run that exploded last year. at the intersection of glen view and san bruno. john fowler has what we still have to learn. >> reporter: even though the pipeline that is being dug up has not been operated for a half century, there's something new about it, it might hold a clue of a deadly blast and how to prevent them in the future. the commission gave pg & e a double task. >> remove an 8-foot section of pipeline that was decommissioned back in 1956. >> reporter: since that pipe has not been pressurized or depressure sized its welds will be similar to when they were brand new, including any defects. that's good because several pipelines are still working beneath cities,including crowded san francisco. >> we are going to look with a camera, about 250 feet of