Pacific Gas and Electric Co. conducted a retest Thursday of the natural gas pipeline that burst during high pressure testing in northwest Bakersfield Monday. A utility spokeswoman said the test was successful.
PG&E reported that, for the half hour that ended at 11 a.m. Thursday, the pipeline withstood water pressure measuring at least 1,042 pounds per square inch, as required as part of the test.
The segment normally transports natural gas at no more than 757 psi. On Monday morning it ruptured at 998 psi, tearing a 7-foot longitudinal gash through the pipeline and spraying water high over an alfalfa field.
Following the morning part of the test, PG&E planned to keep the mile-long segment at 970 psi for eight hours. The test ended successfully at 7 p.m.
This week's tests were done in response to last year's deadly pipeline disaster in San Bruno. PG&E plans to test some 150 miles of pipeline this year. There were to be 10 separate tests in Kern County, four of which are ongoing or in preparatory stages, company spokeswoman Katie Harlan Allen said.
The Kern segments were selected because the company had no record of previous tests, or because they are located in "high-consequence" areas. Allen said this week's test was done for the latter reason: There is a farm building nearby.
All but one of the tests done this year in Kern County were "spike" tests such as the ones Monday and Thursday, in which pipeline segments are pushed well beyond their normal operating pressure for a short period. The one that was not a spike test took place in Tehachapi in August; a slope along the pipeline made such a test unfeasible.
After Monday's failure, the San Francisco-based utility hired contractors to remove about 80 feet of steel pipeline and replace it with three steel segments. The sections were then welded together with a girth weld, Allen said.
The four pipeline tests still to be completed in Kern County this year are set to take place in Boron near Boron Avenue, near Golden Hills along West Valley Boulevard, and two separate sections in Bakersfield -- one around South Union Avenue, the other near Billie Way, Allen said.
In all, PG&E has 391 miles of transmission pipeline in Kern County. Allen said the company continually tests and monitors these pipelines.