The Chevron refinery in Burnaby, B.C., turns crude and synthetic oils, condensate and butanes into 50,000 to 55,000 barrels of gasoline, diesel and jet fuels, asphalts, heating fuels, heavy fuel oils, butanes and propane every day. (Chevron)

Workers at the Chevron oil refinery in Burnaby, B.C., are trying to stop oil from seeping into the waters of Burrard Inlet, but have yet to find the underground source of the contamination.

Last month, a routine inspection by workers revealed a mix of gas, oil and diesel in a trench near the refinery, located east of Vancouver, and an oily sheen on a small section of beach on the shores of the saltwater inlet.

"There was evidence detected of hydrocarbon, kind of an oily substance.… A combination of a gasoline material, a crude oil material and diesel," according to Chevron Canada spokesman Ray Lord.

The company now is working to contain the contamination by inspecting its pipes and by cleaning up the beach, said Lord.

"Our primary focus is to limit the introduction of any more of the material into the system and continue with the recovery of the material," said Lord.

But it is still not clear where the toxic substance is coming from, how long it has been seeping out and how much has already leaked.

"We don't have a definitive source yet, although it does seem to be localized," he said.

Lord said it's not an oil spill, but seepage, meaning the oil is bleeding from underground into the waters of Burrard Inlet.

"Depending on rainfall, depending on the pace, it's being picked up by groundwater. It's impossible to determine an amount at this point in time," he said.

Fouling 'unacceptable,' says Burnaby councillor

That doesn't sit well with Burnaby Coun. Dan Johnston, who chairs the city's environment committee.

"I'm quite, quite concerned. This is an issue that's unacceptable," said Johnston.

Chevron has had a system in place since 2004 to test the perimeter of the refinery for breaches, and Johnston said the company should know by now exactly what's happening.

"They need to assure the community as a whole that in fact they're capable of operating the refinery without this kind of incident happening," he said.

Harold Riedler, an environmental emergency response officer with B.C.'s Environment Ministry, is overseeing cleanup efforts.

"Right now my job is to ensure Chevron Canada complies with our legislation," Rielder.

That includes stopping the seepage, cleaning it up with no further pollution, testing for contamination, notifying anyone affected and putting systems in place for prevention.

At this point, Riedler said, officials don't believe the seepage is large enough to be a public safety risk, but the natural environment surrounding the North Burnaby refinery could be at risk.

"Certainly there are insects that use that shoreline, and birdlife, feathers could be fouled," he said.

Testing is expected to get underway next week, to determine the extent of the contamination, he said.