RIASSUNTO
Introduction
On 4th February 1970, the tanker Arrow struck Cerberus Rock in the entrance to Chedabucto Bay, Nova Scotia in bad weather. The Arrow, under charter to Imperial Oil Ltd., was carrying 16,000 tons of Bunker C oil for a pulp mill at Point Tupper, N. S. The loss of most of the cargo resulted in an oil pollution incident of such magnitude that the Minister of Transport established a Task Force with wide authority to draw on all resources of men and materials necessary to minimise the consequences of the spill.
In support of the Task Force, a Scientific Co-ordination team was established and charged with the responsibility of identifying and recording as much information as possible which might be of use in this and possible future spills.
One feature of the spill was that it took place in cold water and was a presage of what might be experienced in a spill in Arctic waters.
This paper deals mainly with the way in which oil behaves when it interacts with the environment and the effect of these interactions on the effectiveness of clean up techniques. Much information has been drawn from the reports of the Task Force to the Minister of Transport (1) although the interpretation is my own.
Attempts to Recover Cargo
The few days subsequent to the day of the grounding of the Arrow were remarably fine for the time of year and attempts were made to recover the cargo. The bow section was badly holed and although the ship could not be salvaged, attempts were made to tow off the stern section which appeared to be relatively intact. These attempts were unsuccessfull and the stern sank in approximately 90 feet of water and took with it about 1/3 of the cargo. All the oil contained in the bow section and the ruptured midsection was lost. Much of this came ashore within the Bay but one large slick travelled out to sea to contaminate the shores of Sable Island which lies approximately 100 miles to the southeast. The movement of this slick is discussed in detail in the paper by Warner, Graham and Dean presented at this Conference.
The Task Force assigned top priority to the recovery of oil from the sunken stern section since the spilled oil was mostly ashore or trapped in ice and consequently the oil in the stern posed the greater threat. This operation, supervised by Mr. Sven Madsen of Esso International, .was most successfull and approximately 5,000 tons were recovered. A key feature was a ""hot tap"" connection of a flanged valve to each storage tank. Pumping lines were then connected to a barge moved over the wreck. Since the temperature of the water was around 32 0 F, the oil had become highly viscous as it cooled and steam had to be led down into each tank before the oil could be pumped to the awaiting barge.