Mystery of Witch Creek fire remains unsolved
Mystery of Witch Creek fire remains unsolved
23 February 2008
published by www.nctimes.com
USA — Four months after the fourth-largest wildfire in California’s history tore a wide path of terror and destruction across North County, authorities are still trying to figure out what started it.
Early on, state fire investigators said a power line had something to do with it. But an official said Friday that they have yet to nail down precisely the role that wires played in the Witch Creek fire.
Meanwhile, an electrical consultant maintains it wasn’t the electric wires that ignited the blaze, but rather the supporting cables that anchor the poles from which they hang.
These cables, guy wires also known as “down-guy wires,” aren’t supposed to be hot. Their purpose is to bolster poles so that they will stand up in strong wind.
Consultant Ed Clark said in a recent interview that his own investigation found that the guy wires on the ranch where the fire broke out were carrying electrical current and arcing at the time.
Clark said he uncovered evidence that shows arcing from the cables ignited tinder-dry grass nearby as ferocious, hurricanelike Santa Ana winds swept across the region.
Clark’s theory caused the California Public Utilities Commission recently to open an investigation.
The state regulatory agency is trying to determine if the potential for guy wire arcing poses a significant fire threat and, if so, whether the construction of guy wires should be more tightly regulated.
“We are looking into whether there are arcing issues with down-guy wires and, if so, (we will) determine the cause and take appropriate action,” said Susan Carothers, a spokeswoman for the Public Utilities Commission in San Francisco, by e-mail.
However, Jim Garrett, fire prevention chief for the California Department of Forestry and Fire Protection in San Diego, said Friday that, while investigators have not finished their investigation, they have ruled out the possibility that guy wires started the fire.
The CalFire investigation
The Witch Creek fire tore a wide swath through North County, stretching from the oak-covered backcountry almost to the ocean.
Fanned by gusts of up to 70 mph, the blaze grew to 198,000 acres and destroyed 1,075 homes in Escondido, Poway and Rancho Bernardo. Two people were killed in Poway.
From the beginning, the 69-kilovolt power line that runs across the ranch between Ramona and Santa Ysabel where the fire started —- near Witch Creek Road —- was suspected as the cause.
And in November, the state firefighting agency, known as CalFire, announced it had reached a preliminary conclusion that wires were involved somehow.
Exactly how is the question that CalFire is attempting to answer in an ongoing investigation. Investigators said earlier that they had expected to find the answer by March 1. But Garrett said Friday it is unclear when the investigation will be completed and a report issued.
Investigators also are still looking into the cause of the Rice fire that scorched 9,472 acres in the Fallbrook area, including nearly 1,000 acres of avocado and citrus groves. That blaze destroyed 240 homes.
As with the Witch Creek fire, CalFire concluded in November that a power line had something to do with it.
But Garrett said CalFire has wrapped up work on the Poomacha fire that destroyed 138 homes, injured 15 firefighters and burned 90 percent of the La Jolla Indian Reservation. He said the 49,400-acre blaze was kindled by a house fire on the reservation that spread to surrounding vegetation, and investigators have been unable to determine what ignited the house.
The guy wire theory
While Garrett declined to say what the Witch Creek investigation was looking at, there are several possibilities involving the electric wires themselves. They tend to slap against each other or against tree limbs in high wind, sending showers of sparks into nearby brush and grass. And they are known to blow down in heavy gusts.
Still, Clark maintains investigators are looking in the wrong place.
Clark, a Huntington Beach man who worked for Southern California Edison as a transmission substation engineer from 1980 to 1990 before going into business for himself, noted that high winds are particularly dangerous when arcing is occurring.
Arcing occurs when there is a short break in a connection between cables or wires that conduct electricity. The current flows through the air between the wires, creating a continuous glow of electricity. That’s different from a spark, which is momentary.
Clark said the evidence he found —- black spots on yellow plastic covers for guy wires and on the ground next to guy wire anchors —- show that the cables on the Ramona-area ranch were energized at the time, and were arcing. He said the arcing was the result of a gap between a guy wire and its anchor.
Clark said those supporting cables were in the area where the Witch Creek fire started.
Despite what he found, the bottom line, said Stephanie Donovan, a spokeswoman for San Diego Gas & Electric Co., the keeper of most county wires, is that Clark has made an unsubstantiated claim.
“There has been no proven link between guy wires and the October wildfires,” Donovan said.
Metal to metal
Clark said he found similar evidence that suggests an arcing guy wire was responsible for the 2003 Paradise fire that also ravaged North County. CalFire determined the cause of that fire a few years ago to be arson.
While guy wires aren’t designed to carry electricity, but rather to brace poles, Clark said they can become energized.
Occasionally, electric current flows through the ground. And if the supporting cables aren’t properly installed, he said, it will run up one guy wire, on one side of a pole, and down the cable on the other side to the ground.
Whether arcing will occur at those times depends in large part on how tightly guy wires are tied to anchors, Clark said.
“If it’s metal to metal, you have great contact and there is no arcing,” he said.
But that’s not what Clark said he found on the Ramona-area ranch. There, he said, connections were loose, leaving space for electric current to travel through the air. And he said there was dry grass next to the anchors.
Even so, the flow of electricity through the cables —- and any arcing —- could have been prevented had SDG&E properly separated the two supporting cables, Clark said. He said that, because the cables were tied into the pole at the same height, on opposite sides, current was able to flow from one guy wire to the other, creating the potential for arcing.
Clark maintained that SDG&E’s installation violates state rules, which he contended requires a cable on one side of a pole to be 12 inches above or below the bolted-on guy wire on the other side. His Web site displays a photo of the construction.
Carothers, of the Public Utilities Commission, said Clark has it wrong. She said only 3 inches of separation is required, and it doesn’t have to be vertical; it can be horizontal. And with the pole being much larger than 3 inches in diameter, it provides adequate spacing, she said.
“The down-guy wires in the pictures Mr. Clark showed us had much more clearance than 3 inches, and therefore could not be considered a technical violation of the 3-inch standard,” Carothers said. “Mr. Clark was simply applying the wrong standard to this situation.”
Donovan, of SDG&E, said the parallel design has been used by the utility for the last 25 years
