Incident Name: Arrow
Subject: USCG Case History
Incident Date: 2/4/1970
Incident Location: Nova Scotia, Canada
Author: USCG Case History
Latitude: 45 28 N
Longitude: 061 06 W
Product: Bunker C Oil
Type: 4
Volume: 77000
Source:Tank Vessel
RAR: Commercial fishing areas, soft shelled clams, lobsters, scallops, lobster fisheries, fish processing plants, seals, gulls, petrels, fulmars, waterfowl, wading birds, alcids, recreational beaches.
Dispersants: Yes
Bioremediation: No
In-Situ Burning: Yes
Special Interest Topic(s): Wildlife impacts, adverse weather conditions, research conducted.
Shoreline Type(s) Impacted: Mixed sediment beaches, sand and gravel beaches, exposed rocky shores.
Summary: On February 4, 1970, at 0935, the steam tanker Arrow ran hard aground on Cerberus Rock in Chedabucto Bay off the coast of Nova Scotia, Canada. The vessel had been traveling off course at nearly full speed when the grounding occurred. The Arrow broke into two pieces on February 12, spilling between 77,000 and 82,500 barrels of Bunker C Oil into the waters of the bay. Visibility at the time of the grounding was between five and six miles, water temperatures were very cold and there was ice in the bays and inlets. There were high winds and seas at the time of the spill. This worked to spread the oil into Chedabucto Bay, and the oil eventually impacted approximately 300 kilometers of the bay's shoreline.
Behavior: Bunker C fuel oil is a heavy product with an API gravity that ranges from 7 to 14. Oil near the spill site took the form of rainbow, silver and dull sheen. Oil was also visible in the water in the form of chunks, which were described as "the size of a hand towel, rolled lengthwise". Oil at the spill site was observed as a long narrow slick extending to the east. This pattern was seen usually during periods of calm or light winds.
Oil moved under the influence of tides and currents and impacted the shoreline generally between the mid and high tide line. In some cases, the oil was driven above the high tide line by storms. In Chedabucto Bay, approximately 300 kilometers of shoreline were oiled ranging from a trace to very heavy coverage. In the lagoons and other low-energy locations, the oil mixed with sand and weeds. The north and west shores of the bay were heavily oiled and formed a tar-like mix of Bunker C and sediment.
Oiled shorelines in high-energy locations were cleaned by natural processes within two to three years. Only traces of oil and no apparent damage to the ecosystem could be found in long-term studies of these areas. In low energy locations, such as Black Duck Cove and Janvrin Lagoon, damage to the ecosystem was still visible and the amount of oil on the shoreline remained relatively unchanged over seven years later.
Countermeasures/Mitigation: Large oil slicks were dispersed by wave action and chemical dispersants. Ten tons of the dispersant Corexit 8666 were applied to large portions of the oil. \\Oiled wharves and boats were cleaned with steam. Steam cleaning in this case was the best alternative, as it required no solvents or detergents, provided portability, required little maintenance and support, and could be used by crews of unskilled laborers. The oil removed during cleaning was absorbed by peat moss placed in the water and recovered with slick lickers, an oleophilic-belt type skimming system. These were used at various locations during the cleanup and were very effective at removing high viscosity oil.\\Oil remained for the longest time on the sheltered mixed sand and gravel beaches. Cleanup of these areas was performed by both manual and mechanical means. Mechanical equipment in these areas caused damage to the back of the beach and mixed oil deeper into the sand than it had been. Scrapers were not effective on the coarse gravel beaches, and only somewhat effective on the compact sand beaches. Oil was still visible to observers ten years after the spill in some of the sheltered areas.
Other Special Interest(s): Remaining cargo was removed from the stern section of the sunken vessel by hot-tapping in approximately ninety feet of water. Pumping operations began on March 2 and were concluded on April 11. Two boilers installed on the recovery barge were used to heat the cargo. Approximately thirty-seven thousand barrels of oil and emulsified oil and water were removed from the Arrow. The extremely adverse weather conditions, including snow, ice, high seas and gale-force winds, added to the difficulty of these operations.\\The scientific coordination team set up a large laundromat for cleaning oiled fishing nets. This cost approximately $22,000, but saved considerable time and money over replacing all the oiled fishing nets. These nets cost approximately twenty-five thousand dollars each.\\Experiments were conducted during the spill to test the effectiveness of various natural sorbents and burning operations. At several sites in Chedabucto Bay, peat moss was tested as an absorbent. Peat moss was spread on the beach and oil was allowed to wash over it, or was forced onto it with booms. The peat moss would stick to the oil and the mixture could be easily removed with a rake. The peat moss was found to be very effective as an absorbent for Bunker C oil on sand beaches. Its ability to absorb decreased as the oil weathered and formed a water-in-oil emulsion. An experiment involving steam cleaning was performed at a test site that had not previously been oiled. Rocks were purposefully covered with oil and then steam cleaned. The oil ran onto peat moss that was being held by boom to keep it from moving downstream, and to prevent further contamination of the area. \\In-situ burning experiments were conducted on two-inch thick patches of oil that had been exposed to the water for more than two weeks. In two separate sites, peat moss was used as a wick, and fuel (gasoline or turbofuel) was used to start the fire burning. Results of both tests were negative. This is believed to be due to the amount of weathering that had already taken place.\\On February 14, 1970, only ten days after the grounding of the Arrow, an oil barge called the Irving Whale spilled between 100 and 200 barrels of Bunker C oil off the southeast coast of Newfoundland. This barge was later used to receive oil pumped from the Arrow during the salvage and lightering operations. (The Irving Whale sank off the northern coast of Prince Edward Island in July 1970 with a cargo of Bunker C aboard.) The spill from the Irving Whale is estimated to have caused the deaths of at least 5,500 birds along the southern coast of Newfoundland. \\Both the Irving Whale and the Arrow caused the deaths of a large number of birds. The two spills caused the known deaths of 1,500 ducks and seabirds, and deaths of an estimated 12,000 birds.
References: Brown et al. 1973. Bird Mortality from Slicks off Eastern Canada, February-April 1970. Canadian Field-Naturalist 87: 225-234.
Canadian Ministry of Transport. Report of the Task Force-Operation Oil (Cleanup of the Arrow Spill in Chedabucto Bay). 1970.
Environment Canada. 1982. Oil and Dispersants in Canadian Seas- Research and Appraisal Recommendations.
Hooke, N. Modern Shipping Disasters 1963-1987. Lloyds of London Press. 1987.
Mostert, N. Supership. 1974.
Report of the Royal Commission. Pollution of Canadian Waters by Oil and Formal Investigation into Grounding of Steam Tanker "Arrow". 1970.
Review of Oil Spill Occurrences and Impacts, Exxon Production Research Company, 1989.
Tanker Advisory Center, Inc. 1991 Guide for the Selection of Tankers. T.A.C. Inc. 1991.
Wilson, M.P. Jr., et al., "The Spreading, Retention and Clean-up of Oil Spills", URI, Kingston, RI, 1976.
Last Edit: 9/18/92
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