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Small leaks frequent for underground power cable
An underground transmission line linked to a recent oily sheen in Colquitz River has leaked about 200 litres of oil in the past year, B.C. Hydro says.
The line transmits power between a downtown Victoria substation to a substation near Camosun College Interurban, about nine kilometres, and is encased in mineral oil for insulation.
B.C. Hydro said that at a number of locations the line has been subject to small “drip leaks” into the earth, which it estimates adds up to about 200 litres since last December. Ted Olynyk, with B.C. Hydro, stressed that the petroleum-based mineral oil has “very low toxicity” and won’t harm fish and other wildlife.
“Anytime (a leak) happens, we go to extremes to ensure the environment is protected. We realize there is a lot of community sensitivity about this,” Olynyk said. “This doesn’t harm fish and that’s one of the reasons we use this oil.”
Saanich public works staff discovered an oil sheen on Colquitz River last Wednesday (Nov. 7) near Interurban Road and Columbine Way.
The crew strung absorbent booms across the stream, and B.C. Hydro took over cleanup and remediation late last week, after the corporation was confident the oil was related to its operations.
Olynyk said it remains unclear how many days the oil leaked undetected into the Colquitz. It’s possible oil migrated out from soil relocated from earlier B.C. Hydro excavation work in the area, as the underground cable itself is about 12 metres from the creek.
B.C. Hydro did transmission cable repairs in the area on Oct. 31 after discovering a leak, but Olynyk said there was no evidence any oil entered the creek from that incident. A different section of the cable had a small leak repaired in December.
The system can alert Hydro crews to low oil pressure in the cable, although that didn’t happen in October or this latest leak.
Olynyk said crews walk and inspect transmission lines every few months. Engineers suspect cycles of heating and cooling can cause small cracks in the cable casing.
Saanich environmental services manager Adriane Pollard said B.C. Hydro has taken responsibly for cleanup in partnership with the Ministry of Environment, but Saanich staff remain in the loop.
Pollard said she isn’t aware of other incidents where transmission line fluid has leaked into a Saanich waterway.