VICTORIA - Ninety-five per cent of the diesel slick from a barge accident near a killer whale habitat has dissipated since Tuesday, a Canadian Coast Guard official said Wednesday.
Jamie Toxopeus, coast guard environmental response co-ordinator, said the information comes from coast guard staff who took part in an overflight of the spill with Burrard Clean, the company contracted to clean up the mess.
The next step is to do a shoreline assessment by walking the beaches, he said.
Marine scientists say at least 50 orcas have been spotted swimming through the diesel slick near Robson Bight, an ecological reserve on northern Vancouver Island where whales congregate every year to feed and rub their bellies.
Marine mammal scientist John Ford of Fisheries and Oceans Canada said there doesn't seem to be any noticeable change in the whales' behaviour.
They are foraging and moving through the area as they normally do, he said.
The diesel leaked when a partially filled fuel truck and nine other vehicles were dumped into the water when a barge overturned Monday.
Dave Smith of Canadian Wildlife Service of Environment Canada said there have been no confirmed reports of birds picking up oil from the spill.
"There've been some reports of excessive preening and whatnot, which is typical of bird behaviour when they are oiled," he said.
"But no birds have been picked up to date and the beach surveys have indicated that there's no birds on the beach and there's no oil."
Bruce Kaye of Environment Canada told a media briefing diesel evaporates and dissipates more quickly than a heavier fuel such as a bunker fuel oil.
"The evaporation rate can be up to 50 per cent in 24 hours," he said.
"Because it is a lighter fuel and because the amounts that have been found on the surface of the water are quite low, the sheen that is being formed is very thin and as a consequence is not recoverable using oil recovery technology."
Kaye said protective booms have been deployed to prevent the diesel fuel from reaching the shoreline.
The cause of the accident hasn't been determined and it's not known if the barge was inside a protected area off Robson Bight.
The barge owned by Ted LeRoy Trucking of Chemainus, B.C., was en route to Campbell River, B.C.
Fisheries official Peter Ross said a longer-term concern about the spill's effects would be that the heavier fraction of the diesel would get onto the rubbing beaches and form tar balls or emulsify, or coat some of the cobblestones that the killer whales rub on.
Ross said there's also concern the spill could contaminate food sources such as shellfish, which filter large amounts of water and whatever that water contains.
"We're also concerned about what is retained in the coming years," he said. "That may present a health risk for a period of years."
