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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
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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
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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
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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.
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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.
Representative terms from entire chapter:
main pass
