How to spot one, and what you need to do.
What is Heating Oil?
Heating oil (also called fuel oil) is chemically very similar to diesel fuel. Before our current natural gas infrastructure was built in BC, oil was a popular heating option. Heating oil is cheap, energy dense, and easy to store. It was widely used until the 1970's throughout the province. It is still used today in rural areas, or in locations without natural gas infrastructure such as Golden, BC.
How Was it Stored?
Oil furnaces are very similar to natural gas furnaces, except they burn a liquid fuel instead. This fuel is most commonly stored in a tank either above or below ground. These tanks can be installed near to, inside, or occasionally underneath a house.
Why Would You Bury an Oil Tank?
Great question. It seems like a bad idea in retrospect, but at the time it may have seemed like a practical way to hide an unsightly tank, and gain back some yard space. Safety and environmental standards weren't what they are today, and the fear of a tank rusting out and leaking was either not considered, or not sufficiently concerning.
Why Are They a Problem?
As you can imagine, a single-walled metal tank buried in the ground will rust at some point, which is exactly what happened. If a tank rusted, heating oil would leak out slowly without being detected, and leach into the soil and contaminate the groundwater.
Leaking tanks can contaminate soil and groundwater.
Cleanup is Expensive
Mitigating a fuel spill can be expensive and labor-intensive. In order to properly remediate a spill, all contaminated soil has to be removed and disposed of, along with the old tank. This could mean significant excavation, soil testing, and environmental assessment. A buried oil tank is the responsibility of the current owner of the house.
How Can I Spot One?
If you suspect that there may be a buried oil tank, there are a few clues to look for.
Vent and Fill Pipes
These were typically 2" in diameter, and located near the front of the house. They stuck up out of the ground, and sometimes were attached to the house itself. They would be in a location that would provide reasonable access for the fuel truck to refill the tank.
Supply Lines
Supply lines were typically 3/8" copper, and came through the foundation wall, or up through the floor. There would normally be two, one supply and one return line. They were sometimes made of steel or brass, and they could also be a larger in diameter (up to 2" diameter steel lines were used in very cold climates).
Emergency Switch
Oil furnaces were equipped with an oil flow valve that could cut off the fuel to the furnace in an emergency. The emergency switch for that valve was not always removed when an oil furnace was decommissioned.
How Can I Know for Sure?
If you suspect there may have been a buried oil tank, the only way to know for sure is to hire a professional. A tank detection specialist may use sensitive metal detection and/or ground-penetrating radar to confirm if there is a tank on your property. If a tank had been previously removed, the seller should be able to provide the official documentation as proof.
Key Points
Oil was a popular heating fuel until the 1970's.
Buried oil tanks can leak, contaminating soil and groundwater.
These tanks can be expensive to remove.
A buried oil tank is the homeowner's responsibility.
The only way to know for sure is to hire a specialist.