http://www.kqed.org/.stream/anon/radio/quest/2011/08/2011-08-29-quest.mp3

On September 9th, when the blast hit, Tammy Zapata was cooking dinner at her house on Earl Avenue, about a block from the explosion. Tammy's husband, Mike, was watching Monday Night Football. Their daughter Amanda was doing her homework on the couch. When Tammy heard the roar, she looked outside her kitchen window.

"No matter how high you looked," she says, "all you saw was fire."

You'll find our series of first-hand accounts, "San Bruno Stories" on the KQED News Blog.

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She says the pressure of the blast was so powerful, it sucked the air out of her living room. They couldn't move.

It felt, she says, "like when you’re in a dream, and you’re trying to run as fast as you can but you’re getting nowhere. Like you’re in quicksand."

A few blocks away, on Claremont Drive, Kevin Ashley had just finished giving his two young children dinner. Like a lot of people, he thought there had been a plane crash.

His first thought was to put the kids into the car. But then he realized the fire was already too close. "I made a split-second decision. I took the kids and I ran, because if not, we were going to be trapped."

A year later, it's still painful for him to talk about.

"I didn’t want my kids to die," he recalls, choking back tears. "I didn’t want them to be burned. And then I decided, it’s not going to happen."

The family has moved to South San Francisco. Ashley's two kids, like many others in the neighborhood, are in therapy. Kevin's wife, Michele, says moving back to San Bruno was out of the question.

"It’s not a home if you don’t feel safe," she says. "And on that night, it almost killed us. So that was the reason we decided to start over."

The pipes beneath our streets

The San Bruno explosion put a spotlight on something most people rarely think about: the vast network of underground pipes that delivers natural gas to millions of homes across the United States.

One of the main transmission lines in the Bay Area, Line 132, ran under the Crestmoor neighborhood of San Bruno. It was installed by Pacific Gas & Electric in 1956, which makes it an old pipe, but not the oldest in the PG&E system.

The part that ruptured was made up of several different sections, including six short pieces called "pups."

According to David Howitt, a chemical engineer at the University of California, Davis, who studies the behavior of metals, the particular pup that ruptured along a welded seam just wasn't made very well.

"The way that pipe was made was you bend it into shape, rather like you’d fold over a piece of paper," he explains. "And then the two edges of the paper, or pipe, have to be stuck together."

When that gap was filled in with welding material, whoever welded it didn’t use enough metal, NTSB investigators found.

"So what you essentially had was a region of the pipe that was much thinner than it should have been. And that’s where it failed."

The investigation

After the explosion, federal and state investigators descended on the area. They found that the section of pipe that blew up had more than 150 welding defects.

Which begs an important question: Where else might similar, shoddy pipes exist? What other sections of pipe were made by this same pipe-maker, or crew?

This information is critical. Because without knowing how strong a pipe is, there's no way of knowing how much pressure it can withstand. Or, how long it might last.

Investigators hoped to find these answers in PG&E's archives. But according to the utility, those records have been lost.

Richard Kuprewicz is an independent pipeline expert in Redmond, Washington, who has studied pipe ruptures for 40 years. He says it's to be expected that a utility might not be able to produce every record for every pipeline. But for a pipeline such as Line 132, one that carries gas at high pressures, record keeping is a form of due diligence.

"It is extremely unusual to not have certain records related to your pipeline, even pipeline that’s 50, 60, or 70 years old," says Kuprewicz.

PG&E says it has made important changes. It has hired a new CEO, and has reorganized its gas division. It has hired dozens of new gas engineers, and agreed to run expensive water pressure tests on up to 152 miles of buried pipelines in the Bay Area this year, to make sure that they're safe.

But many questions remain. For instance, what final straw caused that pipe to finally burst? Was it changes to the gas pressure over the past 50 years? Was it a job the city approved in 2008 to replace a sewer pipe right next to the part of the gas line that exploded? Or something else? And what lessons can we take from it?

"We want the truth."

For San Bruno City Manager Connie Jackson and many others here, tomorrow's report from the NTSB will be momentous.

"First and foremost we want the truth," says Jackson. "What happened? Why did it happen? And more importantly, what will regulators do in order to assure that this never happens again?"

Over the last year, state and federal lawmakers have introduced legislation aiming to reduce the likelihood of another San Bruno explosion. State Assemblymember Jerry Hill's AB 56, which is currently making its way through the state legislature, would strengthen pipeline safety rules and force utilities and regulators to be more accountable. The federal bills, introduced by Congresswoman Jackie Spieier, from San Mateo, and Senator Diane Feinstein, among others, would increase inspections, and notify people who live above gas lines. They also would require that PG&E install automatic shut-off valves, so that fires could be put out much faster.

Here in Crestmoor, the gas line has been decommissioned, for good. The sound of hammers breaks the morning silence.

Bill and Betty Magoolaghan are one of the first families to rebuild here.

Second blog photo san bruno — Bill Magoolaghan.

Like other families, the Magoolaghans received money from PG&E to help pay for temporary housing and other expenses. Now, their insurance is funding much of the reconstruction. Even though their house wasn't completely destroyed, water and fire damage have forced them to rebuild almost down to the foundation. They've added a second story, and changed the layout.

Bill says, especially for his children, the excitement over a new house is what will make it possible to return to this neighborhood.

"If the house was exactly the same, I think it would be a lot more difficult for them to come back in. We had to change the house to make it viable that we could move back in. So that’s what we’ve done."

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About 100 families, including the Magoolaghans, have filed lawsuits against PG&E, alleging that the company could have prevented the explosion. The first batch is expected to reach trial next summer

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