Leaking underground storage tanks (LUST) that hold toxic substances have come under new regulatory scrutiny in the United States because of the health and environmental hazards posed by the materials that can leak from them. These storage tanks typically hold petroleum products and other toxic chemicals beneath gas stations and other petroleum facilities. An estimated 63,000 of the nation's underground storage tanks have been shown to leak contaminants into the environment or are considered to have the potential to leak at any time. One reason for the instability of underground storage tanks is their construction. Only five percent of underground storage tanks are made of corrosion-protected steel, while 84 percent are made of bare steel, which corrodes easily. Another 11 percent of underground storage tanks are made of fiberglass.

Hazardous materials seeping from some of the nation's six million LUSTs can contaminate aquifers, the water-bearing...