Frequently Asked Questions


Not sure if you want to purchase a house with an underground oil tank?

Test soil and find out if  the tank is leaking oil into the ground. This will help minimize your risk. Soil test results take about three business days to get the results.

Not sure if there is an abandoned underground storage tank is buried on your property?

To assist you in finding if there is or was an underground oil tank on your property, first go in the basement and look for abandoned oil piping, copper fuel lines, or patch-marks on the foundation wall where such lines may have been removed. On the outside of the house look for an old vent pipe that is usually fastened vertically along side of the house. The vent pipes are usually 3/4 to 1 ½ inch galvanized piping and in many cases has a cap that looks like a mushroom on the top of the piping. As for the fuel tank fill pipe, it is protruding from the ground and the fill pipe will have a special cap that in some cases may be difficult to remove. A fill pipe will be needed to accurately measure and decommission your heating oil tank.


What should be done with an abandoned underground storage tank?

Department of Ecology and many Local Fire Departments recommend permanent closure for abandoned underground storage tanks. The process of permanently closing a tank is referred to as "decommissioning". A tank may either be decommissioned by capping, filling it with an inert material such as slurry or foam or by removing it from the ground. Decommissioning also involves removing heating oil and sludge from the tank.

Many underground storage tanks have been abandoned with oil still in them. You should consider arranging to have any remaining oil removed from the abandoned tank if you do not immediately decommission it. This will help prevent possible contamination of soil and ground water.

Why should I decommission my abandoned underground storage tank?

Abandoned underground storage tanks are a potential source of contamination of the soil and ground water and may pose a fire and explosion hazard under certain conditions. Underground storage tanks can corrode and deteriorate and possibly cave-in and collapse. They should be decommissioned whenever they are no longer used or whenever there are questions about their structural integrity or about their ability to hold product without leaking.

Under the Model Toxics Control Act, a tank owner may be held liable for contamination caused by a leak.

Many times the tank does not become an issue until the home owner decides to sell their home and at that time has an inspection done on their home. These inspections are often done one to two weeks before closing. Before finalizing the sale of a house, lending institutions and home buyers may want sellers to remove or decommission the abandoned heating oil tank.

Is there a problem if I have an abandoned tank on my property?

Discovering an abandoned tank on your property doesn’t mean that it has leaked or caused an environmental problem. Although most abandoned underground storage tanks do not cause major environmental problems or health risks, ignoring an abandoned tank is not recommended. Even if it has not yet caused a problem, it could in the future.

Dealing with your tank now may prevent or at least minimize future problems and expense. Some abandoned tanks have leaked heating oil, resulting in contaminated soil and ground water and expensive cleanups. Leaking oil can migrate into a basement or crawl space of your home and, although unlikely, the fumes from the oil could cause a fire or health risk. Also, an abandoned tank may cause a safety hazard even if it has never leaked. Over time tanks will corrode and deteriorate and possibility cave-in and collapse.

If my underground storage tank has leaked, what should I do?

If a tank has leaked, the Washington State Department of Ecology regional office does have reporting requirements based on the extent of contamination found. Minor leaks or spills from residential heating oil tanks do not have to be reported to the Washington State Department of Ecology. Minor leaks are those that affect only the soil near the tank.

According to Washington State Department of Ecology's report R-TC-92-117, it is the owner's responsibility to evaluate the extent of contamination caused by the leak, then determine if it is a threat to human health and the environment and clean up any contamination caused by the leak.

A significant leak requires that the tank be removed and as much of the contaminated soil be removed according to the regulations indicated by the state Model Toxics Control Act.

What is polyurethane foam?

Polyurethane foam is a safe close cell material. Water cannot penetrate polyurethane. When you consider the health and safety factors, along with the strength and structural integrity of the product, polyurethane foam is by far the logical choice for abandoned underground storage tanks. Polyurethane foam provides structural integrity and has tensile strength and compressive strength and eliminating the chance of caving. It sets up like concrete. An underground storage tank filled with polyurethane foam will not float or pop out of the ground. Various polyurethane foams are used in construction, typically for roofing, ground perimeter insulations, wall insulation and sheathing.

The polyurethane foam used to fill underground storage tanks presents no health hazards. It is chemically inert and insoluble in water and most organic solvents.  Partially because of its inert properties, polyurethane is the polymers of choice in many biomedical applications.  Do not confuse polyurethane foam with urea formaldehyde foam. There is a major problem with urea formaldehyde foam – it’s a potential health hazard. In recent years, public concern about the adverse health effects of urea formaldehyde foam insulation has been in the spotlight.  If the underground storage tank needs to be removed from the ground at a later date, the foam in a 300 gallon tank will weigh approximately 80 pounds versus approximately 5400 pounds for concrete slurry.

Do not confuse polyurethane foam with urea formaldehyde foam. There is a major problem with urea formaldehyde foam – it's a potential health hazard. In recent years, public concern about the adverse health effects of urea formaldehyde foam insulation has been in the spotlight.

If the underground storage tank needs to be removed from the ground at a later date, the foam in a 300 gallon tank will weigh approximately 80 pounds versus approximately 5400 pounds for concrete slurry.

What is the difference between a foam filled or slurry filled tank?

The removal of a polyurethane foam filled tank, if ever required, is less complicated than slurry since the polyurethane foam is relatively light in weight. The foam in a 300 gallon tank will weigh approximately 80 pounds versus approximately 5400 pounds for concrete slurry.

How do I know if my tank is leaking?

Many residents use heating oil to heat their homes and, unfortunately, most residential heating oil tanks are 30-50 years old. Leaks are common when tanks get this old, but there are some simple ways to determine if your tank is leaking:

Track your oil use. If your furnace seems to be using unexpected/unexplained more fuel oil consumption and the weather hasn't justified an increase, your tank may be leaking.

Sometimes a tank will contain oil and water, or primarily water (the water will settle to the bottom; the oil will float on top). To check for water, put a small amount of water-reactive paste on the end of a stick and insert the stick into the tank. If water is present, the paste will change color.

Water in your tank in most cases indicates that the tank has failed and water is entering the tank through a hole. If water is getting into the tank, oil is most likely getting out and the tank should be inspected as soon as possible.

During the summer, when you're not using your furnace, measure the level of oil in your tank using a long rod, tape measure or some other measuring device. After a few weeks, measure it again. If the level is lower, then the tank is probably leaking. If the level is higher, then you should check to see if water is entering the tank.

If you smell oil around the tank, near your property's catch basins or in your basement, oil may have leaked from your tank. It may also have infiltrated to the bedding area of nearby underground pipes and found a drainage course into the groundwater or surface water. Residential heating oil is dyed a red color, so that it is easily identifiable.

What if my tank has a leak?

If you find that your tank has a leak, you should take immediate action to stop the leak. Call Filco Company, Inc., and we can assist you.

No longer using your tank and have an abandoned heating oil tank?

If you have switched from home heating oil to natural gas or electricity as a means to heating your home, and your heating oil tank that is no longer in use, then it's a good idea to have it decommissioned. It is especially a good idea if you plan on selling the house. Often, home buyers and lending institutions require assurance that the property being sold is not contaminated; and the best way to do that is to remove the tank and sample the surrounding soil. If removal isn't possible, and you don't expect to sell the house, you can decommission your home heating oil tank by "close your tank in place" by pumping out the oil, cleaning out any sludge, triple rinsing it clean, and removing or capping lines or filling the tank with inert solid material.

Have all unused heating oil removed from your tank.

Ecology strongly recommends that you have all unused heating oil removed from your tank. Removing the unused oil is the easiest, least costly, and single-most important action you can take to prevent contamination of soil and groundwater. After the heating oil has been pumped out of your tank, you should think about having your tank removed or "closed in place".

What is the life expectancy of an underground oil tank?

While some underground heating oil tanks have lasted longer, a common life expectancy of buried underground oil tanks is approximately 10-15 years. The odds of a leak happening increase, as the tank gets older. Even small, slow leaks can pose significant risk to the environment if they go undiscovered for a long time. The best way to avoid the problems associated with a leaking tank is to have your tank taken out of the ground and have a new tank installed, either underground or above ground.

What is an "Abandoned" underground storage tank?

Many underground storage tanks are no longer being used, rendered obsolete by piped-in natural gas or electric baseboard heat or heat pumps. An underground storage tank that is no longer in use is considered "abandoned".