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Pipe material in Cupertino blast has history of failure

September 5, 2011 6:30:08 PM PDT
The California Public Utilities Commission has launched an investigation into a natural gas explosion at a townhouse complex in Cupertino last week. The type of plastic used to make the pipes involved in that blast has a history of failure.

Experts tell ABC7 all gas pipelines have the potential to leak, but the National Transportation Safety Board recommended stepped-up inspections back in 1998 after a series of explosions.

The plastic pipe that cracked and set off the explosion and fire is known as Aldyl-A, made from polyethylene material by DuPont in the 70s, 80s and early 90s. It doesn't corrode the way metal pipes do, and chemists say it had a life expectancy of 150 years.

However, PG&E says it will now replace all 6,000 feet of Aldyl-A pipe feeding gas to the 400 units at Northwest Square.

"If they've figured out that that's a material that's not very good, I would think with the better material they should be taking those safety precautions and make sure things like that don't happen," said neighbor Abhay Sachar.

The 40-year-old Aldyl-A pipe will be replaced with a new generation of plastic -- a project PG&E says will take several months. In the meantime, it will perform weekly safety checks for gas leaks.

A former DuPont chemist, now an independent pipeline consultant, Dr. Gene Palermo, has studied the projected life of Aldyl-A pipes. The plastic pipe can be compromised by what he calls rock impingements, where the pipe presses against rocks in the soil.

"It's possible for the crack to initiate and to propagate through the wall of the pipe, in say five years," said Palermo. "In other cases, I have seen slip-crack failures that have occurred after 40 years."

Residents near last week's explosion and fire are leery of PG&E's safety record. They say they're uneasy now.

"PG&E has moved another degree of uncertainty for us. I feel very, very concerned," said customer Poonam Bhargava. "There should be some kind of inspection done in the whole area in our neighborhood."

PG&E says it has just over 1,200 miles of old Aldyl-A pipeline in its distribution system. The state PUC is investigating and the NTSB will be watching closely.


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