Just because we are told that pipelines are "safe," doesn't necessarily guarantee it. Many, if not most, pipeline rupture and explosions are a result of someone with a backhoe or other equipment putting an unreported "nick" in the wrapping of the pipe.
Despite the use of electrical current to prevent corrosion, over a period of years the "nick" becomes a rust spot, then a dimple, then a pit, then a thin spot in the pipe. At mainline gas pipe pressure, the pipe then ruptures. The static electricity generated from the flow of gas ignites it. With the high pressure on a gas mainline, this results in explosion.
Nobody knows for sure where and how many of these "nicks" there are, but they are there. Over time, they will become obvious. Call before you dig!
Mark Rauch, Kennewick