On September 7, 1970, the oil barge Irving Whale sank during a storm into the Gulf of St. Lawrence about 60 kilometres northeast of North Point, Prince Edward Island. The barge, which originally contained 4200 tons of bunker C oil, laid to rest in about 67 metres of water. After the initial spill of oil, the frigid temperatures of the water caused the oil to congeal. Leakage over the intervening 26 years was minimal. By 1996, 3100 tons (3,214,700 litres) remained in the submerged barge.

Over the years, the Canadian Coast Guard maintained surveillance of the Irving Whale site to monitor pollution. Detailed underwater inspections of the barge where made in 1989, 1990, 1993, and 1994, and recommendations to remove the oil and/or raise the barge followed. In August 1994, the decision to proceed with raising the barge was announced, and by June 1995, the contract to raise the barge was awarded.

On June 23, 1995, Environment Canada became aware of the presence of PCB-based heating fluid in the Irving Whale. It was estimated that the barge contained 5440 litres of PCBs, and samples taken from the adjacent seabed revealed traces of PCBs, although it was determined that no PCBs were presently leaking from the barge. After further study the Canadian Coast Guard gave the final go-ahead to proceed with the salvage operation on April 16, 1996.

Substantial efforts were made to ensure this type of accident did not occur. Environmental studies were conducted to anticipate possible effects that a break-up of the barge could cause and equipment for minimizing the extent of possible damage was obtained. In particular, conditions of the seabed surrounding the Irving Whale, as well as surface wind, weather and sea-state conditions at the exact time of salvage, were of concern.

A variety of technologies was used to best determine these conditions. Submersible digital sonar sidescan equipment was employed to create a horizontal image of the Irving Whale and the surrounding sea bottom. The sidescan showed salvagers both the Irving Whale and its features as well as boulders strewn on the sea floor around the barge. To determine the current surface conditions, traditional meteorological methods were used as well as RADARSAT SAR data and air photos. In preparation for a potential oil spill this information along with a DC-3 mounted Laser Fluorosensor, an instrument that measures the fluorescence of oil at depths of up to five metres, was made available to help with cleanup efforts.

The Irving Whale presented a scenario where RADARSAT acquisitions could be planned to support both pre- and post-raising activities. For pre-salvage operations, the RADARSAT SAR was used to check for oil on the surface. The detection of oil on water is best optimized using RADASAT's steeper incidence angles. Also Wide beam position 1 and 2 were employed to provide the optimum trade-off between the coverage and resolution needed. On July 28, 1996, the first RADARSAT scene was collected. The operation required fast delivery, within hours of data acquisition in preparation for the salvage operations which began on July 29th. Unfortunately, calm sea conditions made the detection of oil difficult and none was observed on the image, although small amounts were known to be on the sea surface. During the actual raising of the barge on July 30th approximately 4,500 litres of oil were spilled. The resulting 55 square kilometre spill was cleaned up on site and monitored by airborne Fluorosensors, aircraft equipped with video cameras, and ship-based operational personnel. The spill was considered small and was cleaned up without difficulty.

The next available image was acquired July 31st, 36 hours after the spill and clean-up operation began. Quick image delivery was a major priority and the first TIFF image of the recovery site was delivered within two hours of the RADARSAT pass and a larger, more detailed image was delivered within five hours of acquisition. By the time this image was acquired, most of the oil spill had been cleaned up, but three residual slicks were visible on the July 31st image. Some oil sheens present in the Gulf area, detectable by airborne Fluorosensors, were too thin to dampen capillary wave action and were unobservable on the RADARSAT image. This demonstrates RADARSAT can detect oil spills but cannot determine their thickness. Therefore, the use of RADARSAT in conjunction with Laser Fluorosensors, as complementary technologies, would be the most effective method in determining spill size and thickness.

A final RADARSAT image was collected on August 4th. Again, calm wind conditions limited the usefulness of the imagery. A number of areas on the image were interpreted as possible spill locations, although on-site observations did not find oil present. This, again, highlights the need for additional information and the value of field work to validate interpretation results.

The raising of the Irving Whale helped to demonstrate proof-of-concept for using RADARSAT images in this type of operation. The information provided was useful for both the documentation of the event and monitoring potential problems. "Any RADARSAT data would have been useful for Spill Response Management had an accident occured", said the Operations Manager.