State regulators in 2007 gave Pacific Gas and Electric Co. the go-ahead to spend $5 million of ratepayer money to replace a 62-year-old section of the same pipeline that exploded last week in San Bruno. But the work never got done as scheduled in 2009, and this year the utility asked for another $5 million to do the same job by 2013, according to documents submitted by PG&E to the California Public Utility Commission as part of a general rate-hike request. While the cause of the pipeline explosion has yet to be determined, experts say that in general older lines...