Chilliwack residents were warned not to go outside as smoke from thousands of litres of burning oil at BC Hydro's Atchelitz substation filled the sky Friday afternoon.

Winds blew that smoke across and past the city within hours, but it is still to be determined what environmental damage was caused by oil that leaked from the site.

"Some of the oil was burned, some of the oil we were able to contain on the site and some did escape from the site, but it's been contained in a ditch right outside the fence and we're in the process of cleaning that up right now," B.C. Hydro senior vice-president David Lebeter said Friday.

On Monday, BC Hydro reported the site of the fire had cooled and was no longer emitting smoke.

A spill response contractor and an environmental consultant was on site to contain the spilled oil.

"BC Hydro has hired an environmental consultant to develop a sampling and monitoring plan that will be reviewed by the ministry and other agencies," a statement issued to the Times said.

"Ministry of Environment Environmental Emergency Response Officer (EERO) will continue to work with BC Hydro and other agencies to determine environmental sampling, monitoring and remediation requirements moving forward."

Some concerns had been raised about PCBs in the oil, which was used as a coolant at the transformer, but Lebeter said the levels were "so low they're barely measurable."

Lebeter said Hydro personnel were not finding any trace of contamination beyond a ditch just outside the substation fence.

phenderson@chilliwacktimes.com