Engineers monitored pressure gauges, holding at 600 pounds per square inch for eight hours. Green tanks held the water that was then forced into the 24-inch pipe; the natural gas it normally holds was emptied last week.
"We normally operate this pipeline at less than 400 pounds, so by testing it at 600 pounds, we're getting a significant margin of safety for natural gas operations," said PG&E spokesman Brian Swanson.
The pipe dating from the late 1950s held the elevated pressure, indicating that there are no weak welds or other defects that could lead to a disaster like last year's deadly San Bruno explosion that killed eight people and destroyed 38 homes.
"I think the actual physical testing that's happening right now, is the first thing that's happened since San Bruno that has made me feel like OK, we're turning the corner, safety is actually being tested and improved," said CPUC Executive Director Paul Clanon.
PG&E plans to test or replace 150 miles of pipe similar to the ruptured San Bruno Line 132. The lines are located in densely populated areas from San Bernardino on the south to Sonoma and Solano counties on the north. They'll be done in 95 segments, about 15 a month, hoping to be done by the end of October.
"We're dong several other things this year to validate safe operating pressures. We're doing internal inspections with devices called 'pigs' and cameras, and we're also excavating pipelines, examining welds and testing the strength of the steel," said Swanson.
The testing is not cheap -- between 150,000 and $500,000 a mile.
"The testing that's happening right now, PG&E shareholders are paying for that. PG&E has not requested and the PUC has not granted any rate treatment for this testing. PG&E has the obligation to operate it's systems safely so this is part of doing that," said Clanon.
PG&E told the CPUC last week that over the last decade, there were two failures on 11 tests, so odds are there will be multiple failures on this year's 95 tests.
A pipeline that runs through Antioch will undergo the same water testing next week. On Monday, PG&E vented gas from a line that runs beneath Bridgehead Road and warned residents they may smell gas during the venting process. The pressure test there is scheduled for Monday.