Mud from (PG&E) explosion closes lanes on I-280

[Newsjock]

Source: KGO-TV

WOODSIDE, Calif. (KGO) -- Two northbound lanes of Interstate 280 in San Mateo County have been closed due to mud and other debris in the roadway.

Authorities confirmed to ABC7 News the mudslide was caused by an explosion that occurred while PG&E was conducting some sort of test on pipeline in the area.

California Highway Patrol Capt. Mike Maskarich says the vapor that was released from the explosion is not harmful.

Read more: http://abclocal.go.com/kgo/story?section=resources/traffic&id=8421021

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PG&E pipe testing probed in I-280 mudslide
http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2011/11/06/BAMV1LRCQ5.DTL&tsp=1

A failed high-pressure water test of the Pacific Gas & Electric Co. pipeline that exploded and destroyed a San Bruno neighborhood last year trigged a mudslide that has shut down part of northbound Interstate 280 near Woodside.

The rupture is the second failure on that line in four days of testing.

"It was part of a hydro test on the line that was adjacent to part of the line where we had a pinole leak" earlier this week, said PG&E spokesman David Eisenhauer. He said the pipe that failed was believed to be 24 inches in diameter.

... A nearby resident told a CHP officer about hearing a "loud hissing noise going on all night" and reported seeing a "large-diameter pipe spewing mist in the air" at the bottom of an off-ramp on the west side of I-280.

[benld74]

1. A hydro test on 48 inch diameter pipe? Damn, that'd be some high pressure folk

[kentauros]

2. The pressures are probably still going to be no more than

a few hundred psi. Now the amount of energy used to get to that level would be impressive. 48" is usually the upper limit of high-pressure gas pipelines. Most mainline pipelines these days range from 12" up no more than 42" and usually around 30" or 36".

It sounds like the pipeline is old and has become brittle from the hydrogen in the gas. They'd be better off just inserting plastic sleeve linings and forget about saving the pipe as is.

Found a great PDF of PG&Es guidelines for hydro-testing:
Piping Design and Test Requirements

[formercia]

3. That would cost PG&E money

Can't have that.

[kentauros]

4. Then, they'll keep blowing up sections as they pressure-test them.

I'm gonna make an educated guess here (as I'm a pipeline designer/drafter) that it's going to cost them more money in the long run to dig up all the blown-up sections, re-hydro-test, blow-up more sections and so on until the whole line is "tested" (and replaced) than if they just lined it.

Of course, it really doesn't cost them anything per se, because they'll just pass the repair costs on to their customers anyway.

[formercia]

5. I thought they did that already as far as money goes.

They were supposed to fix the line long ago and the money had already been put aside for the work, but it never was done, so the cost had already been passed on to the customers.

[kentauros]

6. I wouldn't know.

I'm not in California. This story was originally in LBN, and why I commented :)