PASADENA — Minutes before an electrical vault exploded, killing three workers underground last July 12, the foreman on the job began to suspect that he and his crew had misidentified an electrical line.
According to a report by a Long Beach forensic engineer released last week by the city, information from a San Rafael-area resident whose electrical power was off perplexed foreman Walter (Glenn) Wise, a 29-year Water and Power Department veteran, prompting him to go back into the vault where two men were working.
The consultant, Douglas Bennett, also found that the workers were hampered by maps that weren't as detailed as they could have been, although he noted that such maps are standard among electrical utilities.
A minute after Wise joined two other workers already in the vault, the lines exploded. Killed were Wise, 50, of Temple City and two cable splicers, Brian Miles, 36, of Pasadena and Larry Hokenson, 38, of West Covina.
In an inspection report ordered by the department, Bennett found that all four workers at the scene mistook a 4,000-volt energized electrical line for part of a de-energized 17,000-volt line they were supposed to repair.
"That's what prompted (Wise) to go down and give it a second look," Bennett said. "He was getting feedback that it was not going exactly as it should be."
The accident has prompted the city to consider changes in the operation of electrical repairs, including providing more details about electrical routings to workers in the field by radio, Bennett said.
Pasadena's circuit maps provide no precise geography of cable routings, Bennett said. Instead, workers such as Wise must piece together electrical routings on scene. Although more detailed engineering maps could be computerized for daily use, the practice is not common, Bennett said.
"I find power utilities to be not really high tech when it comes to things like that," he said. "The only place where it's done is in nuclear power plants."
The city also is considering revising its record-keeping rules on testing for energized circuits before beginning repairs, Water and Power Department Manager David Plumb said.
But some of those changes have been postponed while the city appeals eight Cal/OSHA citations arising from the accident.
The citations faulted Pasadena for, among other things, failing to require workers to use rubber gloves when handling energized lines, to identify and shut off current lines before entering the vault, to ground electrical lines inside the vault, and to test the lines to ensure that they were de-energized before workers entered the vault.
Pasadena officials have retained Bennett to work with the city and Cal/OSHA to help revise the city's operating procedures. The appeal process and final changes to operating procedures could take four months, Plumb said.
According to the scenario put together by Bennett, the July 12 accident began about 8 p.m., when fire broke out in an electrical vault at the intersection of San Rafael Avenue and La Loma Road. A 4,000-volt cable in the vault malfunctioned at a spot where it had been previously spliced.
The fire cut off power to some houses connected to the 4,000-volt line in the exclusive neighborhood south of the Rose Bowl and also burned a parallel 17,000-volt line, which caused more fire and power outages.
When power department trouble-shooter Joe Armstrong arrived about 15 minutes later, the 4,000-volt line did not appear heavily damaged, the report said.
Bennett said that 4,000-volt lines, which are older and are being phased out by Pasadena, can malfunction but that current will continue to run through the line to the point of the malfunction.
Wise arrived about 8:30 p.m., consulted circuit maps and climbed down into two other electrical vaults at the intersection with Armstrong to figure out the electrical routing for the area, Bennett said. Wise erroneously concluded that only the 17,000-volt line was damaged, Bennett said.
Armstrong and Wise mistook the 4,000-volt cable in the burned vault for a feeder line to the damaged 17,000-volt line. The confusion occurred because the 4,000-volt line and the 17,000-volt line consisted of twisted cables of red, blue and black.
The 4,000-volt line, however, had one extra black cable, missed by Wise and Armstrong. Hokenson and Miles also failed to notice the extra black cable, Bennett said, adding that investigators were "perplexed somewhat as to why it wasn't noticed."
In addition, Wise and Armstrong checked three manholes at the intersection but failed to enter a fourth manhole that contained the true connection for the 17,000-volt feeder line.
"It appears, in overly simplistic terms, that the confusion about the identification and all the effects later might have been eliminated had they gone into the other manhole," Bennett said.
As a result of the oversights, the workers thought that no current was running through the 4,000-volt line when they entered the vault about 10 p.m., Bennett said.