On the evening of August 6, 1990, the Cypriot tanker Sea Spirit
and the Norwegian Liquefied Petroleum Gas (LPG) carrier Hesperus
collided in the Strait of Gibraltar.
The Sea Spirit was holed on the starboard side above and below the waterline,
causing approximately 48,875 barrels of oil to be spilled into the Mediterranean Sea.
Estimates of the total volume spilled ranged from 48,875 to 89,426 barrels.
The bows of the Hesperus were destroyed,
but the vessel was still capable of sailing and did not leak any of her cargo.
Prevailing currents drew the oil into the Mediterranean Sea.
The oil was caught in the flow of a clockwise gyre between Morocco and Spain
and made approximately two to three revolutions in the gyre over the following week,
breaking up and dispersing naturally.
As the main body of the oil moved in the gyre,
it passed within a few miles of the Moroccan coast, near Punta de los Frailes.
The oil spread out with extensive sheen due to the warm, calm conditions at the time.
Sheen and large patches of emulsified oil were visible from overflights,
and reported by fishermen and observers in vessels in the waters off the coast.
Oil began to come ashore on the coasts of Spain and Morocco within a few days of the spill.
The Moroccan province of Al Hoceim was the hardest hit area.
The first impacts here were on August 13.
Large slicks were observed in the bay and in nearby offshore areas of Al Hoceim.
Most of the oiling along the Moroccan coastline consisted of a band of tarballs between two- and six feet wide.
With the exception of a few sites, this band was nearly continuous
for the approximately 600 kilometers of Moroccan coastline.
Slicks were monitored and tracked as they neared the coastlines of Spain and Morocco.
Heavy fuel oil is resistant to chemical dispersants.
Spanish authorities attempted with little success to break up the slick with dispersants sprayed from a tug.
A representative from the International Tanker Owners Pollution Federation, Ltd. (ITOPF)
recommended that chemical dispersant use be discontinued,
as it could have made mechanical cleanup techniques ineffective.
No other open-water cleanup and recovery operations were undertaken.
Another tug remained offshore monitoring the slick with boom, a skimmer, and dispersants aboard,
but these dispersants were never used.
The oil was mechanically dispersed at sea and in coastal waters.
This involved running a boat through the oil at high speed,
churning and breaking up the oil into smaller particles.
Because of this technique, most of the beach impacts were in the form of tarballs and lumps of oil.