dispers- ing oil, but are highly toxic to marine and shore organisms when sprayed in high concentrations directly on beaches. Biological sur- veys showed that heavy excessive mortalities resulted where these early formulations were used in large quantities. In fact, of] con- tamination alone resulted in fewer adverse biological effects on shore areas than where the dispersants were used. MAIN PASS BLOCK 41, PLATFORM C, 1972 Gulf of Mexico, Main Pass Block 41, Platform C, located about 11 mi east of the Mississippi River Delta in 39 ft of water, discharged about 65,000 bb} of crude of! over 3 weeks in March 1970. During that time, about 2,000 bbI of two chemical dispersants were sprayed in diluted form by fire monitors from a barge. The dilute dispersant was applied to the platform and immediate surrounding waters to keep the steed structure water-wet, both for safety of personnel working on the platform and to keep the structure from melting if the of} and gas reignited. No attempt was purposely made to treat all of the slick with spray boats or aircraft. *Maritime spills are reported in long tons (2,240 lb = 7.5 bbl of oilj
APPENDIX B 319 It was estimated that 25 to 30 percent of the oil evaporated in the first 24 hr. 10 to 20 percent was recovered from the water surface, less than 1 percent dissolved, and less than 1 percent was identified in sediments within a 5-ml radius of the platform. Some of} was emulsified, observed as a "widening creamy-yeBow near-surface plume as it moved with the water from the platform," which became too diffused to observe from about ~ my away (McAuliffe et al., 1975~. Over 3 days when the of! was estimated to be spilling at a rate of 1,500 bbl/day, water samples were collected near the platform and from the dispersed of! plume until it could no longer be seen (McAuTiffe et al., 1975~. The highest of} concentration in a sample of the plume closest to the platform was 60 mg/liter. One mile away, of! concentration decreased to 1 mg/liter. Estimates of of} dispersed ranged between 4 and 66 percent. Neither the untreated of! nor the dispersed of} appear to have had adverse effects on marine life (spilled of} did not strand). Over 550 species of benthic organisms were identified in 233 samples from that region. The numbers of species and individuals organisms showed lower values in some samples near the platform. However, seasonal variations, bottom sediment type, and other environmental param- eters, including Mississippi River discharges, made it impossible to determine whether these locations had been affected by the spilled oil. There was no correlation between number of species, number of individuals, or other biological parameters and the hydrocarbon content of the sediments for samples within a 10-m radius of the platform. This lack of correlation suggests lack of significant effect of oil on benthic organisms, which would have been most likely to be affected. Extensive trawl samples showed no alteration in the annual life cycle of commercially important shrimp, blue crabs were observed throughout the area, and the number of fish species was comparable to a prior survey. El;EN! V, 1978 The Eleni V carried a heavy fuel of] with viscosity 5,000 cSt at 20° C. Colliding with the Roseline off the southeast coast of England in 197S, she released 7,500 tons (56,000 bill) of oil. A total of 900 tons (6,800 bbl) of dispersant concentrate BPllOOD and 10 percent Basic I`TD were applied by 22 vessels over 3 weeks, but because of
320 APPENDIX B high viscosity they were ineffective, and virtually all the of] washed ashore (Nichols and Parker, 1985~. HASBAH 6, 1978 The Hasbah 6 wed blowout off northern Saudi Arabia released 14,000 tons (105,000 bbl) of heavy crude oil, which was treated with dispersant by boat and helicopter. Calm seas, the high viscosity of weathered crude making up the slick, and inadequate preparation for such a large spin diminished the effectiveness of the effort (Kornberg et al., 1931; Oil Spill Intelligence Report, 1980~. IXTOC I, 1979-1980 The [bloc Iwell blowout occurred in the southern Gulf of Mexico in June 1979, spilling an estimated 30,000 bbl/day between June and December. Over these 6 months, spray booms 25-ft long on each aircraft wing, with 228 nozzle bodies, pumped 400 gal/min per pump. Some aircraft were equipped with two such systems, thus doubling the maximum rate available (Lindblom et al., 1981~. Observers saw results within several hours, and by the following day no of! was visible in the treated area. This included oil that had drifted 500 mi and had been on the water for 4 to 6 months before spraying (l~indblom et al., 1981~. Dispersal of oil at 4 to 6 months was visually confirmed by the air crews on return trips (I.indblom et al., 1981~. Slicks on very calm water to which dispersants were applied were usually dispersed by overnight storms. A small amount of of] was stranded north of Tampico, Mexico while aerial operations were con- fined to the southern Gulf. After redeployment of aircraft along the shoreline to the U.S. border, no oil came ashore in Mexico until hurri- cane Henri arrived in late September and grounded the airplanes. At that time oil stranded on the western Yucatan shoreline, but lagoons were protected from oiling by the rapid outflow of fresh water from heavy rains (I.indblom et al., 1981~. Field evaluation by the Gulf Universities Research Consortium (Lipton and Koons, 1983) indicated that dispersant "effectively dis- persed the [xtoc ~ crude from the surface into the upper 3 m of the water column." Limited biological studies during and following the spin did not reveal adverse effects. For example, shrimp landings in subsequent years were unchanged or greater than previous yearly catch statistics.
APPENDIX B 321 BETELGUESE, 1979 The 1979 spill of 7,000 bb] of mixed Arabian crude from the tanker Beteigeuse in Bantry Bay, southwest {relend was probably the first significant of! spill in Europe for which dispersants were applied from aircraft in preference to vessels (Nichols and White, 1979~. Thirty-five metric tons (260 bbl) of BPl1OOWD was believed to have protected shorelines successfully with an application rate of 2 to 3 gal/acre (19 to 28 liter/ha) (Nichols and Parker, 1985; Nichols and White, 1979~. On the other hand, winds up to Beaufort force 4 were present and much of the effective dispersal may have been due to wind turbulence. PUERTO RICAN, 1984 In 1984, after an explosion and fire, the tanker Puerto Rican broke in two, spilling 25,000 to 35,000 bb} of refined petroleum products, mostly lubricating ails, in the Point Reyes-FaraDon Ts- land Marine Sanctuary, 25 mi west of San Francisco Bay. Within 10 hr the Regional Response Team, acting under the State of California Contingency Plan, granted final approval for dispersant use based on an apparent threat to marine mammals (Herz, 1986; Herz and Kopec, 1985~. Dispersant application was delayed 4 to 5 hr. how- ever, because wind and wave conditions prevented a sampling vessel from reaching the scene (the Regional Contingency Plan required samples). An airplane sprayed about 2,500 gal (60 bbl) of Corex~t 9527 on about half of the spill. Dispersion estimates by aerial observers ranged from none to 20 to 30 percent. During 2 to 3 weeks, oil skimmers collected 1,500 bb} of oil-water emulsion (50 percent), ac- counting for only 2 to 3 percent of the amount spilled.
