"Safety regulators are increasingly focusing on how seemingly minor problems with a natural-gas pipeline can combine to magnify the risk of an explosion or serious leak, as some experts say was probably the case in a blast that shook a rural Ohio neighborhood last month."
"The regulators, who are preparing to tighten pipeline-safety rules, are considering whether to require companies to change the way they assess risk.
Jeff Gilliam, director of engineering and research at the U.S. Pipeline and Hazardous Materials Safety Administration, told a meeting of regulators and industry officials in August that the current models companies use are "ineffective to analyze the risks" posed in a combination of threats.
Until last year, regulators collected data only on what was deemed to be the primary cause of a pipeline failure. But PHMSA, which other federal regulators have faulted for lax oversight, is stepping up pressure on companies in the wake of several serious explosions, including one near Glouster, Ohio, that destroyed two houses on Nov. 16 and a deadly 2010 explosion in a PG&E Corp. pipeline that leveled a neighborhood in San Bruno, Calif."