An administrative law judge on Wednesday approved PG&E's plea for more time to produce records detailing welding flaws in its natural gas pipelines, following the company's admission that it had "seriously underestimated" how much work it would take to gather the documents.

The California Public Utilities Commission ordered PG&E to give it the information on all gas-transmission line weld failures or defects since 1955 because the Sept. 9 San Bruno gas line explosion, which claimed eight lives and destroyed 38 homes, had been linked to flawed welds.

But PG&E, which already is facing a $3 million commission fine for failing to provide other records to prove its pipe pressure levels are safe, said it couldn't meet the commission's June 20 deadline.

The company said it could provide "a substantial quantity" of the welding documents for 1,805 miles of urban pipes -- plus "a smaller volume" of records for rural pipes -- by that date. But it said it would need until Sept. 30 to submit records for all its urban gas lines and another 15 months to provide the data for all 5,766 miles of pipes.

In her ruling, judge Amy Yip-Kikugawa agreed to give PG&E the extra time it needs. But during a hearing on the matter earlier this week, she noted that PG&E's inability to quickly produce the records could be used by the commission as a basis to fine the company.

In a regulatory filing responding to PG&E's request for a delay, PUC attorney Robert Cagen had denounced the company's record-keeping as "patently unsafe."

Although pleased with the judge's ruling, "we acknowledge that our record-keeping practices are not where they should be," PG&E spokeswoman Brittany Chord said. "But we are committed to raising our record-keeping practices up to industry leading standards."

Contact Steve Johnson at sjohnson@mercurynews.com or 408-920-5043.