The utility was notified of a leak on Laura Alice Way shortly after 9 a.m. and a repair crew arrived on scene by 9:15 a.m., PG&E spokesman Joe Molica said.
The crew stopped the flow of gas through the damaged 2-inch distribution line at about 11:15 a.m., and as of 11:30 a.m., crews were still working to make final repairs, which require replacement of the damaged segment of the line, Molica said.
Once the line is repaired, it will need to be retested and then slowly repressurized, Molica said. Afterward, crew members will go door to door to conduct gas safety checks before relighting customers' pilot lights, he said.
One nearby business had been evacuated as a precaution.
Molica said the gas line was ruptured accidentally by a third-party contractor. An initial investigation indicated that the line was properly marked, he said.
"These types of accidents just show the absolute importance of utilizing safe digging techniques," he said.
One fire engine had been on standby at the site while crews worked to shut off the gas, according to the Contra Costa County Fire Protection District.
Before the gas leak was stopped, traffic was being diverted at the Solano Way off-ramp from Highway 4 to prevent motorists from traveling east on Arnold Way, CHP Officer Kevin Bartlett said.
The eastbound and westbound off-ramps from the highway to Port Chicago Way had also been closed, he said.
Police Cpl. James Carroll said that those access points were reopened at about 11:15 a.m.