The agency found flaws with the U.S. Pipeline and Hazardous Materials Safety Association and CPUC audit of the operation of Line 132 following the explosion. Ruane claims CPUC colluded with PG&E to suppress evidence about the line’s construction and operation.

“Ultimately it’s the engineers who have the ‘duty of care’ to the public and there were many steps along the way for both the utility and the regulator to do something about this and nobody ever did,” Vokes says.

CUPC did not comment.

Bryan Foster, a San Bruno resident who witnessed the blast, filed a research report to the California Dept. of Justice last September that futher alleges the utility was operating the pipeline to supply only one customer—a power plant illegally retrofitted in 2008 with natural gas turbines. The section that exploded was a sole-source, dedicated fuel line, running from San Bruno into San Francisco, to the Mirant Power Plant located in the Hunter's Point District.

The operating pressure of the pipeline was nearly 100 psi over what federal guidelines allowed when it exploded, NTSB said in its report.

In a separate proceeding closely watched by the gas industry, California safety regulators have proposed that PG&E be fined a record $2.25 billion for violating rules on recordkeeping, pipeline classification and the direct causes of the blast.

PG&E has warned that if such a fine is approved, it could hamper its efforts to raise equity to pay for safety improvements. The administrative law judge’s proposed decision in that proceeding has been awaited all year.

“San Bruno was a tragic accident,” the utility said in its statement. “We have worked hard to do the right thing for victims, their families and the community, and we will continue to do so.”

PG&E said it has already committed to spend about $2.7 billion of shareholder money to test and upgrade its system and that it has completed nine of the 12 safety recommendations made by the NTSB, with work on the final three progressing. The utility has also settled claims amounting to nearly $500 million with the victims and families of the San Bruno accident, established a $50 million trust for San Bruno for recovery costs and contributed $70 million to support city and community recovery efforts.

"PG&E thinks they should get credit for progress they've made since the incident, but we think it should have been done over the last fifty years instead of so much money going to shareholders," Ruane says.