The overhead power line that snapped near Candlestick Park Monday night, triggering the first of two outages that delayed the San Francisco 49ers game, came apart at a site where it had been repaired, Pacific Gas and Electric Company said Wednesday.
But the utility could not say when that repair took place. PG&E said the line had recently been inspected.
On Tuesday, San Francisco Mayor Ed Lee called the outages a "national embarrassment" and ordered the city's fire chief and the head of the San Francisco Public Utilities Commission to investigate the failure.
The 12,000-volt power line snapped at 5:18 p.m. Monday, shortly before the scheduled start of the Niners game against the Pittsburgh Steelers, when a piece of equipment known as a bump sleeve failed, setting off a huge blue flash and cutting power to the stadium.
The bump sleeves that PG&E uses are steel structures about 5 inches long that hold two ends of a power line together. They are often compared to toy finger traps because of the way they grip wires.
The presence of the bump sleeve, which is also called a splice, on the power line indicated to PG&E investigators that it had been repaired at some point, company spokesman Joe Molica said Wednesday.
“Any time you find a splice like that, you’re going to find evidence that that line has been repaired,” Molica said.
Molica said PG&E does not know when the wire was repaired, because regulators do not require the company to keep records when making repairs after storms or other emergencies. Such a requirement “would really hold us up,” Molica said.
After last year's deadly pipeline explosion in San Bruno, which killed eight people, federal investigators assailed PG&E's maintenance and record-keeping practices.
PG&E is investigating whether the bump sleeve was installed in June 2010, when metallic balloons struck the wire, or in September 2010, when a wet bird was electrocuted by the wire, causing a blackout, according to Molica.
Molica said crews thoroughly inspected the wire after each of those incidents and that a PG&E crew performed a less-intensive visual "patrol" of the line earlier this year. "We patrol every year," he said.
Mindy Spatt, a spokeswoman for the consumer advocacy group The Utility Reform Network, said failed overhead wires are a persistent problem for the utility company.
For example, on Sunday, one day before the high-profile blackout at Candlestick Park, 2,900 PG&E customers on the Central Coast lost power after a bump sleeve failed in El Granada.
“If this were an isolated incident, that would be one thing,” Spatt said. “But the fear is that it’s part of a broader pattern of neglect and mismanagement at PG&E.”
It remained unclear Wednesday why the snapped wire caused Candlestick Park to lose power. A second power line is connected to the stadium to prevent such outages, but it did not immediately switch on. Investigators also don't know what caused that backup line to fail during the second quarter, causing another delay in the game.
The California Public Utilities Commission on Wednesday continued its investigation into the outages. Spokeswoman Terrie Prosper said the inquiry may take a few weeks to complete.
"Our inspectors are inspecting equipment, talking to PG&E, talking to the city and reviewing maintenance records to determine if PG&E violated any regulations," Prosper said.