In a similar incident in New Mexico a decade ago, 12 people were killed when microbes in stagnant water inside a gas pipeline released gases that eventually broke down the wall of a 50-year-old, 30-inch gas line, a phenomenon known as microbiologically influenced corrosion, the San Francisco Chronicle reported Friday.
The phenomenon is considered a possible cause of the disaster in San Bruno in which another 5-decade-old, 30-inch gas transmission line ruptured, the newspaper said.
The San Bruno pipeline's owner, Pacific Gas and Electric Co., said in a filing with state regulators last year there was "ongoing concern" about the potential for internal corrosion on the 46-mile line running from San Francisco to Milpitas, which included the portion that eventually ruptured.
This week, the utility acknowledged a "small amount" of water -- the key ingredient necessary for microbiologically influenced corrosion -- had shown up in tests of the line and as many as four others, the Chronicle said.
Pipe-corrosion experts say once present, destructive microbes can lie dormant for years before springing to life and going to work on the metal. All it takes is a pool of water at the bottom of a pipe.
Any pipe as old as the one in San Bruno, installed in 1956, would be likely to have corrosion-causing microbes hiding inside it, Laura Kentala, an environmental microbiologist who has studied the phenomenon, says.
"There is a really high chance," Kentala said. "It is anywhere and everywhere."