SAN BRUNO -- PG&E said Thursday it continues to make progress in a sweeping upgrade of its natural gas pipeline system in the wake of a fatal explosion in San Bruno, although the utility has encountered some cost overruns.

The utility during 2013 replaced 64 miles of natural gas pipelines, up 60 percent from the 40 miles of pipeline it replaced during 2012. The company also automated 75 gas valves, a 63 percent jump from 2012.

"We have hit our targets on our pipeline upgrades," said Debbie Felix, a Pacific Gas & Electric spokeswoman.

The upgrades are part of the Pipeline Safety Enhancement Program, or PSEP, that PG&E has undertaken in the wake of the 2010 natural gas pipeline explosion in San Bruno that killed eight people and destroyed 38 homes.

"The pipeline safety enhancement program is an essential part of PG&E's commitment to rigorous safety standards, improved operations and better service for its customers and the public," the utility said in a recent regulatory filing with the state Public Utilities Commission, which regulates PG&E.

PG&E also said it has undertaken high-pressure water testing, or hydrostatic testing, on a total of 465 miles of pipelines since 2011. Of that total, about 189 miles of pipes were hydro tested in 2013, Felix said.

State Sen. Jerry Hill, whose district includes San Bruno and who is an outspoken critic of PG&E, said the pipeline updates are indications that progress is being made.

"PG&E is improving and going in the right direction," Hill said Thursday. "But because the PUC hasn't transformed itself yet, it is hard to really determine or validate how much safer PG&E is today."

PG&E's update comes as comes as PUC administrative law judges deliberate over the amount and nature of the punishment and fines PG&E must pay as its penalty for causing the San Bruno blast.

San Francisco-based PG&E faces fines of up to $4 billion, but questions have been raised about whether PG&E and its principal regulator have too cozy of a relationship.

PG&E also said that it has encountered some cost overruns in the work it conducted during 2013. But the utility said it wouldn't seek a rate increase to cover the unexpected additional expenditures.

"Our shareholders will cover the higher costs," Felix said. "We have accomplished an extraordinary amount of work, and we are making more progress every day."

The utility has committed to spending $1.4 billion above the $1.17 billion the PUC has authorized for pipeline upgrades and other work to improve the safety of the gas system.

"PG&E is a work in progress," Hill said. "But PG&E is saying the right things and they are spending the money."

Contact George Avalos at 408-859-5167. Follow him at Twitter.com/georgeavalos.