The National Transportation Safety Board is wrapping up its three days of hearings examining the pipeline rupture and explosion in San Bruno. Today's focus is on technology - both remote shut off valves, but also on ways to detect problems in underground pipes. The bad news is that no technology is perfect. And it could be very expensive.
Basically, there are basically three ways to check natural gas pipes for leaks, corrosion, and cracks. You can dig up the pipe. You can flush water through the system, called hydrostatic testing. Or you can send a device - called a "pig" through the pipe to take a look. There are problems with all three tests.
Realistically, you can't dig up every pipe in America. So companies are using the other two technologies to decide which part of a pipeline to dig up.
Hydrostatic testing will help you find the weakest link in a pipeline, but it won't tell you about other smaller defects, or what are called the “threats lurking around the corner.” Also, if you're flushing water through a pipe, you have to turn off the gas to customers. And any bits of water leftover can create corrosion later. Or if you live in a cold climate, it can freeze and burst the pipe.
The "pig" solution only works if your pipeline is "pigable" - in other words, doesn't have Y connections or twists and turns that the device can't maneuver. According to an American Gas Association survey, 61 percent of the nation's pipelines are not pigable. The group estimates it would cost 12 billion dollars to make all the pipes pigable.