A hidden hazard lurks beneath many of the roughly 156,000 gas stations across the United States.
The hazard is corrosion in parts of underground gas storage tankscorrosion that could result in failures, leaks and contamination of groundwater, a source of drinking water. In recent years, field inspectors in nine states have reported many rapidly corroding gas storage tank components such as sump pumps. These incidents are generally associated with use of gasoline-ethanol blends and the presence of bacteria, Acetobacter aceti, which convert ethanol to acetic acid, a component of vinegar.
Following up on the inspectors' findings, a National Institute of Standards and Technology (NIST) laboratory study* has demonstrated severe corrosionrapidly eating through 1 millimeter of wall thickness per yearon steel alloy samples exposed to ethanol and acetic acid vapors. Based on this finding, NIST researchers suggest gas stations may need to replace submersible pump casings, typically made of steel or cast iron, sooner than expected. Such retrofits could cost an estimated $1,500 to $2,500 each, and there are more than 500,000 underground gas storage tanks around the country.
The NIST study focused only on sump pump components, located directly below access covers at filling stations, just above and connected to underground gas storage tanks. The sump pumps move fuel from underground tanks to the fuel dispensers that pump gas into cars. These underground tanks and pipes also may be made of steel and could be vulnerable, too. "We know there are corrosion issues associated with the inside of some tanks. We're not sure, at this point, if that type of corrosion is caused by the bacteria," NIST co-author Jeffrey Sowards says.
Much of the U.S. fuel infrastructure was designed for unblended gasoline. Ethanol, an alcohol that can be made from corn, is now widely used as a gasoline additive due to its oxygen content and octane rating, or antikno
|Contact: Laura Ost|
National Institute of Standards and Technology (NIST)