Leaking roofs and busted furnaces: costly liabilities homeowners dread. But beneath the surface lurks another threat potentially every bit as expensive.

Decommissioned underground oil tanks abound and, if not properly drained, could be slowly contaminating the soil.

One Saanich family learned a hard lesson recently when they were slapped with a bill for more than $20,000 to clean municipal land.

Added to the expense was the cost of hiring an environmental consultant to clean the contaminated soil and remove the tank, discovered buried in the family’s front yard.

It all started when a pedestrian noticed oil bubbling out of a storm sewer outfall two blocks away.

Using a metal detector, Corey Hughes of Victoria Oil Tank Services pinpointed the offending tank to 563 Judah St.

“It was bad,” said Hughes, adding the approximately 4,500-litre tank was too big to have been for residential use.

The company goes on about 10 “treasure hunts” for tanks each day. Usually, they’re called in by real estate agents on behalf of prospective buyers to avoid unpleasant surprises down the road.

Hughes estimates 10 to 20 per cent of the calls turn up tanks. In most cases, the tanks were properly drained when they stopped being used. Still, oil leaks aren’t uncommon, Hughes said. After 14 years in the business, Hughes sees about 25 leaking tanks in Greater Victoria every year.

These days, it’s illegal not to disclose an on-site oil tank or any soil contamination, but that hasn’t always been the case, explained Colin Doyle, director of Saanich engineering.

When the family on Judah moved into their subdivision, built in 1975, they didn’t know the land previously housed a greenhouse heated from an underground tank.

“It’s just a very difficult situation,” said Doyle. “They’re in a situation where they ... didn’t directly cause this and yet they are the property owners now.”

The only recourse the family has to recover some of their costs is to peg the previous owners responsible, he said. In this case, however, it could be difficult. “In all likelihood the previous owner will be deceased given the time lapse here,” Doyle said.

Tax records pinpoint the first owner of the property as Herbert Lee in 1907 and two greenhouses followed. Island Greenhouse Company in 1939 and Park View Greenhouses in 1961. To whom the tank belonged is unclear.

In April 2007, at the request of Saanich Coun. Vicki Sanders, chair of the environmental advisory committee, Saanich published a guide to help homeowners protect themselves from unwanted oil tank expenses.

People often aren’t aware of the need to ask about oil tanks when they buy a house, said Sanders at the time of the web release. And she should know.

She’s removed a tank on her own lot and that of her father. Thankfully, a soil test confirmed no contamination surrounding either, but her neighbour wasn’t so lucky.

“It was a horrendous cost,” Sanders recalled. “She was very upset.”

rholmen@saanichnews.com