When you visit the gas station, gas is pumped into your car. But where was the gas before it entered your car? It was in a very large underground storage tank located under the service station's driveway.

All over the US, underground storage tanks hold gasoline and many more toxic materials. Materials that, if leaked, can cause a lot of destruction.

To understand how this destruction occurs, you need to understand that underground streams flow beneath the land. The streams are called aquifers. There are two aquifers, a shallow aquifer and a deep aquifer.

Many of us obtain our drinking water from these streams. This happens in one of two ways.

Many people have their own on-site wells. Those wells supply water, usually for one home or building, from an aquifer.

Many other people obtain their water from water supply companies or agencies. In those cases, often the water is obtained from a group of wells. Wells situated next to one another are often called a well field.

Back now, to the tanks. When the tanks leak gasoline, or whatever else they have, the contents leak into the soil and often end up in an aquifer. If that aquifer feeds a private or public well water source, the drinking water risks becoming contaminated.

In every state, enforcement actions occur after a leak has been discovered. Tank owners and operators are sent orders requiring them to fix the problem and address the contamination. Fines are usually available if a person fails to honor these orders.

The problem with this approach is that it is akin to locking the barn door after the horse has already escaped. Yes, after the fact cleanups can be effective, but they always take forever, cause needless disruption, and are very costly.

Cost can be a real problem. When gas from a leaking tank just affects local soils, cleanups are usually not that costly. But once ground water is affected, forget about it! The costs can run into the hundreds of thousand dollars - if not more.

Which means that the key is to avoid the leaks in the first place. That's such a simple idea, but it where the system falls apart.

While some monies have recently been made available both at the federal level and state level to increase inspections, not enough is being done. All tanks that are underground must be inspected, at least once a year. More often would even be better.

We have seen spills that have wiped out drinking water supplies for hundreds of people. The costs to cure the problem can run into the millions of dollars per large scale incident.

While frequent inspections seem costly and unrealistic, this approach is the only one that makes sense.

And another thing: where possible underground tanks should be replaced with above ground tanks. Obviously that is not always possible, such as in the case of gasoline storage tanks and large heating oil tanks.

But in the case of many smaller tanks, they need to be replaced above ground, not back below.

Underground tanks require frequent inspections to safeguard the environment. And when possible, they need to be replaced with tanks that sit above.

The information provided in this column is written by Stuart Lieberman,a practicing environmental attorney, and is for general information purposes only. It is not legal advice and should not be used in place of legal advice.

Stuart Lieberman, Esq., and IRED.Com, Inc., will not accept any responsibilty for any reliance on the information in this column or any damages whatsoever resulting from reading this column.