Chedabucto Bay 1992 shoreline oil conditions survey: Long-term fate of Bunker C oil from the Arrow spill in Chedabucto Bay, Nova Scotia, 1970

A field survey was conducted from June to September 1992 to locate and document any residual oil on the shores of Chedabucto Bay, Nova Scotia. The grounding of the tanker Arrow in February 1970 released more than 11 x 106 liters of Bunker C fuel oil. The oil was stranded over an estimated 350 km of shoreline, but less than 50 km was treated during the cleanup effort. The systematic ground survey documented the presence of oil on 13.3 km of shoreline in Chedabucto Bay. Heavy oiling is restricted to 1.3 km, concentrated primarily in the Black Duck Cove and Lennox Passage areas. Natural weathering accounts for the removal of the majority of the oil from Chedabucto Bay. Where oil remains, it occurs as a thin stain on bedrock or coarse sediments or as a resistant oil-sediment asphalt-like mixture. Areas in the low wave energy environment of Haddock Harbour and Inhabitants Bay that were heavily oiled in the spill and were not cleaned are now virtually free of oil. These areas have a plentiful supply of fine-grained suspended sediments that may have contributed to clay-oil flocculation weathering as described for Prince William Sound, Alaska. Oil remains on the shore when it is: outside the zone of physical wave action required to move sediments and/or abrade the oil; in areas of nearshore mixing where fine sediments are not present to weather the oil through biophysical processes; and when it is weathered on the surface, forming a crust that prevents biodegradation processes from being active. 45 refs., 17 figs., 6 tabs