We've been collecting copies of environmental regulations regarding this issue for U.S. states and Canadian provinces since about 1990. Information provided at this web-site is derived from multiple sources, listed at References below where you can link to additional documents. A simple overview of issues for home buyers. Such components are not inspected during a home or building inspection unless specific prior test arrangements have been made. Tank inspection, other than casual visual inspection, tank tests, as well as removal or abandonment require that you use an appropriate expert.
Some general advice is below.
While we've found them lasting longer, a common life expectancy of buried oil tanks is 10-15 years. We do not have the same data for gas tanks. Life may be similar. Buried tanks should be tested for amount of water present in tank bottom, and water should be pumped out. Water corrodes the tank and leads to leaks.