Every winter, Environment Canada's Enforcement and Emergency Section fields calls about spilled home heating oil.

"The reasons behind most of the calls are badly identified tanks or poor fuel records," says George Balmer, head of the section.

All too often, delivery companies fill fuel tanks with water or water tanks with heating oil, Balmer says, or try to fill old, unused tanks. Sometimes they pump a tankful of fuel into a tank that is already full, spilling the excess through the basement or crawlspace of the house.

"It will happen even if you don't have an oil furnace and you don't get oil delivered to your house," warns Environmental Inspector Stephen Arrell. "The guy next door might have an oil furnace, and the new driver comes to your house by mistake, finds a stem sticking out, and fills your water tank with oil"

In one case, a fuel truck driver pumped a full tank of fuel into a pipestem sticking up from the crawlspace beneath a house. Unfortunately, he had got the wrong address. The pipestem had once been attached to a water tank, but the tank had been removed, so the entire load of heating oil poured into the crawlspace beneath the house.

In another case of mistaken addresses, a driver pumped fuel into a tank that had been filled only days earlier. The excess oil overflowed along the house foundations and into the basement.

Because people can detect hydrocarbons at extremely low concentrations, even a relatively small spill of heating oil can become a major problem.

"Most human noses are far more accurate than testing devices," says Balmer. On the good side, that means that you are likely to smell the fuel long before it becomes a combustion danger. On the bad side, a small spill can make your house virtually unlivable, and prolonged exposure to fuel can have serious health effects.

"Small amounts of fuel can also contaminate large amounts of groundwater, making it undrinkable," Arrell adds. A leak from an underground fuel tank could contaminate wells hundreds of metres away. The owner of the tank could be liable for the damage under civil law, or even face charges under the Fisheries Act if the fuel made its way into the surface water and affected fish.

Although it's not as easily combustible as gasoline, heating fuel can become a fire hazard, especially if it soaks into wood and dry grass around the tank or under the house.

"If you have a grass fire nearby, it creates a fuel source with a direct connection to your tank and your house," says Balmer. "A pound of fuel is more powerful than a pound of dynamite under certain conditions. When you think of your fuel tank in the ground, your house is sitting on half a ton of explosive."

Cleaning up a major fuel spill is costly, difficult, and not always effective. The best approach is prevention, say Arrell and Balmer.

They recommend labeling all lines leading to storage tanks to indicate which lines are for fuel and which for water. If you have an unused tank or unused line, they say, make it inaccessible or remove it entirely. Make sure any fuel tank has a functional gauge or warning device and keep a record of fuel deliveries in order to avoid overfilling the tank.

They also recommend making sure that above-ground tanks are properly braced. Each year they get calls from people whose fuel tanks have shifted or toppled over, breaking the fuel lines and spilling the oil onto the ground.

The tank owner might be able to reduce the impact of a small heating oil spill fairly simply, Balmer says. First, dig out as much of the contaminated soil as possible. Next, put down a plastic barrier to block any remaining contamination, and fill the hole with clean material.

"Then take your contaminated soil, spread it out thinly on a barrier, and expose it to the air," says Balmer. Within a couple of years, the volatile parts of the oil will have evaporated and bacteria will have broken down the heavy parts. Of course, this process works for pure fuel oil only, not for waste or contaminated oil, he warns.

And all spills should be reported to the Yukon Spill Line, just to be safe, Balmer adds.

For more information about how to handle home heating fuel, contact Environment Canada, Whitehorse. The number for the Yukon Spill Line is (867) 667-7244.