Last week's massive power outage in Los Angeles could have been prevented if workers had double-checked faulty designs and whether lines were electrified, the Department of Water and Power said Thursday in a report recommending sweeping changes.
The 24-page evaluation of the Sept. 12 incident provides the most detailed account yet of an accident that cut power to 2 million people in Los Angeles, Glendale and Burbank.
In releasing the report, DWP General Manager Ron Deaton apologized to residents for any inconvenience caused by the 1 1/2 -hour outage.
"It was an unfortunate event," Deaton said in a letter to the mayor in which he praised city employees for restoring power quickly. "It also gives us a humbling insight into the procedures that must be improved and helps us better prepare for a major disaster."
Mayor Antonio Villaraigosa said he was "deeply concerned" by the findings and said the analysis does not go far enough. He ordered a more detailed study to be done in the next 30 days to find ways to limit the scope of future power outages and reduce public health problems caused when oil refineries lost power and burned off excess fuel.
"The preliminary conclusions about the cause of the outage are troubling because they confirm that the outage was the result of multiple errors and a lack of communication," the mayor wrote to Deaton after the release of the report.
The outage occurred when a worker installing a new automated control system at the Toluca Lake receiving station cut a bundle of three wires that were electrified, triggering a short circuit that led to the shutdown of other transmission and generation stations to avoid damage.
All similar work has been suspended until a more detailed evaluation is completed, Deaton said.
The incident affected 897,922 homes and businesses, more than half of the DWP's customers, the report said.
The report concluded that several people were in positions to prevent the incident, but does not identify them. A private engineering contractor that drafted the initial design for the automated control system did not account for the replacement of an old breaker relay "since it was outside their requested scope," and DWP design engineers indicated they would design the replacement for the old relay but had not gotten to it in time, the report said.
A test engineer discovered the omission and tried to fix the problem, but a print with errors was given to the work crew, which cut the wires without testing them to see if they were electrified.
