Statistics indicate as many as 25% of all Underground storage tanks (USTs) may now be leaking. These underground tanks may hold oil or gas but can most frequently be found at homes heated with oil. Over time, there is a tendency for these older tanks to corrode and leak their contents into the ground and possibly into the ground water. Because of the great expense involved in cleaning up the contamination caused by leaking tanks, it behooves those that have older underground tanks, to have them or the soil tested.

Because most underground oil tanks are steel, this steel can rust over time allowing the oil or gas to leak into the ground. Although it is hard to pinpoint exactly what age this may occur, the state of Maryland has stated that any tank over the age of fifteen may be at risk of leaking. It is recommended that any tank over twenty to twenty five should be checked to insure it's integrity.

If a tank begins leaking its contents into the soil the owner of the tank (house where tank is located) whether a new owner or long time resident may be responsible for the cleanup. It is important to remember that the only time that cleanup is required is when the oil or gas actually contaminates the ground water or public waterways. Obviously, those with high water tables or in close proximity to a public waterway, ie. stream, creek, river or bay have a higher risk of being responsible for cleanup. If a new homeowner buys a house with an oil or gas tank that has contaminated a body of water, that new owner is responsible. There are many horror stories of "new" home owners finding out that they are responsible for thousands of dollars worth of contaminated soil removal from a newly discovered leaking tank. Unfortunately, the first person who usually finds out about it after the homeowner is the Realtor. As such, both the Real Estate agent and the buyer should contractual stipulate to underground tank testing to alleviate their liability. It should be noted that in most situations homeowners insurance does not cover the expense involved.

There are two common forms of testing available to test underground oil tanks for leakage: Soil sampling and Pressure test of tank. Soil sampling requires the pulling of soil samples from under the tank and then sending them to a laboratory where there are then analyzed for the presence of oil. Normally no more than four samples will need to be pulled unless special circumstances dictate differently. Because the samples must be sent to a lab, time should be budgeted for the lab to analyze and then report results. There are a variety of different methods for pressure testing of a tank. Normally, a vacuum test of the tank is conducted to find any leaks. Unfortunately this type of test may require that the tank have no more than 1/2" of water in bottom, no bends in the oil fill (it must be straight) and the tank must be level or the fill needs to be on the lower end of tank. Some companies are now using sensitive equipment to measure liquid loss in the tank. Either of the above tests may take many hours on-site to conduct.

If a tank is found to be leaking oil or gas, the tank must either be abandoned or removed. The process of abandoning an underground tank is called Closure. Through this process, the tank must be pumped dry of its contents and then filled with sand or a cement slurry mix. The state of Maryland has asked those that are abandoning a tank to report it to the state so they have a record of the location of the tank. Each jurisdiction has different requirements and organizations responsible for USTs. In some areas, the only time a tank may be abandoned is if the removal "would endanger a building structure if removed." It is important that the local agency responsible for USTs be contacted to obtain local regulations. This may be the local fire department, health department, or other county agency.

The desired method for leaking USTs is removal of the tank. Following is the recommended steps when removing an underground oil tank as dictated by the Maryland Department of the Environment (MDE).

1. Notify the Oil Supplier to discontinue oil service to the home.
2. Obtain an approved contractor to conduct the work. MDE maintains a list of those approved.
3. Local jurisdictions may have specific permits to conduct removal, contact governing agency.
4. Have all oil pumped from the tank and lines. Some companies provide a credit for reusable oil removed.
5. Excavate the top of the tank and expose the piping.
6. All piping should be disconnected and drained including the tank fill line.
7. Oil sludge and residue on exterior of tank should be removed and disposed of properly.
8. If tank is clean, it can be disposed of in an approved manner. The contractor or MDE can assist in locating a proper disposal site.
9. If soil or groundwater contamination is found during excavation, it must be reported to MDE immediately upon discovery. Phone number: 410/631-3442 or after hours 410/974-3551.
10. Any residential tank greater than 1,100 gallons in capacity are required to be registered with MDE. Forms may be obtained by calling 410 / 631-3442.

Any home that has an older UST should have it periodically inspected to prevent unforeseen expense to the homeowner. Any house that is being bought and may have an older UST on site should be checked for its condition whether it is requested by the homebuyer or the Realtor. For further information on this subject, contact your local governing agency regulating USTs, the Department of the Environment or the Environmental Protection Agency (EPA).