Environmental Expert Tim McDonald: Buried Oil Tank

The life span of an underground oil tank (UST) is limited. Most homeowners are not clear as to the age of their tank. Usually it was installed in the ground when they bought their house. Of course, they know the approximate age of their house but not if the tank was original or a replacement. The majority of USTs are steel and therefore subject to rust and corrosion. It also likely that USTs contains a small amount of water and can therefore be rusting from the inside out, as well as the outside in.
If left in the ground, eventually all USTs leak. There is no telling how long any tank will last. Its life span is governed largely by unique site conditions. A leak can mean soil and groundwater remediation (but does not always have to). This is a problem that can be avoided by removing your UST, usually a one day job, and replacing it with a new above ground tank.